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Polar Alignment idea


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Lacking an illuminated cross eyepiece when I set up my scope lately I have found using my camera, my laptop and two pieces of string blu-tacked to my screen I can get a great alignment done in half the time I used to, and with much greater accuracy.

The issue I still have is polar aligning, getting that perfect is tedious and frustrating, and I just struggle with drift alignment.  Last night while pondering this I came up with an idea that I would like feedback on.  I assume it has been tried / done and as such people could tell me the pitfalls.

Simply enough, thanks to http://www.12dstring.me.uk/fov.htm I know that my camera FOV is 56.34' x 37.56'

Using Stellarium or similar I can create an image of the zenith in those dimensions, and print it out to the same size as my laptop screen.

Stick a piece of clear plastic over this, mark out all visible stars.

Then simply when I set up my scope, I connect up the camera, stick my see through plastic onto my laptop screen, and use that for polar alignment.

Obviously it won't be prefect, and will still need tweaking (plastic will need rotating, scales will be slightly out etc) but as an alternative to crawling around on my knees trying to use a polar scope it seems a reasonable alternative.

Has anyone tried anything similar?

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The only issues I see with this is the movement of the earth.

- You print off what the stars should look like at 6pm

- Stick it onto your monitor and start taking a picture at 6:10pm

That's 10min of movement which, depending on focal length, could make it way off where you expect the stars to be.

I could be wrong but that's my first thought?

Phil

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The only issues I see with this is the movement of the earth.

- You print off what the stars should look like at 6pm

- Stick it onto your monitor and start taking a picture at 6:10pm

That's 10min of movement which, depending on focal length, could make it way off where you expect the stars to be.

I could be wrong but that's my first thought?

Phil

Wouldn't the only movement be rotation though?  In which case it would just be a matter of spinning the image slighlty.

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Perhaps? Uou're also assuming that your telescope is going to be pointing perfectly in the same direction as the mount? If it's out a small amount then your PA will also be out a small amount? :(

Ah!  And that is they key item that my brain was skipping over.  I knew I was missing something obvious.

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Hi, 

can't you use some software like APT or Backyard EOS to do it like with an eyepiece?

I make this way with APT:

center the star in the small rectangle in live view mode, then i zoom in all the way and center it in the crosshairs and do the needed adjustments.

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