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Astrosurf

OIII Filter for Imaging Rosette Nebula?

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I took some longish-exposure subs of the rosette nebula at SGL7 with my unmodded camera but it didn't register anything much. Doesn't the nebula emit in mainly H-alpha and IR? I guess the IR filter in the camera was blocking out those wavelengths?

I read that the OIII filter will help bring out detail in emission nebulae such as the rosette when imaging with an unmodded camera? Is this so? If so, what make of OIII filter can I use with my Canon EOS and SW 200P?

Alexxx

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Hi Alex,

How much data did you manage, and how long were the subs. ?

I love the Rosette neb lots of glorious Ha in this one. With a standard DSLR you should still capture quite a bit of the red stuff. Sure a modded camera would be better but I am always surprised at just how much Ha comes through with modern cameras given enough time on the target.

Any chance of posting it up Alex so we can take a look at it.

I wouldn't bother with a O111 filter, 2" filters are so expensive and of no real advantage I don't think if using a standard camera .

Modding your DSLR or buying a modded camrea body would probalby be a better move for those Ha Nebs

Dave

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Thanks Dave. I'm at work at the mo but will get the info to you as soon as I can. Busy weekend this one! I'm excited that I should be able to get some pics! Can't afford a modded camera at the mo, sigh.

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Actually, OIII should in theory work quite well on a DSLR with its double green pixels in the bayer matrix... The Rosette is mostly Ha, though, and without modding your camera you'll need about 3x the length of exposure.

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Thanks Dave. I'm at work at the mo but will get the info to you as soon as I can. Busy weekend this one! I'm excited that I should be able to get some pics! Can't afford a modded camera at the mo, sigh.

No problem.

I processed a unmoddeed DSLR pic of the Rosette for a guy on here last year and he was pretty happy with the result with his standard camera, he only had 15 mins worth of data and the Rosette was easily identifiable, so its perculiar that you can't make it out that well.

Anyway don't worry. have a good day in work and I look forward to seeing your Rosette pic

Dave

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Actually, OIII should in theory work quite well on a DSLR with its double green pixels in the bayer matrix... The Rosette is mostly Ha, though, and without modding your camera you'll need about 3x the length of exposure.

Point taken Lewis quite right. As you say though exposure times go way up making things difficult with a DSLR

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The O111 filter line is at 501nm. It just so happens that the change over from blue to green is normally centred on approximately 500nm. As a OSC chip, as in the DSLR, has two green filters and one blue filter per pixel then you'll have three filters letting light through. So far so good.

What will you do with the O111 data and is it worth the expense ? There are a few images posted on SGL that show how good a modded DSLR is at capturing Ha. Would that expense be worth it to you ?

Dave.

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Thanks guys.

DaveW, my camera is unmodded. I was hoping the filter would help me get more detail in an image.

Dave Moulton, I managed to get 10 subs with tricky autoguiding at 5 mins each at ISO 800. Here's a MediaFire link to the stacked and unprocessed TIFF. I used the default settings in Deep Sky Stacker. I hope it downloads OK. It's 58MB!

EDIT: hold on, the file is too big for MediaFire. I'll reduce it a little and attach link in a mo . . .

Many thanks!

Edited by Astrosurf

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Hi Alex, I hope you dont mind but I was intererested to see what you had captured as I am using an umodded DSLR myself. I have had a quick play with TIF file and gave it really quick and dirty stretch. Certainly there is a lot of structure in there (afraid I am using GIMP so losing a lot of your data) and you have got a lot of stuff in there in the red spectrum. With a good play on the levels and curves I think you can get something that looks much less forced. (also had to compress and resize loads to get it to post on here :()

HTH

post-15439-0-75495200-1340530442_thumb.j

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There's definitely OIII in the Rosette that can be picked up by a DSLR. It does show up in different areas than H-alpha.

OIII_int_c_DBE.jpg

This is a "throw everything in the stack and hope for the best" reprocess I did recently. Modified Canon 450D 36x2m and unmodified 600D 17x2m both with 135mm at f/2. Various ISO. Astronomik OIII 12nm filter. As others mentioned before, a modified camera has no real advantage for OIII.

Looking up the 200P, at f/5 it would require about 2.3x longer exposure for a given level than I was at f/2, so the 5 minute subs mentioned should show roughly the same level as was getting at 2 minutes. The 5 minutes, I take it that was without any filtering? How was the background light level there?

Edited by GlassWalker

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Thanks Anweniel. I'm surprised you managed to download it as MF was saying it was too big, as I couldn't download it!

Thanks GlassWalker. Nope, no filter and it was a dark site but there still might have been a very slight haze (poss picking up a little LP from Hereford - can't remember). I can't remember if it had cleared by that time, or at all.

Here's the 47MB TIFF: http://www.mediafire...p6c25jrhworkwlb DELETED - - uploading original in a mo . . .

Edited by Astrosurf

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No problems downloading, in fact it was quite swift! If you are using PS or something I think you'll be able to resolve a much neater image I think you may have to be quite brutal with the adjustments initially to see where the info needs that stretch as the camera is not particuarly sensitive to Ha when the original IR filter is in place. A finer adjustment can be made later. My own skills at processing are pretty poor so hopefully you will do much better! Just wanted to demonstrate that the information is in there, as I suspected it would be with 5 min exposures.

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I'm not great at processing where it's a difficult image. I tried to stretch it in Levels and Curves but just got noise! I'll have to practice. I'll load up the original link in a mo for others to try in PS and poss give me clues!#

EDIT: Original 58MB image: http://www.mediafire.com/i/?9crhbbb7igc1ld2

Edited by Astrosurf

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Had a quick play with it... it's a bit too far in the noise for me to bring out, although I don't claim to be any master at processing. I think a better stack could help. I never managed to get great results out of DSS and currently use PixInsight. If you want to and can share the raws somehow, I could have a go putting it through that.

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Had a quick play with it... it's a bit too far in the noise for me to bring out, although I don't claim to be any master at processing. I think a better stack could help. I never managed to get great results out of DSS and currently use PixInsight. If you want to and can share the raws somehow, I could have a go putting it through that.

Here's a link to the 10 RAWs:

http://www.mediafire.com/?8moflrxsi2f80n4,hhe37t8e9btw459

I hope it works as I've not used MF for multiple files. Ta muchly!

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When I modded my Canon it was the best thing I ever did really brings out those nebula. Here was my shot of the rosette with the modded camera

Rosette%2520modded%2520master.jpg

Rosette%2520guided%2520efforts2.jpg

They both could do with more subs and seeing wasnt that great but at least you can see what modding the camera brings out

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I shot some O111 to add to RGB for the Rosette and in the end didn't use it. I did add Ha, as you'd expect to do. I found the O111 just gave some rather murky patches and not much else. However, Tom (Tom O'D) did apply it to his version. A marginal benifit on this target, I'd say.

Modding the camera would really make it sing though.

Olly

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integration_DBE.jpg

Astrosurf, here's my attempt. It's just too low in the noise for me to fish out the red stuff, and there's quite some sensor banding going on.

PixInsight Star Align, integrate with winsorize sigma clipping, dynamic background extraction (note - without some external reference, it's quite possible this would have tried to neutralise the H-alpha too since it should be everywhere in this field of view), and some tweaking in photoshop afterwards.

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Astrosurf, here's my attempt. It's just too low in the noise for me to fish out the red stuff, and there's quite some sensor banding going on.

PixInsight Star Align, integrate with winsorize sigma clipping, dynamic background extraction (note - without some external reference, it's quite possible this would have tried to neutralise the H-alpha too since it should be everywhere in this field of view), and some tweaking in photoshop afterwards.

That's sort of what I got. Thanks so much for trying. I'll do longer and more subs with higher ISO and see how it goes. But I think a modded camera is the only answer, in my price range that is. I do get awful sensor banding. The camera is my husband's so he doesn't want it modded! Fair enough as it was very expensive a few years ago.

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One other suggestion: the long focal length of the scope means you only got the core region of the rosette. Got a focal reducer you can try on it? Or alternatively, got any fast telephoto lenses?

As for the camera, a suitable used camera can be found for around £200 used, and if you're not too scared of taking it apart removing the filters would only cost you some time.

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I'm afraid £200 is too much at the mo. I'll have to wait until some money comes in. It's an expensive hobby this!

I do have a Canon 70-200 zoom lens I've used that's not too bad. I'll give that a go. I'll push the ISO up to 1600.

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