Cooling issue of ASi071MC Pro ?

anderesa

I bought an ASI071MC PRO in Feb last year. I was very happy with the first results of this OSC (One-Shot-Color) camera behind my 14" RC scope. In the past nights I've used it as imaging camera behind my portable 4" refractor and run into the following problem which might be related to cooling.

Attached are screenshots of two frames, one from beginning of 60 minutes session, one from the end. I have pointed the Televue NP101 refractor the famous Markarian chain of galaxies.

The frames were taken with 60 sec exposure, gain 50 at -20C cooling. Can somebody explain the strange artifacts appearing at the border of the image. Note that these dark narrow bands only appear in the Light frames, not in bias or darks. I have not taken any flats.

Last night, I noticed the same problem again.

Thanks

--Sam

moson

Is this appears only at cooling? Will it changes? Did it appears only at begining or all the time?Is the strange artifacts the same every time it appears？

anderesa

Hi,

thanks for your questions. I will investigate this issue over the next clear nights. I have gai inspected using CCDstack software my series of 60 frames (60sec, gain 50, 1x bin, -20C). I can now tell that these dark lines at the edge of the chip started to appear at frame #30 and grew larger. I get the impression that these are narrow branches of ice. I have attached one more screenshot showing how the image of a star got spiky when crossing one of these dark areas.

I will keep you up to date on my investigation.

moson

Thank you very much for your sharing and feedback.

anderesa

I have used this OSC camera again last Thursday behind a completely different telescope. A 14" RC permanently mounted in a dome. I have taken frames up to 120sec exposure gain 400 and camera cooled to -25 to -30 degrees below ambient temperature.

The cooling issue was not present. I did not see any of these dark lines growing at the bottom of the chip. I have no clear explanation beyond the fact that the ambient temperate in the dome was about 10 degrees higher than when I took the pictures outside using the refractor.

Kind regards

--Sam

moson

We are glad that the cooling issue was not present. Thank you for sharing us again.