Meade Instruments LX200 - Manual (Page 49)

Meade Instruments Corporation - Meade LX200 Instruction Manuals
Some beginning observers have a tough time discerning objects less than about 1 arc minute in size
unless it is a double star or a planet. Astrophotographers and those involved with CCD imaging may want
to set a higher value based off of desired image scale coverage that would be most impressive with
different films or types of CCD cameras. Enter the new value in arc minutes, then press ENTER to exit to
the option file.
[ toc ] e) SMALLER
The SMALLER menu file option is the upper size object limit. At power up the setting is for 200' arc minutes
or 3.33 degrees. This setting is high enough to cover the largest objects in the OBJECT LIBRARY. You
may want to lower the value because of true field-of-view limitations of a particular eyepiece (see the
RADIUS parameter option for calculating true field).
Other reasons for limiting the value in SMALLER is for astrophotographic or CCD imaging requirements
where we don't want the object to exceed the imaging area of the film or the CCD chip.
[ toc ] f) BRIGHTER
The lower brightness limits based on stellar magnitude can be limited in the BRIGHTER menu file option.
At power up, the magnitude value is set to a very faint level of +20.0.
You may want to adjust the magnitude level to a brighter value starting at perhaps the limiting visual
magnitude of your LX200, which is approximately 14.0 for an 8" and 14.5 for a 10". If you are making
astrophotographs, the limiting magnitudes are about 16.5 and 17 for the eight and ten inch instruments
respectively. Sky conditions also greatly affect the limiting magnitude due to atmospheric haze, high
clouds, light pollution, or combinations thereof.
[ toc ] g) FAINTER
The upper level of brightness may also be adjusted with the FAINTER menu file option, although you may
find few applications for limiting it to a lower value.
[ toc ] h) RADIUS
The RADIUS value sets the boundaries of what and how many objects the LX200 recognizes is in a given
eyepiece while in the FIELD menu selection. At power up the RADIUS menu file option is set to 15 arc
minutes, the radius of 1/2 a degree (30 arc minutes), which is about the proper setting for a 26mm
eyepiece used in an 8" f/10 LX200.
To calculate the true field of an eyepiece in the telescope, first divide the focal length of the telescope (e.g.
2000mm for an 8" f/10) by the focal length of the eyepiece (the standard supplied eyepiece is a 26mm
Super Plössl, 2000 divided by 26 equals 77X magnification). Then find the apparent field of the eyepiece
(which is 52 degrees for the 26mm Super Plössl) and divide it by the magnification (52 divided by 77
equals .67 degrees, multiplied by 60 equals 40.2 arc minutes).
To get the radius of the true field of view, divide the true field by 2. In the case of the above equation, 40.2
arc minutes divided by 2 equals 20.1 arc minutes.
[ toc ] 2. Mode Two: COORDINATES/ GO TO
Mode two allows you to see where you have pointed the LX200 in two celestial coordinate formats, either
Right Ascension and Declination or Altazimuth. Also in this mode you can enter new Right Ascension and
Declination coordinates for any sky position, perhaps to locate objects not in the LX200 library such as
comets or asteroids and have your telescope slew to the new coordinates.
[ toc ] a. Coordinates Menu File
You will at first see the RA = and DEC = coordinates of where the telescope is pointing. If you move the
LX200 with the N,S,W,or E keys, the coordinates display will immediately update the new position in Right
Ascension and Declination.
You can also display computed information of the Altazimuth coordinates (ALT = and AZ =) by pressing the
ENTER key. To return to RA = and DEC =, press the ENTER key again.
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