23.08.2022 60MT etalon trials continue. AR3085

 *

Tuesday 23rd Bright start then overcast then sun in the afternoon. Thin, high cloud with a gusty wind. Max 76F.

I started the morning by collimating the 150mm objective and FT focuser. Both had been removed and replaced when I shortened the main tube. They weren't far out of alignment but are better now.

16.35 76F. Windy! First decent image today. Though hardly sharp and detailed. Complex light bridge is visible over the umbra on lower left spot. I am hoping the seeing conditions will improve. I believe the image brightness is more even after collimation.

 17.00 Seeing conditions remain unchanged. I am struggling to find best focus and best tuning. So I have paused for afternoon tea. 

 It is ironic that I have never previously succeeded with a 2x Barlow. It was always "too powerful" for the seeing conditions compared to the GPCs. It effectively doubles the the focal length to 3m. Now I have the Barlow sitting in front of the camera. 

 17.27 Another image rescued from the shaking mush on the monitor. The first hint of magnetic bristles.

 The one thing I haven't done [yet] is to rotate the Lunt Blocking Filter relative to the etalon. This is something I always did with the PST etalon. I even marked the BF with a bit of red tape to ensure "correct alignment." 

 I just tried this and believe I found a best orientation where the field was darkest and most even. Unfortunately the image shaking and softness on the monitor does not help.

18.02 I added a long aluminium tube and lifted the camera end of the stack with a cord. Crude but effective in combating the obvious sag.

18.21 Seeing steadying but not much sharper. Thin, high cloud is probably to blame.

 

 18.30 Image has gone dark. Trees and cloud.

The end of today's trials 

 

*