Thanks partly to you h0ughy getting the cooled DSLR and the results it obtained, I was sure it was worthwhile going to all this trouble to cool the 5DH.
Last night had a few problems with intermittent cloud but still managed to get this.
Large image 1.4MB Image scale is 0.94" per pixel.
Canon 5DH, TAL200K 1800mm f/9. Hutech LPR filter.
All at an ISO of 1600. 1x30s, 4x(1, 4, 8) min. Converted from RAW to TIFF and corrected for flats with images plus. Aligned with Registar and generated an LDR from this data with EasyHDR.
The fridge was at 6C (ambient 21C) at the start of the night and dropped to 3C (ambient 14C) by early morning. I used an ISO of 1600 to see how much the noise was suppressed. What is really interesting I left the cooling fan on the Peltier heatsink run at full speed and there were no vibrations at all to intefere with image quality.
Next I will improve the cooling capacity to get a bigger temperature difference.