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M51 and IFN

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#1 Jared

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Posted 12 April 2021 - 01:27 PM

Like many of us, I have photographed M51 six or eight times over the years, getting slightly better results each time I did it. This year, for the first time, I started to see some things that I had never noticed before, not in M51 itself but in its surroundings.  First, there is the usual, beautiful structure within M51 itself. I feel like I was able to get a bit more "pop" than usual just because I added some H-Alpha into the red channel. That's nice, but hardly revolutionary.  The next thing I managed to do was capture some decent quality data from fairly dark skies rather than my usual Bortle 9. It's not a log of data--only a single night--but even a couple hours from Bortle 4 got me quite a bit deeper than more than twenty hours from home. Nice!  So, what are the things I hadn't seen before?  

 

First, there is IFN around M51. Not exactly a shocker, I know, given its location in the sky, but I had never seen it before in amateur images. Now that I've gone and looked for it on the internet, yes, it is there, but I've certainly never captured it before. In my image you'll see a faint finger of nebulosity coming down from the upper right corner of the image. If I really push the luminance data there are a couple areas as well, but I didn't have enough integration time to include those areas without more noise appearing than I wanted. Still, pretty cool.

 

Second, I can just make out a faint tidal stream coming off NGC 5198--the elliptical galaxy to the south (right) of M51. Never seen that before. Again, if I go search for it in other images I'm hardly the first, but it was fun to capture something totally new to me. Sorry if the JPG compression and file size requirements remove the tidal tail--I can post a stretched crop to show it as well as a more heavily stretched image of the IFN.

 

This is 2.5 hours of luminance data and one hour each of red, green, and blue data captured from a Bortle 4 site near Lake Berryessa on Saturday night. I added an additional 4.5 hrs of H-alpha data into the red channel (taken from home under Bortle 9 skies) to make the HII regions in M51 stand out. Seeing conditions were so-so (about 2.3" FWHM). Honestly, I was hoping for better based on the forecast, but I'm super happy with the rest of the image. The telescope was a 305mm Riccardi-Honders at f/3.8. The mount used was an AP1100GTO AE. Images were all unguided. The camera was a QHY600 monochrome.

 

C&C welcome (as long as any criticism is constructive).

 

M51.jpg

 

- Jared


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#2 Jared

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Posted 12 April 2021 - 01:32 PM

Here is a heavily stretched luminance frame that may make it easier to see the IFN and the tidal tail on NGC 5198...

 

master_Light_Lum.jpg

 

- Jared


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#3 dugpatrick

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Posted 12 April 2021 - 01:32 PM

Wow!  Great capture!

 

Doug


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#4 rob1986

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Posted 12 April 2021 - 01:35 PM

are those two dust lanes the remnants of spiral arms?


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#5 coinboy1

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Posted 12 April 2021 - 01:35 PM

Thats the deepest shot of M51 I have ever seen! Great shot and unguided!!


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#6 Jared

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Posted 12 April 2021 - 01:39 PM

And here is the annotated image from PixInsight.

 

M51_Annotated.jpg


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#7 Jared

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Posted 12 April 2021 - 01:42 PM

are those two dust lanes the remnants of spiral arms?

Which dust lanes? You mean the the lanes between the spiral arms?  Presumably just density waves that make the spiral arms in M51 more prominent  due to recent interactions with NGC 5195. Not sure we're talking about the same thing, though.



#8 Jared

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Posted 12 April 2021 - 01:46 PM

Thats the deepest shot of M51 I have ever seen! Great shot and unguided!!

Thanks! It's not all that deep, actually, but compared to what I can usually get from my Bortle 9 location even over several nights it's pretty good. I was happy with the result.

 

The AP1100GTO AE mount has absolute encoders, so as long as you have a decent pointing model it can handle moderately long exposures without guiding. The focal length of the scope is pretty low as well, which helps. These were three minute subs. 



#9 mtc

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Posted 12 April 2021 - 01:54 PM

I just realized the true advantages of darker skies, with M51 as my example.. Now I see the advantages of faster optics!

Impressive!


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#10 Dan_I

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Posted 12 April 2021 - 02:01 PM

Very very impressive shot Jared with lot of fine details and a tremendous amount of info in the background.  I'd prefer with the highlights a little bit less "mute" but this is a matter of taste of course.


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#11 rob1986

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Posted 12 April 2021 - 02:15 PM

there are 2 large dust lanes connected to the central dust obscuration in 5195



#12 Jared

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Posted 12 April 2021 - 02:22 PM

I just realized the true advantages of darker skies, with M51 as my example.. Now I see the advantages of faster optics!
Impressive!


Yeah, I managed to get significantly deeper in 2.5 hours under decent skies than I was able to do in about 15 hours under light pollution. The faster optics are nice for wide fields, but don’t really matter much in terms of total depth. If I had used a 12” f/8 scope instead and just binned the camera 2x2 I would have gotten essentially the same result. Perhaps even a touch better since the central obstruction could have been much smaller.

To a first approximation, all scopes of a given aperture should go to the same depth in the same integration time as long as long as you sample at the same arc seconds per pixel (via hardware binning or just re-sampling in software).
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#13 Jared

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Posted 12 April 2021 - 02:26 PM

Very very impressive shot Jared with lot of fine details and a tremendous amount of info in the background. I'd prefer with the highlights a little bit less "mute" but this is a matter of taste of course.


I’ll take a look at it again tomorrow with fresh eyes to see if I agree with you. I saved my work along the way so I can re-process as required. I am also worried that the HDRMT created a bit more contrast than I wanted in the spiral structure. The challenge was that the stretch needed to be pretty aggressive to hint at the IFN. That pushed the highlights waaayy up.

#14 rob1986

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Posted 12 April 2021 - 03:07 PM

the red lines trace the dust lanes. to me it screams barred spiral reminant.

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#15 andysea

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Posted 12 April 2021 - 03:41 PM

This is beautiful, well done Jared!


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#16 Jared

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Posted 12 April 2021 - 07:47 PM

the red lines trace the dust lanes. to me it screams barred spiral reminant.


Got it. No ideas. I haven’t read anything that would suggest that.

#17 lucam

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Posted 12 April 2021 - 09:48 PM

Beautiful work, Jared! Very elegant image without pushing the data outside of its comfort zone.

 

Thanks for sharing!

 

Luca


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#18 rob1986

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Posted 12 April 2021 - 11:37 PM

Got it. No ideas. I haven’t read anything that would suggest that.


like they said, this maybe the "deepest" photo they've seen. its not impossible that this is the first time the remnants have been photographed. my suggestion is submit this to your local astronomy department and ask their opinion. if so, it may be worthy of publishing. how does an academic article with your name as a contributer sound?

I'll try to submit this to my old astronomy professor as well.
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#19 Gert

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Posted 13 April 2021 - 12:44 AM

Hello Jared,

 

Congratulations on the excellent result. Can you tell a bit about the camera and processing? Are you moving from CCD to CMOS ?

Cheers,

Gert


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#20 ArandomPilot

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Posted 13 April 2021 - 02:53 PM

Like many of us, I have photographed M51 six or eight times over the years, getting slightly better results each time I did it. This year, for the first time, I started to see some things that I had never noticed before, not in M51 itself but in its surroundings.  First, there is the usual, beautiful structure within M51 itself. I feel like I was able to get a bit more "pop" than usual just because I added some H-Alpha into the red channel. That's nice, but hardly revolutionary.  The next thing I managed to do was capture some decent quality data from fairly dark skies rather than my usual Bortle 9. It's not a log of data--only a single night--but even a couple hours from Bortle 4 got me quite a bit deeper than more than twenty hours from home. Nice!  So, what are the things I hadn't seen before?  

 

First, there is IFN around M51. Not exactly a shocker, I know, given its location in the sky, but I had never seen it before in amateur images. Now that I've gone and looked for it on the internet, yes, it is there, but I've certainly never captured it before. In my image you'll see a faint finger of nebulosity coming down from the upper right corner of the image. If I really push the luminance data there are a couple areas as well, but I didn't have enough integration time to include those areas without more noise appearing than I wanted. Still, pretty cool.

 

Second, I can just make out a faint tidal stream coming off NGC 5198--the elliptical galaxy to the south (right) of M51. Never seen that before. Again, if I go search for it in other images I'm hardly the first, but it was fun to capture something totally new to me. Sorry if the JPG compression and file size requirements remove the tidal tail--I can post a stretched crop to show it as well as a more heavily stretched image of the IFN.

 

This is 2.5 hours of luminance data and one hour each of red, green, and blue data captured from a Bortle 4 site near Lake Berryessa on Saturday night. I added an additional 4.5 hrs of H-alpha data into the red channel (taken from home under Bortle 9 skies) to make the HII regions in M51 stand out. Seeing conditions were so-so (about 2.3" FWHM). Honestly, I was hoping for better based on the forecast, but I'm super happy with the rest of the image. The telescope was a 305mm Riccardi-Honders at f/3.8. The mount used was an AP1100GTO AE. Images were all unguided. The camera was a QHY600 monochrome.

 

C&C welcome (as long as any criticism is constructive).

 

attachicon.gifM51.jpg

 

- Jared

Constructive Criticism?

 

Absolutely none! The image is the perfect blend of sharpness with stars that look natural. The background galaxies look incredible. It's such a natural looking galaxy I feel like I am viewing it with my own eyes from that distance. Incredible work, keep at it.


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#21 elmiko

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Posted 13 April 2021 - 05:09 PM

This is outstanding Jared! Thanks for sharing this.


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#22 Jared

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Posted 13 April 2021 - 05:32 PM

like they said, this maybe the "deepest" photo they've seen. its not impossible that this is the first time the remnants have been photographed. my suggestion is submit this to your local astronomy department and ask their opinion. if so, it may be worthy of publishing. how does an academic article with your name as a contributer sound?

I'll try to submit this to my old astronomy professor as well.

By all means let me know what your professor says. I’m not sure the image shows anything that isn’t easy to achieve with larger scopes (aside from the widefield aspects), but I’m happy to get feedback.



#23 Jared

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Posted 13 April 2021 - 06:07 PM

Hello Jared,

 

Congratulations on the excellent result. Can you tell a bit about the camera and processing? Are you moving from CCD to CMOS ?

Cheers,

Gert

Sure, Ger. The camera was a QHY600, so I have, indeed, moved from the SBIG CCD camera to CMOS—just a couple months ago. I love the camera. Cooling is very good, field of view is huge, read noise is negligible. What’s not to like? I think I even get a touch more resolution on nights of good seeing, though it’s hard to tell for sure since I haven’t had any nights of good seeing since I bought the camera. Decent seeing, yes. Good? No.

 

As far as technique and processing... It’s fairly straightforward for anyone using good equipment and PixInsight. No guiding is required with my mount (absolute encoders) and short subs like these. When I got to the dark sky site I took twilight flats, twenty per filter. I then polar aligned using PemPro and got a result that was within an arc minute or so. I then built an 80 point sky model using APMM so I could skip guiding. I took a few sample shots with and without guiding just to make sure I was getting equivalent FWHM values in both situations. I was. Seeing was decent but not exceptional at something like 2.2” FWHY for the central two thirds of the frame. I setup a sequence in NINA to shoot ninety minutes of RGB images, then 2.5 hours of luminance (when the target was high in the sky), then another ninety minutes of RGB. Checked the first few frames, then went to bed in the car. NINA ran the whole routine, then parked the mount around 4am and warmed up the camera.

 

I calibrate my frames manually rather than using WBPP just because I use the overscan region of my chip to account for bias drift. WBPP has a checkbox for incorporating overscan, but I haven’t managed to get it to yield the correct results yet. So I calibrate using the individual processes. I then use WBPP for cosmetic correction, registration, and image integration. I process luminance first, then RGB. For the luminance frames, I used Mure Denoise, then cropped, then DBE to flatten the image. Next was a slight deconvolution. This is a subject where “less is more” in terms of deconvolution since I didn’t want to create halo artifacts. I used a luminance mask to limit the areas where deconvolution would be run and also used a star mask for local support. I think I chose 10 iterations. 

 

The luminance data looked really good, so I wanted to stretch them enough to show (if faintly) the IFN as well as the tidal tail streaming out from NGC 5198. That meant star bloat was going to be a problem. I decided to run a morphological transformation to shrink the stars a touch so they wouldn’t swell as badly when the data were stretched. The stretch itself was a tough compromise. I was worried about highlights in the galaxy going past what I could easily recover in HDRMT if I tried to make the tidal tail and IFN obvious. The result was a compromise. HDRMT recovered the blown out highlights in M51. I used the “substitute preview” script to make sure HDRMT was only applied to M51 itself.

 

RGB data were not nearly as good. Biggest issue was that I have a big chip in my green filter—I dropped the entire carousel a couple weeks ago and the green filter was damaged. Like an idiot, I had rotated the chip to the absolute worst possible location, one of the corners. As a result, that meant it intruded way into the field of view. I’ve already got vignetting problems using 50mm circular filters with such a fast scope. The chip made things worse. Oh,well, at least the issue is in the color data not the luminance. With the meridian flip, though, that meant two corners of data representing nearly ⅓ of the frame were bad. 

 

RGB got heavy noise reduction—Mure Denoise as well as TGV and a low pass filter (multi-scale linear transform). Normal channel combination, crop, and DBE followed by a photometric color calibration. I then split out the red channel and merged it with my H-Alpha data using the technique described in LightVortex.com. ARCSINH stretch (less noise than a normal histogram transformation) followed by a mild histogram transformation to get tones where I wanted them.

 

I do LRGB combine and final touch up in Photoshop rather than PixInsight since it lets me work freehand for things like local contrast adjustments, etc. I overplayed the luminance layer onto the RGB layer, the converted to LAB mode so I could tweak the saturation using a curve to the A and B channels. Like ARCSINH stretch, this avoids the color noise if you were to just bump up the saturation in RGB mode. Because this is Photoshop and I can select areas by hand, I could apply different levels of saturation to stars and to the galaxies. 

 

Finally, some local contrast adjustments on the galaxies by using a high pass filter set to “soft light” or “overlay” (depending on the scale of the adjustment). I think I used a high pass at 2.6 pixels and other at about five pixels. I used a mask to make sure the local contrast adjustments were applied to the brighter portions of the galaxies only (since this contrast bump tends to highlight noise), then painted out the brighter stars by hand so they wouldn’t swell. Imported to Lightroom Classic just for database and file management. Don’t think I made any adjustments in Lightroom. Maybe a touch of sharpening? Not much if anything.


Edited by Jared, 13 April 2021 - 06:10 PM.


#24 Jared

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Posted 13 April 2021 - 06:09 PM

Constructive Criticism?

 

Absolutely none! The image is the perfect blend of sharpness with stars that look natural. The background galaxies look incredible. It's such a natural looking galaxy I feel like I am viewing it with my own eyes from that distance. Incredible work, keep at it.

Thanks so much! As the person who took the picture, I obviously see all the warts. Glad to know the result looks good to someone who doesn’t know everything that went right and wrong through the process. I definitely want a result that looks natural and not over processed. At the same time, I want the galaxy to “pop”. That, and hinting at the fainter background stuff, is what I was trying to achieve.



#25 Jared

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Posted 13 April 2021 - 06:14 PM

Very very impressive shot Jared with lot of fine details and a tremendous amount of info in the background.  I'd prefer with the highlights a little bit less "mute" but this is a matter of taste of course.

Whoops. I think I read your post backwards—highlights LESS muted, not more. Obviously, to each his own. 

 

I did look at the data with fresh eyes this morning. I decided I had overdone it very slightly on the contrast and re-processed the results. Didn’t make a big difference—frankly nothing that shows in a 16000 x 10000 pixel JPG so I won’t bother to re-post. I’ve really got to learn to be more patient and not post my first result—ever. I keep telling myself that, but in the excitement of the moment I usually post anyway. This one didn’t change much with a day to review, though.




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