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ZEQ25 and guiding - Newb in Trouble!

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#1 noexperience

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Posted 29 October 2013 - 08:23 PM

Just starting out in astrophotography and purchased a ZEQ25 for my ES 80ED. I watched Astronewb's You Tube video on tuning and with that help I removed a lot of slop from both axes.
Last Sunday I went out and captured data from M13. With the tuned up mount I was getting very flat graphs in PHD using a SS Magnificent Mini. I had some time after collecting this data and was feeling really good about the round stars I was seeing so I decided to start collecting some data on M31. I slewed to M31 and it was right in the middle of the frame so I started to track. The DEC continued with it's flat line behavior but the RA went off the chart almost immediately. I stopped the guide and restartd and it went off the chart in the other direction. I rebooted the SS and shut off PHD and restarted it, but had the same result. Returned the mount to home, shut it off, did another align, slewed to M31 (right in the viewfinder) but the RA was still going crazy. I was low on battery so I did not get a chance to return to M13 to see if tracking was better.

Can anyone provide any help in diagnosing this issue? Sorry I have no graphs, my notebook died before I had a chance to get this saved.

Thanks in advance! :bow:

#2 orlyandico

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Posted 29 October 2013 - 08:32 PM

1) when you did the PHD calibration, was it on the opposite side of the mount as M31? (e.g. you were pointing west when you calibrated, then when you slewed to M31 you were now pointing east)

2) what was the declination of the star when you calibrated? was it very different from the declination of M31?

Generally, if you meridian-flip, you have to invert the calibration data (there is an option in PHD for this). And, if you slew someplace "far" (in declination) from the calibration star, but remain on the same side of the meridian, you have to recalibrate.

Most paranoid solution is to recalibrate after every long slew.

#3 noexperience

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Posted 29 October 2013 - 08:43 PM

WOW! Thanks for the quick response. I think you hit it on the head. M13 (when I did the first calibration) was in the west and low on the horizon. M31 was is in the east and much higher (later in the evening.) And no, I did not recalibrate. Thanks for the advice, can't wait to get out now and see what I learned is the answer (I bet it is.) Unfortunately it looks like clouds for the immediate future.

Thanks

#4 Stelios

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Posted 30 October 2013 - 11:27 AM

Most paranoid solution is to recalibrate after every long slew.


Paranoid or not, I like it. That's what I've been doing the last few times after experiencing several disasters similar to the poster's.

Part of the issue may be distribution of the weight (balance). Part may be mount sloppiness. In any case, it takes no more than 10 mins to recalibrate, well worth it to not ruin a 1 to 2-hr imaging session.






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