Bob's Knobs?

[JayStar]

I'm paranoid so I have mine at roughly 45° and alternate it every so often

Is that with the clutches locked?

I can get a good balance without the clutches locked if i take everything off the OTA or leave everything on, but i like to take all the visual and imaging train components off when not in use, but tend to leave the finder scope on.

I have heard that leaving teh clutches engaged can also be bad for the scope because it can damage the clutch...

[knobby]

I leave them on , but loose

[RafalT73]

My first impression with collimation using Bob's Knobs - mega hit, SUPER. Collimation of telescope goes unbelievable fast and no stress.

Yesterday I collected a lot of material from Moon imaging, but I have no time to process it. Just as a sample I stack one avi. Crater Clavius (width 255 km, depth 3,5 km)

[Tinker1947]

I brought these from A2A4.com they cost about a fiver from memory, i chose the longer length then packed them out with stainless steel washers, the knobs are stainless as well....

[Avocette]

i thought about replacing the rubber o rings with springs but not sure if it can be done on a 200p skywatcher ?

Simple answer yes - I did it. However I started off just ordering the standard knob set for the 200p and found that it didn't fit properly, and it didn't work well because SW had started using the neoprene O rings, whereas earlier examples had springs. So I got into correspondence with Bob and sent him lots of photos with dimensional references. As a result he came up with different length screws and some test example springs all of which sorted out my scope. The only lasting problem was that I could not stand my OTA on its mirror end, since the BKs protruded beyond the tube end casting. This became, literally a pain in the back, since it made less convenient to split the Dob into two parts for carrying.

Since then I upgraded via a 250px to a 300p, both of which have had SW Knobs and springs and deeply recessed tube end castings.

[RafalT73]

Hi all, today I have just received bob's knobs. It is really fantastic thing and fulfill to my expectation. However, after installing it turns out that I can not put dust cap onto my telescope. Knobs are little bit bigger than space between secondary mirror housing and edge of telescope assembly tube - screws protrude beyond the edge. Have you met with such situation?  Have you got some hints?

My telescope is Celestron 11" compatible with fastar system.

Hi I solved the problem. Using a hole saw for wood I cut a central hole in the dust cap (fi 83mm).

On the edge of the hole I glued a rubber gasket. The gasket provide a sufficient distance for Bob's Knobs.

And finally at the top of rubber gasket I glued plastic cover. I works!!! Dust cap can be again mounted on telescope.

 

[Tinker1947]

The Bob's knobs only need to long enough to touch the back of the secondary the one's in my picture were fine the dust cover fitted no problem.....if you can't put the cover on then shorten them a bit.....

[RafalT73]

The Bob's knobs only need to long enough to touch the back of the secondary the one's in my picture were fine the dust cover fitted no problem.....if you can't put the cover on then shorten them a bit.....

Celestron dust cover is concave and distance between edge of secondary mirror housing and dust cap is really minimum. No chance to place there any other screw then original one. But as I said - problem solved  

[Tinker1947]

Celestron dust cover is concave and distance between edge of secondary mirror housing and dust cap is really minimum. No chance to place there any other screw then original one. But as I said - problem solved

Look at my photo that was my C11 the dust cover went on with a twist to lock it.....

[JayStar]

Mine arrived and I have attached them - my scope is a CPC925 and had the colllimation screw cover that twists to reveal the screws.  Main OTA cap goes on fine with the new knobs installed.

Unfortunately I mistook the main secondary mirror housing thread as a way to reveal the screws and actually ended up removing the secondary!  Suffice to say that I had my first SCT collimating job to do after replacing the mirror and adding Bob's Knobs.  Luckily with these new adjusters in place I was able to re-collimate to an acceptable level... will be doing some tweaking to make it perfect.  It seems like this will be another one of things to obsess about getting perfect ... With that in mind does anyone have any experience with CCDInspector which has a collimation tool that uses a CCD image as opposed to having to look into the eyepiece at an unfocused star.

[RafalT73]

It looks that everybody are happy with Bob's Knobs

If so then why Celestron does not install it originally in SCT ota?

[Tinker1947]

Give them time the new scope have Feathertouch micro Focusers as standard.......

http://www.firstlightoptics.com/rowe-ackermann-schmidt-astrograph-telescopes/celestron-rowe-ackermann-schmidt-astrograph-telescope.html

[thehand]

"Give them time the new scope have Feathertouch micro Focusers as standard......."

Thanks.  I took a look at the ad but no model number was listed for the focuser.  So the question is, is it an OEM focuser with the feather touch name?  If anyone is familiar how big-box stores such as Lowes and Home Depot sell seemingly name brand tools, then it may or may not be a similar thing.  For example: if I buy a Milwaukee drill at Lowes, it's not the same MIlwaukee drill I can buy from tool vendors.  It may look the same, have a similar model number, but it's not quite the same quality because the OEM relationship drives for a lower cost item and thus Milwaukee will cheapen the drill for their bigbox customer who is signing up to some sort of guaranteed purchasing agreement.

[Tinker1947]

well if you want quality go to the tool vendor, i don't think we have the same sort of problem in the UK, well i have never heard of 2 types of the same drill ect....

[thehand]

"well i have never heard of 2 types of the same drill ect...."

It's most apparent when  you compare the seemingly the same model number between two bigbox stores.  The full model number on the label will have one or two different characters.  Sometimes it's as explicit as "L" for "Lowes" and "H" for "Home Depot".

I don't know what you have for bigbox stores in the UK but next time you look at a product at the bigbox store copy down the model number in full.  Then go to your local hardware store that sells the seemingly same item but for more money.  The part numbers will likely be slightly different.

[Mr Spock]

Bob's Knobs on my C9.25 was one of the best upgrades. It makes collimation so much easier.

As installing Bob's Knobs would change collimation anyway, I took my secondary out to fit them. It would be so easy to take the original screws out and have the secondary mirror come off the mounting. It was a risk I wasn't willing to make.