Primary Mirror Movement

[austen4]

Hello all,

just wondering if I wanted to move the primary mirror up the tube by a small measurement like 20mm - 30mm would I need to cut the tube or can I just get new screws and springs?

Thanks

[umadog]

It depends on the design of the cell. With some cell you can just drill some more holes and move the cell up the tube. Alternatively, you may be able to modify the cell with different springs and longer collimation bolts. Cutting the tube is drastic because there's no going back. Another possibility is to move the spider and focuser down the tube. You'll end up with an ugly hole next to the focuser, but that can be patched up.

[Sam]

With my 8" scope moved the mirror by screwing in some blocks into the base of the mirror holder (can't remember the proper name) and then screwed the collimation screws into the blocks - I did it like that so I could go back to how it was meant to be if needed.

[austen4]

With my 8" scope moved the mirror by screwing in some blocks into the base of the mirror holder (can't remember the proper name) and then screwed the collimation screws into the blocks - I did it like that so I could go back to how it was meant to be if needed.

I see, so you added a block to push the mirror up the tube? So the block acted as a booster.

Austen

[austen4]

It depends on the design of the cell. With some cell you can just drill some more holes and move the cell up the tube. Alternatively, you may be able to modify the cell with different springs and longer collimation bolts. Cutting the tube is drastic because there's no going back. Another possibility is to move the spider and focuser down the tube. You'll end up with an ugly hole next to the focuser, but that can be patched up.

Im not planning on cutting the tube but hopefully I will not need too much back focus and can solve it using new screws and springs.

Austen

[Stephen]

I added some stiff springs and longer bolts and moved the mirror in my 200P approximately 9mm up the tube without drilling, cutting or anything scary like that

[austen4]

Ah ok, where did you get them from. I have heard if I rung up FLO they would have some maybe?

Thanks

[Stephen]

FLO may well be able to help. I used the following:

Bobs Knobs - I bought them initially to improve the collimation experience. Once I added the springs though, I found I could use the locking bolts as collimation bolts (longer) and I did not require the locking bolts any more because it held so well.

strutsdirect.co.uk parts SC229

See this thread http://stargazerslounge.com/diy-astronomer/47872-going-mod-my-skywatcher-130p.html

and this one http://stargazerslounge.com/discussions-scopes-whole-setups/148344-replacement-mirror-cell.html#post1885326

for pics and info and stuff

[Sam]

I see, so you added a block to push the mirror up the tube? So the block acted as a booster.

Austen

yep - pretty much