[avandonk]

Spent some time carefully collimating the TAL200K last night with the help of many mozzies. Thought I would do a quick HDR of the Jewel Box as a test early this morning just before beginning of twilight.

Details
Tal200K FL 1800mm f/9, no filter. Canon 5DH.

All at an ISO of 500. 8s, 15s, 30s, 1m, 2m, 4m. Converted from RAW to TIFF and corrected for flats with images plus. Aligned with Registar and generated an LDR from this data with EasyHDR.
As you can see the HDR process tends to preserve star colours. The EQ6 also seems to be tracking fine at 1800mm as I really did not have to use Registar to align as there was virtually no drift over the full set of exposures except for the last 4m image. At 1800mm focal length the image scale for the 5DH is 0.94 seconds of arc per pixel.
The second image is a 100% crop. The third is a full frame defocused image that gives some idea of the state of collimation and star colours. I actually collimate by viewing a defocused bright star centrally through the camera viewfinder, adjust and then take a defocused image. Repeat until the image is nice and symmetrical for the central star.

Bert