NGC 7008 is a planetary nebula sometimes called the Fetus Nebula, which lies in the northern reaches of the constellation Cygnus.  Glowing at approximately 12th magnitude, NGC 7008 spans only about 1.4 arcminutes in size, making it a good target for longer focal length imaging systems under conditions of good seeing. 

This image was acquired with two telescopes to produce a final HOO composite with RGB star colors.  The narrowband exposures were captured with a C11 EdgeHD at f/7 and approximately 2000 mm focal length.  The narrowband filters were an Orion Extra Narrowband 7 nm H-alpha and a Chroma 3 nm OIII using a QSI 660ws CCD camera.  The star colors were obtained with a Sky-Watcher Esprit 100ED refractor and a QHY268M PH camera with Baader RGB filters.  RGB subs were captured in Mode 3, Gain 14, Offset 10, and exposures were 240 s each.

The choice to use two telescopes was simply based upon the QHY268M being attached to the refractor at the moment.  I am slowly progressing toward running both telescopes simultaneously on two mounts to speed up my image capture.  This image was a nice milestone toward that goal, but I used the Paramount MX with each telescope on different nights.  The question of the day is whether my old CGEM mount can handle the refractor well enough to capture RGB data while the C11 is busy riding on the Paramount MX.  I will find out soon, with clear skies and a full moon approaching.

The seeing was really quite good during the nights on which the data were captured, except for the night on which I shot the RGB subs.  It has been a long time since the seeing was good enough at my location to justify using the C11 EdgeHD over the refractor.  The final image was drizzled 2x to achieve a somewhat optimistic image scale of 0.23” per pixel, with the idea that sharpening and deconvolution algorithms can perform better on more highly sampled data, even if the seeing doesn’t quite support such high resolution.  The final version was cropped to frame this small planetary nebula well.

Processing was done with several programs, but one difference from my previous images was that calibration and stacking were carried out in Siril instead of Deep Sky Stacker.  I was pleasantly surprised by how well Siril performed with noise rejection, considering that 12-minute narrowband subs do suffer from significant thermal noise.  Details were enhanced using multiresolution sharpening in ImagesPlus, and some mild noise reduction was applied using Noiseware.