I wanted to keep you updated on the status of the 20" iDK Astrograph in Namibia.
It is performing fairly well, but there are some issues nonetheless:
- Collimation is okay, but not spot on: It looks like the secondary is not exactly centered in the tube. Also, there is some tilt in the system. Combined, those two lead to some changing star shapes while cooling down.
- While the observatory allows to image down to about 21° above horizon, it is advised to keep the minimum altitude to about 40° (you can do so in the Imaging Request Wizard). Keeping very low bloats the stars up and give a bigger surface for wind gusts.
- The CCD in our FLI Proline has one defective (hot) column, plus some minor aging signs. Keep a good eye on the calibration. I really recommend doing it yourself, the automatic calibration is far from perfect. Also, it is preferable to take more dithered frames and stack them to correct out the hot pixels and column. So, it might be better to shorten the exposure time for the single frames and raising their number while keeping the total exposure time constant.
I plan to fix point 1) in october on site. As for the CCD, I am considering to buy a new GSENSE 4040 CMOS camera, which would cover the exact same area with the same 9 micron pixel size, but would be far more sensitive and supposedly be easier to calibrate. I honestly need to see how things are going onwards as it would be a serious investment 😅