The cloudy weather of the last few mights relented last night and I was able to try out my new 85mm lens for the first time. I'll admit straight away that there are a few technical issues with this image. The focus was very slightly off (I disabled the 40D's "LCD Auto Adjust" Live View setting which I think
caused the stellar images on my laptop's screen to appear fat making it difficult to see the point of sharpest focus) and, judging by the amount of background light in the RAW images, the exposures were a little longer than they should have been. That was an issue with my local street lighting
as the 120 second dark frames from the camera were totally black apart from a few stuck pixels.
Anyway, here is the result of stacking 7 images. Each exposure was 120 seconds at ISO 400 and f/1.2 with the camera mounted on top of my telescope to take advantage of the motor driven tracking. The resultant images were aligned, stacked and heavily
post-processed using IRIS
and a little cosmetic finishing was done using Photoshop. No airbrushing or the like was done - what you see is entirely derived from what came out of the camera. If you want to know where in the sky this object is then pop outside in the Northern Hemisphere around 11 o'clock tonight and look a little west of directly overhead (temperate latiitudes). Unfortunately the North American nebula (WiKi
), seen near the left edge of the image, is too faint to be normally seen with the naked eye.
The bright star with the blue halo is Deneb
and this is the 19th brightest star in the night sky. It is significantly hotter than the Sun, hence the blue colouration. Here is a map (courtesy of Wikipedia) which shows both Deneb and the North American nebula which has the designation NGC7000 and which is indicated by the larger circle. Up in my image would be roughly to the left in the map.
The combination of faster glass and stacking multiple images has certainly made a difference compared to my previous image posted earlier in this thread. I still hope to do better though. In particular, because I didn't use a "flat" frame during the image processing vignetting in the corners is far too pronounced.
EDIT: Added comment about vignetting in the last paragraph.