Hi Robin, Yes thanks, I did something similar by flashing a red torch into the scope whilst taking a sighting exposure. The slit showed up fine and I marked it with the PHD mask as suggested.
I’ve noticed a few shadows and elongated stars in exposures and the Lodestar field seems slightly offset. I guess that it’s simply down to the OAG mirror(s) alignment. I took a quick 15 sec exposure of M15 to ‘see what I could see’ and the attached frame clearly shows the dead space. Is that common or do I have to work on the alignment and focusing to perfect?