Celestron 11007 Bedienerhandbuch PDF herunterladen (Seite 21)

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The EdgeHD Optical tube is equipped with mirror tension clutches to

help support and minimize lateral movement of the primary mirror

during astrophotography.

To use the mirror clutches:

1. Use the focus knob to adjust the primary mirror to the desired focus.

2. Once in focus, turn the two mirror lock knobs clockwise until both are

very tight and can be turned no further.

Warning! Once the mirror is locked down, do not turn the focuser

knob without loosening the mirror locks rst. Although turning

the focus knob should not damage the telescope, undue stress can

be placed on the focus mechanisms causing excessive image shift

while focusing.

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You can change the power of your telescope just by changing the

eyepiece (ocular). To determine the magnication of your telescope,

simply divide the focal length of the telescope by the focal length of the

eyepiece used. In equation format, the formula looks like this:

Let’s say, for example, you are using the 40 mm Plössl eyepiece. To

determine the magnication you simply divide the focal length of your

telescope (the CPC 800, for example, has a focal length of 2032 mm) by

the focal length of the eyepiece, 40 mm. Dividing 2032 by 40 yields a

magnication of 51 power.

Although the power is variable, each instrument under average skies

has a limit to the highest useful magnication. The general rule is that

60 power can be used for every inch of aperture. For example, the

CPC 800 is 8 inches in diameter. Multiplying 8 by 60 gives a maximum

useful magnication of 480 power. Although this is the maximum useful

magnication, most observing is done in the range of 20 to 35 power for

every inch of aperture which is 160 to 280 times for the CPC 800 telescope.

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Determining the eld of view is important if you want to get an idea of

the angular size of the object you are observing. To calculate the actual

eld of view, divide the apparent eld of the eyepiece (supplied by the

eyepiece manufacturer) by the magnication. In equation format, the

formula looks like this:

As you can see, before determining the eld of view, you must calculate

the magnication. Using the example in the previous section, we can

determine the eld of view using the same 40 mm eyepiece. The 40 mm

Plössl eyepiece has an apparent eld of view of 46°. Divide the 46° by

the magnication, which is 51 power. This yields an actual eld of .9°, or

almost a full degree.

To convert degrees to feet at 1,000 yards, which is more useful for

terrestrial observing, simply multiply by 52.5. Continuing with our

example, multiply the angular eld .9° by 52.5. This produces a linear

eld width of 47 feet at a distance of one thousand yards. The apparent

eld of each eyepiece that Celestron manufactures is found in the

Celestron Accessory Catalog (#93685).

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When working with any optical instrument, there are a few things to

remember to ensure you get the best possible image.

• Never look through window glass. Glass found in household windows

is optically imperfect, and as a result, may vary in thickness from one

part of a window to the next. This inconsistency can and will aect the

ability to focus your telescope. In most cases you will not be able to

achieve a truly sharp image, while in some cases, you may actually see

a double image.

• Never look across or over objects that are producing heat waves. This

includes asphalt parking lots on hot summer days or building rooftops.

• Hazy skies, fog and mist can also make it dicult to focus when

viewing terrestrially. The amount of detail seen under these conditions

is greatly reduced. Also, when photographing under these conditions,

the processed lm may come out a little grainier than normal with

lower contrast and underexposed.

• If you wear corrective lenses (specically glasses), you may want

to remove them when observing with an eyepiece attached to the

telescope. When using a camera, however, you should always wear

corrective lenses to ensure the sharpest possible focus. If you have a

stigmatism, corrective lenses must be worn at all times.

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Mirror

Clutch

Knobs

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