7.3.19 PST mod with binoviewer and low powers.

*

Thursday: Gales and rain so no chance to fit the inner skirt. I rotated the dome's shutters into the wind. Incredibly noisy in there with 40-50mph gusts driving heavy rain! Though there was no creaking, movement nor vibration. No sense that the dome was remotely interested in lifting.

Back to H-alpha, the binoviewers and trying to reach focus with a 1.25" star diagonal. I want to maintain low powers so I can see the whole disk but in stereo. Viewing "straight through" is acceptable in winter with low solar altitudes at 55N. Once the sun starts climbing it soon becomes very uncomfortable on the neck. So a star diagonal becomes essential for viewing comfort.

Careful examination of the AOK Swiss etalon adapters suggests they are optimized for minimum path length. Only the internal baffle separates the rear of the etalon from the nose of the PST filters. So even the most optimistic mechanical change is limited to reducing the path length by only 2 or possibly 3mm at most. So not worth the effort.

The lowest power pairs of matching eyepieces I have is 32mm. The highest powers are a pair of 20mm. So I need to reach focus using a GPC and some combination of eyepieces without losing the whole disk. Used "straight through" and without a GPC I have plenty of sky around the 20mm for 65x. Suggesting a pair of 15mm for 87x would still give me a slight ring of sky around the sun. 

Though I am guessing now until I can positively confirm this with a 15mm EP in the binoviewer. A pair of EPs is not necessary for this test unless I want stereo. The 15mm are unlikely to be a comfortable choice for binoviewing. The eye lens is small. Requiring much more careful head positioning compared with lower powers. 

So now I need to try the TS 1.6x GPC with my pairs of 32mm and 26mm EPs. Just to see if they push the boundaries of my demand for a whole disk sun. The ~100mm, glass path length of the binoviewers increases the power and makes diagonal use, while still reaching focus, only marginal.

Friday 8th Sunny but blowing a fierce and gusty gale up to 50mph from the NW.  At least that's blowing on the back of the dome. Even if I risked going up into the dome the noise would be tremendous. What a waste! I'd better go and see what it's like.

*