After some instigation by Don, we all decided that the alternate site had a hope of providing us clear skies. Of course, with the new GWS, the chance for actual clear skies was slim. However, a big enough scope can see through clouds…. and a dob can slew faster than a goto.

I was the first to arrive, at about 9:05 pm, and Kerry pulled in before i had a chance to get out of the car. I selected a firm surface for the GWS and began assembling it. I chose the path just beyond the parking lot.

I put the top half on rotated 120 degrees but had it right 2 minutes later, for a setup time of 9 minutes from car to view. I aligned the finderscope, using the moon, and got it bang-on. I got a nice view of Venus as it was setting. A sharp crescent it was, even though it was directly behind a tree branch. A big enough scope can see through trees…

The finder works great on anything that has bright stars nearby. M57 came in without any fuss whatsoever. It was quite easy to see M57 even with direct vision. I think i might benefit from a right angle finder scope for the GWS,
to help where the sky does not have bright enough stars for me to see them without help. Perhaps an 8 or 12-inch finderscope would do. (Actually, i think a 3 inch at 6x power would be fine).

I was able to hold my camera at the eyepiece and get a few shots of the moon by hand, and was impressed it could pick things up and the auto focus could focus on the moon. I borrowed Don’s camera holder and put my Dimage Xt onto it. It weighed down the GWS but i eventually remembered there’s an adjustable clutch which was able to counteract the weight. I think a super-magnet would help too.

I was able to get 4 second time exposures of Jupiter and the moon. Then i tried zooming in… I was able to get the camera to focus on Jupiter, but at 3x zoom looking into the eyepiece things move about 1.5 Jupiter diameters in 4 seconds. Once you know which way to go, adjusting a dob to keep things in view is easy. Guiding to keep them stationary is not possible though.

I tried one flash shot, after warning all within earshot to close their eyes. I got a sharp shot of Jupiter, but the moons don’t show in a 1/1000 second exposure. Here it is. You can even see some bands on it. ( i wish i knew how to link jupiter_1ms.jpg here. it’s uploaded already)

We brought in M13 and i switched to a 10 mm eyepiece to get a 180x magnification. Even with that magnification it was about 1/3 of the field of view and pretty bright. That’s when the collimation issue started showing up though. It turned out that the collimation was a bit off, and we all agreed that steps should be taken. I thought the gentle bump it got when I put it down last Thursday might have thrown off the collimation but I now think that a truss Dob can be out in several different ways, and what I need is a rigorous collimation procedure at setup time.

First, the secondary mirror might not be directly on the axis of the primary and the view through the eyepiece might not go to the center of the primary, as viewed in the secondary. These depend more on the length of the struts and the selection of which strut to use in each position than anything else. I plan to mark them. Unfortunately it was pretty dark (even with the Hamilton skyglow bouncing off the clouds) by the time I wanted to collimate, and that made it kind of impractical.

Clouds blew in and blocked our view of the area around Linear, and although i waited about 20 minutes for them to clear, they were followed by high clouds that made spotting comets impractical.

I packed up at about midnight, and zipped home, with enough energy to spare that I can do it again. I plan to try assembling the scope a few times on my porch and checking how the collimation changes. I am keen to see through all manner of eyepieces and at high magnification, once things get straightened out.