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Dobsonians full tube or strut?


ChrisKnipe
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at that aperture (to me anyway) there's no advantage of a truss over a full tube.

the full tube will fit across the back seat of a car and the only difference in space taken up is vertically.

I prefer a full tube generally speaking and even have a 16" f4 dob which fits into the back of my Rover 214 hatchback with the back seats down.

the only proviso to the above would be that I think it's only the truss one that comes with tracking (NOT goto)? tracking is an excellent option to add if you can afford it.

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I agree with Moonshane, the only reason I can think of for opting for an 8" strut is if you have limited vertical storage height. Otherwise a solid tube makes more sense - it's lighter, can be mounted on a GEM, and it's cheaper :D

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Agree with the others, the solid tube makes the most sense.

I've ended up with the 10" truss simply because no solid tubes were available. But the 10", like the 8", makes no sense what so ever as truss tube.

The truss tubes also have serious balance issues. My 10", even with no accessories fitted just wants to nosedive if the tension handles are released. Highly annoying.

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skywatcher 250PX 10" solid tube here...love it!

i know someone with the truss and they prefer the solid tube to the truss type...plus you get a bit of benefit with slightly increased dew prevention and slightly increased contrast

Edited by banner001
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Solid tube, I always worry that dust will get in between the struts. And that alignment would be a big issue. I have an f6 Newt which JUST fits across my back seat which I was very lucky with as I didn't measure up before buying it. Let us know what you go for.

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Just to put the counter argument: I've got a Skywatcher flexitube dob (10") and I think there are advantages with this design. It easily fits in the car, carrying is significantly easier since your arms are less spread out, and getting it through doorways is easier (I have also tried this in the operational position). It also sits at chest height in the garage meaning that things can be stored on top of it.

Collimation is absolutely not an issue with this design, its rock solid repeatable. Dust isn't an issue since out of the box it comes with a cap which fits on the lower tube, and stray light isn't an issue if you make a collapsible shroud like wot I - or should I say my wife - did. The shroud will double as a dust exclusion measure and you can then move the cap to the upper tube.

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I don't think collimation is ever an issue to consider if buying a newt. you have to do it almost every time to get the best from your scope anyway. the more you do it the less you have to adjust each time and the better you get at it.

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A truss also allows the optics and tube to cool to ambient far faster than a tube. This helps alleviate the poor seeing caused by the heat haze off the primary.

That being said, a cooling fan helps reduce this difference.

Mark

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My Rev. 12" (solid tube) just goes diagonally in my Xsara Picasso with the seats flat. It's also quite a handful to manhandle. Measurre carefully!

That said, if you have the space, it's like night & day over the 8" I had before it.

I agree with the others that there's really no point to a truss below 12". I would suggest it's "flavour of the month" syndrome.

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