Water tightness and other musings

After building the observatory, I eventually got around to making it water tight. I just got sheets of rubberized canvas and made skirts around the roof's 2x4 frame so that the skirts cover the gap and extend a bit over the walls on all four sides. Upon water testing this with a garden hose it held up pretty well. Unless we have a rain with winds strong enough to make the rain come close to parallel to the ground, there should not be a problem (and this never happens in california).

The base of the walls, where the frame meets the asphalt of the roof was also completely sealed using roofing cement on all sides. This makes sure that water does not seep inside from the bottom edges.

I also noticed that I needed a bit more ventilation and added two more of those solar fans from solarwholesales.org. This time I added them at the apex of the roof so the air is being circulated by two fans in the center and two fans near the edges. This seems to be working very well as well. We've been having a few 100 degree days lately and the insides easily stay 15 degrees or so cooler than the outside.

Also for a while now, I have been contemplating making the system I have (Celestron C8 on an Atlas EQ-G mount. QHY8 and Hyperstar III) a little more versatile. Of course I could always operate the scope in f/10 config by attaching the camera to the back, but with a f/6.3 reducer/corrector, I could also operate it in that mode effectively giving me 3 different configurations. A quote from the Celestron website on the f/6.3 reducer: "For the Celestron reducer with a focal length of 284mm working at f/6.3, the spacing is 105mm. For Celestron accessories simply screw the reducer onto your scope and view at f/6.3. For aftermarket uses the compression ranges from about 0.7 at 50mm spacing to about 0.5 at 225mm spacing." Given this, I got the following items:
1) Celestron f/6.3 reducer/corrector
2) SCT to T-Thread adapter. Got the 55mm version
3) 10mm T-Thread extension

I already had a 20mm T-Thread extension and from the QHY dimensions



I have a total spacing as follows:
55mm Thread Converter + 20mm Extension + 10mm Extension + 20mm QHY8 = 105mm spacing between Corrector and CCD Chip. The QHY8 has 7.8 um x 7 .8 um pixels with 3110x2030 total pixels and 3032x2016 active pixels. Using this calculator and the active pixels, I get the following:
At f/2 Hyperstar setup: 16" FL == 40.64 cm FL == 406.40 mm FL == 199.8' x 132.8' FOV
At f/10 Visual Back setup: 80" FL == 203.20 cm FL == 2032.00 mm FL == 40.0' x 26.6' FOV
At f/6.3 FR Visual Back setup: 50" FL = 127 cm FL = 1270.00 mm FL = 63.9' x 42.5' FOV

I could also change the spacing using the various spacers I have and get these additional combinations ( comp = 1 - Spacing/FR FL. For Celestron f/6.3 FR FL = 284mm):
75mm = 1 - 75/284 = 0.74x
85mm = 1 - 85/284 = 0.7x
95mm = 1 - 95/284 = 0.67x

Which translates to:
At f/7.4 FR Visual Back setup: 59" FL = 149.86 cm FL = 1498.60 mm FL = 54.2' x 36' FOV
At f/7 FR Visual Back setup: 56" FL = 142.24 cm FL = 1422.40 mm FL = 57.1 x 38.0' FOV
At f/6.7 FR Visual Back setup: 54" FL = 137.16 cm FL = 1371.60 mm FL = 59.2' x39.4' FOV

I am not sure if these additional configs are worthwhile to attempt, but it's interesting nonetheless. Maybe I can use the FOVI in Sky6 to see what suits best. Although, I should point out, the Celestron documentation indicates a different range for the same range of spacing.