Wednesday, 5 February 2014

A survey of Galaxies

Galaxies can be very beautiful objects to image. They are all unique, can often have very intricate spirals, and don't take much work to get a good picture of. The tricky part is knowing which galaxies to take images of, as there certainly are a lot! Over the past 18 months I have been taking images of some promising galaxies and here I present the results of that endeavour.

There really are a lot of galaxies (most of them very very far away). Most of the fuzzy dots in the centre of this image are galaxies, not stars. This close up (external image) shows this more clearly.

Where to start?

I started my search in the NGC Catalogue. The Messier Catalogue contains many easy to observe galaxies, all in the Northern Hemisphere. But only containing 110 objects, and all being of a reasonable size in the sky, it is easy to skim down a list like this one and pick out some galaxies. The New General Catalogue contains 7,840 objects, a large proportion of which are galaxies. Lots of these galaxies are in the Southern Hemisphere and a majority are really too small to be worth imaging with the BRT (similar in size to the ones above).

I found a downloadable database of the NGC Catalogue, which contained information such as object type, size, brightness and location in the sky. I then filtered this list by location and size to give large and observable galaxies. I went through one by one, confirming they were observable and that they looked like good, photogenic galaxies. I mostly omitted elliptical galaxies in favour of spiral galaxies or irregular galaxies. I then ordered images of the most promising of what remained one by one.

Some of the galaxies weren't visible at the time I did this and so I had to wait the best part of a year for some of them to come back. Even then, some of them were ruined by problems such as sky glow or trailing (at the time when we were having problems with that) and needed to be ordered again. Even now, I am waiting for a few last galaxies to be re-imaged. Still, most of them returned, I have compiled a little gallery of all the images and I will add the last ones as they are taken.

All images are half-size (but all to scale of course). You can click on an image to view the original image as well as to see detailed visibility information and to submit your own request like mine.

All images were taken with a single 3-minute exposure, no filter, using Galaxy Cam and quickly processed using the flash fits viewer.

I now want to pick out a few of my favourites and spend some time putting together some nice composite images (which of course I will post on my blog as before).