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There are 3 distinct ways of attaching a camera to look through an astronomical telescope:
A misconception about astronomical telescopes is that their main purpose is to provide a high degree of magnification, as a super-telephoto lens in photographic terms. While that is useful for studying the moon and planets and perhaps the sun, for other subjects it is more important to collect as much light as possible. So aperture is significant. My Meade telescope, shown above, has excellent optics for lunar and planetary photography but, in common with all catadioptric telescopes, its photographic aperture ratio is poor: f/15. So I can photograph the moon and planets through it but it is not so good for stars and nebulas. Many years ago I had a Newtonian telescope. It had an aperture diameter of 150mm, similar to the Meade, but it was f/8, which is typical for the simpler Newtonian design. So these days I do star photography in the piggy-back mode described previously and I mainly photograph through the telescope for the moon, planets and sun (warning: the sun requires a special filter, to be described later).
Here is my camera mounted at the prime focus of my Meade telescope through a port on the back of the scope:
That uses a T-mount adaptor, having a Canon fitting at one end to fix to the camera body and a T-mount screw thread for attaching to the telescope. Telescopes and microscopes commonly use the T-mount standard for fitting accessories. The little white spot at the back of the telescope is a lever which flips a 45-degree mirror out of the way to give a clear path to the camera instead of reflecting up to the eyepiece on the top of the instrument.
In December 07 I bought an HEQ5 equatorial mount to overcome the power limitations of the Meade mount when loaded with a camera as well as the telescope. I removed the Meade ETX from its own fork mount. That was much easier than I expected. There are just two screws either side which need to be removed and the operation is reversible if necessary. The only difficulty I had was that an imperial Allen key was needed rather than a metric one, but I was able to improvise. The following two photos show where the screws are on the telescope and on the mount. I have replaced the screws on the telescope, simply to avoid losing them.
Here are some photos showing my Meade telescope and Canon camera on the HEQ5 mount:
This is how I intended mostly to use the new mount. One of my first results is here. However, the prime focus method looks even more promising - see below.
The only advantage of this over mounting the camera without the telescope would be if I wanted to use the telescope for guiding. But the drive of the HEQ5 is so steady that I think that will never be necessary, especially with my technique of combining many short exposures through GRIP.
This was never possible with the ETX drive because it was not steady enough when overloaded. First results with the HEQ5 are far better than I dared hope. See my very first result in this configuration, here. My new possibility of prime focus like this has made me realise that my "astro-process" in GRIP is not ideally suited to telescopic photography, because of the way it does background correction. Therefore I am releasing a new version (8.1.20) of GRIP that significantly improves matters.
There would typically be a telescope eyepiece inside the adapter, projecting onto the camera detector.
