4 hours on Elephant's trunk Nebula- no colors - Forums

Topic starter

May 14, 2021

I'm trying to figure out what causes that.
Last night and the previous night I shot the Elephant's trunk nebula , haven't added all the subs yet.
I only did a quick stack of last night, which were 210x 70 seconds exposures.
Sharpcap recommended me to take 67 seconds at gain 0 and offset 5 with its calculations for the ASI 533Mc Pro.
So I used NINA, and I am not comfortable with such a low offset so I always go with offset 50 so I won't clip the light.
As I just stacked the images (1hr 20 min stacking with darks and bias, no flats yet) with SiriL, The image has no colors even after I did a photometric calibration on the Elephant's trunk nebula.
This is the second time that I failed to get any results on this nebula.
I can understand not seeing much with 1 hour or 2 hours, but with 4.08 hours?
Should I be seeing something beside just some dark outlines of the nebula?
I feel like Sharpcap is giving me the wrong settings. I never used gain0 on this camera, not sure why it's recommending it to me to do that.
Most of my images made with gain 100 and 60 or 90s seconds, not gain0. I start to feel like I'm wasting a lot of time with wrong settings.
The telescope is 80mm F7 SV503 ( I know not the greatest but I successfully image other objects with it)
I'm at bortle 5.
Someone has an insight on this? Anyone with ASI533Mc pro and has it's "go-to"settings that I should try or start out with?
Thanks!

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Bruce Donzanti

May 14, 2021

The 533MC will work at gain 0 even though I always used it at gain 100. Did you debayer the images? If not, they will remain gray scale.

Michel Makhlouta

May 14, 2021

Gain 100 with offset 70 (unity gain and default offset) is what I use, and on paper it doesn’t make sense to use gain 0.

Even single frames should have colors. You need to tell your stacking software that the frames are CFA and it needs to debayer them, choose RGGB. I never used Siril, but with pixinsight and deepskystacker, you need to set this, it’s not there by default

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Ferenc Szabo

Topic starter

May 14, 2021

Bruce Donzanti:
The 533MC will work at gain 0 even though I always used it at gain 100. Did you debayer the images? If not, they will remain gray scale.

* Not that it's lacks colors completely , it has the star colors and some tiny bit red here and there but very tiny. Actually the stars look bloated, even with these settings.
I think i start to suspect that the light pollution filter is screwing things up. I just looked and I did image this before and used gain100 with 60 seconds and the subs looked good.
Ok, so I might have found the issue. The subs may be out of focus, the stars look bloated even though they shouldn't be .
I do have an autofocuser and it found the "best" focus point last night, but I suspect the LP filter won't let the camera fully focus.

Bruce Donzanti

May 14, 2021

Ok- if you have some color and stars look bloated, check focus as you say but also maybe you just need to do more histogram stretching and use of curves saturation. However, I have used LP filters with this camera with no problem. You may want to try a UV/IR which controls for star bloat.

andrea tasselli

Frequent contributor

May 14, 2021

The Elephant's Trunk is a very faint object that needs a lot of integration and a lot of stretching (or a lot of NB integration). At a glance I'd say you should use 100 gain FIXED and never change it. Dynamic range is the same (or nearly so) that at 0 gain and read noise much better (basically same setting of my 294MC). This should provide the boost you need to see a bit more of it. LP filter have nothing to do with focusing and in fact, if anything, they should provide sharper focus. Test the setting of best focus with a Bahtinov mask. Not sure I'd want to use one of the more selective of theLP filters around with Bortle 5 skies (I guess it's a toss) but you don't say which one you got. Also, it would help us help you if you would show a pic of what you got.

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Ferenc Szabo

Topic starter

May 15, 2021 · Edited: May 15, 2021

andrea tasselli:
The Elephant's Trunk is a very faint object that needs a lot of integration and a lot of stretching (or a lot of NB integration). At a glance I'd say you should use 100 gain FIXED and never change it. Dynamic range is the same (or nearly so) that at 0 gain and read noise much better (basically same setting of my 294MC). This should provide the boost you need to see a bit more of it. LP filter have nothing to do with focusing and in fact, if anything, they should provide sharper focus. Test the setting of best focus with a Bahtinov mask. Not sure I'd want to use one of the more selective of theLP filters around with Bortle 5 skies (I guess it's a toss) but you don't say which one you got. Also, it would help us help you if you would show a pic of what you got.

It's a cheap LP filter, I think it's not even for astrophoto but visuals. It's called ICE LIPO 2", and it has been causing reflection spikes of shiny stars looking like a photo of a flashlight directly into the camera. The filter was placed before the flattener (there is a threaded part on front of the flattener), not between the camera and the flattener. It's the second (and probably the last) time I used this, and only did it, because I've been getting very short exposure recommendations from Sharpcap, like 13 seconds per subframe, but I don't have enough hard drive space to shoot 13 second exposures and shoot thousands.
I'm gonna shrink a single sub, resample it in photoshop - and manually stretch it somewhat to see that this has to be out of focus. I have a Bathinov mask and use it, but this time I relied on the autofocus only.
Some water drops also seen, which is no concern after was gonna apply flats. So again, ASI533MC Pro gain 0, 70 seconds, offset 50. This is aimed at the Elephant's Trunk nebula center part.

Ferenc Szabo

Topic starter

May 15, 2021

Here is that flashlight spike effect I am talking about. The first time I used this filter.
This was from the Cave Nebula region and I don't have the subs anymore, but look for a aiming-reticule shaped cross on very bright star. I'm using a refractor so this shouldn't be there.

andrea tasselli

Frequent contributor

May 15, 2021

Having seen the image I'd reckon the focus is pretty good for what it is. The main issue here is that your ED refractor needs to have an UV/IR cut filter ahead of the flattener, as the picture shows unfocused light in the red end of the spectrum and a significant violet glare in the brightest stars. Since there is a considerable amount of chromatic aberration in both the near-IR and in the violet end of the spectrum if I were you I'd get myself a Baader Semi-APO filter which would resolve the issue completely and give you an extra filtering in the yellow/orange area of the spectrum, which improves contrast when LP is present. As I said before, with gain 0 is hardly surprising you can't see a thing. You would need to fully process the sequence to check the quality of the exposures. Plus, 70s is really not much on such a subject, you should aim at 180s at least to hope to catch up something in a single exposure. Or use binning.

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Ferenc Szabo

Topic starter

May 18, 2021

andrea tasselli:
Having seen the image I'd reckon the focus is pretty good for what it is. The main issue here is that your ED refractor needs to have an UV/IR cut filter ahead of the flattener, as the picture shows unfocused light in the red end of the spectrum and a significant violet glare in the brightest stars. Since there is a considerable amount of chromatic aberration in both the near-IR and in the violet end of the spectrum if I were you I'd get myself a Baader Semi-APO filter which would resolve the issue completely and give you an extra filtering in the yellow/orange area of the spectrum, which improves contrast when LP is present. As I said before, with gain 0 is hardly surprising you can't see a thing. You would need to fully process the sequence to check the quality of the exposures. Plus, 70s is really not much on such a subject, you should aim at 180s at least to hope to catch up something in a single exposure. Or use binning.

Hi! thanks for the advice! I assumed the LP filter would also act as an IR/CUT filter, so we don't have to stack filters on top of each other. I'm just gonna try to use a different type of LP filter or only use an IR/CUT filter and no light pollution filter. I could get away without any light pollution filter (only IR/CUT) while photographing the Whirlpool and the Pinwheel Galaxy, but those were nearly at the Zenith, while these nebulae are still low- north/northeast and I think the nearby city's light pollution and fighting the thicker atmosphere reduces a lot of details.

FiZzZ

May 19, 2021

Is a different camera, but with ASI294MM I’m going at
LUM Unbinned 180s gain 200 offset 20,
RGB bin2x2 120s gain 100 offset 10 and
halpha unbinned 300s gain 200 offset 20.

and I still struggle with details and colors
(I have a WIP elephant trunk nebula in my pics, is still in progress as it still rises late here)

to me you should greatly increase your exposure time and bin@2x2.

Ferenc Szabo

Topic starter

May 19, 2021 · Edited: May 19, 2021

Is a different camera, but with ASI294MM I’m going at
LUM Unbinned 180s gain 200 offset 20,
RGB bin2x2 120s gain 100 offset 10 and
halpha unbinned 300s gain 200 offset 20.

and I still struggle with details and colors
(I have a WIP elephant trunk nebula in my pics, is still in progress as it still rises late here)

to me you should greatly increase your exposure time and bin@2x2.

Yes, it comes to my field of view around 12am-1am so I can only shoot for max 3 hours. After 4am, it's already getting bright and those dawn- subs just gonna ruin the rest. And usually that 3 hours is only 2 lol, since I end up messing around before I start the sequence.
Thank! I did! Finally I feel like I'm getting somewhere!
I switched to my smaller Williams Optics Z61, since I want a wider field and put in another light pollution filter. (this one is very strong, but that's what I got)
I cranked up the exposure time to 300 seconds per sub, stayed on gain 100.
Yes, the blue stars are bloated a bit, but this was just a test-stack via Siril and didn't spend much time developing beside basic stretching and some de-noising.
\

https://cdn.astrobin.com/solutions/images/94750/2021/6c951bae-f1eb-4f74-95f5-0c73e6963329-1621456056.jpg

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