Astronomical Imaging Hardware
The latest technology often includes longer time exposures coupled with noise reduction and more sensitive sensors, making these digital cameras much more useful for astrophotography. Canon, Fuji, Pentax and Nikon seem to be most favoured by amateur astro-photographers.
Canon EOS digital SLR cameras and Canon L series telephoto lenses
I currently use an unmodified Canon 6D full frame and a Canon T2i APS-c modified to be more sensitive to infra-red wavelengths of light. Along with many other Canon dSLRs, the ones I use are all highly recommended by astro-photographers around the world. Canon appears to have developed the best low noise high sensitivity CMOS sensors currently available. The Canon T2i is modified by Hutech for astronomical use. There are several important features which make these cameras ideal for amateur astrophotography:
- lower noise at higher ISO
- higher ISO available (1600 for the T2i)
- more sensitive sensors
- modified for increased sensitivity to infrared (T2i)
- high resolution – 18Mpix for both the 7D and T2i
- 48 bit colour when raw format is used
- mirror lockup
- fast shutter and image processing times for general operations
- fast writing of images to memory storage or through USB2 to a notebook computer
- big LCD screens
- “Live view” feature
I use both dSLRs for prime focus photography on a Meade LX200R 14″ SCT telescope, and also use the T2i prime focus on my Borg 101 ED f/4 Astrograph apochromatic refractor mounted on a Skywatcher HEQ5 Pro mount. I also mount the cameras and telephoto lenses directly on an Astrotrac travel mount or directly on the HEQ5 mount. The Canon CMOS sensors produce superb, low noise images. I normally save images in Canon RAW format, giving 48 bit dynamic colour range instead of the 24 bits used by the standard jpg or tiff formats. The modified T2i is particularly effective when photographing emission nebula, however I also use it when photographing celestial objects that do not emit much infrared since I have it permanently setup for astronomical photography.
The Canon ES 400mm L series telephoto is a sweet lens for astrophotography, although I have since sold it in favour of the Canon ES 70-300mm L series zoom telephoto. Both lenses are like having a widefield refractor telescope, but in a smaller form factor. I first used the 400mm telephoto (with a Baader solar filter) for my shots of the 2006 Total Solar Eclipse in the Libyan Sahara Desert. I have subsequently used these telephotos for quite a few wide field Deep Space images, and find them to be perfect companions for travel. The Canon ES 70-300mm L series zoom telephoto is great for astrophotography when a wider field of view is needed.
The Canon TC-80N3 Timer Remote Controller is an important piece of gear for an astrophotographer such as myself. It replaces using a laptop computer to run automated sequences of shots. I have modified the TC-80N3 cable to enable control of either the 6D or T2i by cutting the cable and inserting a mini stereo jack and plug. I plug the two halves together to control the 6D shutter, or use the mini stereo plug to control the XTi shutter.
Astrophotography makes use of the fact that taking a series of images and “stacking” them will create a single resultant image with a superior signal-to-noise ratio. For example, a series of 20 images taken for 1 minute exposure time each will yield a noticeably better image (when stacked together) than a single 20 minute shot. The exposure timing and programming available with the TC-80N3 to control the Canon dSLRs saves me from doing an otherwise tedious manual timing and recording task during my astrophotography sessions in the field.