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OBSERVING

CHAPTER

PHOTOGRAPHY WITH BOTH ETX MODELS

Photography through either ETX model requires the addition of the

optional #64 T–Adapter (see

OPTIONAL ACCESSORIES

, page 17).

With the #64 T-Adapter attached to the telescope (Fig. 20),

through-the-telescope photography is possible with any 35mm

camera body with a removable lens. In this way the telescope

effectively becomes the lens of the camera.

For through-the-telescope photography, turn the flip-mirror control,

(5, Fig. 20) to the “down” position, allowing light to pass straight

through the telescope and out the photo port (17, Fig. 1). With the

flip-mirror control in the “down” position and the photo port’s dust

cover removed, you can see the front lens of the telescope when

you look through the photo port. The #64 T-Adapter threads onto

the photo port, followed by a T-mount for the particular brand of

35mm camera being used, followed by the camera body (with the

camera lens removed).

The #64 T-Adapter consists of two sections (1 and 2, Fig. 20),

which are threaded together in shipment. You may use either of

the following photographic mounting formats to couple the camera

body to the telescope’s photo port thread.

• Format 1: Camera Body + T-Mount + Section (1) of the #64 T-

Adapter (7, Fig. 20).

ETX-90EC 1250mm at f/13.8

ETX-125EC 1900mm at f/15

Format 1 utilizes only the short section of the #64 T–Adapter to

permit close-coupling of a camera body to the telescope. In this

format vignetting will occur: the photographic image will appear

on film with a slight darkening at the corners of the 35mm frame

(see Fig. 21).

• Format 2: Camera Body + T-Mount + Sections (1) and (2) of the

#64 T-Adapter (see Fig. 20).

ETX-90EC 1450mm at f/16

ETX-125EC 2310mm at f/18

Format 2 utilizes both sections of the #64 T-Adapter threaded

together to form a rigid unit. In this configuration there is no field

vignetting: images are illuminated to the edges of a standard

35mm frame (see Fig. 22).

To frame an object in the viewfinder of the 35mm camera body,

slightly loosen the knurled attachment ring (3, Fig. 20), which

threads the #64 T-Adapter to the telescope’s photo port; rotate the

camera body to achieve proper framing of the object; then re-

tighten the knurled ring.

Photography through a long lens, such as the ETX requires

special technique for good results. The photographer should

expect to waste a roll or two of film in acquiring this technique.

Long-lens photography has its own rewards, however, which

short-focus lenses cannot duplicate.

A few tips on photography with both ETX models

1. Use the optional table tripod specific to your model of ETX, or

the #883 Deluxe Field Tripod as a platform for the telescope. At

effective focal lengths of 1250mm to 1450mm (ETX-90EC) or

1900mm to 2310mm (ETX–125EC), even small external

vibrations can easily ruin an otherwise good photo.

CAUTION: With the #64 T-Adapter and a camera body

mounted to the ETX photo port, the telescope can be

rotated vertically only 45°. Moving past this point may

damage the telescope and camera.

2. Use a cable-operated shutter release. Touching the camera

body to operate the shutter will almost certainly introduce

undesirable vibrations.

3. Focus the image with extreme care. While observing the

subject through the camera’s reflex viewfinder, turn the ETX's

focus knob (9, Fig. 1) to achieve the sharpest possible focus.

Note that some 35mm cameras may have an optional focusing

screen (available from the manufacturer) for use with a long

telephoto lens. This screen provides a brighter and clearer

image to focus and is highly recommended.

4. Correct shutter speeds vary widely, depending on lighting

conditions and film used. Trial-and-error is the best way to

determine proper shutter speed in any given application.

NOTE: The camera used with either ETX model may have an

exposure meter that is still active when the standard lens is

removed and the body is connected to the telescope with the

T–mount. If used for terrestrial photography, the camera meter

should be acceptable. If used for astrophotography, the meter

probably will not provide good results since camera meters are not

made to compensate for a dark sky.

5. Terrestrial photography through either ETX model is sensitive

to heat waves rising from the Earth’s surface. Long distance

photography is best accomplished in the early morning hours

before the earth has had time to build up heat.

6. Photography of the Moon and planets through either ETX

model can be especially gratifying, but points 1 through 4

should be particularly noted in this case. Lunar or planetary

photography requires that the telescope be polar aligned (see

Polar Alignment Pro c e d u r e, page 12), and that the

t e l e s c o p e ’s motor drive be in operation (see E l e c t ro n i c

Controller Modes, page 11).

NOTE:Long-exposure photography of deep-sky objects is not

practical with either ETX model, since this type of photography

requires special electronic and optical guiding devices not

available for this telescope.

Fig.20: Example of photography through the ETX using the

#64 T–Adapter. (1) Short section of #64 T-Adapter;

(2) Extension section of #64 T-Adapter; (3) Knurled attachment

ring; (4) T-mount; (5) Flip-

mirror control in “down” position; (6)

35mm camera body; (7) Format 1.

4 5

Fig.21: Example of a format 1 photo.

Fig.22: Example of a format 2 photo.

1 2 ... 10 11 12 13 14 15 16 17 18 19 20 ... 27 28

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