Unpacking the main Optical Tube Assembly

Unpack the OTAJust look at the size of this thing in its box! I included my hand in the photo to give an indication of scale, but as you will see from the photos lower down this page, it is quite a large telescope.

Main OTAMy XT10i shown here is quite something itself, but the next size up in the Skyquest XT telescope range is the XT12, with a full 12 inches of aperture, that must be a real beast.









Putting the Tube on the Base

Grasp the tube firmly, and get a feel for its weight, then carefully lift the scope tube and gently place it into the Dobsonian base so that the Altitude Bearings on either side of the tube rest on the Bearing Cylinders.

As you do this make sure that the tube and bearing sides do not get hung up on the Vertical Bumper Stop, or the CorrecTension pads as you lower it into position. Be careful when placing the tube on the bearings, because if it is inserted at the wrong angle the hub can strike the Encoder Board and possibly damage it.

You will soon get the hang of it.

Personally I have my own preferred technique of picking up the OTA and putting it onto the base:-

Grasp the top of the Scope tubeWith the OTA standing vertically on the floor (and the OTA dust cover lid removed), I stand next to it on the Eyepiece Holder side of the scope, and put my left hand over the top edge of the tube in line with the Finder Scope mounting bracket, and grasp the edge firmly.


Tilt OTA tube over to grasp the bottomNext I tilt the tube over slightly, so as to create a gap under the front bottom edge of the Primary Mirror Cell. This is so that I can put my right hand underneath to grip the bottom end.







Lifting the Telescope tubeLeft: Here I am doing my strong man act (I'm standing a bit strange simply because I was trying to keep my head in the photo, not because the tube is that heavy!). At the same time I bend down slightly and put my right hand under the bottom edge, grasp firmly, then adjusting my balance and taking the weight with both arms, I lift the OTA tube. Using both hands to share the weight of the scope is not too bad.

The XT10 tube weighs nearly 29lbs, and the Dobsonian base weighs a little more than 26lbs.

Like this, I feel that I have a better grip on the tube and that I am more able to lift and position it over the Dobsonian base than by using the method shown in the Instruction Manual, which suggests you stand behind the tube, and apply pressure with both hands on either side of the tube, then lift upwards. I think that way makes it more awkward if you need to carry the tube any distance, e.g. from indoors to outdoors.

Lifting it with my method places the tube across my body at waist height, with my arms naturally pulling the weight against me, which is easier to walk with than if you hold the tube "dangling" in front of you because you then have to hold your arms out more, which puts the tube in the way of your legs as you walk.


Placing the tube on the baseNext I approach the Dobsonian Base, and gently place my left foot (toe) against the edge of the Top Baseplate, so as to prevent it rotating as I lower the tube down into place on the bearings.

As I do this I concentrate on placing the side further away from me into position next to the Altitude Sensor Encoder Board, and then I know as I lower it, everything will slot into position nicely.

Perhaps you should adopt the method shown in the manual initially while carrying it short distances, and getting used to the way the OTA fits onto the base or even if you have back problems, but otherwise I think you will soon start lifting the scope in the way I have described.







Tube on BaseOnce it is mounted on the bearing cylinders, the tube should pivot freely up and down with gentle hand pressure, but it is not yet secure or properly balanced, since neither an Eyepiece, or the Finder Scope are in place yet, and the CorrecTension system has not be done up yet.

CorrecTension KnobsIn the right hand photo, left hand side, you can see the CorrecTension Knobs, with one metal washer, one white nylon washer, and a black nylon retaining knob spacer. The Black Spacer is only used if you have not got the IntelliScope Altitude Sensor installed.







Tensioning Knob WashersTake one of the knobs, and put the Metal Washer on it first, followed by the White Nylon Washer, which has to be threaded on. This is a sufficiently tight fit to prevent the two washers falling off the knob and getting lost. This knob will be known as the Tensioning Knob, and it will always be screwed into the "viewing" side of the telescope.

Tensioning KnobDo it up until the white CorrecTension Pads on the interior surface of the side panel just touch the side of the altitude bearing on the OTA.







Retaining KnobTake the second knob. If you have purchased and installed the IntelliScope Altitude Sensor Encoder Board, then you can immediately screw in the second knob. If not, then place the Black Spacer onto the knob before screwing it into the side panel. This knob will always go into the opposite side panel. This second knob will known as the Retaining Knob, and it should be fully tightened to prevent slippage of the encoder Magnetic Disc in relation to the telescope tube, as otherwise the sensor will give false readings.







CorrecTension SystemThe CorrecTension system is now installed, and the OTA is safe and cannot be dislodged from the base. To remove the OTA from the base for carrying to a new location, simply undo both knobs completely, together with their washers (and spacer if fitted).

When not in use ALWAYS make sure to screw the knobs back into the OTA bearing hubs so none of the parts get lost.










Adjusting the Vertical Stop

Handle BoltsHere you can see the Vertical Stop Knob which the bottom end of the telescope tube butts up against when vertical.

The intention of the Vertical Stop Knob is to ensure the tube is exactly 90 degrees from horizontal as taken from the horizontal surface of the Top Baseplate, and this fact is used during the first step of alignment for the IntelliScope Computer Object Locator.

In order for the IntelliScope system to work accurately, the Vertical Stop must be precisely adjusted so that the OTA is truly perpendicular to the azimuth axis of the base when the Computer tells you to "point the tube vertical".

Spirit Level on BaseThe IntelliScope COL instruction manual gives exact instructions for doing this, but basically you should work on a level floor surface, and then using a spirit level placed on the top of the Top Baseplate, rotate it through 360 degress to ensure the base itself is completely level. Reposition the base on the ground or use shims to make it so.

When level, put the Vertical Stop with all its supplied washers (a nylon spacer + 1/16" thick washer + 1/32" thick washer), onto the Vertical Stop Screw and thread it back into the base.

Rotate the telescope upwards in altitude until the mirror cell comes into contact with the Vertical Stop Knob.

Spirit Levl on TopNow place the spirit level across the top of the telescope and aligned in the same axis as the altitude movement. If it is completely level then the Vertical Stop is adjusted correctly, otherwise add or remove a washer until it becomes exactly level.






Once adjusted it should not need adjusting again. In normal day-to-day use of the telescope the base itself does not need to be level for the IntelliScope system to function properly; the base only needs levelling when intially setting the vertical stop.


Next section: Installing the Finder Scope

Other Topics in the Assembly section: