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Wednesday: Clear and bright again after a cool night. Only a little, distant mist today.
10.00am 49/45F [Out/In] Nothing visible in white light.
10.15am 50/46F Sun at 21° altitude. A quick scan in H-a shows proms at my 4.00, 8.00, 9.00 and 11.00. The 4.00 and 9.00 are the largest and best defined. GONG not showing much on the disk except for a dark smudge at 4.00 . I'm only seeing some subtle light areas.
11.20 53/50F Sun surrounded in a flood of red light. So I cut out a stop ring to the theoretical 120mm aperture resulting from the PST optical limitations. The 150/8 becomes a 120/10. It had no visible effect.
12.00 56/52F So then I removed the 6" tailpiece and sprayed the bare aluminium matt black. It had been too cold to paint until now. I have left the tailpiece to dry off outside in the sunshine. To avoid fresh solvent fumes inside the OTA.
The dome plywood panels inside are showing similar temperatures to yesterday's. 90F when facing the sun. Higher panels have higher temperatures. 90F when direct sunlight is shining on them through the slit. The unlit panels are all in the low 60s F. The open shutters are blocking the sun from reaching the two vertical rows of overlapped panels.
I have some wooden louver panels about 1.25m high x ~60cm wide. Which I thought I could incorporate into the dome walls to minimize thermal differentials inside and outside the dome. With the veranda doors open I could generate a cross draught. "Dome seeing" is the result of warmer air rising through the observing slit. If the air in the observatory can be kept cooler then the gradient won't be so deleterious. Shading the southern quadrant of the obs. walls might have similarly, beneficial effects. Shading the dome is much more difficult due to its shape and need for rotation.
14.40 60/56F breezy now. The sky just arrived from the NW in the form of rippled clouds. I'm getting some excellent views of clouds passing across the sun in WL. More confusing in H-a because they affect the sharpness. Might as well give up.
11.20 53/50F Sun surrounded in a flood of red light. So I cut out a stop ring to the theoretical 120mm aperture resulting from the PST optical limitations. The 150/8 becomes a 120/10. It had no visible effect.
12.00 56/52F So then I removed the 6" tailpiece and sprayed the bare aluminium matt black. It had been too cold to paint until now. I have left the tailpiece to dry off outside in the sunshine. To avoid fresh solvent fumes inside the OTA.The dome plywood panels inside are showing similar temperatures to yesterday's. 90F when facing the sun. Higher panels have higher temperatures. 90F when direct sunlight is shining on them through the slit. The unlit panels are all in the low 60s F. The open shutters are blocking the sun from reaching the two vertical rows of overlapped panels.
I have some wooden louver panels about 1.25m high x ~60cm wide. Which I thought I could incorporate into the dome walls to minimize thermal differentials inside and outside the dome. With the veranda doors open I could generate a cross draught. "Dome seeing" is the result of warmer air rising through the observing slit. If the air in the observatory can be kept cooler then the gradient won't be so deleterious. Shading the southern quadrant of the obs. walls might have similarly, beneficial effects. Shading the dome is much more difficult due to its shape and need for rotation.
14.40 60/56F breezy now. The sky just arrived from the NW in the form of rippled clouds. I'm getting some excellent views of clouds passing across the sun in WL. More confusing in H-a because they affect the sharpness. Might as well give up.
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