First go at North America nebula untracked

[Bluesboystig]

Hi everyone, 

Together with a friend we had a go at trying to shoot the North America nebula, completely untracked. We made so many mistakes it's unreal  1000 x 1s lights (no darks, bias, flats, because.. I don't know why..), with a Nikon d810 at 50mm. Now, with hindsight, we could have pushed probably much longer exposure times, but we were worried about star trailing. So I think that the final result is a consequence of having not a lot of exposure time per each frame after all. It's all part of learning, but I'm beating myself up so much, we could have used the night much better. I have tried my best with GIMP but I can't get much more out of the stacked file. Not sure if you have any tips/hints? 

Cheers!

Simone

 

[adyj1]

Have you heard of the 300 rule? (or 500 if you have a full frame). Divide 300 by your FL to get a rough approximation of exposure without trailing. So 300/50 = 6 seconds. It is more of a guideline than a rule, so zoom in on a test exposure to check for trailing/eggy stars and adjust accordingly. It is definitely worth spending a few minutes checking this (and focusing at the same time) as the results will be much better. 

[Bluesboystig]

54 minutes ago, adyj1 said:

Have you heard of the 300 rule? (or 500 if you have a full frame). Divide 300 by your FL to get a rough approximation of exposure without trailing. So 300/50 = 6 seconds. It is more of a guideline than a rule, so zoom in on a test exposure to check for trailing/eggy stars and adjust accordingly. It is definitely worth spending a few minutes checking this (and focusing at the same time) as the results will be much better. 

I did, but with 4s exposures we were noticing trails, so we reduced to 3s, then 2s then 1s. I hindsight, we where zooming in quite a lot to check for trailing, so that might have been one of the problems.. Do you think it's out of focus as well? 

[Rossco72]

It's really hard to say if it's in good focus as there is sooo much coma, or it looks like coma to me from your lens.

The good news is that it is there, and you can see it, but I think the 1s exposures probably won't have helped you much.

Did you keep the camera still for the entire 1000 shots or reframe after each 50 or so?

 

[Bluesboystig]

3 hours ago, Rossco72 said:

It's really hard to say if it's in good focus as there is sooo much coma, or it looks like coma to me from your lens.

The good news is that it is there, and you can see it, but I think the 1s exposures probably won't have helped you much.

Did you keep the camera still for the entire 1000 shots or reframe after each 50 or so?

 

No, stupidly I thought we wouldn't need to do that at 50mm... all part of the learning curve.

[Felias]

It's not too bad, actually, you just need to get rid of the light pollution. A simple background extraction with Siril, and the most basic arcsinh stretch with Photoshop yields this:

It's definitely there, and you should be able to get a better result departing from your original tiff or fits file, instead of the jpg I have used. It looks like there's coma in the stars, though, so worth checking your lens. And do not be afraid of longer exposure times, it's not too bad if there's a bit of trailing. I did this 50 mm with 8-second exposures, you gain more than you lose by letting the stars trail some:

 

 

[Bluesboystig]

1 hour ago, Felias said:

It's not too bad, actually, you just need to get rid of the light pollution. A simple background extraction with Siril, and the most basic arcsinh stretch with Photoshop yields this:

It's definitely there, and you should be able to get a better result departing from your original tiff or fits file, instead of the jpg I have used. It looks like there's coma in the stars, though, so worth checking your lens. And do not be afraid of longer exposure times, it's not too bad if there's a bit of trailing. I did this 50 mm with 8-second exposures, you gain more than you lose by letting the stars trail some:

 

 

Nice result! The learning curve with Siril + GIMP is steep, but definitely worth climbing! Your result on my file looks really good (I was working from a TIFF and exported the final result as a JPEG), actually impressive compared to what I was getting. Thanks for the pointers, really appreciated.

The photo you linked is an absolute masterpiece though, I'm absolutely amazed! I hope one day I'll manage to get something even half that good! 

[Felias]

5 minutes ago, Bluesboystig said:

Nice result! The learning curve with Siril + GIMP is steep, but definitely worth climbing! Your result on my file looks really good (I was working from a TIFF and exported the final result as a JPEG), actually impressive compared to what I was getting. Thanks for the pointers, really appreciated.

The photo you linked is an absolute masterpiece though, I'm absolutely amazed! I hope one day I'll manage to get something even half that good! 

Siril should be easier if you follow the tutorial step by step: https://siril.org/tutorials/tuto-scripts/

And thanks, but the only trick to that photo was a dark sky, honestly!

[Elp]

If you do the green noise removal in Siril too it will remove most of the unwanted green. GIMP is actually quite decent, tried it earlier today with some data I did earlier in the year struggling to eeek out faint nebulosity, GIMP did it well as I could process in 32 bit floating point mode (higher bit mode, more shades of colour/grey values that can be defined). It's why you should also always process tif/fits type files prior to saving a final output into something like a jpeg for smaller file sizes.

[900SL]

D810 at 6 seconds and don't pixel peep. The high resolution sensor will show very minor trailing at 150% but it's unnoticeable at full image. I have a D610 and shoot at 12-15s at 20mm, or track. The 500 rule is for older full frame cameras. A 300 rule is more appropriate 

[ollypenrice]

Another Photoshop trick, which might be available in GIMP, is to go into Image-Adjustments-Selective Colour and lower the cyans in red. This boosts signal from Ha in the red channel.

Olly