Meade 12″ Lightbridge

Well my 12” Lightbridge arrived today thanks to Steve at First Light Optics. The ‘scope arrived in 2 large boxes, one for the IKEA style base and one for the OTA. The boxes were single skinned which is a shame as it wouldn’t have cost much more to double skin the boxes and even though my Lightbridge wasn’t mishandled and arrived intact, I can imagine others being easily damaged. Anyway, it’s a small thing.

The first box contained the base which is made from standard MDF fibre board covered in Formica.

The needed tools were supplied (Allen key) and it was very easy to put together. There was a disc of roller bearings supplied which is sandwiched between 2 sheets of Teflon (?) and then the top board and ground board. There is a central bolt which can be used to adjust the tension between the 2 boards (the Az tension). You can see me industrially putting the base together in this image and you can see the bearing sandwich in the background. (You can also see the OTA and is a bit of a giveaway that I didn’t put the thing together in the right order as I was too eager to see the mirror hehe, but I’ll write this review in the right order!)

The second box contained the mirror ‘box’, the UTA and the trusses. It also contained the 2” 26mm QX series 4000 eyepiece. I was a little concerned about the mirror cover as I’d read in other reviews that it had come loose and damaged the mirror coatings with other people. I was confused at first then to see the mirror cover resting on the TOP of the box. Upon unpacking it seems Meade is getting around the problem of the mirror cover scratching the mirror by NOT installing it in the first place! The mirror box was simply in a plastic bag with nothing covering the mirror. Seems like an effective and simple solution to me!

Putting the OTA together took even less time than the base. Just 3 truss sections, the mirror ‘box’ and the UTA. The UTA (Upper Truss Assembly) is thankfully very light, just 7lbs. This makes it easy to lift and attach the truss poles. The mirror ‘box’ is the heaviest component (obviously) containing the 12” mirror and the 2 aluminium bearings. The tolerances are very tight and the bearings slightly catch on the base making the Alt movements a little tight. I’m sure though that after some use it will “break in”. The base uses just felt as a bearing surface and I am unsure as to the ability of felt to stand the test of time (felt compresses) and I may replace the felt with Teflon at some point in the future.

Once the OTA was sat on the base pretty much everything was done. It took me less than 30 minutes to put everything together and that included opening the boxes! I was very pleased at the lack of tools needed also as this means less fumbling in the dark when using the ‘scope in anger. I did notice that the OTA base does just catch the Az tension adjustment screw which is a shame as a few extra mm in the side boards would have cleared this. I did have a quick look at the collimation and found it to be WAY out, but I haven’t had a play yet as I have a set of Bob’s knobs on order from the states so until they arrive in the next day or two I’ll leave it be.

Here’s another picture of yours truly to show the scale of the 12” scope. (You can also see the bags under my eyes too due to my daughter going through a growth spurt and wanting to be fed every 2 hours! I’ll have to have a shave at some point too). I’m 5’8” for reference.

This is the largest scope I’ve owned (perhaps the 8” f/8 was a little longer but the 12” is certainly fatter!) and over all I’m very pleased with it so far. I’m 100% sure that there will be thunder and torrential rain until Christmas now but I’m in no hurry for first light! The Lightbridge is now safely stored in my astro shed under lock and key, and the 80lb weight shouldn’t be too much of an issue as I only have to drag the whole thing 6 foot to use it.
As always I hope to update this thread once I’ve had a first light!

[update]
Finally managed to get a good first light of my 12” Lightbridge tonight. The night started out clear at about 6pm but by the time I’d had my dinner and got outside it was misty! Thought it was going to be another useless night and nearly opened a bottle of merlot but by 8pm the mist had cleared enough to make me think it might be worth going out for an hour or 2.

I dragged my Lightbridge out in 2 trips: I keep the OTA assembled and sat on the base in my shed and I took the OTA out in the first trip and (gingerly) placed it down on the collimation screws. I REALLY need to sort out some rubber stoppers for the OTA base so I can set the OTA down on its end without knocking the collimation. God knows what Meade were thinking when they designed the base of the mirror box! Anyway, second trip to get the rocker box, then pick the OTA up again and drop it on the rocker box. Easy peasy and a 2 minute setup.

A note about the fan, I’ve recently installed a set of bobs knobs for the Lightbridge and replaced the primary mirror springs with sturdier versions to prevent mirror flop. A slight problem with the fan is that the new bob’s knobs knurled nut cover the power connector so it’s impossible to plug the fan in with bobs knobs installed. [update] Actually if you turn the knob just so, you can get the connector between the knurls! Not ideal but it works. Although this doesn’t affect me as I keep my Lightbridge in my shed so don’t need cooling as it’s always at ambient but for people storing their ‘scope in the house this could be a pain.

This is the secondary with Bob’s Knobs installed

And the rear of the primary

Next was removing the primary mirror cover. This flimsy piece of plastic is all that protects the primary mirror and to be honest it’s a load of rubbish. The plastic is a cheap vacuum formed pile of crud and I wouldn’t trust it to protect my shaving mirror let alone my 12” precision instrument. I rapidly need to sort out a plywood cover for the top of the mirror box. Whilst I’m at it I also need to think about a secondary cover, but that might just be an old sock and an elastic band!

I’ve purchased a Meade laser collimator as being a truss dob it needs collimation more often than a solid tube. This didn’t take long and is much more accurate than eyeballing down the focuser. For those who haven’t used a laser before (I hadn’t) it’s quite simple. Just stick the laser in the focuser and centre the red dot on the primary centre donut by adjusting the secondary mirror tilt. Then when the red dot is centred adjust the primary mirror so the return beam is aligned with the first beam. There’s a silvered 45 degree plane on the collimator to make it easier and the system works very well. It still needs a final tweak with a star test but for me its close enough, at least for now. I’ll see how well it keeps collimation when I come to use the ‘scope again (maybe in about 6 months going by the current weather!) [update] I need to make sure that my laser is collimated as whilst I was using the ‘scope I wasn’t getting perfect focus. Easily collimated but something I missed.

The laser collimator in place

And if you look closely you can see the red dot on my primary out of collimation

A note about the red dot finder, the finder itself is quite good, and you can choose 10 levels of brightness and 4 different reticule shapes. However the supplied stalk that attaches the metal finder to the metal shoe is PLASTIC! I mean ffs, how on earth can you align the finder when it moves as you tighten the Allen keys!? I did manage to align the finder during the day but only by compensating for the flexure of the plastic stalk. For the sake of an extra 50p in the manufacturing costs I would have happily paid a few £’s more.

Anyway, once I was all setup I was ready to do some observing! I screwed in my 2” Baader moon and skyglow filter into the 1.25” to 2” adapter and my 24mm Pan was my eyepiece of choice. Turned on the red dot finder and turned to M45 first. Well a little disappointed as I couldn’t fit M45 into my FOV with the 24 Pan! Given the Lightbridge’s 1600mm focal length the FOV is greatly reduced from my 600mm ED80! I knew this was the case but didn’t realize quite how small the FOV is. I can see some expensive 2” Naglers in my future and my 3-6 Nagler zoom going on UK astro buy/sell!

Anyway not to be disheartened I changed to my 45m Plossl and there was M45 in all its glory. The 45mm Plossl isn’t ideal for this scope as it gives a 9mm exit pupil but I was quite pleased with the view despite a half moon. I changed to an 11mm T6 Nagler and centred the view on Alycone for a star test. Defocused out and was quite pleased with the results despite the rough collimation. Defocused in and got similar results. The secondary was quite prominent and I could clearly see the 3 mirror clips. I’m sure there’s a better way of attaching the mirror but it doesn’t bother me too much.

Back in with the 24 Pan and over to the half moon that was causing me such light pollution. I decided that the moon was a target and not a source of light pollution! The moon fitted nicely in the 24 Pan’s FOV and I was very pleased at the detail the Lightbridge showed. Upped the magnification to the 11mm T6 Nagler and there was no image degradation at all. Upped again to 6mm and still perfect. No “mushyness” at all even with less than perfect seeing. There was some turbulence in the atmosphere “heat haze” so didn’t push the magnification any more, but on a good night I feel I could go all the way to 3mm if I could track at that high magnification.

All in all I’m very pleased with the performance of the Lightbridge. I’m just waiting now for M42 to rise to a viewable position and if I’m not too tired perhaps Saturn too. I’m not sure how easy I will be able to track the ringed one as the stability of the dob base at high powers leaves something to be desired. With the 6mm eyepiece focusing produced significant wobble and I need to work out a way to strengthen the base without adding too much weight. I also noticed that the tolerances of the base were a little too tight and the aluminium alt bearings were catching slightly on the base sides. This meant that the friction in the alt axis was a little high but once the bearings had worn their own groove in the MDF it sorted itself out. Not ideal but I can live with that. I may help things along with a touch of grease or see about replacing the felt used with Teflon blocks, but that’s a project for another day.

One thing I did test was that my magnetic inclinometer attaches happily to the UTA! No aluminium here, just good old steel. I’m quite pleased as this is one half of my setting circles and now all I need is a 24” diameter disc for the Az circle and a chunk cut out of my top board. Easy enough to sort. Also needed is a shroud, especially in my light polluted skies. You can buy one for £60 but I think I’ll have a bash at making one for 50p instead. Can’t be that hard!

[update]
Well couldn’t see the horse or flame but then I didn’t think I would with magnitude 4 skies but to say I was pleased with M42 would be an understatement. The trapezium stood out fantastically clear although I think my collimation is off as I couldn’t quite get tack sharp focus. Couldn’t see any colour in M42 but again, didn’t really expect to, but I was impressed with the amount of nebulosity given my skies.

Once again mistook Procyon for Saturn (got to stop doing that!) and gave up before the ringed one peeked above the houses to my east. I’ll catch him another night. Off to bed now, but very happy with this first night out with the 12”, I’m looking forward to many more great nights! I might even take the time to lug it to a dark site to really test it out, but need more brownie points with the missus before then!

Originally posted 21 November 2006

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