 |
|||||||
 |
 |
 |
 |
 |
 |
 |
 |
Losmandy G11 User Manual |
|
Checking the parts Your G-11 mount was shipped in four or more boxes. The contents of each box are as follows:
|
|
| Assembling the tripod |
| Remove the legs, leg clamps and weight shaft from the box. Place one leg clamp on the end of each tripod leg, making sure the screw on the side of each leg clamp lines up with the hole on the tripod leg. These clamps will remain on the legs and will not be taken off. Slide the legs onto the Centre column and lock in place by turning each knob on the leg clamps. The tripod is now ready for the equatorial mount. |
| Attaching the equatorial mount |
After the tripod is set up, you are ready to attach the equatorial mount.
This is the platform to which the telescope attaches and allows you to direct it
anywhere in the sky.
The mount is also adjustable so you can orient the axis of rotation
to make it parallel with the Earth’s axis of rotation (see the section on
Polar Alignment). To attach the equatorial mount to the
tripod:
|
| Attaching the counterweight bar |
To properly balance the telescope, the mount comes with a counterweight bar and
counterweight. To install the counterweight bar:
|
| Attaching the counterweight |
The Losmandy G-11 comes standard with one 21 pound counterweight.
To install the counterweight:
|
| Attaching the telescope to the mount |
The telescope attaches to the mount via a dovetail bar bolted to the bottom of the
telescope. Before you attach the optical tube, make sure that the declination and
right ascension clutch knobs are tight. This will ensure that the mount does not
move suddenly while attaching the telescope. To mount the telescope
tube:
|
| Installing the polar alignment finder |
To aid in polar aligning the mount, your Losmandy G-11 accepts an optional Polar
Axis Finder which fits directly into the polar axis. To install:
|
| Installing the polar alignment illuminator |
If you look through the Polar Axis Finder in the daytime the reticle is clearly
visible. To see the reticle at night, however, you need to install the
illuminator.
|
| Moving the telescope in R.A. and DEC |
|
Once the telescope is set up, you will need to point it at various locations to
observe different objects. Unlike other systems, the Losmandy mounts have a
clutch system. To make rough adjustments, loosen the R.A. and DEC clutch knobs
slightly and move the telescope in the desired direction. The R.A. clutch knob is
near the Polar Axis Finder while the DEC clutch knob is at the top of the
counterweight bar. How tight should the clutch knobs be? You set the
clutch knobs to the friction you like. When you want to move the
telescope, all you do is grab the telescope and move it to its new
position. For fine adjustments, use the fast-set function on the hand control box. For more information please see the section on Using the Drive. |
| Balancing the telescope on R.A. |
To eliminate undue stress on the mount, the telescope should be properly balanced
around the polar axis. Proper balancing is crucial for accurate tracking.
To balance the mount:
|
| Balancing the mount in DEC |
Although the telescope does not track in declination, the telescope should also be balanced in this
axis to prevent any sudden motions when the DEC clutch knob is loose. To
balance the telescope in DEC:
Like R.A. balance, these are general balance instructions and will reduce undue stress on the mount. When taking astro-photographs, this balance process should be done for the specific area at which the telescope is pointing. |
| Adjusting the mount for polar alignment |
In order for the clock drive
to track accurately, the telescope’s axis of rotation must be parallel to
the Earth’s axis of rotation, a process known as polar alignment. Polar
alignment is achieved NOT by moving the telescope in R.A, or DEC, but by
adjusting the mount vertically, which is called altitude, and
horizontally, which is called azimuth. This section simply covers
the correct movement of the telescope during the polar alignment process.
The actual process of polar alignment, (making the telescope’s axis of
rotation parallel to the Earth’s) is described later in this manual in the
section on Polar Alignment. To adjust the mount in altitude:
Keep in mind that adjusting the mount is done during the polar alignment process only. Once polar aligned, the mount must NOT be moved. Pointing the telescope is done by moving the mount in right ascension and declination, as described earlier in this manual. Once the appropriate adjustments have been made and you are aligned on the celestial pole, turn the clock drive on and the telescope will track. |
| |
G-11 Technical Specifications |
| Below is pertinent technical information on your Losmandy G-11 telescope that technophiles may find useful. |
| R.A. & DEC axis |
|
| Tripod |
Distance from the DEC/R.A. junction to the top of the saddle is 7". Please note that these specifications are subject to change without notice and stated for the Losmandy G-11 mount with the standard accessories. |
| The G-11 drive system |
| The drive system uses a 5.625" diameter 7075 aluminium gear with 360 teeth for incredibly accurate tracking. One of the most unique features of the new drive is the Periodic Error Correction (PEC) function. This feature allows the drive system to learn the characteristics of the worm gear, and as a result, improve the tracking accuracy even more. This typically reduces the periodic error to 30 percent or less of the original error. The amount of improvement varies depending on guiding skill, atmospheric stability, the characteristics of the worm gear, and the accuracy of polar alignment. Following is a brief discussion of each feature. |
| Power Up the Drive |
|
In order to activate the drive, you must first plug it into an external power source.
To supply power to your Losmandy G-11 plug your DC or AC power cord into the outlet on
the electronic console labeled "12V IN." Then, plug the other end of the adapter into
the appropriate power source (either AC or DC depending on the adapter used).
Next, plug the R.A. and DEC cables into the electronic box. The receptacles are on the upper right portion of the box (R.A. is on the left; DEC is on the right). Then plug the cables into the respective motors. Once plugged into the proper power source, activate the drive by placing the ON/OFF switch in the "ON" position. Once activated, the drive begins tracking at the default sidereal rate. The LED below the sidereal rate icon will illuminate. |
| G/S (Guide Setting) |
|
This function allows you to select the speed at which the motor moves when corrections
are made via the hand controller. Once the drive is activated, the default setting
is .3 times sidereal rate. Press the button to change the guiding rate.
The sections are .3x, .5x, 2x, 4x, 8x, and 16x sidereal rate.
For guiding, use either the .3x or .5x setting. These two rates allow optical use with auto guiders. For auto guiders, use the 2x setting for calibrating and .5x for playback. The faster settings of 2x, 4x, 8x, and 16x are perfect for positioning objects within the field of view. To move the telescope at the 16x speed WITHOUT changing the guide setting, press the button that corresponds to the direction you want to move the telescope. While holding the button down, press the opposite directional button. For example, if you want to move the telescope west, hold the west button down and then press the east button. Conversely, if you want to move the telescopes east, hold the east button down and then press the west button. This fast-set function also works in declination. NOTE: THE R.A. SETTING CIRCLE DOES NOT REMAIN CALIBRATED WHEN USING ANY OF THE SLEWING RATES. |
| TVC - Time Variable (Dec. Backlash) Compensation |
|
The TVC (Time Variable Compensation) function allows you to eliminate the backlash in the DEC motor when changing directions such as from north to south or vice versa. Each time you change the direction of the telescope in declination, the motor speeds up momentarily to take up any slack, There are ten settings - each indicated by an illuminated red bar. The best setting is determined by looking through the eyepiece while changing the direction of the DEC motor and then moving through the TVC settings until the backlash has been eliminated.
To activate this function, press the TVC button. Once activated, the bar on the far right of the display will illuminate. Press the TVC button again, and the next bar will illuminate, and so on for all ten settings. Note that the first bar (on the far right) always stays illuminated while the TVC function is activated. A setting of three to six bars typically eliminates any backlash. The TVC must be reset each time you power up the drive. |
| Tracking Rate Selection |
|
The drive has four basic rates: sidereal, King (a modified sidereal rate), solar,
and lunar. While solar and lunar rates are obvious, sidereal and King rates require a
little more explaining. Sidereal rate is based on a single rotation of the Earth which
takes 1,432.5 minutes. Unfortunately, atmospheric refraction causes objects near the
horizon to move at slightly different rates, a fact discovered by an astronomer by the
name of King. The King Rate takes into account this refraction caused by the Earth’s
atmosphere and is recommended for deep sky astro-photography. For deep-sky observing,
either King or sidereal rate is fine.
Each of the tracking rates is represented by an icon. Sidereal rate is represented by a star, King rate by a crown, solar rate by a sun, and lunar rate by a crescent moon. Underneath each icon is an LED to indicate which rate has been selected. Once the power has been turned on, the drive tracks at the default sidereal rate. To change the tracking rate, press the "RATE" button. Pressing the button increments the rates sequentially from left to right as listed previously. NOTE: The PEC does NOT have to be activated for the drive to work. Once PEC is activated, however, you can only use .3x or .5x tracking rate. You can not change to a faster rate until PEC is turned off. |
| Periodic Error Correction (PEC) |
Periodic Error Correction, or PEC, is a system that improves the tracking accuracy
of the drive. PEC is designed to improve photographic quality by reducing the
amplitude of the worm gear errors. Periodic error is a slight oscillation in right
ascension caused by imperfections in all drive gears. The cycle of the periodic
error is equal to one rotation of the worm gear, which is four minutes for the G-11.
No matter how precise, all telescope drives will have some periodic error, though
it is already extremely low on the Losmandy G-11. Using the PEC function is a
two-step process. First, you must guide for at least four minutes, keeping the
guide star centered on the cross hairs of your guiding eyepiece, during which time
the system records the correction you make. It takes the worm gear four minutes to make
one complete revolution, hence the need to guide for four minutes. The second step
is to play back the corrections you made during the recording phase.
The microcomputer inside the electronic console does this automatically after one
revolution of the worm gear. Keep in mind that this feature is for advanced
astro-photographers and requires careful guiding. Here’s how to use the PEC
function most effectively.
Once you have used the PEC function for a while you may mistake its operation for the way the drive normally operates. The best way to see how well the PEC function works is to turn if off and note the change in tracking. PEC results improve with practice and patience. |
| Dim |
| The DIM button changes the intensity of the LED displays. There are five brightness ranges with the default to the maximum setting. This feature allows the LEDs to be dimmed to an acceptable level so as not to be a distraction when observing and photographing |
| HC/CCD |
| This modular phone style outlet accepts the hand controller needed for guiding and moving the telescope. In addition, the outlet is wired to accept all SBIG Auto Guiders. Push the connector on the cable into the outlet until the plastic tab clicks. To remove the cable, squeeze the plastic tab and pull away from the outlet. Phone jack splitters are available so that the hand controller and auto guider can be used at the same time. |
| 12 VDC in |
| This outlet is used to supply power to the telescope mount. Your Losmandy G-11 comes standard with a DC adapter. To install, plug the connector into the electronic box first, then the power source. |
| 12 VDC out |
| The 12 V DC OUT is for auxiliary accessories that require power, such as digital setting circles. The accessories need a plug like the one on the DC adapter. NOTE: Centre core positive(+) plug. |
| R.A./DEC outlets |
| In the upper right corner of the electronic console are two modular phone-type outlets; one labeled R.A. for the Right Ascension motor, and the other DEC for the Declination motor. Push the connector at the end of the cable into the outlet until the plastic tab clicks. To remove the cable, squeeze the plastic tab and remove it from the outlet. |
| Northern/Southern hemisphere operation |
When using your Losmandy G-11 in the southern hemisphere, there is a need to
reverse the motors. In some mounts this is accomplished by installing a reversed
motor. In the G-11 the direction the drive motor moves the telescope is within
the control of the user. Changing from northern hemisphere to southern hemisphere
requires changing the polarity of the drive motor. To do this:
For quick changes, press one of the R.A. buttons while powering up the drive. Which R.A. button do you press? It depends on the directional setting of the R.A. switch (see the section on R.A./DEC REVERSE). The best way is to do it by trial and error; press one button while powering up the drive. If it does not work, turn the drive off and try the process again while pressing the other R.A. button. The hand controller allows you to move the telescope in R.A. and DEC using the corresponding motors. This includes fine corrections for guided astro-photography and minor adjustments for centering objects in the field of view. The buttons on the hand controller are intentionally labeled rather simply. This is due to the fact that the direction of motion of the mount varies depending on how the telescope is oriented. Furthermore, these buttons are user definable to eliminate confusion when guiding. For more information, see the section on R.A./DEC Reverse. Once again, to move the telescope at the 16x speed WITHOUT changing the guide setting, press the button that corresponds to the direction you want to move the telescope. While holding the button down, press the opposite directional button. For example, if you want to move the telescope west, hold the west button down and then press the east button. Conversely, if you want to move the telescope east, hold the east button down then press the west button. This fast-set function also works in declination. |
| R.A./DEC Reverse |
|
As mentioned previously, the direction a particular button moves the mount
varies depending on the telescope’s orientation (i.e., whether its on the east
or west side of the mount.) This can create confusion when guiding if you
change the telescope’s orientation during a given photographic session.
To compensate for this, the direction of the R.A. and DEC buttons are changeable.
To reverse the direction of either the R.A. and/or DEC buttons change the switch
setting of the appropriate axis. The switches that control these settings are
found on the upper portion of the hand controller.
The next section deals with observational astronomy in general. It includes information on the night sky, polar alignment, and using your telescope for astronomical observing. And finally, if you're having problems, then check out the troubleshooting guide |
| losmandy.co.uk is brought to you by Venturescope your friendly Telescope retailer in the UK. Sitemap |