M31, WIP

[tomato]

This is my initial try out of using the mosaic tool in SGP. It is 6 panels of 30 mins L, 10 mins each RGB, taken in a single night, with the Esprit 150, G2-8300 on a Mesu 200.

Despite being shot on a single night I think conditions changed quite a lot as the galaxy arched overhead as despite numerous experiments in APP, I cannot fully eradicate the joins. I have found to date 1st LNC, 10 iterations and 15% MBB gave the best result, if any APP users could point me in the right direction, it would be very much appreciated. My laptop is also flagging when processing images of this size🤪

So I’m posting this monochrome version for now but will attempt more subs on this project (wind and rain currently battering the dome).

Thanks for looking

[assouptro]

Thanks for posting your work so far, I'm afraid I can't help you but as I plan on putting my first APP Mosic together as soon as I can obtain enough data on panel 2  I am watching this with interest 

Have you posted this question in the APP forum? 

Nice image btw It's defintely got potential! I hope you get the help you need

cheers 

Bryan 

[Xplode]

You need evenly illuminated images and all good SNR per panel, without both those you won't be able to create a good quality mosaic.
Your images seems pretty low SNR...there's also some weird patterns? Do yhou dither?

[Laurin Dave]

Looking good, I’d be interested to know if there’s an answer to this.   I’ve found APP mosaic stitching works like magic on narrowband  but have struggled with it because of gradients on RGB (haven’t tried Lum)..  I went back to Pixinsight gradient merge mosaic having first       lightly stretched and removed gradients from each panel..  still far from perfect though.. and have only used the result as the basis for HaR_OiiiG_OiiiB..  

Dave

[assouptro]

3 minutes ago, Xplode said:

You need evenly illuminated images and all good SNR per panel, without both those you won't be able to create a good quality mosaic.
Your images seems pretty low SNR...there's also some weird patterns? Do yhou dither?

Is dithering a benefit or a hinderance to mosaic images? 

Cheers 

Bryan

[tomato]

Thanks for the replies, SGP was dithering in between every sub, not something I normally do. Each panel is currently only 1 hour integration so the SNR won’t be great. I have previously stitched mosaics together in APP with better results than this, I think at least one panel was affected by high cloud, based on the changes observed on the PHD guide star SNR.

[GraemeH]

WIth my recently posted M31 mosaic, I had frames with wildly different background brightnesses due to having some subs ranging from either side of a full moon, through until just after new moon.  For me, APP did a great job of normalising, using 1st order LNC with 5 iterations, but I think the thing that made the biggest difference to the background smoothness was setting MBB to 50%.  Spending a long time in building a model for light pollution removal in APP made a big difference too, trying to follow the guidance from one of Mabula's videos on LP removal.

I'm too new to APP to know how well these settings would apply to a different integration, but I guess it couldn't hurt to try.

Graeme

[Xplode]

You really need 10+ images per filter per panel and at least 3 dithers to remove noise succesfully.
It would be interesting to take a look at your uncalibrated images if possible? Maybe you could share 1-2 panels with calibration images?

Edited December 7, 2019 by Xplode

[tomato]

I'll see about posting a couple of panels, in the meantime this is what I have with the LRGB data, smooth it is not, clearly more subs needed!

[Allinthehead]

Did you use flats?

I find it best to stack each panel separately. Then stitch together. This saves a huge amount of time.

If they're evenly illuminated then 1st or 2nd degree with 4 or 5 iterations. If that doesn't work i then try 4/5 degree with the same amount of iterations and so on.

[tomato]

Thanks for the tip. Yes, I’ve been reading Mabula’s How to posts on Mosaics and I was using the wrong workflow, I’m currently trying to combine some old data with these panels, but with varying success.

I do take flats, but I have noticed that since setting up the scope in the permanent observatory, I am getting some odd shaped histograms on them. There appears to be a light gradient running from top to bottom on the sensor, whereas the illumination was quite uniform previously. I realise the purpose of the flats is to eliminate these type of gradients, but I am puzzled why this has now appeared.

[tomato]

So, more subs taken on the outer arms, unfortunately under less than ideal conditions. To keep the panel integration roughly the same I used some images of the central region taken in 2018, these were on a good night so I have really struggled to get a neutral background, you can see the differences on the second image. I have resorted to some very heavy handed methods to get an even background and in so doing have lost some of the sharpness and luminosity that was present in some of the better panel integrations.

I just need to capture decent data, the 150 is pulling in some good detail I think, each panel is (on average) 72 mins of integration