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Contains:  M 76, Little Dumbbell, NGC 650
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M76 Little Dumbbell Planetary Nebula in Perseus under 84% moon, 


M76 Little Dumbbell Planetary Nebula in Perseus under 84% moon

M76 Little Dumbbell Planetary Nebula in Perseus under 84% moon

Technical card

Resolution: 2572x1676

Dates:July 9, 2014

Frames: 21x90" ISO400

Integration: 0.5 hours

Darks: ~18

Bias: ~30

Avg. Moon age: 11.41 days

Avg. Moon phase: 87.76%

Temperature: 12.00 job: 316967

RA center: 25.590 degrees

DEC center: 51.567 degrees

Pixel scale: 1.090 arcsec/pixel

Orientation: -93.386 degrees

Field radius: 0.465 degrees

Locations: Suburban backyard N/O Seattle, Lynnwood, WA, United States


Full resolution crop of M76, the Little Dumbbell planetary nebula in Perseus taken a few nights before the July 2014 super moon. The moonlight almost washed out the dumbbell weights but the handle was quite bright. I reduced the contrast a bit to let the dumbbell weights show although that causes more noise in the background.

This shot was taken while testing the tracking. I did the PEC training the night before but needed to separate the OTA, mount, and tripod to store in the house and then set up again. Like the night before I did a polar alignment only using the polar scope but did not do a fresh PEC training. The tracking was not as good as the night before, perhaps because a different area of the sky was imaged. I reduced the exposures from 240 seconds to 90 seconds.

The drift was about the same as the night before: 1.21 arcsec/minute in the RA, 0.3 arcsec/minute in the DEC. Of the 21 subs, 6 separated the dimmer stars into doubles. I included them in the stack anyway to help make the dumbell nebulosity more visible. DSS appears to detect the trailed and false double stars and make them single and round anyway. I'm not sure if it was ignoring the bad stars or making them match the tighter ones.

Edit: My measurements assumed the RA axis and DEC axis were exactly vertical and horizontal, but the plate solve shows my image x/y coordinates to be 3.386 degrees off. If my polar alignment were perfect the apparent DEC drift due to camera orientation would be 1.21 x sin 3.386 = 0.07 arcsec/minute. My DEC drift either 0.23 arcsec/minute or 0.37 arcsec/minute depending whether I need to add or subtract the correction.



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M76 Little Dumbbell Planetary Nebula in Perseus under 84% moon,