Sadr & IC1318 Molecular Cloud - Triband (Cygnus), May 2023
FIRST LIGHT: Askar 500FRA telecope w reducer; IOptron HEM27 mount
ASI2600MC, FIRST LIGHT - Antlia Triband Filter
(66 x 300s exposures, Bin 1x1, Gain 100)
Total Integration Time = 5.5 hours
Sadr or Gamma Cygni is the star right at the centre of Cygnus, where the wings meet the chest. It is the second brightest star in Cygnus (Gamma?) and is a super giant (12+ x Solar Mass) that has already left the main sequence star path and is destined to become a super-nova. As with such large stars, it is burning though its fuel relatively quickly. Although it is 12+ times more massive than the sun, it is 33,000 times more luminous. It is currently 12 million years old, compared to the suns 5 billion year age. It lies 1800 ly away from us, and although it appears to light up the molecular cloud behind it, it does not: the molecular cloud is a much more distant 4,900 ly.
IC1318 is actually lit up by a hot blue star that is behind a dark patch of the dusty cloud itself, as a testament to how opaque these clouds can become. You can tell areas of the cloud that are behind and lit up by this star as it appears mainly H2 red. Where we are viewing the back side of the cloud (this side of the star, it is very dark / opaque. This can be differentiated from just absent or thin by the number of stars that shine through it.
IC1318 lies right in the Milky Way, and it is dust like this than obscures the centre of the galaxy from our direct visual view. Where the cloud emits light appears red to us, as in this image and blue where it simply reflects starlight.
Stars are undoubted being created within IC1318 aka the Butterfly Nebula, and is likely responsible for the nice star cluster directly above Sadr in this image (NGC 6910).
Overall I do like the job that the Antlia filter did. Ha/NII clearly dominates the nebulosity and I would like to have seen more contribution from OIII in the nebulosity. SCC calibrated the dimmer stars nicely, but the linear portion did not fit Sadr very well, and it ended up more teal than its true yellow colour. Star halos were definitely larger in OII than red, but nothing too bad. I really like the addition of the blue band to this filter, something I had thought of adding to a dual band filter after the fact before I got this one. In this image, I decided to leave it naturally red, rather than manipulate to generate a more colourful result.
The reducer did a pretty good job, too. There is a slight misalignment of colours in the corners (they were registered agains one another) due to relative distortion. I don't know if this is the filter, the reducer, or something else. Even this isn't bad though.