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  1. #1
    Senior Member
    BF Hammer's Avatar

    Orion in a wider-field

    I have had a plan for this since mid-December. I also have had many clouded and overcast nights, or moon interfering. Friday the 22nd a high pressure system finally parked nearby and we had clear skies, but freezing cold temperatures. The bigger problem was the moon was a little past first quarter and also very close to Orion. I took my chances anyhow.

    My secondary photo of a night landscape with Orion in frame (20mm lens planned for that at the local lake outside town) was thrown out the window as I figured the moon would ruin the nebulosity even more and Orion was already pretty high in the south sky when I started. This photo may need to be done in December or very early January.

    Primary photo was a go, Tamron 90mm f/2.8 mounted on D7000 for 135mm equivalent view. Mounted to my Skywatcher go-to tracking mount in EQ mode. I also attached a light pollution filter I have (150mm square-type, looked ridiculous adapted and mounted this smaller size lens) and used just a wired remote shutter release with a built-in intervalometer to automate the photo sequence. Plan was to have an hour or more of combined exposure, so set for 70-second exposures and 60 total exposures. Gave it 10 seconds of rest between images to clear buffer and settle.

    Since I scrapped the secondary photo plan, I made my first mistake and did not switch to using the D750 body. I kind of wish I shot a bit wider, but it may not have worked either with the moon. I had trouble getting polar aligned. Normally with the 150-600mm lens I just use live-view and center Polaris in the focus square. May have been some haze to the north, but I could not find any star in live-view on screen. Here is where the f/2.8 lens helped and I could just see Polaris in the optical viewfinder and pretty much get it centered. Score one for longer focal length. Focus was sort of a guess after I got the tracking mount re-aimed at Orion. I could actually see those stars on live-view. Did I mention it was about 10F right now and I was working at this for about 30 minutes. I had just charged the battery and it failed right before I was set to start taking photos. It may be my oldest battery pack because my replacement one did not give up. Then I had an error that forced remounting the lens. I hoped the alignment was still good. Verified a couple of test photos and refocused to finally begin. Then I retreated to my car and broke out the electric hand warmer. Still was cold as I waited out over 1 hour and 15 minutes for the sequence to complete.

    This was my first run at the photo right after getting home. It was created with Siril and GIMP and completed in 90 minutes from import of images to exporting JPG. Eh, it sort of looks rushed.
    Orion in a wider-field-orion_widefield_stacked.jpg
    D7000, Tamron 90mm f/2.8, ISO 2000, 60 stacked exposures of 70 seconds, f/3.3

    This afternoon I took another run with the file saved after stacking and worked more methodically.
    Orion in a wider-field-b_orion_stacked.jpg
    Same settings as above, just some different paths taken in post-processing. This version the Horsehead Nebula disappears for sake of blacker background.

    At this wide-field my hope was not only to catch the Horsehead Nebula at the leftmost star of Orion's belt but to also catch a bit of Barnard's Loop to the left of the field. I think the moonshine erased those. I may even consider doing this from an even darker sky location. My light-pollution filter was not problematic like it was in summer. It tended to fog up then, but now I have a lens warming wrap that plugs into a USB port for power. That seemed to work well. They are cheap enough I could consider getting another.

    Next version of this should be done with the higher-resolution D750 when the moon is not in the sky. That will be something I could do in about 12 days or later if weather co-operates. And with the D750 I will have the ability to control it with DigiKamControl by WiFi from inside of a car. I can micro-focus it remotely, adjust exposure settings, and keep warmer several feet away out of breeze. I think that would help a lot.


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  2. #2
    Senior Member
    STM's Avatar

    Re: Orion in a wider-field

    Well done!

    I am going to shoot the Flame and Horse Head nebulae tonight, cloud cover permitting.

    Perhaps you could have used the lasso tool with a fairly wide feather and selected around the Horse Head and Bright Orion Nebulae and then inverted the selection and blackened the skies so you retained the detail in the nebulae.

    Just a suggestion...........I hope you don't mind I took the liberty to see how well it worked.

    Orion in a wider-field-larson-image.jpg

    I would not worry too much about light pollution from the moon in the vicinity of Orion. I took this one the night before last of just M24 and NGC 1973-5-7 without a light pollution filter (I used a 400mm f/2.8 ED IF AIS on a D500) a bright 64% moon and got rid of any pollution with a couple of levels stretches, the "apply filter" and subtracting the background and some work with curves and the Camera Raw filter. It was like it was not even there. Feel free to drop me a line if you have any questions.

    Orion in a wider-field-m42-16x20.jpg
    Last edited by STM; 01-25-2021 at 12:12 AM.
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