Solid tube or truss

[Mike73]

Think I'm swaying towards a truss now. -

But which truss? There isn't too much choice in Europe. :-/

[Daniel-K]

I have the 14" skywatcher flexi tube and the only thing I dislike is the base its a royal pain in the hoop. Even though it brakes down into 4 parts I wish they would for once make a square base! Other than that I love mine

[Scooot]

But which truss? There isn't too much choice in Europe. :-/

Don't know, but it's not imminent so I'll take my time deciding.

[russ.will]

John,

Not in our climes. Body heat wouldn't affect an open truss as much the residual heat of a closed tube. Once temps get down in the minus 20 C, maybe. Well, anything at that point.

Cheers

Ian

When finessing collimation on a defocused star, I find it quite easy to see breath currents that I don't recall seeing in my old (shrouded) FlexTube. game of nthsBut I certainly can't recall seeing anything resulting from body heat.

That said and as this is a game of nths of a dgeree - I do wish ES had fitted the focuser on the other side of the scope, so that when viewing objects that are predominantly in the south, I'd be standing on the east and therefore downwind in the prevailing wind directions of the UK. I suspect it would make no difference, as you say, but it wouldn't be the first change made for peace of mind, rather than due to empirical evidence - Sort of like clicking on the 1/10th wave option as it's only £60 more than the already-better-than-my-eyes 1/6th wave standard optics!

Russell

[russ.will]

But which truss? There isn't too much choice in Europe. :-/

There's a lot more than there used to be and the list is growing.

ES with SW to follow.

David Luckhurst

Summerian Optics

A couple of Polish blokes

Others that I fail to remember.

Indeed full truss Dobs (I'm discounting the LBs & FTs as more a lip service to the idea) have never been cheaper and can still be as expensive as you could want, especially considering the quality of mirror makers we have within these shores to equip a bare bones purchase.

Happy Days.

Russell

[Scooot]

I was reading Olly's link on the serrurier truss design and I've also been browsing at the obsession website. They describe their scopes as serrurier truss designed but I don't see the bit in the middle that bends to help with the gravity. Or is it the fact that both mirrors are attached to the end of the tubes. I'm sure I'm missing something, and have no engineering skills, but just wondered.

[Moonshane]

technically, I think that most scopes whilst based on the serrurier truss design are not technically true to it. the most common truss systems (i.e. those used by 'normal' astronomers (term used advisedly ) not those by professional large obs instruments) replace the primary end truss system with a box, having trusses only from the point of rotation upwards to the UTA rather than also downwards to the primary. the idea is the same though of course - one set of tubes in compression on one side, matched by a set on the other side in tension which equalise each other and give good strength and stability (assuming certain proportions).

[Beulah]

I have the 14" skywatcher flexi tube and the only thing I dislike is the base its a royal pain in the hoop. Even though it brakes down into 4 parts I wish they would for once make a square base! Other than that I love mine

With my SW Dob, I removed the 'semi' circular bits with a bandsaw and made the base true with the rocker box. As a result I can move the steps nearer to the EP. (Focuser height is 5ft 11)

The box itself was reinforced with some tough corner brackets and the bare chip board edges were treated to a few coats of  black paint to seal them. I could have replaced the rubber edging that was attached to the circumference of the base but didn't have appropriate adhesive to hand (didn't feel like mixing a few tubes of 2 part epoxy!).

It's been around ten months, the scope has been shifted about a fair bit and the mount is still sturdy, plus the bonus of getting it to fit through doors!!

[scarp15]

One aspect that I have been very impressed with since I have owned the OOUK VX14  dob, is how well it holds its collimation. I know that this isn't necessarily a decision making factor, yet I only use mine traveling to dark sites such as last night - though a mostly cloudy affair (typical unreliable forecast) . I check the collimation prior to setting off and first thing on arrival and it is either spot on perfect or very close. As I said previously, it travels stably supported and locked into foam blocks additionally cushioned with camping mats.

If intended use is mainly from home and finance not too much of a concern, then a bigger version of the scope you already have / are familiar with, such as VX14 or VX16 would be a consideration perhaps. Certainly with the VX14 (I am just under 5'11") and I would expect with the F4, 16" there are no issues in requiring a step for observing (unless you choose to place it onto an equatorial platform in which a short step may be required . 

[John]

One aspect that I have been very impressed with since I have owned the OOUK VX14  dob, is how well it holds its collimation. I know that this isn't necessarily a decision making factor, yet I only use mine traveling to dark sites such as last night - though a mostly cloudy affair (typical unreliable forecast) . I check the collimation prior to setting off and first thing on arrival and it is either spot on perfect or very close. As I said previously, it travels stably supported and locked into foam blocks additionally cushioned with camping mats.....

As I posted earlier, my OO is very good in this respect too.

I think the design, construction and operation of the mirror cells in a newtonian is vitally important to it's overall performance. There have been a few after market mirror cells offered by suppliers such as First Light Optics in the past but they never seem to get much attention whereas folks seem to change their focusers in the blink of an eye.

Collimation screws do seem to get upgraded though and primary collimation springs, which some manufacturers still seem to make too weak to support the primary - what would the cost be of fixing that little "quirk" during manufacture ?

[Scooot]

I have been browsing and also reading about OOUK's 20", but starting to get very pricey. I would need a small step for this sometimes, ( I'm 5'9" ). I was wondering whether the semi-truss design was better than say a David Lukehurst type truss design from a dew viewpoint. Can't find any reviews on the OO one. Also with the OO 20" I'd have to find out what the clearance is below the tube so I could fit the azimuth encoder for my Nexus.

[scarp15]

The mirror cell on my 12" Meade Lightbridge was built from quite thin metal. I'm sure the elements of the cell used to flex as I moved the scope around. Using the locking screws certainly caused it to flex so I didn't use those.

The cell on my 12" Orion Optics is much more sturdy despite being a simpler design. When I bought the scope the 60 miles or so to the SGL star party this year it was laying on it's side in the back of the car and I must have hit dozens of pot holes during the journey, and then there are the speed ramps on the entry road to the camp site, but when I put the tube on the mount the collimation was still spot on. Hats off to Orion Optics for that design   

Ah right good point John, just re-read the thread and confirms my own experience. 

In terms of dew I have yet to experience a problem regarding the mirrors and do not even have a dew shield for this scope, which I found to be e necessity on numerous occasions to fit a dew shield (which subsequently effected balance) with my former flextube.

[faulksy]

same here as scarp, i love the vx 14 and it travels so well, when ever i take it to a dark site i obviously check colimation but rarely needs adjusting, very good scopes

[Gina]

This thread is very interesting   I am considering getting into observing in addition to imaging and looking at the options.  Like everyone, I would like a nice big Dob and these tend to use truss build.  I'm not sure yet what I will be able to afford and I will be looking at as much DIY as possible to cut costs.  I like DIY anyway  

I think I should start my own thread rather than post more here as I'm liable to go off-topic.

[astronymonkey]

Id use a truss for anything of 12 inches and above due to storage , transport and weight issues (as the individual parts are lighter than a whole tube).

A 16 inch tube is large in any format but being able to break it down can be an advantage, and whatever you do you will end up tinkering anyway - so for me its not an issue if I have to spend 2 mins on collimation , is just part of the routine.

my LB has travelled with me on quite a few occasions and its a joy to be able to fit it in the car on my own.

as for dew, I use a dew heater for the secondary but prevent it on the primary by using a shroud and tilting the scope downwards when not in use. I have mini hairdryer if needed but ive never had to use it.

cheers

[quaoar]

https://sites.google.com/site/thedobsonfactory3/home

Has anyone over there checked this guy out?.

[Moonshane]

https://sites.google.com/site/thedobsonfactory3/home

Has anyone over there checked this guy out?.

very nice but not cheap (understandably!)

[quaoar]

I was just thinking along the lines that if I had access to one of these scopes I could replicate a lot of its structural components myself. If you were going to build your own scope anyway you could use the original as a template and save a lot of reinventing the wheel. Later you could sell the original. If 4 or 5 people who wanted say a 20" could pool their cash and work together...... well you get my drift. Just thinking out loud.

[faulksy]

I was just thinking along the lines that if I had access to one of these scopes I could replicate a lot of its structural components myself. If you were going to build your own scope anyway you could use the original as a template and save a lot of reinventing the wheel. Later you could sell the original. If 4 or 5 people who wanted say a 20" could pool their cash and work together...... well you get my drift. Just thinking out loud.

good idea, you could even buy it without optics and that would be even cheaper then it could be sold on after using everything as a pattern

[Moonshane]

surely it would be better to just make one yourself? I'd be looking to pay no more than 60-70% of the cost of a new one for a used one so the losses might be substantial.

[Scooot]

https://sites.google.com/site/thedobsonfactory3/home

Has anyone over there checked this guy out?.

They do look very desirable.

[TheMightyKong]

Dobson factory and skyvision make nice dobs in France.

[quaoar]

surely it would be better to just make one yourself? I'd be looking to pay no more than 60-70% of the cost of a new one for a used one so the losses might be substantial.

Sure you can build a "one off" by yourself from scratch but like I said you'll be reinventing the wheel the whole way. Still it is the cheapest way. The easiest way is to bite the bullet and pay someone who specialises in building telescopes to build it for you however this is the most expensive option. Another way is to buy secondhand like you said 60-70% of new.

I think it's probably a stretch for most DIY to build say a 20" from scratch. However looking at the Dobson factory one I reckon if you and a few similarly motivated chaps had one there in front of you .... Well who knows. What's a 30-40% loss divided 4 ways?.

[Moonshane]

I think I was being too subtle. To me it feels wrong to buy a product a then rip it off without permission. Personally I have no issue with diyers seeing my own build threads and copying the designs as 1) i never intended to make a living from it and 2) I got many of my design ideas from diy sites like Stellafane. Like their subscribers i hoped my efforts would inspire others to try.

I know the effort that goes into these scopes and what you suggest to save some money seems very wrong. Maybe you have approached them and they said they don't mind in which case I apologise in advance.

[quaoar]

I think I was being too subtle. To me it feels wrong to buy a product a then rip it off without permission. Personally I have no issue with diyers seeing my own build threads and copying the designs as 1) i never intended to make a living from it and 2) I got many of my design ideas from diy sites like Stellafane. Like their subscribers i hoped my efforts would inspire others to try.

I know the effort that goes into these scopes and what you suggest to save some money seems very wrong. Maybe you have approached them and they said they don't mind in which case I apologise in advance.

Subtlety is wasted on me I'm as thick as a whale omelette.

No you are right it is wrong (ish). I bought all my scopes with cash but not everyone who wants a big dob is as lucky as me. I myself can't be bothered with the DIY route because even with the scope right in front of me it's still a chore and my reproduction no matter how much effort I put into it would still be a pale imitation of the real thing. I don't believe any top shelf vendor would lie awake at night worrying about any threat I or any other DIYer would pose. Most of them can't keep up with the demand from people who can afford them ( I waited 2 1/2 years for my Webster ). I would point out that in the scenario described above the vendor would be getting a sale that they otherwise wouldn't have got. Dave Kriege of Obsession Telescopes wrote a book for anyone to buy that screams "this is how I build my scopes, build one yourself I'll even sell you the bits!". Webster on their site say " Hey if you want to build your own clone of our clone of Obsession we'll help you and we'll even sell you the bits!". Dennis at Dobstuff will build you just about anything you want. All I can say is if you feel it's wrong don't do it, or ring him up and ask, or hop on a train visit his workshop and wrangle a deal or just save your money and buy one. I'll shut up now and go polish my dob.