Focus of OAG

[Glider]

I'm just trying to remember what I've forgotten from my University Optics course!

If I focus my guide camera and imaging camera on the fence at the end of my garden today will they still both be in focus together on DSO tonight?

Will I only need to fine adjust the focus on the OTA tonight?

Should I get the cameras in focus together on something further away, say the horizon?

[Merlin66]

If they are in focus...they're in focus; doesn't matter where the object is.

The "combo" AOG/ camera should be fixed....under the stars you may have to slightly refocus the "Combo", not the individual cameras.

HTH

[Glider]

Phew, just what I wanted to hear, thanks.

[angusb1]

Cheers, I'd been wondering about this myself

[steppenwolf]

I always set OAGs up during the day aimed at an object in the distance (a fence will be fine) and all will be well on the night sky too.

[ollypenrice]

I always set OAGs up during the day aimed at an object in the distance (a fence will be fine) and all will be well on the night sky too.

This is done having first focused the main scope on the fence, I assume? I've never used one. (Well, I've used a fence but not an OAG...)

Olly

[steppenwolf]

This is done having first focused the main scope on the fence, I assume?

That is the easiest way of doing it as these devices normally have a focus method on the guide camera port rather than the imaging camera port.

[Merlin66]

yes, focus the imaging camera - on the fence then move the guide camera in the OAG body to get a good focus - on part of the fence. If you run out of INWARD movement for the guide camera, then you need to add a spacer between the OAG guide body and the imaging camera.