Crescent Nebula DSLR Woes

[imakebeer]

2 hours ago, Elp said:

Maybe post an image of your imaging train and rig if you can please.

As far as I recall for the moment, the DSLR is simply connected directly to a SkyWatcher Coma-Corrector and I've now screwed the 2" L-eNhance filter onto the end of that.

Don't want to dismantle it for the time being as I want to have another go at taking some flats.

[Elp]

Are you positive no stray light enters the front of the scope whilst imaging? I'm wondering whether the shadow is from the secondary mirror/assembly.

[imakebeer]

4 minutes ago, Elp said:

Are you positive no stray light enters the front of the scope whilst imaging? I'm wondering whether the shadow is from the secondary mirror/assembly.

Nope 🤣

Typically the scope is in the garden looking south(ish) over my house, moving to SW(ish) through the night 

The moon will be the moon. No direct line of sight to street lamps to the front of the house. 

Lights from neighbours are typically off, as are the lights in the rooms at the back of our house.

I think I'm doing everything I can to minimise stray light, certainly it's not like someone is shining a torch down the scope. 

Unless the squirrels are (a) nocturnal and (b) equipped with torches 🤣

[alacant]

35 minutes ago, imakebeer said:

look visually similar to yours when viewed in Siril with the viewer mode set to "Histogram"

OK. I think I've found it.
They are way over. Aim for a maximum ADU of ~8000. Then they will correct. For example, using the same light source as your 2.4s frames, Instead of 2.4s, try 0.5s.
Or, better keep your 2.4s and block the light until you get the correct ADU.

The theory of what should work breaks down with older Digic firmware. We gave up on trying to explain anything in AP many full moons ago. Hands on and experimentation is the only way!

35 minutes ago, imakebeer said:

How do you get Siril to tell you the ADU

You just did it...

Edited September 30 by alacant

[imakebeer]

35 minutes ago, alacant said:

The theory of what should work breaks down with older Digic firmware.

So are we kinda saying that:

• Normally, with a more modern DSLR for example, we want the peak of the histogram in our flats to be roughly in the middle
• But for some reason, because the 450D is older, this assumption breaks down and we need to reduce the exposure such that the histogram peak is much further left???

So presumably ADU is some sort of measure of the intensity or brightness in an image???

Awesome work Columbo, I will have another bash at the flats 👍🙏

Edit: Why 8000 ADU? Is this an arbitrary number or does it stem originally from powers of 2, e.g. 2^13 = 8192 ?

Edited September 30 by imakebeer

[alacant]

20 minutes ago, imakebeer said:

Why 8000 ADU?

Because it works.

My boss labels AP: El Arte del pragmatismo extremo.

(Art of extreme pragmatism perhaps?)

Edited September 30 by alacant

[imakebeer]

1 minute ago, alacant said:

Because it works.

My boss labels AP: El Arte del pragmatismo extremo.

(Art of extreme pragmatism perhaps?)

Muchas gracias chico - mas o menos yo se lo que significa 😂

BTW I think I found the answer to my question here:

https://theskysearchers.com/viewtopic.php?p=64155&sid=f4d617739976678018793ff2ca174e1e#p64155

450D has 14-bits => well depth of 16384, but you want it to be about half full or a bit less, so more or less ~8000.

[alacant]

4 minutes ago, imakebeer said:

so more or less ~8000.

¡Solucionado!

[ollypenrice]

31 minutes ago, alacant said:

Because it works.

My boss labels AP: El Arte del pragmatismo extremo.

(Art of extreme pragmatism perhaps?)

I certainly agree with this.

Olly

[imakebeer]

OK, new flats done - I ended up with 20 x 3s exposures which is giving me about 4500 ADU (mean value) instead of >20000!!!

And wow! I still need to run this starless image through Graxpert to de-noise it before I take it into GIMP for final histogram tweaks etc, but wow! I can already see there is more detail in there so I'm excited to see how this will look after some final tweaks 😁 (you can just about make out that little soap bubble at bottom left of the image)

Thank you @alacant , great detective work. I think I understand now what I need to be aiming for with my flats with and equipment setup going forward 👍

[TiffsAndAstro]

that's really cooling getting the soap bubble. was it a full moon when you took your lights?

the brain itself looks really nice, lots of detail and crenelations and clearly two blue bow shock waves but the clouds/Ha looks like when i take images (of some, not all targets) in strong moon light.  sort of a bit faded?

also, did you run any background extraction before/after removing the stars? if not, that may improve things even further. As you brain looks nice and detailed, im surprised your cloudy/more nebulous parts don't also

[imakebeer]

@TiffsAndAstro 27-28 Sept, maybe half moon, can't remember...

It might just be I need more time on the clouds. They do look a lot better in the denoised image so it might just be noise you're seeing??? I'm interested to try Ha & OIII extraction in Siril to see if that being anything extra to the party. 

I stack in Siril, then background extraction with GraXpert, then back to Siril for some more tweaks. Then I run Starnet in Siril to separate the stars. Then back to GraXpert to denoise the background, and finally GIMP for final tweaks.

 

[TiffsAndAstro]

2 hours ago, imakebeer said:

@TiffsAndAstro 27-28 Sept, maybe half moon, can't remember...

It might just be I need more time on the clouds. They do look a lot better in the denoised image so it might just be noise you're seeing??? I'm interested to try Ha & OIII extraction in Siril to see if that being anything extra to the party. 

I stack in Siril, then background extraction with GraXpert, then back to Siril for some more tweaks. Then I run Starnet in Siril to separate the stars. Then back to GraXpert to denoise the background, and finally GIMP for final tweaks.

 

Sounds right from here. I'm just surprised your brain looks so good while the clouds are a bit vaguer

[imakebeer]

Right, here we go - I've done a bit of stretching in GIMP. Honestly I've been staring at this thing for so long now I genuinely don't know what to think anymore 🤣

I cut the blue a bit as it was looking a bit magenta, but looking on my phone I think it might be a bit orange now.....

[TiffsAndAstro]

The brains Orange parts look a bit bloomy, now, but the brains blue bow waves things look even better than before

Also those clouds look a lot better. Some 3dness in top right hand corner.

Definitely progressing.

[alacant]

4 hours ago, imakebeer said:

background extraction with GraXpert, then back to Siril for some more tweaks

Hi
To save time, maybe try the latest version of Siril which has grx integrated?

[TiffsAndAstro]

1 hour ago, alacant said:

Hi
To save time, maybe try the latest version of Siril which has grx integrated?

Wtf? I try not to upgrade software until (being polite here) others have tested it.

Off to upgrade now ty

[imakebeer]

I've looked before and was looking again earlier - I can't see where you can access this development version ☹️

(but yes it would be jolly handy to incorporate GraXpert into my Siril process, similar to Starnet.....)

[TiffsAndAstro]

2 hours ago, alacant said:

Hi
To save time, maybe try the latest version of Siril which has grx integrated?

sorry to have to ask - how are you accessing grx from within siril like starnet? Scripts? I can't see it at all anywhere. Do i have to integrate it with siril, or have it up and running before i run Siiril? 

Edited October 1 by TiffsAndAstro

[imakebeer]

I assume it will work a bit like Starnet and you'll have to define somewhere in Preferences where the executable is.

Meanwhile in other news - slight tweak to the core, I think I'm happier with this:

[alacant]

47 minutes ago, imakebeer said:

where you can access this development version ☹️

Try here.

HTH

[alacant]

6 minutes ago, imakebeer said:

happier with this

Stunning blues. The 450 does particularly well in this part of the spectrum.

[TiffsAndAstro]

49 minutes ago, imakebeer said:

I assume it will work a bit like Starnet and you'll have to define somewhere in Preferences where the executable is.

Meanwhile in other news - slight tweak to the core, I think I'm happier with this:

I like this a LOT. Looks really really good

[TiffsAndAstro]

46 minutes ago, alacant said:

Try here.

HTH

Er thanks but is there a download/package? doubt i can compile this myself

[alacant]

53 minutes ago, TiffsAndAstro said:

doubt i can compile this myself

?

The method is given in the link I sent. It builds in under a minute. On Linux at least.

The idea of open source is that we all get involved. Report back, make suggestions, make translations, document the project, test new stuff, have a say...

Cheers 

Edited October 1 by alacant