tions, 2" eyepieces can give a wider field of view than standard 1.25" eyepieces. This is especially desirable for observing
To use 2" eyepieces, simply loosen the thumb screw on the star diagonal that secures the 1.25" adapter, and remove the adapter. Insert a 2" eyepiece directly into the diagonal, and secure it in place with the thumb screw on the diagonal. You are now ready to observe with the 2" eyepiece. If you attempt to place a 2" eyepiece directly into the focuser drawtube with- out using the star diagonal, images will not come into focus. If you wish to view with 2" eyepieces without using the diagonal, you will need to purchase an optional 2" extension tube.
Use of 1.25” Eyepieces without a Diagonal
The SkyView Pro 100mm ED can use 1.25" eyepieces with- out a 90° star diagonal if desired. Viewing straight through the telescope may be more comfortable for observing objects low on the horizon. When viewing straight through the telescope without a diagonal the view will be oriented the same as the finder scope (rotated 180°, see Figure 7).
To use a 1.25” eyepiece without a diagonal, remove the 2" diagonal by first loosening the two thumb screws on the fo- cuser drawtube. Insert the camera adapter and secure it by tightening the drawtube’s thumb screws. Loosen the thumb screw on the camera adapter and insert the barrel of a 1.25" eyepiece into it. Secure the eyepiece with the thumb screw on the camera adapter.
Note About Chromatic Aberration
Chromatic aberration literally means color distortion. Whenever light passes through one material to another, light of differ- ent wavelengths (color) is bent by different amounts. This is
aproblem that plagues
R.A. setting circle
|
|
| Ascension | |
Polar axis finder scope | Right | |||
(optional) |
|
| Axis | |
|
| |||
|
|
| ||
Latitude scale |
|
| ||
(opposite side) |
|
| ||
|
|
|
| |
Latitude |
|
| ||
adjustment |
|
| ||
|
|
| ||
astronomical objects emit a spectrum comprised of many dif- ferent wavelengths of light, so each wavelength will be bent by a slightly different amount when passing through a lens. This results in each color of light reaching precise focus at a slightly different point, which will provide unacceptable images.
The 100mm ED is designed to minimize chromatic aberra- tion. The objective lens is actually comprised of two individual lenses, called elements, one of which is made of ED (Extra- low Dispersion) glass, a special type of glass that has superior refractive properties when compared to normal types of optical glass. The use of this ED glass minimizes the amount of chro- matic aberration, resulting in a much more pleasing view when compared to telescopes that do not use ED glass.
6.Setting Up and Using the Equatorial Mount
When you look at the night sky, you no doubt have noticed that the stars appear to move slowly from east to west over time.That apparent motion is caused by the Earth’s rotation (from west to east). An equatorial mount (Figure 8) is designed to compen- sate for that motion, allowing you to easily “track” the movement of astronomical objects, thereby keeping them from drifting out of your telescope’s field of view while you’re observing.
This is accomplished by slowly rotating the telescope on its right ascension (R.A.) axis, using only the R.A.
Polar Alignment
For Northern Hemisphere observers, approximate polar align- ment is achieved by pointing the mount’s right ascension axis at the North Star, or Polaris. It lies within 1° of the north celes- tial pole (NCP), which is an extension of the Earth’s rotational axis out into space. Stars in the Northern Hemisphere appear to revolve around the NCP.
Dec.
|
|
|
|
|
|
| Dec. setting circle |
|
|
|
|
|
|
| |
|
|
|
|
|
|
| Dec. lock lever |
|
|
|
|
|
|
| |
|
|
|
|
|
|
| Front opening |
|
|
|
|
|
|
| |
|
|
|
|
|
|
| R.A. lock lever |
|
|
| Declination | ||||
|
|
|
| ||||
|
|
| Axis | R.A. | |||
|
|
|
|
|
|
| |
|
|
|
|
|
|
| control knob |
|
|
|
|
|
|
| |
Figure 8. The SkyView Pro mount.
8