Handleiding Celestron CPC Deluxe 800 HD - 11007 (pagina 28 van 50) (Engels)

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This form of celestial photography is designed for objects with small

angular sizes, primarily the Moon and planets. Planets, although

physically quite large, appear small in angular size because of their

great distances. Moderate to high magnication is, therefore, required

to make the image large enough to see any detail. Unfortunately,

the camera/telescope combination alone does not provide enough

magnication to produce a usable image size on lm. In order to get the

image large enough, you must attach your camera to the telescope with

the eyepiece in place. To do so, you need two additional accessories; a

deluxe tele-extender (#93643), which attaches to the visual back and a

T-ring for your particular camera make (i.e., Minolta, Nikon, Pentax, etc.).

Because of the high magnications during eyepiece projection, the eld

of view is quite small which makes it dicult to nd and center objects.

To make the job a little easier, align the nder as accurately as possible.

This allows you to get the object in the telescope’s eld based on the

nder’s view alone.







Another problem introduced by the high magnication is vibration.

Simply tripping the shutter – even with a cable release – produces enough

vibration to smear the image. To get around this, use the camera’s self-

timer if the exposure time is less than one second – a common occurrence

when photographing the Moon. For exposures over one second, use the

“hat trick.” This technique incorporates a hand-held black card placed

over the aperture of the telescope to act as a shutter. The card prevents

light from entering the telescope while the shutter is released. Once

the shutter has been released and the vibration has diminished (a few

seconds), move the black card out of the way to expose the lm. After

the exposure is complete, place the card over the front of the telescope

and close the shutter. Advance the lm and you’re ready for your next

shot. Keep in mind that the card should be held a few inches in front of

the telescope, and not touching it. It is easier if you use two people for

this process; one to release the camera shutter and one to hold the card.

Here’s the process for making the exposure.

1. Find and center the desired target in the viewnder of your camera.

2. Turn the focus knob until the image is as sharp as possible.

3. Place the black card over the front of the telescope.

4. Release the shutter using a cable release.

5. Wait for the vibration caused by releasing the shutter to diminish.

Also, wait for a moment of good seeing.

6. Remove the black card from in front of the telescope for the duration

of the exposure (see accompanying table).

7. Replace the black card over the front of the telescope.

8. Close the camera’s shutter.

Advance the lm and you are ready for your next exposure. Don’t forget

to take photos of varying duration and keep accurate records of what you

have done. Record the date, telescope, exposure duration, eyepiece,

f/ratio, lm and some comments on the seeing conditions.

The following table lists exposures for eyepiece projection with a 10 mm

eyepiece. All exposure times are listed in seconds or fractions of

a second.





Planet ISO 50 ISO 100 ISO 200 ISO 400

Moon 4 2 1 1/2

Mercury 16 8 4 2

Venus 1/2 1/4 1/8 1/15

Mars 16 8 4 2

Jupiter 8 4 2 1

Saturn 16 8 4 2

The exposure times listed here should be used as a starting point. Always

make exposures that are longer and shorter than the recommended

time. Also, take a few photos at each shutter speed. This will ensure that

you get a good photo. It is not uncommon to go through an entire roll of

36 exposures and have only one good shot.

NOTE: Don’t expect to record more detail than you can see

visually in the eyepiece at the time you are photographing.

Once you have mastered the technique, experiment with dierent lms,

dierent focal length eyepieces and even dierent lters.

>>

This is the last form of celestial photography to be attempted after

others have been mastered. It is intended primarily for deep sky objects

that are objects outside our solar system which includes star clusters,

nebulae and galaxies. While it may seem that high magnication is

required for these objects, just the opposite is true. Most of these objects

cover large angular areas and t nicely into the prime focus eld of your

telescope. The brightness of these objects, however, requires long

exposure times and, as a result, are rather dicult to photograph.

There are several techniques for this type of photography, and the

one chosen will determine the standard accessories needed. The best

method for long exposure deep sky astrophotography is with an o-axis

guider. This device allows you to photograph and guide through the

telescope simultaneously. Celestron oers a very special and advanced

o-axis guider, called the Radial Guider (#94176). In addition, you will

need a T-Ring to attach your camera to the Radial Guider.

Other equipment needs include a guiding eyepiece. Unlike other

forms of astrophotography which allows for fairly loose guiding, prime

focus requires meticulous guiding for long periods. To accomplish this

you need a guiding ocular with an illuminated reticle to monitor your

guide star. For this purpose, Celestron oers the Micro Guide Eyepiece

(#94171). Here is a brief summary of the technique.

1. Polar align the telescope using an optional equatorial wedge. To polar

align the CPC you must select EQ North Align (or EO South Align)

from the alignment options. For more information on polar aligning,

see the Polar Alignment section earlier in the manual.

2. Remove all visual accessories.

3. Thread the Radial Guider onto your telescope.

4. Thread the T-Ring onto the Radial Guider.

T-Ring

Tele-Extender

Eyepiece

Visual Back

35 mm SLR

Celestron CPC Deluxe 800 HD - 11007 Handleiding

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