My idea for this post is to illustrate that it is very possible to image interesting objects in the night sky, without the use of a telescope or an especially long focal length lens.
Our large neighboring galaxy M31 Andromeda is a good example, this galaxy can be made out with the naked eye, though you won’t be seeing many details that way! I’m going to use my Canon 20D here and yes I could use a big 400mm lens but that would rather defeat the object so here’s the list of kit used:
- Canon 20D
- Canon 24 – 105 L f4 IS
- Canon programmable remote timer trigger TC-80N3
- Celestron CG5 equatorial mount
So yes I have used one specialist piece of kit, the mount, but that really is necessary to track the sky due to earth’s rotation during the exposure time; no guiding system has been used though. The lens will be set at 105mm & wide open at f4; manual focus set and IS turned off. The camera was pre focused visually on a bright star and then the mount slewed to point at Andromeda. Whilst I used mains power for the 20D & recorded images straight to PC, this would still have been possible with a freshly charged battery & a decent compact flash card. The image below is the full frame output after processing (reduced in size of course) :
A total exposure time of 1hr 15mins was achieved by taking 37 separate frames, ISO was set to 1600. As well as these light frames, multiple dark & flat frames were taken. Darks are taken at the same settings & temperature as the lights but with the lens cap on, they are used to correct for hot pixels & noise. Flats are taken with the same zoom & focus as the lights but are at low ISO and are of an evenly lit object e.g. a whiteboard; they are used to correct for dust bunnies & vignetting. All of these images are put together in an excellent piece of freeware called Iris.
The output is then adjusted for contrast & levels in Adobe Photoshop before final output. Below is a crop into Andromeda herself.
As you can see, some of the dust lanes within Andromeda are very clear, the oval & circular bright patches above & below Andromeda are companion galaxies M32 & M110. So there we have it 3 galaxies, 1 picture and a focal length of only 105mm. “Size matters” or so they say but I’m not too sure 🙂
Why not have a go at a few photos yourself, it’s great fun.