I've got an FW8G-STXL that has performed flawlessly up until now. All of a sudden, only the stars near the center of the frame are close to focus and those around the edge are out of focus to varying degrees. The images from the main camera sensor are fine. It's as if the guide sensor or reducer lens are tilted. Have you ever seen anything like this before? I've always handled the camera/filter wheel very carefully and it has never been dropped. I haven't opened up the filter wheel to investigate yet, but I can if needed. Worth noting, the camera/filter wheel is being used on a Takahashi BRC-250 that has a 100mm imaging circle. Also, last night I confirmed the chip is just outside the light path to the main CCD and I tried refocusing the guider; neither improved the situation. Let me know what you think. Thanks, Nick
Hi Doug, Happy New Year! The mirror seems firmly in place, but the lens is definitely tilted. It appears the lens has 3 or 4 small dabs of glue(?) holding it in place and one of them cut loose. I snapped a photo and you can see a gap on one side of the lens (highlighted in red). I bought the filter wheel from Woodland Hills back in 2020 so it's out of warranty. Any chance I can get this repaired?
Yes it is easily repaired. The "glue" is high quality RTV. We use three spots to avoid stressing the glass, which could result in optical distortion. This is something @Bill could easily do, if he's available. Otherwise you'll need to RMA it to Ottawa.
RTV = Room Temperature Vulcanizing Silicone - the flexible rubbery stuff used for bonding glass to other materials.
Thank Doug and Colin. After studying the mechanism I realized how easy it would be to repair, and a fresh tube of clear RTV will be a fraction of the cost of shipping alone. Wish me luck!
If one searches "RTV without acid" there are products that do not release acetic acid fumes as they cure. For use around optics / electronics one should consider a neutral cure version.
Tim - good point. I think since a tiny dot is needed for this purpose, it probably doesn't matter. That said, I've had a few folks mention Permatex® 59803 Ultra Black Gasket Maker - it is a neutral cure RTV available at a lot of auto supply places. It doesn't have acetic acid, and they market it as "sensor safe" for auto electronic sensors.
