Conditions: acquired 3 miles north of Boulder, CO, on Apr. 27, 2004 with a moderately light polluted sky, around the beginning of Nautical twilight; ~10 deg. C, weak western wind, no clouds, good/average transparency. The altitude of Comet Linear during the exposures ranged from just 5-9 degrees; very low! Visually, I couldn't see a thing!!
Setup: Nikon 180 mm F4, DF-2 focusser, IR reject filter, ST10XE, MaximDL/CCD, Takahashi EM-10 mount (see a mechanical description and roadside view of this setup)
Exposure time: 27x25 sec. I just kept on imaging until the sky background was so bright that it got saturated!
Processing (Mira, Registar, Photoshop): dark subtracted, flat fielded, masked hot/cold pixels, subtracted bright sky background (3x3 polynomial fit in Mira, special (homemade) Mathematica software and a smoothed background in Photoshop. -The works!), registered, median/avr combined (in Registar), levels&curves, reduced 50% for web format
Comet Linear was a much more challenging object than comet Bradfield, visible this same morning. It was lower in a brighter sky and the tail
was more tenuous. The image certainly bears proof of this, looking more 'processed' than my image of Bradfield, taken just a few minutes
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