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Six Spring Mirror Mod


laser_jock99

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While installing longer springs in my 12" Newtonian (to shift the mirror up the tube 15mm)it occurred to me that the useless 'mirror locking' bolts could simply be replaced with three more compression springs for added spatial stability of the rear mirror cell.

Mirror cell with 'six spring mod'. The white 'locking' knobs now act merely hold the extra three springs in place (will be replaced in due course with short M6 socket button heads)

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The 'locking' bolt does not touch the mirror cell. Just the springs keep extra tension.

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The longer spring I used compared to a standard length 'Bobs Knobs' strength spring.

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The modification certainly seems to have reduced the minor mirror shifting that I was seeing even with 3x Bobs Knobs springs fitted. Losing those valueless 'mirror locking' bolts was of no consequence- all I found they ever did was screw up a painstakingly achieved collimation!

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Hi, so just to understand what you have done...? You've completely removed the locking screws, and replaced them with three more springs? But you need something to "screw down" onto and through the spring right to hold it in place? Isn't that what the locking screws do anyway? I am sure you know what you are doing - I am just eager to understand because I'd like to do something similar.

I second that thought about the locking screws screwing up the collimation. Absolutely. I though it was just me being ham-fisted.

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Due to the mirror cell now being shifted up the tube by 15mm (this is so I can get more back focus distance for AP) the 'mirror locking' no longer even reach the mirror cell (only about half way). So I just using the shank of the screw to hold the extra springs in place.

You could do this mod with extra normal length springs- but then it would be wise to fit shorter screws in place of the existing 'mirror locking' screws so they do not toch the mirror cell and mess up collimation.

I'm glad to find I'm not alone I coming to the same conclusion about the 'mirror locking' screws!

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