Fig. 16: Example of vignetting.

The #64ST T–Adapterpermits close-coupling of

 

 

a camera body to the telescope at a focal length

 

 

of 350mm and an effective photographic speed

1

of f/5.8 for the ETX-60 and f/5 for the ETX-70. In

3

 

 

this format vignetting occurs: the photographic

 

 

image appears on film with a slight darkening

 

 

(vignetting) at the corners of the 35mm frame

4

(Fig. 16).

 

 

When removing the T-Adapter and T-Mount from

 

 

the photo port, the T-Adapter may become

 

 

torqued to either the photo port or the T-Mount.

2

 

If this occurs, the T-Adapter has a slot on both

 

sides which may be used to loosen the T-

 

 

 

 

Adapter. Place a metal straight edge, or similar

Fig. 17: ETX with #64ST T-Adapter.

instrument across the two slots and turn coun-

 

 

 

 

terclockwise to remove the T-Adapter. Photography through a long lens such as the ETX-60AT or ETX-70AT requires special technique for good results, and the photographer should proba- bly expect to waste a roll or two of film in acquiring this technique. Long-lens photography has its own rewards, however, rewards that short-focus lenses cannot duplicate.

A few tips on photography with the ETX-60AT or ETX-70AT:

1.Use the optional #882 Standard Field Tripod or the #883 Deluxe Field Tripod as a platform for the telescope. At an effective focal length of 350mm, even small external vibrations can easily ruin an otherwise good photo.

CAUTION: With the #64ST T-Adapter and a camera body mounted to the ETX- 60AT or ETX-70AT photo port, the telescope can only be rotated vertically about 45°. Moving past this point may damage the telescope and camera.

2.Use a cable-operated shutter release. Touching the camera body to initiate shutter opera- tion almost certainly introduces undesirable vibrations.

3.Focus the image with extreme care. While observing the subject through the camera’s reflex viewfinder, turn the telescope’s focus knob (8, Fig. 1) to achieve the sharpest pos- sible focus. Note that some 35mm cameras may have an optional focusing screen (avail- able 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 your telescope may have an exposure meter that is still active when the standard lens is removed and the body is connected to the tel- escope with the T–Mount. If used for terrestrial photography, the camera meter should be acceptable. If used for astrophotography, the meter probably will not pro- vide good results since camera meters are not made to compensate for a dark sky.

5.Terrestrial photography through the ETX-60AT or ETX-70AT is sensitive to heat waves ris- ing 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 the ETX-60AT or ETX-70AT can be espe- cially 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 “APPENDIX A,” page 31.

NOTE: Long exposure photography of deep-sky objects is not practical with the ETX-60AT and ETX-70AT, since this type of photography requires special elec- tronic and optical guiding devices not available for these telescopes.

24 Advanced Features

Page 24
Image 24
Meade Instrument across the two slots and turn coun, Few tips on photography with the ETX-60AT or ETX-70AT

ETX-70AT specifications

The Meade ETX-70AT is a compact, portable telescope that caters to both amateur astronomers and educational purposes. This telescope is part of the renowned ETX series, known for its innovative features and user-friendly design. With an aperture of 70mm, the ETX-70AT is designed to provide clear, bright images of celestial objects, making it an ideal choice for novice astronomers eager to explore the night sky.

One of the standout features of the ETX-70AT is its Maksutov-Cassegrain optical design. This design combines a Maksutov corrector plate with a compact cassegrain layout, allowing for a shorter tube length while still providing excellent optical performance. As a result, users can easily transport the telescope to various observing locations without compromising on image quality.

The telescope boasts a focal length of 350mm, which offers a wide field of view, allowing observers to comfortably locate and track celestial phenomena. The ETX-70AT comes equipped with a built-in electronic control system known as the Audio Star, featuring a database of over 30,000 celestial objects. This system not only makes it easier for users to locate specific targets but also enhances the overall observing experience by providing informative audio commentary about different astronomical objects.

Another notable characteristic is its lightweight design, weighing in at just around 5 lbs. This portability factor makes it an excellent choice for stargazers who prefer to travel or hike to optimal viewing locations. The telescope is mounted on an adjustable and stable aluminum tripods, providing a solid foundation for viewing.

The Meade ETX-70AT also includes a variety of accessories, including two eyepieces (26mm and 9.7mm), a finder scope to help users aim accurately, and a variety of optional filters to enhance viewing contrast and clarity. Furthermore, the telescope supports direct connection to a computer for astrophotography, enabling enthusiasts to capture their astronomical observations digitally.

In summary, the Meade ETX-70AT is an exceptional entry-level telescope that combines portability, advanced technology, and ease of use. With its powerful optics, automated features, and impressive accessory offerings, it serves as an excellent tool for any individual or educational institution looking to delve into the wonders of astronomy.