StarTools

Hi all,

since I was often annoyed by missing reds with my unmodified EOS 2000D, I decided to do a full spectrum modification (please see below). And I also bought an L-eNhance duo-band filter to get access to all those beautiful nebula targets.
For first light, I headed for the Western Veil. Everyone here was talking about it and so I wanted to see it with my own eyes - ahem – camera.
- 200/1000 GSO Newton / SkyWatcher EQ-5
- Baader MPCC
- L-eNhance
- EOS 2000Da, APT
- 50/200 Guide Scope, ASI 120 MC, PHD2

- 22 x 240s @ ISO 1600 (~ 1.5 hours)
- flats, bias

Unfortunately it rained the day before and after some time there was a lot of dew – on the scope, the camera, the notebook – everywhere. And I assume, there was also dew on the secondary mirror and this causes the big halo 52 Cygnus shows. But I’m quite happy with this image, nevertheless.

I underestimated how much light the duo-band filter cuts off and I had to prolong exposure time from 90s to 240s and ISO setting from 800 to 1600. I was afraid, that this would cause troubles with increased noise (particularly together with high temperatures here in Europe right now), but that was not the case, as far, as I can see.

The processing with ST was some kind of first light for me too. But ST is awesome, it gets better, the more features I use. I used Compose module for the first time and bi-colour processing worked like a charm. Simply great . I don’t know, why the OIII regions are green and not blue, but I will figure it out And the SVDecon module once again did a great job for clarity and tightening the stars.

Regarding the astro modification I read a lot about it on CN and other sites (Gary Honis) and it took some time for me to decide to try it, because I was afraid of breaking the camera. But then I found the video of this guy here and it helped me a lot:

https://www.youtube.com/watch?v=0omuDroX7Tk

Since he speaks French, I did not understand a single word. Maybe I should have learned French in school and not Latin But it was no problem at all. The most difficult part was the adjustment of the sensor. It is adjusted with 3 screws and I was afraid to tilt it. I marked the screws beforehand and as far as I can judge, I reassembled it without noticeable tilting.

Anyway it took 3 hours for me to accomplish it and afterwards I felt pretty burnt out. Decades have left their mark on me …
Best regards, Dietmar.

Hi Dietmar,

awesome result! Looking at your image I notice several features which I really like and on which I have some questions Good amount of stretching...did you use a Autodev with a certain ROI or Filmdev? I also like the well controlled star field - is this a ST only image or did you also include Starnet in your workflow? And the neutral star colors...the HOO stars from duo NB filters often have a very teal like color which I personally do not like very much. Did you tweak the star colors in a particular way or where they like this out of the box?

Your stars are nice and round by the way. 4 min subs obviously were no problem for your mount

decay wrote: ↑Wed Aug 03, 2022 12:34 pm I don’t know, why the OIII regions are green and not blue, but I will figure it out

Light from OIII is detected by the blue and green pixels of your sensor so the teal color is a reasonable result. Some people (like me) like their OIII rather blue and push it that way. Since your duo NB data isn't a "true" (visible spectrum) image that would be legit in my eyes. But if you like the teal color in the Veil that's also totally fine I guess

And congrats to the modification! I bought my DSLR second hand and it has already been modified. I wouldn't have dared to do it myself...

Regards
Stefan

Excellent job on the mod. I did the same to create my f/s D5300.

Too bad on the fogging-over dew halo, as otherwise ST usually does an excellent job keeping 52 Cyg under control.

If you look at graphs, OIII is pretty much right up the middle of blue and green and so...teal. But, this is really a form of narrowband, so you can alter it in many ways, as long as you maintain just two hues, of course.

The bicolor composite blends the B and G into a single file and stuffs it into both the B and G channels, as you know. So the 50/50 bicolor of HOO, which you could also think of as R(GB)(GB), is...teal.

I suppose you could composite it differently? If I were to do so, I think I would do a bicolor composite of just the (2xG)(B), don't load red, mono, and save that linear file. That now has all the pixels for OIII that you captured. Then compose again with the full file in the red, and the new OIII in the blue, leaving green blank. Normal compose now, not bicolor. I think that might work? Then in Color module just keep things straight up, no bicolor matrix, though you could manually move the other settings to be more like you would in bicolor, at least to start out. So drop back the bright and dark saturation, perhaps change to artistic, and RGB ratio, and also maybe some highlight repair.

The only part I would be unsure of, in both operations, is the setting for color channel interpolation on/off. You'd think I would understand that by now but I only kind of do.

Hi Stefan,

thank you for your reply and for your kind words

I used AutoDev with ROI like so:
And I dropped Shadow Linearity down to 25%.

But finding the right curve is sometimes still a problem for me and so I did a little postprocessing with darktable – but only level and colour corrections:
As for the star field I was surprised as well, particularly after I read about the struggles you had. No special processing. As I wrote, SVDecon did a great job. And I only used default preset “tighten” with Shrink module. Your image is deeper than mine – due to longer integration time and a darker sky, I guess. Maybe this causes the problems as you simply captured much more stars then I did?!

I do not use Starnet++ usually. Especially after I removed the main star of M27 out of our space-time continuum. I felt bad and a bit guilty and I’m still wondering if using Starnet++ is the dark side of the force and if so, how much …

As for the neutral star colours – I read about the teal co loured stars but I was surprised that this was (at first) not the case for me – I thought that this would be another kind of magic which Ivo implemented in bi-color processing workflow. Maybe you could try and do a run with your NB data stack only?

At my second run I dialled in much more colour and in this case some teal halos were visible – so I used a star mask and desaturated the stars with a second run of the Color module. For now white stars are fine for me, I will practise later on combining RGB data.

Best regards, Dietmar.

Hi Mike, thank you

Once again you left me speechless . I just started with narrowband processing and I was pretty proud that things went that well for me. And now I must try to understand what you wrote down. Joking aside, thanks for that, I will try to follow your suggestions, but right now I think I need to learn a lot more first.

Best regards, Dietmar.

Hi Dietmar,

Well it wasn't so much suggestions as just some more of my theorizing-on-the-fly. I tend to do that.

But I did some experimenting tonight with one of my Ha and OIII files from Panel 1 of my Cygnus Loop, i.e. the Western Veil portion. Indeed, putting the OIII only into B can give you a stronger blue than the lighter blue, heading towards teal or cyan, that maybe happens in bicolor HOO composite and mapping.

You do have to watch the green channel though, to put it in just the right spot so that you have red and blue. Otherwise you can greenerize or purpleize the whole image.

EDIT: Oh and I finally took a closer look at your post above and the clip of the AutoDev ROI -- nice! That is almost exactly the same ROI that I have always used with the Veil! Sometimes I include that little star up to the left too, but in any event, my rectangles are usually very close to that.

I'm pretty sure it was the Western Veil and 52 Cyg, a year or more ago, when I realized you sometimes just have to find a way to include the brightest and baddest star inside the ROI, in order to keep it under control.

Mike in Rancho wrote: ↑Mon Aug 08, 2022 7:14 am I realized you sometimes just have to find a way to include the brightest and baddest star inside the ROI, in order to keep it under control.

Yes, I think it's a good sign when two guys independently come to the same conclusion ?! Unless both have made the same mistake .

Mike in Rancho wrote: ↑Mon Aug 08, 2022 7:14 am just some more of my theorizing-on-the-fly. I tend to do that

Yeah, I already suspected that . But I'm just jealous. I would do the same if only I could, but with my limited English skills, every sentence is a time-consuming endeavor - nothing-on-the-fly.

And thanks for the additional remarks regarding the colouring. I will consider that all, when I reached that point, and then I will report back.

Best regards, Dietmar.