M42 Wide Field

[symmetal]

Centre crop of my first 'proper' image from my RedCat51 and ASI071 one-shot colour camera. No ice on sensor this time.  Had two clear nights a few weeks ago and just got around to processing them. HEQ5 mount, ZWO mini-guide scope and ASI120MM guide camera. 

100 x 3 min subs, unity gain.

Stacked in AstroArt, processed in Startools and final tweaks in Photoshop. The darker bits are still a bit noisy so could do with some more subs. Distinct halos around the bright stars are also rather noticeable.  Whether this is the scope or the camera, I'm not sure. I could try the 071 with my ZS61 next time to see.

VdB 42, 46 and 54 are also visible in the image.

Alan

[Ceph]

Wow, that was a really nice picture Alan. As you say it is a bit noisy, I guess that can be improved. I guess it is the scope doing the halos, they seem to point out from the center on the edges.
I gets the same result with my refractor Astro Tech AT 65Q, but less on my mirrorscope and it seems to increase were there are dark dusts around, maybe I am wrong but that is what I found so far.

[bottletopburly]

Thats a lovely image well done .

[symmetal]

Thank you for the comments and 'likes' 

11 hours ago, Ceph said:

I guess it is the scope doing the halos, they seem to point out from the center on the edges.

I suspect you're right. My FLT98 and ZS61 don't give hard edge halos so was hoping the RC51 would be similar. I did use a Baader 2" UV/IR cut mounted in the RedCat. I can try another reprocess with less stretch and blend the halo stars in from that one. I probably wound the saturation back too much too to make the halos less obvious. The default from Startools was way over saturated. I'll have another go.

Not having any luminance, more subs will be needed to reduce the noise some more but the moon came up stopping me at the time.

The RedCat seems to hold focus throughout the night so a check at the start seems sufficient. I did check it again mid way through with the bahtinov mask but it was still good.

Alan

[alan potts]

And there was me worrying about using my 071 with a 330mm Borg scope, a stunning image indeed. Interesting what you say about ice, I had troubles with cooling too quick, been fine since I slowed down a bit.

Alan

[david_taurus83]

Lovely image. If you have Pixinsight theres a good trick for reducing background noise. Extract Luminance from the image and then apply as a mask. It covers the high signal bright areas and let's you apply a pretty heavy MLT noise reduction to the darker noisier areas. Not sure if Photoshop can do something similar.

[ollypenrice]

That's a lovely image.

Just over 3 Hrs is plenty for M42 but your image is much more ambitious than that since it goes after the faint outlying dust structures. More data would be a huge help.

43 minutes ago, david_taurus83 said:

Lovely image. If you have Pixinsight theres a good trick for reducing background noise. Extract Luminance from the image and then apply as a mask. It covers the high signal bright areas and let's you apply a pretty heavy MLT noise reduction to the darker noisier areas. Not sure if Photoshop can do something similar.

In Photoshop there are various ways to select just the regions you want for noise reduction but I think the easiest is the dead simple 'Colour Select' tool. Set the 'fuzziness' (the range either side of the specific pixel you happen to hit) to about 10 and then click on the regions containing the noise. You can then apply NR just to those selected regions but I wouldn't do it that way, I'd make a copy layer and apply a fairly heavy dose of NR to all of the bottom layer then go to the top layer and use the eraser at partial opacity to erase the noisy top layer in a series of passes till you have the right amount. None at all looks terrible. At any time you can ditch that selection and make a different one, perhaps concentrating on areas of really stubborn noise.

In my own widefield M42 I did pull down quite a few of the brighter stars but mine only had a soft kind of bloat. Here we see hard disk-like haloes which seem to go with the present CMOS cameras for some reason. Processing them out would not be at all easy so they are probably best left as they are?

Might be worth a few short subs for the Trapezium and this method for blending them? http://www.astropix.com/html/j_digit/laymask.html

You're onto a winner with this image.

Olly

Edited December 21, 2019 by ollypenrice

[symmetal]

2 hours ago, alan potts said:

And there was me worrying about using my 071 with a 330mm Borg scope, a stunning image indeed. Interesting what you say about ice, I had troubles with cooling too quick, been fine since I slowed down a bit.

I might have been better using my ZS61 at 360mm with the 071, as I cropped a fair amount off the RC51 image. This is the full frame view from Startools processing.

Keeping my camera in a sealed box with desiccant when not in use (most of the time ) seemed to have solved the icing problem which this camera is prone to.

1 hour ago, david_taurus83 said:

Lovely image. If you have Pixinsight theres a good trick for reducing background noise. Extract Luminance from the image and then apply as a mask. It covers the high signal bright areas and let's you apply a pretty heavy MLT noise reduction to the darker noisier areas. Not sure if Photoshop can do something similar.

Thanks David, I don't have Pixinsight but am fairly happy with using levels and masks in PS so will try what Olly has suggested.

1 hour ago, ollypenrice said:

In Photoshop there are various ways to select just the regions you want for noise reduction but I think the easiest is the dead simple 'Colour Select' tool. Set the 'fuzziness' (the range either side of the specific pixel you happen to hit) to about 10 and then click on the regions containing the noise. You can then apply NR just to those selected regions but I wouldn't do it that way, I'd make a copy layer and apply a fairly heavy dose of NR to all of the bottom layer then go to the top layer and use the eraser at partial opacity to erase the noisy top layer in a series of passes till you have the right amount. None at all looks terrible. At any time you can ditch that selection and make a different one, perhaps concentrating on areas of really stubborn noise.

In my own widefield M42 I did pull down quite a few of the brighter stars but mine only had a soft kind of bloat. Here we see hard disk-like haloes which seem to go with the present CMOS cameras for some reason. Processing them out would not be at all easy so they are probably best left as they are?

Might be worth a few short subs for the Trapezium and this method for blending them? http://www.astropix.com/html/j_digit/laymask.html

You're onto a winner with this image.

Thanks Olly.

Good idea about applying NR to the whole image and layer masking back in the areas that need to remain sharp. I had done that applying sharpening to just the bright areas, but will have another go.

My ASI1600 mono doesn't seem to produce such hard edge halos like this so was wondering if OSC may be more prone. The 071 front glass is fairly close to the sensor which may not help in that respect.

I did take some 20sec exposures for the Trapezium but hadn't added them into the image yet. I'll try that next. 

Alan