Andrew’s Astronomy Blog

C2009/P1 made it’s closest approach to M71, a globular cluster in Sagitta on Friday night. While the weather people were predicting a gap in the cloud for mid evening, the gap turned out to be only 5 minutes in length!

Checking the star charts for the following evening showed the comet still fairly close and within the frame for the 70mm ZenithStar and Canon combination. The weather didn’t start too promising but cleared late evening for long enough to get a five pictures before it clouded over again.

The comet core has trailed in this stack as I didn’t have enough images to process the comet and background stars separately and then recombine them. The two bright orange stars in the frame corners are Gamma and Delta Sagittae which make it really easy to find the cluster.

Image comprised of 5 90 second exposures at ISO 800

ZenithStar 70 with WO Field flattener III

Saturday was clear and the forecast for the evening was good so I started looking at Cartes Du Ciel for possible targets for the 20″. Low in the East is generally best for this system and fitting the bill perfectly was a comet, C2009/P1 (Garradd). Brightness was shown as M8.8 which is fairly bright as well.

The plan was to take multiple LRGB sequences with the Atik 383, each exposure being 60 seconds.  Then stack on the comet and remove the stars from the image, stack on the stars and remove the comet and finally combine the images. Due to the comet’s motion across the sky, this complex procedure is required to avoid trailing of either the comet or stars.

There were some problems with the altitude drive which resulted in a fair few frames being rejected but, after a couple of runs through Photoshop trying different techniques, here is the result.

Comet C/2009 R1 (McNaught) is currently travelling through Perseus, low down in the pre-dawn sky. I managed to get a single 60 second exposure from New Mexico on GRAS-14, a Takashashi FSQ 106ED with an SBIG STL-11000M-ABG camera. The comet is currently 177 million kilometres from Earth and makes it’s closest approach on 15th June at 170 million kilometres.

I’ve had to remove a substantial background gradient on this image as this was just before dawn and it’s binned 3×3 to reduce the image size.