The new UAG II is entirely a visual product, only intended for use with the Maxbright II binocular viewer. It is not intended to be used on its own for monocular observation, but for easy, comfotable use with the binoviewer
It is likewise NOT intended to work in front of a 2" star diagonal but only directly in front of the binocular viewer.
Absolutely any telecompressor causes "aperture loss". But not because it would crop the incoming beam, but because it does what the name says - it "compresses" the beam to become smaller in diameter. So, you get a smaller, brighter image.
At the distance of 121 mm the fully illuminatred field circle would be 18 mm and this is mercilessly visible in a CMOS-camera. The light fall off is so slow though that the human eye hardly notices the vignetting until the image circle has reached a diameter of ~23 mm. This is the reason why it is a joy to use with the binocular viewer and 1.25" eyepieces (which have field stop diameters of less that 26mm, and many binoviewers have even smaller prisms), but NOT with 2" eyepieces. Many eyepieces btw. work with this "vignetting trick"to -virtually- sharpen the outermost edge of the field. Check the web for TV-Plossel eyepieces of the first generations which used this "design feature" already 30 years ago.
Vignetting of UAG II and AG II are the same. The AG II was designed around the same time as the TV-Plossels. This was the time of emulsion films hundreds of times less sensitive than modern CMOS-cameras, and when 2" eyepieces did cost a fortune. Please do not try to pursue your project using the AG-lens principle for applications it was not intended for.
For a larger monocular true field of view, we'd recommend a 2" eyepiece like the Hyperion 36mm (the field stop diameter and thus the true field of view is comparable to thos of 2" eyepieces with even longer focal lengths, but the apparent field of view is much larger). If you aim for a brighter image with 1.25" eyepieces, then the UAG (in the standard version, which offers more options for configuration) is the better choice.
Answer by: Baader Web Team (Admin) on Mar 30, 2021 1:36:00 PM