Off axis guiding

[david maitland]

A question, learning to image with an off axis guider, if I have both cameras focused and par focal on an object 200m away in daylight, would it follow they would be the same when imaging your DSOs?

[ChrisEll]

Yes, the back focus is the same to imaging sensor and to guiding sensor. However you will need to adjust the drawtube focus common to both cameras but not each camera separately (hope I've explained that clearly).

[RayD]

39 minutes ago, david maitland said:

A question, learning to image with an off axis guider, if I have both cameras focused and par focal on an object 200m away in daylight, would it follow they would be the same when imaging your DSOs?

Yes it should be near enough.  200m isn't far, so you may need to re-focus the main camera, which naturally will change the focus on both, but if you are using PHD2 for guiding then you don't want your guide star perfectly focused anyway, so this would be ideal.

[david maitland]

24 minutes ago, ChrisEll said:

Yes, the back focus is the same to imaging sensor and to guiding sensor. However you will need to adjust the drawtube focus common to both cameras but not each camera separately (hope I've explained that clearly).

Yeah I think I understand, you mean both cameras parfocal while on OAG?

[ChrisEll]

LOL I'm confused now  The distance between the OAG and objective can change to get focus on star, no need to change anything behind the OAG (both cams are already parfocused).

[ollypenrice]

Like Ray, I think it will be near enough. Just give it a try. You can, if you have to, tweak the OAG focus slightly but perfect focus is not required for guiding. As Ray says, slightly soft focus is recommended. (By Craig Stark, creator of PHD.)

Olly