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shortcut to polar alignment?


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I have an eq2 which I am planning to convert to use for widefield photography, the mount has fixed setting circles so I wondered if a quick shortcut to polar alignment would be to set the circles to the position for a known bright star like vega and then adjust the alt az screws until that star is central in the camera view finder.

will this work or am I kidding myself?

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I don't think the setting circles are accurate enough for the job.

I have developed a photographic shortcut for PA of simple EQ mounts of the type used for widefield photography (say,in the tens of mm of focal length).

See details in http://stargazerslounge.com/diy-astronomer/108643-help-me-test-my-polar-alignment-procedure.html#post1477068

Briefly, you take two exposures of the Polaris region, at two RA positions roughly 90 degrees from each other. You study the exposures, identify the stars UMi Alpha (Polaris) and UMi Lambda and jot down their pixel coordinates (that's 8 numbers in all). Feed this into the supplied spreadsheet and out pop the pixel coordinates that Polaris should be in (in either RA position of the mount). Adjust your mount in Alt-Az, taking test exposures until you get it as close as you like. I can easily get PA error down to 6 arcminutes (1/5 of the Full Moon), measured by the spreadsheet.

I will be doing this for my EQ6 too, doesn't hurt to get a number for PA error. It will also verify if the polarscope reticle is set up correctly.

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Ian

Unfortunately, you're kidding yourself! :D

To prove it to yourself, position the scope so that it isn't polar aligned. then follow your procedure and you should still be able to align your mount on Vega, or wherever, using the RA/Dec screws.

Steve

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Yes, I use this method with the main scope, the motor on the eq2 does have an adjustable speed but no speed scale, but thinking about it now i don't think it actually matters, the reason for 2x is that the stars end up pretty close to the starting point after a one minute out, one minute stopped, however if the motor speed is quicker or slower all that happens is the star ends up finishing long or short compared to the start position which could make star id difficult in narrow FOV images but in widefield shouldn't matter much as the whole trail will be visible in the picture....

(or am I kidding myself again?)

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