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Resolution and Star Tests of ATX Scopes (1 Viewer)

Kimmo and Gijs,

Thanks for your efforts. I think we can now almost put to rest the question of magnification variations in the different models. I say almost because it would still be interesting to see how the ATX-95 Nr.1 and ATX-85 Nr.1 in Gijs' tests would measure with their eyepiece modules exchanged.

Gijs, I think Michael is referring to the scope I mentioned in my first post. If you're not familiar with it, Astro-Physics is a small company in Illinois owned by the master telescope maker Roland Christen. He produces some of the world's best astronomical APO's. Production numbers are very small, so to buy a scope you must place yourself on a waiting list and be prepared to wait for at least several years.

Henry
 
Henry,
Thank you, I did not know the company Astro-Physics.
If I have time left I will see what happens when the eyepiece models of the ATX number 1 measurements are exchanged, but I immediately admit that it is not high on my priority list.
 
Gijs, Henry,

I noticed there was a slight omission in my data in post #19. The maximum magnification reading for the ATX 95 had a range of 28-28.5mm, not just 28, which is why there was a range for the zoom ratio for that scope also. With single figures, there would of course have been a single zoom ratio.

Gijs,

With your new measurements, and especially taking into account the margin of uncertainty in them, I concur with your conclusion that we may take Swarovski's published data as being accurate. But, since 2.4 x 30 = 72, the maximum magnification figure for the large scope seems to be rounded down in the Swarovski literature.

Thanks for going through the trouble of measuring so many scopes again.

- Kimmo
 
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"Have now seen two more 85's and one more 95 ATX.
Image quality in the second 95 looked just as good if not a bit better even than in the first 95. I only tested it indoors today, at the shop where I don't know the exact distance to the target. The target is the Edmunds glass slide, mounted in front of a white sheet of paper (but not against it) with a window behind and a halogen desk light illuminating the slide from about a 40 degree angle from the front, about a foot from the slide. They have used this setup to check a lot of scopes, and I have checked perhaps a half-dozen there this way. Kowa 883's can let you see the orientation of the line pattern in group 3/elemnt 6 there providing the sample is good, but only barely. Other scopes are considered good samples if they make 3/5. The 95 makes 3/6 easy, and 4/1 can be resolved to my standard of what I consider resolved. The 85 there today struggled with 3/5 but resolved it. My Nikon (did not have it today) has also barely resolved the 3/6 there. Unboosted star-testing with giny glitter points on a chrystal/gold Swarovski miniature binocular bling-bling item showed ecellent symmetry in diffraction patterns, easily discernible rings either side of focus already at 2-3 rings, and no other defects besides some triangularity that resembles slight pinching, but fortunately with no flare from the roundish corners. Trying the same objective with the back that came with the 85 added an ever so slight bit of astigmatism, just enough to prevent seeing the orientation of the horizontal 4/1, and made the focus a tad more difficult to achieve. The 85 showed a more messy diffraction pattern, but still good by most standards. The 85 that I saw at another store last Thursday was significantly better, about as good relatively speaking as the two 95's. All of the ATX's I've been able to look at diffraction-patterns with have exhibited tiny amounts of coma as well, but in only one 85mm was it enough to begin to compromise the image a little."

So, my observations are very similar to yours, and put together they give a very favorable first impression of the general quality of these unusually complex scopes. I was certainly worried about excessive sample differences, but our admittedly small sample has not yet included any lemons.

Kimmo

Hi,
I read several times that all scope are not equivalent within a same model. This amaze me! Who can confirm?
For my point of view, it is unacceptable for an equipment of nearly 4000€, you can pick the wrong one.
Regards
Yves
 
Yes there are sample variations in even high end scopes.:eek!:

http://www.birdforum.net/showthread.php?t=237786

It would be a good step forward if the manufacturers of high end optics took a leaf from the book of the custom telescope makers and included the quality control document showing the performance of the item.
I do not think that this would be costly, given the routine use of automated test gear, but it would help set an objective threshold, which might revitalize a stagnant market.
Currently there is absolutely no trustworthy information provided by the manufacturers, even the basic parameters such as aperture or magnification are often a bit off.
The advertising is indistinguishable from beer ads. 'lighter', 'clearer', 'more natural', are the operative adjectives. This kind of content free marketing devalues the brands.
Ads offering concrete and specific information could be a powerful market differentiator in this sea of vapid hype.
 
It would be a good step forward if the manufacturers of high end optics took a leaf from the book of the custom telescope makers and included the quality control document showing the performance of the item.

I agree and think that this is a good idea. As far as I know, Docter seems to be the only manufacturer leading with a step to the right direction by providing some information about a minimum standard of resolution for their Aspectem 80 ED binoculars: http://www.docter-germany.de/nc/service/downloads.html?cid=4463&did=3748&sechash=39a56244 , see the table of the specs.
Also, they are giving exact information about the distorsion of their 84°-AFOV eyepiece, which is available with the Aspectem but as well solo with 1 1/4" fitting for use with astro-telescopes (17,3%).

Steve
 
I agree and think that this is a good idea. As far as I know, Docter seems to be the only manufacturer leading with a step to the right direction by providing some information about a minimum standard of resolution for their Aspectem 80 ED binoculars: http://www.docter-germany.de/nc/service/downloads.html?cid=4463&did=3748&sechash=39a56244 , see the table of the specs.
Also, they are giving exact information about the distorsion of their 84°-AFOV eyepiece, which is available with the Aspectem but as well solo with 1 1/4" fitting for use with astro-telescopes (17,3%).

Steve

To add some specifics to this discussion, the Lens Rentals site has an excellent discussion of sample variation for a couple of top tier Canon lenses:

http://www.lensrentals.com/blog/2012/11/canon-24-70-mk-ii-variation#more-10262

The spread in performance is quite wide, about +/- 12% for best line pairs/mm resolution if I've read it right, eye opening variability considering that these are sealed lenses, no interchangeable eye pieces involved.
So even at the premium level, cherry specimens are still well worth looking for.
 
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