M13 Cluster in Hercules

M13 is a globular cluster within the Hercules constellation, formed of about 300,000 stars. This was one of my first target with my new tracking mount, as it's a little fainter than other targets but still visible with a pair of binoculars.

Having set the mount to find the cluster, I took a few shots and was a little confused - I couldn't see anything resembling a cluster and as it was one of the first uses of my new mount - being a total novice I was sure something wasn't right. So I popped indoors to check on Stellarium where the cluster sits within the Hercules constellation - a quick diagram drawn on a post-it note helped me pin point it. It turns out I had captured it, but it was a lot smaller and fainter than I initially thought. The first shot below shows the image I initially captured, if you click on the image you will see where on the image the cluster is.

The constellation of Hercules, with M13 visible left of centre at the top

This weekend just gone, I stayed at my parents who live on the coast and have much darker skies. I stayed out for a few hours before tiredness got the better of me. I had three targets in mind, one of them being M13 again. 

This time I took 16 minutes worth of exposures, with 8 minutes of 'dark frames' which are used to subtract any noise on the sensor itself. I was pleasantly surprised with the outcome, after a few hours trying to get a decent results from the shots I took - the clear build up of stars as it gets toward the centre is pretty fascinating. 

16 minutes of exposure on M13 - Hercules globular cluster

How to: Capture Star Trails

Meteor on the right

Star trails have been something I've wanted to photograph since I first became aware of them around a year ago. The patience of spending all night in the garden with your camera in the freezing cold put me off slightly, but lately due to a clear window and some clear skies, I've managed to get the same results indoors.

This guide will briefly (and as simply as I can) explain the process I took to get these results by stacking multiple images together to create one final long-exposure image.

The first step is to set the camera up. For these images I use continuous shoot mode, with 30 second exposure and a low ISO (around 400) to keep the grain down. I'll set the aperture once the camera is pointing at the sky as it depends on how dark/light the sky is.

I've been taking my latest star trail shots through a back window in a spare room. By positioning the tripod against the wall, I can get the camera as close to the window as possible (try make sure the window is clean too!). Adding a bit of support to the tripod legs to stop any movement or slippage during the night. 

Once my shutter speed, shooting mode ISO are set, and I'm happy with the aperture, I use a wired external remote with locking switch to begin shooting. Continuous shoot mode will continually take shots while the remote button is pressed.

I'll then, usually, go to bed. You will usually find the camera silent in the morning, having drained all battery life. I've been told that when the sensor is activated is when the camera uses the most power, so continuous shots drain it pretty quick - however you should still get 5 - 7 hours of shooting out of a full charge (on my Canon 1000D anyway).

I'll then review the photos on screen, checking every 15 - 30 shots for clouds. Some trails I have had to cut short as clouds tend to come along after a few hours, in this case, I'll discard these from the final edit.

To stack the good images I use a program on the Macbook called Starstax (will add a link). This program, simply put, takes all the photos you select and stacks them together. Very simple to use indeed so no real need to explain further in this.

The stacking will show you each image as it stacks it, 2 or 3 per second, which is interesting to watch as you can see your photo gradually building up - star trails gradually getting longer. Occasionally you may see a plane fly past, or if you're lucky a meteor suddenly appear. By watching the stacking process you can also identify any shots that need touching up, for example last night I had to edit 4 or 5 photos after noticing a neighbour used a spotlight, thus filling the shot with an over-exposed foreground and bit of lens flare. A quick touch up in Photoshop on these images quickly solves this. If you chose not to touch these up, and simply delete these images, you will have gaps in your trails.

Once the stacking is complete, you can save the final image onto your computer.

2 hours 38 minutes

I tend to open the final image in Photoshop to see if it needs any touching up or colours fixed. I generally make the sky a little darker black/blue as so much exposure can make it pretty light/purple. I may also touch up the light pollution at the bottom of the shot.

I'm now pretty confident with this process, but am continuing to play around with different angles and parts of the sky. I'm also trying to hunt down some meteors of course ;-)