Only three hours of data, more than half of which was SII. I actually used NR on this (I pretty much never use NR), and I think I did it reasonably well this time. I followed parts of this half finished tutorial someone posted on CN.
Constructive criticism very much appreciated... still trying to find my place with this narrowband stuff.
Did I read in astrobin correctly that you used 4 min subs?
If so you've done pretty well the S2 and O3 are fairly faint in the chook. otherwise maybe consider some longer subs. I did 20 min subs for my effort and would consider going longer on S2 and O3.
Looking good Lee, especially for the short subs. I usually use 600-900s subs with narrowband, depending on the object.
When my new mount arrived I do hope to go nearer to 1800s for the deeper objects.
I do really like your star colours with the narrowband
I've done up to 40min narrowband exposures (on another target), but the math just doesn't support that approach with my gear.
For SII, I identified a region with of nebulosity that was, as far as I could tell by eye-balling it, about the faintest region that I could identify.
That region had a sky flux of 25.25e/min. The signal in that area was 0.788e/min (above the sky flux).
Given a camera with 5.4e read noise, this means that I'll end up with 89.9% of the SNR with 4min subs, compared to 32min subs, given the same integration time of 240mins. Granted, by doing more subs I lose out on some imaging time due to dithering and extra image download time, but I'm ok with that, since it only happens every 4mins anyway.
You can get away with a lot by using a very high QE sensor with low read noise, just do the math...
Edit: Corrected the number, since I stuffed the math up
Last edited by codemonkey; 19-05-2016 at 12:56 PM.
Gee Lee, this is a really nice image for someone still learning the ropes in narrowband.
Damn fine. The stars are perfect for one thing and its super sharp and detailed. Delicate. I like it a lot.
Thanks Greg, appreciate that! This is only my third tri-colour narrowband image, so definitely still learning the ropes.
Not sure if the noise reduction I did was subtle enough... I think it looks good at full res, there's still some natural looking "grain", but it doesn't look quite right at normal viewing resolution, to me anyway.
Pretty happy with the sharpness... I didn't even bother to apply any deconvolution or sharpening, but maybe I should... you can always do with a little decon
That's a lovely image Lee, subtle and soft but some nice resolution, your NR was clearly used appropriately All it probably needs is more data, simple, and you can do much of this when the moon is up
Thanks Mike! More data would be good, if only the weather forecast agreed with me. Looking like Monday might be the next night for imaging, but you never know, the weather could play nice for once and surprise me. Only thing is, by Monday night the moon's still 97% full and I need OIII more than anything at this point.
Nice job, Lee. Good detail visible in Thackeray's Globules.
Cheers mate.
Quote:
Originally Posted by billdan
Nice image Lee, I like the colours you have chosen. Am I right in thinking you have not done a Ha run yet?
Also where did you get these precise figures from,
" That region had a sky flux of 25.25e/min. The signal in that area was 0.788e/min (above the sky flux)."
Cheers
Bill
Thanks Bill. I got those numbers by stuffing up the math again by forgetting to include gain in my calculations lol.
Assuming I haven't stuffed something else up (highly likely!), actual sky flux was 9.5445 e/min, and target flux was 0.297864 e/min.
Now that I've redone it, it looks like 9mins would get me to the 90% SNR mark on this target, so future subs on this target will be longer. 4mins only gets me 79%, which is lower than I'd like. That's for SII anyway, I'll do some analysis on the OIII and potentially adjust sub length for that.
As for the underlying math, it's derived from this article.
The image does indeed include Ha data. It's got 10x240s Ha, 10x240s OIII and 25x240s SII.
Back to the image, I think it's a bit too subtle. I'll be pushing it harder and hopefully adding some more data to clean it up soon.
Lee, I think it's very fine, and a pleasure to look at. Perhaps it's slightly too blue.
Fine features in the image seem limited by grittiness rather than focus or tracking. More data will fix that.
Looking forward to seeing more narrowband from you.
Best,
Mike
Thanks Mike! Can you elaborated a bit more on the colour? Do you mean the blue is too saturated, or do you mean there should be less blue in the image and more of something else?
Out of curiosity, were you looking at the Astrobin version, or the attached version? I ended up pushing the one on Astrobin a bit harder, making it look a lot more gritty. The attached one didn't look too bad to me in that regard though.
Quote:
Originally Posted by Rod771
Looks very good, Lee! I wish I had the same camera orientation for my version. ( I wish I had your camera for that matter )
Nicely framed and processed.
Thanks Rod! Where possible I try to dig up wider field images of a target before I image it so that I can plan out the composition in advance. Saves me time on the night and helps me make better decisions. I usually just search through Astrobin, or sometimes I use Stellarium for the really bright/common targets that it has images for.
Quote:
Originally Posted by Ryderscope
Good project and image Lee.
Agree with the observation of more data.
The colour palette has worked and you've captured some very good detail.
Cheers mate! Definitely needs more data now that I've pushed it harder... one forecast is telling me tonight will have a few clear hours tonight, another not, so hopefully I can get some soon.
All it probably needs is more data, simple, and you can do much of this when the moon is up 
) 
