How to use an intervalometer
29 November 2019
The cheapest way of taking a photo through a telescope is using a mobile phone, normally stabilised using a phone adapter, such as the saxon ScopePix.
This is a good start, but the next step in astrophotography is to use a DSLR. These attach to the business end of your scope using an adapter called a t-ring (this is a photo of mine).
But then you've got a whole new set of problems. Every time you press the shutter button, you rock the scope slightly and it ruins the photo. And you want to take lots of photos so you can give them to your stacking software. And you don't want to be hovering over your rig all night, just pressing the button every minute or so. After all, we all need to sleep occasionally.
What you need is a way of pressing the button without your having to actually be there. If only there were some gadget that does that for you.
Of course there is, it's called an intervalometer, and it’s like an old cable release with a brain. Most DSLR astrophotographers use them all the time.
The intervalometer connects to your DSLR using a cable (some newer ones do it wirelessly). Put simply, it just presses and releases the shutter release on your DSLR, but it’s programmable. With it running on your camera in bulb mode, you can do a pile of things.
You can set the time between when it presses the button and when it releases it – giving the length of your exposures. You can set the time between when it presses the button and when it presses the button again. You can set the number times it repeats all this. You can set a delay so it doesn’t do anything for some time after you’ve started it running.
Last night I needed to take a time lapse of Orion rising. I’d set up my DSLR on a tracker, pointed it at where Orion was (behind a fence and some trees) and set the tracker in motion. I set the intervalometer to take a series of 75 exposures, each one being 30 seconds, and separated by two minutes. Then I set an alarm and went to bed.
One caveat though, try to remember to keep it out of the frost!