Phd2 declination confusion

Discussion of using SharpCap for Deep Sky Imaging
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psy1280
Posts: 208
Joined: Wed Oct 24, 2018 4:52 pm

Phd2 declination confusion

#1

Post by psy1280 »

I apologize if this repeats other threads, I've just started using phd2 (I'm trying to begin that long journey toward AP) and the other night I encountered some weird, pulses in declination. I suspect these are backlash issues, however, I'm not sure how to approach my next attempt at guiding. Any suggestions will be most appreciated. I blindly did a bit of trial-and-error with the phd2 values... to no avail.

I'm using a Celestron 8" SCT

AVX mount

According to SharpCap's polar align, I had an excellent alignment

I was imaging the Pinwheel galaxy that had just crossed the meridian, however, being a rookie, I didn't know how to do a meridian flip, so I just keep imaging without doing any flip.(I had used Skysafari for go-to alignment)

The Pinwheel was close to the Zenith

Since this happened I've bundled all my loose cables

I did not "east" balance the OTA

Thanks to all,
Joe

declination issues.jpg
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oopfan
Posts: 1321
Joined: Sat Jul 08, 2017 2:37 pm
Location: New York
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Re: Phd2 declination confusion

#2

Post by oopfan »

Joe,

I don't know how much help I can be with declination issues, but I use PHD2 to guide in Right Ascension. I have Declination disabled. I rely on the accuracy of my polar alignment using SharpCap. I can expose for as long as 600 seconds with only a couple arc-seconds of declination error.

I don't know what exposures you are using, but I suspect it is shorter than mine by a wide amount. You may not even need declination guiding. Try disabling it to see what you get.

Just curious, did you run the Guiding Assistant? Each new session after PA, I run Calibration while pointing the scope at the sky between the equator and +20 deg declination (usually +18 deg). And then I slew to the DSO, and run the Guiding Assistant for about 5 minutes. PHD2 will suggest optimal settings that you should apply by clicking the Apply button. I believe that the Guiding Assistant also analyzes your declination backlash.

Brian
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