Problem with focusing

[jasig62]

I have an Orion Starshoot Auto-Guider attached to a Skywatcher Startravel 80 scope as a a guide-scope.

I use it with PHD2 guiding software but the problem is I fall short of a proper focus on the inward travel of the focuser. Tried removing the diagonal to get more inwards travel but you cannot get a focus on either the camera or the eyepiece without the diagonal inserted.

Any advice would be appreciated.

[Merlin66]

On the ST-80 if you remove the diagonal you need a 60mm spacer in the focuser to get back close to focus.....

This should get you close....

[ollypenrice]

Don't use a diagonal for guiding. I use the ST80 as well and have extended the backfocus by using a de-lensed Barlow which I had kicking about.

The distance from the back of the focuser body on the main OTA (at the point where the draw tube emerges from it) to the back of the adapter needs to be about 15cm. I've just measured mine. If you don't have an old Barlow body you'll need to order an extender of the right length.

Olly

Edit, I crossed with Ken but our figures agree.

Edited April 24, 2020 by ollypenrice

[Skipper Billy]

This was my ST80 with a QHY5 - it required an 80mm extender to reach ficus - you can see it in the middle of this photo.

 

[jasig62]

Thanks guys for all your good advice. I will give it a try.

[jasig62]

Tried de-lensed barlow. Success !! Distance is around 60cm so all good. Many thanks for your help.