Crab Nebula (M1)

[alan4908]

My first attempt at the Crab Nebula.

The image is an LRGB with an Ha blend into the lum and red channels and represents about 14 hours integration time.  

Alan 

LIGHTS: L:14,R:16, G:8, B:14 x 600s, H:11 x 1800s.

[graemlourens]

Very nice Alain!

A very difficult target i found the Crab to be...

Kind regards, Graem

[tooth_dr]

Stunning, thanks for sharing.

[Barry-Wilson]

Ooohh, lovely image Alan.  Well balanced and natural processing.  Good job.

[alan4908]

1 hour ago, graemlourens said:

Very nice Alain!

A very difficult target i found the Crab to be...

Kind regards, Graem

Thanks for the comment Graem.  Yes, it is quite difficult - I was pleased that I managed to capture a bit of detail.

1 hour ago, tooth_dr said:

Stunning, thanks for sharing.

Thanks ! 

1 hour ago, Barry-Wilson said:

Ooohh, lovely image Alan.  Well balanced and natural processing.  Good job.

Glad you liked it Barry.  

[toxic]

that is a lovely rendition of the crab 

[coatesg]

A pretty fine first stab at the Crab it is too! Very natural and lovely colour.

What kit do you use?

[alan4908]

15 hours ago, toxic said:

that is a lovely rendition of the crab 

Thanks Chris. 

15 hours ago, coatesg said:

A pretty fine first stab at the Crab it is too! Very natural and lovely colour.

What kit do you use?

Thanks for the comment Graeme.

The equipment used was my Esprit 150 +FF with a SX Trius 814 CCD and 3nm Astrodon Ha filter, mounted on my 10micron GM1000HPS in unguided mode.

[Sam]

This is a fantastic image, I love the colour.

[MarsG76]

Nice result. excellent vein detail.

 

[alan4908]

22 hours ago, Sam said:

This is a fantastic image, I love the colour.

Thanks Sam.  Yes, I so do I 

13 hours ago, MarsG76 said:

Nice result. excellent vein detail.

Thanks. I think that the details where helped by my decision to keep only the best quality subs.

[MarsG76]

20 minutes ago, alan4908 said:

decision to keep only the best quality subs.

I thought everybody did that... I always keep the best subs...

[alan4908]

19 minutes ago, MarsG76 said:

I thought everybody did that... I always keep the best subs...

I used to do that but I subsequently found that it depends on the image and what I want to achieve - to explain: I often rely on data rejection to eliminate aircraft or satellite trails which I find can be removed without degrading image quality. I also sometimes keep subs which have been taken in poor seeing, if I want to maximize signal but I'm not too interested in details. If I don't have many subs, I've also found that by experimenting with different rejection algorithms, that you can keep subs with significant star aspect ratio distortion (and still end up with round stars) provided that you use an appropriate data rejection algorithm.  My key leanings on this subject came from watching Adam Block's video tutorials on image processing, which I would recommend.

[MarsG76]

9 hours ago, alan4908 said:

I used to do that but I subsequently found that it depends on the image and what I want to achieve - to explain: I often rely on data rejection to eliminate aircraft or satellite trails which I find can be removed without degrading image quality. I also sometimes keep subs which have been taken in poor seeing, if I want to maximize signal but I'm not too interested in details. If I don't have many subs, I've also found that by experimenting with different rejection algorithms, that you can keep subs with significant star aspect ratio distortion (and still end up with round stars) provided that you use an appropriate data rejection algorithm.  My key leanings on this subject came from watching Adam Block's video tutorials on image processing, which I would recommend.

If there is a satellite or meteorite streak through a sub, stacking will remove it... but if you're using subs where your stars are not round, "aspect ratio distortion", than that is a sign of motion blur effect in the reminder of the image softening out detail. I haven't heard of Adam Block or his methods so perhaps there is a trick to fox the motion blur, but to date I use stars in the center (or near center) of the frame to determine quality of the sub.

If the stars are round, no streaks or elongation than its a keeper otherwise I remove it. I find that by keeping only the best subs results in the best looking final image. If its too noisy or looks rough when stretching the stacked image than I just spend another night grabbing subs and re stack. Generally I end up with 40-50 subs of various lengths before I think I have enough data for good SNR and a relatively smooth image.  

Mind you though, I might end up with 2 or 3 subs that I delete in a nights session, and that's 3 at most on a bad night when something goes wrong with the tracking/autoguiding or the cursed clouds ruin it, and it's always on the 15, 20 minute or longer subs. So I don't cull too much data, rarely do I have a night where I spend a night of exposing subs where the seeing is so poor that my data is unusable.