OK, so we’ve covered the basics, and we have talked about equipment. So now it is time to actually take your camera and your telescope and start taking some pictures. So how do you set these things up? Well, actually there are several ways. This graphic shows the main ones:
As you can see, there are several ways to couple your camera and your telescope. Let’s discuss them in order:
Prime Focus/Direct Projection The camera in this case is little more than a CCD & shutter system. The camera body is attached to the telescope (most telescopes made these days have threads on the eyepiece holder). This will entail something called a T-Ring adapter. T-Ring adapters are brand specific to the camera and sold by the larger camera supply companies.
In essence, the telescope is now the camera’s lens. Its one of the simplest setups but it has limits – the magnification is usually not very high, for example. This is usually OK on most objects as the digital camera’s resolution and some selective cropping in a photo editing program can give you the image you want. Most specialty telescope camera eyepieces work using this technique as they usually are just dropped into the eyepiece holder.
Afocal Photography: The idea here is a simple one: Whatever I can see through the eyepiece I should be able to photograph. This is pretty much true and one of the simpler setups if you accept certain limitations. Afocal photography has been around for a long time, but with digital cameras allowing for you to see the shot in real time (instead of waiting to get the film to developed) it has had a resurgence in popularity. Now of course a lot of the problem is that holding the camera up to the eyepiece does not really work well on its own – The view will be faint and the camera will need to take a long exposure shot. So holding it in your hand won’t work well unless you are a human statue. For those of us who are not there are devices that hold the camera in position to take the shot.
Even so, this technique does have limitations – there is often a lot of vignetting (where the view through the telescope does not fill the camera field of view, it doesn’t work so well for long exposure shots (the camera is held by clamping to the eyepiece and thus not incredibly stable), and it is surprisingly tricky for such a simple technique. On the other hand, the clamping devices do not cost very much, so assuming you already have a suitable camera and telescope (see part 2) you can do some astrophotography on the cheap since the only less expensive technique is piggybacking (see part 1). You can even use digital cameras that are not DSLRs!
Projection Photography: Here the camera is once again lensless, but the telescope keeps its eyepiece in place (unlike Prime Focus Photography). This method has some excellent advantages: it has adjustable magnification, for example. But it is perhaps the most persnickety to setup (although opinions will vary). This method usually involves the T-Ring adapters mentioned above as well as some other camera adapters. However just having the adapters does not set everything up automatically. There is a lot of adjustment that will be needed to make the image the correct size and magnification.
These are the main method of astrophotography – there are of course more methods that are less common but they are out of the scope of this article and of “Astronomy Hints”. Remember that while we have put out some stern comments about the effort required for astrophotography, we also want to point out that it can be lots of fun and very rewarding – just remember what you are getting into first!