My problem is that when I’m doing any imaging when the object is pretty dim (mainly narrowband OIII and SII images) I have a problem with the bright stars in the image leaving a dark trail immediately to the right of the star position. It looks like a dark tail after all the brighter stars. I had contacted Alan Holmes with the problem and he seemed to know what was wrong but little be-known to me was that at that time they were right in the middle of the acquisition of SBIG by Cyanogen. He said that they didn’t have the time to work on it and to get with them later on. I was wondering if you could help me with it. I’ll enclose two links to “Drop-Box”. One is a raw image that is uncalibrated and the other is a mean average of 6 calibrated exposures which show the problem much better. There is a lot of vertical banding also but as I understand it, it’s common with all the interlaced chips and I can deal with it in post processing, but the black tails on the stars is a problem. This one is the Mean average of 6 exposures, 30 minutes each of SII.. It’s 40 megs so….. https://www.dropbox.com/s/odejs0mc3z765d3/Mean Sum_Ha.FIT?dl=0 This one is a single exposure, uncalibrated, 30 minutes also. https://www.dropbox.com/s/3hwauysvxtwad34/SIIRosette_300_E.02281.fit?dl=0 Alan said something about a problem with an amplifier… I don’t remember, but I realize I may end up sending the camera in to you. Whatever it takes. Thanks a lot, Dan Wilson
FYI. I have exactly the same problem. My camera is currently enroute to SBIG for a fix. Don't know the cause yet. Regards, Marcus
Good to know I'm not the only one I guess.... LOL. Please keep us posted on what they find and how much it cost! Thanks, Dan
Doug and or Tim; I've been waiting to send my camera in for this problem. Has the one you have been fixed? Problem found? Thanks, Dan
Sorry it's been a very slow process. We did a whole suite of tests on the bench, invented a star simulator... all kinds of things, and can't reproduce the fault. It's extremely hard to resolve a problem that you can't see. My current plan is to test the camera on my telescope with real-world stars, but this was held up for a while because my Paramount was having an electrical problem. I think I've finally got that fixed, and I'm just waiting on some clear weather to run the tests. Naturally the weather has been really awful ever since I got the mount working again...
If my camera is acting the same as Marcus's then the best way to reproduce is to use a narrow band filter SII or OIII on a signal poor region that has some bright stars in it. The exposure time should be enough to get the stars near saturation and signal bad enough to get the vertical banding.. Then you'll see dark cometary tails coming off of the RH side of brighter stars horizontally. The vertical banding being inherent to the KAI chips, can be corrected for, but the dark tails are another story. Hope this helps! Dan
Doug, My problem is exactly like Dan's (and another I've seen). The sample FIT image of NGC 1365 that my distributor supplied you 4 months ago (resupplied below) was a stack of 4 x 15 minute subs through a red filter. You would need to apply some DDP of course (eg via CCDStack Auto Scale). The dark shadows stand out like the proverbial dog's b***s against the sky background (of 163 ADU). This is not hard to reproduce. https://www.dropbox.com/s/6jeu64ggv9f81hp/Median%20RedNGC1365_TrailingTails.FIT?dl=0 Regards, Marcus
Since repairing my Paramount two weeks ago we've yet to have clear skies for testing. Once I can replicate the problem we'll have something to work with.
Was able to get some data last night. Took a couple of hours to get everything working again (had trouble with focuser), so by that point only an hour of dark skies. Got some data and am analyzing... probably will need to get some more.
Not to my satisfaction. It may be clear tonight, if so I am going to rotate the camera to get the diffraction spikes out of the way, and do a lot more exposures. (Have to fix the PEC curve too, was lost when I replaced mount controller.) In looking over the schematics sith a fine-toothed comb, I came up with a possibility. This portion of the circuit has the right time constant to make an artifact of that length. It may or not may be relevant, but it's something to investigate.
Good deal Doug.... I'm going to have to send my camera in as it's filter wheel, (either the motor or controller card) has gone belly up in addition to the problem we are discussing on this thread. Would it be best to call Tim Puckett to get the ball rolling?
Dan, That's really up to the boss. I know Doug is swamped so it might be tomorrow to get a reply. Here is Bill's repair contact info below: bill@sbig.com (805) 308-6979 Anytime I can help feel free to call regardless.
Most repair items go to Bill at SBIG Service & Repair. They only come to Ottawa when we need to do an engineering investigation.
