First light with my Lightbridge 12"

[John]

It was one of those nights designed to really frustrate the astronomer, especially one with a new scope to try out !.

Over North Somerset (my base) we had tempting spells of clear skies but then lots of clouds drifting over every 30 to 60 minutes obscuring just about everything for quite long periods - before the next tempting clear patch beckoned .....

At around 11:40 pm the sky looked pretty clear in all directions. My family and our neighbours had gone to bed so the surrounding lighting was reduced quite a bit. The moon was 88% illuminated which was not so good for DSO's of course but I gave way to tempation and set the Lightbridge 12" out on the patio.

My previous scope was a Skywatcher 8" dob which I could carry out in one piece - not so the 12 - the routine here is:

- lift optical tube off mount (the tube weighs around 21 kilos).

- stand tube on newly added "feet" fixed on the base (the original design would stand on it's collimation knobs which is not good).

- position mount outside

- lift tube onto mount

- connect 12v supply to cooling fan and retire for a coffee

Oh boy was I impatient tonight after just 25 mins I could not resist a gander though my 31mm Nagler - and the view was not bad at all, rather suprisingly ! - out of focus star images still showed a fair amount of tube currents swirling about but at 49x it was fun just to sweep around a bit - I left the fan running initially which may or may not have helped the image but I manage to find the galaxy pair M81 and M82 - pretty bright despite all the moonlight and signs of the dark patches across M82. They both fit with ease into the 1.67 degree FoV that the Nagler 31 gives with the scope - it's going to be a superb view on a dark, moonless night

Switched the fan off now, popped the 16mm Nagler in and had a quick look at Mizar and Alcor to see how the image was settling down. Mizar was a clear double but the stars were still a little "hairy" so the optics were still cooling (this was after all only about 40 mins after the scope being put outside from the dining room).

I really wanted to catch Orion and M42 in particular so I had to move the scope. Same routine (without the fan) taking care to put, rather than drop, the tube onto the altitude bearing cutouts on the mount. I'm getting the routine for this now.

With the moon so bright M42 was never going to be that great, even with 12" of aperture. I was actually pleased with what I saw - lots of sweeping nebulosity, dare I say it, with even a slight green tint to parts of it ? The trapezium well resolved and the stars actually beginning to look more compact. I could not see E and F but I was not expecting to do so under these conditions. It was though a real appetizer for dark skies with this scope

Then the clouds started to show again after barely and hour and with the scope not fully cooled so I snatched a quick look at Sigma Orionis, one of my favourite multiple stars and saw 4 componants clearly - the star images starting to look encouraging now.

I also had a quick look at Betelgeuse to check the collimation of the scope. I did not have time (clouds really becoming a pain now !) for anything other than a quick look at the intra and extra focal images at 169x but the shadow of the secondary looked pretty central so my simple cheshire eyepiece must be doing a reasonable job. I was just starting to get hints of diffraction rings as well as I tightened the focus with is encouraging.

And that was it - the clouds rolled in and my appointment with the universe was at an end - for tonight at least

Two trips saw the scope back inside with the primary safely covered up.

I learned a few things from tonight:

- The scope is capable of great things

- I can collimate it and it holds collimation reasonably well for a truss tube dob, at least it survived moving arond the garden a bit !.

- Ideally the scope will need a good hour to cool and will imprive further for another hour after that I reckon - that fan does seem to move things along a bit faster though.

- The 16mm Nagler is going to be a heavily used eyepiece in this scope - there is something "just right" about the view it gives.

- While not "grab and go" by any means it really is a managable 12 inch scope that can be set up in a matter of minutes and bought in just as quickly.

- A light shroud is a real must (as others have already suggested to be fair) the amount of ambient light that finds its way though the truss framework and onto the mirrors is significant and must reduce contrast a lot.

- I have a lot of admiration for those that manage the 16 inch version of this scope :shock:

Thats all folks ! - can't wait for the next chance to view

John

[ZOG]

You're gonna love that scope on a dark sky night John. I had the 12" out tonight, spent a lot of time on the moon, plaedes, and M42, but the highlight of the night was Saturn, seen rising over the top of my kitchen extension and subject to rising heat, but I clearly spotted 4 moons. These big dobs are the business aren't they ?

[Jamie]

Hi John

I had the priveledge to use my 12" flextube in anger back in November at Kielder with a 13mm ethos eyepiece. Stunning views!!!!

A very under rated scope me thinks.

You will surely have a ball with this one matey..

[russ]

Nice one John, i knew you wouldn't be disappointed. And that's just a moonlit appetiser.

There's something about the 12 dob. Very easy to setup quickly, easy to use and great views. Cool down on those big mirrors is long, even worse on the Starfinder as its a closed tube mirror cell.

It's worth checking out the moon too with that big aperture.

[davo]

Superb report. Was with you all the way. I must try Sigma Orionis myself. That's a new one. It's good to hear thats others are getting some observing in. It's been so cloudy here for days and days. Does anyone have an anti-rain cloud gun??

[Doc]

Nice report John.

I'm drooling over your collection of naglers, I just wish i could afford them if they are good in your 12" how much would I see in my 16".

One thing I have found is these beasts take ages to cool down, I have to leave mine a good 90 minutes before the turbulence at the eyepiece dies down completely.

And yes you should see alot of green nebulosity round M42 I do.

[Andrew*]

Excellent report, John,

Glad you got it finally and it's delivering the goods

I hope you don't find the set-up too inconvenient with time...

Andrew

[John]

Excellent report, John,

Glad you got it finally and it's delivering the goods

I hope you don't find the set-up too inconvenient with time...

Andrew

Thanks Andrew

Thats a good point about convenience - I think I've accepted that the move a larger aperture comes at the price of having to be a bit more organised about my observing. If the conditions and / or my mood mean that I don't fancy using the 12" then I've got a good 4" Apo in the Vixen ED102SS for more casual / ad hoc observing.

John

[Andrew*]

Got it all worked out!

[lunator]

John

Nice report

Looks like you've got a great combination of scope & eyepiece

Maybe you could call the 12" set up a "grab & drag" set up?

Cheers

Ian

[rusirius]

Your report seems to echo my experience with my Flextube 300P f5 and Nagler 16mm. Same mirror size, same f ratio and same eyepiece focal length (I have the T2). Its been my primary eyepiece since I acquired it and as you say something feels just right about that combination. Also seems to work well with a 9mm Ortho.

[John]

Had a longer session tonight (Tuesday) and managed a bit over 2 hours with the LB 12 before clouds intervened. After around 90 mins the scope seemed to have cooled (it had come from a centrally heated house) and the tube currents were not too obvious in an out of focus star image.

I've put some feet on the bottom of the OTA so it does not stand on it's collimation knobs as I move it and the base around now. Collimation is held much better though I don't seem to need to use the collimation lock bolts - just the collimation knobs.

The Astrozap light shroud has now been added which makes a big difference to contrast. I reckon that I might still benefit from a top of tube light shield as well though - there are quite a lot of lights around where I observe that can send light bouncing down the tube.

I also need to seriously consider counterweighting the tube lower end - the light shroud has added some middle to top end weight so even the 1.25" Naglers cause the OTA to "droop" when viewing low altitude objects. The brake fitted to one of the altitude bearings is NOT very efficient. There are lots of DIY weight solutions for Lightbridges on the web thankfully.

I stuck to well known favourite objects again tonight. M42 was simply lovely - especially with my 16mm and 13mm Naglers. With a little averted vision, I could see the dark rift through M43 (immediately adjacent to M42) while M42 itself was full of lime green (or so it seemed to me) swirls of nebulosity. To me M43 seemed a slight tinge of pink compared to the pale green of M42 but it was an extremely subtle effect.

The trapezium stars were very well defined and, with careful scrutiny, I could make out the E componant and glimpse, on occasions, the F star. The 13mm Nagler (117x) was ideal for this work. I was pleased with this result because it shows that the optics of the scope are decent and not far away from good collimation despite the hefting about that seems to go with operating a 12 inch scope.

Moving on into Taurus I had a look for M1, the Crab Nebula. I found it fairly easily and it was reasonably bright with 12" of aperture although still an object that is easily obscured if there is any hazy cloud about or moonlight.

On to Gemini now to view the M35 open cluster - wow ! - right in amongst the stars with the 16mm Nagler (95x) and a nice, albeit faintly, resolved view of NGC 2158 nestling to one side of M35 and once considered as a potential globular cluster. Whilst in Gemini I tested the scopes optics again on Castor and got a nice split at 117x - Castor being a double star.

Last objects of this session were the galaxy pairing of M81 and M82 in Ursa Major. Again the Nagler 16mm give the best composed view (although the 31mm Nagler was used to find the galaxies) with both objects in the same field. I'll aim to spend some more time on this pair in a future session.

Overall a nice experience with the Lightbridge 12". It's harder work than my old 8" dob and you really have to think about where you set it up as it's much more effort to move around. Cool down needs to be allowed for as I store the scope indoors which cramps it's style as a grab and go somewhat.

As well as the counterweights for the tube, I'm really going to have to get a proper observing seat (a Lidle Ironing Seat ?) - sitting is much more relaxing than standing / stooping and I'm sure the eye takes in more if the observer is relaxed.

I've got Bobs Knobs for the secondary mirror on the way from the USA and a Baader Laser Collimator en route as well so I'll be even better prepared for the next session with my "big white cannon".

John

[Doc]

I'm glad you are having fun.....

Try flocking the OTA that cuts down alot on stray light. Also what colour are your truss poles are they still white, make them black and that seems to work a bit as well.

[lunator]

John

Nice report.

The M42/43 colour contrast is an interesting effect.

Cheers

Ian

[John]

I'm glad you are having fun.....

Try flocking the OTA that cuts down alot on stray light. Also what colour are your truss poles are they still white, make them black and that seems to work a bit as well.

Thanks Doc,

The truss poles are still that dull silver colour as supplied. Blacking them up is on my todo list. I was looking out for some black / very dark grey pipe insulation as I've seen that used on other LB's.

Flocking ditto - at least the job is made easier by there being less tube to flock with the truss design plus the tube that is there is pretty accessible.

These scopes are definately a "work in progress" as delivered - but I think the optics are pretty good - plus it's actually quite satisfying to incrementally improve the scope although I might have been a tad frustrated if I had bought one new and paid £800 for it - and still had to apply all the fixes

John