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Messages - monkeybird747

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1
Have you tried the Average Spiral Galaxy model? G2V is biased toward reds. Maybe check the spectral types of the predominant stars in the trapezium and try a model that is similar?

Could you tell us the type of frames being used (OSC, LRGB, etc.) and at what point in your processing you are using PCC?


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General / Re: Resolving M31 Core
« on: 2018 November 12 18:25:22 »
Try the DarkStructureEnhance script for your dust lanes. Default amount is pretty good. Try lowering it to suit taste. Easily overdone.

If you're worried about your core you could do as mentioned above, or shoot some more frames at a much shorter exposure, then use HDRComposition to create a HDR image. Works well.

3
I’ll add to the above to be sure and reset the screen transfer function once you’ve drug it’s triangle to the histogram transformation window. Otherwise I think your live preview will apply the stretch to the stretched image (double application of stretch), and not represent the changes you are planning on applying to image.

Once you apply the stretch through histogram transformation your preview window will again look off because you are stretching the image you just stretched again. Reset the HT tool after applying the stretch for your preview to be accurate again. This applies to similar tools like curves and saturation. Apply, the reset and evaluate if further application is needed.

4
Thanks Rob. On some other images I get the comment that my stars are lacking color. I notice this on the raw subs as well. I wonder if this could be a side effect of the LP filter. It’s been a while since I imaged without it, so maybe a test is in order. I’m nearing the end of my DSLR career and begun researching mono astrocams.

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General / Re: Photometric Color Calibration Problems after stacking
« on: 2018 September 17 12:07:29 »
I recently had this happen. In my case the previous target coordinates were still being used even though I was selecting "get coordinates". I had not changed the target in the search box at the top of the get coordinates window. Once searched for new target the proper coordinates popped up and it worked fine.

Also be sure to check the pixel scale and focal length settings. If you drizzle at a scale of 2 you have to double the focal length or half the pixel size (I think I did both and it still worked). From the support documentation:

If you are using drizzle, please remember to change the focal length or the pixel size according to the Scale parameter value used in DrizzleIntegration. For instance, if using a Scale value of 2, you should then multiply the focal length by 2 or divide the pixel size by 2.

6
Thanks Rob. Incidentally, in reading the stats on this filter it also boasts "near perfect color balance" for modified DSLR. For me there is still a significant blue-green color cast using this filter. Easily fixed during PCC, but still I'm not sure what their idea of near-perfect balance is, or if its my understanding of what they mean that is flawed.

Here is a link to my latest M31 image using PCC. There were no color tweaks other than increased saturation on total image. I was hoping to get close to what Juan refers to as "documentary" color.

https://astrob.in/366999/0/

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General / Re: Image Stacking after a meridian flip
« on: 2018 September 17 11:41:13 »
I use auto meridian flips and never move/rotate the camera after a flip. I take flats after the imaging session is complete and feed it all in to PI without even thinking about it. Works great! But yeah, if you rotated your camera independently of the OTA after the flip you'd have to do as above with your flats. I think the computing time of star alignment takes a little longer with images that are 180 out from each other, but PI powers through with no problem. (And yeah, it's wicked cool!)

8
General / Re: HDR - Individual sets against fully stacked version
« on: 2018 September 17 11:34:07 »
I just finished an HDR Composition of Andromeda a few days ago. The tutorial I read (LVA) had you calibrate, integrate, and DBE the individual exposures, then use the HDR Composition routine on the resulting integrated images. For me I only had 300s and 60s frames, so I used HDRComp on two fully preprocessed and integrated images. I suppose in this fashion you would lose the benefit of stacking more images and the associated gains in SNR. I'm not 100% on that part though. For a target like this that may not be much of a consideration.

For Andromeda I had to significantly reduce the Binarizing setting to get the amount of masking of the core I wanted. The default settings only masked a tiny dot at the center of the core, and I wanted to replace more of the saturated core with the 60s exposures. I also bumped the smoothness up to 20 or so. All this had the effect of including a handful of the most saturated stars in the mask, replacing them with the less saturated versions of the 60s exposures. This was my first attempt at this process, so please take with a grain of salt. After this was photometric color calibration using Sb galaxy profile. I saved the HDR Multiscale Transform for near the end of processing. Final version linked below.

https://astrob.in/366999/0/

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I’m not sure where I got the UV part. It’s not mentioned specifically on the Astronomik website. For some reason I thought this was part of the filter, and needed for a fully modified DSLR. What you say about the statement referring to pass filters makes sense though.

10
In reading release notes from Juan I noticed this statement:

“We cannot expect any robust color representation when using narrowband filters, or filters located in the UV or IR wavelength ranges. ”

Would this apply to using a clip in CLS-CCD light pollution filter? I believe it has a uv filter component.

Someone else asked if adjusting saturation evenly across all channels effectively negates the PCC process, but that thread is a year old and unanswered.

Finally, is SCNR necessary if you use PCC? I’m currently applying it prior to PCC.

Thanks,

MB747

11
General / Re: Inserting Ha into an RGB Image
« on: 2018 July 14 09:48:07 »
Ive run into this where my Ha data is not drizzled because of a lower sub count than my OSC master, which is drizzled. I’ve only done it a few times, but I did resample the Ha to match the RGB before star alignment. Plus there was a superpixel debayer involved with the Ha. I’ll try just the star alignment next time to see what happens.

12
General / Re: RGB star color preservation with NB
« on: 2018 July 13 06:59:40 »
There is this tutorial that uses a good star mask and MorphologicalTransformation to erode/remove the unwanted stars from the NB image.

http://www.lightvortexastronomy.com/tutorial-reducing-star-sizes.html#Section3

You could try that before combining using one of the above mentioned methods. I'm going to try this on my next processing attempt with some OSC + Ha data. My first attempt shows some of what you are talking about, i.e. some star color loss that is hard to get back. Here is a screen shot of, from left to right, RGB fully processed, Ha integration, RGB+Ha fully processed.




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General / Re: Inserting Ha into an RGB Image
« on: 2018 July 13 06:32:28 »


if the Ha requires upsizing then the two images have not been registered to one another.

rob

This touches on a similar question I asked in a similar thread. So registration does indeed take care of differences in scale between the two images to be registered? I've seen other workflows that mention both resampling and star alignment, but it seems one would negate the the other it terms of image scale.

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General / Re: Inserting Ha into an RGB Image
« on: 2018 July 13 06:05:09 »
There is also the NBRGBCombination script. I use it for osc and ha combination.

15
General / Re: DSLR RGB Ha Combination
« on: 2018 July 12 19:33:11 »
Thanks for the reply Alex. Thats an interesting take on drizzling. In my limited time in this field I've been working under the assumption drizzling was well justified for DSLR images, supposing a sufficient dither was used during capture.

For the below image I used Mike Oates' technique for the Ha image, and then combined using the NBRGBCombination script before going linear. I was not able to use CFA drizzle following Mike's steps, but did do a normal drizzle, despite the fact that I didn't have enough images to justify its use for the Ha data (more of an experiment). The results were ok, but I don't know if I really gained anything by debayering and splitting channels first, as opposed to processing normally and then splitting channels after integration. My instrument may not be fine enough to detect the difference.

Here is a side-by-side, from left to right, of the fully processed RGB (had to fix some star cores later), the integrated Ha, and the fully processed combination of the two. Feedback welcome, although its a low-res screen shot. I think the RGB can stand on its own, but it did gain significant detail from the Ha channel.


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