Basics of Astrophotography

Basics of Astrophotography

I have been photographing the night skies for many years, and is something I LOVE doing. My results are dependent on the camera, the lens and the darkness and quality of the night sky. If you have the right equipment, then it is a relatively easy process to get started, and start experimenting with the settings,

to improve the final outcome. I am certainly NOT an expert, and go only by my own experience, which perhaps not all may not agree with.

I will discuss the basics only, and if you want to take multiple images, and ‘stack’ them for a better result, then this is easily researched on the Internet.

My equipment - Canon 450D, tripod and cable release. Lenses include - Canon 50mm f 1.1, Sigma 17-70mm F2.8-4.5, Canon 75-300mm f 4-5.6, Canon 18-55mm, MC Zenitar fisheye lens.

Equipment Needed

  • A digital SLR (DSLR) camera (or a film SLR), though there are some compact digital cameras in which the shutter can stay open for up to 30 seconds. I have a nifty Panasonic Lumix which has settings for 15 sec, and 30 sec. and can take quite an OK photo.
  • Your desired lens for either wide angle, normal or telephoto (50mm focal length is a standard lens, though I like a WIDER angle like 28mm or 18mm).
  • A sturdy tripod.
  • A cable release is very handy, though I have taken some reasonable pictures with dodgy finger on the shutter button, though this is not advised. A cheap cable release is easily purchased off eBay.
  • You will also need to cover up to protect from the ever present mozzie, which can ruin the perfect photo as you swat at them, move and bump the tripod!! Have done this many times.

What to Photograph

This is purely a personal preference and may cover multiple targets.

Planets and the Moon are very popular targets, as is the International Space Station (ISS), and other satellites.

Meteors are very tricky, and based largely on luck and timing, than technique.

Do some research on the internet to see what is presently visible in the night sky i.e. visible planets, meteor showers, comets etc., and then you can start your plan.
The times of satellites, and iridium flares are listed on www.heavens-above.com and is a great resource.

A dark site is a bonus when doing astrophotography, so as not to be troubled by streetlights, cars, and neighbors suddenly popping the spotlights on ….. or just the strong glare from city lights in general.

Another favourite of mine to photograph is the Milky Way, and I have numerous pictures showing the beauty of the starfields and gas clouds. A dark site will enable fainter objects to be seen and imaged.

Technique

Bulb

The settings on your camera will need to be adjusted to allow the camera lens to stay open for amount of time you require. This is achieved by using the Bulb setting …you may need to play with the settings, or read your camera manual if having trouble finding it.

Exposure

After 20-30 seconds (depending what lens you have on) you will start to get star trails, so aim for about this time, or less. If you are lucky enough to have a telescope with a motor drive, you may be able to attach the camera to scope so as not to get star trails, and 'track' the stars. This will enable to lens to stay open for a longer period of time, and capture more objects for a beautiful photo.

Star trails can also make for an effective photo, and this maybe what you want, then the lens will need to be open for > 5 minutes depending on the desired outcome. Star trails around the polar areas can be stunning.

APERTURE

This will need to be adjusted, to allow as much light into the camera for the image to develop. In many cases, this needs to be open as wide as possible, and depends on the lens being used. Your camera lens may have numbers like f 3.5, and this 3.5 is the aperture. A FAST lens will have a bigger aperture (smaller number). I have a 50mm Canon lens at F 1.8, which takes a mighty fine picture, though I prefer a wider angle than 50mm. Wide angle lens may start at 17 or 18 mm, and this will give you a wider view of sky.

You may need to close the aperture a little if the sky is too light, after sunset etc …… e.g. if 3.5 is the lowest number on your lens (your widest aperture) then you may have to wind it up to 4 or 5.6, so to prevent your photos being washed out with too much light.

ISO/ASA

This setting also allows the camera to image at different settings to also allow for light. My Canon 450D highest ISO setting is 1600, which I like, though other cameras may be lucky to go up to 3200. This setting is also adjusted depending on the light in the sky.
Early in the evening you may need an ISO of 200, then gradually increase as sky darkens.

The beauty of DSLR is that you can check the picture after it is taken, and alter the settings to improve the photo. If the photo is too light, then turn the ISO down, and/or alter the aperture to decrease the light going in through the lens.

Ready, Set and Go

After working out what you want to photograph (e.g. constellation Scorpious), find a flat, dark position with a good view of sky and set up tripod and camera. It is often better to set on Bulb, set 'f' stop to the largest opening (smallest number f 3.5 etc), and attach cable release inside the house. It is also better to use a high quality format for the pic, and many astrophotographers use the RAW setting. Move the camera to frame the constellation (roughly), be sure all is in focus (manual setting to infinity), press cable release shutter button for about 20 seconds, and have a look at the result to check for positioning and focus. If OK, then try for longer shots. You may want to take some random photos, and face the camera in a few different directions to capture some other constellations. You may be lucky to image a meteor or satellite as well.

When you download your photo, you may need a star atlas to work out what you have taken, and some photo programs will allow you to label the constellations. This is also a great learning process, and helps to identify smaller constellations aside the larger ones. 

Not all will work, so don’t worry, just delete the blurry ones ... easy.

That's the beauty of digital cameras that you can take as many as you like, as long as your battery can keep up. I always have a spare battery with me.
When you take your photos, it can be a good idea to jot down the settings, so as to have a record of what was used for each photo. I always forget to do this, but some camera software on the computer will show you what settings and what lens was used.

These are some examples of settings

  • Venus and Jupiter at 7 pm, so sky still with some light- ISO 400, 20 sec, F 4.6.
  • ISS/Satellites – ISO 800, 35 seconds, F 4.6
  • Moon – ISO 100-200, aperture 4.6, 2-4 seconds only, as Moon is very bright, and overexposes   EASILY.
  • Meteors (later in night) and Milky Way – ISO 1600 (or more), 30 seconds or more, and aperture wide open.

As I said, these are only the ‘basics’, and as you take more photos, you will become more comfortable and confident to alter the parameters for a picture perfect astrophotograph.

It is a wonderful hobby, though can be expensive as you strive for a better picture, and keep searching for ‘good glass’ in terms of a great lens to pop onto the camera.

I seem to be accumulating an ever growing assortment of lenses to cover a variety of opportunities not to be missed. It can be as addictive as eyepieces for your scope.

If you have any further queries or comments, let me know. The main thing is to enjoy yourself, and if happy, then you can also post your pictures on the forum so we can all enjoy them.

Liz Gleeson