NGC7293, The Helix Nebula. On this particular evening I had bright moonlight, light pollution, cloudy weather and a 25-minute time slot to contend with as it drifted between the rooftops. I could only capture 60 second sub frames so I set the camera on X2 bin mode. The total exposure time was 8 minutes using a H Alpha filter, 6 minutes using O111 filter, 2 minutes using a S11 filter and 60 seconds using a blue filter. I captured 60 second sub frames with matching dark frames and combined them with flat field frames to reduce the effect of noise and vignetting in the final image. The telescope was a 4-inch f/6.3 refractor on a Vixen Atlux mount and an Atik 383L mono CCD camera.
The time-slot
The Helix nebula appearing over the rooftop
The Helix nebula
