Astronomically, you can se the moon, the sun ( if properly filtered ), all of the planets except for Pluto, some surface detail on Mars, Jupiter, and Saturn, multiple stars, globilar and open clusters, bright nebulae, galaxies, and nearby galaxy clusters. Terrestrially, there is wildlife, sports, etc.
Yes and no. Bright objects such as the moon, some planets and star clusters will show colours and features just like the photographs. Faint objects are more difficult.Your eyes are not sensitive enough to detect colour at very low light levels, and even bright nebulae will appear as shades of grays and greenish hues. Colour films can be exposed long enough to collect light across the visible spectrum so photographs show the colours that you do not see visually.
A telescope has three types of power which is measured against the performance of a normal human eye. They are: a) Magnifying Power, b) Light Gathering Power, and c) Resolving Power. All three are important, but the most important is the “Resolving Power”. The longer the focal length of a telescope, the more a particular eyepiece will magnify the image. However, there is a practical magnification limit of 2X per mm of telescope aperture. Using an eyepiece which gives a magnification beyond that limit is of little use. The amount of light that a telescope can gather depends on the size of the apertureand the more light that can be gathered, the better the resolution. What you will see through your telescope will then depend on these three powers. For example, compared to the human eye, and using the 2X per mm rule, a 150 mm aperture telescope will have a maximum power of 300X, a light gathering power of 600X, and a resolving power of 0.8 arc-seconds.
The larger the aperture, the higher the practical magnification limit. Since more light is collected and brought to focus by a larger aperture telescope, fainter objectscan be seen with it than with smaller apertures. Under good seeing conditions when air is not turbulent, a larger aperture objective gives higher resolution, letting you see finer details.
For standard eyepieces with a 50 degree apparent field of view, the Plossl eyepieces are a good choice if your telescope’s focal ratio is f-7 or less. For longer f-ratio instruments, simpler eyepieces such as Kellners will be sufficient. Choose eyepiece focal lengths that wont give you a duplicate magnification when a Barlow lens is used. For example, do not buy a 10 mm and a 20 mm eyepiece with a 2X Barlow.
A motor drive is necessary for many for many types of astrophotography, and it is more than just a convenience for visual observing. At 200X magnification, the Earth’s rotationwill move an object out of your field of view in about five seconds. A Right Ascension ( R/A ) motor drive will keep an objectin the centre of your field where the image is the best without producing the objectionable vibrations experience when tracking manually. Adding a Declination ( DEC ) motor drive and a hand controller allows you to guide for astrophotography.
How do I find objects in the sky?
The sky is mapped out in a spherical coordinate system similar to to the system of Latitude and Longitude on the surface of the Earth. On the imaginary celestial sphere, the coordinates are Declination, which is the equivalent to Latitude, and is measured in degrees, while Right Ascension is the equivalent to Longitude,and measured in hours. The celestial equator is a projection of Earth’s equator onto the celestial sphere. Because the positions of the stars and other distant celestial objects, as plotted on this celestial sphere , change very slowly with time, their listed coordinates are updated every fifty years. On the other hand, planets change positions so rapidly that their coordinates must be obtainedfrom current astronomy periodicals. The setting circles on your equatorial mount can be aligned with the celestial sphere to aid in finding astronomical objects.
What do I need to take photographs through my
telescope?
Most telescopes can be adapted to act as lenses for single lens reflex ( SLR ) cameras. For the basic technique of “prime focus” photography, all you generally need are a camera body, a T-ring specifically made for your camera body ( this allows it to connect to a T-thread) and in some cases a combination Camera Adapter Tube designed for your telescope. This configuration is fine for terrestrial use, for the moon, or for the sun if correctly filtered. For fainter astronomical objects you will need to do time exposures using an equatorial mount with a Right Ascension motor to correct for the Earth’s rotation. For exposures longer than a few seconds, you should use a dual axis motor drives and a hand controller to guide the telescope.
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