Quote:
Originally Posted by 5ash
Here’s a picture of the above thumb screws, total cost including postage was $5 for 5 screws.
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That's the easiest and cheapest way to do it and you end up with the same result if not better. Bob's knobs are ridiculously expensive for what they are.
I replaced my secondary collimation screws on my 10" GSO dob with 304 grade stainless thumb screws about 15 years ago. I can't remember what length they were, but I remember they needed to be quite long to go right through the secondary holder and have enough length remaining to leave full adjustment of the secondary. They are definitely 4mm x .7mm pitch and I think they needed to be either 40mm or 50mm long. Measure the depth of the secondary holder and add about 15mm to give sufficient travel both sides of the holder. I also replaced the primary collimation screws on the GSO mirror cell with stronger stainless steel springs and 7mm metric thumb screws. I think they use a different primary collimation set up on the more recent manufacture scopes.
Cheers
John B