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Orion XT-12 Intelliscope;
Newtonian Reflector
on a
Dobsonian mount:
The Intelliscope Controller

The Orion Intelliscope family of Dobsonian telescopes consists of 6-, 8-, 10-, and 12-inch scopes.  They are exactly alike except for the size of the Optical Tube Assembly (OTA) with the 6-inch being the smallest and the 12-inch being the largest.  This article is my description of the operation of the Intelliscope controller.

How to find things in the sky

The main challenge facing an astronomer -- professional or amateur -- is finding things in the sky.  If you want to look at a certain star, nebula, globular cluster, planet, or what have you, how do you find it?  How do you know which of the zillion or so spots of light in the sky is the one you want to look at?

The sky

Complicating the problem of finding what you want to observe is the fact that it's all moving -- that is, the Earth revolves on its axis once every 24 hours and the Earth revolves around the Sun, making one circuit every 365 days.  Where an object is in the sky is determined by three elements:  rotation of the Earth around its axis; rotation of the Earth around the Sun, and, observer's location on Earth.

• Rotation of the Earth around its axis.  The stars and other objects in the universe are fixed in position -- they don't move (well, really they DO move, it's just that their motion is so slow and so complex in relation to each other and to us that they appear to be fixed).  As the Earth revolves on its axis, objects move into and out of view -- step outside one night and look for a bright star, mark where it is.  Then, step outside a couple of hours later and notice that the star is not where it was earlier.  Actually, the star has not moved -- you have -- the Earth has rotated through a few degrees around its axis and the star has appeared to move.  This is how the Sun moves across the sky from morning to night -- we rotate, the sun sits still.
• Rotation of the Earth around the Sun. As the Earth revolves around the Sun, our view of the universe changes.  That is, some objects are visible only in the winter, others in the summer, etc.  One of my favorite constellations is Orion, The Hunter.  Orion dominates the winter sky, usually appearing in early fall and remaining visible until early spring.  In the fall, Orion rises early in the morning, rising earlier and earlier each day until in the middle of winter Orion rises around sunset and is visible all night.
• Observer's location on Earth.  Another factor that determines where objects are in the sky is your location.  An observer standing in Alaska will see a star in one position while an observer on the Equator looking at the same star, same date, same time, will see the star in a different location because each observer is looking at the star from a different point.

Manually locating astronomical objects

The traditional, manual method of finding objects involves, "learning the sky," then using various observation aids, mainly a sky chart or a sky atlas.  We have all seen sky charts and some of us have seen sky atlases.  A sky chart shows a view of the night sky at a particular date and time and shows where the stars are at that date, time, and observing location.  Here's an example of a star chart that shows the positions of stars and constellations in winter as seen from the mid-latitudes of the Northern Hemisphere.

The constellation Orion is in the center of the southern sky, with its brightest stars, Betelgeuse and Rigel shining brightly.  Sirius, the Dog Star, is the brightest object in the night sky.  This chart is good for midnight, late December.  Two months earlier, this chart would be good but for earlier in the morning -- around 0400 -- because the Earth is moving around the Sun, causing the angle at which we see these objects to change.  If you look directly overhead at midnight, late December, you'll spot the bright star Capella.  Polaris -- the North Star -- is in the center of the northern sky.

Armed with a sky chart and a pair of binoculars, you can see a lot of objects in the sky.  Just compare the sky chart to the sky and refer to the chart to identify objects in the sky.  If you do this 3-4 days a week for a year, you will have gone a long way toward "learning the sky" -- you'll be able to pick out the major constellations, the bright stars, and other objects in the sky without the aid of a chart.

 A more sophisticated method of locating objects in the sky is "star-hopping."   This requires a fairly good knowledge of the sky and a sky atlas.  Here's how it works:

• Find a known object in your telescope.
• Consult your star chart and find the known object that's in the telescope field of view and the object you want to see.
• Consult your star atlas and determine how far and in what direction is the object you want to see.
• Note any prominent objects between where you are looking and where you want to look.
• Now, move the telescope in the direction and for the distance you determined from the atlas until you find the object you are  looking for.  You may have to move from one object to the next and the next and so on until you get to where you are going -- hence the name "star-hopping," because you are hopping from star to star to find what you want.
• Do a Google search for star-hopping for a better explanation and examples.

A sky atlas is a VERY detailed chart showing the location of thousands of stars.  Sky atlases are many pages long and can be quite detailed -- they are typically used only by serious amateurs and professionals.

Let the computer find things for you

If you stop and think about this process for a minute, you'll come up with an obvious solution to the problem of finding objects in the sky.  Consider the following:

• Objects in the sky "move" across our field of view at a steady, predictable rate because of the rotation of the Earth and because of our movement around the Sun.
• Objects in the sky appear at the same place, the same time, year after year.
• Objects in the sky always appear in the same position relative to each other.  That is -- refer to the sky chart above and note the locations of Procyon, Betelgeuse, Sirius, and Rigel.  These four stars are always in the same relative position, forming a + sign with Betelgeuse at the top, Sirius at the bottom, and Rigel and Procyon on the right and left wings respectively. 

Throw in the fact that observing location will cause the view to change, and you come up with the following conditions:

• If you know where you are on the face of the Earth, the date, and the time, you will know exactly where to look for a specific object.  For example -- if it's 2345 hours, EST, 23 December (year does not matter), then the star Betelgeuse will be at one specific location in the sky -- ditto for everything else in the sky.
  OR

• If you know where two objects are in relation to you and to each other, then you can calculate where every other object is.  For example -- look again at the sky chart.  If you can measure precisely the angle of view from your location to Procyon and Rigel, and the angle between these two objects, then you can calculate the angle at which you must look to see Castor (or any other object)-- you don't need to know where you are, you just need to know the angle to each object you are seeing.  This works because everything in the universe is in a fixed position relative to everything else.

Because of the regularity of movement and position in the universe relative to date, time, and observer location, we can program a computer to calculate where to look in the sky if the computer is told:

• EITHER, observer location, date, and time; OR,
• The location of two known objects.

With this data, the computer can tell you where to look -- or -- better yet, the computer can control motors that drive your telescope and point it for you.

GOTO vs. PUSHTO

The capability of a computer to calculate where objects are in the sky and then to move a telescope so it points to that spot has given rise to two types of automated or semi-automated telescopes -- GOTO scopes and PUSHTO scopes. 

• A GOTO scope is driven by a motors that are controlled by a computer -- tell the computer your location, date, and time and it will calculate where each object is from your vantage point.  You then select from the computer's database the object you want to see, push a button, and the computer moves the scope so it's pointing at the object.  Every telescope manufacturer makes several models of GOTO scopes.  I owned a Meade ETX-90 GOTO scope until it was destroyed in Hurricane Katrina.  The scope was accurate, provided I fed to it the exact location, date, and time -- I obtained that information from a GPS receiver so the input data was accurate.  I would set up the scope, turn it on, tell it the location, date, and time (actually, I had an application that allowed the scope to read the data from a GPS receiver); the scope would "beep" when it was ready; it would go to two stars and ask me to center the stars in the field of view, just to check alignment; then, I could tell the scope to GOTO a certain object, the motors would grind away, the scope would move and "beep" to tell me it was at its destination -- and there would be the object in the middle of the field of view.
   
• A PUSHTO scope, on the other hand, has a computer that tracks where the scope is pointed and that will calculate where to move the scope to see any object -- but -- the PUSHTO scope does not have motors to move it -- you push or pull the scope in the direction indicated by the computer until the computer tells you the scope is pointed at the right spot in the sky to see what you want to see.  The XT-12 Intelliscope is a PUSHTO scope.  The following paragraphs describe how it works.

The Orion Intelliscopes

The following information applies to all the Orion Intelliscopes, although I use my XT-12 as the example.

Remember the earlier discussion in which I said:  "If you know where two objects are in relation to you and to each other, then you can calculate where every other object is.  For example -- look again at the sky chart.  If you can measure precisely the angle of view from your location to Procyon and Rigel, and the angle between these two objects, then you can calculate the angle at which you must look to see Castor (or any other object)-- you don't need to know where you are, you just need to know the angle to each object you are seeing.  This works because everything in the universe is in a fixed position relative to everything else."  Well, this is how the Intelliscope works -- it measures the angle from you to two objects and the angle between these two objects, then, when you ask, it tells you where to go to find any other object.

I will describe how to use the Intelliscope computerized controller and you will understand how it works.

First, here is a view of the XT-12 with the Intelliscope controller connected.  In this photo, the controller is the small handheld device with the coiled cord connected between it and the scope base.

Controller:  Up-close view and the keys

Here is a close-up of the controller.

Most of the keys on the controller have two functions, as shown in this chart:

How it works

Embedded in the scope base are two encoder disks.  These disks rotate as the scope is moved from left to right -- AZIMUTH, or, az -- and as the OTA (the long tube that contains the optics) is moved up and down -- ALTITUDE, or, alt. 

• Look at the photo of the scope -- see the round part sitting on the ground?  There are actually two parts to this base plate -- upper base plate and lower base plate.  The lower base plate -- not visible in the photo -- has feet that sit on the ground, it does not move.  The upper and lower base plates are connected by a single bolt that runs through their center.  Sandwiched between these two plates are several Teflon pads, which are slippery.  When you try to move the scope right or left, the bottom plate will not move but the top base plate slides across the Teflon pads, allowing the scope to rotate in azimuth around the axis established by the bolt that connects the two sections of the base plate.  Also between the upper and lower base plates is the azimuth encoder disk -- as the upper plate moves around the lower plate, the encoder measures how many degrees the upper plate -- and hence, the scope -- has rotated.  This data is fed to the handheld controller as the azimuth movement data.
• Look at the photo of the scope again.  Notice that there is a knob to the right of the controller -- look at the optical tube assembly (OTA) behind the knob and you will see the edge of a large round bearing -- the OTA rides on tow of these bearings that swivel on bumpers set inside the upright part of the base.  There is a close-up and a better explanation of this on page 2 of the XT-12 article.  Sandwiched between one of the OTA bearings and the upright is another encoder disk that measures how far out of vertical the OTA has moved; that data is fed to the controller as altitude data.
• Thus, the scope is now able to tell the controller how many degrees it has moved right or left and up or down.  If the scope knows its starting point and knows the degree of travel from the starting point to two known stars, the controller can then calculate where every other star is -- because it knows the direction to two stars and the angular distance between them.

To use the Intelliscope controller:

1. When the scope is assembled, there is a vertical stop that must be adjusted using a carpenter's level to ensure that when the OTA is against the stop, it is pointed exactly vertical.
2. To use the Intelliscope controller, you must have some familiarity with the night sky -- that is, you must be able to locate at least the brightest stars.  You can do this with a star chart or a planisphere. 
3. Set up the scope.
4. Identify two prominent stars -- they should be bright enough for you to find them without difficulty and they should be 60 degrees apart.  Remember their names and where to find them.
5. Plug in the controller, turn it on.
6. The controller display will show the command PLACE THE SCOPE VERTICAL.
7. Move the OTA so it is against the vertical stop, pointing straight up.
8. Hit ENTER.
9. The display will then tell you to select the first alignment star.
10. Using the UP and DOWN arrow buttons, scroll through the list of alignment stars until you find one of the two stars you have located.
11. DO NOT PUSH ANY BUTTONS. 
12. Move the scope until alignment star #1 is in the center of the field of view through the eyepiece -- take your time, make certain you have the right star and make certain it's centered in the eyepiece.
13. When the first alignment star is centered in the eyepiece, hit ENTER.
14. The display will then tell you to select the second alignment star.
15. Using the UP and DOWN arrow buttons, scroll through the list of alignment stars until you find the second of the two stars you have located.
16. DO NOT PUSH ANY BUTTONS
17. Move the scope until alignment star #2 is in the center of the field of view through the eyepiece -- take your time, make certain you have the right star and make certain it's centered in the eyepiece.
18. When the second alignment star is centered in the eyepiece, hit ENTER.
19. The controller will then display a number between 0.0 and 51.0 -- this is a measure of the quality of your alignment, it's known as the "warp factor."   You want warp factor to be less than 0.3 or 0.4.  A warp factor of 0.5 and up is not a good alignment -- turn off the controller, return the scope to vertical, and do it again.  On my first attempt, the warp factor was 0.3; my warp factor is always 0.1 to 0.3, it's not difficult.
20. Now, the controller is ready to find objects.  For example:
    1. If you want to find a STAR, push the 8/STAR button and use the UP or DOWN arrows to scroll through NAMED, DOUBLE, VARIABLE, or INDEX stars.  Let's say you want to find Arcturus -- scroll through the STAR choices to NAMED and hit ENTER.  Then, scroll through the list of names until you find Arcturus and hit ENTER.
    2. If you want to find a MESSIER object, press the 1/M button and the display shows M001.  Press two or three digits corresponding to the number of the Messier object you want to see -- if you enter two digits, hit the ENTER key and the controller calculates where to go; if you enter three digits, no need to hit the ENTER key.  For example, to find Messier M31, just press the 3 key, the 1 key, and the ENTER key.  To find Messier object 101, enter 1, 0, 1 -- don't hit the ENTER key.
21. When you select the object you want to find and hit ENTER, the controller will then display two arrows -- one pointing left or right, one pointing up or down.  Next to each arrow is a number -- the higher the number, the farther you must move the scope in the indicated direction.
22. Move the OTA left/right, up/down, watching the numbers next to the arrows.  When the number drops below 10, it then shows the number to one decimal place -- e.g., 8.7.  Move the scope until both sets of numbers read 0.0.
23. Look through the finder scope and there is the object you were seeking -- center the object in the finder scope and there you have it.

Here is a photo of the controller moving to the Whirlpool Galaxy (WHIRLPOOL GA)  in the constellation Canes Venatici (CVN).  In the photo on the left, the controller is telling you to move the scope to the right 34 degrees and up 12 degrees.  As the scope is moved, the encoder wheels tell the controller how far the scope has moved in azimuth and altitude -- as the scope moves, the distance to be moved decreases -- in the center photo, the scope still needs to move 7.6 deg right, 5.7 deg up.  In the last photo, the scope is now pointed at the Whirlpool Galaxy -- 0.0 deg right/left, 0.0 deg up/down.  Stop moving the scope and start observing.

If you are looking for a planet -- there is an extra step.  When you hit the 7/PLANET button, the controller asks for the date and year.  Enter this information and the computer calculates where each planet is then you can find them.  Read the instruction manual because the day, month, and year must be entered in a specific manner.

Why does this work?  Because --

1. When you point the scope straight up, the encoders tell the controller the scope is vertical.  The controller than sets its internal readings to 90.0 ALTITUDE and 0.0 AZIMUTH.
2. As you move to the first alignment star, the encoder wheels track how far and in what direction the scope moves, in degrees, up or down, right or left.  When you hit ENTER, the scope knows that the first alignment star is XX degrees from vertical and YY degrees in azimuth from where it started.
3. As you move the scope to the second alignment star, the encoder wheels track how far you move up/down, right/left FROM THE FIRST ALIGNMENT STAR.  When you hit ENTER, the controller now knows how many horizontal and vertical degrees it is between the two alignment stars.  The controller knows where these two stars are in relation to each other and to every other object in its database -- because it has a star almanac in its memory.
4. If the controller knows the azimuth and altitude to two stars, it knows the angular distance between the two, and it can now calculate the location of any other object and can tell you which direction and how far to go to find the object you want to find.
5. Think about it and you'll see just how simple this is.

The Intelliscope controller does not have every single known object in the universe in its memory.  Instead, it has the following in its database:

• 110 Messier objects
• 7,840 New General Catalog objects
• 5,386 Index Catalog objects
• 8 planets
• 99 user-defined objects

Here is a link to a PDF version of the Intelliscope instruction manual -- it is detailed and easy to use.

http://www.telescope.com/text/content/pdf/IN_229_E_CompObjectLocator.pdf

My impressions after using the Intelliscope

Compliments:  I like the Intelliscope controller; I find it easy to use and accurate.

You don't have to use the Intelliscope controller -- the scope works just fine without it.  If I want to star-hop, or just look at one or two objects, there is no need to use the controller.  Just don't plug it in -- leave it in the house or in your eyepiece case and use the scope as a normal Dobsonian scope.

The Intelliscope is accurate and easy to use.  The first time I used the Intelliscope, I used it for two nights, locating 30 different objects.  In every case, after I had pushed the scope to where the display showed 0.0 and 0.0, the object was in the finder scope.  If I was using a high magnification eyepiece -- over 225X, there were a couple of times when the object was not in the eyepiece but was just slightly out of the field of view -- I found these with no problem.  In every other case, the object was in the eyepiece when the controller showed 0.0, 0.0.

Alignment is easy but you do have to pay attention to what you're doing -- it's sometimes a chore to find the alignment stars but if you choose a bright star and are competent with your scope, this is not a problem.  I use a Telrad finder and a 9X50 correct angle finder -- this combination allows me to locate my alignment stars quickly.

Complaints:  I have only two minor complaints.

The Intelliscope controller does not like to get cold.  The two nights I have used the Intelliscope, the outside temperature was in the low 20's.  After about 20 minutes of being very cold, the display dimmed and the controller responded slowly.  It still worked, just noticeably slower than when it was warm.  I am going to try using a hand warmer strapped to the controller with a couple of rubber bands and see how that works.  The controller did not fail to work when it got cold -- it just ran very slowly.

The labels on the controller buttons are easy to read -- but --  I wear tri-focals which I take off when I am using the telescope.  It's a real chore to put my glasses on to read the buttons, take them off the look through the scope, put my glasses back on to read the buttons, take them off again to look through the scope, and back and forth with the glasses -- so, I leave my glasses off.  It's a bit difficult for my old eyes to read the buttons.  The buttons are big enough and the type is big enough -- and they are back lighted -- but be advised if you wear glasses you might have difficulty reading the labels without your glasses.

UPDATE:  When you assemble the Intelliscope, the instructions tell you to set the base on a perfectly level surface.  Then, you install the OTA onto the base and stand it vertical -- using a level, check to see that the tube is vertical.   There is an adjustable stop on the base that you adjust to ensure the OTA is vertical in relationship to the base. 

When you use the Intelliscope, you start off with the OTA vertical -- then -- turn on the handheld controller, find two alignment stars, and align the scope.  It is easy to misinterpret the instructions about the OTA being vertical -- read carefully:

•   When you assemble the scope, set the base on a perfectly flat surface -- check with a level -- install the OTA, stand it vertical, measure the OTA for plumb, and adjust the stop on the base so that the OTA is aligned perfectly vertical in relationship to the base.
   
•  When you use the Intelliscope controller --   set the scope on the ground, plug in the controller, DO NOT TURN THE CONTROLLER ON, then move the OTA to its vertical position against the stop.  This does not mean that the OTA must be perfectly vertical -- that is, if the scope is on rough or un-level ground -- which is common -- the OTA will be slightly out of vertical -- that's fine because the OTA, when it is against the vertical stop on the base, is vertical in relationship to the base -- the scope doesn't care if it's not on level ground.  Carefully read the Intelliscope instruction manual and it tells you the scope does not have to be on level ground after it has been assembled.
   
•  HOWEVER -- sometimes it's not possible to find a good spot to set up the scope, especially if you are at a viewing location that is on rough ground.  For this reason, I made a leveling platform that I can use in case the place where I set up the scope is really rough.  This article shows how I built my leveling platform.  I rarely use this platform -- just find a patch of ground that's reasonably flat and plunk the scope down there, but, sometimes I am at a location where the ground is quite rough and this platform comes in handy to keep the scope sitting on a solid foundation.

•  Here are instructions for that platform.  I rarely use this -- just find a patch of ground that's reasonably flat and plunk the scope down there.

Here is a link to the first of two pages describing the XT-12 Intelliscope -- complete with photos and links to the manufacturer's site.