[Paul Haese]

Three years ago I bought an SBIG STXL 11002 camera. I have owned two QSI cameras for the last 6 years and both performed very well at my observatory site and the one I still own continues to perform flawlessly. During the period I have owned the STXL, the camera has been sited 6km from the ocean at Clayton in South Australia. Prevailing winds during the day typically come from the south or south west. There is never any wind at night except when we get northerlies, so the air mass during that time is dry and rare. In the norm the air is probably highlyladen with moisture and with some salt. I have often witnessed heavy dewing on site to the point water is dripping off everything in the mornings.

About a year after I first bought the STXL, the camera had its first failure. It has been back to the US for repair 7 times. The first failure was to do with the sensor. Several trips back to the States were required to find the problem and eventually the camera was replaced. The last few trips back to the states started identifying another issue of corrosion of the PCBs in the heat sink bay. The first image shows the bay of the camera that contains the communications and power boards. The communications board is on the bottom and the power board on top. They are connected together with exposed pin connectors which have air passing through them. The heat sink is seen located in the same area as the boards. Air is drawn in over the heat sink and then pushed out via the vents on the side which can be seen in the first image. In short the moisture laden air is passing over the boards. Images taken over the last couple of trips have shown corrosion on the boards and pin connectors. Salt was even seen on the most recent images of the boards. This sort of damage is not covered by SBIG warrantee. Though I have to point out that SBIG has been very good with warrantee claims in the past 6 trips. They expedited the claims quickly and kept me up to date regularly. In short they have been very good on the whole.

On the last trip back to the states I was forced to buy and replace the two boards that are located in this bay. The cost was $2300 AUD which included labour and insurance. I was initially going to try to sell the camera and off load the problem. This design does not seem to work well in my location. I note that my onsite computers are desktops and exposed to the same conditions and drawing the same air into the boxes and never failed in 6 years for one computer and 3 years for the one with the STXL.

However, after some consideration and consultation with a few people including SBIG I considered doing what is called conformal coating to the PCBs. The PCB's are coated in a hard silicone seal that prevents corrosion to the boards and components. It is commonly used in environments with high moisture, chemical concentrations and salt levels. The connectors also need to be coated in silicone but not entirely. The pins need to have correct contact unhindered by silicone. I got some excellent advice from someone in our astronomical society who works with this sort of coating all the time. It was either this or take a huge loss on the camera and buy and FLI. Worth a punt I think. The AOX tech is a huge advantage and something I wanted to keep.

The other images show the PCBs during coating taking place with masking of the tops of the pins and silicone being applied to the pins. The camera is back to together again and I am glad to say working.

Will this work last and prevent corrosion long term? That I don't know yet. I hope so and I will have to give it a try. A gamble for sure but to keep the advantages of the system with short back focus and AOX integration I think it is worth it. I'll report if it does not work.