Bob's Knobs

[Stu Ward]

After my last few days playing around getting the hang of Collimation, i see the potential benefit of Bob's Knobs

But looking at their website, i can find the Secondary knobs for my Skywatcher Dob, but i can't see where the Primary ones are

I've fired off an email to them, but they have not replied

Anyone know if the Meade 8" Lightbridge set will work ?
Its not clear that the Primary's are compatible

Thanks

Stu

[ericc]

Hi Stu--
I cant tell you if the Bobs Knobs will fit your Sky Watcher Dob,but rest assured that by fitting Bobs Knobs to the secondary and primary will make your life alot easier--its money well spent!
I have just fitted a set to my Bintel(GSO)secondary and they are bloody fantastic.The primary has large knurled knobs as standard(abit like Bobs Knobs).
I also found that fitting heavy duty primary springs work well for me.
Im sure someone else will chime in with the right info.
Good luck!!
Cheers-Eric

[barx1963]

I had a similar query and received an answer from Bob himself, took a couple of days.
You will love Bobs knobs, bought an entire set, primary, secondary and springs, worth every cent!

[Kevnool]

Search the posts for bobs knobs as there is info here.
Cheers Kev.

[Stu Ward]

Looks as though i am not going to be able to add knobs to the primary
Bob has got back to me and confirmed that the knobs won't work on my Skywatcher as the Locking nuts are too close to the adjustment screws

Spose i could still use Secondary knobs

[Kevnool]

On my scope the locking screws are not in there because there useless.
The locking nuts will give you grief and destroy the collimation.
If you have really tight compression springs (thats a mod) the mirror dont move.

Replace your springs / throw the locking nuts or screws away/ bobs Knobs.
Thats my opinion.

Cheers Kev.

[John45]

Very much agree. For the money we spend on other items in this hobby, this is a fairly low cost option that makes things quicker and easier. Even if you only manage to get one set that will fit.

[bmitchell82]

Loose the lock screws they are snot, like Kev says as soon as you lock them in, you loose your collimation. bobs knobs will be something youll love! :) good luck

[big_dav_2001]

Funnily enough i was just about to post about my addition of bobs knobs to my 12" Dob today... I also got the whole works; primary, secondary, springs, and telrad knobs...

I was surprised how flimsy the standard GSO springs are in comparison to Bob's...It always held its collimation pretty well before upgrading, but with these new springs, its not going to take one hell of a hit to bump it out of collimation again....

I also agree with Kev and Brendan, the thicker/stronger springs make the locking screws unnecessesary...

They definately make collimating sooo much quicker and easier...

Davin
:cheers:

[yusufcam]

yes, had the same problem with the lock screws.

the trick was, i found, to just loosen them the smallest amount to accomplish the collimation. then when they were retightened they didn't move the mirror.

bit of a pain, but it appears since using this approach to be locked in and hasn't lost collimation since.

regards
Colin

[Jason D]

The lock screws are not really a problem. Just handle them the same way you would handle the adjustment screws. That is, tighten them slowly while keeping an eye on your favorite collimation tool.
For example, if you use a barlowed laser collimator with a rear window such as the TuBlug or the BLUG then keep your eye on the center spot shadow while tightening the lock screws to preserve collimation.
Jason

[Ingle]

Apologies if this is a hijack but where is the best place to purchase Bob's Knobs? Is there an Aussie retailer or do you just go direct to Bob?

I have a Bintel 10" Dob (about 2005 model) that I would be interested in getting knobs and springs for. I believe is a Guan Sheng scope, will they know what I am talking about if I go somewhere other than Bintel?

Cheers

Alex

[Steffen]

That's easy! Bob ships for free worldwide, why go elsewhere?

Cheers
Steffen.

[bmitchell82]

Or even better jason :D get rid of the old skywatcher primary cell and put something in that works :) i just recived my new orion optics 10" mirror cell! happy days!

[Stu Ward]

So i've been out and bought myself a new set of knobs and springs (well getting them shipped direct from Bob)

Does anyone know if Instructions come with the springs, or where i can find out how to replace them safely ?

I have this recurring thought that i'm going to undo something and springs are going to fly out, the mirror crash to the ground and leave me sobbing in a heap on the floor !!!!!!

Stu

[Steffen]

Yes, that's what is most likely to happen. On the way to the floor the mirror will also travel down the tube and shatter the secondary… :lol:

Seriously, if you think before you do and take your time it's going to be a breeze. Here's how I do it:


mark the position of the mirror cell's mounting frame in the tube
unscrew the frame from the bottom of the tube (get help if you're not confident you can support its weight with one hand once it pops out)
put the frame and cell mirror down on a clean table
mark the relative position of frame and cell
remove the locking screws, put them away
remove the collimation screws, take the mountig frame off the mirror cell (take care not to rip off the fan cable if there is one)
remove the old springs that should now be sitting on top of the mirror cell, put the new ones in their places
replace the mounting frame and insert the collimation screws, compressing the springs down to about 1/2 to 1/3 of their length.
(optional) turn the cell over and verify the position of the centre mark
put the cell back into the tube and replace the screws.


Cheers
Steffen.

[JethroB76]

Or you could unscrew and replace one collimation screw/spring at a time.
This should be relatively easy unless you have a closed mirror cell

[Stu Ward]

My set of Knobs arrived this morning, so i couldn't wait to install them when i got home. However i found a real problem

Now i'm not sure if Sywatcher have changed their design, or i have suffered from some misinformation from here

I purchased a full set :
Primary knobs
Uprated Springs
Secondary Knobs

I detached the mirror housing from my dob and then removed the mirror ( V V V carefully )
Then took the Primary adjusting screws from the base so that i could replace the weak springs, but wait a minute, there are no springs !!!!

My dob's primary springs are infact little rubber washers, but no drama i will just replace them with the springs

Next problem

The Primary adjusters' thread supplied by Bob are about 2mm wider than the screws they are supposed to replace !!!
So the Primary adjusters will not go in the base.
And as the factory screws are much shorter the springs are useless !!!

The Secondary Knobs seem fine

So i have paid around $90 for a set of Secondary adjusters.
I have informed Bob via email that there may have been a Skywatcher design change that he is unaware of.

I feel sad

Stu

[morls]

Sorry to hear of your problems Stu. I'm looking at doing the same sort of mod on my 8" skywatcher collapsible dob. Maybe we're just stuck with the original primary screws?

Stephen

[Steffen]

I couldn't find any primary knobs for SkyWatcher dobs on Bob's site. Which ones did you get?

Cheers
Steffen.

[Stu Ward]

The Meade Lightbridge ones, as these fit all Skywatcher Dobs (except for the 8") as i have now found out

Stu

[bartman]

I had a look on Bobs site a while ago......is there a set that will fit a 10" skywatcher Newt. Primary and secondary and eq6 mount....

[morls]

Hi Stu,

have you gotten any further with finding screws to fit the primary?

I was wondering if there would be a way around....maybe get larger screws i.e. longer shanks but with the same thread and the same length of thread as the original ones.

Then we'd need a way to anchor the body of the screw to the base of the mirror cell on the outside so that when you tighten the screw it pulls the mirror towards the base....

maybe even a screw with a lot of thread and some sort of locking nut to anchor it...

do you know how Bob's Knobs do it?

I might be way off track here, but just trying to find a way to get this to work:shrug:....it just seems too awkward at the moment with the stock screws, and a bit of a bummer that Bob's Knobs don't fit....

cheers

Stephen

[Stu Ward]

I have found no primary solution just yet.
I am still looking though
I could open Stu's Skywatcher Screws

[bmitchell82]

so let me get this straight stu, you want to have a set of thumb screws virtually to adjust your primary mirror. if so is it this kinda thing you are looking for

http://www.iceinspace.com.au/forum/showthread.php?p=611079#post611079

zip down to post #16

if so shoot me a PM.

[morls]

Hi Brendan,

I'm looking for exactly that for my 8" skywatcher as well, so any advice would be much appreciated....

Hope it's not bad form to jump in here Stu, don't want to hijack your thread....just want to get these damn screws sorted out...

Stephen

[Stu Ward]

I have the Screws for the Secondary care of Bob's Knobs, as his work fine
But the Primary Knobs, the thread is too wide

Stu

[bmitchell82]

Im currently looking into the sizes ect ect, ill get back to you once i have the correct thread sizes ect ect

[morls]

Hi Stu,

Don't know the latest with your situation here, but Brendan was able to sort out a great solution for me.....now have completely tool-free collimation on both primary and secondary for my skywatcher 8" collapsible....

Thanks Brendan....taken the hassle out of collimation....:party:

[Stu Ward]

If Brendan is out there listening, i would love to sort out the right knobs for the primary


Stu

[bmitchell82]

PMed:thumbsup:

[Jeeps]

I am about to order a set of secondary knobs for my skywatcher 10" flex dob. I find the factory primary knobs fine but I'm tired of using an Allen key to adjust my secondary.

Bobs knobs website lists the skywatcher secondary knobs in either 30mm or 35mm. Does anyone know which I should order?

Cheers