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Truss Tube Dobsonian Telescope

beginner dob
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#1 hal9000a

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Posted 13 August 2019 - 11:43 AM

Hi 

i'm doing a commeback after 20 year laugh.gif 

and starting to look for a Dobsonian

 

just to be sure to understand Truss Tube Dobsonian Telescope

if there is little light where you use it wont be a good choice

 

Thanks


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#2 OleCuss

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Posted 13 August 2019 - 11:51 AM

You can get a shroud and then ambient light will be no worse than if you had a regular closed-tube Dobsonian.

 

The Truss-tubes take a greater time commitment for getting them set up and that can decrease your use (and therefore observing).

 

As the owner of a 12" Truss-tube Dobsonian, I'd only get another if it were required in order to be able to transport the thing.

 

I also have a 20" mirror I may someday build out.  That would definitely be a truss-tube as transporting a closed-tube even in the backyard would be too much of a pain.


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#3 jayrome

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Posted 13 August 2019 - 11:52 AM

Hi hal9000a, welcome aboard!

I'm replying to your post because I was recently in a very similar situation, in that I was into astronomy and had a scope as a kid, and this spring, 30-some years later, I got back into the hobby with the purchase of a Meade 10" Lightbridge truss-tube dob.

Now I can tell you with some certainty, you don't have to worry too too much about light-scatter down into the tube affecting your views. Let me explain. I have 2 spots that I bring the scope out to. One is Class 4 and the other is Class 2 Bortle. Needless to say, under good, dark conditions, you really don't have to worry at all about it. Even from my own backyard under Bortle 8 sky, it's not a problem. That being said, I did recently (with the help of my mother who's sewing skills are well beyond mine) make a DIY light-shroud for my scope. I have yet to test it.

 

Back to truss-tube dobs, I think your mileage will vary, depending on the scope  you plan to get. I do believe with some, if the tube is open all the way to the bottom then it may be more of an issue. Just get a light-shroud if you'll be doing observing from less-dark skies.

 

cheers!



#4 Kyphoron

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Posted 13 August 2019 - 11:52 AM

Not true, If its a shrouded truss tube it will function as well as a solid tube dobsonian. My avatar shows my shrouded 16" that is perfect even under light polluted within reason that is. 



#5 hal9000a

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Posted 13 August 2019 - 11:58 AM

Thanks all 



#6 Jeff Struve

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Posted 13 August 2019 - 12:10 PM

My Orion 12XXi truss dob was my first real scope... I not only still have it, but it is my favorite scope to use when I am doing visual astronomy.

 

It packs up well and is easy to transport, set up, and tear down. From in it's cases in the car to set up, collimated, and aligned. about 10 minutes.

 

At my last Messier Marathon I was able tot use it with just a 21mm eyepiece and found 107 of the 110 objects plus another 11 objects in a single night.

 

As mentioned, the shroud can help if it's really light polluted, but even without it, I don't usually have an issue. Where it helps more is if set up during the day or when doing solar to keep folks from looking into the mirror...

 

I thought about maybe getting a larger dob at one time, but even with a 14" you need a step stool or more to reach the eyepiece...

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#7 Chesterguy1

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Posted 13 August 2019 - 12:32 PM

Mostly out of laziness I have been using my 15" truss tube without the shroud recently. Often there isn't enough raking light where I worry about it, but there are two other advantages to the shroud not mentioned. One, is that there is at least a minimal barrier from one's body heat influencing the air column. Two, and to me this shouldn't be devalued, it prevents stuff from accidentally falling onto the mirror from the sides--especially as the scope is pointed closer to the zenith. Sometimes gravity is not our friend.

 

Chesterguy


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#8 Napp

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Posted 13 August 2019 - 12:49 PM

Truss tubes work fine.  The shroud keeps out the light but also helps keep out dust and other stuff suspended in the air.  I have a 16 inch and it’s actually very easy to setup.  If you are buying a 10 inch or less then a solid tube is easier to handle.  Above 10 inches and a solid tube becomes a beast.  The heaviest part of my 16 inch is of course the mirror box but it weighs less than 60 lbs.  Of course if you are just going to move the scope out of the garage a few feet just install rollers or wheelbarrow handles and you can leave the scope assembled.


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#9 George N

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Posted 14 August 2019 - 09:28 AM

…….t there are two other advantages to the shroud not mentioned. One, is that there is at least a minimal barrier from one's body heat influencing the air column. Two, and to me this shouldn't be devalued, it prevents stuff from accidentally falling onto the mirror from the sides--especially as the scope is pointed closer to the zenith. Sometimes gravity is not our friend.

 

Chesterguy

Those two are the main reasons I always use a shroud on my Obsession 20. If it is windy enough the scope blows around - it's probably too windy to observe - however, I have moved the shroud to cover only half the open tube in windy conditions.




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