Flextube Dobs

[A McEwan]

Hi all.

I've seen a few of you getting these funky new collapsable Dobs recently. They look very tempting. Nothing definite planned yet, but I may be thinking of getting a 10" or 12" in the future, to replace my 8" f6.

Before I do, I have several questions.

How heavy/bulky are the 12" and the 10"? Is there a big difference between the two? Does the optical advantage of the 12" validate the extra weight/bulk?

What is the width of the rocker box for the two models? I'd need to know how easy it is to get into my small Panda (car, not animal).

Are there any recommended hardware upgrades needed out of the box? Collimation knobs, mirror support springs, focuser etc - do they all function fine without needing to be instantly replaced? What about the rocker box motions?

Does anyone produce a shroud for them? Is a shroud even really needed?

Many thanks for your input.

Ant 8)

[A McEwan]

And... In pictures I've seen, the tube assembly seems to be attached to the rocker box by means of the tension-twist handles. Is it possible to detach the OTA for moving around separate from the rocker box easily? Can it even be used without the tension twists in place?

And finally (maybe) is he primary mirror centre-spotted?

Ant

[John]

Hi Ant,

I've seen a 12" but not looked through it (TJ has one for sale BTW).

It is a big scope when extended (same size / weight as the Lightbridge 12" which I've just bought). It can be carried in one piece by one strong person but I would personally separate the OTA from the base to carry it - I have had back problems in the past !.

It looks quite compact when folded of course - but still weighs the same !!!.

I think the rocker box base is about 25" wide (again same as Lightbridge).

Shrouds are a bit of a challenge because of the 3 strut design - you need to find a way to stop the shroud material flopping into the lightpath - extra struts built into the shroud ?. I don't think there is a commercial shroud available - yet.

The tension handles work in the same way the ones on regular Skywatcher dobs do - I doubt the scope would be steady without them in place - my 8" SW dob certainly was not. They do unscrew / screw in very easily so it's no hassle to remove them and lift the OTA free of the mount.

No mods needed to use out of the box as far as I know.

Excellent scopes I think - the one I saw was Ade Ashfords review one and he was very impressed with it. I would have bought one but I got a good deal on a Lightbridge 12" from another SGL member so I've gone for that.

Hope that helps,

John

[Astronut]

I have the sold tube 12" and the mirror was centre spotted with a dougnut which I've since replaced with a Catseye collimator triangle. I see no reason why the truss version's mirror should be any different.

The solid tube fits in my Citroen Saxo with the passenger seat folded down. Obviously the truss version when collapsed will be much more compact.

The optics and mirror cell in the truss and the solid tube are exactly the same so no need to worry about the collimation springs and knobs - they work just fine and are a very good design. I've had no problems with the solid tube's mirror cell. The focuser on my solid tube was a single speed crayford with no compression rings which I later replaced with a dual speed Moonlite with compression rings. The standard Crayford supplied was very good though.

It's been said that the views through a 10" after an 8" aren't nearly as noticable as the difference between an 8" and 12".

There are a few members who have the 12" truss and one of them will be able to comment further. I haven't noticed anyone on here with the 10" truss but there might be someone.

[ZOG]

Hi ant, I have the 12 inch version. The width of the base of the mount is 25" and the height form the floor is 30 inches. it goes in the boot of my Octavia vertically with the parcel shelf removed. The lenghth of the OTA collapsed is 95cm which again will fit into tne boot.

It is a heavyish scope and I wouldn't try to lift it in one piece, but when the tensioning handles are removed, it is easily moved in two parts. The mirror is centre spotted, and the springs seem up to the job. Collimation is via three large thumbscrews with 3 further, smaller locking thumbscrews. The focuser is a single speed crayford type and is smooth enough. Alt and Az movements can be controlled with finger pressure although you have to set the Az tension when building the base.

I don't know what the difference would be from an 8 inch scope but the difference from the 130 pm is huge. I'm sure Steve at Flo had the shrouds on his site, Not needed in a dark site but if you have any LP I'd recommend one.

All in all I can highly recommend the scope. Hopefully one of the 10 inch owners will be along shortly to give you the info on that version.

Bill

[vlebo]

I agree with everything Zog says, my only upgrade would be a Moonlite focuser or the new Skywatcher Crayford focuser which uses the existing holes on the Flextube as I find the stock one a little coarse to use .

On another note , if you are considering getting one soon , keep an eye on prices as they are already beginning to rise and you may be better off getting one sooner rather than later.

Vlebo

[A McEwan]

Thanks very much for the information and opinions so far, folks! That's just the sort of stuff I was looking for. Personally, I'd have to carry the 'scope in two parts I think as well, so it's good to know that the OTA can easily separate from the rocker box.

So it sounds like a Dob that neds nothing done out of the box? Surely not? Who would have thought such a thing would ever happen...? :shock:

Ant

[MikeP]

I can only provide information on the 12” – I have the original all white model but I doubt it is very different from the latest two tone version.

How heavy/bulky are the 12" and the 10"? Is there a big difference between the two? Does the optical advantage of the 12" validate the extra weight/bulk?

The OTA weighs about 46lbs (OTA, me, bathroom scales and a bit of subtraction) and using the same technology, the mount weighs 44lbs. The OTA is easy to carry despite it being bottom heavy. The mount is clumsy to get hold of but can be carried one handed using the handle on the front.

What is the width of the rocker box for the two models? I'd need to know how easy it is to get into my small Panda (car, not animal).

The rocker box sits on a circular base that is 25” in diameter. The rocker box itself is only about 17.5” wide but stands about 28” above the ground. You could have difficulty getting the base through the rear doors of a 4 door Panda (if they exist) but I doubt there would be a problem putting it in via the tailgate. If you really had to, you could disassemble and reassemble the base quite quickly.

Are there any recommended hardware upgrades needed out of the box? Collimation knobs, mirror support springs, focuser etc - do they all function fine without needing to be instantly replaced? What about the rocker box motions?

Works right out of the box, but we are never satisfied are we? So ….

I use a collicap and/or laser and give it a quick tweak when I take it out but we are talking fractional adjustment if anything.

The focuser is perfectly OK but I replaced mine with a dual speed Moonlite – it is better (as it should be) but a luxury.

The azimuth axis was very slightly coarse so I took it apart and added a bit of grease, now very smooth.

Since I have a very large patio area and a lot of trees to dodge, I attached three lockable castors to the base. I can move it around with ease without taking it apart. If there were no steps between my shed and my patio, I would never take it apart.

The secondary has a tendency to dew up. I tried to make a shroud from a camping mat but found it to be more nuisance than I was prepared to put up with, so I bought a secondary mirror heater which works well.

Finally, I replaced the finder with a right angled version and a Telrad.

Does anyone produce a shroud for them? Is a shroud even really needed?

Not that I know of. It is possible that the Astrozap one for a Lightbridge could be adapted - I’ll be having a look but frankly I’m not too bothered now I have the secondary heater.

And... In pictures I've seen, the tube assembly seems to be attached to the rocker box by means of the tension-twist handles. Is it possible to detach the OTA for moving around separate from the rocker box easily? Can it even be used without the tension twists in place?

Yes, the handles take under 30 seconds to remove or replace (even with cold fingers).

I would not advise moving the mount and OTA together. Despite being under 100lbs, it is a very awkward object for one person to grab hold of and carry.

I would not advise operating the scope without the handles and it would be a pointless exercise.

And finally (maybe) is he primary mirror centre-spotted?

Yes with a donut shaped sticky thing.

[A McEwan]

Sounds great - thank you all for answering all of my questions, that was really helpful! And yes Mike, it is a four door Panda. Takes the rocker box of my 8" dob in front seat and tube across the back, but I'll have to measure up to see if the 12" Flextube will fit. I think it will...

Thanks again,

Ant 8)