M42 first attempt

[D Wright]

This is my first attempt at M42. 20 x 30 second lights and 12 darks taken through 10" reflector on Vixen GP mount with no guiding using Canon 450D unmodified. The smaller image is taken with the same camera but with a Sigma 70-300mm lens at 250mm at f5.6. this is 10 x 30 second lights and 5 darks. Both stacked in DSS and processed in GIMP. I don't understand why I have got all the lines in the second photo. The only reason I can think of is that I was using a dew heater band on the same power supply as the mount and I don't know if this caused interference. I have this in my latest photos but not on the older ones with the same lens. Comments, criticism and advice greatly appreciated.

[Knight of Clear Skies]

Good effort. I suspect the pronounced banding in the second image may be due to the low number of darks, a small number can be worse than none as the noise isn't averaged out properly. I rarely bother with darks myself, a dither and kappa-sigma clip when stacking in DSS is very good at removing DSLR noise patterns. With an unguided mount you get a bit of dithering for free, especially if the camera isn't aligned along the RA and DEC axis.

[D Wright]

I would have done more lights and darks but my camera battery died on me. It was the third I used as I did quite a bit of imaging and Orion was quite late in clearing the trees where I was.

[Knight of Clear Skies]

Restacking without the darks may help if you choose a kappa-sigma clip. Ideally it needs more than 10 subs but I have used it with as few as eight, and it successfully zapped a satellite trail.

[MARS1960]

Thats a great first M42, much better than my first six attempts lol.

[Cozzy]

I can only echo what has already been said. Very good first attempt, keep at it and good luck/clear skies.

 

Tim

[D Wright]

Thanks for the posative replies.I think I will try again another time and take more/longer subs and more darks and by then I hope flats and bias too. I have successfully done 2 minute subs with the camera lens.

[alacant]

20 hours ago, D Wright said:

and more darks

Hi. Good effort. Nice shots. But no. As KoCS recommends, lose the darks. On Canon they seem to make more noise. So: light, flat and bias frames, yes. Darks, no. If you have APT it's a simple mod to add dither too. With that combo I find the noise really is minimised.

[D Wright]

The strange thing is on the first image taken through the scope I used darks and as you can see there is not much noise. I think with the second image as KoCS said I had too many darks for the amount of flats. I will endevour to take some flats and bias next time and try stacking without darks and see if it improves.

[cjdawson]

Don't forget to take a series of shorter subs too.  You've completely blown out the central region, the Trapezium is completely missing.    The trick to getting a fantastic M42, is to do a series of images with different exposure times.  Expose for the Trap, then for the brighter stuff around, and finally longer again for the feint stuff.    Then you combine the images together to give the illusion of a single image.  It's a HDR technique (one that I have yet to try successfully) but should result in a fantastic image.

In addition, I think the background if your M42 too black.  This is a sign that you may have clipped off too much colour.  In reality, the sky is never black, so be careful about clipping too much - as this is where that really valuable feint data is hiding!

[Starwiz]

Nice images.  

I hope to have my first proper attempt at M42 sometime soon.  I took a few test shots of it a few weeks ago, although not fully in focus the colours looked great.  

John

[wxsatuser]

Good start.

Basically in the larger image, with the short exposures you only caught the Trapezium plus the red Ha.
Much longer exposures will capture all the surrounding blue reflection nebula.
The Trapezium should be greenish, so if it appears green/blue you have the colour correct.

[Pete Presland]

A very nice start, love the wider field view as well!

[D Wright]

On 12/11/2016 at 00:22, cjdawson said:

 Then you combine the images together to give the illusion of a single image.  It's a HDR technique (one that I have yet to try successfully) but should result in a fantastic image.

How do you do this and which software do you use. I understand the principle but not how to do it. I noticed the centre was blown out when I processed the image. I will try different length subs next time I get a chance. I will try and increase the length of the subs to get more data.

[cjdawson]

5 hours ago, D Wright said:

How do you do this and which software do you use. I understand the principle but not how to do it. I noticed the centre was blown out when I processed the image. I will try different length subs next time I get a chance. I will try and increase the length of the subs to get more data.

You can use a program like Photoshop or The gimp.   Both should get you do it.

There are tutorials on the subject of focus stacking, or HDR, the techniques in those should cover you.  Effectively that you are doing is making a HDR image.     The technique done using by putting the long exposure on the bottom layer, then the medium photo as a layer on top, then the short exposure on top on it's own layer.  (Or might be the other way round) Then using the layer masking features, you cut holes in the image above to show through the parts of the longer exposure around the core.   One thing that you can do is rather than cut a hard edged hole, you can blend the edges of one image to the next.

[D Wright]

I have reworked the image using short exposure and used GIMP with a layer mask and in my opinion it is much better.