alcol620

Thanks William. I had an exchange of information with ZWO tech and they initially suggested the usual "moisture in the works" and dry it out. Later it was suggested get in touch with the retailer and get it sent back for repair. i bought the camera in a used condition so my optiona are limited. It worked fine over a period of months so I had no come backs on the seller, just my bad luck. I saw mention on another site to use dew heater on the camera to prevent moiture, but I ssume that this would only stop the camera outside glass from dewing up.

Hi William, I used the "Optical Wonder Fineoptical cleaning fluid" from Baader Planetarium.

Thanks again for your inputs. I have on 3 occasions cleaned the sensor as per the link that LandyJohn posted. Once when i took the old tablets out and dried them in the microwave, second when I dried them in a conventional oven and thirdly when I put new tablets in (after heating them in a conventional oven). If there had been moisture on the sensor I would have thought that my 3 attempts with dry tablets would have cured it. As symmetal suggests, maybe the camera is not sealed properly and allows dampness into the sensor area?

Thanks for the feedback you 2 guys. For clarification when I talked about cleaning the sensor, I now realise that I was only cleaning the sensor window. I am not sure that I have a job description that includes removing the sensor window to get to the sensor itself!! With symmetal's info on noise, I think I will stick with simply taking subs with the camera temperature set above 0deg C. Thanks again

A belated update. Since my last post I dried the existing tablets in a conventional oven, again cleaning the sensor. Replaced the tablets. Result no change. I bought new tablets from FLO, put them in the oven for an hour and put them in the camera. The new tablets were left in the camera for 10 days before the camera was next used. The result was no change, I still had the same noisy pattern in the same area of the subs with the camera cooled below 0deg C. Above this figure no noisy pattern appears. I have wasted so much time and mental effort trying to resolve the problem and have decided that the only option is to take subs a couple of degrees above freezing. I assume this will make subs a bit noisier but at least the noisy area does not appear? Sending the camera back to ZWO and losing it for 2/3 months and having to pay for whatever is found is not an option. Any further comments are very welcome

A quick update. Calibrated with new flats and stacked the new lights taken at +5degC and no suggestion of any noisy pattern on the master light. Awaitingthe arrival of the wider swabs and will then re-clean the sensor and bake the tablets as suggested.

Thanks HTH much appreciated. I took some flats earlier this evening at 5degC to remove the ise of ice forming and an initial look suggested no noisy pattern. Now taking lights at the same temperature to check out the result. I have "cleaned" the sensor a couple of times although not with a wide swab. Not of that cleaning has changed the pattern significantly, but I will get some wider swabs and give it another go. I will also give the tablets a bake in a conventional oven.

Hi folks. Followed the process of drying the inside of the camera. Took the 4 tablets out 2 minutes in the microwave, cleaned the sensor and put the camera cover back on, waited 48 hours for tablets to do their thing. Just took some new flats. First ones at +1degC 10 minute cool down time. Took the second set of flats at -13deg C 10 further minutes to cool down. Result, I still have this noisy area on the flats, both at 1deg and -13deg. I have attaached images to illustrate the noisy area on the flats, including the "rejection high" images produced by Pixinsight and the resultant master flat. Any further ideas folks? Help gratefully received

Thanks everyone, especially the fulsome answer from oddsocks. So many helpful and knowledgeable people on here. I am awaiting the next sunny and hot day to take the camera apart in my extremely hot and dry conservatory to deal with the tablets. Reassuring to know that you are still watching over us Steve.

Hi Folks first test completed. set target temperature at 1 deg and took 10 minutes to cool down, left to run for 10 minutes. Took 30 flats usual settings and stacked them. Result: no indication of the usual noisy area. Then cooled the camera down to -13deg left for 10 minutes and took another 30 flats. Result: the usual noisy area appeared. Job for tomorrow: dry the tablets and see what the result is. One thing that puzzles me it that if it is dampness inside the camera, why does the noisy area always appear in the same area of the image? I would have thought that the moisture would move around and the crystals, whatever they are, would form on different parts of the sensor?

Next on my list to try, but first I am checking if the problem goes away if I slowly cool to just above freezing. If the fails the the tablets will get dried. Thanks for you help.

Thanks Anthony Argon purge?

Many thanks Andrew, it didn't occur to me that could be the problem, although on a couple of occasions the issue didn't arise. I am cooling to -13deg in about 5 minutes for flats, dark-flats and lights. I assume that only cooling to 0deg will give more image noise. Next time out, if we ever get a clear night, I will cool down much more slowly like you suggest. You have raised my hopes of a solution to the problem that has caused the loss of lots of subs. Thanks again Ale

Hoping someone can give me feedback on the cause of spotty pattern on flats. This seems to have appeared a few weeks ago. Using Pixinsight, I have stacked around 30 flats callibrated with dark flats. The Pixinsight rejection-high image resulting from calibrating and stacking the flats is attached illustrates the area of distortion on the image. This also appears on the master flat image, to a lesser degree. Using the flat to calibrate the lights leaves slightly darkened area on the stacked light frame over the samea area as appears in the flats. I also shot the flats with the same settings but with the camera rotated. The distortion appeared in the same place on the image. Suggesting that the problem is inside the camera. I opened the camera and cleaned it. It made little difference, apart from adding a few dust motes. Is there some sort of problem with the sensor? the flats are 9s duration and ADu around 35000. I have attached an image showing the area rejection-high and a stacked flat frame. Feedback very welcome.

Thanks Adam, your help is much appreciated. Take care, Alec