GSO coma corector

[Imme]

Ok....so who has one of these? They are sold under a couple of different badges/names but essentially are all the same. They come with minimal documentation and there are conflicting focus distances quoted by various people on the net from 70 to 82mm.

Does anyone know the proper backspace dimension?

Bintel website says 80mm (+/- 2mm), another guys is saying 75mm on the dot.

.....and......all people say to measure from the lens to the focal plane....the lens is curved so measurements differ from centre to edge (by about 4mm).....I guess I take it from the centre as that’s where the image sensor is right???

Any advice would be greatly appreciated

[MattT]

https://www.cloudynights.com/topic/462985-setting-up-the-gso-coma-corrector/

Might answer your question...

[Imme]

Thanks Matt.... Thats one of many sites with vared info. Ive decided to split the difference between all the info i could find and gone 77.5mm