NGC7635 Bubble Nebula in Red Light from 18" Cassegrain with fog but great seeing

click image to enlarge (1.8-2.1 arc-sec seeing, but foggy)

shot on November 15, 2004 from my backyard in Castro Valley, Ca. under superb seeing conditions but with fog diminishing the nebulosity (boo hoo). I measured some stars with FWHM as tight as 1.6 arc-seconds and the average was close to 2 arc-seconds. So the stars are tight but the nebulosity is weak due to transparency problems.

Compact Collapsible Cassegrain 18" @f/12.6 (F=5760mm)

IMG6303E camera @-35C

AO7 @ 16 Hz

RCOS Dichroic beam splitter

ST7E guide camera

FLI CFW1 Filter wheel

Optec  Red  filter

11 exposures of 5 minutes  + 3 exposures of 10 minutes through Optec Red Filter (binned 2x2)

-Discovered a piece of flocking paper had fallen loose inside the main baffle tube from the night before and this was partially obstructing the light path. I am thinking this was the cause of the strange shaped stars in the collimation tests from the previous night

November 16, 2004 

Click on image to enlarge (2.3-2.7 arc-sec seeing, clear)


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