Thread: Canon 400D EOS
View Single Post
Old 30-11-2007, 10:27 AM
astroturf (Bryan)
Registered User

astroturf is offline
Join Date: Mar 2007
Location: Bardwell Park NSW
Posts: 245
Originally Posted by Dennis View Post
Hi Bryan

There are two main types of photos you can take with a DSLR and a telescope and both really require a polar aligned equatorial mount to allow long exposures to be taken:

1. Piggyback where you mount the DSLR + lens on the Ďscope/mount and use the tracking capability of the mount to take wide field exposures.

2. Prime focus where you remove the eyepiece and replace it with the DSLR, minus its lens, but fitted with a special adapter. Effectively, your telescope now is a super telephoto lens and the DSLR simply holds the CCD chip to record the image.

Both these techniques require your mount to be an equatorial mount and be to polar aligned, so you can take long exposure photos without having the stars trail.

The standard 400D has a built in filter that cuts off a lot of (useful) light at the red end of the spectrum, which is unfortunate as objects such as the Eta Carina nebula are rich in these wavelengths and the built in filter does a good job of cutting these out, so you only record a fraction of what is available.

Some people have their 400Dís modified (expensive) by having this filter removed, allowing the full spectrum to reach the CCD chip.

If you use the DSLR + lens AND the Stratus eyepiece, this is called ďafocalĒ photography and will usually give you highly magnified photos of the Moon, albeit with some vignetting. It can be difficult to hold the camera steady and get a nice focus with this technique, whilst avoiding any vibrations from the mirror slap as it flips up to expose the CCD.

Well, thatís a very brief sprint through some of the issues, I hope it proves helpful.


Thanks Dennis

You've certainly filled in most of the blanks(& possibly opened a can of worms!)

if you were to modify(remove) the 400d filter,would that then enhance the camera for normal use as well or make it less suitable?

the way I'm reading it ,the 400d has a maximum 30 sec shutter speed ,is this also udgradable?

I'm currently "experimenting" with a DSI, would the Canon offer a bigger FOV & could the 3.3 reducer I have ,be used to any advantage?

Reply With Quote