Bob's knobs worth it??

[Liz]

Have read some good reports on Bob's knobs, to aid in easier collimation. Too dear in Aus, but cheaper from USA.
Are they worth the $$
I have a 10" GSO Dob, which I believe uses the knobs made for 10" Meade Lightbridge.
Is it better to get knobs for both the primary and secondary mirrors?
Thanks :)

http://www.astronomics.com/main/product.asp/catalog_name/Astronomics/category_name/BGX78LRPJXMA9P660WF9D9WXJ1/product_id/BKLB10P

[iceman]

Hi Liz

I reckon they're great - definitely easier for primary collimation. I didn't buy the ones for the secondary - I was happy enough using a screwdriver for those.

[astronut]

Liz,
Yes, they are an expense, but..................they are certainly worth it!!
I bought my 12"LB three years ago before they made the current changes.
It was a royal pain in the @$#%^ to collimate either the primary or secondary mirrors, plus it would take forever!!
There was also a chance of dropping your screwdriver onto the primary whilst trying to collimate the secondary.:scared:
Spend the money Liz, it will be well worth it.
I bought my knobs from http://www.astronomy-shoppe.com/ go to the "Dob Kits" section for the information.:thumbsup:

[Dennis]

Hi Liz

I fitted a set to my Celestron C9.25 and they do a great job there – no problems.

But, on my Takahashi Mewlon 180, they were far too tight to adjust and I used to get really sore fingers and in the end, one of the finger/thumb knobs on the top sheared off from the threaded shank below. Fortunately, it exposed a socket head cap screw, so I could then remove the threaded part with an Allen Key. To qualify this, I have read several posts on the Tak forums complaining about the too tight original collimation screws on the Mewlons.

Cheers

Dennis

[erick]

Yes, and buy a new set of primary support springs at the same time. :thumbsup:

[Liz]

Yikes ... now its looking complicated.
Do I need ... springs?? Although, in saying that, I remember that one of my springs is buggered anyway .....


Thanks guys ... will get some quotes from the US.

[erick]

Never had to replace them myself - the 12" I bought had the job already done. From reports, 8" seemed to be OK, 12" seemed to definitely need stronger springs to prevent slight sag. 10" in the middle - so maybe.

One approach is to pull the mirror further down towards the bottom of the tube so the springs are under increased pressure and should be less prone to any sag. When I bought my second-hand scope, the previous owner had one collimation screw pulled up tight and adjusted primary collimation with the other two - hence keeping the springs well compressed. I've since given them all a bit more slack so I can play with all three.

It's just, if you are changing the knobs, the springs should be a simple change at the same time.

I reckon the secondary screws are more important to avoid dropping that screwdriver or Allen wrench onto the primary - Ouch!

[chrisp9au]

Hi Liz,

I'm wondering how you determined that the GSO dob collimating screws are the same as the LB?
Would it be safe to assume that my recently acquired 12" GSO dob are the same? See attached.

Cheers :thumbsup:
Chris

[stephenb]

Liz, They are worthwhile, but I question how much dearer they really are here vs. buying them from the US. Your link shows them at $29.95 USD which at todays exchange rate, will cost you $37.60 AUD then shipping on top of that. BinTel (for example sell) them for $44.00. That's only $6.60 more. Not really "too dear in Aus". Ring BinTel for a price and ask their postage costs. I reckon at the end of the day you won't be saving much.

Good luck.

[iceman]

I can confirm they are the same. It stated as much on the Bob's Knobs site.

They fit my 12" perfectly.

And yes, I also bought the heavy duty springs at the same time. Well worth it.

[chrisp9au]

Thanks Mike,

I've found them at Bintel and they are $44 Australian, so it's definitely worth buying local!
https://www.bintelshop.com.au/Product.aspx?ID=6492
They are going on the $150 12" I scored from Clive last week! Still pinching myself!

Cheers :thumbsup:
Chris

[erick]

:eyepop: Well done!

[Liz]

Yes, looks like prices are similiar to the US, at just under the $100.

Chris - you must be only buying a set for the primary??
Didnt want to pay $100 .... so perhaps I will get one set at a time :)

[chrisp9au]

It certainly pays to shop at Ice Trade Classifieds! :)

Chris

[GeoffW1]

Hi,

Being a tru-blu patriotic beer-guzzling pie-scoffing thong-wearing Aussie, run the pants off a kangaroo, I have to ask this..

why can't we get a local manufacturer of these b...dy things? It's enough to make me run out, buy a Hercus 260 and do it meself! I done me time on the lathe after all.

Stone the crows, what has happened to us?

[chrisp9au]

Hi Liz,

Bintel's price is $44 for the six knobs. Try the link, give them a call, what have you got to lose?

https://www.bintelshop.com.au/Product.aspx?ID=6492

Cheers :thumbsup:
Chris

[Solanum]

I recently bought the primary knobs, secondary knobs and primary springs from Bintel. They are a lot of money for what they are. I suspect if you had the right dimensions/thread sizes you could buy something similar from an engineering/hardware supplier for 10% of the price. There is noting particularly special about them as far as the manufacturing goes.

However, that said, they are a lot better than the GSO supplied ones (not needing a screwdriver is easier and safer for your mirror for a start), and they make collimation a LOT quicker/easier. The combination of Bob's knobs and my collimator mean I can collimate secondary and primary in about 1-2 minutes at the most now.

So my summary is, if you can afford them, then they are well worth it. But they don't do anything your current screws do, so if money is tight....

[GrahamL]

guess you could diy it with a little time and resolve :)
http://www.smallparts.com.au/store/categories/knob/

$44 dosn't seem a lot imo to have another work it out and just post it straight to us though.

[Solanum]

It's not $44 for both sets of knobs and the springs, it's $96! Which is a lot of money for 6 screws and 3 small springs! Anyhow, I wasn't saying they aren't worth it (I certainly felt it was easier just to pay that than try and find the equivalent parts), just that there is nothing that special about them and with some effort I'm sure one could save some money. The springs in particular are fairly roughly finished (but very strong and they actually don't need to be sanded smooth).

Nice link by the way, those knobs look remarkably like the Bob's ones!

[JethroB76]

Agree with this.
I ordered these way back before Bintel listed them on the website and with out a price and was a bit shocked when they came in and they were ~$96+post.
Great mod though, whether you buy the premade ones or do your own.

[chrisp9au]

I note that a few people have paid a lot of money for these knobs from Bintel, but that is not my experience.

A set of six knobs, 3 collimating and 3 locking, for a 12" Meade LB, or the GSO 12", just cost me $54.00 including postage from Bintel to central Victoria. The price was confirmed over the phone at time of purchase.

Great service, as always, from a very reliable Australian supplier.

Cheers :thumbsup:
Chris

[richardda1st]

Hi all, I don't get all this fuss about the knobs. Maybe it's because my 10" Lightbridge is still new.

I applied a very small drop of sewing machine oil to all the thumb screws and the truss tube mounting screws, with a wipe with a tissue to prevent any possible run-off from the oil. All threads should be lightly lubricated which results in minimum force to tighten and loosen, otherwise most threads tend to bind and wear. Anyway, maybe if I can get to use my scope more often I might find that I'll also will be looking for Bob's knobs.

I think thumb screws for the secondary is a good idea.:shrug:

[JethroB76]

The new lightbridges have tool-less primary collimation out of the box don't they?

Chris, the knobs and spring kit cost $96 (primary and secondary knobs and three springs).

[Tamtarn]

One of the first things we fitted to our Celestron C9.25 when it arrived was a set of Bob's Knobs to the secondary.

A very good investment indeed. :thumbsup:

[stephenb]

I think a clear distinction needs to be made about the issues of "Is the collimation set: (a) too expensive here in this country, (b) BinTel charging too much, or (c) or just expensive alltogether.

For example, the parts for a 10" Lightbridge from Astronomics in the USA:

- a set of primary and secondary knobs is $49.95 USD (here (http://www.astronomics.com/main/product.asp/catalog_name/Astronomics/category_name/BGX78LRPJXMA9P660WF9D9WXJ1/product_id/BKLB10ST))
- a set of springs $16.95 USD (here (http://www.astronomics.com/main/product.asp/catalog_name/Astronomics/category_name/BGX78LRPJXMA9P660WF9D9WXJ1/product_id/BKLBSPR))
- Total $66.90 USD or $84.65 AUD (at current exchange rate)

- Cost at BinTel (everyone seems to be quoting them) $96.00 AUD

That's only $12 more. Seems totally reasonable price to pay in this country, considering the USD price to a US resident.
I had them fitted to the LX90 on purchase and I believe they are a worthwhile addition to any scope, particularly SCT's with the fiddling around near the corrector plate.
hoo roo,

Stephen

[Liz]

Yes, I agree Stephen ... the prices are not that much different, so obviously go OZ. I will when I finally get them.
As Chris says - a set of 6 knobs for primary mirror is $54 incl postage.
I need springs as well, and would like secondary knobs too ;) so puts price up to around the $100 ish.

[Solanum]

I don't think anyone claimed that Bintel were gouging, just that Bob's Knobs are expensive. They make collimation significantly easier, but don't actually enable you to do anything new and that is what you should bear in mind when deciding to buy some.

Also, looking at the link given above, if you know the correct screw thread and knob dimensions, you could probably buy the same for a fraction of the price.

[astronut]

Buying the knobs may not allow you to do anything different, BUT.......the job of collimation will be significantly better and easier.
On my 12"LB, the original configuration needed a flat blade screwdriver for the primary and phillips head screwdriver for the secondary.
Consider trying to insert a flat blade driver onto the screw head in the dark!!:scared: or holding a p.h driver over your secondary to collimate it, with the possibility that it could slip from your grasp and fall onto the primary!!:scared:
All of a sudden the $80 - $100 for the improved versions appear quite cheap.

[stephenb]

No worries, I was just trying to clarify the original argument for Liz.

You are quite correct also with sussing out a DIY alternative. As Nightstalker suggested, the company: http://www.smallparts.com.au/store/categories/knob/ (http://www.smallparts.com.au/store/categories/knob/) looks like a great source of parts for this purpose. I have bookmarked them also.

[Solanum]

And to perhaps end this thread I would just like to congratulate everyone for managing 30 posts on Bob's Knob's without a single 'knob' joke! I don't know about anyone else, but I've found it quite hard!

[stephenb]

:clap::clap:

[astronut]

:lol::rofl::rofl::rofl::rofl::rofl:

[beefking]

:lol:

I've put the secondary knobs on my skywatcher dob, and they've made collimation significantly easier. no tools, and you can turn your attention to which way the mirror needs to go instead of figuring out why the allen key is slipping.

well worth the $30 bucks or so.

[Liz]

:whistle: ... I think I must have an innocent mind.



"I've put the secondary knobs on my skywatcher dob, and they've made collimation significantly easier. no tools, and you can turn your attention to which way the mirror needs to go instead of figuring out why the allen key is slipping.

well worth the $30 bucks or so."

Did you get ones for the primary too Nathan, or just the secondary?

[beefking]

Just the secondary. The primary collimating knobs supplied on my skywatcher are very similar to bob's knobs. I may need to upgrade the springs, but my scope holds primary collimation very well (imo) already.

[mozzie]

i wonder how long till they make skywatcher primary mirror knobs i suppose its all supply and demand
mozzie

[AndrewJ]

Dobs Knobs cant be that hard,
you should try an SCT when you cant reach yr knobs whilst looking into the EP.
However, it is much easier if you stick a bicycle spoke into the side of yr Knob first :o

Stop thinking those thoughts and look at the piccy.

Andrew

[erick]

:love::prey2::einstein: clever! thanks.

[JethroB76]

Bonus diffraction spikes?:lol:

[NeilW]

How close would the primary threads on a GSO 8" Dob be to the equivalent Skywatcher? My SW just has allen head screws on the primary, so a set of Bob's would be a significant advantage. I'm surprised that they're not available.