It's arrived - 16" Lightbridge

[albedo0.39]

At last, the waiting (for me anyhow) is over and I'm now the very happy owner of a very heavy Lightbridge.

OK, it's not got much in the way of technology behind it, but it sports spankingly new resilvered mirrors by Galvoptics, blackened interior and truss tubes, a nice little light shroud and a few other discrete mods.

So now, the tweaking begins.

1) Secondary Collimation

As anyone with one of these will attest, the mechanics of the secondary are not the best from what I can see but before I start modifying it, what is / should be the correct length (approx of course) of the exposed thread under the screwhead of the 3 collimation screws.

From what I can see, if the screws are wound fully "in" (i.e. no exposed thread), the secondary mirror would be closer to the primary.

If the 3 screws are wound "out" then the mirror is further away.

Of course, the position of these screws has a certain "sweet spot" from which I start my collimation, but could someone give me a starter for 10 ?

2) I am missing the battery pack for the fan.

I'm pretty sure it takes 4 x AA batteries = 6v. However, since the LB will live in an unheated, dust free and essentially ambient outside environment, I'm wondering if it's even needed. Thoughts ?

3) Although painted matt black, I understand the upper and lower tubes benefit from adding a "flocking" material - a little like Velvet Fablon. Any ideas where in the UK I can get this from ?

4) RA Movement

What is the correct amount / type of lubricant on the RA roller bearings ? - for my bikes, I use GT85 for pretty much everything. It's a teflon based thin film but not like WD40 at all (no stickiness). It's somewhat viscous at the moment because I think it has some pretty heavy oil in the centre bearing

5) Collimation

I've read heaps on this subject for weeks now :- (lasers, barlows, cheshires etc)... but today, I was instructed how to collimate with a simple cap fitting into the eyepiece, with a tiny hole in it and a doughnut on the underside. Simple Q - the very very experienced prior owner recommended this as the very simple sure fire way of collimating this scope. We tried his ££££ laser and ££ Cheshire and both disagreed with the final "best" view with this seemingly inexpensive little plastic jobbie. Any ideas ?

OK - that's it for now - really appreciate all the help you might be able to offer

Cheers

PS - It's a very clear night and I was soooo tempted to give the fresh silver it's first light.

[Lee]

I believe a forum member is selling some flocking paper:

http://stargazerslounge.com/sale/77909-protostar-flocking-paper.html

Unfortunatly I can't help with the rest. I always wanted a look through a 16" Lightbridge... Good luck with it.

Lee.

[Sam]

Great news on you getting your 16" Lightbridge, you won't be dissappointed! The collimation of this beast is key and I think you'll get the most accurate results from the cheshire. I haven't got my fan hooked up on the scope and I haven't ever used it as I allow about 90mins for it to cool down before use which seems to be enough.

Sam

[Doc]

Another 16" LB owner. There's a few of us now with this scope.

1) As Sam has said collimation is mega important. I have onne of thos caps you are talking about and they do a great job. But I use it in conjunction with a baader Laser collimator and as llong as the laser is tightly inserted up to the edge of the focuser they both agree with each other.

On my focuser there's 13mm of visible thread showing. I've only tweaked the secondry a touch.

2) My scope has a larger fan fitted that runs of 12v. But I don't use it as I place the scope outside like Sam does 90 mins before I observe.

3) It is best to blacken all truss poles as white one do scatter the light from what I have read. Loads of options here.

4) I don't use no grease on my Az bearings. Just mmake sure they are very clean. Alt bearings are original foam ones still.

I really think the reason people upgrade there bearings to say magic slliders and teflon is basically to overcome a badly balanced scope.

So balance and collimation is key to getting the best out of your scope.

[davew]

I don't own an LB but do have a Newt. Regarding the possition of the secondary I wouldn't measure bolt lengths. Get the mirror central by use of the Cheshire or pin hole only. If it helps, get someone to hold a piece of paper between the secondary and primary first so you can't see the primary. This helps me !

So, do I have a scope in perfect collimation ? Errrrr we'll talk about that another time.

Dave.

[albedo0.39]

Thanks for all the info and updates - this afternoon, the mods begin (what price bank holidays eh ?)

First up... add stiffening braces / handles to the carcass.

Then the flocking can start...

[Doc]

And don't forget post some pics and give a first light report.

[Astro_Baby]

There was some flocking paper fro sale in the 'For Sale' section here. If thats gone then this is where I got mine from

http://www.dobsonian-parts.co.uk/wwwroot/index.html

[RichieJarvis]

Sam and the other LB owners - is he gonna need the weight mod??

Richie

[Doc]

I hope he drinks milk.

[RichieJarvis]

hehehe - cryptic, eh?

I am sure he can find a suitable donor bottle if all else fails!

Richie

[Sam]

hehehe - cryptic, eh?

I am sure he can find a suitable donor bottle if all else fails!

Richie

LOL - better be quick though I'm going to have the design patented, probably in North Korea.

[RichieJarvis]

Ahhhh - no go there Sam, I've already seen Astro-nut is using the same design.....

[albedo0.39]

Will post piccies, but the only ones I have now are of me toiling in the garage like a demented Chippie Minton (who he ?).

I even bought a new jigsaw (whatever next). From astronomy to woodworking in one easy lesson.

[John]

Nice scope - congratulations !.

I'm a LB12 owner and not too far from you (North Somerset). I get to Cheltenham a lot as the team I manage are mostly based there.

The mods on my LB12 are as follows:

- Bob's Knobs added to both primary and secondary mirror cells to replace standard items.

- Uprated collimation springs on the primary cell (this might be only an issue on the 12's).

- Low profile azimuth tension bolt - the original tended to contact the OTA when it was pointing towards the zenith.

- Astrozap light shroud.

- Blackened the truss poles using black Armaflex foam pipe insulation.

- Meade SCT sliding counterweight assembly added to lower OTA - these scopes are really nose heavy with a big 2" eyepiece in the drawtube !.

- Replaced supplied multi-reticule RDF with Rigel Quickfinder.

- Backed off primary cell locking screws and I don't use them at all now as they seem to flex the primary cell (affecting collimation) as well as locking it.

The fan battery pack on mine uses 8 x AA batteries but I use a portable power pack when I choose to use the fan, which is not often TBH.

The LB's are a bit of a "work in progress" when they come out of the box but I'm enjoying mine a lot now I've made those mods.

John

[albedo0.39]

Nice mods John - I'm especially interested in the thought process you had in the Rigel Quickfinder. I have not used the Red Dot, but it looks intuitive. Also, the previous owner (a very serious amateur with about 10 scopes) said he had no issues whatsoever with this kind of finder.

Why did you change ? The one I have looks quite workmanlike and is lightweight so I'm wondering what benefit you had / have up to now ?

Also, you are right about the primary mirror clamps. Previous owner did a very detailed report on the scope and complained about the astigmatism until he discovered the clamps were too tight. He then loosened so that they are +1mm from the mirror. Result ? = no astigmatism.

Steve

[John]

Steve,

I was referring to the mirror cell locking bolts which I don't tighten - but I have made sure that my primary mirror clips are not tight on the mirror as well.

My beef with the supplied RDF finder is not so much the finder itself (although even at it's lowest setting it is a little bright I find) but with the plastic stem that it's mounted on - too much flex which makes it difficult (I found) to accurately align the finder with the scope. As I only use an RDF I like to have it spot on and I've found the Rigel Quickfinder a) much easier to get to the right brightness easy to align with the scope and re-align if it goes off a bit and c) I like the .5 degree and 2 degree concentric ring pattern. I guess a Telrad would be good instead but I'm keeping the weight at the top of the OTA to a minimum.

I've still got the original RDF though - it's a good enough finder on a rather poor plastic mount !.

John

[calibos]

I have an aluminium stalk on order for mine. As for it being too bright. I have seen a mod where someone cut out a square of a cheap plastic sunglasses lense and glued it in front of the LED emiiter.