M33 60s v 300s - 300s too far?

[scitmon]

I recently completed an imaging session of M33, with sub lengths of 300s.  I was hoping this data would greatly add to my previous attempt on M33 where I only did 60s sub lengths.  However after numerious processing attempts in PixInsight I am very dissapointed in the result.  Obviously the stars are bloated, but it all appears to be a blury mess.  Could it be that I was out of focus or have I just pushed the sub length of my Canon 700d too far?

39 x 300s:

47 x 60s:

Edited January 1, 2020 by scitmon

[Whistlin Bob]

We're you guiding? Poor tracking could cause blurring.

Is your camera modified, and if so were you using any sort of filter? Bloated stars can result from no IR cut if the filter has been completely removed.

You could improve this significantly in the processing by using the Starnet PI extension to remove the stars, process only for the galaxy and then add the stars back in with Pixelmath with much less of a stretch on them.

Edited January 2, 2020 by Whistlin Bob
Autocarrot

[scitmon]

Thank you for the reply, yes I was guiding and my camera is modified.  I was using the IDAS D2 Light Pollution Suppression Filter on the 300s and not on the 60s. 

I wasn't too concerned about the stars as I could blend in 60s ones, I was looking for more detail and colour in the galaxy, which I don't really understand why there isn't after adding over 3 hours of exposure?  Still much to learn in this hobby!

[PeterCPC]

I normally use 300s exposure with my Canon with no ill effects. I use APP for processing. For instance this was taken with my Canon 1200d with 300s exposures for about 2.4 hours.

Peter

[tooth_dr]

Focus or poor conditions on the night?

[scitmon]

Yes possibly, certainly sounds like something other than the sub length.  I think an autofocusser and SGPro (so I can schedule refocussing through the night) is my next step to improving my pictures.

[scitmon]

1 hour ago, PeterCPC said:

I normally use 300s exposure with my Canon with no ill effects. I use APP for processing. For instance this was taken with my Canon 1200d with 300s exposures for about 2.4 hours.

Peter

That is some excellent noise control there, was it mostly processed out?  With Pixinsight?

[PeterCPC]

3 minutes ago, scitmon said:

That is some excellent noise control there, was it mostly processed out?  With Pixinsight?

I don't use Pixinsight any more. I use Astropixel Processor (APP) for stacking and some post processing but the majority of post processing is done with Affinity Photo with some plug ins like AstroFlat Pro. I found Pixinsight to be too complex.

Peter

[wimvb]

Tracking issues and atmospheric disturbances become more obvious with longer exposure times. The stars in both your images show that they were not overexposed, you've got good star colour. The 300 s image also starts to show Ha regions in the galaxy. Even though the IDAS LP filter is a good one, it will affect the colour in your image. Furthermore, DSLRs suffer from chromatic noise (colour mottle). All this has to be remedied in post processing. And I think that it is quite straightforward to do this.

This is after some adjustments to your 60 s image. Working on the original xisf file would yield better results of course.

[scitmon]

Wow looks much better, may I ask what you did there?

You say the filter will effect colour... as in colour balance which can be corrected in post processing or am I actually blocking colour?  If thats the case I might reconsider using it.

I will happily provide the xisf files if you want to show me what more can be done.  Here are the links to them in my OneDrive:

https://1drv.ms/u/s!Al9nr2n1J94MnGFYTyu23WkEK6_B?e=psoK8E

https://1drv.ms/u/s!Al9nr2n1J94MnGBPbZCdlwtGGY2k?e=qMesMa

 

[wimvb]

4 minutes ago, scitmon said:

Wow looks much better, may I ask what you did there?

• DBE
• Background neutralization 
• Mmt noise reduction on chrominance
• SCNR green
• Colour saturation
• Contrast adjustments (curves) 

Are the files still linear? It's easier to work on them if they are. Will look at them tomorrow. 

[wimvb]

7 minutes ago, scitmon said:

the filter will effect colour... as in colour balance which can be corrected in post processing or am I actually blocking colour?  If thats the case I might reconsider using it.

Both to some degree. All lp filters will cause a loss on colour. But IDAS are imo best in keeping colour. If you need a lp filter, by all means, keep this one. As you say, a change in colour will be corrected in post processing.

And as for best exposure time, just make sure that the exposure histogram on your Canon is a little removed from the left efge of the display. Longer exposures are not needed, you gain more by increasing the number of exposures than their duration. 

[wimvb]

20 minutes ago, scitmon said:

I will happily provide the xisf files if you want to show me what more can be done.  Here are the links to them in my OneDrive:

https://1drv.ms/u/s!Al9nr2n1J94MnGFYTyu23WkEK6_B?e=psoK8E

https://1drv.ms/u/s!Al9nr2n1J94MnGBPbZCdlwtGGY2k?e=qMesMa

 

Btw, the links don't work for me. I can't access the files.

[scitmon]

  

26 minutes ago, wimvb said:

• DBE
• Background neutralization 
• Mmt noise reduction on chrominance
• SCNR green
• Colour saturation
• Contrast adjustments (curves) 

Are the files still linear? It's easier to work on them if they are. Will look at them tomorrow. 

I did do all those on my image, obviously not as well as you!  I'm going through the Inside PixInsight book as I go.

It would be great to know what my data can achieve in the right hands.

10 minutes ago, wimvb said:

Btw, the links don't work for me. I can't access the files.

Sorry I was replacing them with the linear images:

https://1drv.ms/u/s!Al9nr2n1J94MnGKt6CE7ovlKyhmg?e=KFCdOR

https://1drv.ms/u/s!Al9nr2n1J94MnGM4YEUs8qqSje73?e=lMd6YU

All I've done is calibrated and integrated with flats and bias, (no darks and dithered).

 

Edited January 3, 2020 by scitmon

[scitmon]

20 minutes ago, wimvb said:

If you need a lp filter, by all means, keep this one. As you say, a change in colour will be corrected in post processing.

I do wonder now, I am class 5 Bortle and as you can see I can easily get 60s without one.   I will have to look into it further.

[wimvb]

I downloaded two files: light_master.xisf and lightmaster 30s.xisf. The latter is probably underexposed. After DBE and colour calibration, the brightest stars have a normalised pixelvalue of 0.78 (approx.). I think you can safely double the exposure time. Underexposed stars are good if you want to keep colour down to their core, as you would when photographing clusters. But if you want fainter detail in a nebula or galaxy, it may be better to overexpose the brightest stars and get more signal. The alternative is to gather many more subs to get the noise down.

10 hours ago, scitmon said:

I do wonder now, I am class 5 Bortle and as you can see I can easily get 60s without one.   I will have to look into it further.

At Bortle 5 you should definitely try to shoot without the LP filter. It will depend very much on what kind of light pollution you have and at which part of the sky relative to the pollution source you are aiming.

[wimvb]

This is your lightmaster_30s image after PixInsight

Process:

RGB:

• Crop to remove stacking artefacts
• DBE
• Colour calibration (background neutralization and PCC)
• Extraction of Luminance to be processed separately
• noise reduction (chrominance only)
• Masked stretch
• Arcsinh stretch
• Histogram adjustments
• Blurring
• LRGB combination
• Adjustment of star profiles

L:

• Noise reduction
• DBE to correct a persistent gradient
• Histogram and Curves Transformation
• HDR compression (slightly)
• Curves adjustment
• LRGB combination

The data is a bit noisy, but if this is just 47 x 30 seconds, that's understandable. My advice: try to collect as much data as you can, at least 3 - 4 hours if feasible. This will improve the signal to noise ratio and make processing easier.

[wimvb]

Light_master.xisf has better defined Ha regions and less noise. But it is more difficult to get the colours right. Both PCC and standard colour calibration result in a too red/magenta galaxy core. Also, since the stars are over exposed, colour calibration will give false colours in the star cores that need to be repaired.

http://pixinsight.com.ar/en/info/processing-examples/28/maskedstretch-stars-sores.html

Probably the best exposure is between 60 s and 300 s.

[scitmon]

5 hours ago, wimvb said:

This is your lightmaster_30s image after PixInsight

Process:

RGB:

• Crop to remove stacking artefacts
• DBE
• Colour calibration (background neutralization and PCC)
• Extraction of Luminance to be processed separately
• noise reduction (chrominance only)
• Masked stretch
• Arcsinh stretch
• Histogram adjustments
• Blurring
• LRGB combination
• Adjustment of star profiles

L:

• Noise reduction
• DBE to correct a persistent gradient
• Histogram and Curves Transformation
• HDR compression (slightly)
• Curves adjustment
• LRGB combination

The data is a bit noisy, but if this is just 47 x 30 seconds, that's understandable. My advice: try to collect as much data as you can, at least 3 - 4 hours if feasible. This will improve the signal to noise ratio and make processing easier.

Well this is very impressive, I clearly have much to learn and practice.  I think perhaps the main difference between my approach and yours was the seperate processing of luminance, I will give that a go.

Its good to know my data has more potential than I thought.  I should point out that it was 47 x 60s, I named the file incorrectly sorry.

 

57 minutes ago, wimvb said:

Light_master.xisf has better defined Ha regions and less noise. But it is more difficult to get the colours right. Both PCC and standard colour calibration result in a too red/magenta galaxy core. Also, since the stars are over exposed, colour calibration will give false colours in the star cores that need to be repaired.

http://pixinsight.com.ar/en/info/processing-examples/28/maskedstretch-stars-sores.html

Probably the best exposure is between 60 s and 300 s.

 

So it does seem that 300s might have been too much.   It didn't occur to me that overexposed stars could adversely effect the colour of the image overall to such a degree.  I learnt a lot from your input, thank you very much!