Another stupid question. .

[goldblade1983]

Hi

About to acquire an st80 second hand. The seller also has 3 point rings for sale which I'm considering.

I'm also looking at cnc rings.

St 80 will be piggybacked on wo gt81.

Can I ask a question about aligning both scopes using cnc rings so they're both pointing at same star.

How do you do it if there's no pins to alter the way the st80 is pointing?

Presumably 3 point may be better to allow alterations for choosing guide starts anyway?

Cheers

Brian

[ChrisLX200]

With an ST80 you won't need to search around for a suitable guidestar - not if using a decent guidecam like a QHY5 etc.,). Problem with 3-point rings are they don't support the scope as rigedly as either full rings or even simply bolting the tripod foot to the main scope. It doesn't really matter if the FOV is not _exactly_ the same either.

ChrisH

[goldblade1983]

Ah yes I can see that the may be 'scope' for flexure. Will go for cnc. Cheers

[steppenwolf]

As Chris says, the wide FOV of the ST80 makes it unnecessary for it to be perfectly aligned with the imaging telescope for guiding. I would not really recommend the adjustable mounting that you suggest as it will lead to differential flexure! Mount it as solidly as you can, irrespective of how accurately it mimics the pointing of the WO GT-81.

[Tinker1947]

I use a ST-80 as a guide scope and as said your never be short of a guide star, i mount my in the 3 point ring system and after a bit of twiddling the star in the centre of the ST-80 is also in the centre of the DSLR Sensor, it might be a bit further down the slippy AP road for you but when i use PHD the Star/DSO  in the centre of the PHD is right in the middle of the Camera Sensor so there no back and forth just centre it in PHD so there's no need to run any other software to get the object centred, i can see it on the PHD screen, 1 good reason for using them, although i use EQMod and Stellarium to slew the scope ect you could just use PHD.....