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Dob men don 't drift align!

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#1 cheapersleeper

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Posted 18 October 2012 - 01:50 PM

Doing some Jupiter imaging with my 12" ATM dob and my ATM EQ Platform. I am working at about 3000mm effective focal length so the better the tracking the easier it is. Since it is webcam vid, it is forgiving of mistakes as long as the planet is on the chip.

Unfortunately, I need to drift align to get it as good as it can be. I have studiously avoided tracking since 1976, though, and am a bit baffled. With my Newt and Telrad, it is super counter intuitive.

I turn off the drive to make sure I have that orientation right while I tweak my speed but I am having a devil of a time getting my head straight o North and South and what to do to make the drift stop!!

Anyone have an easy approach to this that even a Dob and Telrad guy can use?

Regards,
Brad

#2 Lee Jay

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Posted 18 October 2012 - 04:18 PM

I can't imagine a reason you'd need to drift align for that. Heck, you could polar align on Polaris and it should work out fine for planetary imaging. I've done it at 3,800mm with a webcam. 3 minutes is no problem. Periodic error is a bigger problem than drift due to inaccurate polar alignment.

#3 Dwight J

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Posted 18 October 2012 - 04:32 PM

To determine north for instance, look in the eyepiece and nudge the tube up. The stars will move in the north direction while you are watching. If you are using a Poncet type of equatorial table you will need to fine tune your polar alignment for tracking at the very high magnifications used in planetary imaging.

#4 cheapersleeper

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Posted 18 October 2012 - 05:13 PM

Lee,

Are you using a platform? If so, made by whom? My thrown together platform moves the image around a big but keeps a planet on the chip for long while. Even so, it appears to have some North/South drift going on. It would be nice if I could work that out of there.

Dwight,

Thanks for your comments. I suspect I could learn to use a reticle eyepiece at the beginning of a session and orient the crosshair to help me sort it out. Having spent decades 90 degrees from my object and upside down, I get dang confused at times.

Thanks,
Brad

Thanks,
Brad

#5 Lee Jay

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Posted 18 October 2012 - 06:28 PM

No, I'm using a fork. But the polar alignment shouldn't matter much over 2-3 minutes. If it drifts a bit, bump it once. Certainly a multi-hour drift align is not necessary. Go half a degree towards Kocab.






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