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Bob's Knobs for Skywatcher primary?


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If its a Sky-Watcher 200 on an EQ mount Bob doesnt do anything for them. I know cos I photographed the back of my scope and mailed him a few months ago and he said he could'nt help.

Dont know if the 200 Dob has the same back end as the 200 on the EQ.

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My SW 250PX came with adjustable primary knobs from new, dunno if they still come like that?

If I recall correctly the 250's have quite nice "no tool" chrome knobs fitted as standard but for some reason the 200's are fitted with collimation screws that need a phillips screwdriver and locking screws that need an hex key - quite fiddly !.

John

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Thank you all.

Yes, my scope is fitted with wholly inconvenient phillips and hex screw collimation screws. Even more inconvenient as some of the heads are now stripped because of the number of times they've been worked.

AB, that's odd. I would have thought that Bob would have had knobs for one of the most popular scopes out there :? SO what did you do about it?

Andrew

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Hi

Contact WDS Ltd. They'll be able to sort out some knobs for you, maybe complete thumb screws or thumb knobs and threaded rod. You'll just need to know the thread size and length.

http://www.wdsltd.co.uk/Plastic%20handwheels,%20knobs%20&%20grips/

Another alternative is Epsilon Telescopes http://www.epsilon-telescopes.co.uk/products.htm as they could probably make some up for you.

John

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Ummm what I did was to spend ages looking online for nuts and bolts and never found any that would be any good - part of the problem is the lock screws and adjusters are too close together to really have an elegant solution - I gave up in the end.

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Andrew

Get the Lightbridge replacement springs from Bob (I could not find a UK equivalent) and then goto WDS for the primary screws. I'll dig out the ones I ordered if you like...

I also got my secondary replacements from WDS as well.

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Found it!!

The part number from WDS is 8440-504. M5 thread, 15mm shaft length, stainless steel. You need to create an account with WDS but its free to do.

Now, they were a little too long, but I packed them out with nylon washers and they were fine. Since I changed to the replacement Meade springs, I do not need the washers. You may, therefore want to order the 8440-502 at 10mm shaft length.

Incidentally, there are two letters on the end of the code to indicate colour - BG (Black Grey) PG (Pale Grey) TR (Traffic Red) CY (Cadmium Yellow)

I also ordered 8168-227 for the secondary (M4, 25mm length), again, these were too long, but as the secondary screw holes are fully threaded, this is not so much of an issue. More of an aesthetic thing I think.

Hope this helps

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Thanks for that, Daz,

Just to clarify - the primary bolts you refer to are to replace the Philip screws for adjustment, and an allan key is still required to undo the locking nuts?

Has anyone also replaced the locking nuts with thumbscrews, so no tools are needed at all?

Oh, and if the secondary ones are too long, could they get in the way of the tube dust cap?

Cheers

Andrew

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Just to clarify - the primary bolts you refer to are to replace the Philip screws for adjustment, and an allan key is still required to undo the locking nuts?

Has anyone also replaced the locking nuts with thumbscrews, so no tools are needed at all?

Oh, and if the secondary ones are too long, could they get in the way of the tube dust cap?

Anyone? :(

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I've got a set of primary + secondary for my SW dob out in the observatory that I never got round to fitting, once it warms up a bit i'll go check what I ordered :(

General advice would be to just drop Bob an email if there's any doubt what you need, i've ordered from him a bunch of times and he's very helpful

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AP - I had this discussion with Bob at Bobs Knobs and he said no it wasn't possible. I think it would be if you had very thin knurled ends on the lock knobs but I haven't ever been able to source any that are right - thats why I just gave up on the whole idea.

Ultimately - when I am in funds - I will ask around and see if I can get a spare 'back end' for an Orion ( US ) 200 Dob as that has a 9 point cell AND chand collimation knobs. I think the SW200 Dob has the same so assuming the tube diamter is identical it may be possible to acquire a spare and replace the mirror cell / rear end.

That seemed simpler to me than messing about trying to find some wretched screws online.

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Andrew

The replacement springs and the thumb screws that I ordered made the locking screws way too short. At the moment, I don't know if I need to buy longer ones. Hoping that the tension from the springs will be more than enough TBH.

As for the secondary's, no, they do not get in the way of getting the dust cap on.

HTH

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AP - I had this discussion with Bob at Bobs Knobs and he said no it wasn't possible. I think it would be if you had very thin knurled ends on the lock knobs but I haven't ever been able to source any that are right - thats why I just gave up on the whole idea.

You mean because the locking and adjustment knobs are too close together? Oh well :) Of course it wouldn't be that much of a hassle to drill and tap locking knobs a bit away from the adjustment knobs, as it seems to be to find suitable thumbscrews!

The replacement springs and the thumb screws that I ordered made the locking screws way too short. At the moment, I don't know if I need to buy longer ones. Hoping that the tension from the springs will be more than enough TBH.

Interesting. I presume the springs are to help maintain good collimation? Aren't the locking nuts are also very important to do this? And I assume you got the springs for the 8" Lightbridge, which fit the SW?

Thanks for your help all - eventually I'll get there :(

Andrew

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