Auto Meridian Flips!


Hello all,
Have a general question regarding when SGP performs an Auto Meridian Flip…

I use a 10" newt on an NEQ6 Pro and a QHY8L. I always use the manual rotator option so SGP can get me to
rotate my camera to match the angle I choose in the F & M wizard. Also, I have the ±180 degree option set in
the sequencers Target Settings for rotation.

The QHY8L always produces some amp glow in the upper left hand corner of the Lights which needs to be sorted with Dark subtraction though. I chose M81 & M82 last time I was able to get out, the first image had M81 to the left of the image and M82 to the right with the familiar amp glow in the top left.

When SGP needed to do the flip it done it all fine except one issue. It didn’t get me to rotate the camera by 180 degree’s after the flip. When the next image came in M81 and M82 were on opposite sides and by the end of the run I had a set of images half of which needed to be flipped by 180 degree’s. What I noticed then is that I had amp glow in both the opposing corners once the images after the flip were rotated by 180 degree’s…

Now I know that using the ±180 option avoids having to take 2 different sets of Flats and a rotation wont be performed after a flip but when I do the Darks, these will only have amp glow in one corner, whereas, due to the flip and no 180 degree camera rotation,I have ‘X’ amount of amp glow in 2 opposing corners on the Lights ! ! !

‘IF’ I had to resort to the ‘Always’ option and take 2 different sets of Flats, how on earth would I manage this, haven’t got a clue to be completely honest !

Anyone got any advice on how best to approach this problem ???

Many Thanks


You don’t have to rotate the camera, leave that job to the alignment software when you are preprocessing your frames.


Hi Paul,
I am completely new here, but think I have a simple answer for you. If you for one moment disregard what is actually on the image,(ie which galaxy is where) and think of just the image as it came out of your camera. Your amp glow or hot pixel column etc will always be in the same place ( ie top left ) Now before you register and align the images you will be doing the calibration steps (Subtracting Darks / Flats & Bias) which will remove the amp glow from the top left corner of all images. It is only after this when aligning the images that those taken after the flip will be rotated (ie the now “not there anymore” amp glow section will be rotated to the bottom right. So long story short, as John said… the stacking software will take care of this for you, you just go about getting as many subs as you can :smile:

Leslie Rose



SO when the alignment / stacking part happens, as well as wiggling images about to get them aligned it will also rotate images a full 180 degree’s & wiggle them too if need be ???

Is that what we are saying :smiley:

<-- So hopes Pixinsight does this too !



That is the way a “proper” alignment software works. In Pixinsight, the subs can be very far off from each other, both in terms of rotation and distortion, and it will still align them. If you are working on subs from different telescopes it is a good idea to generate a star map from the catalog and align your images to that instead of a reference sub. That way, projection gets perfect and you definitely know that your image is correct.

I have even done mosaics by simply aligning all the subs to a star map that covers the entire mosaic, and then stacking the subs in one go for the whole mosaic. I consider this experimental practice at this time, but it is nice to not have to do any work at all in terms of stitching :slight_smile: