Collimation screws

[ckp82]

I bought a used skywatcher 200p dob about a year ago on impulse and it's been gathering dust in the shed ever since as I've been using an e.a.a set up.

Today I cleaned it all up and put it back together only to find that when I come to colimate it there were screws missing on the back of the primary mirror. 

Are the screws missing the same ones that use the springs? Please see attached photo. Where is the best place to get replacements from?

Thanks.

[NGC 1502]

Are you quite certain those screws are missing?  Take a close look because you may find allen head (hexagon) screws in the 3 recesses.  A torch and magnifying glass may help.

[Astronomist]

Those are the collimation locking screws, many people choose not to use them, as tightening them can throw off the collimation. Certainly they are not essential.

If they are missing and you do wish to replace them the best place to get new ones is probably your local hardware store, just measure the hole and buy some appropriate metric thumbscrews, most likely M5 or M6. 

[ckp82]

After a closer inspection, it does look like there is allen key bolts inside. Unfortunately, I don't seem to have the right allen key for it.

I'm used to the flextube 130p which uses thumb screws for both locking screws and collimation screws (see attached image), hence why the 200p looked a bit bare. I usually slack off the locking screws, then do the collimating and tighten up the locking screws.

Can I get the same type of thumb screws for the 200p as the 130p?

 

[NGC 1502]

1 hour ago, ckp82 said:

After a closer inspection, it does look like there is allen key bolts inside. Unfortunately, I don't seem to have the right allen key for it.

I'm used to the flextube 130p which uses thumb screws for both locking screws and collimation screws (see attached image), hence why the 200p looked a bit bare. I usually slack off the locking screws, then do the collimating and tighten up the locking screws.

Can I get the same type of thumb screws for the 200p as the 130p?

 

 

The thread will be a commonly found metric size.  Many DIY stores would stock hex head or Philips head bolts to replace the original recessed Allen screws.  Alternatively if you retain the originals then the Allen key will be an easy to find size.

[Mandy D]

@ckp82 IIRC the grub screws that lock collimation on the 200P are M6 and about 10 mm long. I don't know what end they have, but they can be had with flat end, recessed end, ball end and spike end. I think a 3mm hex key is the correct size.

[RT65CB-SWL]

I mainly buy my metric fasteners from here: https://www.gwr-fasteners.co.uk/ via their eBay outlet/store. If they are imperial or metric, then here: https://www.modelfixings.co.uk/

If I need them asap, then I visit these guys:  https://www.precisefastenings.co.uk/ as I am local to them. Someone also makes homemade jams and preserves for them to sell… hard to resist.

When buying Allen keys from the DIY stores or supermarkets, don’t go for the cheapest ones. I was replacing the bottom case screws on my Panasonic ToughBook CF-19 laptop with some replacement Allen screws and the Allen key snapped… and it was not even tight. When I checked the package of Allen keys,  it said they were made from carbon steel.