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Guiding and Polar Alignment


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Hello,

These might be basic questions, but I just want to confirm my understanding:

I've got a ASTROTECH AT-65Q telescope piggybacked on a Skywatcher Refractor (focal length 1000mm, D = 120mm).

1) If I should polar align the ASTROTECH AT-65Q, would the Skywatcher be polar aligned automatically and vice versa ?

2) I know I can guide the Skywatcher telescope using the ASTROTECH AT-65Q, but using the same setup (ASTROTECH AT-65Q being piggybacked) could I guide the ASTROTECH AT 65Q with the Skywatcher ?

Thank you.

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Neither. Polar alignment is conducted to align your mount's axis with the pole not the scopes. Then the mount will track your scopes according to that PA.

If you piggy back something then no it is unlikely to be perfectly aligned with the main scope but that can be an advantage if it is not too far out.

2) in theory, yes but why?

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So then if I understand correctly it does not really matter which one of the telescopes you use to polar align your mount ? The polar alignment of the mount would valid more or less for both ?

I would like to do long exposure imaging through my ASTROTECH AT-65Q also since it provides different optics and field of view, without using focal reducers or barlow lenses. That's the reason for my second question.

Thank you.

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So then if I understand correctly it does not really matter which one of the telescopes you use to polar align your mount ? The polar alignment of the mount would valid more or less for both ?

I would like to do long exposure imaging through my ASTROTECH AT-65Q also since it provides different optics and field of view, without using focal reducers or barlow lenses. That's the reason for my second question.

Thank you.

You don't use the scopes to polar align.

You should use your polar scope to align the mount.

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Here's what I do:

Crude alignment, scope towards North, center Polaris through Polar scope, main and finder scope (to align all my scopes, however, if they're not totally aligned, that shouldn't be a problem, because you align the axes),

then, I put my cam in the scope ( maybe a bit early, but that way I get alignment, focusing, and having to touch the scope out of the way). At this point, Polaris is in the center of the Polar scope, main and finder scope.

Then, I move Polaris to its correct position (visual crude) with the AZ and Lat. screws on the mount (the position I get from the alignment steps, or a star chart, keeping in mind that directions are most likely inverted, or turned around 180 degrees).

Then a 3 star alignment (to eliminate cone error, and for precision, some do this alignment after drift alignment). On the 2nd, or third star, I put the guidecam into the finder scope.

Then drift alignment, beginning in AZ, then dec. (2 iterations, as a correction in one axis may create an error in the other [if the mount is not level).

I have used both guide scope and main scope for drift alignment. W/ the main scope, due to the larger magnification, the alignment can be more precise). If there is a large error, though, than sometimes the guider is "better" in that the larger FOV is easier to work with.

Then recenter on the last star I used for drift alignment (for accuracy in that part of the sky when I look for faint objects).

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  • 2 weeks later...

Here's what I do:

Crude alignment, scope towards North, center Polaris through Polar scope, main and finder scope (to align all my scopes, however, if they're not totally aligned, that shouldn't be a problem, because you align the axes),

then, I put my cam in the scope ( maybe a bit early, but that way I get alignment, focusing, and having to touch the scope out of the way). At this point, Polaris is in the center of the Polar scope, main and finder scope.

Then, I move Polaris to its correct position (visual crude) with the AZ and Lat. screws on the mount (the position I get from the alignment steps, or a star chart, keeping in mind that directions are most likely inverted, or turned around 180 degrees).

Then a 3 star alignment (to eliminate cone error, and for precision, some do this alignment after drift alignment). On the 2nd, or third star, I put the guidecam into the finder scope.

Then drift alignment, beginning in AZ, then dec. (2 iterations, as a correction in one axis may create an error in the other [if the mount is not level).

I have used both guide scope and main scope for drift alignment. W/ the main scope, due to the larger magnification, the alignment can be more precise). If there is a large error, though, than sometimes the guider is "better" in that the larger FOV is easier to work with.

Then recenter on the last star I used for drift alignment (for accuracy in that part of the sky when I look for faint objects).

This is your problem. The method is incorrect. You should only use your main scopes for polar alignment by using the drift method. What you are trying to do here, as I understand it, is use your main scopes as polarscopes and this will never work. They will always have cone error and getting the RA and Dec axes perfectly aligned with the mount's polar axis will, likewise, never be possible.

I would use the polarscope at first and then do a quick drift using one of the scopes. This is good;  http://www.andysshotglass.com/DriftAlignment.html

Olly

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Agree with Olly.

I set my kit up as if i'm about to image, so that everything is ready and balanced and good to go. I then use EQmod to polar align through the polar alignment scope (making sure that has been collimated so is as accurate as HUMANly possible). Once there I connect everything up and turn it all on, setting my CCD to start it's cooling procedure etc.

Opening PHD2 I use the drift align wizard on that to gain a more accurate alignment using the Az and Alt knobs on the mount. Once I'm happy that I'm 'close enough' I head inside the house and control everything from there with a glass of Gin and Tonic! :)

Obviously if you need to manually focus then this will need to be done before heading inside.

Phil

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