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Posts tagged ‘Dobsonian Telescope’

Telescope Tips: ” Why did it take so long for Dobsonian Telescopes to become popular?”

Today, Dobsonian Telescopes are as popular as any design of telescope on the market. Its not surprise why: They are easy to use, and they give the 3112biggest ‘bang for your buck’- the most aperture for your telescope dollar.

But it wasn’t always this way. Times were that using a Dobsonian telescope was something that only true hardcore amatuer astronomers did. Using a Dob was the equivelant of a computer gamer overclocking the chips on his computer – something most people just couldn’t do despite the benefits it may reap. So why was this the case?


Assembling the Orion SkyQuest XT8i Intelliscope Dobsonian Telescope – Part 1

A bit of a disclaimer here. This is going to be as much of ‘what’s wrong with the Intelliscope’s instructions as much as it will be a  ‘how to’ for helping set-up your Intelliscope.

005First a little background: Dobsonian telescopes, with their large mirrors and lazy-susan bases have been around for ages but it wasn’t until Orion released their SkyQuest XT line in the late 90’s that they became popular. Previous Dobsonian telescope models had issues with balance and were trick to keep on target.  Odd solutions like weights added to the outside of the telescope were clunky and awkward for basic users. Orion solved the issue by adding the CorrectTension system, which was a spring that held the optical tube of the Dobsonian to the base. It was a simple and elegant solution and it worked very well. The line got excellent marks and was considered one of the best Dobsonian lines on the market . At first Orion just sold a 6″ and 8″ model, then added a 10″ model, a 4.5″ kid’s model, and later a 12″ model.

For several years, Orion pretty much dominated the Dobsonian Market, but when imitators cropped up they decided to improve their classic Dobsonian by adding a computer guidance system (not a computer control system like many GoTo telescopes). Here you would get the advantages of having a computer system to help you find objects. It would not require batteries for any motors and the observer would be the person moving the telescope, using a hand controller to guide them.

The whole system using a pair of magnetic encoders, and development was tricky. The initial plan was to have the Intelliscope completely replace the original Dobsonian line where it would be sold with and without the controllers. This didn’t happen due to some development issues. Once the Intelliscope was ready it was sold both with and without the controllers, but after a few years it was sold strictly with the Intelliscope controller system. This unfortunately left some ‘development scars’  that will show up from time to time as we assemble the telescope. (more…)

Telescope Assembly Review: The Orion XT12G GoTo Dobsonian!

We were almost going to list this under ‘Telescope tips’, but it really isn’t a tip so much as a review and examination of the process of putting a Dobsonian telescope together.

Now we don’t normally stock the Orion XTG Goto Dobsonians, they tend to take up a lot of space and shipping costs can get very high very fast. But we do get special orders and this customer wanted us to put the telescope together for them (a service we offer for a fee). So this was an opportunity to show the process of putting one of these things together.

Of course, this customer bought the biggest bear of the series: the XT12G


This arrives in three boxes: One for the tube, one for the base, and one for the mirror. The XT10G and XT8G versions need only two boxes as they come with the mirror cell already installed.

The instructions have you put the base together first, but we wanted to get the mirror stuff out of the way first so we fished out the tube from its humongous box:

We also opened the mirror cell box:

We took of the wrappings (and it was well wrapped: a plastic bag. foam, shrink wrapping and protective linen paper on the mirror surface!). Then we removed the cell from the telescope tube:

That part on top (which is actually the bottom of the tube) is what needs to come off.

The involves removing 6 screws and lifting the mirror cell from the optical tube. These were then placed on the worktable:

Now we start to sweat.

Here is where it gets fun: You have to put the mirror face down (on a clean, flat surface, we used the foam from the box and the protective paper that came with the mirror. Then you connect the mirror to the cells by attaching the adjustment knobs that are used in collimation. Once this is done you have an assembled mirror cell!


Now we have to get the mirror cell back onto the tube. This is not easy as the cell is heavy, and you have to line up the screw holes with each other or take it out and try again. You actually have to squeeze the tube a bit to get the cell properly on the tube.This means you have to play ‘huggy bear’ with your scope until it drop into place.  With any luck the screw holes line up and you screw the attachment screws  back into place.

Now, about that base. The XT12G is actually big enough that it not only has its parts but also a couple of braces on the sides. The XT8G and XT10G do not have these.  Anyway, here are the base parts disassembled:

Parts! Beautiful XT12G base parts!

Now, here is why I love the Orion Goto Dob series over their other models: See the base of the base? The Round part at the bottom? It comes assembled! This is probably because having the customer insert the motors, etc would be a lot to ask, but comparted to the basic XT Dobsonian clunky two-part assembly or the Intelliscope’s near nightmarish base assembly this is a breeze! Its like putting together IKEA furniture – although that isn’t automatically a good thing.

First up, we put the top parts together. Now I strongly suggest that you have a decent drill/driver with a phillips head screwdriver and hex-head bits for this job. Trust me, it will be very, very handy:

You need me!

The front piece attaches to the side pieces. When we first put this together we put the wrong side out (did I mention IKEA furniture?) fortunately, this was not a hard fix.

This is done with about a dozen wood screws with hex-heads. The smaller versions don’t use as many screws but they also don’t need the braces on the side.

This frame is then placed on top of the round base and the screw holes are lined up. About half of the attachment screws can be worked with the drill driver, the other half are a bit more difficult as you have to use the hand hex-wrench:

As annoying as this part is, I will take it any day over the method used with Orion’s other Dob lines. With those you must drive the screws up from the bottom of the top plate and into the upper base pieces. It is even more annoying than it sounds. This is simplicity itself by comparison, but it still can be a bit hard on your hands.After tis you attach the eyepiece rack and the handles. The XT12 has three handles since it is a big bear.

Done! (handles and rack came later)

Now it is time to place the optical tube on the base. This is tough as the tube is pretty bulky and heavy. The attachment method for this dob is to turn it sideways and place it in the base in a horizontal position. not easy as the other Orion models but not really that much harder, either.The tube attaches to the base with a screw that prevents it from ‘jumping’ or being pulled out by accident. We could get a shot of the tube being placed as it was just me putting this thing together:

Once assembled, the XT12G stands just about 5′ 10″ tall. I am about 6′ tall and my eyes were just looking over the top of the tube when it was standing upright. Like we said, it is a big bear.

After assembly, the optics must be collimated – both secondary and primary mirrors. Most telescopes come from the factory collimated already, but since we had to install the mirror it was very unlikely to be collimated from the start.

The control unit and other items were also not attached as this was going to be picked up by the customer.

In review: While the XT12G (or any 12″ non-trussed Dobsonian) are big and heavy, the XT12G actually assembles quite nicely.

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