Leisure Time LX20 Library Object Keys, Unknown Site, Which Alignment Method to Use?

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2.Telescope Position. The first display shows the RA and DEC (telescope position in stellar coordinates) and the second display (accessed by pressing the ENTER key) shows the telescope position in ALTAZ coordinates.

3.Time and Date. The first display shows local and Sidereal time and the second display (accessed by pressing the ENTER key) shows the date.

4.Timer and Freq. This display is a countdown timer and allows the user to change drive rates. These are advanced features.

5. All Off. This mode simply turns off all displays and backlighting. You can also adjust the backlighting brightness by pressing the ENTER key and using the PREV and NEXT keys to adjust the brightness.

f. Library Object Keys

While in any of the 5 main keypad display modes, you can directly access the library objects by using the M, STAR, or CNGC keys (see APPENDIX C, page 31, of this manual for more information on the 64,359 Object Library). Simply press an object key, and type in the number of the object desired, followed by ENTER. For example, a good first object for the first part of the year is M42 — the Great Orion Nebula.

Press the M key, the 4 key, the 2 key, and finally the ENTER key. The display will show data on the object (name, rating, object type, brightness, size). Now press GO TO. The telescope will automatically slew to M42.

If the object entered is not above the horizon, the keypad hand controller will display the message "Object Below Horizon."

Other good first objects (if above the horizon) are any of the M objects — from M1 to M 110, and the planets. To find a planet enter: (NOTE: 903 is the Moon.)

OBJECT LIBRARY PLANET LEGEND

PLANET	STAR #	PLANET	STAR #
MERCURY	901	SATURN	906
VENUS	902	URANUS	907
MARS	904	NEPTUNE	908
JUPITER	905	PLUTO	909

3.Follow the keypad display prompts to choose and center the the second alignment star. Be sure to use the keypad to slew to the second star. After pressing the ENTER key in the last

step, the keypad display should show the TELESCOPE/OBJECT LIBRARY screen.

Important Note: Whenever using either of the 2-Star alignment procedures (at a known SITE or at an unknown SITE), choosing the proper two stars will determine the pointing accuracy of the telescope. Choose two stars that are not too close together — try to use stars that are at least 90° apart. Do not use Polaris because RA changes very fast at the Pole and minor centering errors translate to large RA pointing errors. Also, avoid stars near the zenith (straight up) since azimuth changes very fast in this area. Generally speaking, choosing two stars as far apart as possible will yield very accurate pointing, often within a few arc minutes.

The LX200 calculates the distance between the two stars that you chose in the alignment steps and compares this to the distance that you actually slewed the telescope. This is a check to be sure you centered the correct stars during the alignment steps. Should the LX200 discover a discrepancy, the keypad will display an "Align Mismatch — Check Stars" message. If you get this message after aligning the telescope, check that you are using the correct stars and align again.

c. Unknown SITE

To use the LX200 telescope at an unknown location, use the following procedure:

1.Select site #5 (UNKNOWN) from the SITE menu.

NOTE: This site cannot be edited like site numbers 1 to 4 as described in Entering Basic Information, page 10.

2.Follow the keypad display prompts to select and center the two alignment stars.

As described above, the LX200 will check the accuracy of the two stars and give the "Align Mismatch — Check Stars" message if it detects an error.

d. Which Alignment Method to Use?

Each of the three method described above has advantages and disadvantages. The following table summarizes these properties.

4. Star Alignment

The 2-Star initialization routines provide three options for aligning the LX200 telescope when in the ALTAZ mode.

NOTE: The 2-Star initialization routines only apply to the ALTAZ alignment mode (see MODE FUNCTIONS, page 16, for POLAR and LAND mode initialization).

The first and second options require that entry of the SITE and TIME information as described in Entering Basic Information (page 10). The third option is used when the SITE information is not known or has not been entered into the LX200's memory.

a. 1-Star with Known SITE

The 1-Star alignment routine was explained in detail in Setting Up the Telescope (page 11).

b. 2-Star at Known SITE

To use the 2-Star alignment procedure at a known site, follow these steps:

1.Select the 2-Star alignment (by pressing the "2" key); the keypad display will prompt you to level the base. This leveling step requires a rough level only and, unlike the 1- Star alignment routine, does not affect the pointing accuracy of the telescope. (See Section d. below for a summary of the differences in telescope operation when selecting each of the three alignment procedures.)

2.After leveling the base and pressing ENTER, follow the keypad display prompts to select the first alignment star. Slew to that star using the N, S, E, and W keys.

	1-Star Known	2-Star Known	2-Star
			Unknown
Pointing	Level of	2-Star	2-Star
Accuracy	Telescope	Alignment	Alignment
Determined By:
Atmospheric	Yes	Yes	No
Refraction
Correction*
Atmospheric	Level of	Level	Not
Refraction	Telescope	of Telescope	Applicable
Correction
Determined By:
When Best Used	Best used	Best used on a	Best used
	when the	transportable	when the
	telescope is	telescope with	SITE
	permanently	the SITE	information is
	mounted and	information	not available
	accurately	available
	leveled

*Atmospheric Refraction Correction: Light from an astronomical object is "bent," (refracted) as it passes through the atmosphere. This bending is more pronounced near the horizon because there is more atmosphere for the light to pass through, and it shifts the apparent position of the star. The LX200 calculates this bending and compensates for it when slewing to objects near the horizon.