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How to align guide star when using a Newtonian?

Open PHD Guiding Project PHD2 Acquisition Guiding Polar Alignment Deep Sky
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PghAstroDude avatar
PghAstroDude avatar
Hello Folks,

Since I haven’t had a clear sky in what seems like months, my brain tends to wander.

If you are aligning your guide scope with your main telescope and your main scope is a Newt, and Newtonian images are upside down - do you position the reference guide star in PHD2 how it actually appears in your main scope’s FOV, or upside down?

Take for example Polaris, in which I use NINA for 3PPA and I switch to Live View to align my guide scope. To mitigate flexure, which way should the scope be aligned?

I tend to copy how the FOV looks in my main scope in my guider view, but wonder if that’s the right approach.

Thank you!
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Rafał Szwejkowski avatar
Rafał Szwejkowski avatar
You want to point reasonably at the same area as the main scope to minimize any field rotation issues (but you don't need to be super accurate about it).  The orientation of the image doesn't matter at all since guide calibration process takes care of this.

Now flexure is something else and it has to do with the rigidity of the connection between the main tube and the guider.  That's something that you'll have to ascertain empirically - when I had a flexure problem the guiding was outstanding yet all subs had elongated stars.  What's really insidious about flexure is that the connection between the tube and the guider may seem rock solid yet it isn't in some way.  It's almost impossible to diagnose without actually looking at the subs.  Another potential issue is mirror shift but that's telescope specific when it comes to Newtonians.

At first I'd just evaluate subs for potential issues to address if any.  Chances are your setup is working correctly as is.
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