Intruments: Konus Vista 80mm f/5

It's a Konus Vista model, but is exactly the same of Orion Short Tube and Celestron FirstScope 80. I dissuade anyone to use it for deepsky imaging because the corrected field is very little, about 20 mm diameter: in the borders of 24x36 film the stars are horrible. The cause is field curvature, so you must pay attention to focus in the center of the field, if you don't want a ring of focused stars with in the middle defocussed stars...
For the low-power visual observation is almost good, only some cromatic aberration, big but not too much for a f/5 refractor. An artificial star test showed the non existence of a focus point because of cromatic aberration, and a very big astigmatism.

Intra-extra focal images of Konus Vista, and the image at focus: note the very big astigmatism that cause the inexistence of Airy disks, it shows a sort of cross. Philips Vesta Pro webcam with 5x barlow.

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