Every change is one or more new frustrations

[AstroRookie]

Hello,

I'm getting desperate over this hobby (but I refuse to give up); with every change new problems set in. I purchased a SVBONY SV106 (60mm - 240mm) guide scope to replace a 80mm - 400mm scope, I was using as a guide scope which was installed on the Orion 8 tube rings. I replaced the finder scope with the guide scope.

First issue balancing but that one I sorted out. Then I tried to focus the ASI120MM with the new guide scope. For the old  one (80x400) , I needed 2 extensions (in fact the extensions are low cost barlows from which I removed the plastic lens) to get focus. To align the new guide scope, I used a 17mm eyepiece and that went ok while pointing at some far away trees. But I could not get the ASI120MM focused on the same trees, not with PHD2 nor with Firecapture; I turned the gain way down, but with or without extensions, no focus. As bad weather is (again) setting in and the scope is permanently outside I had to stop trying.

So I take on this break to get some assistance.  Anybody any advice on this, for

AstroRookie

[JonCarleton]

I use the SV106 as my guide scope and have been happy with it.  Sometimes I even do wide-field images with it (see attached).  It does want to focus a lot farther away than earthbound objects, however.  I am using a SV305 camera on it, and have the extension tube set at 2 + 3 marks.  My "guess" for your ASI120MM is that it will need a setting slightly less, based on my experience with switching out my ASI with the SV305 in the main scope.  The SV305 seems to take a bit longer tube. 

I will say that the fine focus is REALLY "tichy" on the SV106.  A tiny adjustment makes a significant focus difference.  The good news is that once you finally get it set and tighten the set screws, it rarely needs any adjustment for guiding purposes.

 

Edited December 13, 2020 by JonCarleton

[Budgie1]

I use the same setup with the SV106 and ASI120MM Mini attached.

The camera has the longer spacer attached, which you can just see in the photos below. Hopefully this will give you an idea of where the backfocus is for yours.  

[AstroRookie]

Thanks for the help,  I'll have a look - next weekend probably, they announce dry weather during the day.

AstroRookie

[AstroRookie]

On 13/12/2020 at 16:54, Budgie1 said:

I use the same setup with the SV106 and ASI120MM Mini attached.

The camera has the longer spacer attached, which you can just see in the photos below. Hopefully this will give you an idea of where the backfocus is for yours.  

Budgie1,

you're my hero! I removed the extension (I needed for the previous guidescope), "copied" the settings as shown in your picture and bingo! Stars all over place! A great thanks, from

AstroRookie