1st go at M51

[Zummerzet_Leveller]

C & C welcome.  My first attempt at M51.  Taken with my SW 150P with coma corrector and my Canon 100D (Baader Mod).

Nearly 5hrs of 240 second lights, stacked in DSS and processed in Gimp.

[JemC]

I think you have done really well with this for a 1st attempt 👍

[Zummerzet_Leveller]

11 minutes ago, JemC said:

I think you have done really well with this for a 1st attempt 👍

Thanks.  I couldn't get more red to show, I think I need a bigger bucket or more exposure time.

[peter shah]

lovely rendition

[Adreneline]

50 minutes ago, Zummerzet_Leveller said:

I couldn't get more red to show, I think I need a bigger bucket or more exposure time.

Hi Jody.

Hope you don't mind but I had a play with your image which is great and better than my first attempt at M51 by a country mile.

On my monitor the image had a distinct magenta cast so I removed that and then increased the colour saturation a little. I've cropped the galaxy out and there is not shortage of colour.

Bearing in mind I was only working with a low-res 8 bit version I am sure there is more to be had from your 16 bit original. The blue regions in the spiral arms is showing up really well.

Hope you don't mnd.

Adrian

 

[Zummerzet_Leveller]

8 hours ago, Adreneline said:

Hi Jody.

Hope you don't mind but I had a play with your image which is great and better than my first attempt at M51 by a country mile.

On my monitor the image had a distinct magenta cast so I removed that and then increased the colour saturation a little. I've cropped the galaxy out and there is not shortage of colour.

Bearing in mind I was only working with a low-res 8 bit version I am sure there is more to be had from your 16 bit original. The blue regions in the spiral arms is showing up really well.

Hope you don't mnd.

Adrian

 

Thanks Adrian, I don't mind at all.

I think I may have overcooked the magenta in the shadows to control the green!  Just need to get the balance right.  Did you apply a global saturation or to individual colours?  I was cautious about pushing the saturation too far.

Jody

[Zummerzet_Leveller]

9 hours ago, peter shah said:

lovely rendition

Thanks Peter.

[Adreneline]

9 minutes ago, Zummerzet_Leveller said:

Did you apply a global saturation or to individual colours?  I was cautious about pushing the saturation too far.

Hi Jody,

I used PixInsight to remove the magenta. I 'inverted' the image and removed the green with the SCNR process and then re-inverted the image; it must be possible to do the equivalent in GIMP but I don't know how. Forgot to mention I then reduced the noise just a little across the whole image (I use a free, old copy of Nik Dfine2); I would normally create a mask and only reduce noise in the background. I then lifted the saturation on the whole image as well just a little in Affinity. If I had been processing my own image I might have played around with masks again to be more selective with the galaxy and the stars, which I now tend to remove, process the main target and then put back separately processed. Getting colour balance right is really difficult and I struggle loads to achieve. I also find that if I process on my PC laptop (rarely) and then look at the image on my MacBook Pro the colours are way different; if I plug an external monitor into the PC laptop they are different again!

Adrian

 

[Zummerzet_Leveller]

8 hours ago, Adreneline said:

Hi Jody,

I used PixInsight to remove the magenta. I 'inverted' the image and removed the green with the SCNR process and then re-inverted the image; it must be possible to do the equivalent in GIMP but I don't know how. Forgot to mention I then reduced the noise just a little across the whole image (I use a free, old copy of Nik Dfine2); I would normally create a mask and only reduce noise in the background. I then lifted the saturation on the whole image as well just a little in Affinity. If I had been processing my own image I might have played around with masks again to be more selective with the galaxy and the stars, which I now tend to remove, process the main target and then put back separately processed. Getting colour balance right is really difficult and I struggle loads to achieve. I also find that if I process on my PC laptop (rarely) and then look at the image on my MacBook Pro the colours are way different; if I plug an external monitor into the PC laptop they are different again!

Adrian

 

Thanks for the details Adrian.  I'll see what I can do to emulate the process in the freeware.  I know Siril has a green removal tool, might try that out.  I've got Starnet++ installed (on my work computer 🤫) so will keep tinkering.  I have two monitors and the the image looks different in both.

[Zummerzet_Leveller]

22 hours ago, Adreneline said:

Hi Jody.

Hope you don't mind but I had a play with your image which is great and better than my first attempt at M51 by a country mile.

On my monitor the image had a distinct magenta cast so I removed that and then increased the colour saturation a little. I've cropped the galaxy out and there is not shortage of colour.

Bearing in mind I was only working with a low-res 8 bit version I am sure there is more to be had from your 16 bit original. The blue regions in the spiral arms is showing up really well.

Hope you don't mnd.

Adrian

 

Did a reprocess but think I need to get better at blending the mask in.

[Adreneline]

Hi Jody.

This really is a cracking image of M51 but I have to say there is still a magenta cast on my screen. If I do the PI trick again and remove green from the inverted image then M51 looks amazing. It really needs a GIMP expert to throw in their two-penny-worth because I have no idea how do this magenta removal.

I took your image into Affinity and used the colour picker tool to scan/sample around the background. I many places the R and B values exceed the G value indicating a magenta cast which I presume prevails on the whole image.

I hope you don't feel I am being picky or critical but there is a seriously nice M51 lurking in your data.

I am sorry I cannot be of more help.

Adrian

[Zummerzet_Leveller]

15 minutes ago, Adreneline said:

Hi Jody.

This really is a cracking image of M51 but I have to say there is still a magenta cast on my screen. If I do the PI trick again and remove green from the inverted image then M51 looks amazing. It really needs a GIMP expert to throw in their two-penny-worth because I have no idea how do this magenta removal.

I took your image into Affinity and used the colour picker tool to scan/sample around the background. I many places the R and B values exceed the G value indicating a magenta cast which I presume prevails on the whole image.

I hope you don't feel I am being picky or critical but there is a seriously nice M51 lurking in your data.

I am sorry I cannot be of more help.

Adrian

It's all great Adrian.  I appreciate all your help and insight it steers me in the right direction to improve and challenge myself, I picked up the SW150p as my first scope in July last year and I've learned so much already.  I'll get on to Google and see whether there is any way of tweaking.  I did a colour inversion and lowered the greens in curves but must not be getting rid of those causing the cast.  At least as things are at the moment I have plenty of spare time to learn and improve. 

[Adreneline]

6 minutes ago, Zummerzet_Leveller said:

I did a colour inversion and lowered the greens in curves but must not be getting rid of those causing the cast.

I'm sure this is not easy. I'm sure you know magenta is an extra-spectral colour we see that does not appear on the EM spectrum because it is made up of blue and red - (255,0,255) - opposite ends of the spectrum. Magenta is the complementary colour to Green hence the "invert and remove green" but exactly how SCNR in PixInsight does it I have no idea. As to doing the same thing with Curves in Affinity (or GIMP) I have no idea.

I was advised on this forum to aim to get background space to be around R,G,B : 23,23,23 - not too black in other words.

Good luck and sorry again I can't be of more help.

Adrian

[Zummerzet_Leveller]

On 11/03/2021 at 23:46, Adreneline said:

I'm sure this is not easy. I'm sure you know magenta is an extra-spectral colour we see that does not appear on the EM spectrum because it is made up of blue and red - (255,0,255) - opposite ends of the spectrum. Magenta is the complementary colour to Green hence the "invert and remove green" but exactly how SCNR in PixInsight does it I have no idea. As to doing the same thing with Curves in Affinity (or GIMP) I have no idea.

I was advised on this forum to aim to get background space to be around R,G,B : 23,23,23 - not too black in other words.

Good luck and sorry again I can't be of more help.

Adrian

@Adreneline I've managed to get some time to re-work the data can you have a look and see if this is still showing a magenta hue on your monitor? 

Edited March 31, 2021 by Zummerzet_Leveller

[Adreneline]

Hi Jody!

You'll be pleased to know I can't see a trace of magenta on my monitor. I loaded your image into Affinity and sampled the background to examine the RGB levels. As you can see from the four sample points the RGB levels are all pretty similar (a good thing) and most importantly the Red and Blue are not significantly higher values than the Green.

One thing I was advised to do was to try not to clip the black point and it was a good idea to try to get the background to be around the R:G:B = 23:23:23 or thereabouts. You can see from the image above that the histogram is pretty much up against the left hand axis; it's a good idea to have a bit of space to the left of the histogram. The advantage of not clipping the black point is that quit often you find feint nebulosity is revealed. I know many though prefer the 'blackness of space" look and the subject of the image appearing to hang in the darkness. It's a totally personal preference thing I think - whatever works for you - but I pass on the advice so you can decide.

It's a great image - one to be proud of!

HTH

Adrian

P.S. I have to say I tend to go for around the 18:18:18 mark as per my attached image of M51 taken some time ago - and processed some time ago!

 

M51+aa.tiff

[Zummerzet_Leveller]

@Adreneline Perfect, thanks for the feedback and I am pretty pleased with how it turned out, a lot of trial and error...  I think my star reduction technique might be a little to blame for the black clipping, I think I need to pull it back a bit.  Great to hear my workflow is beginning to get the right colour balance.  I've recently upgraded to a 27" LED backlit monitor which seems to have better colour calibration compared to my 6 year old 21" LCD monitor so that may have helped a bit.  I'll see if I can find a way to do RGB sampling in GIMP, I'm sure it's possible.

I have also just forked out for my Canon 6D to be astromodded and it arrives tomorrow so looking forward to trying the full frame, bigger light wells and lower noise over my modded 100d.  It won't be long before I get a dedicated astro-cam I'm sure, then it will be a choice of mono or OSC and a whimpering bank account!

[Adreneline]

8 minutes ago, Zummerzet_Leveller said:

It won't be long before I get a dedicated astro-cam I'm sure, then it will be a choice of mono or OSC and a whimpering bank account!

Or both! If you get one you'll wish you had the other

I look forward to seeing the results of the modded 6D.

Good luck.

Adrian