Combining different equipments and setting them up for optimal astronomy photos are complicated but fun to many astro-photographers. Last month, Piotr Maliński did some homework with a bunch of kits, including DMK 21AF04.AS astronomy camera, and sent us a review afterwards.

The paragraphs in blue are quotes from his e-mail:

I've made some interesting pictures recently. First of all I wanted to test a 1,25″ filter threaded 0,5 focal reducer with DMK 21AF04.AS (to get wider field). As I have f/5 newtonian the standard DMK C/CS nose was to long and it would reduce the image too much (unfocusable. It would be good for telescopes with focal ratio 9 and more). So I've got short C/CS nose (15 mm, which gives 30-33mm reducer to CCD distance and not 60 mm as with standard nose) and low profile 1.25″ eyepiece holder:

The results are quite interesting. From f/5 newtonian I've got about f/2,75 Newtonian nearly at the end of back focus. Imaging Sun I could make the mosaic with just two images (DMK 21AF04.AS, focal reducer, green RGB filter, false yellow color):

Coma is getting noticeable at such extremely fast focal ratio (no coma corrector used). With a coma corrector it should look much better. Such fast focal ratio also give the possibility to catch very faint objects. On f/5 setup I could get Saturn moonHyperion at 2 sec exposures barely. With the focal reducer I can get nearly 16 mag star close to big bright Saturn:

Many Thank to Piotr for his details review!