Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

Rodd

M51 LRGB

Recommended Posts

The acquisition of this data went surprisingly well (I thought).   The image is a work in progress and contains about 13 hours of data in 10 min subs with C11Edge at F7 with SBIG STT-8300.  I got a new flat illuminated panel (Alnitak flatman) that really improved calibration.  So that went better than expected as well.  The stacks seem to look good and I was anxious to combine them into a RGB image.  That's when the disappointment started.  To me, the image looks blurry, smudgy somehow, as if it was colored by someone using dull crayons instead of sharp pencils. 

Focus seemed to be good, with FWHM values between 2.0 and 2.6.  Eccentricity values are surprisingly around .4-.5 (with the Televue I am lucky to get better than .6)

Guiding seemed to work well, with rms errors betweem .2 and .3 pixels (my pixel scale is .57 arcsec/pix, so guide errors were between .1 and .2 arcsec.

Do I need more data?  I only have 8 10 min lum subs, so that seems low.   Color seems sufficient.  

Any suggestions/comments welcomed

Thanks--Rodd

 

 

LRGB-2.thumb.jpg.48474de03f7e22055c84dbf2ddd2bbbb.jpg

  • Like 21

Share this post


Link to post
Share on other sites

 

22 minutes ago, Singlin said:

I really like the core.

Thanks--It is the one thing I suppose that came out OK. 

 

 

Share this post


Link to post
Share on other sites
57 minutes ago, simmo39 said:

Thats a Wow image! nice!

Thanks Simmo39

Share this post


Link to post
Share on other sites
9 minutes ago, laudropb said:

Very nice image.

Thanks Laudropb

Share this post


Link to post
Share on other sites
3 hours ago, Rodd said:

To me, the image looks blurry, smudgy somehow, as if it was colored by someone using dull crayons instead of sharp pencils. 

To me, it looks like a great image :)

It does look a little soft in the background; almost as if it's had a guassian blur applied with the detail protected. However, at screen size it looks amazing. I love the saturation.

Share this post


Link to post
Share on other sites
52 minutes ago, Filroden said:

To me, it looks like a great image :)

It does look a little soft in the background; almost as if it's had a guassian blur applied with the detail protected. However, at screen size it looks amazing. I love the saturation.

Thanks Ken.  I am wondering if the "softness" could be the result of the sensor not being 46.5mm from the back lens ( the specified distance for this scope).  To me the high signal areas look soft as well--almost like there is a film in front of the image.  The distance is most likely correct though, because narrowband data does not look soft.  I don't know-LRGB is frustrating.

Rodd

Share this post


Link to post
Share on other sites

Wonderful image - I love the colours.

I can't help with the cause of the softness; you have covered off the problems that I would normally look for - seeing being the main culprit in my images.

In any case, I think this is a lovely image.  It is somewhat sharper seen full size and the slight softness in the galaxy arms seems to give the image a feeling of depth - like looking into a river whirlpool.

Share this post


Link to post
Share on other sites

Great image. A tad oversaturated, imo. If the individual r, g and b frames are good, you can combine them with the lum data to make a synthetic lum image. Combine this with the rgb data.

Good luck, and thanks for sharing

Share this post


Link to post
Share on other sites
3 hours ago, wimvb said:

Great image. A tad oversaturated, imo. If the individual r, g and b frames are good, you can combine them with the lum data to make a synthetic lum image. Combine this with the rgb data.

Good luck, and thanks for sharing

Thanks Wim--I tried a synthetic Lum made will all subs (80!) and a lum made with just the Lum subs (only 8) and the one with the 8 subs came out the best.  I have made several attempts at reprocessing since I posted the image, but none resulted in an improvement.  i think I need more data.  I plan on collecting Ha as well.  I think it is overstretched.  The galaxy really looks better not as stretched--the valleys are darker and there is more contrast--but you don't get the extensions and trails off the companion as well.  I think more data will help.  

Rodd

Share this post


Link to post
Share on other sites
4 hours ago, Rodd said:

i think I need more data.

I don't think it's the data. You've captured an amazing amount of detail. Just look how tight the stars are, and the small clusters within the galaxy, and within the core itself.

4 hours ago, Rodd said:

 I think it is overstretched.  The galaxy really looks better not as stretched--the valleys are darker and there is more contrast--but you don't get the extensions and trails off the companion as well.

Have you tried blending the two images together, the one not so stretched and this one? You might find a happy medium between them?

I think I have to come back to this thought. Had you not mentioned the softness I probably wouldn't have zoomed in to see it! I'd have just enjoyed the image for what it was - a great M51 with a bold saturation (which I love but I know is a matter of taste).

Share this post


Link to post
Share on other sites

I think its great. As others have said, I'd reduce the colour saturation myself. I'd also look at the blue balance, whcih I think is a good way over towards cyan, but these are simple adjustments and a matter of taste anyway. More L subs would help pull out the faint extensions. I know you work in LP so this won't be easy. For comparison, Yves and I collected about 22 hours at F6.8 on this target. Much of that time just went into the extensions.

A really nice feature you've caught is the blue tip to the extended spiral arm sometimes known as the Bridge of Light. To me this says the arm is a foreground object and that it is not physically enangled in the smaller galaxy as was once thought. Redhift does put them at different distances.

Olly

Share this post


Link to post
Share on other sites

this is a great picture.

                             bob.

Share this post


Link to post
Share on other sites

In PixInsight:

Create a copy of the image. Remove all detail. Rename the image 'largescale'. Use pixelmath to subtract from the original, creating a new image called 'smallscale'. Stretch the 'largescale' using any method known by man. Then use pixelmath to add 'largescale' and 'smallscale' into a new image. This is one way to stretch faint signal.

Do this at the very end of your process.

Courtesy of Vicent Peris and RB Andreo.

Gerald Wechselberger has a video tutorial, showing a variation of the technique.

(But you maybe already knew all this)

Share this post


Link to post
Share on other sites
4 hours ago, Filroden said:

I don't think it's the data. You've captured an amazing amount of detail. Just look how tight the stars are, and the small clusters within the galaxy, and within the core itself.

Have you tried blending the two images together, the one not so stretched and this one? You might find a happy medium between them?

I think I have to come back to this thought. Had you not mentioned the softness I probably wouldn't have zoomed in to see it! I'd have just enjoyed the image for what it was - a great M51 with a bold saturation (which I love but I know is a matter of taste).

This image is doing something opposite to what I am used to....its growing on me.  Usually, when I look at an image the next day, it somehow seemed to degrade overnight.  I suppose that is the source of the philosophy of "putting the image in a drawer" for a time and revisiting before posting.  Strange.  At screen size (1:1 I assume) I agree--its nice.  But in my narrowband work I always process for full resolution mode, and use that as a test of image quality.  This image definitely does not pass muster at full resolution.  Maybe I should not worry about full resolution mode.  Anyway--I appreciate your comments.

Rodd

Share this post


Link to post
Share on other sites
4 hours ago, ollypenrice said:

I think its great. As others have said, I'd reduce the colour saturation myself. I'd also look at the blue balance, whcih I think is a good way over towards cyan, but these are simple adjustments and a matter of taste anyway. More L subs would help pull out the faint extensions. I know you work in LP so this won't be easy. For comparison, Yves and I collected about 22 hours at F6.8 on this target. Much of that time just went into the extensions.

A really nice feature you've caught is the blue tip to the extended spiral arm sometimes known as the Bridge of Light. To me this says the arm is a foreground object and that it is not physically enangled in the smaller galaxy as was once thought. Redhift does put them at different distances.

Olly

Thanks Olly--The image has grown on me--which is unusual for me.  I do feel that in full resolution mode it is not quite there.  I know you feel that images rarely stand up to viewing beyond 1:1, so maybe this is not a problem.  I do try and process my images for full resolution mode however.  For narrowband its much easier for me for some reason.  I think maybe I will try 15 or 20 min lums just to see if I can sharpen up some of the finer details.  Well see how the first sub looks, the target is in an area of the sky with the least LP for me.  Also, I think Ha will help in those areas that look like clumps of Ha emission but are really artificially saturated red areas. 

Rodd

Share this post


Link to post
Share on other sites
2 hours ago, wimvb said:

In PixInsight:

Create a copy of the image. Remove all detail. Rename the image 'largescale'. Use pixelmath to subtract from the original, creating a new image called 'smallscale'. Stretch the 'largescale' using any method known by man. Then use pixelmath to add 'largescale' and 'smallscale' into a new image. This is one way to stretch faint signal.

Do this at the very end of your process.

Courtesy of Vicent Peris and RB Andreo.

Gerald Wechselberger has a video tutorial, showing a variation of the technique.

(But you maybe already knew all this)

Thanks Wim--no, I am not familiar with this particular technique.  I know you can use MSLT and/or MSMT in a similar way you can do low pass and high pass layers in PS--but I have not been able to master this.  Vicents tutorial on this is pretty convincing ( The one I saw was on the iris nebula I think). I do use MSMT to make tight fitting star masks by removing the R layer with 4 layers defined.  But it does not pick up the large stars--even with very steep S curve stretches in "Curves", which brighten and enlarge the stars without picking up non stellar features.  

Rodd

Share this post


Link to post
Share on other sites
8 hours ago, ollypenrice said:

I think its great. As others have said, I'd reduce the colour saturation myself.

Olly

Well-Like a fool I diod not save the FITS (XISF) file when I saved the JPEG for posting.  I have tried too many times to reprocess the image and just can't achieve the level of success that I did with the version I posted.  So, I am left with the JPEG.  Here is a modified version--a bit less saturation, sharper details.

9 hours ago, Filroden said:

I don't think it's the data. You've captured an amazing amount of detail. Just look how tight the stars are, and the small clusters within the galaxy, and within the core itself.

Here's a modified version.  Unfortunately I cannot seem to reprocess the image very effectively, so I worked on the JPEG

 

6 hours ago, wimvb said:

In PixInsight:

Create a copy of the image. Remove all detail. Rename the image 'largescale'. Use pixelmath to subtract from the original, creating a new image called 'smallscale'. Stretch the 'largescale' using any method known by man. Then use pixelmath to add 'largescale' and 'smallscale' into a new image. This is one way to stretch faint signal.

 

I tried to reprocess so I could try this, but maybe I have been looking at this data too long and need a break.  I figured it would not work very well on the JPEG, which I think I have managed to sharpen up a bit.

 

LRGB-2a.thumb.jpg.4f9c6af94a0aeeac1e6efb5c3609c78a.jpg

 

 

 

  • Like 2

Share this post


Link to post
Share on other sites

Here you go--the RGB and Lum FITs files in case anyone wants to give it a go.  I think these individual images look pretty decent--if a bit "soft".  Its all downhill from here for me-except for the stars, which, for a change, I like.

Images are aligned and cropped to be equal

RGB.fit

Lum.fit

Share this post


Link to post
Share on other sites

Since the images were stretched already, I kept processing to a minimum: enhancing detail and increasing colour saturation.

On linear data, I would use deconvolution, and try to avoid HDR, which most often behaves like a power grinder.

Lum:

MultiscaleHDR (scale = 7)

Mild Exponential stretch with mask protecting the bright parts

RGB:

colour saturation (curves and color saturation with mask)

L*a*b combination of Lum with RGB

Star reduction (MorphologyTransform)

Slight sharpening of detail in galaxy with MLT bias on layers 2, 3, and 4

I think that it's easy to overprocess this image. This winter we've also had bad weather, even when the skies were clear. At leas here in Sweden, transparancy and seeing were poor, due to moisture in the air. Judging from the stars in your image, it must have been pretty much the same in the UK.

M51_Rodd.thumb.jpg.01bb3cb9b2409a7e9a5093716d9580e6.jpg

  • Like 1

Share this post


Link to post
Share on other sites
3 hours ago, wimvb said:

Since the images were stretched already, I kept processing to a minimum: enhancing detail and increasing colour saturation.

On linear data, I would use deconvolution, and try to avoid HDR, which most often behaves like a power grinder.

Lum:

MultiscaleHDR (scale = 7)

Mild Exponential stretch with mask protecting the bright parts

RGB:

colour saturation (curves and color saturation with mask)

L*a*b combination of Lum with RGB

Star reduction (MorphologyTransform)

Slight sharpening of detail in galaxy with MLT bias on layers 2, 3, and 4

I think that it's easy to overprocess this image. This winter we've also had bad weather, even when the skies were clear. At leas here in Sweden, transparancy and seeing were poor, due to moisture in the air. Judging from the stars in your image, it must have been pretty much the same in the UK.

M51_Rodd.thumb.jpg.01bb3cb9b2409a7e9a5093716d9580e6.jpg

Now that looks good Wim.  Thanks for the tips.  i will give it a go tomorrow.  Cloudy here for at least another week.

 

Rodd

Share this post


Link to post
Share on other sites

Well--One last try before I quit.  I think I will try 20min Lums to see if some of the detail will become sharper.  I had my Mure Denoise settings wrong, which dulled up the crayon considerably.  Still not sure the pencil is as sharp as it should be--judging from other images of M51.  But it is better.

 

LRGB-NoMD-1b.thumb.jpg.dd8e92db1cfd5c0f690de9a0673359a2.jpg

Share this post


Link to post
Share on other sites

And here is a touch less saturated. 

 

LRGB-NoMD-1b3.thumb.jpg.d8ee51179be06fbf14ab83eb9cff3264.jpg

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.