Viewing Report 16th April 2020 – IMT3 – Final TPoint again…..

Viewing time period – 20:59 – 23:42

Here is my workflow so I can repeat each night until this is finished.

Open dome – done

cool down – done

turn off dehumidifier – done

turn off fans on scope – done

find home – not needed

focus – done 59,659 clear – done


slew and sync to nearby star – done at 21:06 as not dark enough before then

Not quite dark enough yet

make sure scale is correct -done

make sure image link to all sky database is selected – done

All Sky Image Link settings

start TPoint run at point 93 – done @ 21:10

Complete TPoint – 231 points done at 23:46 including checking 5min unguided exposure which was fine

Final TPoint plus Super Model

Turn on Dehumidifer – done

So what did I learn tonight? It was worth doing the TPoint model. The resulting pointing accuracy is much better with objects being almost centre off the chip. Unguided images on the 12″ look good at 5mins, I will try longer when the clouds and rain disappear. That following a documented approach helps as above. The adjustments to the worm and the loose weight helped. That fixing the dome rotation slippage on the encoder today helped.

TPoint completion of 231 points
Final model applied
Polar alignment report
Command line view
Protrack on
Tpoint model on sky
2min unguided image through OS12″
5min unguided exposure through OS12″

I mentioned above the dome slipping on the encoder, this was because of the small weak spring that is used on the dome, which is not good enough and over the past year has stretched beyond its limit. This means as the dome rotates and the dome shudders due to the joins in the dome not being flush (another issue) and thus the spring is stretched. This meant that some of the time the encoder wheel seen below was not touching the dome and therefore lost around 30-40 degrees. To rectify I have temporarily stretched and tightened the spring which we will replace later with a more suitable one.

Encoder wheel
Encoder spring now stretched to fix problem