36 replies to this topic

[CTYankee]

I have a C11 Edge telescope and need to have good collimation for planetary imaging. Do you recommend Bob's Knobs in place of the standard phillips screws? If you can comment on your experience with them (either good or bad) I'd appreciate it. In particular I am wondering if the scope would hold collimation well after installing them. 

[pyrasanth]

Don't waste your money- they are, IMO, a fad that you don't need.

 

I bought a set- bad to use- I put them back in the packet & never touched them again.

 

The stock Celestron screws are fine.

Edited by pyrasanth, 24 April 2025 - 05:20 PM.

[Notdarkenough]

No. They don't hold collimation as well as screws IME. I dumped mine after a few months. I replaced them with hex cap screws. The Phillips head screws are soft and deform too easily, but the hex cap screws have been wonderful. They hold well, don't deform easily, and provide a much more stable connection with the tool in the dark. My other problem with Bob's Knobs is my arthritis in my thumbs. I also know some folks who have replaced collimation screws with wing-style-head screws.

[MikeCrapo]

I agree with those above. They are hard to turn, and I like the hex screws a lot more. Easier to fine tune.

[Don W]

I replaced the stock screws with Allen heads. I can leave a wrench or two in the heads and it helps me figure out which one to move.

[vtaDan]

I have them on my C8 and prefer them to using the original Phillips screws but they are overpriced. You can find the exact same thing at a decent hardware store or online for a quarter of the price. 

[Jethro7]

Hello CTYankee,

Bobs knobs are one of those things that are either loved or hated I fall into the former camp. Besides insulating my C8 EHD with Reflectix, installing a set of Bob's Knobs  one of the best upgrades that I have done for the C8. Bob's Knobs, make collimation very fast and easy. You can watch as you collimate. If the Bob's Knobs are tighten down correctly, collimation is something that you will rarely have to do. When I do have to collimate the C8, it usually only takes a tiny tweek of one screw. A few other side notes. The factory screws are soft and easilly stripped. Personally I don't like having pointy metal objects around the corrector plate especially at night. Bob's Knobs were the answer.

 

HAPPY SKIES AND KEEP LOOKING UP Jethro.

Edited by Jethro7, 25 April 2025 - 08:43 AM.

[OregonAstronomer]

+1 for Jethro7!

I have Bob's Knobs on my C8, C9.25 EdgeHD and C14 EdgeHD. Best investment I ever made. They never drop into the grass, dirt, or through the gaps in the deck boards like hex wrenches always seem to do. I don't have to try to find little hex screw depressions in the dark, nor worry about dropping a hex wrench from my arthritic fingers onto the corrector plate. My scopes also hold collimation better than they ever did in the past. I check very carefully before each imaging session, and I rarely have to re-collimate anymore. With the stock screws, I had to re-collimate every time I traveled with the scopes.

[Inkie]

You can get reasonable substitutes on line for about half the price if you bother to spend a few minutes on one of the market sites.

[MrJones]

Plenty of threads on this. I love them more than I hate them. Ultimately who wants deal with Allen wrenches or screwdrivers in the dark so close to the corrector? I also think you get a better feel for the tightness with your fingers right on the screws. I put wingnuts on my Dob but Bob’s are always the right length and fit and are very easy to install.

[Don W]

I can’t remember the last time I collimated any telescope in the dark!

[Patrick]

I put some Bob's Knobs on my C11 at one point in time, but then found the scope cover hit the screws so they came back off again. 

 

Patrick

[quilty]

I have a C11 Edge telescope and need to have good collimation for planetary imaging. Do you recommend Bob's Knobs in place of the standard phillips screws? If you can comment on your experience with them (either good or bad) I'd appreciate it. In particular I am wondering if the scope would hold collimation well after installing them.

No,
but these Knobs are quite a personal opinion thing. You could try them. I'm fine with Phillips heads. Anyway better than 2 mm Allen hex heads on my C11

[carolinaskies]

I have a C11 Edge telescope and need to have good collimation for planetary imaging. Do you recommend Bob's Knobs in place of the standard phillips screws? If you can comment on your experience with them (either good or bad) I'd appreciate it. In particular I am wondering if the scope would hold collimation well after installing them. 

I prefer the allen head screws used in Meade secondaries.  You can remove one of your screws and if you have a decent hardware store it's not hard to match them up to a set of allen head version.  If you have to order them online McMaster's online catalog has quality offerings, you only need to ID the length, thread type and thread pitch.

 

SCTs shouldn't require constant adjustment AND when it is warranted you want to be able to have fine control.  Thumbscrew types like BKs give little feedback for movement compared to adjusting either a screwdriver or allen wrench.  Allen wrenches(good ones) have the advantage of sticking in the socket of the screw and showing up as a shadown in the field of view helping to know what the adjustment is doing to the centering.  

[JimB1]

I put BKs on the secondary for my Meade SN6 and feel it was a good investment. Makes collimation on that scope much easier and I like tool free adjustments if I need to tweak something quickly. That scope has a very heavy secondary mirror housing, and I move everything in and out of the house for every session so needing the occasional adjustment is part of life. 

 

I just got a set for the secondary on my 6se and the jury is still out on that one since I just put them on a day ago. I know I didn't like the Philips heads that were on there. Going near the corrector with a pointy object in the dark just seems like a bad idea. I'll know in a few weeks if the BKs hold collimation. So far, they seem good. 

 

JMHO

[MrJones]

I put some Bob's Knobs on my C11 at one point in time, but then found the scope cover hit the screws so they came back off again. 

 

Patrick

That's curious. I had them on my C11 and it was fine. You really need to check models and such with a few scopes to get the right ones, looks like there are 4 options for C11s. They (him?) were also very helpful the couple times I've emailed with questions. I've had them on a C9.25, C11 and current C8 and been satisfied. I did not keep them on my 6" Meade ACF but I can't remember why.

[VA3DSO]

I'll echo the experiences mentioned above and vote against the Bob's Knobs:

• I installed Bob's Knobs on my 8" SCT
• I found I could no longer put the cover plate on the end of the telescope - BK's advice was to "bend" my cover plate to accommodate
• I found the knobs hard to fine tune (not enough leverage / fine adjustment)
• the arthritis in my hands made it hard to get the BK's tightened down to my satisfaction
• I removed the Bob's Knobs and put my original Allen head screws back in place

Ultimately, the Allen head screws were the clear winner for me - extra leverage for fine tweaking, my Allen key "sticks" in the Allen head making it very easy to use at night, my cover plate fits per normal, my scope retains its collimation very well (I tweak it on Polaris every time I'm out - seeing permitted).

[Inkie]

As with all purchases of this kind, improving one's experience and handling of a scope, you have to 'size' the item if you're looking further afield than the often pricey (comparatively) hobby retailers.  For the knobs impeding the installation of the front cover of the OTA, a shorter length of the same screw pitch would work, even if you have to cut them to size (hacksaw and then dress the threads and end with needle files).

[MrJones]

[*]I found the knobs hard to fine tune (not enough leverage / fine adjustment)
.

Definitely an issue. I do try to loosen screws before I tighten others but I have had to use pliers maybe twice to unstick overly tight ones.

[KOstar]

Okay, here is my experience.  I have a C11 Edge and it came from the factory with Phillips head collimation screws.  I hate this setup.  In order to adjust them you have to press down on the collimation screw slightly (not a lot, but some) to keep the screwdriver engaged.  I don't like the idea of pressing down on the screw, and thereby the corrector plate, to adjust them.  And if you slip off of a screw, you have a pointy Phillips screwdriver near your corrector plate that could do some damage.

 

So, I got some Bob's Knobs for it.  They installed fine and they work well.  But, as has been mentioned, the top of the knob pressed slightly against the scope cover when it was twisted into place.  This puts stress on the corrector plate.  And since the knobs are in contact with the cover, if you bump the cover, you are also bumping the corrector plate.  Not a good thing!

 

I believe your best bet is replacing the Phillips collimation screws with Allen head screws with exactly the same thread length as your factory screws.  They allow you to adjust the collimation screws precisely with only a twisting motion.  No down pressure needed.  In my experience, they hold collimation well.

 

I do have Bob's Knobs on my C8.  They don't hit anything and work well.  But for my C11, not a good fit.

 

Hope this helps.

 

KO

 

Just a reminder - only replace one screw at a time.  If you remove all three at a time, the secondary mirror may fall.

Edited by KOstar, 25 April 2025 - 06:44 PM.

[39.1N84.5W]

Allen head screws are a fine upgrade over the stock screws. M3x12mm for the Edge C11.

[quilty]

Allen head screws are a fine upgrade over the stock screws. M3x12mm for the Edge C11.

NO! not those microscopic 2 mm hexes. Maybe at 3mm an Allen hex starts to properly work

[BKBrown]

I am a planetary imager and am very fussy about proper collimation. That said, I use Bob's Knobs on every one of my SCTs (EdgeHD 14, two EdgeHD 11s, an EdgeHD 8, and my former C9.25 XLT). Like others here, I have arthritic fingers and do not want to manipulate a small hex wrench, let alone a Phillips head screwdriver, anywhere near a corrector plate in the dark. In my experience I have never had problems getting them tight enough or having them too loose. Checking collimation before every imaging session is part of my routine, and it is always with a star test. If the seeing is too bad for a test, it is too bad for imaging that night. I do not personally know any first rate planetary imager who does not frequently check collimation, it is a critical step for acquiring high quality data. And yet I only infrequently need to actually tweak collimation. So employing Bob's Knobs is like any new tool or task..."use makes master" as folks used to say. Install and use with confidence.

 

Clear Skies,

Brian 

Edited by BKBrown, 28 April 2025 - 10:28 PM.

[quilty]

As said above as long as thumb screws do and the aperture lid still fits there's nothing wrong with them.

I'm just arguing against those microscopic Allen hexes where Phillips do much better. Already told this in another thread, the great pro of proper Phillips is they do without any play or clearance so they provide a better feeling at tiny tweaks (as thumb screws may do, too)
due to their double wedge shape (blue and orange):



It's not about applying a high torque (at which tiny Allen regularly fail) it's about the elimination of any play in order to better feel what you're doing

Edited by quilty, 28 April 2025 - 05:54 AM.

[39.1N84.5W]

NO! not those microscopic 2 mm hexes. Maybe at 3mm an Allen hex starts to properly work

NO? Thats the thread size listed by the manufacturer for C11 Edge. M3x12mm. Please do not post misinformation.