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DaveS

Rosette with old data

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90min HII, 72min [NII], and 80min [OIII] in 2 min subs with the 80mm f/4.4 and ASI1600 MMC camera through 3nm Astrodons. Piggy backed on the 130 f/7 mounted on the DDM60 and encoder guided.

Sigma Add stacking in AA5, then gradient removal, alignment and Trichromy with [NII] mapped to Red, HII to Green, and [OIII] to Blue, following the Hubble Palette.

Multiple Histogram Stretches, and a Low Pass filter to get rid of some of the noise. The RGB stack needed a serious crop as the [OIII] subs were at a steep angle to the other data, which is a pity as I can see plenty of outlying detail in the individual stacks.

 

5a5d0fcb67820_ZWOFirstNHO.thumb.jpg.be0bb35ddb2d3c4487d49421af5adfaa.jpg

I'm not taking this particular image any further as the data is too short. I've already got another 2 hours of HII in 5 min subs which I'll stack and add to the existing HII stack. The [OIII] I think I'll bin as it's so badly skewed, I'll try to replace it with 5 min subs properly aligned. The [NII] is OK as it stands, but I'll try to add to it.

When I'll be able to get more data is a moot point, as the weather here has been dire. There *may* be a couple of windows coming up, but I'm not counting on them.

 

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I'll just add that this data was acquired last year, Jan and Feb according to the dates on the subs.

I'd written off the [NII] data as I thought I'd made a mistake and set the HII filter instead. Being bored with the rubbish weather I decided to have another look, and it seems I *did* get the right filter after all.

In addition to being badly framed, the [OIII] data had a huge linear gradient through it, another reason to bin it.

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After saying I wouldn't take this further I tried some ideas I had.

Up till now I've combined the raw stacks in the Trichromy tool of AA5, then ticked "Auto" and "White Balance". This time I applied some linear stretching and LPF to the stacks first. After Trichromy and cropping the alignment borders I then performed many iterations of Histogram Stretch with curves, and a few linear

5a60edfb07e2c_NHOwithpre-stretch.thumb.jpg.7a6c7efaa3dbe3932c2605986e7dd3c5.jpg

TBH I'm not sure it's making much difference, the main thing, I think is to get a lot more data, especially [OIII], and some [NII].

The thing that's bothering me is no being able to get a clean Blue from the [OIII] signal. I *think* more data will help, but is it inherent in my capture / processing?

Any pointers will be welcome.

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