Bedienungsanleitung Celestron CPC Deluxe 800 HD - 11007 (Seite 30 von 50) (Englisch)

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metering which lets you know if your picture is under or overexposed.

Adjustments for proper exposures are made by changing the shutter

speed. Consult your camera’s manual for specic information on

metering and changing shutter speeds

Reducing Vibration

Releasing the shutter manually can cause vibrations, producing blurred

photos. To reduce vibration when tripping the shutter, use a cable

release. A cable release keeps your hands clear of the camera and lens,

thus eliminating the possibility of introducing vibration. Mechanical

shutter releases can be used, though air-type releases are best. Blurry

pictures can also result from shutter speeds that are too slow. To prevent

this, use lms that produce shutter speeds greater than 1/250 of a second

when hand-holding the lens. If the lens is mounted on a tripod, the

exposure length is virtually unlimited.

Another way to reduce vibration is with the Vibration Suppression Pads

(#93503). These pads rest between the ground and tripod feet. They

reduce the vibration amplitude and vibration time.

The following is a brief description of the advantages of imaging at each

f-number conguration and the proper equipment needed to use the

telescope in any of its many settings

f/6.3 with Reducer/Corrector

When imaging some objects like planetary nebula (for example M57, the

Ring Nebula) and small galaxies (M104, the Sombrero Galaxy), larger

image scale is needed to resolve ner detail. These objects are better

shot at f/6.3 or even f/10.

Medium size to small galaxies – f/6.3 imaging gives you ner resolution

then at f/2, but the slower f-number will usually require you to guide

the image while you are taking longer exposures. Guiding can be

accomplished by using an optional Radial Guider or a piggyback guide

scope. The exposure times are about 10 times longer, but the results can

be worth the extra eort. There are some objects that are small enough

and bright enough that they work great at f/6.3. M104 (the Sombrero

Galaxy) can be imaged under dark skies with a series of short exposures

using Track and Accumulate. Ten exposures at 15 seconds each will yield

a nice image and is short enough that you may not need to guide the

exposure at all. For f/6.3 imaging, the optional Reducer/Corrector is

needed. (See Optional Accessory section at the end of this manual).

Lunar or small planetary nebulae – f/10 imaging is more challenging for

long exposure, deep-sky imaging. Guiding needs to be very accurate and

the exposure times need to be much longer, about 25 times longer than

f/2. There are only a select few objects that work well at f/10. The Moon

images ne because it is so bright, but planets are still a bit small and

should be shot at f/20. The Ring Nebula is a good candidate because it is

small and bright. The Ring Nebula (M57) can be imaged in about 30-50

seconds at f/10. The longer the exposure, the better.

Planetary or Lunar – f/20 is a great way to image the planets and

features on the Moon. When imaging the planets, very short exposures

are needed. The exposure lengths range from .03 to .1 seconds on

planetary images. Focus is critical as is good atmospheric conditions.

Generally you will take one image after another until one looks good.

This is due to the atmospheric “seeing” conditions. For every 10

exposures you might save 1. To image at f/20, you need to purchase a 2x

Barlow and a T-adapter or Radial Guider.

>>

Fastar Option – Using your EdgeHD telescope at f/2 with optional

lens assembly.

The EdgeHD telescopes are equipped with a removable secondary

mirror that allows you to convert your f/10 telescope into an f/2 imaging

system capable of exposure times 25 times shorter than those needed

with a f/10 system! The Fastar compatible telescope’s versatility allows it

to be used in many dierent f-number congurations for CCD imaging,

making it the most versatile imaging system available today. With an

optional lens assembly you can easily convert your Fastar compatible

telescope to f/2 prime focus use in a matter of seconds. This makes the

system ideal for imaging deep-sky objects as well as planetary detail.

Described below is the conguration of each f-number and the type of

object best suited to that kind of imaging.







The above gure shows how the secondary mirror is removed when

using the optional CCD camera for f/2 imaging.

Warning: The secondary mirror should never be removed unless

installing the optional f/2 lens assembly. Adjustments to collimation

can easily be made by turning the screws on the top of the secondary

mirror mount without ever having to remove the secondary mirror (see

Telescope Maintenance section of this manual).

The f/# stands for the ratio between the focal length and the diameter

of the light gathering element. For example, the EdgeHD 11” optical

tube has a focal length of 110 inches and a diameter of 11 inches. This

makes the system an f/10, (focal length divided by diameter). When

the secondary is removed and the CCD camera is placed at the Fastar

position, the system becomes f/2. This is a unique feature to some

Celestron telescopes (see gures below).



























Celestron CPC Deluxe 800 HD - 11007 Seite 30

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