DaveS Posted August 31, 2017 Share Posted August 31, 2017 I wasn't going to post this yet, but it looks like it may be a while before I can add to the data. The moon is starting to get in the way, especially in [OIII], and I'm back to school after the summer break so have to be up at stupid o/clock. So here it is, The witch's Broom with 2 hours each of [NII], HII, and [OIII] in 10 min subs, mapping [NII] to red, HII to green and [OIII] to blue with no colour mixing between them. TS Photoline 130mm f/7 triplet with APM-Riccardi 0.75x reducer, 3nm Astrodon filters, SX Trius 694 camera cooled to -20 C Encoder- guided on an ASA DDM60 mount, Captured in Maxim DL6, stacking and processing in AstroArt 5 Stacked using Sigma Add, Bias only as the Flats I had were making things worse, as were the Darks Each stack had Adaptive-Divide gradient reduction before RGB colour assembly, then cropped to remove alignment artifacts (Mostly in the [OIII] data collected after meridian flip) and another Adaptive-Subtract reduction before DDP processing. This was carried out very carefully to preserve the delicate tendrils of HII and [OIII] emission while avoiding burning too much out. There were colour-noise artifacts in the background, which I reduced to some extent with Low-Pass Butterworth filtering, then finally used a little Histogram Stretch with curves to knock them down into the black while boosting the highlights a little, after another Adaptive-Subtract gradient reduction. Phew! C & C welcome as always, and feel free to download the PNG and kick it around a bit if you want. Link to comment Share on other sites More sharing options...
MartinB Posted September 2, 2017 Share Posted September 2, 2017 It's starting to get deep with the data you have gathered so far so. Colour's a personal preference but not quite my cup of tea however you can nicely see the contribution made by the different bands Link to comment Share on other sites More sharing options...
Ouroboros Posted September 2, 2017 Share Posted September 2, 2017 Lovely detail. I don't see much if any red (NII). Is that to be expected? Link to comment Share on other sites More sharing options...
DaveS Posted September 2, 2017 Author Share Posted September 2, 2017 Thanks Martin. Yes, I was surprised myself at how much feint "fluff" there was, given the less-than-transparent skies I had. One of the joys of 3nm filters. I still want another 2 hours or so in each channel to improve the S/N ratio. Regarding colour palette, I was somewhat restricted by not having PS to mix the channels (I may try the 16 bit Gimp I have), but also I wanted to go for a more "pure" "scientific" HST analogue. Link to comment Share on other sites More sharing options...
DaveS Posted September 2, 2017 Author Share Posted September 2, 2017 The [NII] is there, mixed in (In varying proportion) with the HII. Most of it is in the golden hues of the "fluff" under the blue [OIII] tendrils. There are some feint green HII tendrils there too. Link to comment Share on other sites More sharing options...
Rodd Posted September 2, 2017 Share Posted September 2, 2017 Looks very nice. The palette is very unique. I wouldn't say its green--which I usually eschew. Its more greenish gold, like the first green leaves of spring--one of my favorite colors. It definitely has the detail, and its very clear and clean. Well done. Rodd Link to comment Share on other sites More sharing options...
DaveS Posted September 2, 2017 Author Share Posted September 2, 2017 Thanks Rodd. The colour balance is as it came out from the RGB combination, so I can't take credit for it, as much as I'd like to! I think, that for my next round of subs, I may try pushing them to 1200 sec to see how the faint stuff comes up. Link to comment Share on other sites More sharing options...
MarsG76 Posted September 4, 2017 Share Posted September 4, 2017 It has a 3d effect to it, almost like the images where you need red/blue glasses... great image. Link to comment Share on other sites More sharing options...
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