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.

sgl_imaging_challenge_banner_solar_25.thumb.jpg.f1d5d01d306644f613efd90ef96b314c.jpg

eshy76

Markarian's Chain and M87 - LRGB - 25-29 March

Recommended Posts

Posted (edited)

Hi everyone,

This is Markarian's Chain shot from my back garden over three nights in late March. Probably the deepest single image I've taken in terms of integration time...which leaves me feeling my processing is not quite doing the data justice...maybe I'll come back to it.

In any case, this is an incredible part of space; looking away from our galaxy reveals countless others!

The crazy number of Lum subs took a whole day for APP to chug through and so I've resolved to lower the gain from unity going forwards to get more manageable sub lengths than 15 seconds!

L: 1050 (!) x 15s R: 92 x 60s G: 165 x 30s B 165 x 30s....total integration time 8.2 hours.

Captured using APT, stacked in APP and processed in Pixinsight.

Thanks for looking!

Edit: Link to higher res version


1120066042_MarkariansChain2019-03-25.thumb.jpg.f4d0736bd743eaf23b6281f671bbebc5.jpg

Edited by eshy76
  • Like 14

Share this post


Link to post
Share on other sites

Very nice image. A lot of short subs to crunch. 

  • Like 1

Share this post


Link to post
Share on other sites
7 hours ago, tooth_dr said:

Very nice image. A lot of short subs to crunch. 

Thank you! Yes indeed...so while I got, erm, stacking benefits, the practical side was an issue in terms of the time it took to stack on a good PC. I also didn't dare drizzle the integration - that might have taken 2 days!

Share this post


Link to post
Share on other sites
35 minutes ago, Demonperformer said:

There are a lorra lorra galaxies in that image. Nice one.

Thanks! Yes - an incredible part of space. There is a tiny barred spiral in the bottom middle of the image which is just beautiful and perfectly formed...I'll focus on that one one day when I have some more focal length!

Share this post


Link to post
Share on other sites

I like this it is a very nice image and I wonder how many more are there we can't see.

A question what advantage is there in doing so many short subs over fewer longer ones?

Alan

  • Like 1

Share this post


Link to post
Share on other sites
1 minute ago, alan potts said:

I like this it is a very nice image and I wonder how many more are there we can't see.

A question what advantage is there in doing so many short subs over fewer longer ones?

Alan

Thank you! That is the golden question which I intend to find the answer to - with my level of light pollution, 15 secs at unity gain on my camera is more than enough for my Lum subs to drown out the read noise...so I've always used that sub length...

...which was fine for 200-300 subs, but this project really brought home the impracticality of stacking 1000+ subs. I just was thinking in terms of total Lum integration time (250 mins) and set the number of subs that way.

As far as I am aware, SNR benefits of stacking enter the realm of diminishing returns from about 200 subs onwards...so going forwards I'm going to lower the gain from unity (139 on the ASI1600) to 76 or 0 to try and get sub length up to between 30s and 60s and hopefully more like 200-400 subs to stack.

I can then answer your question fully. The 15sec approach benefits in terms of guiding being less critical, and things like clouds or planes or satellites not meaning minutes of data being binned. The Lum integration WAS beautifully smooth at least!

  • Like 1

Share this post


Link to post
Share on other sites
Posted (edited)

There is a video on here somewhere produced by rwg who goes into details of optimal sub length. I'l track it down for you when back on desktop.

As regards stacking, if you use sharpcap, you could stack them as you go along.

Edited by Demonperformer
  • Like 2

Share this post


Link to post
Share on other sites

I remember seeing something which in truth was Concorde for me, miles over my head, about short subs and CMOS sensors. I intend to get a couple of cameras this year, maybe a 071 and a 183 for my range of scopes. I am sure you would love to visit here where on a decently transparent you can see M33, but it does get almost overhead. Still what ever you have to do, it is still a lovely capture or should I say lots of captures.

Alan

  • Like 1

Share this post


Link to post
Share on other sites
51 minutes ago, Demonperformer said:

There is a video on here somewhere produced by rwg who goes into details of optimal sub length. I'l track it down for you when back on desktop.

As regards stacking, if you use sharpcap, you could stack them as you go along.

Thank you - that sounds interesting - I like the theory side of things as a guideline to what I do! And I did not know that about Sharpcap...I've got the pro version for the polar alignment routine, but have been using APT for capture. 

Share this post


Link to post
Share on other sites
20 minutes ago, alan potts said:

I remember seeing something which in truth was Concorde for me, miles over my head, about short subs and CMOS sensors. I intend to get a couple of cameras this year, maybe a 071 and a 183 for my range of scopes. I am sure you would love to visit here where on a decently transparent you can see M33, but it does get almost overhead. Still what ever you have to do, it is still a lovely capture or should I say lots of captures.

Alan

I hear you! The basic theory is that each sub should be long enough to drown out the read noise and with the really low read noise of CMOS cameras, that level is reached quickly with light pollution. Of course you can shoot longer than that for practicality, but if subs are too long, stars and highlights could get saturated. That is it in words - there are mathematical formula that try to calculate the optimal sub lengths!

Those cameras have really good reputations - I was looking at a 071, but ended up getting a 294, which I'm still learning. I think the 071 has an APS-C sensor?

Thank you for the kind words!

Share this post


Link to post
Share on other sites

Great picture.  Very difficult to tease out the colour on this subject, there is not a lot there but you've done it great.

For sure, my next camera will be a CMOS.

  • Like 1

Share this post


Link to post
Share on other sites
31 minutes ago, Demonperformer said:

Here is a link to the video. This is good if you wish to explore the theory a bit further.

Thank you very much! Something to devour this weekend!

Share this post


Link to post
Share on other sites
29 minutes ago, kirkster501 said:

Great picture.  Very difficult to tease out the colour on this subject, there is not a lot there but you've done it great.

For sure, my next camera will be a CMOS.

Thank you!

I really wanted to bring out the blues more but the data was not cooperating...in any case it's a nice data set to come back and add to. The background is a mottled black too - I actually think that is the beginnings of IFN (integrated flux nebula), but the integration time was too low and the light pollution too high to get close to bringing that out as pretty dust.

Share this post


Link to post
Share on other sites

By the way, NGC 4440 was the pretty barred spiral galaxy I was referring to earlier....you will be mine one day!

Share this post


Link to post
Share on other sites

Great image and a great thread! Right now I’m sticking with CMOS cameras for small galaxy targets. Having cut my teeth on a KAF 8300 camera, the shorter subs were really counter intuitive but I saw Robin Glover’s lecture at the PAS, and I’m just doing what Sharpcap recommends, running at 20-30 s for Lum and three times that for RGB, and the results I have obtained to date are very encouraging. A 1000+ subs to integrate is a bit daunting, but APP does get there in the end.

  • Like 1

Share this post


Link to post
Share on other sites

Thank you tomato! I went straight to CMOS, so short subs is all I know...looks like Sharpcap does a lot more than just polar alignment...I need to take a closer look.

Share this post


Link to post
Share on other sites

Yes, up until recently I only used SharpCap for Polar Aligning (which it does really well), but the sensor calibration and smart histogram features really seem to work with the CMOS cameras.

  • Like 1

Share this post


Link to post
Share on other sites
9 hours ago, David_L said:

Excellent effort!

David

Thank you!

Share this post


Link to post
Share on other sites
On 26/04/2019 at 11:12, Demonperformer said:

Here is a link to the video. This is good if you wish to explore the theory a bit further.

I watched the vid and read those posts yesterday - superb! The new stuff versus what I had read before was actually getting a number for light pollution and incorporating that into the equations.

It was an impressive presentation and makes me want to dig deeper into Sharpcap, if its creator is so knowledgeable.

Thanks again for sharing!

Share this post


Link to post
Share on other sites

For me, the biggest help has been the live stacking option. It does all the DSS  stuff while the capturing is going on. Even if you use multi-sessions, you stil only have one stacked image per session to do in DSS. Really opens up the "lots of short subs" approach that seems to suit these CMOS cameras so much.

  • Like 1

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By Davenn
      The Sun, 14 May 2019 One significant active region AR2741 One reasonable prominence on the limb LUNT LS60THa Solar scope, ASI 1600MM and ZWO Tilt Adjuster           Cheers Dave
    • By jjosefsen
      Galaxies in Leo   Hickson 44 is a group of interacting galaxies in the constellation Leo, also designated as Arp 316 in The Atlas of Peculiar Galaxies.     Inverted crop of luminance:   Equipment used: Altair Astro Hypercam 183v2 mono EQ6 Skywatcher ED80 N.I.N.A. used for capture and control, calibrated and stacked in Astro Pixel Processor, post processing in PixInsight with final color tweaks and watermark in Photoshop.   NGC 3190 is the nearly edge on spiral galaxy in the center of the image, with the very prominent dustlane. Lower to the right is NGC 3187 a barred spiral galaxy. Above we find the hazy eliptical galaxy NGC 3193.   NGC 3185 to the lower left is not a part of the Hickson 44 group, but is another lovely barred spiral galaxy.   The distance to Hickson 44 is approximately 80 million lightyears.   Total integration time is around 9 hours in a bit of a mixed bag of subs. 100 minutes of luminance. 153 minutes of Red. 150 minutes of Green. 141 minutes of Blue.   I made a synthetic luminance by stacking all lum, red, green and blue subs for a total luminance stack of roughly 9 hours, but it stands to reason that the contribution of the RGB only equates to a little under 3 hours of luminance. I am experimenting with just shooting RGB and combining it as a synthetic luminance, it is probably faster to get real luminance in the end. But shooting this much RGB compared to what I normally do, made it a little easier to process I think.   More details and a full resolution version here: Astrobin   Question: I am getting quite a bit of split color stars, I am assuming this is to do with the less than perfect correction of my optics?   Comments and criticism is always welcome!
    • By eshy76
      Hi everyone,
      One and a half clear nights for me early in the year and I focused on M45. As a naked eye visible target, I think subconsciously I never gave M45 the concentration it deserves, thinking I could always catch it another time.
      Anyway, despite lusting after the Horsehead, I kept my refractor pointed at the seven sisters in new moon skies and the result is below.
      I actually found it pretty hard to process...the seven sisters themselves were pretty well behaved, but I couldn't decide what to do with the background. I know this is a dusty region so I did not want to put DBE samples everywhere. But at the end the background seems a bit smudgy after tweaking curves - I'm not sure whether to darken the background or leave it as is.
      3.4 hours of LRGB integration. Full details on Astrobin.
      Thanks for looking!

    • By ACross
      Hi All, I am posting what I suspect is a newbie mistake question but hoping that someone can assist with the issue of flats.
      Although I have been fumbling around the sky, taking snaps at leisure, recently I became serious.  I have read up about the different calibration files (flats, darks, bias) and they seemed to make sense; different ways to capture the image defects and extract those from the image of the sky. After a few weeks (months) of further fumbling I went back to the very first target to receive my attention, M42 Orion Nebula.
      In short, I took 20x 30s exposures in LRGB  and ran these along with 20x LRGB each of darks, bias and flats. To obtain the flats I used a diffuse sheet of perspex (lightbox material) and an LED video lamp that has 180 white LEDs, turned to its lowest setting. Attached below is the stacked Luminance flat and the light image. In the lights I am getting very strong marks from dust and I had thought that the flats would subtract this but looking at the flats the marks are completely different shapes and do nothing to remove them from the lights.
      The attached has been further stretched to show the issue. Now, I am obviously doing something wrong but I have no idea what, any pointers from the vast pool of knowledge will be much appreciated.
      Thanks, Anthony
       


    • By urbko
      Hi, i have a problem with my atik camera, not sure if its just me or the camera but  every time i try to combine diferent chanels i get realy washed out pic, almost no color in them, all chanels look almost the same, i checked the efw but it works fine, so i have no idea what i'm doing wrong. please help :)
      ps. sory for my broken english.
      pps. here is link for M51 files that i shot with camera, if some one wants to check if they get the same result.
      https://drive.google.com/open?id=1X1EcBT5WLIe2uSsWM5zYsTNATk80ZgyP
      Urban
×
×
  • Create New...

Important Information

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