Tips and Tricks
Marking with luminous paint:
As noted above in the section about assembly it is very helpful to mark the positions of the altitude
wheels and the trusses. This helps when assembling the telescope at night and keeps collimation issues at a minimum.
We also recommend marking your screws with a patch of luminous paint because it makes finding lost parts a lot easier to find
when dropped in the grass and often makes it unnecessary to use a flashlight, which would disturb the night vision of other
observers.
Image orientation:
You may have noticed that objects appear to be upside down and mirrored in your telescope. This is the case
in almost every astronomical telescope and does not cause any problem during astronomical observations. Because of the Earth’s
rotation all objects seem to drift across the field of view. To compensate this movement you have to move the telescope smoothly
and slowly. The higher the magnification the more accurate this tracking movement has to be. Another solution is to place the
object on the eastern rim of the field of view and let it drift across the field, then reposition it on the eastern rim again. However –
this method only works with good eyepieces that are delivering a sharp image up to the edge of the field.
Vibrations:
Try to avoid touching the eyepiece during observations. Touching the eyepiece and the slight shiver of the hand will
cause unsteady views.
Night vision:
Give your eyes some time to adapt to the darkness. This takes about 20-30 minutes after an exposure to a bright
light – even if it is a short exposure. Use a dim light with a red filter to read star charts or draw objects – dim red light does not
influence your eye’s adaption very much.
Horizon viewing:
Planets and other objects that are close to the horizon are severely influenced by air movement and
absorbance. It is much better to time your observations in a way that those objects are close to the meridian, so that they are on
their highest position possible. If the image is dim or moving fast, use a smaller magnification. Using too much magnification is a
mistake that is made very often by beginners.
Warm Clothing:
Even in the summer the nights may get very cold during clear nights, especially on the mountains. Always
remember to bring warm clothing like thick jackets, beanies, gloves, winter shoes and thick socks – even if your were sweating
during the day. It is hard to enjoy even the best night when you are freezing!
Explore your observing site during the day:
The ideal site should be far off of frequently used streets and other light sources
that would prevent your eyes from adapting to the dark. Keep in mind that it is likely to get foggy in the vicinity of open water, such
as river valleys or lakes. The ground should be solid and relatively flat. You can observe in the city, but try to get to a place some
distance away, where you can see the Milky Way if possible. You can get really good conditions as close as 50 km outside of
cities. If relocating to a more rural area is not a possibility, try to position your scope away from as many artificial light sources as
possible. An old astronomers quote says: “ You cannot really replace a dark sky by anything than a darker sky”
Calculating magnification
The magnification that a telescope gives you at the sky is determined by two factors: The focal length of the telescope and the
focal length of the eyepiece. You will find the focal length of almost all eyepieces written on the eyepiece body.
The magnification is determined by the following formula:
Magnification. = Telescope focal length divided by eyepiece focal length
For example, a 12” dobson and a 24mm eyepiece:
Magnification. = 1525mm/24mm = 64x
The eyepiece type, like Modified Achromatic, Plössl or Super Plössl, does not have any influence on the magnification, but
determines other optical properties like apparent field, chromatic error correction and flatness of the field of view.
The maximum usable magnification is about two times the diameter of the aperture in millimeters. However, in nights of bad to
average seeing much lower magnifications will produce a more detailed and steadier image. High magnifications should only be
used during periods of extremely steady air on special objects, like double stars. When you are starting to observe an object,
always start with a low magnification. Then center the object in the field of view and focus with care. Now you can try a higher
magnification. When the image is becoming fuzzy or is moving, go back to the last magnification. Atmosphere – and thus seeing
conditions – is always changing. Please notice that a sharp image at a low magnification will show you more than an over-
magnified fuzzy view.
Содержание Truss Tube Dobsonian Series
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