Query - Which cameras sell with a no dead pixel policy

[g__day]

I am more concerned with guide cameras here. I notice that my Meade DSI II Pro mono has about 6 bright pixels - which largely dissappear when I bin 2*2 and take a dark frame (using PHD) to guide my shots.

When I bought this from BinTel earlier this year I asked at the time was there a no dead / stuck / hot pixel warranty on the CCD - as I specifically want to dedicate this camera as a guide unit and I didn't want hot pixels confusing my guiding software. I was rather surprised when Don stated that no pixel policy had ever been articulated by Meade and BinTel simply didn't know what classed as a working versus defective unit when it came to hot pixels.

This got me wondering what other manufactures warranties are for typical guide cameras - be they seperate units QHY5 / 8 or in-built ones such as the two CCD S-Big cameras.

Does anyone know what the warranties are for specific cameras?

Alternatively anyone found good software or processing methods to alleviate the effects of hot pixels when guiding?

I have mostly got around the issue (unless clouds come out, dim the guide star too much and my one remaining hot pixel grabs my guide softwares attention and it then won't re-grab the star again once the clouds pass by).

[jase]

How much money you got to spend? You can always ask for a Class 0 chip, but it will cost you. Producing CCD chips isn't cheap, nor easy. The technical tolerances to producing a Class 0 chip are extremely high. Most research facilitates will settle for a Class 1 or 2. The higher the number the more defects. Most camera manufacturers will tell you their cameras are within specifications for defects, and to be technically accurate they are. I know of an Apogee U42 back illuminated camera with hot pixels and a slight hot spot which is within specifications....and this is a US$45k camera.

It is rare that guiding software will guide on a hot pixel given the initial sub exposure identifies star centroids. Hot pixels don't have a centroid, but I could understand the software making a mistake if sampling is less than ideal. As you've suggested 2x2 bin can greatly assist in both sensitivity and sampling. In addition, dark subtraction of the guiding exposure will significantly boost the S/N to identify the ideal guide star.

You're going to have a tough battle claiming defects as a warranty issue. Chip characteristics change with time. There is plenty of info online about chip classifications such as standard grade, research grade along with the various classes. Here's a start on SBIG ST series - http://www.sbig.com/FAQ/ST-7_8_9_10_2K_Family/What_class_of_CCD.htm

EDIT: Specifically to address your issue of losing a guide star, it doesn't hurt to script the reacquisition of a guide star between sub exposures or check out some of the MaximDL plug-ins. Multi-guide is pretty cool. Allows you to guide on more than one star simultaneously. At the end of the night however, clouds are clouds. Loss of a guide star is sometimes unavoidable.

[g__day]

Thanks Jase - Yes I don't understand why PHDs dark subtraction doesn't remove hot pixels with 100% accuracy? I'll have to go back and try MaximDL's multi star guide again.

End of the day for $580 I have quite a decent guide camera (might try removing the neutral filter and seeing if that helps). Really its only when seeing is very poor that guiding becomes problematic.