PA using guide scope

[MichaelMan]

Hi all, 

I plan to use my DSLR on my main scope and use my guide scope with guide cam for PA.

I'm using AZ GTI in EQ mode, so no polar scope. 

Does my guide scope need to be perfectly aligned with my main scope to have good PA? Or same as for guiding just roughly in the same direction?
Main scope will be WO ZS61, guide scope probably 50mm. 

[StevieDvd]

If you PA using your guidescope then your mount will be aligned (for that session if you setup each time).  Software PA alignment basically does that by using your main scope/camera and platesolving several positions to work out your current PA axis from what it should be.  When guiding the target in your dslr will keep the same offset from your guide star if your PA is good.

[MichaelMan]

Thank you StevieDvd

Just to clarify you say 

"Software PA alignment basically does that by using your main scope/camera and platesolving"
However I plan to be using my guide scope for that as I don't believe my DSLR can be used for this?
Hence my question, does my main scope and guide scope need to be precisely aligned to the same spot?

 

[fifeskies]

I polar align with my guidescope and Sharpcap and it works fine. My main scope and guidescope are aligned together on a side by side mount. Nominally pointing at the same spot but I don't worry about exact alignment between them.

(My guidescope is an ST80 so I get plenty stars)

I do only have a ZWO290mm as my guide camera so the field of view is not large at 0.8 degrees by 0.45 degrees and Sharpcap advises a larger field to get enough stars.

I think I manage to get away with the smaller FOV because my large guider aperture brings out many fainter stars for the software to be able to platesolve properly.

 

 

Edited November 11, 2020 by fifeskies

[MichaelMan]

Thank you Fifeskies

Good point about FOV of camera, i was only taking into consideration the guidescope fov vs the main scope. 

 

[CedricTheBrave]

1 hour ago, MichaelMan said:

Thank you StevieDvd

Just to clarify you say 

"Software PA alignment basically does that by using your main scope/camera and platesolving"
However I plan to be using my guide scope for that as I don't believe my DSLR can be used for this?
Hence my question, does my main scope and guide scope need to be precisely aligned to the same spot?

 

i use my Nikon d7000 or Canon 700d to plate solve and PA no problem

 

[fifeskies]

I did try try the Canon DSLR fix for Sharpcap , and although it did connect and take frames the software always froze on me , so reverted to my guidecam.

[MichaelMan]

36 minutes ago, CedricTheBrave said:

i use my Nikon d7000 or Canon 700d to plate solve and PA no problem

 

Interesting, I will give it a go

 

[StevieDvd]

Just to give an example of the need or lack of need for the guide scope and main scope to be pointing at the same target:

1. For visual if they are both alighend the lager fov lets you find the target easier in the finder scope. Needs both aligned.

2. You want to image a particular target but there is no good star in the fov of the guide scope. Adjust the guidescope to show one and guide on that. Not aligned but intentional and OK.

You will see some of the heavy weight guidescope adapters have adjusters for point 2

And to further answer your question if the guidescope and main scope are not aligned. You can still use the PA routines that take images and platesolve with either scope, the PA process is the relative axis of the mount to a fixed camera view (main or guide).

Hope that helps.

[MichaelMan]

Thank you
This is very helpful