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CG5ASGT: 4min tracking at 100mm -> trails.

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#26 Patrick

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Posted 16 September 2009 - 09:14 AM

Niels,

If I understand your program correctly, in order to see no star trailing in an image, the "Pixel Curve Size" would have to be less than 1. Is that correct?

Patrick

#27 amateur

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Posted 16 September 2009 - 10:09 AM

100% correct.

For example: PE error=0, Polar Alignment error=zero, rate=1.0000 should always result in a perfect exposure without trailing:
PE curve size=0 x 0 pixels

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#28 Patrick

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Posted 16 September 2009 - 10:28 AM

Or like this?

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#29 amateur

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Posted 16 September 2009 - 12:16 PM

I expect that limited trailing like this will be invisible (hidden by limited resolution of the lense, clipping of bright stars and seeing blur).

#30 Patrick

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Posted 16 September 2009 - 01:55 PM

I expect that limited trailing like this will be invisible (hidden by limited resolution of the lense, clipping of bright stars and seeing blur).



That's the heart of what I'm trying to get at. If the PE (measured in 'pixels') is less than 1 pixel, then there can't be any trailing recorded on the sensor because the pixel next to it doesn't get hit with any photons. So, I should be able to adjust my exposure parameter and look at the Pixel Curve Size value and tell when my exposure will be too long. Or...adjust one of the other parameters if I can. For instance, I might be better off with a camera with larger pixels or it may show that no matter what I do with the mount, I'll need to autoguide.

I think that's what most of the people doing astrophotography are concerned with when it comes to PE...how long of an exposure can I take with the equipment I have.

Niels, thanks for creating your PE calculator!

Patrick






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