Requesting PI processing tips on this M31...

[jusasi]

I'm practicing this fine art of processing at the moment and yesterday I captured a sample set of frames from my balcony, inside light polluted city center. Took them with 2x2 binning since I wanted to get some decent amount of material to work with in the tight time window I had. The result was a bit disappointing but I'd still like to see what can be salvaged of this little endeavor. I'm hoping to get some processing tips with PixInsight.

Here's a quick peek of what I've got:

This is after combining the LRGB masters and the output of STF.

As you can see there's a lot of work to get this look somewhat nice and flat. I'm not sure how to get rid of the background lightness, and that light bulge on the left between M31 and M110 - I've tried Dynamic Background Extraction but there always seems to be the problem that the edge between the light and dark space on the left gets exaggerated so that instead of getting a nicer, darker background that I had hoped to get, I get a lighter background with the left corners lightened to the same brightness as the right side, and a dark area, like this:

I'm wondering if this material can be salvaged or is it going to be a futile attempt to get something out of this. I guess it's at least perfect for practice...

Any tips are welcome!

Also, I've attached the master frames to this post if you want to take a look at them and experiment with them by yourself.

 

m31-master-frames.zip

[nucdoc]

I will have a look at your data, it would be better for you to upload the unstreched masters however

Mark

[jusasi]

3 hours ago, nucdoc said:

I will have a look at your data, it would be better for you to upload the unstreched masters however

Mark

Thanks! Although I'm suspecting there's not much that can be done. I suspect the light areas are a reflection of some light.

I'm not sure what you mean by unstretched masters - these are the master frames, calibrated with biases, darks and flats. What do you need?

[wimvb]

In order to process your image, we would need the stacked but otherwise unprocessed master light image that you get after calibration and stacking.

Since you have PixInsight, I suggest that you test the following process steps:

1. after stacking, crop the image using DynamicCrop. Make sure that all edges are trimmed so that no stacking artefacts remain.

2. apply DBE (Dynamic Background Extraction). Place some samples away from stars and galaxy. Use Subtraction as correction method

After these steps, your image should have an evenly coloured background

3. create a preview that only contains background, no stars or galaxy

4. use Background Neutralization to neutralise the background, with the preview as reference

These steps should result in an even background with no obvious colour

 

Good luck