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What advantages do Dobson Telescopes have?

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#1 wdretired

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Posted 28 November 2012 - 12:25 PM

What advantages do Dobson telescopes have (if any)? Are they a good choice for astrophotography?

#2 Maverick199

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Posted 28 November 2012 - 12:29 PM

Advantages of a Dobsonian:-

1. Best bang for buck per inch of aperture.
2. Easy to use. ( though bigger the dob, more strenuous the exercise ).
3. Light gathering bucket.

Astrophotography is almost out of the question unless you want one mounted on a heavy eq platform with a modified low profile focuser.

#3 newtoskies

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Posted 28 November 2012 - 12:32 PM

I don't have a refractor (yet) but can tell you that you do get more bang for the buck with a Dob. I only have a 6" and have seen and learned a lot. A dob will teach you a lot about astronomy. You will learn the stars, star hoping, see DSO objects better and clearer. next to no set up time other than collimating and aclimating.

#4 RTLR 12

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Posted 28 November 2012 - 12:40 PM

next to no set up time other than collimating and aclimating.


??????????????????

#5 csrlice12

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Posted 28 November 2012 - 12:42 PM

You'll never get the views in a refractor that you will get from a big Dob; why do you think big Dobs use refractors for finderscopes?????

But for AP, go the refractor route; unless your last name is Buffet or Trump....

#6 newtoskies

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Posted 28 November 2012 - 12:45 PM

next to no set up time other than collimating and aclimating.



??????????????????



Was meant that you don't have to polar align etc as with an EQ mount. Hey, I'm still learning :smirk:

#7 CosmoSat

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Posted 28 November 2012 - 12:58 PM

What advantages do Dobson telescopes have (if any)? Are they a good choice for astrophotography?


By dobsonian telescope..u mean the alt/az mounting..right?? Well..it was designed to be used specifically for visual...very stable..easy to setup and use.

And if u mean the newtonian scopes which are usually used on the dobsonian mounts...newts sure are used for astrophotography..

Clear skies!

#8 YetAnotherHobby

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Posted 28 November 2012 - 01:03 PM

What others have said - you get the most aperture for your dollar.
They are stone-simple to setup and use - point and shoot.
No computer to align, no batteries required, no software - just the way Newton intended.
As the aperture goes up they get heavy and awkward, but ANY scope 12" and above is going to give you a workout.
There are disadvantages - the lack of tracking means you can't take long exposure pictures. Snapshots of the moon, no problem, but you won't be doing astrophotography. The lack of tracking could be considered a disadvantage if you wanted to study an object in detail at high magnification. The constant nudge-nudge of the tube to keep the object in view can be distracting.
These telescopes typically have a "fast" focal ratio - f5 or lower. That means that some inexpensive eyepieces can leave the edges of the view slightly distorted. I've never noticed the issue, but then I am usually focused on the object in the center.
Some people object to the fact that the eyepiece position varies quite a bit depending on the location of the object you are viewing. If you are near the horizon, you will be on your knees. Near Zenith some height-challenged individuals might need a ladder. And when you are very close to zenith dobs are hard to point (google "dobson's hole").
So they aren't perfect for every astronomer, but they are very hard to beat.

#9 Thomas Karpf

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Posted 28 November 2012 - 01:05 PM


next to no set up time other than collimating and acclimating.

??????????????????



Was meant that you don't have to polar align etc as with an EQ mount. Hey, I'm still learning :smirk:


As long as you're not using any electronics (go-to, push-to, cameras, etc.), a dob sets up quickly. If you're lazy or impatient (or haven't bounced the scope much since the last time you used it), you don't HAVE to collimate. If you don't mind 'wavy' views initially and have just brought your scope outside where it's cold, you don't HAVE to let the mirror acclimate.

Total setup time: a minute for solid tube scopes.

#10 TahoeNoob

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Posted 28 November 2012 - 01:17 PM

I don't have a refractor (yet) but can tell you that you do get more bang for the buck with a Dob.


What you don't know is that this, lucky, guy got a great (flea market) deal on a super nice refractor. 25 bucks, for a beautiful, high quality, classic... with awesome optics! :bow:

He's probably one of the few people that'll get more bang for the buck out of a refractor.

#11 Seldom

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Posted 28 November 2012 - 01:28 PM

Astrophotography is almost out of the question unless you want one mounted on a heavy eq platform with a modified low profile focuser.

How long an exposure can you expect from a dob on an equatorial platform?

#12 newtoskies

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Posted 28 November 2012 - 01:31 PM

That is a great deal, I don't have that luck...lol

#13 Mark Costello

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Posted 28 November 2012 - 02:02 PM

Hi wdretired.

"What advantages do Dobson telescopes have (if any)?"

To me the biggest advantage is the mount, inexpensive, sturdy and low slung with a low centroid for the entire rig. This has at least three payoffs. The first one it the "most bang for the buck." The second payoff is ease of setup. The third payoff is very good stability of the rig while it's in use.....

#14 Tony Flanders

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Posted 28 November 2012 - 03:18 PM

How long an exposure can you expect from a dob on an equatorial platform?


Depends how rigid the Dob is and how good the EQ platform is. In theory, it can work as well as any astrophoto rig. I know one person who specializes in long-exposure astrophotos with a Dob.

#15 wdretired

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Posted 28 November 2012 - 06:04 PM

Is there an advantage to having a goto Dob? I noticed they were a bit more expensive but except for mounting the camera, you wouldn't have to worry about keeping up with the target. I'm not worried about a little weight. I don't plan on going on a 25 mile hike with the thing anyway. Are you actually looking over the top of the telescope into the eye piece or are they moveable to the side?

#16 GOLGO13

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Posted 28 November 2012 - 06:22 PM

To me tracking the stars is the biggest downside of dobs. But an EQ platform or the new Orion goto scopes (or for those with expensive dobs they have other options) have changed that a bit.

But I find dobs really easy to use, quick to setup, and take up almost no space in the house. Simplicity is a good thing in my opinion. For the money they have huge capabilites.

#17 Achernar

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Posted 28 November 2012 - 06:56 PM

Dobs have a lot of advantages, but they also have drawbacks. The advantages are:

Maximum aperture for the buck.
When well made, the optics offer very high image quality.
Simple to set up and use.
No batteries need to operate.
Simple to maintain, very little to go wrong.
Stable mountings, yet allow for effortless tracking of objects when well made.
Can be equipped with digital setting circles and or equatorial platforms.
Easy to build yourself.
Portability, a 8-inch solid tube fits in any car, a 15-inch truss tube can fit in many cars when disassembled.
In a properly ventilated Dob, optics cool down more rapidly to ambient temperature than sealed telescopes.
No need for polar alignment.
Can be moved from spot to spot to get around obstacles blocking your view of an object.

The drawbacks are:

They are not suited to astrophotography, at least not without a lot of modifications.
They can be hard to use on objects near the zenith.
In larger apertures, they can be very tall, requring a ladder to reach the eyepiece.
Above 10-inches or so with a solid tube, and 16-inches with a truss tube, they are heavy and bulky and require a larger vehicle to transport. If that is not required, wheelbarrow handles or other means can be used to move the telescope around.
Optics are exposed to the air, requiring washing them when needed, and recoating every ten years or so.
Tracking at very high magnifications can be difficult.
Optics are subject to dewing, requiring heaters and a powersource.
Optics must be collimated for good views.
In faster focal ratios, coma becomes an problem but will be cured with a corrector lens.

Dobs are not made with photography in mind, there are far more suitable telescopes for that. But for visual observing, especially of dimmer deep sky objects, a Dob is an excellent choice. The smaller ones are good, grab and go telescopes for quick observing sessions.

Taras

#18 panhard

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Posted 28 November 2012 - 06:59 PM

I would say that Tarus summed it up nicely. :bow:

#19 Tony Flanders

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Posted 28 November 2012 - 07:14 PM

Is there an advantage to having a goto Dob? I noticed they were a bit more expensive but except for mounting the camera, you wouldn't have to worry about keeping up with the target.


Go To Dobs have two advantages: They track the sky and (of course) they find the objects for you, rather than requiring you to star-hop.

However, they are not suitable for long-exposure astrophotography. For that, you need an equatorial mount to avoid field rotation.

Are you actually looking over the top of the telescope into the eye piece or are they moveable to the side?


Big Dobs -- ones where you often need a ladder -- usually have the eyepiece mounted horizontally. Small and medium-sized Dobs usually have it mounted so that it points up at 45 degrees when the tube is horizontal.

Few Dobs allow you to rotate the eyepiece to different positions.

#20 panhard

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Posted 28 November 2012 - 07:49 PM

+1 :grin:

#21 Atl

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Posted 28 November 2012 - 09:31 PM

If you just want to play you can certainly photo the moon and planets. Here is an image from my dob at 100x with no tracking...not exactly art...but very cool.

Attached Files



#22 Atl

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Posted 28 November 2012 - 09:42 PM

And another...also no tracking. So dobs are not a lost cause for photography. Is it ideal? No, but we are not all out to be Damien Peach...lol...and it gives great views!

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#23 Mike4242

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Posted 28 November 2012 - 10:14 PM

Great shots! :waytogo:

#24 kfiscus

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Posted 28 November 2012 - 10:16 PM

Nothing impresses at an outreach like a good-size dob. To the general public, even a 6" dob looks huge. My 10" and 12" are well received by the unwashed masses.

#25 GOLGO13

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Posted 28 November 2012 - 10:24 PM

Kfiscus,

It's funny you say that about the size of the dobs being impressive. When I got my 10 inch dob I thought...holy moley this is big. Then I went to a site with a 30 inch dob, and my friend has a 16 inch dob. Now I look at my 10 inch and think, it's kinda medium to small sized. :lol:






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