A Re-Shoot of M42 and NGC 1973-5-7

I went out and re-shot the Bright Orion and Running Man nebulae last night with the D-500 and 400mm f/2.8 ED IF AIS Nikkor. I am quite happy with this one, though cutting my exposure to 0.5 second should, by the MFN calculation, which said 0.4 sec) eliminate star trailing but I still got just a little bit. I did not alter the colors at all, this is just what they looked like after 2 iterations of levels "stretching" in PS. The swirls of atmospheric dust and gases are amazing. Now I just wish my telescope would get here!

I am going to get this one printed 16x20!

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Originally Posted by BF Hammer

Nice, I was trying to shoot Orion last night with a wider-field 90mm lens. If there was no moon I think it would have worked a lot better. But it helps to be zoomed-in under those conditions.

I think I have decided to keep using Siril for the stack and initial exposure-stretching. I stacked 60 images (70 second exposures) and managed to have a workable photo in under 90 minutes of effort. I bet it would bring out the full circle of the nebula in your photo if you tried.

DSS has worked well for me, at least with DSO objects. For the moon I have just been using Zerene Stacker and it seems to work ok. I did break out the whole "ring" of M42 but since it was faint and I liked this crop better, I chose to go without it. I could have dodged it in PS if I had wanted to. Tonight I am going after the Flame and Horse Head nebulae with the D500 and 400mm f/2.8 ED IF AIS Nikkor. I got two Bahtinov masks in the mail a couple of days ago so I will use the one for the 400mm to focus on Regel to ensure the focus is perfect!

The moon will be a good source of light pollution tonight since it is supposed to be a waxing Gibbous with 79% showing, but two good stretches and subtracting the background noise out of the image using Apply Image and Subtract in PS works well. I finish things using Camera Raw filter and apply some darkening of the blacks, the dehaze filter and clarity filter and I can pretty much make all of it go away. What is still vexing is the slight star trailing. I go to a site which uses the complicated MFN calculation for calculating the maximum shutter speed to avoid trailing. The rule of 500 is outdated and to a great extent useless and no one I have talked with uses it any more. It might work if you are using very wide lenses but not with telephoto lenses. At first I thought it might just be coma, but that is only seen near the edges of the frame and not normally seen with lenses of this focal length so I discounted that. The MFN calc said I could use 0.7 sec so I went with 0.5 sec to be on the safe side but still got some. I am just going to have to wait until I get my telescope and az-alt mount and wedge (which turns it into an equatorial mount) to eliminate it.

This is the site if you are interested:
Société Astronomique du Havre - Règle NPF : temps de pose pour éviter le filé d'étoiles (archive.org) Microsoft Edge will translate the page because it is in French.

Something else that has helped me tremendously, not having a go-to mount yet, is this little sight I built out in the shop. It is made from some 1" Sch 80 PVC pipe and two pieces of clear 0.1" acrylic sheet. I made a "reticle" in PS and used it as a template to mark around the rear piece of acrylic with glow in the dark paint. The front piece only has 1 dot in it, that is the out of focus "blob" in the image lower right. With a long lens, trying to slew the camera to a small nebula is a pretty difficult task to say the least, but with this little $5 home made gadget, it is a piece of cake! Necessity is the mother of all inventions!