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SH2-129 and OU4 integration time


lensman57
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Hi,

I have been looking at  various examples of the above nebulae for over a year now and I am still none the wiser as to what exactly is the minimum integration time to bring these ultra faint nebulae out of the background. I have seen some eye openers with as little as 8 hours of exposure and I have also seen some decent but totally unconvincing attempts with over 40 hours of integration. I know the , more the better but in the case of some of these images it seems that the more the better is not really any better.

A.G

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I suppose it depends on the QE of your camera, how dark the skies are, and the f-ratio of the imaging setup.  I tried over the last couple of sessions using f/5.2, Atik490EX (QE 75%), and 30min exposure with Astrodon 3nM OIII. Damn, it's faint! It's definitely there (only have 3 subs so far) but it's going to take some strenuous processing to bring it out.

ChrisH

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I suppose it depends on the QE of your camera, how dark the skies are, and the f-ratio of the imaging setup.  I tried over the last couple of sessions using f/5.2, Atik490EX (QE 75%), and 30min exposure with Astrodon 3nM OIII. Damn, it's faint! It's definitely there (only have 3 subs so far) but it's going to take some strenuous processing to bring it out.

ChrisH

Hi Chris,

Thanks for your reply. You are absolutely correct in saying that this one is a super faint target. I have no choice but to use my 383L+ and a Canon 200 F2.8 L which will have a front aperture mask of 58mm plus an Astronomik 12 nm Ha filter to start with and see what happens. This one is so large that I need every micron of the sensor to fit it in.

Regards,

A.G

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As said, it partially depends on the background sky, filter band width, lens speed, camera QE and time.

I've added an image from 2013 that shows what I did. I used a 250mm camera lens at f4 through a 5nm filter and Moravian 8300 for 30 minutes in OIII at kelling. I used the same set up from home in S Manchester but using a 5nm Ha for the bat and 20 minute subs. I think ( Can't find all the original files just now ) 19 subs.

What I found was that the Bat is not a Bat, it's a Pig ! No matter what I tried I couldn't get it to look as good as I wanted it. Thick and dull and unexciting. Bright enough though. It didn't require 19 subs but I kept going thinking it needed more.

The OIII is weak. The darker skies of Kelling probably helped but I only spent the one night on it collecting 4 hours. A bit of a stretch required to even get a hint of the Squid. I didn't go too wild because the noise starts to break through.

As for the view and speed - The 200mm lens will be more than ample. Is the lens no good at f2.8 ? Loads of people use them stopped down as a first port of call instead of collecting photons in bucket loads ! Try f2.8 with the OIII filter and see if the edge stars can be rescued or as an alternative, image the Squid at F2.8 and do a few more stopped down for the stars. As you can see my 250mm lens gets enough of the Nebula to be able to crop the 200mm if necessary.

I've shown here my original process from 2013 and if I wanted to do the area again I'd take more time and effort on it. The OIII content could be falsely boosted but I decided not to.

Only one way of finding out what works for you, go and try it :) I think the 8300 chip will cope ok as it's not the devil it's made out to be, and how much faster than f2.8 would you go even if you could ? I was working wide open at half that speed.

Dave.

PS. Have a look round for images of the Bat and see if you agree that most are fairly dull. I think I prefer the Bat as a Mono Ha image as it looks detailed and lively then.

post-493-0-79478300-1439374111_thumb.jpg

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As said, it partially depends on the background sky, filter band width, lens speed, camera QE and time.

I've added an image from 2013 that shows what I did. I used a 250mm camera lens at f4 through a 5nm filter and Moravian 8300 for 30 minutes in OIII at kelling. I used the same set up from home in S Manchester but using a 5nm Ha for the bat and 20 minute subs. I think ( Can't find all the original files just now ) 19 subs.

What I found was that the Bat is not a Bat, it's a Pig ! No matter what I tried I couldn't get it to look as good as I wanted it. Thick and dull and unexciting. Bright enough though. It didn't require 19 subs but I kept going thinking it needed more.

The OIII is weak. The darker skies of Kelling probably helped but I only spent the one night on it collecting 4 hours. A bit of a stretch required to even get a hint of the Squid. I didn't go too wild because the noise starts to break through.

As for the view and speed - The 200mm lens will be more than ample. Is the lens no good at f2.8 ? Loads of people use them stopped down as a first port of call instead of collecting photons in bucket loads ! Try f2.8 with the OIII filter and see if the edge stars can be rescued or as an alternative, image the Squid at F2.8 and do a few more stopped down for the stars. As you can see my 250mm lens gets enough of the Nebula to be able to crop the 200mm if necessary.

I've shown here my original process from 2013 and if I wanted to do the area again I'd take more time and effort on it. The OIII content could be falsely boosted but I decided not to.

Only one way of finding out what works for you, go and try it :) I think the 8300 chip will cope ok as it's not the devil it's made out to be, and how much faster than f2.8 would you go even if you could ? I was working wide open at half that speed.

Dave.

PS. Have a look round for images of the Bat and see if you agree that most are fairly dull. I think I prefer the Bat as a Mono Ha image as it looks detailed and lively then.

Many thanks Dave for your reply and advice. I took the chance and went for it and it sort of paid off. I binned the Oiii data and then drizzled it in PI to match the Ha and then did the combine in StarTools. I have posted the result in the imaging section. My problem is that I only live a couple of miles from the Airport by a busy and well lit dual carriage way so the LP is sort of Manchestertastic.

Regards,

A.G

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So far I just captured 4 x 1800s subs - only to discover I don't have a full Squid! Bit of a miscalcualtion... I should have used the reducer. It needed loads more subs but I'm abandoning this and will have to re-shoot with the 0.8x reducer on.

Sh2-129%20Squid%20AstHa%20ST_zpsjaykyhg4

ChrisH

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Many thanks Dave for your reply and advice. I took the chance and went for it and it sort of paid off. I binned the Oiii data and then drizzled it in PI to match the Ha and then did the combine in StarTools. I have posted the result in the imaging section. My problem is that I only live a couple of miles from the Airport by a busy and well lit dual carriage way so the LP is sort of Manchestertastic.

Regards,

A.G

I've seen your image and it's coming along really well. Notice the horrid Ha ? It does my poor head in and I can't understand why almost all Bat images look so bad.

Your Squid is doing fine. Just get more and then a few more still :)

I notice you're imaging at around f 3.4 Have you tried f 2.8 ? If you bin 2 at 200 mm the stars are not likely to look any worse.

Using the 200 mm instead of my 250 mm lens, you have more of the dust detail at the sides. Keep your eyes on that dust and don't damage it !

I shoot near the airport too. I have the motorway but you sound like you have Kingsway. All sent to amuse us  :)

Dave.

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So far I just captured 4 x 1800s subs - only to discover I don't have a full Squid! Bit of a miscalcualtion... I should have used the reducer. It needed loads more subs but I'm abandoning this and will have to re-shoot with the 0.8x reducer on.

ChrisH

Keep going with that one. With the reducer on I get the feeling it's going to be a very impressive image. Everything else you do is impressive.

Dave 

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I use 30 minute subs in NB and might try longer. Obviously I have a dark site.

If you are aiming to add the Ha and OIII to RGB or LRGB I can suggest a few heresies which might help, especially for the OIII.  :eek:  The OIII is going to occupy the central part of frame. Do you care what the edge stars look like? Are they going to feature in the final image? I doubt it. So why not run wide open? When you do apply the OIII to green and blue in Blend Mode Lighten you can just erase all the OIII bar the Squid itself because that's all there is anyway. You could also de-star it completely in OIII even over the part you keep.

Once you have the OIII over the green or blue in blend mode lighten you can pin the background sky and give it another lift in Curves. This would look terrible in a standalone OIII but it will propbably enhance the green and blue quite happily.( In BM lighten the noise, now stretched to screaming point, will be fainter than the original colour channel and won't be applied.)  In a nutshell you can stretch NB data way beyond its own noise limit and still apply it without bringing noise into the final picture.

Olly

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I've seen your image and it's coming along really well. Notice the horrid Ha ? It does my poor head in and I can't understand why almost all Bat images look so bad.

Your Squid is doing fine. Just get more and then a few more still :)

I notice you're imaging at around f 3.4 Have you tried f 2.8 ? If you bin 2 at 200 mm the stars are not likely to look any worse.

Using the 200 mm instead of my 250 mm lens, you have more of the dust detail at the sides. Keep your eyes on that dust and don't damage it !

I shoot near the airport too. I have the motorway but you sound like you have Kingsway. All sent to amuse us   :)

Dave.

Hi Dave,

Thanks for your kind words. I am away from Kingsway but just off Altrincham road. It is a nightmare now with all the tram lightings.

I may give f2.8 a try but whether the 1.25" filters cover the sensor @ F2.8 is to be seen.

I also forgot to mention that I held back quite a bit off the Ha data as it was overwhelming everything else. I guess the only solution is a hell of a lot more data.

Regards,

A.G

Edited by lensman57
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