Celestron C8 diagram: a Schmidt-Cassegrain telescope

Telescope Operation

Sections and Links

  1. Powering Up the Roof System
  2. Mounting/Dismounting the Telescopes on the Roof
  3. Mounting/Dismounting the Telescopes Inside
  4. Observing with the Telescopes
  5. C8 Sky Alignment in General
  6. C8 Sky Alignment Procedure
  7. Using the Telescope
  8. To Turn the Clock Drive On/Off
  9. Taking Down the Telescopes

  1. Powering Up the Roof System

    1. The master power unit is inside the dome on the east wall.

    2. Find the toggle switches on the power unit. When they are turned on, the system box will glow red for all of the toggle switches.

    3. Each of the telescope stands should also have a red light glowing next to the power plug.

  2. Mounting/Dismounting the Telescopes on the Roof

    1. Mounting:

      1. Equatorial mount:

        Two persons are required for safe mounting---one to hold the C8, one to tighten/loosen the screws.

        This is rule: the two person rule.

        Exception: One person can do it if you really think you have the technique and strength to do it safely alone.

        The wedges are permanently installed on the pillars. So nothing is needed at this step.

        Altazimuth mount:

        Take the screw-on pads from a shelf in the shed and screw them onto the pillars.

        The pads should be screwed on snugly, but avoid making them so tight that they can't be unscrewed without great force.

        The pads should be snug enough NOT to move during ordinary telescopes operations.

      2. The C8's are in the roof shed on shelves.

      3. Thanks to Bill, the star-pointer lights (i.e., lasers) work off the power source and don't need batteries anymore.

          Obsolete: If you need C8's with star-pointer lights (i.e., lasers) working, make sure that the lights are working before taking the C8's off the shelves.

          If you the lights arn't working and you what to make them work yourself, you need put in new lithium batteries. See Changing a Star Pointer Battery.

      4. Carry a C8 out of the shed. It's probably best to have one hand under the base and the other on the fork arm. The C8's arn't that heavy, but they are a bit awkward.

        Or load the C8's on a cart for transport.

        The C8's are NOT completely fragile, but nevertheless, you should be quite gentle with them.

      5. Equatorial mount:

        Screw in one screw first and then the 1st person hangs the C8 on the wedge by that screw.

        Then the 2nd person tightens the screw and screws the other two screws in.

        The operation can be done by one skillful, strong enough person, but it's easier and safer with two persons.

        Altazimuth mount:

        Put the C8 on the pad with pad screws aligned with the C8 If you do this neatly, the aligmnent is right right-off. If you don't do it neatly, you may have to manhandle the C8 a bit to get alignment.

        Screw the three screws until they are snug. I find the screwing on with the left hand and screwing off with the right hand is most natural.

      6. The wires with the BNC connectors are in the shed.

        The plug end of a wire goes in the pillar socket, the BNC connector itself goes into the prong on top of the C8 base.

        I find screwing on/off the BNC connector with one hand held over the BNC connector works well.

      7. Thanks to Bill, the star-pointer lights (i.e., lasers) work off the power source and don't need batteries anymore.

        The finderscope still needs batteries for illumination of the crosshairs, but we don't nee that illumination, and so don't worry about batteries at all anymore.

          When setting up the C8's for students, the star pointer and finderscope lights should usually be turned off to save the lithium batteries.

          The students should learn to turn them on for themselves.

          Actually, the finderscope lights are almost never needed.

          Sometimes you will want to turn the star pointer lights on just before they are needed to save time when the students get to the scopes.

          You should try to train students to turn the lights off when they are finished observing.

      8. You should give the C8's an initial focus. See focus knob on figure below.

        Point at a bright star or at a point-like city light and focus with the focusing knob.

        The image of a point source should NOT look like a doughnut.

        The region of focus on the focus knob for the C8's is quite small.

        You sometimes have to turn the knob a long way before getting focus---and it's often NOT clear which way the knob has to be turned to go to focus---keep trying.

        The C8's are NOT designed to focus at relatively short distances, less than about 5 meters. More than about 6 meters allows a focus.

        So in classroom environments you need look at sufficiently remote objects, usually well across the classroom.

    2. Dismounting:

      1. Dismounting is largely mounting in reverse. But there as some fine points.

      2. Level the C8's before turning off the power.

        They are most easily stored when leveled.

      3. Equatorial mount:

        Two person rule: one to hold, one to unscrew.

        The operation can be done by one skillful, strong enough person, but it's easier and safer with two persons.

        Altazimuth mount:

        When unscrewing a pad from a pillar, it helps to loosen it with a C8 still attached to the pad by gently pulling counterclockwise as seen from above on the C8 base or fork arm. Pulling on one of these allows you to exert force more easily. There doesn't seem to be any mechanical advantage though.

        Actually, pulling on the fork arm may NOT be good for the clock drive mechanism.

        So gently pull on the base.

        What if the pad is so tightly screwed on that gentle pulling on the base doesn't work?

        Remove the telesscope and get a wrench from the roof shed. There's one that is just right for putting in one of the pairs flanges on the bottom of the pad. With the wrench, one has mechanical advantage and one should be able to loosen the pad. Someone tighten the pad on by hand, and so it can be that hard to loosen.

      4. Make sure that the wire is disconnected before walking off with a C8.

        The connectors on the wires are NOT strongly fixed. They will break when you walk off and NOT just give a gentle tug reminding you to disconnect.

      5. Make sure the star pointer and finderscope lights are turned off.

        The lithium batteries will burn out before the next use otherwise.

        The lithium batteries do cost money and it is a nuisance to have to change them. See Changing a Star Pointer Battery.

  3. Mounting/Dismounting the Telescopes Inside

    1. The C8's will just sit stably on tables or carts.

    2. You will need a black power unit (which is actually a rectifier) from the storeroom.

      A power unit has wall plug and a round plug for a socket on the base of a C8's near the on/off switch.

      Power units are heavy and get a bit warm when used for awhile.

    3. You will need to focus a C8.

      The region of focus on the focus knob for the C8's is quite small.

      You sometimes have to turn the knob a long way before getting focus---and it's often NOT clear which way the knob has to be turned to go to focus---keep trying.

      The C8's are NOT designed to focus at relatively short distances, less than about 5 meters. More than about 6 meters allows a focus.

      So in classroom environments, you need look at sufficiently remote objects, usually well across the classroom.

      You will just be turning the knob back and forth forever without a focus if you choose an object that is too near.

  4. Observing with the Telescopes

    5. Observing with the telescopes (which in our labs are the C8's) requires a bit of practice and knowing a few tricks.

    The main tricks are detailed in List of Tricks for C8 Telescopes.

    So here we will just list a few tricks in higgledy-piggledy order some redundancy with List of Tricks for C8 Telescopes.

    1. Tricks:

      1. In order to move around on the liquid crystal display (LCD) menus, use the 6 (up) and 9 (down) keys to make your selections, NOT the arrow keys. The arrows are to move the telescope (i.e., the C8) only.

      2. Can you use the star pointer with its light dead?

        Yes.

        If you get a meter or so away from the star pointer and center it on an astronomical object so that the tube of the star pointer projects into a "nearly perfect circle" around the object, then the object usually will be in the finderscope.

        This procedure is a bit finicky, and sometimes it won't work either because the object is too faint or you lose patience.

        Also it takes some practice to identify the "nearly perfect circle".

        Yours truly likes to use the star pointer with the light turned to save the lithium batteries and to keep in practice for those occasions (which happen pretty often) when the lithium batteries is dead.

    2. And a few DON'TS:

      1. Don't slew the C8's by hand.

        Use the arrow keys on keypad.

        Slewing by hand destroys the sky alignment---if that has been set.

        Slewing by hand could also damage the C8's They are designed to slewed by clock drive unit.

        Actually, a little slewing by hand does seem to have hurt any of the C8's.

        So don't be alarmed by a little accidental slewing by hand.

      2. Don't be rough with C8's in any respect.

        They arn't infinitely fragile, but they NOT designed for being yanked or banged about either.

      3. Don't mistreat the pillars or the C8 wedges or pads either.

      4. If you are using the pads (and you probably won't for aeons to come), don't tighten the pads on the pillars so that they hard to get off.

      5. When changing eyepiece, etc. on the C8's, don't unscrew the screws totally. You will drop them on the roof and they will fall into the crevices between the tiles, and we will never get them back.

        Just loosen the screws enough to make the change.

      6. Don't tighten any screw to the max. Just make them snug enough to hold eyepiece rigidly.

      7. Don't wear high heels on the roof.

        The new roof is a lot safer than the old roof.

        But as it ages, gaps will grow between the tiles and some will crack.

        So heels can go into the crevices between the tiles or into the cracks and you will fall on the hard, hard tiles.

  5. C8 Sky Alignment in General

    6. The word "alignment" means many things in astronomy and elsewhere.

    But one thing alignment means is the sky alignment of the C8's which allows the C8 software to point the C8 roughly in the direction of an astronomical objects selected from the LCD key pad menus and can direct C8 clock drive so that astronomical objects stay in the field of view (FOV) as the sky rotates overhead (or, from another perspective, as the Earth turns).

    The sky alignment is NOT perfect, and so one usually has to identify the object on the sky by naked eye, center in the star pointer, center it in the finderscope, and then find it in the FOV of the C8 itself.

    Also since the sky alignment is NOT perfect, the object will NOT usually stay in the FOV for a long time as the sky rotates.

    Usually, we do NOT teach students to do sky alignment, but they could learn how if they wish.

    It's NOT hard, but it does take a bit of practice and it is NOT done instantly.

    Aligning more than one C8 is often a chore. Yours truly needs about 30 minutes to align eight C8's---yours truly would probably get faster with more practice.

    We often don't to sky alignment unless it is necessary for the lab we are doing.

    To do sky alignment, one needs sky objects and a procedure. See the sky map in the the figure below (local link / general link: sky_map_current_time_las_vegas.html) and Sky Alignment Procedure below that.

  6. C8 Sky Alignment Procedure:

    1. The telescope should be set up on either the tripod or scope mount on the roof.

    2. Turn the star pointer on. The power is located on the right side of the device. There are two knobs on the right side of the pointer. One is the power/brightness, and the other is an alignment knob. Be sure you turn the power/brightness knob, which is closer to the back end of the telescope, smaller and has writing on it. If you turn the alignment knob, you will misalign the star pointer. The finderscope will be used for fainter objects. It also has lighted crosshairs; turn them on with the long protruding silver knob.

      Thanks to Bill, the star-pointer lights (i.e., lasers) work off the power source and do NOT need batteries anymore.

    3. Put a 40mm eyepiece into the star diagonal provided with the telescope.

    4. Turn the telescope on. The power switch is located at the base of the fork/arm. On the LCD key pad, there will be a greeting NexStarSE Ready. Press ENTER.

        A very tricky fine point.

        You may think that you should hit ALIGN to start alignment. But no, you hit ENTER.

        ALIGN is hit at another point in the alignment procedure.

    5. Use the Scroll Up ↑ (key 6) and Scroll Down ↓ (key 9) to select the best alignment mode for you:

      1. Solar System Align is usually simplest. You just need one object: e.g., Moon, Venus ♀, Mars ♂, Jupiter ♃, Saturn ♄, etc.
      2. One Star Align is often the next simplest.
      3. Auto Two Star Align, (NOT Two Star Align) is maybe best for high accuracy aligment, but that is usually NOT necessary and the systematics may make it futile: a slight motion of pillar or roof can ruin it.

      Press ENTER.

    6. The time will be displayed. Press UNDO. Unless the time is already the current time.

    7. Enter the time in 24-hour clock format: e.g., 8:45 pm would be entered as 20 45 00. Press ENTER.

      You will just have to figure the sequence for entering those numbers.

      Before starting, you should synchronize your watch (or equivalent) with a good time source: e.g., Official US Time or Time&Date. Perfect synchronization is NOT necessary, but it helps.

    8. The option for daylight saving time or standard time will be given. Use the Scroll Up ↑ (key 6) and Scroll Down ↓ (key 9) to select the proper time. Press ENTER.

    9. The time zone will now be displayed. Select Pacific time. Press ENTER.

    10. The date will now be displayed. Enter the correct date if necessary. Press ENTER.

      Time&Date will also give the date if you need it.

    11. The longitude will now be displayed. Enter 115 08 39 (a longitude in Las Vegas, Nevada) if necessary. Press ENTER.

    12. Select West for longitude if necessary. Press ENTER.

    13. The latitude will now be displayed. Enter 36 06 33 (a latitude inLas Vegas, Nevada) if necessary. Press ENTER.

    14. Select North for latitude. Press ENTER.

    15. The Display will now show Select Solar System Object/Select Star 1. Use the Scroll Up ↑ (key 6) and Scroll Down ↓ (key 9) to select an appropriate star. Press ENTER.

    16. Align Object: Using the arrow keypad on the hand control and looking through the star pointer (set to RATE/9), move the telescope to the astronomical object. You will want to put the red dot as close to the astronomical object as possible. When you are close to the astronomical object with the pointer, look through the eyepiece and center the astronomical object in the eyepiece. Press and hold ALIGN for about 1 second. NOTE: If the telescope is moving too fast for you to make small adjustments with the keypad, you can change the speed of the movement by pressing SLEW and then a number 1-9, 9 being the fastest. 4-5 is recommended for fine adjustment.

    17. For two star alignment, the telescope will now choose a second star to align and move towards it. If the star is NOT visible, press the UNDO button to select another star. You will only be given a choice of 2-3 stars. When the telescope has finished moving, repeat step Align Object.

    18. The display will now say "Alignment Successful".

    19. The telescope is now ready for use.

    20. Further alignment information is at SkyAlign. Telescope Alignment Procedure | 5:45: Best sky alignment video ever!!!

  7. Using the Telescope

    1. To find a star, Messier objects or NGC object with the telescope, make sure you are on the top menu on the LCD hand pad. You will know you are on the top menu, when NexStarSE Ready is displayed. If it is NOT displayed, press UNDO until it is.

    2. Press List (8). Scroll down to Named Stars or Double Stars or SAO or MESSIER or NGC using the Scroll Up ↑ (key 6) and Scroll Down ↓ (key 9). Press ENTER. For the last 3 (SAO, etc.) enter the catalog number at the blinking cursor: e.g., 042 for the Orion Nebula.

    3. Scroll through the list using the Scroll Up ↑ (key 6) and Scroll Down ↓ (key 9) until you find the object you are looking for. Press ENTER. The telescope will slew over to the object. Observe object (see 4 ???).

    4. If the object you are looking for is NOT in the field of view of the eyepiece, use the star pointer or the finderscope to center it. If you need to move the telescope around, use the arrow keys on the hand pad. If the telescope is moving too fast for you to make small adjustments with the keypad, you can change the speed of the movement by pressing SLEW and then a number 1-9, 9 being the fastest. 4-5 is recommended for fine adjustment.

    5. To find a planet, press the PLANET key on the keypad and use the Scroll Up ↑ (key 6) and Scroll Down ↓ (key 9) to select the planet, the Sun, or the Moon. Press ENTER to slew to the planet.

  8. To Turn the Clock Drive On/Off

    1. To turn the clock drive on/off, make sure you are on the top menu on the LCD hand pad. You will know you are on the top menu, when NexStarSE Ready is displayed. If it is NOT displayed, press UNDO until it is.

    2. Press Menu (3) on the keypad. Scroll through the options using the Scroll Up ↑ (key 6) and Scroll Down ↓ (key 9) and select Tracking. Press ENTER.

    3. Scroll through the options and select Mode. Press ENTER.

    4. If you wish to:
      1. Turn the clock drive off, select Off. Press ENTER.
      2. Turn the clock drive on, select Alt-Az (for altazimuth mount) or ??? (for equatorial mount). Press ENTER.

  9. Taking Down the Telescopes

    10. See the above section Mounting/Dismounting the Telescopes on the Roof.