StarTools

So here's what I came up with for my January M42 and friends. Still learning all about this telescope with mirrors thing, and trying to figure out its idiosyncrasies for acquisition and calibration. Like light leaks and internal reflections. This image has all of that. And in between my early month sessions and late month session, of course I removed the secondary to straighten and realign the spider vanes, rendering the stack a bit of a Frankenstein.

Total of 4 hours and 20 minutes over three nights, consisting of 1,560 10-second subs with dithering, flats each session, master bias, ISO200, Nikon D5300f/s, SVB UV-IR cut, MPCC Mk III, Orion 6" f/4 Newt, HEQ5 Pro, BYN, DSS, and ST 1.8.

Due to the bizzaro gradients I split the stack and ran a different Wipe on each channel, strongest on the green. I think it helped but still didn't completely eradicate a deep color anomaly off the top edge of M42. Also unsure if ST's splits and saves, as 16-bit RGB tiff if I have that right, result in any loss of detail when recomposed as compared to the 32-bit original?

It also took some adjustments to normal settings and a quirky ROI in AutoDev to get things where I wanted. After that, contrast, HDR, and SVD did their magic. Color was a bit strong coming out of my split-and-recombine technique, but dropping the global sat to around 100 took care of that, and I then made my adjustments to bright and dark sat, and the bias sliders. A no-iteration Shrink with a touched up mask was then used for remnant deringing.

Although surrounding dust can be stretched out a lot more, I didn't think my data warranted it. Plus, with some anomalies still present on the right side of the image, I was being forced to crop it off, which ruined the overall framing. So in addition to minding my stretch in AutoDev, I ran SS-Isolate with gamma 0.75 to push things back, followed by a finishing denoise.

I followed that with a few post-tracking touch-ups: Having saved prior to SS, I made a star mask on that file and used it to bring some stars back in via Layer, as I felt the SS had dimmed some of those a little too much. My next star repair was to again create a star mask, this time only of the stars with blown cores, and use a slight Layer-Kernel radius to tame them a tiny bit. Even at only 10-seconds, all the bright and medium star cores had maxed out the D5300 sensor.

Lastly, I took that final image into FilmDev, where I lowered the gamma to 95, and dropped back the red luminance contribution. Those helped to further minimize the surrounding chop, and eased back on M42's reds and helped other detail be more easily seen. Or so it seemed. I then ran another light DN which only cleaned up the outer chop.

Hopefully when I get better with this Newt less extra work will be needed. But M42 is a bit of a special animal as well, so who knows.

So I got a comment on CN about too much green, particularly in 45 Ori (third star down on the right of the Running Man).

Does anyone see that?

I knew it was there based on MaxRGB, but when using my eyes and a x-rite calibrated monitor, it just appeared to be the slightest of green-tinted yellow. So I left it. But now I'm wondering if I should just open up the final (non-linear no tracking) and cap off any green remnant.

Technically it seems that 45 Ori is a whitish blue based on Stellarium and other internet sources, but in so many images it looks yellow - perhaps real, or perhaps relative to what is around it. I just kind of presumed it might also be due to whatever dust or gasses it might be shining through.

But I'm kind of leaning towards capping it off as (one of many no doubt) an error in my data, therefore better matching up with the known spectra too. On running a quick test it the green cap doesn't seem to be otherwise messing with the overall colors of the image.

Nice one Mike! I like it.

To be honest i don't see green, but on CN some people made remakes on former images i made too..seems i am not very sensitive to green...

Quite some work flow you have gone through...

My M42 went to the blue but fortunately i got quite some dust out of the picture...which came out after binning to 25 percent ..
HDR module worked marvelous on it, and so did the flux for then center core...

Mike

Nice image, I think that trying to eliminate every bit of green on the Max RGB screen can lead to a lot of slider tweaking. I went down the layering mode to expose the core but even 10s subs with the RASA are a little too long. Next time it will be lower gainon my ZWO 071. I love the dust around M42, it gives the nebula a contrast boost and shows its context, so for me, combining different sub lengths is necessary.

My blended images in Gallery are 80 minutes each of 40s and 10s. F2 has its advantages

Cheers

David

Topographic wrote: ↑Wed Feb 09, 2022 12:54 pm Mike

Nice image, I think that trying to eliminate every bit of green on the Max RGB screen can lead to a lot of slider tweaking. I went down the layering mode to expose the core but even 10s subs with the RASA are a little too long. Next time it will be lower gainon my ZWO 071. I love the dust around M42, it gives the nebula a contrast boost and shows its context, so for me, combining different sub lengths is necessary.

My blended images in Gallery are 80 minutes each of 40s and 10s. F2 has its advantages

Cheers

David

Thanks, David.

Nothing wrong with slider tweaking. It's what we do. Depends on the goal.

I'm not a green hater and don't chase after all bits of it. In fact I generally don't even use the cap green, absent a need for it. But even as to the main global green slider, too much one way or another can affect your overall purple balance. In some cases, for example if for whatever reason star sampling didn't lead to the the right looking hues, I'll increase the green.

Here, I pretty much just had one star that was belching up an odd green tint to it. Who knows why. I'm still trying to figure out all my light leaks and internal reflections with this thing, as well as working out the right ways to take flats.

For me, this f/4 is awfully fast and is taking some new learning. I can't imagine f/2!

Edit to add: on my final version for the CN challenge I did in fact do a clean up on that star, after reviewing spectral data.