NGC 7635 & 7538– The Emission Nebula in Cassiopeia & Cepheus

NGC 7635 – The Bubble Nebula in Cassiopeia
NGC 7538 – Emission Nebula in Cepheus
Telescope: Meade SN8 at f/4, Orion Atlas EQ-G
Camera: ZWO ASI071MC, Highpoint Scientific UV/IR filter
Sensor Temperature: 0C, Gain: 200, Offset: 50
Guide scope: Williams Optics 50mm, Meade DSI Pro II, PHD
Exposure: 66x120sec saved as FITS
Darks: 32x120sec saved as FITS
Flats: 32x5sec, LED tracing tablet
Average Light Pollution: Red zone, good transparency
Lensed Sky Quality Meter: 18.9 mag/arc-sec^2
Stacking: Mean with a 2-sigma clip.
White Balance: Nebulosity Automatic
Software: Nebulosity, Deep Sky Stacker, Photoshop

While imaging NGC 7635 you often see the open cluster M52 to the northeast, but on one occasion I also noticed a beautiful red emission nebula off to the northwest; NGC 7538. I revisited this area to image both NGC 7635 (lower left) and 7538 (upper right) in the same field.

This is the last in a series of images that I took to explore the use of a simple UV/IR filter and adjusting the white balance as part of my processing in place of my usual Orion Imaging Skyglow filter. I have done this a couple of times in the past after an evening of taking photometric images since I can’t use my skyglow filter when taking these images. The results are encouraging, however, I seem to get better color and better contrast when using a good imaging skyglow filter, particularly with emission nebula and the H-alpha regions of galaxies. So, using a custom white balance alone can be effective while imaging under light polluted skies. However, at least for now, a good light pollution filter seems to give better results. That may change as LEDs replace the current vapor lamps for municipal illumination.

-John

NGC 7635 & 7538 (7-25-2017)-2j.jpg