Pros & cons for dobsonian

[daaveyboy]

I am looking at getting a 10" dobsonian but unsure what the pros & cons for a flex or a solid tube body.

10" & above seem to go down the flex body style and under 10" seem to have a solid body.

Is there any good & bad points I should be looking for?

[Chris Hopson]

Hi daaveyboy,

I had a skywatcher 8" flextube, it was very good. I bought a jacket for it, to stop stray light getting in. ( You don't need one with a solid tube which is a plus). I had limited space and money, hence the collapsible dob. I would imagine a large dob that could collapse, would travel in smaller cars.

I like the look of the Explore Scientific dob.

Chris

[laudropb]

The solid tube Dob will be quicker to set up and will require less collimating. On the other hand, if you are thinking of using a remote dark sky site then the flexi tube will be easier to transport.

[Gazabone]

I think it does come down to transportability. My own Dob is a 10" solid tube. I think I could handle a 12" solid but I'm not 100% sure about getting it in the car though I think I would have to put the back seats down rather than laying the tube across them.

One observatory I belong to has recently bought a 16" flex and that is a 2 man operation to set up and I think would be very difficult to handle as a solid.

Personally I think the downside to flex is the likelihood that it will need collomation every time you assemble it but the views will be worth the effort though.

[Dom1961]

Flex also cools faster

[faulksy]

i get my solid tube dob in the back of my car easy,

[Charic]

My 8" takes up about 52cm of floor space, that's not much more than a kitchen chair for me, and the scope is fully assembled all the time, securely covered to protect from airborne contaminants and ready to go, parked  near the door! I`' not sure the Skyliner 10" takes  much more space if any?

I had considered the 12" as my next upgrade, before considering the 10" due to the faster focal ratio that the 10" has,  possibly requiring more premium type eyepiece selections ( I want to keep what I already have ). This f/6 scope is pretty easy on eyepieces, and my eyes are rewarded with some stunning views, under the right conditions, considering the age of my eyes, and their far from perfect, impaired vision!

I don't like the idea of the  truss tube design either, I`d be too tempted to reach in more often, cleaning , dusting,  even  when stored in the collapsed position, I feel that I would always need to check collimation prior to use.

I rarely check collimation on my scope, as its handled with extreme care, and when I do check ( on a Star ) all seems fine and dandy.

An open tube requires a jacket to prevent stray light from entering, or dew hitting the primary mirror. 

As you say, classic solid tubes are getting harder to find over 8", The f/6 Skyliner is a sound starter investment into astronomy, and the scope may last longer than you think, due to its capability under the right conditions ( same for any scope, dark skies and good seeing )

Enjoy your foray into astronomy.

[John]

Optically they are exactly the same of course.

You will probably need a light shroud for the Flextube design to keep dew, dust and stray light off the primary mirror. It also keeps body heat out of the light path on cold nights.

The Flextube versions actually weigh a little more than the solid tube of the same aperture. I can see the advantages of the collapsable Flextube design for transport and storage.

In apertures of 10" and below I suspect you would be happy with either design.

[bomberbaz]

I had a 12" dob (solid), my wife hated it. She referred to it as the human cannonball  . Additionally it was hard to transport so it didn't last long.

The 12" dob however fold down and sits quietly in the same room and never gets a mention. It is pretty easy for me to move around, fitting easliy along the back seats of my car and collimation is no big deal. I do beleive they cool quicker too as mentioned.

So if you are thinking about regular-ish viewing away from the home and space is an issue, the flextube is a strong contender.

If you have a dark garden to view from with little need to transport, then maybe the solid tube version.

Ok one other thing, how big is your car, thats also something to consider.

Steve

[ollypenrice]

Although I don't move it around my 20 inch truss Dob holds collimation incredibly well. If you are shifting a big Newt around I think it would need some collimating whatever construction it was. I find a laser collimation takes no more than two minutes and is perfectly good enough for most occasions.

Olly

[Dave In Vermont]

If you're like me, collimation is no longer a word that send shivers up your spine. It's a fast & easy job with my laser - 3 minutes tops. If you're just starting out with collimation, I can understand the anxiety it may still generate. But once you have it down to something as difficult as brushing your teeth - a flex-tube Dob should be good-to-go if you want one.

Enjoy -

Dave

[Owmuchonomy]

The evidence I can present is that my 12" flex tube doesn't need frequent collimation.  I would estimate it needs tweaking every five excursions.  It is on the limit of a one man operation though to move the base around especially if you have standard doorways to negotiate.

[estwing]

go for the biggest you can handle...

[RikM]

At 10" there is not whole lot of difference other than the flex tube plus lightshroud is almost 1.5x the cost of a solid tube. 12" and up is where the flex tube or a truss design makes sense.

[bomberbaz]

At 10" there is not whole lot of difference other than the flex tube plus lightshroud is almost 1.5x the cost of a solid tube. 12" and up is where the flex tube or a truss design makes sense.

au contraire Rik, There can be many differences. For one it depends upon storage of the OTA, size of car if transporting and indeed the stature of the person using it. There will be others but those 3 spring to mind.

Steve 

[daaveyboy]

Many thanks to all who replied to my post, it looks like a truss might be the way to go as I will eventually want to go to darker places and transporting it could be an issue.

possibly a 10" with a goto or a 12" without a goto not sure yet,is a goto a benefit for a novice? 

[baggywrinkle]

I have the 12'' SW Flextube.

Easy to store at home but the OTA is a heavy piece of kit to lift. Not ideal for getting in and out of cars, OK for taking out into the garden.

Otherwise a great 'scope. Mine is the GOTO and it is easy to set up and once set up aquires targets very easily within a 24mm ep as a starter.

[Moonshane]

My take is this. 

Collimation - both will need collimating so it's neither a pro or a con although the secondary collimation is made easier in the flextube via the ability to cover the primary.

Weight - both are quite heavy so neither a pro or a con - the flex tube is a bit heavier

Both cool reasonably quickly but the flextube might cool a bit quicker - just observe straight away on low power and wait for the scope to acclimatise before upping the power to seeing limits

The flextube will be less tall and obvious in a room (other half may or may not be happy with that).

The flextube is shorter when folded so may fit in a car more easily.

I think the flextubes are a little more expensive? Also the flextubes are black and solid tubes white if this makes a difference - I like white scopes.

Both will be fab scopes and perform at about the same quality. You cannot go wrong really.

[Moonshane]

if you look carefully, you might be able to spot my three dobs (all solid tubes) in my office. My wife doesn't know they are there half the time (ahem) honest.

[swamp thing]

I don't like the idea of the  truss tube design either, I`d be too tempted to reach in more often, cleaning , dusting,  even  when stored in the collapsed position, I feel that I would always need to check collimation prior to use.

I rarely check collimation on my scope, as its handled with extreme care, and when I do check ( on a Star ) all seems fine and dandy.

If you are looking to upgrade to a 12" scope in the future, you will have to get used to checking collimation every time the scope is moved regardless of whether it has a flex or solid tube. It's nearly always the weight of the primary that necessitates adjusting collimation rather than the tube type. 

A 12" scope should be checked every time its moved, and adjusted if necessary for the best performance. Its nothing to worry about buddy and you'll soon get used to it as part of your setting up routine. it's still quicker than polar aligning an EQ or setting up GOTO

As you've noticed an 8" scope rarely needs adjusting even when moved about in a car. This is because the primary is lightweight compared to bigger aperture scopes. 

To the OP I would agree with Estwing. get the biggest scope you can manage/afford.

[Paul73]

Collimation is a non issue. Even the secondary can be tweaked in minutes once you get the hang of it (and that hardly ever needs changing).

FlexTube is great for storage and transport.

Paul

[John]

if you look carefully, you might be able to spot my three dobs (all solid tubes) in my office. My wife doesn't know they are there half the time (ahem) honest.

I give up Shane, where are they ?

Another thing to remember about the Flextube is that it looks like R2D2 when it's collapsed:

[Charic]

if you look carefully, you might be able to spot my three dobs (all solid tubes) in my office. My wife doesn't know they are there half the time (ahem) honest.

I wish my office was as clean,  and as spacious.

[Moonshane]

so do I 

that was on a day that my wife 'suggested' I might tidy the disgraceful room up. I am fast re-approaching the most recent episode in that particular cycle.