10" f/8 Arachnophobia 3 [Final cut.]

*************

I eventually decided that it would be much easier [and quicker] to use a cheap mitre saw rather than use the lathe. It would have taken far longer to set up properly than to make the actual cut on the vertical slide. With the workshop being so cold I didn't want to spend any more time out there than strictly necessary.

Here is the set up: Collimation nuts tightened against the spring for stability. Only a thin sliver was required to true the 45 degree face. Clamping the spider down into a vice with a G-cramp ensured stability and accuracy of cut. It is difficult to see here but the wedge is very thin at the far end.

 Here is the spider with the sawn face now at a true 45 degrees. The woodcutting blade worked well on the machining quality nylon.

The secondary adjustment allows for collimation regardless of the true angle on the face. Though this is likely to result in a larger obstruction than necessary if the holder is badly skewed to compensate for errors in the 45 degree angle.   

 This image shows the spider vane hub being reduced in the lathe to a diameter of 48mm.

The surface is now turned clean all over the entire circumference. With the vane fixing V-slots still deep enough for perfectly adequate stability.

Any burrs or rough edges are easily cleaned up with abrasive paper.

The final image is of the secondhand 50.5mm secondary support reduced to 48mm diameter. With the secondary holder cylinder further reduced to 47mm to match the elliptical secondary mirror. 

The newly-bare plastic will eventually be sprayed matt black to kill any reflections. Though this will have to wait until the weather is warmer.

I am reliably informed that this is/was a Beacon Hill spider.

I spent some time adjusting the thin brass shroud to match the secondary evenly all round. Then bored and tapped and countersunk an M4 thread for the three radial fixing screws. Then I couldn't find any suitable CSK screws. They were all cheese head.

As if to egg me on there was a brief glimpse of Jupiter, Venus and a very fine crescent Moon at dusk after a horrible day of cold, wintry and windy weather. A soon as I took the 8x42 binoculars outside the sky quickly turned strangely misty and it clouded over again.

Click on any image for an enlargement.

************