Hi. I have recently purchased a used ST-2000XM with a CFW9 which to my disappointment, is starting to look like a bit of a mistake. Everything seems, to some degree or other depending on its brightness to be surrounded by a halo of some sort. I am going to attach one of a series of images I took last night of M42. All filters exhibit a similar sort of artifact but I'm only going to upload this one - a full-field shot of M42/43 and NGC1975 taken with an Astrodon series 2c red filter. The artifacts you can see occur on all stars in all filters to some degree or other. It isn't blooming - at least I don't think so. The reason I say that is because the images show patterns - and the patterns are circular rather than linear. I can't blame my scope. It's a Takahashi FSQ85 (the BabyQ - one of the best refractors around) and is quite clean. I can't blame filters. They're Astrodon Series 2c and as clean as a whistle. I have also removed the filter wheel and - reluctantly but out of some growing desperation - I have cleaned the optical window of the camera and it, too, is now as clean as a whistle. I am now left with only one explanation I can think of - that there is some coating on the sensor itself. That scares the pants off me because of the risks that opening up any CCD chamber entails. Does anyone have any similar problems. More importantly, any solutions? Peter
Peter, did you bake the dessicant? It could be the sensor is fogging up when the cooler is on. So, you have to remove the dessicant plug, put in the dummy plug (assuming you have one). Then take off the o-ring from the dessicant plug, and bake it at low heat for a while. This dries out the dessicant, and readies it for re-use. Then, put the o-ring back on, replace it in the camera, and away you go. Am sure there are instructions in the manual.
Hi Colin. No I haven't - I was assured the dessicant had been baked quite recently before I bought it. But it's something else I can do before resorting to more drastic measures. Thanks for the reminder. Peter
Colin, It's daylight here, so doing a star test will have to wait a bit. But I think we can eliminate frosting on the sensor. I've run the camera down to -10 degrees and opened up a longish exposure so I can look down the barrel at the sensor. There is no visible frosting at all. In fact the sensor looks pretty good. I'll do a star test tonight if the weather permits but my present best-guess is that frosting is not an issue. To be sure, I've removed the old desiccant plug and screwed in a replacement I bought from Farpoint using their little desiccant cartridges. More reports to follow! Peter
I've pulled this image out of the Lum stack because it definitely shows the foggy cloud surrounding this moderately bright star. Its 44 Orionis which is a double - +2.7 and +6.8 so a mid-range sort of star for basic luminosity. You can clearly see the reason I don't think this is blooming. Peter
It's clearly not blooming. If it's not frost, then it's simply dirty. Check the filters, amd the outside of the CCD chamber window to see if they need cleaning. Be sure to look up optics cleaning procedures before attempting to clean them. If the inside of the chamber needs to be cleaned, then I strongly recommend sending it to Bill @ service.
Hi Doug. Thanks. As I said in the top post, every surface outside the CCD chamber is clean. I've replacd the dessicant plug and will star-test again tonight. If the resuls are no better I'll do as you suggest and send it to Bill. Peter
