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