Re: WTB: inexpensive achromatic lens

Bob Bond (rgb@db1.ncube.com)
Fri, 24 Mar 95 15:32:56 PST

University Optics has a nice 80mm refractor kit for $395.00 or thereabouts but it doesn't have a mount. They sell mounts separately but I don't have my catalog here. I bought an 80mm surplus binocular lens from them that I used in a finder I made with a 35mm eyepiece, but I don't think I'd recommend it for use with a much higher power eyepiece. It is not very well color corrected. I think it was under $70.00.

I've appended a note from the sci.astro.amateur newsgroup that reviewed the 80mm kit.

Bob

From: BUNNER@MACC.WISC.EDU (MACCMICRO) >Newsgroups: sci.astro.amateur
>Subject: University Optics 80mm - First Look
>Date: 14 Oct 1994 19:04:37 GMT
>Organization: UNIVERSITY OF WISCONSIN -- MADISON
>
>Review of University Optics 80mm Refractor.
>
>I've been looking for a portable scope for quite a while to compliment my
>13" Coulter. I previously tested a now-discontinued Orion UltraScan 80 and
>found it wanting. And I can't afford an AstroPhysics Traveler, nor even
>a Televue Pronto. So when I heard a few positive reports about the
>University Optics 80mm Refractor, sold by them in kit form for $349.95,
>I decided to investigate. Further inquiries of a number of UO-80 owners
>convinced me it was a good quality scope. So I decided to buy one.
>
>However I then found out it was in short supply and on a 2-4 month back order.
>On a hunch, I decided to call Pocono Mountain Optics and see if they knew
>where one might get one, or if there were other alternatives. Turned out
>they had a used UO-80 they were selling for a private party and put me in
>touch with him. I agreed to pay $275, perhaps a bit high, but it was
>already assembled and said to be in excellent working order.
>
>It arrived yesterday and I put it to a number of tests, before the clouds
>rolled in. First, as a spotting scope in daylight conditions it is
>excellent. Using a Televue 40mm (12.5X) and a Meade 24.5mm (20.5X)
>eyepieces, I trained it on a number of ground objects and a few planes
>on the horizon. It yielded razor-sharp images with no hint of chroma
>aberrations. Images were very sharp on-axis with no apparent decrease in
>sharpness across the width of the lens. Plus, with the 40mm, I was
>able to focus on objects as close as just 9' feet away. This is an
>excellent figure even for a true spotting scope. I would be willing to
>match this scope against the non-florite Kowas and Fujinons scopes.
>
>It was much more difficult to test it at night due to the woefully
>inadequate mount I was forced to use, a $30 SLIK lightweight camera tripod
>and friction pan head. The slightest touch of the pan head tilt lever, the
>focus knob, or even my eyebrow against the rubber eyecup of the eyepiece
>would set the scope to bouncing for 7-8 seconds. A mount upgrade is already
>in the works.
>
>Nevertheless, with some patience, I was able to perform a number of tests.
>M45 was absolutely beautiful at 12.5X in a 3.5 degree field. Images were
>very sharp and even Vega and Deneb yield no hint of blue (perhaps due to
>the skies not being particularly dark due to a bright Moon). Lunar images
>were also very sharp with no color distortions noted.
>
>The same results were obtained with the Meade 24.5mm at 20.5X. Then I pushed
>both eyepieces by inserting a Meade 140 2X Barlow before the star diagonal.
>Images continued to be sharp, very little degradation. I don't know the
>exact effect this Barlow has in this configuration, I believe it to be
>from 2.5X - 3.0X. So I was working with magnifications likely ranging from
>30X-60X.
>
>Next I moved to my Meade 4.7mm Ultrawide (Nagler equivalent). With a 500mm
>focal length and f/6.25, this yielded a 106X image, 0.75mm exit pupil, and
>an actual FOV of about .75-.80 degrees. It took several minutes to find
>and focus on each object, due to my wildly bouncing mount. Centering Saturn
>was very frustrating. However again the images more than exceeded my
>expectations. Saturn was sharp with well-defined rings. With the Moon
>hanging nearby, contrast suffered and I wasn't able to do much in the
>way of examining surface detail. Lunar images were again quite good,
>the terminator line was sharp and surface features well defined. Then
>I turned my attention on Epsilon Lyrae, to my amazement I was able to split
>the double-double at 106X. I can't do this with my Coulter (I've got to
>push it to over 120X to split it). I allowed EL to drift across the field
>and was able to see separation almost to the lens edge. Very impressive
>off-axis sharpness.
>
>I then attempted to push it past its limits and used the 4.7mm in combination
>with the Barlow. At this magnification (250X-300X) on my shaky mount, it took
>a few minutes just to center & focus the Moon. The image was fairly dim
>(I'm now working with an exit image size of roughly .3mm) and definitely
>less sharp but still usable. I had expected a fuzzy blur at this point
>but was able to clearly make out surface features.
>
>All in all, I am extremely pleased with the scope. Very portable (only
>weighs about 5 pounds), 2" focuser (w/1.25" adapter) with nearly 6" of
>focus travel, much lower than expected chroma aberation considering it
>doesn't use SD glass and is a fast f/6.25 design. A heckeva portable
>astronomical/spotting scope for $275 or $350. Can't wait to do some side-
>by-side comparisons with a Pronto (except I wouldn't want to be matched
>up in a beauty contest, the UO-80 has a very spartan appearance).
>
>Dana