readied the Dob

I had offered to operate one of the DDO Dobsonians. Randomly, I had selected Ian Wheelband's 12½" unit, with foam-covered truss-tubes and laminated wood.

Mr Mortfield said it might be off. Possibly something wrong with the aluminium tubes. I said I'd look into it. I would use my film tube collimator.

6:48 PM. I was done the SCT set-up. Headed to the big Dob.

Noted the primary was rather dirty.

First impression of the collimation was that it was way off.

I reseated all the aluminium tubes. Top and bottom. A couple were poorly set. It improved the alignment. But the collimation was still off quite a ways.

Aligned the secondary. Better, again.

But I could not seem to move the primary. The adjustment screws did not want to travel any more. And when they did, seemed to have little effect.

Should not the bases to outward? The triangle plates seemed to be the wrong way. I rotated them 180 degrees.

And there was a plastic ring flopping around. But when I adjusted the triangles, I noticed some double-sided tape at the points. Ah ha. I would discuss this with Ian...

Shot some photos.

Tom L arrived. Asked if he'd help: he watched the eyepiece collimator while I tried to change the primary screws.

We considered loosening pins holding the mirror. Grabbed my spanners and wrench from the car bootlid. But the pins wouldn't move. Then it dawned on us that the primary mirror screws were simply too far in.

We turned the OTA upright. And I turned the primary screws way off and coaxed the mirror back. It worked! Still in the sling. I tapped the rocker box to get the mirror settled.

The mirror was now not jammed up against the pins. Yah.

Tom said we were good. I looked. Awesome!

Tom agreed the mirror needed cleaning.

Second 'scope ready!

I moved my car to the parking lot.