Celestron EdgeHD autofocus

[kosborn]

Hi all,

I'm wondering what people are using for autofocus solutions with a Celestron EdgeHD. An external focusing solution like the Esatto seems like a good solution because it allows you to engage the mirror lock, but I'm not sure if the few fractions of millimetres of autofocus focus adjustment adversely affects the back focus and star profiles. What is the tolerance of back focus with the EdgeHD setup?

Thanks, Kevin

p.s. Yes, I have focal length fever :P

[Dennis]

Hi Kevin

This website:

https://www.innovationsforesight.com/support/celestron-edgehd-back-focus-tolerance/

provides some useful backfocus information using a C11 Edge HD and suggests that variations measured in several millimetres do not appear to make much difference.

Dennis.

[kosborn]

Hi Dennis, thanks for that, much appreciated. It certainly suggest an external autofocuser would work well.

[Dennis]

Hi Kevin

Here is my set up with the C9.25 Edge HD, ESATTO 2" Focuser and ARCO Rotator giving me the recommended 146mm back focus.

Dennis.

[gregmc]

I have a focuser on the image train but I calculated the backfocus around mid travel. Then set the focuser at mid value, then focus using the mirror focuser as best you can, lock the mirror and then fine focus with the focuser in front of the camera from then on.

[kosborn]

Thanks guys. It looks like an external autofocuser is the way to go. In fact it was the 2" Esatto that I had my eye on!