Imaging techniques a starters guide
I have seen it so many times people come to a star party of an observing session and there is somebody there imaging and the see the images and look in awe. The next comment from them is
“how do i do that”
This is one thing that strikes fear into me every time that i hear it…. the skills which i have developed for imaging have been gained over the last 10 years and they have been gained through a lot of tears and frustration. The biggest challenge then is to slow people down and make them relise that imaging can be done of many different levels and that the option of prime focus imaging with a DSLR may not be the best thing to start with.
There are a number of different ways by which an image of the night sky can be snapped:
- Whole sky imaging with a digital camera and a tripod
- Eyepiece projection with a digital camera and a telescope
- Prime focus photography with a DSLR and a telescope
- Astronomical CCD camera and prime focus photography
it may sound simple that there are only 4 ways to really gain images of the night sky …… the table below outlines the different methods
|Imaging Type||Camera details||Camera Mount||Telescope details||Telescope Mount||Comments|
|Whole Sky||DSLR or any digital camera||Sturdy tripod||Not needed||Not needed||Simplest form of imaging|
|EyePiece Projection||DSLR or any digital camera||None||Any telescope||Any, does not have to be driven||This can be used to get short exposures of say the moon|
|Prime focus||DSLR / cooled CCD||None||Any telescope||Driven Mount with polar alignment||This is now starting to get more difficult with driven mounts|
|Long exposure CCD images||Cooled CCD camera||none||Good quality refractor or Schmit||Good quality driven mount with correct alignment||This is the end point with this sort of setup it is possible to produce stunning vistas|
Basic equipment needed.
The most basic equipment is a digital camera, or a 35mm SLR camera. the camera must be capable of long exposures. In most cases modern digital cameras off a full manual mode which is needed to set the exposure length to at least 30 seconds. In the case of a digital SLR then a cable release will also be needed. Another important factor for modern digital cameras is the ability to manually focus the camera. this is really important as there is not many things to focus on in a dark sky. The next object is a sturdy camera tripod – it is possible to just position on a car roof; i have done this — but the real need to be able to mount at a comfortable level and allow the user to look through the view finder and also protect from vibrations.
As your skill develops then the your imaging techniques will also develop but starting simple keeps it enjoyable without a very steep learning curve
So how do you do that ?
The simplest form of imaging just has the camera on a tripod and open the shutter, if you do not have a cable release then open the shutter with the lens covered with a piece of card and remove after about 2 seconds — once completed enjoy a great shot of the night sky.