M13 & M56

M13 is known as "The Great Globular Cluster M13" for a reason. These two images were taken with the same equipment on the same night. M13 is just a bit closer to us than M56---25,000 light years for M13 as opposed to 32,900 light years for M56, but notice how large M13 is. It is quite a showpiece in any telescope. It helps that M13 is in a part of the sky without a lot else to look at, whereas M56 is in Lyra, in the plane of the Milky Way, in an area chock full of stars. Anyway, I've wanted a decent image of M13. It's a popular target. North is up in the image of M56, and to the right in the M13 image.

One thing to notice about the M13 image is that two galaxies also make an appearance. The brighter one in the upper right is NGC 6207. It is perhaps 60 million light years away (one recent study puts the distance at 66.5 million light years, another at 60 million). The dimmer spiral galaxy between NGC 6207 and M13 is IC 4617 or PGC 2085077. IC 4617 is magnitude 15 or 16 and probably further away still.

These are last night's images. I actually imaged these targets twice this week, but the first time my guiding was not good enough to post. Even on this version of M13 it was not quite where it needs to be: notice that many stars are elongated slightly from north to south (it's human error, I assure you, and not the equipment). After I finished the M13 exposures, though, I fiddled around with PHD, the autoguiding program, and figured out what the problem was. With that problem worked around (not quite solved yet), I put M56 in the crosshairs and started the second set of exposures. This was all around 3:00 in the morning. I post them both together to show progress on the guiding front, about which I am quite happy. The guiding on M56 was not perfect, but I kept an hour's worth of frames in which the stars are actually round. For M13 I had few frames that showed truly round stars, so I kept enough of the best ones to make the image bright. Both are somewhere around an hour's worth of two minute exposures. I slept while the camera took the subframes.

By the time I imaged M56, it had been six hours since polar alignment: a quarter of a sidereal day had passed. Any error in polar alignment would have been at its maximum, and that probably accounts for my losing so many of those frames at a time when the guiding setup was actually working much better.

Images were taken with the Atik 16 through the AT66ED at f/6 (400mm), autoguided by a DSI Pro controlled by PHD through the Orion 100mm f/6. The mount is a Tak EM-10. Processing was done in Nebulosity and PSE7.