My dark nebula is too dark

[decay]

Glad that it worked for you now But I have one more question : Did you have an easier time using the Wipe module? Or were aggressive settings still necessary?

Dietmar.

[Stefan B]

I think you've uploaded the ASTAP stack again, as I just downloaded it and it shows the artifacts still.

Sorry, I shared the wrong link. This one should work: https://www.dropbox.com/scl/fi/ho4y8t66 ... x2xrl&dl=0

If you feel there's lack of signal or contrast (comparing to the other guy at astrobin ) I'd suggest analysing the subs and see specially hfr and star count( i find it easier to do this in DSS ). Could be some dog or thin cloud in some subs that might skew the stack. You might end up with less total integration time but better signal to noise ratio. (Unless you have already done that! Then ignore )

Yes, I usually define a star count threshold and delete all the subs with less stars (I see that in the file names given out by NINA). Then I go through all the subs one at a time and delete the ones with oblong stars etc. Before stacking all the subs get analyzed by ASTAP and I delete the ones with a significantly lower quality the score than the rest. I usually loose several hours of integration time but as you said - usually you end up with better SNR. My wife said that's a minimalist's approach: less data, better quality. Albeit you have to have a lot of integration time or subs to chose from in the first place.

Did you have an easier time using the Wipe module? Or were aggressive settings still necessary?

Excellent question I forgot to address in my prior post. My Wipe settings were basically the same as with the ASTAP stack. I am not sure if the colored patterns are even confusing Wipe or if the ASTAP stack has inferior quality in general and the fixed patterns are just another indicator of that.

I frequently notice that the rejection doesn't work from time to time with ASTAP. Often I have several satellite streaks in the stack. I then identify the individual subs and stack again WITHOUT these subs to get a clean stack. Strikingly, the streaks which make it to the final image are extremely bright so they should be easy to reject based on the standard deviation. Maybe the algorithm has problems with overexposed pixels since fainter streaks are robustly rejected.

With Siril I just left all in. I also didn't discard any of the subs because of low quality scores (don't know how or if that works in Siril). But the stack didn't have the streaks anyway. Moreover Siril stacked the 200+ subs in 35 min while ASTAP was calculating for about 4 hours I think. And then it had to do it again after I deleted the satellite subs.

Regards
Stefan

[Carles]

Thank you Stefan,

yes, Siril is quite fast!

Your stack seems already white balanced, as I opened it in either Siril or Startools and it doesn't show the classic all green from unbalanced datasets.
Did you select this on Siril when stacking? Still, it came out cleaner than the previous one. Altough same darker area on the right handside and some tilt.

A question though, do you use HGC or LGC with your camera? I see you use Gain 100 that'll be the equivalent to Gain 0, but is it HGC or LGC?

Asking because of the full well.

Glad you could sort it out anyway

Carles

[Stefan B]

Hi Carles!

Your stack seems already white balanced, as I opened it in either Siril or Startools and it doesn't show the classic all green from unbalanced datasets.
Did you select this on Siril when stacking?

I wouldn't even know where... Can I adjust parameters when using scripts? Cosmetic correction appears to be activated but this only addresses hot pixels if I understand correctly.

Still, it came out cleaner than the previous one. Altough same darker area on the right handside and some tilt.

Tilt is hit or miss for me. I guess it's the focuser. The OTA is really budget. Optics are fine but there are some parts that aren't really robust like the spider vane or the focuser. I tried to adjust for tilt via the focuser's screws and seemed to nail it for some images. But then you image a different part of the sky, the weight of camera, OAG etc drags in a slightly different direction and there it is again. So I live with that.

That the right half of the image appears darker than the left half is a feature not a bug, I guess. On the right handside is more dust blocking the stars compared to the left side. See the deeper image linked above: https://www.astrobin.com/eojxrd/ Or am I missing something here?

A question though, do you use HGC or LGC with your camera? I see you use Gain 100 that'll be the equivalent to Gain 0, but is it HGC or LGC?

For broadband I use LGC and for duo NB it's HGC. Though I am wondering if HGC would be a wise choice for dark nebula, too!? Lower read noise. And as far as I know you don't lose much dynamic range (https://www.cloudynights.com/topic/7472 ... p=10755632).

Regards
Stefan

[Stefan B]

Carles wrote: ↑Wed Sep 04, 2024 8:36 pm
Still, it came out cleaner than the previous one. Altough same darker area on the right handside and some tilt.

[...]

That the right half of the image appears darker than the left half is a feature not a bug, I guess. On the right handside is more dust blocking the stars compared to the left side. See the deeper image linked above: https://www.astrobin.com/eojxrd/ Or am I missing something here?

Or do you mean the massive gradient and that one part of the image is much darker than the other BEFORE Wipe? Then yes, it's still there. Maybe the gradient is just what it is...

For broadband I use LGC and for duo NB it's HGC.

That should be LCG and HCG. Actually I even know what that means but for some reason I have problems with acronyms at the moment. CMYK vs YMCK e.g.

Regards
Stefan

[Carles]

Hi Stefan,

That the right half of the image appears darker than the left half is a feature not a bug, I guess. On the right handside is more dust blocking the stars compared to the left side. See the deeper image linked above: https://www.astrobin.com/eojxrd/ Or am I missing something here?

all depends, how are your flats? I presume they'll be darker too on that side. I see what you mean by the FOV having more nebula on one side and kinda darker on the other but still. I think this can be a focuser misalignment or severe tilt.

About HGC and LGC or whatever, anyway High Gain Conversion Low Gain Conversion, you can swap the G and C still means the same

with HGC, you get less read noise and more e/ADU but at the expense of Full Well, specially, even it keeps the Dynamic range, for me, I rather have more full well. My friend who also has your camera uses HGC, because of noise.. but read noise can be cancelled out with many frames soooo... I rather shoot at 0 Gain with LGC, and keep my Full Well at max of, in my case, 71Ke approx. Why? Because the full well dictates how fast the pixell will get full or saturated. When in narrowband, Is kinda OK because the stars get dimished a lot, specially with l-enhance/Extreme/ultimate anda the likes. but for RGB stars can get really bright and bloated. That guy you're referring to on astrobin, also uses Gain 100 and your camera, but I wonder what HGC or LGC, because the little nebula by star SAO 12445 looks nic and with good contrast, so I guess he was able to controll more the "halo" of that star. Maybe LGC? Not sure.

I wouldn't even know where... Can I adjust parameters when using scripts? Cosmetic correction appears to be activated but this only addresses hot pixels if I understand correctly.

If you used the Scripts, as I do, which one did you use? with or withut bg extraction ? Because the script with bg extraction I think it does white balance , too. I use the simple OSC Processing script, or more often, OSC Processing without DBF , as I pre-calibrate my frames in DSS. on Siril's website there's a description on waht each Script does. https://free-astro.org/index.php?title=Siril:scripts

Regards,

Carles

[Carles]

Following the LGC and Full well topic,

this is a M45 image, around 8h and half, doing 600second subs from my Bortle 8-9, IR-UV filter. I believe, mabye i'm wrong, that keeping gain at 0 and LGC, can use the max full well to keep all Pleiades quite compact, and even was able to get Merope's Nebula, too.

m45.png (357.24 KiB) Viewed 8989 times

M45 -Merope's nebula.jpg (44.59 KiB) Viewed 8989 times

Cs,

Carles

[Stefan B]

Hi Carles,

all depends, how are your flats? I presume they'll be darker too on that side. I see what you mean by the FOV having more nebula on one side and kinda darker on the other but still. I think this can be a focuser misalignment or severe tilt.

The flats are darker on one side, but it's the opposite side The exact same flats were applied to my Wizard image (since I hadn't taken out cam or filter) and all was fine and I got an even field. The Wizard has also been basically gradient free before Wipe. I guess the conditions for the helping hand weren't ideal since it's a bit lower than the Wizard and sometimes street lamps are turned on in that direction.

I rather shoot at 0 Gain with LGC, and keep my Full Well at max of, in my case, 71Ke approx. Why? Because the full well dictates how fast the pixell will get full or saturated. When in narrowband, Is kinda OK because the stars get dimished a lot, specially with l-enhance/Extreme/ultimate anda the likes. but for RGB stars can get really bright and bloated. That guy you're referring to on astrobin, also uses Gain 100 and your camera, but I wonder what HGC or LGC, because the little nebula by star SAO 12445 looks nic and with good contrast, so I guess he was able to controll more the "halo" of that star. Maybe LGC? Not sure.

Gain 100 in LCG is the lowest possible gain with the Touptek 571s, they have no gain 0 AFAIK. The reference image wasn't taken with my camera model (Omegon/Touptek) but with ASI. It's different with ASI and obviously PlayerOne. I am not quite sure but I think that HGC kicks in on the ASIs when Gain 100 or higher is chosen (I've read that some people chose Gain 101 to make sure to be using HCG). So the reference image is probably done with HCG.

Really nice Pleiades by the way

Regards
Stefan

[Stefan B]

If you used the Scripts, as I do, which one did you use? with or withut bg extraction ? Because the script with bg extraction I think it does white balance , too. I use the simple OSC Processing script, or more often, OSC Processing without DBF , as I pre-calibrate my frames in DSS. on Siril's website there's a description on waht each Script does.

I used OSC_preprocessing so I guess without background extraction. Since OSC_Preprocessing_withbackgroundextraction.ssf wasn't preinstalled it hasn't been an option for me

Regards
Stefan

[Carles]

Hi Stefan

The flats are darker on one side, but it's the opposite side The exact same flats were applied to my Wizard image (since I hadn't taken out cam or filter) and all was fine and I got an even field. The Wizard has also been basically gradient free before Wipe. I guess the conditions for the helping hand weren't ideal since it's a bit lower than the Wizard and sometimes street lamps are turned on in that direction.

that's odd haha do you set up the gear each time or is the camera always in ? that might be it. Not sure if you use a clicklock or similar to center the optical train.


Yes, what I mean is that your Gain 100 is equivalent to my Gain 0. There is no 0 on touptek/omegon/risingcam, but that's just because they set it up this way, and still is similar. In the same way as my friend's and the cloudynight post, Gain 100 with LGC has 53ke full well, but as soon as you enable HGC, either with gain or selecting the mode, as my friend he's using HGC with gain 100 like you, and "low noise " mode or sth...but sill, the main difference is this. LGC Gain 100 , 53ke full well, HGC Gain 100, 17ke full well... so, basically the pixels fill up 3 times faster with HGC, and thus is usually recommended for short exposures, and LGC obviously benefits the full well for long exposures. To be honest, I never use HGC, I tried it once for Narrowband, to see if the SNR was better, and it didn't look to me much different. Maybe in s tacks... but then again is read noise the one lowering and that cancels out with many sub frames stacked so. I don't know. My friend insist using HGC for everything , it's his choice haha

all images you can see on my IG https://www.instagram.com/juskartes/?theme=dark have been done with gain 0 (or your Gain 100 ) and LGC. Even when mixing Propeller with l-extreme data. Both RGB and l-Extreme with LGC.

Maybe you can try it one day, perhaps with Alnitak for the Horsehead, and see if it makes any difference in bright stars. I surelly will hehe

Cs ,

Carles.