Hi all. I just wanted to chime in a little from a different perspective. I just bought a Q453-HR which is a US modified version of the QHY8. I too was a looking to step up my astro imaging and started looking for a new camera. I came across the QHY8 which led me to CCD-Labs (the US distributor/modifier)(
www.CCD-Labs.com). At first I looked at the chip size and the price and thought this was one of the "too good to be true" cases. Most of the camera's I looked at were at least 3x more expensive. Even a camera that uses the exact same ccd chip. In my opinion the astrocamera market is over priced and the gravy train will be ending soon. The prices of the ccd/cmos chips keep fall and it is a matter of time before someone puts together a camera that is much cheaper than the competition. I think we are seeing the first of such offerings.
I contacted about 15 people that used the camera around the world and asked them about performance and the darks thing. Some of these people produce absolutely incredible images. All of them LOVED the camera. Most (if not all) had stopped taking darks or went the master dark and defect map route. My personal opinion is that the dark thing is a big deal considering that you should take at least five dark frames at each exposure length the get a good average noise. If you take a five minute exposure thats 25 minutes on darks alone. For those of us with limited time that is a big amount of time. Heaven forbid you take a 20 minute shot!
The Q453-HR version is modified slightly from the original. They seal the CCD in an argon purged cell to keep moisture out. They also sell the camera with the upgraded cooling power supply that lets you control the current to the camera. They do this not because of cooling control (it is not close loop controlled) but to be able to step back on the power consumption. They also include Nebulosity in the deal. The down side is delivery time is 3 to 4 weeks.
I started a Yahoo group
http://tech.groups.yahoo.com/group/QHYCCD/join Feel free to join the group and share. We are small right now but we will get bigger!
Ed