[rcheshire (Rowland)]

Picked up an old stock (Phenom II) Cooler Master for this project. The copper base is 39mm wide which is ideal for a 40x40 TEC. Light enough and small enough not to present a significant balance problem, given its displacement from the optical axis.

Heat sink calculation is probably the most complex part of cooling. Sourcing the right heatsink was a challenge. I think this will do it.

Thermal resistance is probably around 0.3 - 0.5C/Watt, which is OK, - a weight/cost trade-off. It will run about 10C warmer than the Alpha Novatech used on the 1000D cold finger mod.

10C is quoted by Tellurex as an ideal ambient air temperature / heat sink airflow differential. That's fine but needs a 0.16/Watt heatsink for this cooling application. I don't need to cool to that extent. 20C would be great for summer time. Winter requires as little as 6 - 8C differential, because the camera is already cold.

EDIT: While on the subject of heat sinks, it is apparent through testing that the 40mm copper strip is more of a heat repository than heat sink. If using a second external TEC there is more thermal mass to overcome before reducing the hot/cold side differential of the internal TEC, with greater power demands.

A better approach is to reduce the width of the copper conducting strip to that of the internal TEC. With the arrival of the more efficient Tellurex ZMax 25 x 12 TEC (regular post) I will replace the existing copper with a 25mm strip ending in a 40mm square to fit to the heat sink.