M42 Processing help

[mbushee]

Hey Mike

Thanks for the input it's much appreciated

I should of thought to try binning. I do have a general question regarding the noise not sure if you have an answer or not if you don't that's fine.

So I'm guessing the excess noise is from light pollution since I'm shooting from town. If I drop the exposure to say 90s and do something like 60 exposures. Would that help eliminate some of the noise so I can keep my full resolution and still get good detail? I only shot 30 minutes this round since that's all could manage to get on spur of the moment decision to shoot it. Not sure if I'll get another shot until winter.

Yes the gt81 is a triplet. I picked it up specifically since it's easier for beginners and it puts up good image quality. I'm hoping to upgrade the camera next year the qhy268 looks really nice haha. I probably did overexpose sadly Sharpcap isn't working for some reason so I couldn't do a sensor analysis. Had I been able to do that I may have done different exposures. I was hoping with the small pixels and lower gain stuff wouldn't get over exposed. Part of the learning curve I suppose. I also think I had some thin high level clouds rolling through that night not sure if that would have caused the halos.

Good luck cabbage hunting.

[almcl]

As I try to work through this. Did either of you by chance use the binning module? I'm just trying to figure out why I end up with so much noise when I autodev the second time to get the same amount of details that you two are getting.

Sorry not to have responded sooner, yes, I did bin, mostly to speed up processing although it does help with noise too.

In addition to binning, I find there are 4 areas where noise can be reduced.

The 2nd Auto dev, increasing Ignore Fine Detail and reducing Outside ROI can help quieten the background, Decreasing shadow linearity may help too.

In Contrast, reducing the locality and the Dynamic range allocation may help.

In the Superstructure module Dim Small can help or masking the main subject and using the isolate preset, although perhaps not at full strength.

Then the noise reduction in Tracking turn off can help with uneven backgrounds or gas clouds.

There's also a Flux module technique (viewtopic.php?f=12&t=1173) although the results of this are usually too subtle to see with my data.

Hope that helps?

[mbushee]

Hi almcl,

Yes those are very good tips that I will try!

I have come to the conclusion I don't have enough exposure to get the same amount of detail in the full resolution as the binned version. I shot this from close to a bottle 6 with about 70-75% moon with only 30 minutes of exposure. If I sacrifice details in the full resolution I can definitely still get a nice picture it is just missing some of the nice outer dust clouds. Hopefully when Orion comes back around I can give it another go. Currently from my driveway I'm down to about only a 60 minute window where it is visible.

I did read through guys notes again and some of the items finally clicked in my head. Even though I've struggled with some of the post processing I've really enjoyed learning this. I can see all the potential of startools and can't wait to keep going! Thanks again for the help I'm sure I'll be back

[Mike in Rancho]

Hey Mike

Thanks for the input it's much appreciated

I should of thought to try binning. I do have a general question regarding the noise not sure if you have an answer or not if you don't that's fine.

So I'm guessing the excess noise is from light pollution since I'm shooting from town. If I drop the exposure to say 90s and do something like 60 exposures. Would that help eliminate some of the noise so I can keep my full resolution and still get good detail? I only shot 30 minutes this round since that's all could manage to get on spur of the moment decision to shoot it. Not sure if I'll get another shot until winter.

Yes the gt81 is a triplet. I picked it up specifically since it's easier for beginners and it puts up good image quality. I'm hoping to upgrade the camera next year the qhy268 looks really nice haha. I probably did overexpose sadly Sharpcap isn't working for some reason so I couldn't do a sensor analysis. Had I been able to do that I may have done different exposures. I was hoping with the small pixels and lower gain stuff wouldn't get over exposed. Part of the learning curve I suppose. I also think I had some thin high level clouds rolling through that night not sure if that would have caused the halos.

Good luck cabbage hunting.

Well, light pollution will be a possible gradient, as well as longer integration needed to pull the target out of the soup. So in a way you could say you would have "more noise," or at least not enough increased SNR, until the integration time is racked up.

For the subexposure times themselves, you will have to do some research on your camera to find it's sweet spot, or spots, though that's always dependent on conditions and target choice of course. See what most use for gain, offset, and cooled temp setting, for broadband targets. Unity gain should be 11 on that thing. Then maybe offset of 30 or 35, temp -10C? You could experiment with lower gain in order to open up dynamic range, but how "good" those settings are would require looking at graphs or testing things out.

My guess, however, is that you should be using a lot lower subexposures. It's a choice and filled with compromises. Shorter subs means more files to deal with and a bunch of other stuff. By and large you want to be long enough for fine details to be coming out of the read noise and your bias or darks level (as they will be partly subtracted off). If you can go longer, great, as that is fewer files to save and stack, but you also have to check and decide how much you are willing to accept of oversaturation. Maybe a few of the brightest star cores? Actual detail like in the M42 trapezium you likely don't want oversaturated.

I don't have a lot of experience with astrocams so can't really give any useful advice if things would be better (or easier) with NINA compared to Sharpcap for DSO.

Have fun with it. M42 will come back around, but there's plenty of other stuff available now (even if technically heading into "galaxy season") to practice on.