henry link
Well-known member
I had an opportunity to do resolution and star tests of several ATX modules in a store recently. Three objective modules were available (two 85mm and one 95mm) and two prism/eyepiece modules. I set up a USAF 1951 resolution chart and an artificial star and, for comparison, I brought along a reference scope with essentially perfect optics, an Astro-Physics 92mm Stowaway APO. For testing purposes I was able to boost magnifications up to 180x (85mm) and 210x (95mm) using a Zeiss Tripler, which happily fits the ATX eyecup perfectly with the FL binocular eyecup adapter.
When star tested all three of the objective modules proved to be very well corrected for spherical aberration, probably around 1/6 wave. In my experience that’s considerably better than the average expensive spotting scope specimen. In fact it’s close to cherry territory, which I wouldn’t expect from three randomly selected samples. The 85mm modules showed a little more chromatic aberration in out of focus diffraction patterns, which fits logically with their slightly lower focal ratio.
There were some minor optical defects in each of the objective modules. All were slightly comatic and the 95mm also showed some astigmatism and pinching. None of the defects appeared to be associated with the prism modules. Each objective showed the same defects regardless of which prism it was matched with.
Since they were pretty mild and the spherical correction was good the defects didn’t appear to have much effect on the resolving power. The 95mm could resolve the same element on the USAF chart as the Astro-Physics Stowaway though not as cleanly. I wasn’t able to easily move the scopes for a more precise measurement, but I would estimate that this particular 95mm’s resolution falls between 1.25-1.3 arc seconds. Both 85’s resolved one element larger, about 1.4-1.45 arc seconds. These are very good figures for spotting scopes. The 95 has the best raw resolution I’ve measured for a birding scope although it’s no better per mm of aperture than the best Kowa 883 I’ve seen. A 95mm module this good without any astigmatism would probably do a little better.
I didn’t have time to test any eyepiece characteristics, but I found the new zoom very comfortable to use, with none of the blackout problems I’ve experience with the 25-50x Swarovski zoom. The zoom ring was a bit harder to turn than the focusing ring, but its motion is smooth enough. In the latest scope catalogue I notice that Swarovski claims that the difference in effort is intentional to make it easy to differentiate between the focusing and zoom rings by feel alone.
Overall, it looks to me like Swarovski has, once again, come up with some very desirable new products. Even if the modular feature (which doesn’t interest me at all) is ignored, this specimen of the 95mm ATX is the most optically capable spotting scope I’ve seen thanks to its large aperture, low aberrations, high resolution and a wide angle zoom eyepiece with (almost) enough magnification to show the full resolving power.
When star tested all three of the objective modules proved to be very well corrected for spherical aberration, probably around 1/6 wave. In my experience that’s considerably better than the average expensive spotting scope specimen. In fact it’s close to cherry territory, which I wouldn’t expect from three randomly selected samples. The 85mm modules showed a little more chromatic aberration in out of focus diffraction patterns, which fits logically with their slightly lower focal ratio.
There were some minor optical defects in each of the objective modules. All were slightly comatic and the 95mm also showed some astigmatism and pinching. None of the defects appeared to be associated with the prism modules. Each objective showed the same defects regardless of which prism it was matched with.
Since they were pretty mild and the spherical correction was good the defects didn’t appear to have much effect on the resolving power. The 95mm could resolve the same element on the USAF chart as the Astro-Physics Stowaway though not as cleanly. I wasn’t able to easily move the scopes for a more precise measurement, but I would estimate that this particular 95mm’s resolution falls between 1.25-1.3 arc seconds. Both 85’s resolved one element larger, about 1.4-1.45 arc seconds. These are very good figures for spotting scopes. The 95 has the best raw resolution I’ve measured for a birding scope although it’s no better per mm of aperture than the best Kowa 883 I’ve seen. A 95mm module this good without any astigmatism would probably do a little better.
I didn’t have time to test any eyepiece characteristics, but I found the new zoom very comfortable to use, with none of the blackout problems I’ve experience with the 25-50x Swarovski zoom. The zoom ring was a bit harder to turn than the focusing ring, but its motion is smooth enough. In the latest scope catalogue I notice that Swarovski claims that the difference in effort is intentional to make it easy to differentiate between the focusing and zoom rings by feel alone.
Overall, it looks to me like Swarovski has, once again, come up with some very desirable new products. Even if the modular feature (which doesn’t interest me at all) is ignored, this specimen of the 95mm ATX is the most optically capable spotting scope I’ve seen thanks to its large aperture, low aberrations, high resolution and a wide angle zoom eyepiece with (almost) enough magnification to show the full resolving power.