Imaging through a flip

msoutham
16 Dec, 2016 17:18
I currently use Backyard EOS for image capture and PHD to guide. Up until now I have started capture sessions when a target has just passed the meridian or stop imaging just before to avoid a mount flip in the middle of a session. If however, a target will cross the meridian in the middle of a session this poses a couple of problems and I'm wondering 2 things.

1. Can Pixinsight's Batch Preprocessing script handle some images one way up and some upside down?
2. Will PHD figure out that it's calibration settings need to be flipped when it sees stars moving in the wrong direction after the flip?
whwang
17 Dec, 2016 04:49
It's not rare for me to have a meridian flip in the middle of a imaging session.  Sometimes I stack the images before/after the flip separately, and sometimes I just stack them all together.  I don't remember a case where PI failed to stack those 180deg rotated images with the others, as long as the telescope pointing is still good.  I do remember case of failures when there are both large pointing offset and large rotation, in combination of image distortion from the optics.

For PHD, someone may have more accurate answers, but I saw options related to the meridian flip in PHD2, meaning that it can do something to it.  However, someone (or something) have to tell PHD2 it had been flipped.  I am not sure how a user can tell PHD2 the flip had happened, but ASCOM may tell PHD2 such things.  Personally, I always redo the calibration after the meridian flip.  The different weight distribution after the flip may cause an overall tracking pattern change.  A re-calibration generally improves tracking accuracy in my case.

Cheers,
Wei-Hao
adamland
17 Dec, 2016 17:54
Yes, and yes (as long as your mounts ASCOM driver reports what side the mount is on)
widotje
18 Dec, 2016 08:06
There is an option which I used in PhD that lets you flip your calibration data. It works very well for me.
msoutham
23 Dec, 2016 00:36
Thank you all for your advice. I was hoping to have the calibration flip happen automatically. I guess the only way to see if it will is to try. Great to know that PI will handle the flip without issue. Thanks again.
astrofarm
02 Nov, 2017 21:26
PI Star Alignment takes care of it, although you may end up with some borders on the master that need to be cropped off.
stinerjohn
02 Nov, 2017 23:38
Sequence Generator Pro will do the flip for you. It also plays well with PHD.
HillTop
03 Nov, 2017 13:00
+1 for SGP handling meridian flips well. I didn't think BYEOS could do automated flips, but I honestly don't know for sure. I've integrated in DSS and PI with flipped images without issue. To my understanding it's only a problem if you rotate the camera after the flip - then the calibration subs need to match each pier side. Be sure to experiment or check with others for the correct PHD settings for flipped calibration - it varies with different mounts.
 
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