Processing M33. Help!

[Messy Hair 101]

Hi, I wonder if anyone could help me, I'm pulling my hair out!

I've spent a couple of nights gathering LRGB data on the the Triangulum Galaxy, about 2 hours per channel with a bit more for luminance. I feel like my setup is sorted and I can acquire data relatively easily now, it's the processing that's the issue! Also need to work on my calibration (there are some circles on here which must be dust spots and residual amp glow still visible when you stretch but anyway...).

Below was an early attempt at processing and since then, reading more and more tutorials, my attempts have got progressively worse! I'm wondering if someone would like to have a play with the TIFFs from DSS to see if they can do better and if so, give me an idea of workflow and any pointers.

These were 3 minute exposures stacked in DSS, taken with an ASI 183MM Pro and Astronomik LRGB filters with a Skywatcher ED80.

Luminance https://drive.google.com/file/d/1A5lafKfB5mBaSAl_1Y-cvxEK0kAODmvv/view?usp=sharing

Red https://drive.google.com/file/d/1lYSCMxz4BARrERCnjnVUWQrQsn9V_o6n/view?usp=sharing

Green https://drive.google.com/file/d/161ozMFioeQ9trK3f73sP2gLjyuyfvwNv/view?usp=sharing

Blue https://drive.google.com/file/d/1zCLO_fmSlMnVGwmmfn67tgLZ6q1x9jet/view?usp=sharing

 

[johngm]

Hi messy,

I've downloaded the individual files and I will see what I can tweak out of them. It will be tomorrow thought as I have to be up at 4.30am for work.

John

[Messy Hair 101]

Much appreciated John. Thank you.

[alacant]

Hi

Lovely shot.

I think that with correctly matched dark and flat frames and with each channel containing only one set of data -R contains only R etc.-  you'd be able to process the whole of the frame without having to spend time correcting in software. Also best to keep the camera attached at the same angle, thus avoiding edge artefacts which have to be cropped.

 

 

 

 

 

 

 

 

 

 

 

 

Here's an in-your-face-shouldn't-be-here lrgb thrash in Siril. You got some great detail:)

Edited October 1, 2020 by alacant

[Messy Hair 101]

Wonderful thanks for that. I think I know part of the issue.

I did two imaging runs a couple of days apart. I also did the second with an l pro attached which might cause issues?

I also clearly need to work on my darks, dark flats and flats as they haven't worked as well as they should. I didn't take bias frames as I heard they can cause issues.

One question. When you say the red channel should only have red in it, how do I ensure that happens? I've used Astronomik LRGB filters and unless I mixed up some frames, not sure what else I would do.

[alacant]

13 minutes ago, Messy Hair 101 said:

red channel should only have red

It's probably not important and I don't use dss so I don't know what it does but when I open your .tif stacks in Siril, I expect to get 4 separate monochrome images. In fact I get RGB data from each.

If I stack red frames in Siril, I get a monochrome image containing only red data. Maybe dss doesn't do that...

But the main issue I think is to get the calibration frames in order. Do that and you'll find it a lot easier to process.

Cheers

 

[johngm]

Hi Messy,

As Alacant said, you definitely need calibration frames to get any great improvement. I have stretched each individual channel, and your dust motes are on the luminance channel. If your imaging train is still set up the same, i suggest you take flats for each channel, and you definitely need  darks to get rid of the amp glow. This is the best i could do.

[Messy Hair 101]

Wow so the data is there, just need to work on calibration and perhaps stacking.

I did take darks, flats and flat darks. Flats for each channel but I will start again I think as something has clearly gone wrong.

Thanks both for all your efforts. It has helped to restore my faith and given me something to work towards 

[johngm]

7 minutes ago, Messy Hair 101 said:

Wow so the data is there, just need to work on calibration and perhaps stacking.

I did take darks, flats and flat darks. Flats for each channel but I will start again I think as something has clearly gone wrong.

Thanks both for all your efforts. It has helped to restore my faith and given me something to work towards 

Yes Mate, you defiantly have good data, just like you said, you need to work on your calibration, especially darks with a 183 sensor, they are renowned for there starburst amp glow. And with practice, your processing will definitely get better, 

John

[Messy Hair 101]

Quick update. I restacked my LRGB data using Auto Adaptive Weighted Average and that seems to have removed the dust and amp glow. Below is a very quick and dirty, after two rums and a bear re-process to show the principle works.

[ollypenrice]

There is no need for bias with a CMOS camera and you do need to take darks for flats (AKA flat darks) matched to your flats. (With CCD a master bias can replace a flat dark.)

16 hours ago, Messy Hair 101 said:

Quick update. I restacked my LRGB data using Auto Adaptive Weighted Average and that seems to have removed the dust and amp glow. Below is a very quick and dirty, after two rums and a bear re-process to show the principle works.

That is just massively black clipped so all the faint signal, whether wanted or not, has been discarded. This is not the way to fight gradients, vignetting, amp glow or light pollution. Here's your histogram:

A healthy histogram must have some low flat line to the left of the histogram peak: 

Olly

 

 

[billhinge]

Thanks for  the  play, best  I could  do

 

[Messy Hair 101]

On 04/10/2020 at 16:02, ollypenrice said:

There is no need for bias with a CMOS camera and you do need to take darks for flats (AKA flat darks) matched to your flats. (With CCD a master bias can replace a flat dark.)

That is just massively black clipped so all the faint signal, whether wanted or not, has been discarded. This is not the way to fight gradients, vignetting, amp glow or light pollution. Here's your histogram:

 

Yes I guess what I was trying to show was that the amp glow and dust from the first images was gone. Maybe this overstretched luminance file will demonstrate it better. I probably shouldn't have had a go at processing late after a few drinks!

Below are the updated channels with improved calibration if anyone wants to have another crack.

Luminance https://drive.google.com/file/d/1fLVXtgmaVdCqibMsnAebDmJswKq3wJUf/view?usp=sharing

Red https://drive.google.com/file/d/1E79FZ7_DNPeU9zS_1cXsiSUhTNQaYOk9/view?usp=sharing

Green https://drive.google.com/file/d/1HHBlrlsyhR0xa_KNQHk7c66eg9jgn1Di/view?usp=sharing

Blue https://drive.google.com/file/d/1LsPqZmv5Fq803NzMJoVNhHp6-MvFpmxO/view?usp=sharing

[ollypenrice]

9 minutes ago, Messy Hair 101 said:

Yes I guess what I was trying to show was that the amp glow and dust from the first images was gone. Maybe this overstretched luminance file will demonstrate it better. I probably shouldn't have had a go at processing late after a few drinks!

Below are the updated channels with improved calibration if anyone wants to have another crack.

Luminance https://drive.google.com/file/d/1fLVXtgmaVdCqibMsnAebDmJswKq3wJUf/view?usp=sharing

Red https://drive.google.com/file/d/1E79FZ7_DNPeU9zS_1cXsiSUhTNQaYOk9/view?usp=sharing

Green https://drive.google.com/file/d/1HHBlrlsyhR0xa_KNQHk7c66eg9jgn1Di/view?usp=sharing

Blue https://drive.google.com/file/d/1LsPqZmv5Fq803NzMJoVNhHp6-MvFpmxO/view?usp=sharing

'Yes I guess what I was trying to show was that the amp glow and dust from the first images was gone.'  Yes, but so was about half of the image!

My standard advice is always, and without exception, look at the image.  So, if you look at the image above, what do you see? What I see is a decent M33 sitting in a dark pool which is darkest at the bottom.  Let's measure it and see if this is correct. Below I've measured the brightness values of the background in different parts of the image an placed the value on the picture:

This confirms what we see when we look at it. But how do we fix it? Well, one thing's for sure: there is nothing we can do to the whole image that will fix the irregular illumination of the field. Whatever we do is going to have to deal with different parts of the image in different ways. This will require a software designed to look for uneven illumination, AKA gradients and correct them. Pixinsight's DBE, Gradient Xterminator, Astro Pixel Processor, Astro Art and others have such tools.

But you cannot fix it by black clipping in levels.

Olly

[Messy Hair 101]

1 hour ago, ollypenrice said:

But you cannot fix it by black clipping in levels.

I know. I just bodged that image and shouldn't have really tried with it. Uneven illumination is still an issue but with Gradient Xterminator applied, I feel like I'm making some progress. I'm just glad I could get the calibration better.

It's a learning process and there's a lot of trial and error, especially jumping to mono from a DSLR. I'm finding processing quite hard so was just curious what others could make of the data to see if it was the data or my processing. I think I know where the issue lies!

[Viktiste]

Had a go at this with Pixinsight, just for my own exercise.

Your L, R,G,B images are all containing RGB colors? Was this taken with a mono or color camera?

Anyway, here is what I managed with my current Pixinsight skills:

[Viktiste]

And attempt #2

 

Edited October 6, 2020 by Viktiste

[Messy Hair 101]

Thanks Viktiste. They look pretty good. The data should be separate channels of LRGB but as was hypothesized above, I wonder if it's displaying like that because of Photoshop perhaps or DSS when you put them into Pixinsight? The shots were taken with a mono camera, ASI 183MM Pro.

[alacant]

Hi

I think you perhaps need to do the flat frames again. As it stands ATM, you may have better luck without applying flat frames. 

Get the calibration frames and the single colour rgb stacks correct and you'll have a much easier time processing.

Cheers

 

[Messy Hair 101]

3 hours ago, alacant said:

Get the calibration frames and the single colour rgb stacks correct and you'll have a much easier time processing.

Yes I will have another go at the flats - or even try without and see what that does. Can you expand on the single colour RGB stacks point? A few people have commented on there being RGB channels on mono images. I stacked each channel seperately and saved a Tiff from DSS, then opened in Photoshop. I then stretch them a little and paste them into the RGB channels of a new RGB document in PS. Anything I'm doing wrong there?

[Scooot]

On 04/10/2020 at 16:02, ollypenrice said:

There is no need for bias with a CMOS camera and you do need to take darks for flats (AKA flat darks) matched to your flats. (With CCD a master bias can replace a flat dark.)

That is just massively black clipped so all the faint signal, whether wanted or not, has been discarded. This is not the way to fight gradients, vignetting, amp glow or light pollution. Here's your histogram:

A healthy histogram must have some low flat line to the left of the histogram peak: 

Olly

 

 

“There is no need for bias with a CMOS camera and you do need to take darks for flats (AKA flat darks) matched to your flats.”

Hi Olly, is that the case with a DSLR or are you just referring to dedicated Astro CMOS cameras.?

[alacant]

3 hours ago, Messy Hair 101 said:

saved a Tiff from DSS

Hi

See my comment here. We need someone who has stacked red only files in DSS to confirm that red only stacks produce rgb images. 

Cheers

[Viktiste]

19 hours ago, Messy Hair 101 said:

Thanks Viktiste. They look pretty good. The data should be separate channels of LRGB but as was hypothesized above, I wonder if it's displaying like that because of Photoshop perhaps or DSS when you put them into Pixinsight? The shots were taken with a mono camera, ASI 183MM Pro.

I don't think this has anything to do with Pixinsight, it just loads  the image in whatever format it is.

A superzoom of e.g. the L image clearly shows it is a color image. The same goes for the R, G and B images,  the ones I downloaded from here:

On 05/10/2020 at 20:04, Messy Hair 101 said:

Yes I guess what I was trying to show was that the amp glow and dust from the first images was gone. Maybe this overstretched luminance file will demonstrate it better. I probably shouldn't have had a go at processing late after a few drinks!

Below are the updated channels with improved calibration if anyone wants to have another crack.

Luminance https://drive.google.com/file/d/1fLVXtgmaVdCqibMsnAebDmJswKq3wJUf/view?usp=sharing

Red https://drive.google.com/file/d/1E79FZ7_DNPeU9zS_1cXsiSUhTNQaYOk9/view?usp=sharing

Green https://drive.google.com/file/d/1HHBlrlsyhR0xa_KNQHk7c66eg9jgn1Di/view?usp=sharing

Blue https://drive.google.com/file/d/1LsPqZmv5Fq803NzMJoVNhHp6-MvFpmxO/view?usp=sharing

 

[Messy Hair 101]

8 minutes ago, Viktiste said:

A superzoom of e.g. the L image clearly shows it is a color image.

I think I need to go back to stacking school before I try to process! I'm going to try restacking and changing background calibration as I have a feeling it is working on the assumption these are colour lights and not mono. I will report back with findings.

[Nigella Bryant]

Best I could get.