The Double Cluster and NGC 772

Every half-way decent night in December for imaging is a gift. Last night, despite poor transparency and a quarter moon, I thought I'd give two objects I had never imaged before a try. The Double Cluster in the constellation Perseus was the first target. The Greek astronomer, Hipparchus, noted it as early as 130 B.C. What he saw was a patch of light. However, the true nature of the Double Cluster wasn’t discovered until the invention of the telescope many centuries later. The two clusters, NGC 884 and NGC 869, are normally not able to be captured in a single FOV; however, my camera has that capability.

NGC 884 and NGC 869 are at distances of 7600 and 6800 light-years away, respectively, so they are also close to one another in space. The clusters' ages, based on their individual stars, are relatively young. NGC 869 is 5.6 million years old and NGC 884 is 3.2 million years old, according to the 2000 Sky Catalog.

Below is my 10 minute image of the Double Cluster, with NGC 869 at the top and NGC 884 at the bottom. Click on for a screen-filling view.

 
The next target was NGC 772. Located in the constellation Aries, this galaxy rivals the size of our own Milky Way. It is notable for possessing a single elongated outer spiral arm, which has likely arisen due to tidal interactions with nearby galaxies. At around 100,000 light years in diameter, NGC 772 is surrounded by several satellite galaxies. It is 130 million light years away. 

In trying to image MGC 772, I found that my camera, with its large FOV, was not the best instrument for the task. It appeared rather small, but with some cropping, it is visible. I did a 20 minute exposure, but there is a lot of noise in it. You can, however, see the outer spiral arm which distinguishes it.

You may be wondering how I select targets for imaging. I have a collection of books which give suggestions for different times of the year. Magazines like Astronomy and Sky and Telescope give monthly ideas as well.