After getting home from work on Monday evening I decided that I had to do some imaging, after all it’s not often that the sky is clear at the same time that the moon is out of the way. I also figured that I could set it all up start imaging and get a good few hours worth of data together before going to bed. So I rolled the observatory roof back to equalise the temperature and cool the telescope down quickly to ambient, while this was going on I got all the software running making sure that the USB connections were ok, USB connectivity in an outdoors enviroment is about the only problem that I have, any issues is usually solved by disconecting and then plugging the USB back in again. When it was dark enough I went through a 1 star alignment ( this is good enough as I plate solve the image and then sync the mount co-ordinates, RA and DEC from the result ) and took a few focusing shots, that’s when I noticed something more problematic than a dodgy USB connection, the star image was clearly wrong and that the telescope was out of collimation by quite a lot – that’s when I started calling myself a few choice names for being such a pillock. The telescope was out of collimation because the week before I took it apart to clean the main ( or primary ) mirror that was quite dirty and when I put it back together again I never checked and re-collimated the optical path, even a small misalignment between the primary and secondary mirror will cause the stars to be mishaped when imaging, it’s even more pronounced in a RC ( Ritchey Chretien ) telescope. So that was that, no imaging until the collimation is done.
I did however take one image a single shot of the star Regulus, Alpha Leonis, this image shows clearly the only issue with the ZWO asi1600mm Pro camera and that is the lack of an Anti-Reflection ( AR ) coating on the cover glass of the camera sensor, made by Philips and used by ZWO in this camera model.
The strange pattern around the star is the reflection between the protective cover glass over the sensor and the micro lenses over each pixel of the camera sensor, come on Philips what were you thinking, AR coatings is pretty well standard on any optical equipment even camera sensors.