Becoming a Narrowbandido

I have been impressed by widefield images of gas and nebulosity which were created with narrowband filters. I wanted to join this posse of Narrowbandidos and try some of these spectacular summer targets. Having seen Astrobackyard’s review, I opted for an STC dual narrowband filter comprising Ha and OIII. 

My first test would be with wide views and I installed the 2” filter into a 51mm Apo. On this particular scope, the filter thread sits ahead of any attachments in the imaging train. I foolishly tried to run an OAG for guiding before realising the guide camera’s view is subject to the filter and therefore not suited to short guiding exposures. I reverted to a small, separate guidescope.

I read that I’d need to run longer subs than I usually do to give the narrowband exposures a chance. I tend to do only 2min subs or so, reducing the risk of longer subs getting ruined by poor tracking or planes/satellites. On these first tests I pushed my guiding to 4mins. Given for many years I struggled to get 1min guided subs from my iEQ30 (solely my ineptitude) this was a serious leap forward which I attribute to the simplicity and excellence of the ASIAIR, ASI120mini and ZWO 30mm F4 guidescope all working in harmony. 

I started imaging around 9.30pm, in truth a little early as the subs were far better by 10pm showing far greater contrast. I had used SkySafari to plan the framing and also to sync the mount after platesolving. The image actually fitted better than the preview suggested which gave me a little room for cropping the edges of the final image.

This is my first narrowband image of the full Cygnus Loop comprising the Western Veil, Pickering’s Triangle and the Witch’s Broom Nebula. The image is 20x 4min subs using a CMOS single shot colour camera. The red colour is the Ha and the cyan colour is the OIII. I was pretty delighted how it turned out. This was also taken as a full moon was rising in the east proving that the narrowband wasn’t concerned with any effect of moonlight.

Next steps…

I also want to try narrowing imaging with my longest focal length. As most thing get trickier with more focal length, I’ll leave this alone until I’m confident with the exposures and use of the filters. 

Comparison: NGC7000 North America Nebula