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BOBS VERY EXPENSIVE KNOBS


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Just looked at changing my secondary mirror adjusters on my 130pDS.

£21 plus delivery of course. 

Not titanium or gold but stainless Steel. 

I used to sell surgical instruments and we bought in from our factory stainless  steel scissors with special inserts in the cutting edge to prolong surgical sharpness. 

I could buy one pair of scissors for the price of 1 Bob's knob screw. Now even allowing for the lapsed 15 years and taking into account that surgical CE marked instruments demand a mark up it feels like Bob is taking the Michael for 1 screw for 7£.

Not even a 10% discount for pensioners who probably spend less than £7 a day on food. 

 

 

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20 minutes ago, johninderby said:

I like the black stainless knobs as find on eBay. Those are the ones that I fitted to the Bresser OTA.

F6C861DC-1A62-4E0B-A927-3261A6A80209.jpeg

Hi John. 

They work very well. How much do they cost and how do you ensure that they are suitable. 

PS

After the rebuild the Bresser is in great condition

 

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I bought a selection of knurled screws some have plastic heads and some metal heads and they do the job perfectly for a fraction of the cost. If I can remember correctly the primary screws were M4 and the secondary M3. If you buy 20/25 mm long they can be cut to size.

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Search for "knurled knob thumb cap head screws stainless steel" or similar and you should get lots of alternative hits.  As @banjaxed says above, most astro screws are M3/M4 and even M5 occasionally.  Just check the width of the knob/cap to ensure they won't interfere with each other.

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Can’t find that seller of cheap ones on eBay anymore. There are some but at 9 quid each might as well get te BobsKnobs.

Black plastic ones are pretty common though. Just remove one of the screws and  check the length and thread size.

 

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2 minutes ago, Astro_Dad said:

I have a new C6 - in practice how often am I likely to need to collimate and are Bobs knobs likely to provide a genuinely useful way of doing this? Interested to hear views. 

I think there are two schools of thought that I know of…

Using Bob’s knobs type thumb wheels, you can collimate easily and often if needed and probably don’t tighten them up very hard so it is more likely to shift.

Using Allen or cross headed bolts, you can tighten them down a lot harder for more solidly held collimation but it’s a little less convenient to adjust if it does go out.

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i dont think there is anything special in the manufacture of bobs knobs, standard metric thread,  if i wanted knurled screws i would definately use ebay.  have done may times before especially for s/s nuts bolts screws washers etc mainly  for marine use. never any problems. and saved a lot of money over the years.

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9 hours ago, Spile said:

I cannot see the point. My secondary rarely goes out of alignment and it is no bother to use an Allen key to tweak if necessary.

I agree, my secondary hardly goes out of alignment on my newtonians, however I can see the point of them on the primary mirror side as that is the side you would need to collimate more often if you don't have collimation knobs.

I think Bob's Knobs are a good product, I believe they were initially made for schmidt owners instead of using Allen keys for collimation, a much better solution, the last thing you want is to scratch your corrector plate in the dark with an Allen key.😪

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8 hours ago, Astro_Dad said:

I have a new C6 - in practice how often am I likely to need to collimate and are Bobs knobs likely to provide a genuinely useful way of doing this? Interested to hear views. 

With Bob's knobs you're more likely to collimate more often

With a normal hexbolt or screw they're tightened down more so unless you bang your scope around it's far more unlikely to lose collimation 

If you're in the clumsy camp then a Allen wrench or a screwdriver could be a problem on a corrector , if you're normal then there's no problem

 

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9 hours ago, Astro_Dad said:

Could you recommend / specify the exact screws you used here please?

 

Below is a link for Bob's knobs at FLO. These are for the Celestron C6.There you have the option to choose black or stainless steel.

https://www.firstlightoptics.com/bobs-knobs-collimation/bobs-knobs-celestron-c6-collimation-knobs.html

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