Intervalometer!

I have been looking into the CHDK lately and what it can do that our camera can't offer on it's own.

A while ago I realised that there was no option to plug in a remote trigger to the SX40. So this meant that to trigger the camera without touching it, I would need to set it to self timer. This doesn't really help when you want to take a continuous set of images to create a lime lapse effect where you can see something moving over a long period of time.

My main goal was to create star trails. At the moment, I have about 300 images sitting on my computer that I took last night. I haven't yet composed them into one image but I'm hoping they achieve the star trails I wish to capture.

Quite often people take long exposure images for hours at a time and they get the star trails that way. However I don't really like this idea for the SX40. I had a go with it. Now granted I didn't have my settings perfect and the image was pretty over exposed, but my main worry was how hot the camera got. It was just sitting there in the garden in the evening so it wasn't sitting in direct heat and when I got it back in afterwards it was pretty heated. On top of this, the image usually takes the same amount of time to process as it does to take, so a 1 hour shot takes about 1 hour to process which obviously takes a lot of waiting time for something which may not have worked out. (It is also very annoying when your battery cuts out during the picture processing).

So in general, long exposures over many hours seem to be something best kept on SLRs in my opinion - at least I hope it's not only my camera which overheated!

There is also the option of time lapse by leaving the camera filming and then speeding up the footage in  programs like Premiere Pro or Windows Movie Maker. Whilst this does work, the camera limits the films clips to around 4GB per clip which means that you then have to sit with the camera so that you can restart the filming when it cuts out so you don't miss anything. I tried this method at Frensham Ponds about a month ago and I really liked the results, but it just wasn't practical for a long time of say, 2 and a half hours.

In addition, filming takes up a lot of memory whereas taking multiple pictures means that you can fit around 2 hours of pictures on a 2GB card, rather than having to use a 16GB card for the 1 hour of constant video footage! (These are rough amounts from my experience)

I have gone on a tangent.

My point being, I looked into the Intervalometer because it does all the hard work for you! Once you have set it up, you can leave your camera star gazing in an evening and with a well charged battery you can get around 2.5 hours worth of stars passing by and capture their movement.

A normal intervalometer would be built into a good remote trigger which would just plug into the camera and tell it to take a picture every <enter number> seconds/minutes. But as we cannot plug in a remote, we need to use CHDK in order to achieve this.

One of the Facebook page followers cleverly suggested something as simple as tying an elastic band around the shutter button so that it would continuously take pictures as long as you have the camera set to multi shot. I haven't tried it but this seems to be a good idea if you wish to avoid CHDK.

Personally I am growing to really like CHDK so I decided to go for it.

So I set up the SX40 yesterday, set the focus to infinity so it didn't bur any of the images (Infinity focus is done through the hack kit), set the shutter speed to 15 seconds and did an override of the ISO using the hack kit (however the ISO wasn't quite high enough to capture the stars). I'm going to cover all of this in a video tutorial because I am doing the one thing I hate which is talking techno mumbo jumbo without actually explaining how to achieve it.

So the camera sat in the garden taking a new picture every 30 seconds and this was the result (Try watching it full screen as the detail is small and quite dark - my bad!):

Don't be put off by that awful thumbnail... I have no idea why it shows up like that.

As you can see, I obviously had my ISO too low in the end as the stars sort of disappear however I wanted to share it to show how it came out. So I will try again tonight with slightly different settings and will make a video to show how I did it.

For those who are wondering why I would use a higher ISO instead of using a longer shutter speed, it is essentially because, the picture takes 15 seconds to take, so it needs 15 seconds to process. If the picture takes 30 seconds in total to take and process I will only just get enough pictures without getting gaps in the movement of the stars. If I did a 30 second shutter speed, it would take 1 minute in total to make the picture if we include processing time.

1 minute per picture would leave quite a big gap between the stars movements. The very first test I did of the intervalometer took one picture every 2 minutes and looked like this:

So you can see the gaps in the stars/moons movements where there were no pictures being taken. Ideally these would look like streaks and would look quite surreal.

So I now have 300 images from last night which I need to compose together so make the star trails I have been aiming for! I will update to see if it worked and I will post a tutorial on the Intervalometer and time lapse photography in the next couple of days!

Ciao for now!