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About this blog

In my other blog I'm making a stepper focus motor. It will drive my new Moonlite 2" focuser which I can't wait to fit so I can use the few widefield wideangle 2" eps I've collected over the past few months. But before I can fit it I need to move my secondary mirror and as it's a bit ropey I bought a new smaller one (18% obstruction vs og 20%) which means I need a new secondary mount too. It all needs to come together together! 

Entries in this blog

 

Disaster- a wasted day

Ballcocks! 😞 Well you learn something new every day and I learnt today that you shouldn’t use aluminium formers to silver solder brass... It started off so well as well   Guess I’ll be starting that again from scratch- ballcocks

markse68

markse68

 

Spider hub

The spider hub came together tonight- bit of a mare as it’s glued together with high strength retaining compound which gave me about a minute to assemble everything and try to align all the screw holes 😳- needless to say it was a right panic not helped by a friend deciding to strike up conversation at the critical moment. Wish I hadn’t rushed it as it’s not perfectly aligned and not much I can do about it now but it’ll do I think. It’s getting a bit hefty though which is a worry- 200g alrea

markse68

markse68

 

Big improvement- this will work I think

Disappointed with the function of the design yesterday due to friction issues I’ve modified it- it now has only one spring and 4 screws. The spring keeps the indexing screw in contact with the v-groove in the mirror cell top plate. Adjustment is achieved by slackening all the screws then adjusting the tilt to focuser angle with the indexing screw, and the focuser-axial rotation with the 2 side screws then all 4 can be nipped up to lock it which is better than just relying on the springs I think.

markse68

markse68

 

It kinda works 🤔

Completed the screw adjuster plate so I could give the swash plate mechanism a try- it does kinda work but I think there’s too much friction in the swash plate and the ball joint- a ready made Igus part. So I’m thinking they might need to be ptfe and polishing the back of the mirror cell top plate will likely help. But getting there I think... 40749B06-F1D5-43DB-9E9C-3ACA97EC0561.MOV

markse68

markse68

 

Starting to come together

While I’m waiting for the 3D printed parts for the stepper focuser I’be been making a bit of progress on the secondary mount. Here’s the top plate of the mirror cell with the ball joint and the rotation locking grooved insert and a video to show how it’ll work. You’ll have to imagine the mirror tube as that’s next on the todo list 😉 69104768-5797-42C4-ACB7-BF8EE2E23CF9.MOV

markse68

markse68

 

The design

I like the original secondary mount on my Fullerscope- it cleverly separates the tilt from the rotate of the mirror but it’s a bit crude and too big for my new mirror. The new design is meant to be kinematic and I think it is 🤔 It tilts the mirror on a ball joint and axial rotation is locked by a sliding key way on one of the adjuster screws. There are 2 adjuster screws opposed by strong springs and the second screw and the springs bear down on a nylon swash plate to make the action smooth. The

markse68

markse68

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