Truss and Flex tubes

[bomberbaz]

Not that I am in the market for one just yet.. My understanding of these adaptive, portable pieces of equipment is that one of the key aims of them is to fold down into neat and tidy blobs (for want of a better word) so they can be stored away without taking up (depending on size of the aperture) the area of a chair to a good portion of your living room.

http://www.optical-systems.co.uk/meade-lightbridge-trusstype-dobsonian-p-6156.html?currency=GBP&language=gb

http://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-200p-flextube-goto.html

http://www.rothervalleyoptics.co.uk/meade-lightbridge-truss-dob-deluxe_d1388.html

I have only been able to find the folded down specs for the 130p (which in all fairness is tiny in comparison to 95% of all scopes anyway), so why have the marketing guys not seized upon this particular selling point of these adaptive scopes. Before I bought my 8SE I was seriously looking at these and it was only a 2nd hand opportunity that stopped me getting one.

Eventually my aim is to sell my portable 102 goto Mak and up it to a larger apertured scope like the ones I listed above. It will go in the back of my car like the 102 one does http://stargazerslounge.com/topic/183007-scope-carry-case-mod/ so I can observe at a minutes notice when I find myself in the right place at the right time. (My job involves a lot of travelling) This happens a lot believe me.

So again the question, why are the folded down figures not more easily available? It is imho one of the main selling points.............

[Qualia]

I imagine truss dobs are more expensive than solid tube because they're more complex instruments. They will have to be built quite carefully to avoid problems with balancing and collimation every time one sets up, for example. And even if this is well done, you may have to be checking and rechecking colllimation a couple of times in an evening. If this is so, many first time buyers of dobs will more often be directed to a solid tube due to its relative simplicity in set up and lesser cost.

Adding to this factor, I also imagine a truss dob is primarily about travelling but a great many folk will start viewing from their gardens, so transport won't be such an issue. If they have a garden, they will more than likely have a house where storage won't be such an issue, so it seems to make sense that solid tubes will be more popular in the market. As there will be more demand between the respective companies for tubes, this should - in theory - also help drive down costs a little - assuming their isn't a pact or oligopoly in place.

On a side note which isn't exactly related to the OP's question, I have a 10" truss dob and it is truly a fantastic instrument. Set up is conducted in about 15 minutes in the dark and collimation of the primary is really just a tweak of the screws which I do with a cheshire and a red light. I do not own a car, but via public transport I can still get my telescope out to some really exceptional skies (last light I could see with my naked eye 7mag stars!!). This ease of use and transport would just be impossible with a tube design.

So, from where I'm sitting - and I may have this completely wrong - it seems an issue of transportability. If you can wheel or carry a solid tube to your observing location at home, then I can't see much sense in buying a truss. But if you want to take a 10" or bigger out to some really cool dark sites, a truss is the way to go.

[bomberbaz]

All very interesting and valid stuff qualia but I think you may have missed my main point and that is, why are the specifications for the set up and folded down sizes not more easily available? You would think that, (and I note you raised the issue of portability) the manufacturers would make this point of ease of getting the things around easily a bigger selling point!!!!

[crashtestdummy]

If you do a site search for skywatcher flextube dimensions there have been a few threads about this.my 12" is 144cm extended and i think its 95cm closed.i have no collimation problems but it does need doing every observing session if you take it in the car,not as much if stored upright between sessions at home

[Andy_E]

Always thought it was a shame the 10" doesn't come in a similar focal length to the 12"; at 1200mm f4.7 it's just too demanding on EPs for me... surely an f6 1500mm would be more attractive? Given that most manufacturers make a truss 10" version, I can't understand why this isn't available as it would still fold down to a convenient size. Sorry perhaps not the most relevant of replies, it just annoys me that we get stuck with the non truss specs on 10" scopes... assumedly due to keeping manufacturing costs down?