[rally]

For many situations there is an advantage in having a smaller CCD with smaller photosite size (for the same number of mega pixels) as this will yield a more detailed resolution image of the same object - ie get in closer

This makes the Olympus 4/3rds sensor ideal for astro photography - but . . .
The caveat is that the Olympus CCDs are generally noisier than the Canon sensors for long or dark exposures, but with the release of the new models this year their noise and high ISO is now much better.

Olympus now has a number of live preview models
E330 (7.5mp), E410 (10mp), E510 (10mp) and the soon to be released E3
The E330 has and the E3 will have a tiltable CCD making manual focus with live preview with up to 10x magnification.
The E330 uses live MOS sensor (not CCD).

I have successfully used the E330 for moon shots during the eclipse with terrestrial lenses and the live preview with the ability to zoom up to 10x is not just a pleasure to use it is almost bordering on essential.

They can be controlled offline via a PC and the image is available on the PC screen.

I am waiting to receive one of the new breed of cameras and can report when I get a chance. They can also be successfully modded for IR photography. There is a Yahoo Olympus Astronomy group that may know more.


PS Forgot to mention - Dust is almost non existent on the Olympus DSLR sensors - they all have an ultrasonic sensor that vibrates the CCD and the dust falls off onto a sticky pad every time the camera is switched on or you tell it to do a cleaning cycle - I haven't had any dust on nearly 20,000 images this year.
And the Olympus Camera can accept almost every lens ever produced for any 35mm camera or DSLR (except most of the canon lenses) - so any old lenses you have or can get cheap on eBay will most likely be useable
Note all lenses will yield an effective focal length exactly twice their 35mm foacl length - so a 50mm lens will yield images that are equal to using a 100mm lens on a 35mm camera, your 150 will be 300mm and if you have an old mirror then your 500-600mm will be 1000-1200mm.