Saturday, August 23, 2014

collimated the AstroMaster 114

After closing the Telescope Repair Man booth in the afternoon, I drove about the park looking for Heather. Spotted her and her party at the top of a hill near the entrance. Told her I wanted to have another go. She was willing. We discussed timing given the banquet was starting at 5:00 PM, to be followed by the keynote and prize draw.

After the dinner, Heather dropped off the 'scope. I had a quick look but covered it back up for Porco's talk.

Beautiful skies greeted us as we emerged from the big tent. I hurried back to the site. Everything was soaked! Even though covered, Heather's 'scope was dewed. Went through the collimation process again after drawing the secondary mirror back. Asked Phil to corroborate the process with the Hotech laser. That's when we spotted something unusual: a lens at the bottom of the focuser tube.

Suddenly it all made sense! The primary mirror was spherical. This was a corrective lens. This is what caused the Hotech laser beam to hit the primary as a blob, spread out, not a point but a non-circular blob about 1 centimetre in diameter. I also found the lens was fogged. Briefly warmed it with my portable hair dryer—until the power went down in our sector. Finally adjusted the secondary to make the laser exit out the focuser tube. And, while spread out further, I could see the return beam. Fine-tuned the primary and finally had a look.

Arcturus looked good! Sharp, easy to reach focus. Pin-point stars in the field. And just then Heather returned. She was blown away by the view. I showed her the Andromeda galaxy. A very nice view. I was impressed. And finally Mizar. Wow. Tack-sharp stars, when kept near the centre of the field. Beautiful resolution. Mizar A and B easily split, Alcor obvious, Sidus Ludoviciana in the middle. Heather was thrilled.

Me too.

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