The famous stellar cluster+nebula M-45, "The Pleiades": a photograph from the year 2000 by Herm Perez, using a Vixen R200SS 8" f4 Newtonian, stacking two 30-minute and one 15-minute exposure made on E200 film; used by permission; resized & rebalanced by Waldee to bring up dusty reflection nebulosity and NGC-1435. Original full-sized image found here.

Viewing Techniques For Studying M45 - "The Pleiades" - An Article by Steve Waldee

INTRODUCTION

Known since antiquity, the "Pleiades" cluster has introduced many observers to the pleasures of astronomy. The late American comet-hunter Leslie Peltier, a farmer by profession, poetically recalled his childhood fascination with the comforting winter apparition of M-45, then almost universally known. In a modern age when genuine experience with astronomical objects is limited to specialists, so great is the mythical celebrity of this grouping that some scientifically-illiterate flying saucer buffs have targeted M-45 as the homebase of alien creatures who abduct humans to satisfy their insatiable Pleiadean curiosity!

John Sanford's guide, "OBSERVING THE CONSTELLATIONS", summarizes important aspects of this famous asterism:

"The Pleiades, or Seven Sisters (M45), is a nearby young galactic cluster, the stars of which are imbedded in nebulosity shining by light reflected from microscopic solid particles... the [blue] color deriving from the very hot stars...Seeing the members individually is a test for acuity in eyesight, as they are close together and vary in magnitude from Alcyone's 2.86 to Pleione's 5.09. William Rutter Dawes, keen-eyed double star observer of the mid-1800s, saw 13 stars here without optical aid. Burnham remarks that there are at least 20 stars in the vicinity which could be glimpsed..." (quoted by permission of Sanford in the Waldee- Wood computer program EYEPIECE 2.0.)

OBJECT DIMENSIONS AND CHARACTERISTICS

The generally accepted celestial angular diameter of this brilliantly-radiant star cluster, as given on the SEDS page for M45 and by many other references, is 110 minutes, or just under 2 degrees of arc. The SEDS article cited recounts the human history of this remarkable object, known since antiquity and important to ancient, superstitious observers. The cluster is found in the constellation of Taurus, and pertinent astronomical data about it, plus the capability of generating your own customized finder chart, is found on Mikkel Steine's "Deep Sky Browser" page for M-45 (appropriately found on the domain www.Messier45.com.) There, we learn that the visual magnitude is a crisply-bright 1.31 (thus making it one of the most easily seen deep sky objects) and learn some of the multitudes of professional catalogue reference equivalent descriptions: Collinder 42, Melotte 22, OCL 421, Lund 117, and C 0344+239. Indeed, Mikkel's M45 page, with its default setting of 10 arcminutes for a downloaded Deep Sky Survey image, displays only a tiny central region (showing a bit of the reflection nebula Van den Bergh 23 around the star Alcyone) unless one takes the trouble to create a mosaic of 30-arcminute diameter scans.

Many different celestial objects are associated with M-45, as shown below in a 'screen dump' kindly supplied by a friend, using the GUIDE program. Numerous variable stars are indicated, along with nebulae identified with some of the brightest stars in the cluster (notably the larger Merope nebula NGC 1435; the smaller nebula around Merope, IC-349 -- discussed here -- discovered by Edward Barnard; Cederblad 19e, -p, -o, -h; IC-1990; VdB 20, 23; NGC-1432; and the overall nebulosity designation, LBN 770.) An alternative chart is found in the very good article on the Pleiades by Jack Kramer, here on the Lake County Astronomers association website.

19th CENTURY PLEIADES DISCOVERIES

The large nebula associated with Merope was discovered by the German comet-hunter Wilhelm Tempel in 1859 (the online biography cited contains a copy of the original published notice, shown as an illustration rendered in a typical 19th-century woodcut.) Many doubted Tempel's observation, but finally it was confirmed: the the first photograph of the nebulosity was done by the French astrophotography pioneers, brothers Paul and Prosper Henry, in 1885. The exposure was achieved by means of a telescopic camera with 13 inch aperture, operating at f/10, which is distinctly "slow" for recording extended nebulosity. In 1989, I found in the archives of Lick Observatory the original French- language paper by the Henry brothers in the annals of the Paris Observatory, and my friend Rich Page helped me translate it into English (during the research I did on the early photography of the Horsehead nebula.) A very brief notice, in French, was published in the Astronomisches Nachrichten (volume 113, 1886): it may be seen here, sadly without the picture. An accurate direct reproduction of the photograph itself was not published, but rendered instead -- due to the limits of the printing methods available at the time -- as an engraving, showing very little of the nebulosity indeed: just enough to confirm the earlier sightings by Tempel, but not much glow, compared to later pictures made with faster optics, more sensitive plates, and after the introduction of hypersensitizing techniques.

Indeed, as cited in my very lengthy paper on the 19th-century study of the Horsehead, Dr. Max Wolf seemed unimpressed with the results achieved by the Henrys. He wrote, "A year ago I photographed the Pleiades with a 2-1/2 inches aplanatic lens by Steinheil, and I was surprised to obtain, with an exposure of one hour, all the nebulae which the MM. Henry obtained only with an exposure of several hours, using a large telescope of 13 inches aperture." Wolf realized that he had to use a faster optical system than f/10 to register faint nebulosity; the Henrys clearly did not appreciate this, and the failure of the famous Cartes du Ciel photographic atlas project of the late 19th century to record anything but stars confirms that German and American astrophotographers were quicker to grasp the crucial impact of focal ratio on the exposure depth of extended nebulosity.

The next photograph to attain celebrity was the astoundingly improved one by Dr. Isaac Roberts, taken with a vastly superior instrument, particularly suited to photography: the f/5 Grubb 20-inch Newtonian reflector at Roberts' "Starfield" Observatory in Sussex. This telescope, according to its owner, was able to hold a precise point of starlight on a photographic plate for several minutes, without the slightest need for any hand-guiding adjustments. By this means, the picture below -- done on 8 December 1888 -- was able to record vastly more of the faint reflection nebulosity due to the "fast" focal ratio of the telescope.

Even the rudimentary rotogravure printing process used in this old 19th century astronomy book, from which I copied the photo, fails to obscure the beauty and detail: imagine how much better the authentic original plate must be! Compare this old 1888 picture with one of the finest modern ones done by conventional color astrophotography, by Dr. David Malin (seen here), or this fabulous CCD image by Chuck Vaughn. While modern pictures show much more, and in brilliant color, it must be said that before even the end of the 19th century, astronomy buffs now could understand almost as much about the star cluster's 'true' appearance as we can today, 12 decades later.

Better yet, get out and LOOK at the Pleiades, even if merely with your own two unaided eyes! (Remember, Taurus is primarily a winter constellation for northern hemisphere observers, so the object won't be favorably situated in the night sky throughout every season. If you are willing to stay up late, you may observe the Pleiades from the northern hemisphere during late summer; it is most conveniently seen in evening during fall and winter; by springtime it sets a few hours past dusk.)

OBSERVING THE M-45 STAR CLUSTER BY AMATEURS

The Pleiades cluster has often been a favorite object of this observer, as it can be seen to advantage not only by naked eye, but also with virtually any rudimentary optical aid. In fact, a typical amateur telescope is not the most appropriate instrument for viewing the Pleiades. Due to its enormous angular dimension, and the incredibly bright magnitude of the main stars in this cluster, most telescopes have too narrow a field of view, and blind the observer with the brilliance of the major sparklers in the cluster.

The ancient name for this group -- The Seven Sisters -- was not a particularly accurate description, for almost twice this number of stars may be glimpsed by keen naked-eye observers in a dark sky. Percival Lowell (of Martian 'canal' fame) claimed he could see 18; young Ryan Wood, son of EYEPIECE co-author Ron Wood, counted 16 when he was a mere 14 years of age; on the same occasion, your author (then thrice his age) saw a scant 8 stars! Now, eighteen years later, I'm lucky to be able to see 6 or 7 without optical aid.

I mentioned this in a discussion thread on sci.astro.amateur about observing the naked-eye stars of the cluster, and also noted that:

My friend Shiloh Unruh, a former staff member at Lick Observatory, was observing with my wife and myself in late September of 1989. He claimed to be able to see 12, and -- to prove it -- he clearly saw the Pleiades as it rose in the eastern horizon LONG before I could detect the cluster with my naked eye.

There were some very thoughtful responses in that series, especially those of Mel Bartels and Jay Reynolds Freeman, who added:

I hope people noticed that Mel Bartels's recent posting provided the obvious answer ("Thoughts on Counting Pleiades", found here) which is to work with a specific sequence of stars, so that one can say "I could see x and y, but not z".

Another point: To observe casually with the naked eye is to expose the eye to light pollution from the entire visual field. Sites differ dramatically on how bad that is -- in the mountains or desert it may be quite dark in all directions, but many pretty good sites have lots of skyglow near the horizon, or cities and towns visible in the distance. And just skyglow and starlight are often noticeable.

To eliminate much of this source of error, it might help to observe through a simple "1x binocular", made by taping together two paper tubes -- perhaps toilet-paper tubes -- with a spacer in between, and coloring the insides black. I expect that at most sites, observers would see more Pleiades with such a device than without one -- at least, observers who did not wear glasses. A fancier gadget -- something like a welder's hood with a wide tube attached where the dark glass goes -- might do for glasses-wearers.

Last comment: I myself have never been much into naked-eye magnitude limits, because I do wear glasses for distant vision, and my prescription is rarely as "on" as I would like it to be. -- Jay Reynolds Freeman

Here are some interesting drawings made by Jaakko Saloranta, based on his very careful naked-eye studies, as well as by using a night-vision light intensifier, showing the stars of M45 that can be seen by a perceptive observer.

OBSERVING THE PLEIADES' NEBULOSITY

The renowned nebulosity of the Pleiades may be spotted on nights of exceptional atmospheric clarity by using high-resolution optics. However, some novice (and even skilled) observers who look at the Pleiades with a telescope or binoculars are SURE they are seeing the famed nebulosity -- as depicted in David Malin's fabulous photographs -- because of the internal reflections and light- scattering of their optical instruments!

The author studied the Pleiades carefully for several winter seasons, in the late 1980s, in order to confirm a visual sighting of the nebulosity. Starting with a lowly Astroscan telescope, up to a fabulous Astro-Physics Star-Fire apochromatic refractor, the writer has not been able to sincerely state that the nebulosity is viewed by eye as it is depicted in a photograph: occasions where it shows up distinctly, with fine "brush stroke" markings, are few and far between, even in climes and high elevations offering the most superb telescopic seeing.

LPR Filter Color Response, Cutting Out Yellow Streetlight Interference

The patches of nebulosity around the stars Merope, Alcyone, and some of the other bright stars in the cluster glow by reflection of the photons emitted from these bright stars that are scattered off the regional dust clouds. A light-pollution-reduction (LPR) filter that reduces only the wavelengths of manmade streetlights might sometimes be necessary to view this nebulosity: do not use a hydrogen or oxygen-line filter, or you will cut off the pale bluish light that is so easily recorded on photographic film. (More on the various nebular filter types, and suitabilities, may be found in this article that I wrote in 1997, with major updates, and additional illustrations, added in 2007.)

Do not be misled by reflections, flaring, and light scattering around the bright stars in average-quality or even very good telescopes. In the author's 8" f/5.2 richest-field reflector (with a superb primary mirror) there is sufficient light-scatter to cause a general glow around all the bright stars of this cluster. Moving the scope to -- say -- the nearby belt stars of Orion will soon confirm that any star of the same magnitude as the bright ones in the Pleiades may cast a general glare in the field of view.

I made several crackpot experiments recently -- [1996] -- to try to determine a new way of discerning the nebulosity in M-45. Since the light of the cluster members is so bright, an 8" or larger scope presents a blinding image to the eye; yet stopping down to a smaller aperture would reduce the resolution that MIGHT yield a glimpse of the fine sheen that Malin's photograph documents.

I first tried using a variable-polarizing filter intended for lunar observing in order to reduce the brightness without limiting angular resolution. But, swinging the scope over to other bright stars, I confirmed that this filter had internal reflections that cast a bright glow around a star like Sirius or Alnilam.

So I tried a neutral-density moon filter that reduces the light transmission to about 13% of normal at ALL visual wavelengths. By then adding the broadband light-pollution- reduction filter, I began to detect distinct traces of the nebulosity, particularly around Merope (Tempel's famous 'comet'), Alcyone, and Electra. Of course, it is necessary to observe on a night with exceptionally steady seeing, which is difficult to achieve in winter weather conditions.

Even if one is not intent on detecting the elusive nebulosity, M-45 is a wonderful sight even in binoculars or a small beginners' telescope. Yet the typical Christmas-present toystore refractor will not provide the wide field of view necessary for appreciating the entire group. Binoculars, a richest-field scope, or even a good finderscope will give the proper perspective to this beautiful aggregation.

M-45 is so bright that it is possible to obtain a sufficiently wide field by using an ocular that produces an exit pupil of 10 to 12 mm, reducing the apparent scope aperture and light gathering but permitting the full two degrees of the cluster to be accommodated. Of course, users of reflector scopes will have to "dodge" the dark spot in the center of the field that appears when employing an exit pupil larger than the pupil of the viewer's eye. If you are not sure how to calculate the exit pupil of eyepieces used in your scope, download our EYEPIECE computer program, and test it to see what ocular best suits your needs for viewing all of the extent of the full cluster.

Jaakko Saloranta cites an interesting visual observation, yielding an excellent drawing, made by Risto Heikkilä in Finland, using an 14.5" f/5 Newtonian (in a sky with naked-eye stellar magnitude limit of 5.9, and an eyepiece field of view of 35 arcminutes at 136x.) I have to admit that I have never come close to having a clear, precise perception of all those details of the various nebulae!

Jaakko's friend Toni Veikkolainen drew his observation, made by means of an 8" f/5 Newtonian. Toni opined:

Who claims that the Pleiades is a piece of cake? That's true when its [reflection] nebulae are ignored. NGC 1435, the brightest, was situated west of Merope, 23 Tauri. The equally difficult vDB 20 surrounding Electra, 17 Tauri, had a short tail reaching southwest. The hardest one, vDB 21, was a round patch around Maia, 20 Tauri. All nebulae were seen merely through the [Baader O-III] filter and the faintest one demanded averted vision.

Unfortunately, in the original post to the Deep Sky Archive, Toni mis-identified these objects as being emission nebulae, which they are not. I replied to Jaako:

I doubt very much that the filters for the hydrogen beta or triply ionized oxygen lines are really working AS INTENDED for those objects. It could be that they are knocking down the other wavelengths that are bright and mask the objects named above. I might try this myself. But the visibility of the stuff in the cluster is so variable that it might be hard to come up with conditions that match.

(However, it must be noted that the Baader O-III filter seems to have a slightly different response characteristic than -- say -- the familiar Lumicon model, or the newer one made by Orion: see this webpage for a graphic. I wouldn't discount this claim until I've tried it myself, with EXACTLY this model and brand of filter.)

Jaakko too gave his opinion about the visibility of the nebulosity in an email to me, stating (emphasis applied by me):

I think people take the glow from the bright stars as the nebulosity far too easily. With small telescopes I'd claim it easier than with larger ones: The brightest stars start to interfere badly with larger apertures and need to be placed outside the field. Risto Heikkilä also told me once that O-III helps, I've never been able to confirm it so I'm still a bit skeptical until proven otherwise.

I remember this one time at DS-meeting, 2002 or something when I was looking at M45 and the nebulae in particular. The owner of the telescope came to me and asked what I was looking at. I explained about the nebulae and he asked if he could have a look. His telescope and all that so I didn't have any objections. He looked down the eyepiece for about 5 seconds, lifted his head up and said "Yeah, I can see those, easy". I said nothing and he moved on. I had tried to see the nebulae for an half hour with a full night vision. This guy comes from inside the house and claims to see it, what's with that? I looked down the eyepiece and it was covered in moist, "nebulosity" indeed.

Another time I tried it with the 25" Obsession. I felt like the brightest stars burned thru my brain - they were so bright - and no nebulosity was visible but the glow around stars was very evident. I asked this one guy to have a look and he said "Yes, I can see nebulosity around the stars, all of the brightest ones". I've seen and had too many failed observations on this one so I agree with you; they're very faint and the observer needs to know what is true and what is not.

   -- Jaakko Saloranta

STEVE AND JAY DUKE IT OUT ON USENET

My original little 1996 article, posted to usenet as an attempt to help beginning astronomers, seemed -- as usual -- to provoke a lot of heat from the "elite" experts. No two of them agree on many particulars, especially with respect to subjective issues: and this is normal, illustrative of the "personal equation" of astronomers, and our many unique differences (which I discuss in a related article about some of the psychologies of observing and cognition.)

One of the main objectors was the distinguished northern California amateur astronomer Jay Reynolds Freeman, a man of whom I personally have many fond memories, from mutual activities in local astronomy clubs in the 1980s and 90s: a great expert, and an incredibly experienced observer (see this article for some verification of that!) Jay's major complaint -- aside from taking exception to my calling him an excellent observer with "remarkable gifts", which he coyly denied -- was that my "long and discouraging commentary" failed to state categorically that "the Merope Nebula is easy"; that in fact, in his experience, it:

"...looks like a long, broad streamer trailing out away from the star, away from the center of the Pleiades. All of the effects which one might confuse with a nebula are symmetric about the stars, thus the difference is very obvious. What's more, the Merope Nebula is sufficiently bright that I have seen it with (I think) every size of binocular and telescope with which I observed the Pleiades; that's from 7x50 on up.

Yet, I found other posts by Jay, from around the same general time period, in which he presents slightly contradictory opinions: some in fact, I would assert, tending to corroborate MINE:

M45 -- The Merope Nebula is not hard in decent sky, but it is always tough to decide whether any other fuzz I see is dew on the optics, or scattering in the air or eye, or really nebula.

    -- JRF, found here, from Jan 15, 1997.

...The trouble is, they [M-45's bright stars] always all show some adjacent glow, for one of the reasons I cited or another, even on a clear, dry night. One needs a differential measurement of how much is present, or a pattern of glow that is non-symmetric about the star(s) in question...

    -- JRF, found here, from Jan 15, 1997.

Before the Pleiades set I swung the telescope there and was able to show several observers the faint, broad streak of the Merope nebula, at 40 diameters again. More than one person remarked unprompted that there appeared to be nebulosity around several other Pleiades stars in the field, and we all bewailed the difficulty of making sure that circularly symmetric glow about a star is really nebulosity and not dew or halation within the eye.

    -- JRF, found here, from April 2, 1995.

...I have seen the Merope nebula many times before, but this was the first occasion on which I have been willing to call it bright and obvious.

    -- JRF, found here, from Nov. 11, 1996.

An observer near me was looking at the Pleiades at low magnification -- 36x in a Celestron 8, and 15x in a Ranger. I overheard him tell a companion that the Pleiades did contain nebulosity, but that he had never seen it -- all the stuff in the field that looked like nebulosity was a mere consequence of dirty optics. At that point, I asked for a look. It is indeed possible to confuse scattering from dirty optics or dew (not a problem on these nights) for nebulosity near bright stars... When I pointed out what he was seeing, he remarked that he simply hadn't known what to expect.

    -- JRF, found here, from Aug. 24, 1998.

Light pollution, or less than very transparent sky, interferes considerably with seeing the Pleiades nebulosity.

    -- JRF, found here, from Feb. 10, 1998.

The Pleiades -- Dazzling open cluster, with subtle nebulosity.

    -- JRF, found here, from Mar. 28, 1997.

The clusters M34, M35, M36, M37 and M38 were all easily resolved, as were the Pleiades. I saw no hint of nebulosity in the latter.

    -- JRF, found here, from Nov. 25, 1997.

I know someone will object to "taking things out of context", but here we have an interesting quandary, since Jay has found that under some circumstances of viewing the Pleiades he could see "no hint of nebulosity"; that the Pleiades nebulosity is "subtle"; that while it is "not hard in decent sky, but it is always tough to decide whether any other fuzz I see is dew on the optics, or scattering in the air or eye"; that the bright stars of the cluster "always all show some adjacent glow...even on a clear, dry night"; that he had "bewailed the difficulty of making sure that circularly symmetric glow about a star [of the Pleiades] is really nebulosity and not dew or halation within the eye"; and that "Light pollution, or less than very transparent sky, interferes considerably with seeing the Pleiades nebulosity."

Finally, though Jay asserts repeatedly that "the Merope Nebula is easy", in another post done on November 25, 1996 in response to my article, he explains that he has recorded "31 observations of the Merope Nebula"; and only two weeks earlier before I had written my article, he states that "I have seen the Merope nebula many times before, but this was the first occasion on which I have been willing to call it bright and obvious." The conclusion one may draw, from Jay's many comments on the nebula, is that while it is "easy", only once in his 31 observations was it "bright and obvious"; and often the nebulosity may be confused with "dew or halation within the eye." These statements -- while being somewhat more specific about Merope than I had been -- seem to me to be very much like what I was trying to convey in my own way, in MY article (allegedly "discouraging", per Jay.)

Yet, another respondent in the discussion thread seemed not to agree with Jay's assessment that the nebula was so "easy": Kenneth Drake wrote that:

I think seeing the Pleiades nebulosity is no more difficult than seeing the gegenschein which I saw for sure from the Ultimate Star Party last month with the help of Barbara Wilson.

For those that don't know, the gegenschein can be seen as a 10-15 degree patch of very faint light at a point on the ecliptic 180 degrees from the location of the sun. It is caused by light reflecting back off the small dust particles in the zodiacal band. -- Kenneth Drake

My own private reaction was one of absolute astonishment, for I have never seen a trace of the gegenschein, though the zodiacal light has been obvious to me on some nights at my viewing locale in the mountains north of Santa Cruz, not far from 'civilization'. If the Pleiades' nebulosity is as elusive as the gegenschein, I'd never have seen it -- EVER -- in all these years of observing. Drake is a highly- experienced advanced observer and "regular" at the Texas Star Party, having made many informative posts to the group, back in the 1990s. He observed in very dark and transparent skies, superior to the venues used regularly by both Jay Freeman and me. Yet, the Pleiades nebulosity, to Ken Drake, is like the gegenschein. How does one reconcile that expert, informed opinion with Jay's assertion that Merope is so "easy"?

Perhaps, gentle reader, you are beginning to see the points I'm trying to make: first, judgments about what is "easy" -- or not so -- are subjective and will not be universally held by all observers; and second, even the most skilled and experienced observers often disagree about many specific, narrow issues that relate to their own perceptions: and they should not continually fall into the trap of what I've called "denying the experiences of others". In line with this, I think it's fair to observe that to Jay, critical and experienced observer of more than thirty viewings of the Merope nebula, the object is "easy"; to Steve and Jaakko it's "not easy". This is within the normal range of expectations of a population of persons interested in this phenomenon; there is no need to go further and assert a fixed, objective, and unyielding 'quality' to the nebula, as viewed visually through a telescope; and especially no need to cast doubt on the intelligence, skill, and perceptibility of persons who have differing individual experiences, assuming that they have made no obvious blunder.

I felt that I had to reply to Jay and other critics, so I posted these comments:

The issue has been the relative visibility of the nebulosity in the Pleiades, as provoked by my (surprisingly controversial!) article.

Jay adds that success is not so much to be attained by the use of great instruments, but in acquiring the personal skills to perceive and understand what falls on the eye...the 'brain' part of the eye-brain system may not be fully aware of the actual physiological signals from the retina, until we learn to interpret the signals.

When I was researching early nebular photography at the UC/Lick science collection and archives in Santa Cruz, and even at the plate vault on Mt. Hamilton (in conjunction to my wife's and my volunteer work with the Visitor's Program at Lick Observatory) I came upon the Pleiades nebular confirmation by the Henrys, as recounted earlier. I found the long-forgotten paper, still untranslated, in, I believe, 1986 or 87.

In following the trail back to Wilhelm Tempel, the original visual observer of the nebulosity, I was struck by the vituperative nature of the rebuttals of those who argued that if what was seen by ONE could not be immediately seen and corroborated easily by ALL, the error of the original observation was proved.

Five or six generations later, we chuckle at the shortsightedness and contentiousness of many of the skeptics on that issue. The nebulosity was there; because it was not generally seen in the conventional small-aperture, long-focal-length, high-magnification observatory instruments without low-loss modern optical coatings, its existence was controversial, placing it very much in the "NOT PROVED" or even "NOT TRUE" category.

This is not to denounce skeptics! But in the era before modern technology to record and transmit incontrovertible data, professional astronomers (working with such ludicrous instruments as limelight photometric reference light-sources) often posted observations that had little more enduring scientific merit than the comments of any amateur today -- crank or serious observer -- on this newsgroup!

We've all heard the term "NIMBY": not in MY back yard!

Well, there was during the 19th century in professional astronomical circles, a syndrome noted by Dr. Donald Osterbrock in his discussions of the debates regarding nebular lines measured at Lick Observatory in the exquisite seeing of Mt. Hamilton, and the denunciations issued by the Potsdam Astrophysical Observatory in Germany, using its small- aperture visual spectroscope under turbulent skies.

Endless tirades were offered by German astronomers, decrying the observations of James Keeler and other Lick astronomers. I might characterize them with the new term: "NIMT" - not in MY telescope!

Related articles appearing in professional astronomical journals, as reprinted in late-19th-century issues of the ASP publications, read like some of the exchanges on subjective issues in this newsgroup, and were NEARLY as unruly!

The work of Charles Perrine and Keeler in establishing the 36" 'fast' Crossley photographic telescope at Mt. Hamilton to augment the largely visual-use Clark refractor & spectroscope, plus the later developments by Vesto Melvin Slipher at Lowell Observatory -- which largely recovered the tarnished reputation of that organization, suffering from the adverse publicity generated by P. Lowell's canal claims -- put to rest much of this NIMT angst.

We return to these good old days of yesteryear, in comparing personal visual experiences of faint nebular objects. It's lots of fun, and dedicated observers including all the respondents on this particular thread, are enjoying it mightily, and of course all agree about the 'personal equation' element.

I think the thrust of my main argument...now long lost in the dust of this series of exchanges...is that some telescopes have lots of internal light-scattering. One who has not done many dozens -- perhaps even hundreds -- of visual observation of the utterly brilliant star cluster M-45, may have some difficulty in discerning where the internal reflections leave off, and where the nebulosity begins.

As Jay so well illustrates in his responses, someone who has made and confirmed an observation may QUICKLY show another person what to look for in the eyepiece view...often the other individual does a veritable ... smighting of the forehead, crying, "Of course! I see it now!" ... -- Steve Waldee

I can't claim that the passage of ten years' time has enabled me to improve so much as an observer that now the Merope nebula is "easy" (as it is for Jay Freeman); nor have I had the luck in discerning all the subtler fuzzy spots with the clarity shown in Risto Heikkilä's sketch. Indeed, my perception of M-45 hasn't changed very much at all, compared to what I wrote about in 1996. As part of my on-going program to discern challenging objects even in the presence of light pollution (chronicled in my observing articles, commencing here) I have revisited M-45 on numerous occasions, now with a new set of telescopes: a Celestron C-11 Schmidt- Cassegrain; an Orion 10" f/4.7 Dobsonian reflector, and an Orion 80-mm achromat short-tube refractor. The last instrument is particularly suited, as it can easily yield a much wider field of view than the entirety of the Pleiades cluster.

Yet, on various nights at the public observing site at Gilroy's Coyote Lake, or on private property I use at 3,400 feet altitude in the mountains north of Santa Cruz, the nebulosity was sometimes merely a general glow, barely distinct from the light-scatter observed in the field of any blinding star with my "fast" Dobsonian telescope (with conventional secondary mirror four-vane spider, which causes irritating spikes and reflections.) The results are consistently better with refractors, Maks, or SCTs (without the secondary mirror vanes), and telescopes such as refractors -- with no central obstruction at all -- give the most definite and highly-detailed view of the glow. Only once have I seen the nebulosity in a conventional Newtonian reflector with that much clarity: in the fabulous home-made 14" f/6 instrument built by a good friend, from a mountain-top during a morning of rock-steady subarcsecond seeing.

But, I've come close to it. The last time was -- with a large aperture instrument -- noted by me in my report on viewing the asteroid 2004 XP/14, in which I used my 10" Dob:

...we finally... decided, since it was pushing 3 AM, to observe some other objects during the last hour before twilight, looking at NGC 7023, and a few galaxies and nebulae in the Cepheus region. Before putting away the scopes we observed the Pleiades, only perhaps 10d above the horizon, and were surprised to see how incredibly steady the seeing was, even that low: traces of fine filamentary sheen were seen around some of the brightest stars, with or without a Deep Sky filter. Great night -- but too short!

And in a smaller aperture, I've seen the Merope nebula; but it still does NOT, in my particular experience, qualify to be described as an "easy" acquisition. In order not to be guilty of using terms such that my ranking would have an "undistributed middle", I would be careful to describe objects that were detected with almost any optic, even in a city sky, as "easy". Objects that are subtle, requiring optimal conditions and great diligence, would be "hard". (Though I've seen the Horsehead nebula dozens of times since the 1980s, frequency of observation does not give this object the attribution of being "easy".) Then, extreme challenge objects (such as "Gyulbudaghian's nebula") would be called, by me...err, 'supreme challenge objects': very, very hard. Many Messier objects, bright conspicuous galaxies, well known nebulae, and so forth, would be arrayed somewhere in the middle, some closer to the "easy" than to the "hard" category. What would I call "easy"? Well: M-42, for instance. With respect to my experience, the Merope nebula would have to be ranked as being 'moderately to significantly hard'.

For instance: on the morning of August 18, 2007, I viewed the Merope nebula using my 80 mm aperture Orion f/5 achromat, set up piggybacked onto my C-11. No trace of Merope's nebula was visible, even at the lowest power range I could get with the large, long focal length 11" aperture telescope; but the nebula was BARELY visible in the small refractor. The NELM was probably around 5.4 as the fog had not formed completely beneath my mountaintop site, and light was pouring from Gilroy and Morgan Hill to wash out the sky somewhat. Even after all the preliminary work I've done over the years, recalled by the discussion in this article -- and including a very recent email exchange of only the previous week, with Jay Freeman himself, about the Merope nebula -- I still found it a borderline object. It was detected only by means of the SkyGlow filter and a high quality 17 mm Plössl eyepiece (which yielded 23.5x with a 3.3 mm exit pupil.) My logbook says, "Seen barely, and by no other means of mag or exit pupil, nor w/o filter. Merope neb. dimmer than glow around four other bright *s in Pleiades."

This photograph, made by Solon I. Bailey about a century ago with the 24-inch aperture Bruce Telescope of Harvard University, shows no nebulosity (at least in the reproduction given in his 1908 HCO Annals paper, "A catalogue of bright clusters and nebulae".) Solon wrote, "The original photograph shows faintly the brighter nebulosities, but a much longer exposure is needed with the Bruce Telescope to show them to good advantage." He explains earlier that the exposure time for his standardized survey was one hour. That is significantly shorter than was used in that era of early astrophotography for recording nebulosity and the faintest stars. But, in a one hour exposure M-42, as one example, would be registered quite recognizably.

The way to 'move' the Merope nebula toward "easy" on MY scale would be to improve the telescope quite significantly, replacing its standard achromat objective with something of very high quality; improving its internal baffling; and by using a dialectric diagonal (these changes would result in an instrument that might cost ten or fifteen times more than the total amount of my ST-80 model scope, and accessories.) Then, I'd need to observe in an exquisitely dark sky, with M45 near the zenith. Eventually, one could get an optimal experience and then "step backward" holding the memory of the best view. I would suspect that this is what Jay has done, to convince him of the 'ease' of seeing it under varying conditions. But, sadly, not all of us have shared that optimal experience; perhaps, to us, it is still "hard".

I have also made repeated attempts to get a good visual sighting of the 'tiny' nebula IC-349 (Cederblad 19i, VdB 22), which many writers seem to confuse with the "larger" Merope nebula, NGC 1435. This wisp of nebulosity is, due to its proximity to the bright star Merope, a challenging visual observation; it's even somewhat difficult to photograph clearly (for more information on the picture shown here, taken by the Hubble Space Telescope, see this webpage.)

Had I known of Sue French's viewing report, much wasted time would have been saved: the information given by my laptop's computer programs turned out to be seriously flawed. I had the vague recollection that once on the Net I had read an interesting report by my friend Sue French, the "Deep Sky Wonders" columnist for Sky & Telescope magazine, and went a-searching for it recently. The post turned up in the unconscionably- annoying webpage of IAAC observing reports (a gigantic file that takes minutes to load, containing links to 6388 observing reports: can't they be broken down somehow into manageable chunks?) To save you the trouble, here is the direct link to her commentary; I quote much of it below. However, Sue has just notified me (04/12/08) that she has revised her post, including a correction of "one inadvertent direction switch in the background info"; but the revision so far hasn't shown up on the IAAC list. So I have substituted the latest text she has sent me directly:

* To: Internet Amateur Astronomers Catalog
* Subject: (IAAC) Obj: IC 349 (Barnard's Merope Nebula) -
Instrument: 14.5" f/6
* From: Susan C. French
* Date: Wed, 21 Apr 1999 10:27:55 -0400 (EDT) [revised 4/08 by scf]

Observer: Susan C. French
Your skills: Advanced (many years)
Date/time of observation: 2/3, 2/8, 2/9/99; 7:30, 9:30, 7 pm EDT
Location of site: West Glenville, NY (Lat 42.9°, Elev 1000ft.)
Site classification: Exurban
Sky darkness: good 
Seeing: g[ood]
Moon presence: None - moon not in sky
Instrument: 14.5" f/6
Magnification: 10.4mm w/occulting bar
Filter(s): no filter
Object(s): IC 349 (Barnard's Merope Nebula)
Category: Reflection nebula.
Constellation: Tau
Data: mag 13  size 30"
Position: [RA 03h 46m 20.1s  DEC +23d 56m 23s; updated from NEDS by Srw]

I decided to enter this one because I don't know any other amateur who
has observed it.  IC 349 is sometimes confused with the Merope Nebula,
but it is not.  IC 349 is a small, brighter patch within the Merope
Nebula discovered in 1890 by E. E. Barnard.  (I have the discovery
article in front of me as I type.)  It is only 30 arc seconds in
diameter and lies 36 arc seconds south and 9 arc seconds east of the
bright star Merope.  For this reason, I used an occulting bar in my
eyepiece to block out the glare from Merope.  I rotated the tube of my
telescope so that the diffraction spikes would straddle that object.
I left the scope's drive off, and oriented the occulting bar so that
Merope would gradually drift deeper into it.  On the first night I
thought I could see IC 349, but wanted to try again.  On the second
night I could frequently spot it.  For comparison, I examined the area
between the opposing diffraction spikes (i.e. north of Merope) and saw
nothing.  On the third night, it almost looked too easy.  When the
occulting bar was arranged just right, I could see a small brighter
patch on every pass.  Checking for scattered light once again, I
examined the area between the opposite pair of diffraction spikes.
Nothing like this was seen over several repetitions of letting Merope
drift along the opposite side of the occulting bar.  These were not
exceptionally transparent nights.  9 Pleiads were easy to the naked
eye.  One more was a little tougher, and two more were possible.
---------------

The info on size and direction came from Barnard's paper.  I can now
determine a more accurate position.  Of the many disparate sets of
coordinates for IC 349, Harold Corwin's seem to land closest to the center.
Some don't even land within the nebula. So, now I use Corwin's 2000.0
position:

03 46 20.1 +23 56 23

This puts IC 349 7.4" east and 31" south of Merope, or 32" away in PA 167º.
Measuring size from phototgraphic images in problematic at best, but it
should be something around 20".
-- Sue French

I made several cursory attempts to see IC-349 during times I had looked at M-45, in the fall and winter of 2006/07 at my observing site on private property, 3,400 feet high above sea level in the mountains north of Santa Cruz, California, where I've been observing since the late 1970s. The first attempt described below was hampered, as you will see, by conflicting information from various sources; unfortunately I did not have Sue's article with me, but I have learned not to make that mistake again!

On Monday, 8 January 2007, using my 10" f/4.7 Dob, in a sky I described as "V clear, Superb Seeing - 9 on Pickering's Scale!", I diligently worked at the nebula, whose coordinate center (according to my star chart program TheSky) was allegedly 57 arcseconds S and slightly W of 23 Tauri (Merope, SAO 76172, Magnitude 4.3): a star that is so bright it can affect your dark adaptation with a scope of this aperture. Getting Merope out of the field, I had an impression of something in the general haze of light, and wrote next to my sketches, "Maybe. Some c.12-14th mag * in & around it?" I tried using my 10 mm Orion Sirius Plössl plus 2x Shorty Barlow [240x, 12 min FOV, 1.05 mm exit pupil] and rendered the drawing on the left; then, with my 6mm Orion Expanse ocular [191x, ~15m FOV, 1.3 mm exit pupil] I drew what I saw on the right; I used no filter of any kind.

The Deep Sky Survey visible wavelength images on blue and red plates, produced by the 48 inch aperture Schmidt telescopes in California and Australia, were hopeless for determining the appearance and dimensions of the nebula, and distance from Merope; the best I could do with the blue plate, shown here at left, had such severe plate halation -- as well as overall nebular sheen -- around the bright star that almost nothing could be discerned in this picture centered exactly on IC-349's coordinates. I had better luck by using the UK2 infrared plate, shown to the right of the blue one, scanning a region of 3 arcminutes diameter around 23 Tauri and then increasing the luminance. The "little" bright nebula shows up indistinctly, but it's close to the diffraction spike created by the telescope's secondary mirror mount, and the contrast is affected by the plate's halation artifact.

Certainly the object is not as far from Merope as would be suggested by my drawings. Those would indicate that it's a few arcminutes away from 23 Tauri. Not so! I had a vague, gnawing worry that I wasn't really seeing IC-349 but a stable reflection artifact, which seemed to be created with either magnification (visible even after changing oculars.) I had no occulting eyepiece, as suggested by Sue; so I tried to move the scope to get the putative 'nebula' in different parts of the field, with the bright star around different regions of the periphery. The results were "iffy". At home, after measuring carefully the distances shown in the drawings, I decided that this was not a real observation, but a mistake of some sort -- though, oddly, what I seemed to have seen looked somewhat like certain photographs in magazines, and on the Net (though not at all like the phenomenal Hubble telescope image, as one might expect.) Yet, the scale was wrong...

Another possibility I've thought of later is that I had my directions mixed up, and was seeing a wisp of nebulosity in NGC 1435, VdB 22, or one of the Cederblad 19 subdivisions, all near the field of 23 Tauri: but not the closer IC-349. The picture I've created here uses the UK-2 Survey red (left) and blue (right) plates, and as you can see in the "less swamped" red image, wisps of nebulosity are visible across the entire region. Does an isolated patch show up clearly to the eye, at high magnification? I will have to confirm this with further observations using my other telescope, after isolating IC-349 for sure.

To get definitive information about the diameter of the object, I consulted various references, which tended to agree that its diameter was less than an arcminute. According to the NGC 2000.0 catalogue, IC-349 has a diameter that is "very small", some 36 arcseconds from Merope. But, oddly, the diameter of IC-349 is given in the information text file in the program GUIDE as being as follows: "Information from Nebula Databank" (by Eric-Sven Vesting) "IC-349 in NGC 1435 - Maximum Diameter 600 arcseconds" (10 arcminutes); NGC-1435 itself is described as having a diameter of "1800 arcseconds", so that description of IC-349's size was not conflating the two objects. Yet it is obviously indisputable that IC-349 does not really have a diameter of 10 arcminutes! To increase the confusion, the same program lists the diameter of Van den Bergh 22 (the same object as IC-349 according to other sources) as being "3120 arcseconds". My head was beginning to spin! What was necessary now was the direct and accurate scientific data of professional astronomers, not the rehashing of diverse contradictory amateur sources.

In due course I confirmed that both of my star chart software programs were quite wrong about the size and position of IC-349.

In the paper BARNARD'S MEROPE NEBULA (IC 349): AN INTERSTELLAR INTERLOPER by Drs. John Barentine and Gilbert Esquedero, an image of IC-349 taken by the Kitt Peak 4 m telescope in 1973 -- with a field height measuring 155 by 120 arcseconds -- may be utilized to get an approximate diameter of the nebula (which is, according to my best judgment, 28.5 by 18.3 arcseconds, although the picture is much fuzzier than the one taken by Hubble -- which has no referenced size that I could determine.) So, let us accept that as a practical working value, the nebula is half an arcminute long, as discerned in optical wavelengths.

The position of the nebula with respect to Merope is confirmed in this scientific paper, "BARNARD'S MEROPE NEBULA REVISITED: NEW OBSERVATIONAL RESULTS" (by Drs. George Herbig and Theodore Simon, written in 2000.) Its authors state that IC-349 is, in fact:

"The brightest portion of the Pleiades nebulosity... On conventional photographs, it is concealed in the overexposed image of the 4th magnitude 23 Tau (Merope), about 30 arcsec. distant. The structure of IC 349 is quite unlike that of the general nebulosity; it is triangular in outline, with a semistellar nucleus at the apex nearest 23 Tau and an axis of symmetry pointing approximately in that direction. It contains considerable internal detail even at modest angular resolution. Clearly, it owes its illumination to that star; as far as can now be discerned, the spectra of IC 349 and 23 Tau are identical...

"The resolution of the HST images is about a factor 8 better than that of the ground-based images discussed in H96, and as a consequence, the model of IC 349 proposed there must be modified. IC 349 contains much complex structure that, it now appears, did not emanate from the "nucleus." ... In outline, IC 349 is shaped like an arrowhead, with the nucleus at the apex, pointing toward 23 Tau. It will be argued... that this is also very nearly the direction of motion of IC 349 with respect to the star cluster. The earlier low-resolution images showed the nebula to be outlined by several ribs, or veins... They are now seen to be cirrus-like ridges, well defined on the "upstream" side toward 23 Tau but with tattered "downstream" edges. A number of thin plumes extend upstream. Fainter structure exists between the ridges, much of it in short arcs convex to the upstream direction. The nucleus is only the brightest and, presumably, the densest nodule in the leading upwind ridge.

"We propose that IC 349 is the consequence of a small cloud, probably containing some internal structure before it approached 23 Tau, that has been compressed and, to some degree, dispersed during the encounter by either the radiation pressure or wind of 23 Tau... radiation pressure would have a demonstrably significant effect on IC 349, given the separation, the luminosity of 23 Tau, and plausible assumptions as to particle size and composition, while no significant stellar wind from the star has been reported.

"We suppose that the composition of this cloudlet when it approached the Pleiades was typical of moderately dense interstellar clouds with respect to the relative abundances of H, CO, and solids. We assume the latter to be composed of silicates and graphite particles in comparable proportions, whose optical properties are those inferred from Mie theory." -- Herbig & Simon

My next try -- having more knowledge about the circumstances of size and position necessary for a successful observation -- was with the same scope, same site, on Wednesday 17 January 2007, with a sky that was "steady, but windy". I wrote that at 9:15 to 9:45pm I studied the region of Merope for IC-349, scribbling: "Perhaps caught 1 glimpse with 3.7 Epic [323x, 10 min FOV, 0.8 mm exit pupil]. Possibly saw also with 6 mm Plössl + 2x Barlow" [400x, ~7 min FOV, 1.3 mm exit pupil]. I chose that particular Plössl because it has much lower internal reflections and light scatter than my 3.7 mm Epic ocular (which itself has been modified, with blackened lens edges and internal flocking added.) "Otherwise v hard. Later, as the star was setting, it moved too close to spider's diffraction spike; gave up" (unfortunately, the tube of my Dob scope cannot be rotated.) I made no drawing, but intended to make another observation very soon with my C-11 (which did not happen due to humid weather conditions at my site during the most advantageous months.) Yet, I had the distinct feeling that what I had seen was different than the earlier observation, and possibly a vague impression of what Sue French had described.

My logbook records no attempts using the superior C-11 telescope, which has lower internal light reflections, as well as a longer focal length that permits easy use of high magnification. Now this season it's too late to see M-45, so my next trials will wait until fall/winter of 2007.

I was frankly reluctant to write any of these observations up, because I did not feel CONVINCED I had really seen IC-349, especially in light of the data of dimension and location given by the best references, quoted earlier. The first observation may be spurious; the second one is not at all certain, for though I seemed fairly satisfied at the time, I recorded no mention of the specific distance of the nebula from the bright star, and produced no sketch, since I had intended soon to work on it more carefully with the C-11 (which was not to be.) NEXT time, I'll be more thorough; and by fall I intend to make myself an occulting eyepiece!

Meanwhile, this post by Jay LeBlanc to the Astronomy Connection mailing list in January of 1999, which I just discovered, gives me further guidance for experimenting with eyepieces to view IC-349:

That occulting bar I mentioned in a previous message is really just a piece of electrical tape which covers 1/2 the field, mounted at the field stop inside the eyepiece. In my case it is a rather ancient 16mm ortho. I just rotate the eyepiece to change the orientation. Any ocular with a focal plane would be fair game, on my 17.5-in it gives 124x. I suppose a more elegant version could be made with a broken bit of a razor blade and a spot of super glue, but this simple version works. Procyon's companion was not all that difficult, considerably dimmer than Sirius B, but about the same separation at ~4", it was helpful that Procyon was not as bright as Sirius!

While the above were not among my most exciting observations, do try IC 349! I was amazed to see this bright tiny object right next to Merope, in a field I've looked at numerous times. The occulting rig makes it easily seen, but it can be spotted as an 'extension' to Merope in a conventional eyepiece.

Here's my notes on IC 349:

124x + Occulting bar Quite small and very close to Merope, and rather bright, clear and easy! 1.5 to 1 aligned toward Merope, NNW-SSE, very close SSE of Merope, nearly in line with a faint double which points to Merope at some distance with a PA a bit more SE than the nebula. -Jay-

I'll be ready: I can't wait for the Seven Sisters to reappear in the late night sky!

Update, 14 Aug 2007: I have been luckier in August, 2007, following the advice of Sue French. Click for a recent article in my astro blog which contains the report of my last attempt -- apparently successfully -- to view IC-349. And if you scan down about 1/4 way through this astro-blog article about the eyepieces I use, you will find a brief discussion, and picture, of modifying a Plössl for use as an occulting eyepiece.

Steve Waldee, Waldee-Wood Astronomical Software, 4/03/07 & 9/30/07

The critiques of my Pleiades article by Jay and others prompted me to expand on the subject of variability, or "the personal equation" of visual astronomers, affecting their critical perception. To Jay, the Merope nebula was often "easy"; it wasn't the same way at all for me (nor is it, as quoted above, for Jaakko Saloranta, a very gifted observer.) I have looked at the contention afresh, ten years after it was aired on the newsgroup. It seems to me very quaint. Obviously the main issue, aside from two different individuals with their own unique combination of skills, perception, and cognition, is the very real fact that generally I observed with a "fast" Newtonian telescope, and Freeman often used a refractor (with no central obstruction, and very high image contrast, generally offering less internal light scatter than any standard Newtonian telescope.) So the distinction of the exquisitely fine sheen of nebulosity apart from a general vague glow around the stars, often seen in reflector scopes due to light scatter, would be easier for Jay (with refractors, Maks, or SCTs and their often lower internal reflections and reduced visual artifacts), than for me, by definition. At the time, I posted a reply which I hoped to dispel the argument. Of course, it didn't do so. I quote it, below.

On Mon, 25 Nov 1996 19:47:59 GMT, free...@netcom.com (Jay Reynolds Freeman) wrote... regarding the visibility of the Pleiades nebulosity, and specifically the Merope nebula:

>In article <3299CD20.1...@ix.netcom.com> Jay Freeman counters:

>People with garages full of telescopes (pardon me while I
>try to close the door to mine) are in great part victims
>of materialism, marketeering, and hyperbole... I have logged
>31 observations of the Merope Nebula, with 16 different
>instruments, from 7x50 binocular to 17.5-inch Newtonian.
>The range includes six binoculars, five Newtonians, two SCTs,
>two refractors, and a Maksutov. I rarely waste time with a
>truly lousy telescope, and some of these instruments
>were indeed world-class, but by no means all of them.

Jay has thus recorded a clear view of the Merope nebula with instruments that are not all of exceptional quality, unlike Steve Waldee, who has often had difficulty seeing it. Yet I doubt that Jay and I observe more than 15 miles apart!

It's interesting to discover, using one of the world's most familiar objects, the differences of perception of two observers. That very well categorizes the quandary of pre-photographic professional astronomers during the 19th century. The "personal equation" was first and foremost an element in evaluating practically anyone's published observation of a celestial object.

I did a series of talks on the photographic history of the Orion nebula, and for it I researched the remarkable 300+ page dissertation on the nebula by the first director of Lick Observatory, Prof. E. S. Holden. He studied observations of the nebula back to the days of Christian Huygens; dozens of engravings recorded careful reproductions of the originals dating back to the 1600s. Such wonderful observers as Cassini, Mechain, Messier, the Herschels, and Trouvelot were presented; only Trouvelot's effort resembled a modern photograph. Of the old drawings, Messier's at least had some SEMBLANCE of reality, though the stars were severely out of place.

Holden himself -- though he was NOT regarded by his later colleagues as a careful observer -- made a visual study and photometric series on the Triangulum region with the 26-inch Naval Observatory refractor, and determined to his complete satisfaction that the nebula was widely and wildly variable! He closed with the confident assertion that the 'new science' of photography would confirm him. Perhaps in some ways it has...but not in the manner that HE would have expected!

In Holden's time there was a general question about the Triangulum region: most professional observers asserted that the asterism was in a 'hollow' in the nebula containing no background nebulosity; today, with our high-transmission eyepieces and light pollution filters, we can easily detect the milky background behind the points, though it is indeed not as bright as the boundaries of the 'fish mouth' region.

I reproduced these drawings from Holden's study in slides that I showed at about 6 different northern California astronomy clubs, and the audience was quite surprised at the variance in observation and descriptions of the nebula...some resembled grotesque bellowing elephants; others were angular, sharp, and almost "art-deco" in their stylization. Practically none of these drawings...made by the absolutely leading observers of their periods...was accurate in any way, neither resembling what most people now see through modern telescopes and oculars, or what almost ANY kind of photograph records.

A chastening lesson for those of us -- certainly not a sophisticate like Jay but some who might tend to take a hard line about the 'subjective' aspects of visual astronomy -- to learn well.

Yours,
Steve Waldee,  Nov. 26, 1996.

A RECENT ATTEMPT TO DUPLICATE JAY'S EXPERIENCE

On the night of Sunday, 8 April 2007, I made the effort to devote the first part of an observing session at my site on private property, at 3400 feet above sea-level in the mountains north of Santa Cruz, California, to an observation of M-45 after the end of astronomical twilight, before the cluster disappeared behind a large tree that cut off a clear view. The seeing was very steady, and the air was transparent; but residual light pollution in the region of the southern SF peninsula was impacting the sky background darkness. With my 10" reflector scope I carefully studied the brightest stars with, and without, a filter of LPR type, mindful of Jay's admonition that the Merope nebula looked to him like "a long, broad streamer trailing out away from the star, away from the center of the Pleiades", very obvious because of its asymmetry. I have done this test before, hoping to duplicate what Jay asserts is a distinct difference between the glow in the region of Merope, and the general milkiness (plus telescopic light scatter) in the region of at least six of the stars in the cluster. Again, sadly: this asymmetrical patch was NOT OBVIOUS to me (in the reflector telescope, though it's better in my refractor, as discussed in this observing report): the reason probably being due to residual light pollution and instrumental scatter. No matter how enthusiastically and insistently one might argue that this ISN'T SO, the issue is simply moot if another careful observer, making no obvious mistake, fails to duplicate the experience. This was the point of my original article: to explain to persons who use less than the best scopes, and darkest sky conditions, that their experience of the nebulosity may be affected by factors that diminish and confuse the results.

For some opinions of mine on the subjective, idiosyncratic nature of visual observing, see this related article.

UPDATE, 10/23/07: