help Sky-Watcher dobsonian 200p

[O2B3]

Am looking for help with Collimating my Sky-Watcher dobsonian 200p I can not do this as the screw are missing. Need help in finding where I can get the right ones

20241020_102213.heic

[Astronomist]

It looks like there are allen head grub screws in those holes. I'm pretty sure those are the locking screws so you can just loosen them a bit and ignore them if you want to. The big philips head bolts are the ones you should to be using for collimation.

 

[Chandra]

1 hour ago, Astronomist said:

It looks like there are allen head grub screws in those holes. I'm pretty sure those are the locking screws so you can just loosen them a bit and ignore them if you want to. The big philips head bolts are the ones you should to be using for collimation.

 

I can't see the photo, but if he ignores the locking screws, he can still collimate, but the result won't last really long, which will force him to recolimate frequently (depending on the quality of the cell)... hence the importance of the locking screws: to maintain the mirror position (for longer, at least)...

[O2B3]

am looking for screws that are missing does any know where I can get them am not sure what size and they are called can anyone help me out on this ?

 

[John]

Hello,

There are no screws missing from the back end of your 200p dobsonian. The large cross head screws are the collimation adjustment screws and the hex screws are to lock the primary mirror cell. This post from a couple of years back covers this:

https://stargazerslounge.com/topic/388813-skywatcher-200p-help-and-advice/?do=findComment&comment=4194028

 

Edited October 21 by John

[John]

I've replied to your other post on this - there are no screw missing from the back end of your scope.

 

[Captain Scarlet]

There are nine holes, three with cross-head screws which as John says, are the primary collimation screws. The three larger apparently empty holes are not empty: if you look carefully at your photo you'll see they contain hex-head sunken grubscrews. These are for locking the collimation in place. Many do not bother with these locking screws anyway, they are not necessary if the collimation springs are strong enough. The final set of small holes I think are for a rear disc cover across the whole back end. The cover does more harm than good, it hinders air circulation and will stop the mirror from cooling down in good time. You can safely ignore those holes.

Cheers, Magnus

[Mr Spock]

I've merged your threads as were asking the same question twice 

[Alan64]

I find my own to be indispensable...

https://www.amazon.com/dp/B0CG2WH5ZK?ref=ppx_yo2ov_dt_b_fed_asin_title

There are also some even tinier holes round, an ordered set of three, that escape me.

[O2B3]

Thanks for your help much appreciated 

Mark

[Chandra]

In my opinion, the best thing would be to replace them all with knurled screws, 3 by 3 different ones between both groups. I think that being able to tighten or loosen them without the need for tools would make collimation somewhat easier, that is how most Newts come now...

On the other hand, to know the diameter and the pitch, you just have to extract one of each and probably in a hardware store they will be able to guide you...