Posted Originally to sci.astro.amateur:
19 Feb 2007 15:37:51 PST
Friends,
This is not intended to be a really thorough review since I have
nothing similar to compare the eyepiece to; rather it's just a brief
description of the performance of the ocular in my first trial under
the stars.
With all due respects to Nagler products and enthusiasts, I have not
the budget nor inclination to purchase one of their magnificent but
costly products in a focal length near 32 mm. I very rarely use this
focal length in either of my scopes -- a C-11 and an Orion SkyQuest
10" f/4.7 Dob -- since usually I am employing much higher
magnification for the things that I prefer to see (small diameter
galaxies and PN's.)
But I was extremely disappointed with the performance of the Orion
"Sirius" 32mm eyepiece with nebular filters: eye positioning is (for
me) extraordinarily critical and fussy with this ocular, in either
scope. And my 42mm 2" SuperWide (oriental import, obtained from
StellarVue) produces an overly-large exit pupil in the Dob. So I have
been thinking about getting a 32 mm 2" eyepiece for some time, and was
considering the more expensive Orion "OptiLuxe" (costing $150,
compared to $100 for the new Orion Q-70 in the same 32mm focal
length.)
I decided to try both of them in the Cupertino store, in the same
model scope, and then unless there was something obviously wrong with
the Q-70, to purchase it and try it out at night, trading up to the
OptiLuxe only if necessary, in case I did not like it, before return
privileges ran out.
My tests of the Q-70 convince me I will keep it and not trade up to
the OptiLuxe.
In the store, I found that the OptiLuxe *seemed* to have a slightly
brighter view of terrestrial sights (a large building a block or so
north of the store, along Hiway 9, which is about the closest thing
you can get in focus with most of the Newtonians) though it is hard to
keep in memory the exact brightness and contrast of an image when you
have to change oculars and re-focus. But, the eye relief of the
OptiLuxe was much poorer than the Q-70; and it was noticeably narrower
in field of view.
I discovered in the store that the barrel of the OptiLuxe on display
was very slightly larger in diameter than the one of the Q-70 taken
out of stock. In fact, it was very difficult to get the OptiLuxe in
and out of the new Orion Crayford focuser (same as on my 10" Dob): a
further worry.
Neither eyepiece would quite get in focus when pressed fully against
the top of the focuser's eyepiece holder ring, focuser fully extended.
But I was not certain if the building was actually far enough away to
be considered at "infinity". Both the store manager, and I, found
that it was necessary to pull the Q-70 out about 1/4 inch or slightly
more, to get it in focus.
Not a big problem, as there are two screws on the holding ring; and
one can always make a small "parfocal" adaptor ring and place it over
the barrel.
I purchased the Q-70 and then, two days later when the weather
cleared, tested it in the 10" Orion Dob at my site on private property
at 3,400 feet elevation in the mountains south of San Jose.
I was pleasantly surprised at the clarity, expecting a cheap eyepiece
-- definitely not in the same league as a Nagler -- to have clean
stars only a small inner diameter of the field. The star images were,
however, fairly good to at least 75% of the full field diameter,
better than several of my other moderate and lower power oculars (I do
not presently own any Naglers or high end coma-correcting eyepieces,
though I have in the past.)
Here is my simulation of what a perfect looking star field would
be, with complete sharpness edge-to-edge.
Here is my simulation of what star field would look like in my f/4.7
reflector scope, using the Q-70 eyepiece, with sharpness over most of the field
except the edge, and a slight softness due to the curvature of field away from
the exact center.
There was a slight difference in optimal focus position for stars
right in the center of the field, and stars over to the edge, as I
expected with an eyepiece of this relatively simple design and few
elements, used in a fast Newtonian. I could find a reasonable
compromise focus so that the whole field of stars looked acceptable,
for viewing things like the Double Cluster.
Unfortunately, at such low power (37.5x in that scope) my eyes tend to
produce slightly astigmatic star images, evident when I use also my
42mm, my 40mm 1.25" Celestron E-Lux, or my Orion Sirius 32mm 1.25"
Ploessl. So how much was caused by the eyepiece, and how much of the
astigmatism is in my eye, I can't quantify. The only way I think I
could do so would be a careful direct immediate comparison on stars
with top quality Naglers or equivalents, which I haven't done (and am
not likely to do, as I almost never attend star parties.)
But I can say that my 42 mm 2" eyepiece, in the C-11, produces MUCH
worse astigmatism than the 32 Q-70 does in my 10" Dob: so I suspect
that the Q-70 would be no worse than the OptiLuxe in that respect.
The star image quality in the Q-70 was actually quite a bit better
than I had pessimistically expected.
The star image sharpness in the C-11 was even better, with very good clarity
nearly to the edge of the field. Here is my simulation of what that same star
field shown above would be in my C-11.
The eye relief and positioning are good although I found it necessary
to put down the rubber eyeguard to comfortably see all of the very
wide field. Only the stars at the very field edge were ugly, and then
they weren't nearly as bad as in the 42mm ocular.
It is hard to compare the Sirius 32 mm 1.25" against the 32mm Q-70,
due to the unpleasant characteristics and touchy eye positioning of
the 32 Sirius in a short focus scope.
However, I did find that, as I had hoped, using a nebular filter with
the 32 mm Q-70 was *distinctly* more pleasing and comfortable than
with the 32 mm Sirius Ploessl. The filter threads on the Q-70 were
very well cut and perfectly fit my Orion 2" UltraBlock.
I was able to get some good views of nebular objects of large diameter
that are a veritable *pain* in the 32mm Sirius 1.25". M-42 was quite
a spectacle. In particular, I confirmed my earlier viewing several
weeks ago of Abell 7 in Lepus. It was far too late in the evening for
best conditions but I was dodging clouds and had to wait until the
region was perfectly clear. Finally, about 2-1/2 hrs after Abell 7
had transited, I saw it with the Q-70 and the UltraBlock filter, with
much more ease than I'd seen it earlier with the 32 mm Sirius and OIII
or UltraBlock. This is considered a difficult observation for a 10"
scope, to say the least. So I don't have any reason to suspect that
the eyepiece will fail to give me good performance on faint objects.
Now, I shall have to get a 2" OIII filter too!
So, I'm keeping the Q-70. I'd also love, some day, to replace the
focuser on my Orion 120mm f/8 refractor with a 2" barrel model, to
take advantage of it with that scope.
AstroApp
Wed, 21 Feb 2007 12:16:49 PST
As I said earlier, the 32mm Q-70 does seem to show stars (at very low
power in my 10" f/4.7 Dob) with some astigmatism. I did a further
test of this the next clear night, and was surprised that the Q-70's
star images were actually quite a bit "tighter" and cleaner than those
yielded by my Orion Stratus 21mm eyepiece -- which I'd considered
acceptable in the Dob, though it looks nicer in the C-11.
What would be useful to be able to judge the absolute quality of the
Q-70 is of course a run-off against a really high end ocular. I used
to own a 32mm Televue 2" eyepiece, made probably about 15-18 years
ago. I seldom used it in my 8 and 10 inch scopes because I did not
like the fussy eye positioning and the star aberrations -- in fact, I
bought it used from a very discriminating observer who got rid of it
in order to trade up to the later improved TV eyepiece in a similar
focal length, but with wider field and better correction. I too
decided, after a while, that this old 32 was slightly unsatisfactory
(though it was far better than a cheap bottom-barrel Ploessl I'd
earlier purchased for about $50!)
Memory can be faulty, of course, but my impression of the Q-70's
performance in my current scope is that it is considerably more
satisfactory than that old TV model had been in the instruments I used
to own (that ocular is not made any more, but was probably a
modification of the Ploessl design.) Once again, the oriental
knock-offs are producing good value for the money, for those of us who
have a more utilitarian approach to eyepiece collection, rather than a
connoisseur's appreciation.
AstroApp
Author's little 'parfocal' positioner made
of two cable ties around barrel
Sun, 04 Mar 2007 13:46:14 PST
In my initial comment about the Q-70 I mentioned that in the Orion 10"
Dobs, it is necessary to pull it out of the focuser for a certain
distance, even with the focuser tube fully extended.
Under the stars at night, this distance -- for my eyes -- was about
3/8ths of an inch. To increase the convenience I found that I could
wrap two nylon cable ties around the barrel and tighten them so that
their holding clips were opposite each other. Then, the eyepiece fit
nicely into the barrel and could be held without tilting by the two
screws for 2" eyepieces. The width of the cable ties may be altered
as needed in this simple form of a quick 'parfocal ring' workaround.
I don't consider this a defect of the eyepiece since it is hard to
make a Newtonian with a focuser that reaches correct position with
every single eyepiece on the market. To avoid vignetting, modern
focusers don't have the long barrels of the older models that were
once sold.
With my C-11 there is sufficient focus travel, needless to say.
AstroApp
Followup:
I don't remember who made the recommendation, but I appreciated learning in an astronomy forum that an easy way to make a parfocal adaptor for 2 inch eyepieces was to use a rubber O-ring. I found at my local Ace Hardware store the ideal size, Ace #110 (2 inch ID), P/N 9D0014641B. Two (or maybe three) of these rings will place the Q-70 eyepiece at about the right distance, without the 1.25-2" adaptor, as my usual 1.25" oculars, using the 2" focuser adaptor.
The new 32 mm Q-70 eyepiece continues to be a joy to use, either in my 10" Orion Dob, or in my C-11. Viewing large diameter nebulae like M-42 is stunningly satisfying, compared to the 32 mm Orion Sirius 1.25" eyepiece, so much that I purchased a 2" UltraBlock filter, and intend to get a 2" OIII model as soon as I can afford it. The performance in the C-11 is quite excellent, with very good star images throughout most of the field diameter; only the edge is slightly rough. With the "fast" Dob, one has to rack the focus a bit while moving the eye across the whole field, due to the curvature of the focal plane produced by an f/4.7 parabolic primary mirror. This is much less discerned in the f/10 Schmidt-Cassegrain scope, my C-11. I also do not notice significant "pincushion" or "barrel" distortion, which -- if present -- make star fields look strange (see this Wikipedia page for an explanation.) I haven't found instances of any significant optical reflections causing a washed-out field (a problem with some other Orion eyepieces I've owned, such as my 3.7 mm ED Epic.) Rather than giving me performance that fell short of my expectations -- which so often seems to happen when one buys a new, inexpensive product -- the Q70 has definitely exceeded my hopes. -- srw, 3/29/07
In fact, I like the 32 mm model so much that I have now purchased the 26 mm Q-70. -- srw, 5/20/08
Press BACK key,
or click for Jottings Commentary,
or return to the
Full Moon Essay Menu Page.
Tuesday 27 March 2007 at 9:02 pm; last edited Sunday 1 June 2008 at 11:48 am.
Copyright © 2007-8 Stephen R. Waldee - All Rights Reserved.
All Trademarks or Copyrights are © or Property of Their
Respective Copyright Holders.