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Grainy and false color image with ASI120MC #180
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I've just started using Allsky, and I have almost the same camera (mine is an ASI120MC-S). I had the same issue last night...all of a sudden about mid way through the night (based on the video), it suddenly changed to a blueish tint. And towards morning it got grainy, almost looks like it is looking through a screendoor. |
Is this not the same as doing a dark frame within the GUI? |
It is not because of dark file. I am using a good "dark.png" image without any problems. What you see in pictures is not related to dark images. Appears and disappears randomly even on the "image" taken from the camera before it was processed with the dark. It is some kind of blue "grid" with totally different hot pixels from the dark taken. |
I forgot to mention, i am using three darks, taken at 10, 20 and 30 degrees darks changed when chip sensor exceed +/- 5 degrees around this temperature values. But it has nothing to do with dark changing. This problem appears totally random and is a camera issue(in my opinion). |
Well last night I started getting the same issue. It started the run with the blue/red/green dots and went all night. Powering it done and playing with the camera settings did nothing to fix it. During the day when the gain and exposure is at 0 no problems. Tonight I am going to limit the exposure and see if that helps. |
In this evening i have seen the camera with that blue image full of hot pixels. Quick, in this state i make a dark frame. I used this dark to substract the hot pixels in the "startrails" software with very good results. So, if i will catch a fireball on this bad state of the camera i have the posibility now to clean the image and see the stars, even if the image remain bluish. |
I am still doing testing on mine I finding that the Dome is degrading my photos a lot. Some of my first runs without the dome looked very good. I have the dome off as of 6-2-20 it ran last night and has a lot less hot pixels. Tonight going to run at gain 100 and auto expos.\ no dome. My photos are at www.dentonknifeworks.com |
I have (fortunatelly) a glass dome. Acrilic ones, in time, become less transparent and will make the quality of images lower, but i think it is noting to do with hot pixels. The images will become a bit blurry, i think. The real problem might be the temperature of the sensor... i think. I am thinking to place a small fan to cool down the ASI camera. Now, because ambiental temperature raised, i have more frequently this problem with bluish image and hot pixels. I will check this... |
After more testing I agree the dome is not producing the Hot pixels. |
I have seen the same. When the blue image appears, also new hot pixels(a lot of them) are shown, This ones, does not fit the usual dark and you need a new dark for processing this. I think this is a hardware problem related with debayering process inside the camera. I am thinking to detect when this appears and reset the USB, because the problem dissapear only if power off/on the camera. Also, in the next days, i will relocate the fan which cool down the PI to cool simultaneously both, pi and the camera. |
The problem I see with the dark frames is that they vary with the exposure length. |
Well at this point it looks to me that the ASI120MC-S in this texas heat is not good for Allsky. |
I've found the entire dark subtraction process with this software to be a bit of a hit & miss exercise. |
Ok so I renamed the dark.png and let it run last night no difference at all it like the dark file is not doing anything at all. |
That sounds like a useful result. I don't think you have to restart the service, but did you try that? The code does the following when it makes a dark frame: Make sure your config file specifies the dark name (it should be dark.png) |
Looking at your dark, and the image, they looks like they are vastly different (ie maybe you did the dark when it was cooler?). Given the temperatures you're talking about (40+ degree sensor is pretty hot) - I can guarantee you're going to be way cooler hanging off the back of a telescope vs being in a box. I looked at this a little - there are two main issues. The code library being used does not store meta data in the image files (unlike a FITS file for example). So neither the exposure length, nor the sensor temperature are stored in the image files. This makes coming up with a routine a bit messy. I'm thinking that either there needs to be a routine to encode the information in to the filename (which causes other issues), or adding a library to embed metadata in to the images (like EXIF data), which could then be used to be able to dynamically apply an appropriately scaled dark. |
I am using three darks. From the original "capture.cpp" i export in a text file the sensor temperature. Then, PHP read the value from the file and is changing the dark.png with one of three darks taken at 10, 20, 30 degree celsius +/- 5 degrees hysteresis around these values. But as i said, that bluish and pixeled image does not match any of that darks which are all good and is working very well in allsky dark substraction when the camera is working normally. Didn't had time to make a code to detect that blue image and switch to that specific dark which is good in that condition. |
I am thinking your on the right track on the Temp. I added a fan to the box today I will see if it runs cooler tonight. At looking at the frames taken looks like 40c to 50c on temps. If the fan dont work I will put the cam on the scope and see what temps it gets too and recheck the bad pixels on it. |
@RobertG73 I have the exact same issue as you. |
For my past experience with the asi120. It not a good fit for a raspberry pi. Had nothing but issues with it. Worked with vendor and now I upgraded it to a asi224. Much better quality and works better. |
Thanks. |
Unfortunately not, I’m having the same issues with my ASI120MC-S on a Pi 4 4 GB. The cam works fine on a second Pi 4 as a guiding camera with the INDI drivers. |
I put my ASI120MC-S back on the telescope and works fine. So I went with a HQ pi Cam and used the converted code. |
This issue is from an older release of the AllSky software; the current release uses a dark library with dark files based on sensor temperature which improves dark subtraction. Other issues above might be hardware related. |
Hi, i have a strange issue with images taken by my ASI 120 MC. There are two types of bad images which appears totally random and also last for hours when appears. in some nights doesn't appears at all... I attach a photo with both issues. Anyone knows what could be the problem and how to fix it?
Both cases disappear only if i reboot the PI and if i only restart the allsky service this problem doesn't disappear.
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