ICE for M31 Panorama

[JohnSadlerAstro]

Hi,

I want to image M31 (Andromeda Galaxy) but my FOV is just a little too narrow to get the entire galaxy. I need two panels, rotated so the galaxy is horizontal and it should look good. However, I don't have PixInsight. 

ICE lists exposure blending, will it work if I run it on TIFFs straight from stacking, or will there be obvious seams? I'm not really confident the exposure will look identical in the panels. 

This will be my first mosaic, would I be best capturing say 10 frames on each side to start with then work up from there, or should I get lots of one side tonight and then hope for another clear night and use the same settings?

Thanks for looking!  

John

[AKB]

I used ICE for my first (and, so far, only) mosaic, but I did so after stretching, not on the raw stack.

The image quality wasn't great in the first place, as I struggled to match background noise levels, but I was happy enough with the result then.

 

[vlaiv]

I think it would be best to "interleave" frames if you don't have dedicated mosaic software that is capable of normalizing mosaic panels.

If you shoot frames on consecutive night and you opt to do one panel one night and other panel the other night you might end up with two different environments (haze, transparency, humidity, LP levels, seeing, guiding, ...) and it may show on mosaic. For this reason choose to do both panels on both evenings - for example first evening do one panel "pre meridian" and other one "post meridian" (if your target is centered on meridian mid session), or you can do some sort of finer interleaving like 1h one panel, second hour, other, then for third go back to first panel, and for fourth go to second - but this creates problem of exact positioning (need to recenter panels multiple times) - plate solving helps here.

When you stack your panels - choose reference frames for each stack that are as close as possible in time - last frame before switching to other panel, and first frame of other panel to be respective stack reference frames. Use same settings for stacking.

If you find it is difficult to work with ICE - use ImageJ and MosaicSuite - it can create mosaics out of 32bit fits images (so you can mosaic prior to any stretching and processing and process whole mosaic as normal image).

[ollypenrice]

It really is best to combine the linear data then stretch.  We tend to use Registar for this, as in our monster thirty-odd panel Orion. However, ICE is OK. What you might try is giving both panels a gentle, partial stretch and setting the background value (using Levels) to the same value in both then giving them to ICE. It is rare to find a mosaic maker which doesn't need a little creative intervention from the imager. The trick is to think about the data from the software's point of view.

 

Olly