M42 from last night - pointers please.

[volcanotop]

Hi Folks,  

Just starting to get the hang of astrophotography.

I think I’ve  nailed the polar alignement routine and phd2 guiding with a lodestar and a Canon DSLR.

The link below is M42 from last night. 75 lights 60 sec @ iso 800 / 15 darks.  Canon 500d astromod. Astronomik CLS clip.

I’ve got Bortle 8 sky and am a novice at the stacking, processing part, removing light polution part.

This image was DSS stacking and GIMP processing.

Happy to hear constructive criticism to help me improve.

https://astrob.in/full/8lxz20/0/

thanks!

[dannybgoode]

Nice image. Much better than the beat M42 I’ve managed. 
 

Only tip I’d give is to take some shorter exposure frames to blend and try and tackle the core so it’s not so blown out. 

[vlaiv]

Very nice start and I completely understand your urge to stretch image as much as you can, however, my advice would be not to do it.

There is certain draw to match what can be seen in images found online with your own data and that drives people to push their data too much. It can become habitual thing and it is hard to later "relearn" to stretch data only to the point it will let you.

You should aim to have your image relatively noise free even before you start denoising part of your processing. Be also careful of where you set your black point, in fact, there should not be a single pixel with 0,0,0 in your image - as even natural sky without any LP is not completely black.

[wimvb]

Great start. You seem to have focus and tracking under control. Once you have good data, you can process it as many times as you want, and improve as you learn.

I agree with @vlaiv that you should try to avoid clipping the background, but I wouldn't go so far as not having one single pixel clipped in the final image. Avoid clipping while you process. Then at the very end of processing, bring the general background level down with a curves stretch, using an S-curve, until you get a pleasing image. 

Your image seems predominantly red. Early on in your process, look for an "empty" background area and line up the histograms for red, green and blue. You can compare your image to an image you found online to determine a suitable area.

One of the reasons you image looks red is that most of your noise seems in the red channel. There is really only one good method for noise reduction: get more data. If you have light pollution, you have to compensate for that by increasing the total integration time.

As for the core of M42. It is very tricky to keep that under control while lifting the outer regions. What does your unstretced image look like? Are the 4 stars that make up the trapezium in the core of the nebula visible? If so, then it is possible to stretch the image to show both the core and the fainter areas. But it's going to be difficult. And I have no idea how to do that with GIMP. If the core is blown out, there's no way to rescue it, other than with new data. 

Have a look here:

That image used 50 20 second subs. 

[volcanotop]

Folks,

Thanks for the suggestions and pointers.    I'll try again with the stacking and processing 🙂   I'll try to be  bit less eager on the stretch and more care with the colour alignment.

On the noise and surplus red in the image.    My camera is a pretty ancient Canon 500d (astrmod)  so I'm sure some of the noise is from there?  i'd also assumed that some of the red was the remnants of light position that I've not processed properly?    I've got Bortle 8 sky at home and was imaging M42 when it was over Manchester Airport!

If anyone fancies some data processing on a cold wet cloudy night and showing me what a good image from my raw data could be then the 75 lights and 16 darks are shared below.  it would be really interesting to see what someone who has some processing skills can make of this data Vs my 'learner' attempt.

https://drive.google.com/open?id=1w1-ibf9EqrFjW68OPjwDEmb0L13d8_fM

anyway as i said i really appreciate you giving the pointers...

 

 

 

[wimvb]

Those zip files are rather large. Lights.zip now at 1.3 GB and loading ...

[wimvb]

Some careful stretching later:

[volcanotop]

Wow.  that’s nice. MUCH better than my effort.    Many thanks Wim.

Now i know what i’m aiming for!

Edited December 22, 2019 by volcanotop

[bottletopburly]

Stacked files using Siril  used the script No Flats , file is a Fit file but if you want a Tiff then load fit in DSS and save as tiff ,saves having to download big files 🙂 Had a quick play in Startools, now all you need is to take Flats and you will see a difference with cleaner images 

note Siril invert image  should have flipped it in Startools 

 

result.fit

Edited December 22, 2019 by bottletopburly

[volcanotop]

Hi,  thats a really nice job too.

i can see i need to brush up my processing.

i am pleased that my data/camera/tracking etc are good enough for this kind of image.

 

[spillage]

Much better than my first attempt. It maybe my monitor but can I see walking noise in picture? just wondering if you dither?

[wimvb]

No walking noise. In fact, almost no drift at all between exposures. Very accurate tracking. 

[volcanotop]

Yep i’ve got PHD2 set to Random dither.

Tracking / guiding is via an original lodestar and a TS OAG T-ring combo attached to the 500d.

i did experiment with a guidescope but that wasnt so good.   PHD just seems to nail the guiding with an OAG. For me anyway.

Edited December 22, 2019 by volcanotop

[Kevin Francis]

Very nice work! I was going to comment about the need to reduce noise in your photo, but seems you have that advice already.  I see that you used GIMP to post process.  Great choice.  Here's a good video on how to process using GIMP.   Good Luck and great start.