Bob's knobs for SW dobson 200 F6

[Piero]

I am seriously considering these for the primary and secondary mirrors in my dobson. I can see that Rother Valley Optics sells them, but they are quite expensive: 

http://www.rothervalleyoptics.co.uk/bobs-knobs-skywatcher-newtonian-primary-collimating-thumbscrews.html

http://www.rothervalleyoptics.co.uk/bobs-knobs-skywatcher-newtonian-secondary-collimating-thumbscrews.html

Do members buy the original ones generally or an equivalent (and much cheaper) version like this: http://www.boneham.co.uk/shop/product/knurled_thumb_screws_din_464? Any experience? 

Also, the two links above are for a generic SW newton 200. Are these the same for the SW dobson version?

Thanks, Piero

[brantuk]

I had some home made ones in my 12" dob from a mate in my astro soc, and I also has some from Bob himself in the US of A for my 16" dob. I also have some others in my 200P.

To be honest you may as well get the RVO ones cos they all do the same job but for varying prices. And it's hard to be a better screw than any other screw really cos there's not many ways to improve on the function of being a screw. Make sure you get the right size.

[Gazabone]

I've just upgraded my 250p to a 300p Goto. I had the secondary bobs knobs on the 250 already and actually ordered a set for the 300 before I even ordered the scope I like them so much. Personally I don't see any advantage in changing the original primary mirror ones (big but here - if I remember correctly, the primary knobs on the 200 are different to the 250 and 300 and perhaps not as easy to use, if that's the case, I'd say go for it) but upgrading the secondary is a seriously good idea and although expensive for what they are, worth every penny. 

[Piero]

Sure, I don't mind to spend some pound more as long as it is worth. Unfortunately RVO cannot confirm whether those in the links above fit the SW skyliner 200 F6..

Does anyone know whether the lock+collimation screws are the same between the SW newton 200 (F5, I presume) and the skyliner dobson version?

http://www.bobsknobs.com/Newt/page66/SWdob.html

Thanks a lot,

Piero 

[brantuk]

Oh - sorry - I was referring only to the secondary ones.

For the primary ones (which I missed out) - changing them depends on the existing ones. Older scopes had sloppy springs and hex head screws - well worth the change for stiffer springs and knobs. More recent scopes you need to evaluate if it's necessary to change - they tend to come through nowadays with decent springs - and sometimes but not always knobs.....

[brantuk]

One of the reasons I went to Bob's Knobs for the Lightbridge is because they will confirm which size fits which scope, cos their knobs and screws are specifically made for a particular scope.

[Piero]

Thanks Brantuk, 

The springs on the primary look quite thick and to me they hold collimation quite well, I would say. Currently, there is no Bob's knobs, but just normal hex screws for locking and normal screw for collimating with a screwdriver.  

[rockystar]

the ones from RVO are the ones I have in my 200 Skyliner. I was a little bit cringy at the thought of paying £25 for six screws too, but I bit the bullet, and got both primary and secondary and don't regret it.

[Piero]

1 minute ago, rockystar said:

the ones from RVO are the ones I have in my 200 Skyliner. I was a little bit cringy at the thought of paying £25 for six screws too, but I bit the bullet, and got both primary and secondary and don't regret it.

Thanks mate! If they works on yours, they'll work on mine! Looking forward to mounting them next time I fly back to Italy!

[laudropb]

Nice post Piero. I was thinking of changing mine and you have got all the answers I was looking for. Thanks

[CraigT82]

I fitted these thumbscrews to my 200p skyliner...  http://www.ebay.co.uk/itm/10-M5-X-25-FINE-KNURL-THUMBSCREW-KNOBS-WHITE-/222121956475?hash=item33b780147b

 

With these springs, which were very strong but a bit long so I cut in half...  http://www.ebay.co.uk/itm/Compression-spring-2mm-x-13-7mm-x-50mm-2-pack-/111808517124?hash=item1a084e9404

I just got rid of the locking screws, the springs are strong enough not to need them.

[Charic]

I've  often considered the need for Bob's Knobs, yet cant accept that they are more secure and offer a  better/stable hold to the mirror cell, in comparison to the bog standard adjustments using the default fitted 'O' rings, or are they just simply  intended  as an aid for fast tool less adjustments.
I handle my scope with a lot of care, this  scope needs little, if  any correction  once setup, the Barlowed laser technique always looks perfect.
During collimation itself, there is in fact, very little adjustment required, and the 'O' rings  are pretty firm and don't  really 'give'   if you know what I'm trying to say! so once adjusted, they "Should" remain in place, but not the case, as you still need to collimate when required?
That said, sure it will be easier to collimate without tools, if you can reach the end of a Skyliner with your eye on the focuser, but is it not the case, that if held under spring tension, there is  the potential for more movement, more adjustments?
Like most things, I would need to try for my self, what what are the thoughts from those converted, have you found that you need to collimate more often?

[Piero]

2 hours ago, Charic said:

I've  often considered the need for Bob's Knobs, yet cant accept that they are more secure and offer a  better/stable hold to the mirror cell, in comparison to the bog standard adjustments using the default fitted 'O' rings, or are they just simply  intended  as an aid for fast tool less adjustments.
I handle my scope with a lot of care, this  scope needs little, if  any correction  once setup, the Barlowed laser technique always looks perfect.
During collimation itself, there is in fact, very little adjustment required, and the 'O' rings  are pretty firm and don't  really 'give'   if you know what I'm trying to say! so once adjusted, they "Should" remain in place, but not the case, as you still need to collimate when required?
That said, sure it will be easier to collimate without tools, if you can reach the end of a Skyliner with your eye on the focuser, but is it not the case, that if held under spring tension, there is  the potential for more movement, more adjustments?
Like most things, I would need to try for my self, what what are the thoughts from those converted, have you found that you need to collimate more often?

Hi Charic,  

Unfortunately, I cannot tell you whether they hold collimation better than the standard set of screws because I replaced the latter immediately. I suspect that the thickness of the springs play a more important role in holding the collimation though. The reason why I chose to replace the standard screws with bob's knobs was entirely due to comfort. I didn't like to fiddle with tools while collimating the telescope at all.  

I don't need to collimate the telescope often, although please consider that I don't use my 8" often because it is in Italy. Personally I am satisfied with this purchase and I would do it again. If you are fine with normal screws and don't feel the need to collimate your telescope, possibly you don't need them.  

Piero

[Ben the Ignorant]

I never accepted Bob's Knobs prices, which made me craft them instead of buying them. For the secondary, 4mm screws and serrated washers held by a nut and a counternut locked in place with superglue. They were sharpie-painted black later.

 

For the primary on this 150/750: 5mm stainless threaded rods cut to size, with serrated plastic knobs stuck between nuts secured by superglue. Springs push against the knobs in order to do away with the lock screws.

[cotterless45]

Nice, the stock primary springs on my 10" were woefully inadequate. Bob's springs fitted and it just keeps collimation. About time they stopped putting Allen bolts on the primaries and butter mount bolts. For a few dollars more manufacturers could have a user friendly scope. I fitted rubber door stops where the Dob locking bolts were, now it stands up , no problem,

Nick.

[wookie1965]

On 24/05/2016 at 11:02, Piero said:

I am seriously considering these for the primary and secondary mirrors in my dobson. I can see that Rother Valley Optics sells them, but they are quite expensive: 

http://www.rothervalleyoptics.co.uk/bobs-knobs-skywatcher-newtonian-primary-collimating-thumbscrews.html

http://www.rothervalleyoptics.co.uk/bobs-knobs-skywatcher-newtonian-secondary-collimating-thumbscrews.html

Do members buy the original ones generally or an equivalent (and much cheaper) version like this: http://www.boneham.co.uk/shop/product/knurled_thumb_screws_din_464? Any experience? 

Also, the two links above are for a generic SW newton 200. Are these the same for the SW dobson version?

Thanks, Piero

I had to buy 10 for my secondary mirror (200p) so I have a few spare not sure if they fit the Primary you are welcome to them.

[Piero]

14 minutes ago, wookie1965 said:

I had to buy 10 for my secondary mirror (200p) so I have a few spare not sure if they fit the Primary you are welcome to them.

Thanks Wookie'65, very kind of you!  

I already bought mine last spring and they work very well. As mentioned before, I also think they are over expensive. On the other hand, they make the essential step of collimation much easier.

[wookie1965]

2 hours ago, Piero said:

Thanks Wookie'65, very kind of you!  

I already bought mine last spring and they work very well. As mentioned before, I also think they are over expensive. On the other hand, they make the essential step of collimation much easier.

I only paid £4 for the 10 I was same as you looking around and found they were expensive.

[-Dougal-]

On 21/09/2016 at 07:21, Ben the Ignorant said:

I never accepted Bob's Knobs prices, which made me craft them instead of buying them. For the secondary, 4mm screws and serrated washers held by a nut and a counternut locked in place with superglue. They were sharpie-painted black later.

 

Thanks for the idea these look a lot safer than fiddling around with a allen key even if secondry adjustments don't normallly require much attention once set up

 

[gls]

On 24/05/2016 at 11:34, brantuk said:

One of the reasons I went to Bob's Knobs for the Lightbridge is because they will confirm which size fits which scope, cos their knobs and screws are specifically made for a particular scope.

Specifically made for each scope? More like he buys boxes of thumbscrews, looks what ones fit which scope and increases the price by 1000%