This is my first post in the "How I Took It" forum so I hope I get it right. I posted this image of the Milky Way galaxy in the "Share Your Shots" forum and also on an Astronomy forum website that I visit every now and then, and the shot seemed to get a nice response there, so I thought I'd share the process I went through to get it and the things I have learnt while taking it.
Firstly, here is the shot:
Milky Way Galaxy by WebberJason, on Flickr
Secondly, here is the equipment that I used:
Nikon 18-55mm f/3.5-5.6G AF-S DX (the kit lens for my camera)
A normal tripod
(and a blanket)
Ok, so here's the process I followed:
This kind of shot preferably needs to be taken in a rural area, where the skies are dark and clear. I also read that this time of the year (around June/July) is the best time to photograph the Milky Way (globally) as it is brighter now than during the rest of the year. The Milky Way is also known to be brighter near the constellation of Scorpio, and should be photographed when it is high in the sky, preferably overhead. If you do not know where Scorpio is, you can use a free program on your computer called Stellarium, or mobile phone applications such as Google Sky or SkEye, but once you know what it looks like it is quite easy to locate (it looks like a big, upside-down question mark to me). Wait until Scorpio is overhead (for me it was around 22:30 to 23:00, in the Southern Hemisphere), and then get shooting. With dark skies you will easily see the bright band across the sky that is the Milky Way.
Put the camera on the tripod and aim straight up.
It usually helps to keep the tripod as small (legs not extended) as possible, as this helps to reduce the effect of wind etc. on the tripod.
Focus manually if you can.
I have tried focussing manually through the viewfinder and this works if you can see very well, but the way I focus now, which I find a lot easier and more accurate, is to use my camera's Live View, pointed at a star and then zoomed in. On my camera you can digitally zoom in on your subject in Live View before you take the shot. For astrophotography, this function is perfect, zoom in as much as possible (the star should hopefully almost fill the screen now), and then manually make minor adjustments to the focus until the star is as small and as round as possible. Then lock the focus and you're set.
To sort out your composition and to make sure you're pointed at the Milky Way, take a few test shots using the highest ISO that your camera has, with exposures of about 3 seconds. These shots will be incredibly noisy and unusable but they will give you a perfect idea of where your camera is pointing and what your final image will look like. This also helps if you want to have some other subject in the foreground, like a landscape or a tractor or something (shots with a foreground subject give an added focal point and really lift the image in my opinion. There are tons of examples all over the web!). Once you're happy with the composition, set the ISO back to about 1600 (that's what I used for my shot but other ISOs in that region might work better for other cameras).
SHOOT IN RAW!!!
This will give you so much more to work with processing wise, and astrophotography requires quite a bit of post-processing.
Set your exposure time to between 20 and 30 seconds.
There seems to be a rule of thumb in the astrophotography world that says your maximum exposure time before you will get noticeable star trails is 600/focal length. In my case, I was shooting at 20mm so I could theoretically use a 30 second exposure, which I did. If you look closely at an enlarged version of my photo though, you will notice that even then my stars have started to trail. There is a fine line that you need to find between minimising trailing while still maximising exposure time, because the longer the shots are exposed for, the better the colours will be.
(Corrected later: NativeTxn pointed out that when shooting on a DX format camera, the rule changes to 400/focal length, rather than 600/focal length, to account for the cropped sensor. This explains why my shots had slight trailing. Thanks for that tip NativeTxn!)
Don't use the widest aperture that you have.
For some reason, using the widest aperture can cause some slight defects, especially near the edges of your shots, so try to refrain from using your widest available aperture. Different cameras will have different ideal apertures, but if you just go up a few stops you should be fine.
Shoot at a wide angle.
The Milky Way takes up a huge area in the sky so wide angle shots work great! This way you will also be able to keep your aperture wider, which helps to bring in more light to work with.
Take lots of shots.
I used my camera's interval timer function to automatically take 100 shots, one directly after the other. The more shots you take the better, because some will inevitably be ruined by a stray light, a cloud or some smoke from the fire (if you're lucky enough to have one nearby and the wind is blowing the smoke away from you). I found that after 100 shots though, my Milky Way was pretty much moving out of the frame.
DON'T BE DISAPPOINTED WITH THE IN-CAMERA RESULTS!!!
As I mentioned earlier, astrophotography takes a lot of processing, so your shots straight out of the camera are not going to be as amazing as you would like the final image to be, but the information and the potential is there!
I use a free stacking program called DeepSkyStacker. There are other programs out there that will do the same thing, but this is the one I use. It's free and fairly straightforward to use so I like it. You can read up about how it works on the website if you'd like, and there are ways to improve your images as well, but I think it can get quite complicated so I haven't tried that yet. The reason for stacking images is to help to reduce the noise levels (shooting at fairly high ISOs), and to give effectively longer exposure times, but without the risk of star trailing. For example, I stacked 10 30-second exposures to give me an effective exposure time of about 5 minutes.
I pretty much use the default settings, but I found this article very helpful as a guide. It also mentions some of the points I have mentioned here (I actually learnt a lot from it). One thing I might add though is that in about the fifth picture, the author selects "enable 2x drizzle", but this seems to use far too much memory for my computer so if you get an error message saying "Out of memory", try disabling that first and trying again. I only ended up using the 10 best pictures that I had (selected purely visually by me), and it seemed to work out fine, but the more images you use, the "cleaner" your final output is supposed to be (to a point).
DeepSkyStacker (DSS) recommends using other frames called darks, flats and biases, but I haven't had much luck using them yet.
The tutorial above also explains very nicely how to go about editing the output directly in DSS, which I found to be a good way to do it, but I had to play around with the settings a little more to get my picture to work. I guess each picture is different so you might need to play around a little.
Lastly I imported the 16-bit .TIF file (GIMP can not process 32-bit TIF files) into GIMP and made some final adjustments to the saturation and colour balance etc., and that was it!
I hope this was useful for anyone else who is looking to do some photography of this kind! Please post any photos that you do take so that we can all see, and feel free to share any additional tips that you might have picked up along the way!
Happy shooting and clear skies! (and don't forget a blanket!)
EXIF Data for my individual shots:
Image Quality: Compressed RAW (14-bit)
Device: Nikon D5100
Lens: VR 18-55mm F/3.5-5.6G
Focal Length: 20mm
Focus Mode: Manual
AF-Area Mode: Single
Shutter Speed: 30s
Exposure Mode: Manual
Exposure Comp.: 0EV
ISO Sensitivity: ISO 1600
White Balance: Direct sunlight, 0, 0
Color Space: sRGB
High ISO NR: ON (Normal)
Long Exposure NR: OFF
Active D-Lighting: Normal
Auto Distortion Control: OFF
Picture Control: [NL] NEUTRAL