Astronomy
Resources
Telescope equations: http://www.rocketmime.com/astronomy/Telescope/telescope_eqn.html
Calculator and simulation of views: https://astronomy.tools/
Weather forecast: https://clearoutside.com/forecast/
Deep space: transparency is best (low magnification).
Planets and the Moon: seeing is best (high magnification)
Eastman Lake (Raymond, CA): Elevation: 453 ft (138 m)
Big Stump (Wilsonia, CA): Elevation: 6,070 ft (1,850 m)
Stellarium: http://www.stellarium.org/en/
Light pollution map: www.lightpollutionmap.info/
Central Valley Astronomers (CVA) http://cvafresno.org/ (President & Webmaster)
The choice of a telescope:
What to consider:
The location. It will determine what it is possible to observe in relation to the light pollution. In an urban area, it will not be possible to see many deep sky objects. If the location does not allow good observations, it is necessary to think about a telescope that can be transportable, i.e., that can be easily put into a car. If you have lots of light pollution and you cannot/dont want to drive, then the choice will be limited to the moon and planets (Jupiter and Saturn).
If you don't know a dark place where you can clearly see the milky way, then the views will be limited to planets and very few other objects.
The visual targets. Planets and/or deep sky objects (e.g. Messier objects). It leads to the choice of the telescope and the eyepieces.
Visual observation and/or astrophotography. It leads to the choice of the mount.
The price.
What can be observed: if it can be distinguished, it is considered as seen and you should be happy to have seen something, so even a blurry faint blob in the sky represents something relevant.
The balance between the different parts: telescope, eye-piece, and the mount mount.
Alternative to Goto/computerized telescope: with eyepieces with a large field of view (e.g., 32mm), use free apps on your phone to get the coordinate of the objects to observe (altitude+azimuth), orient the telescope following the azimuth, use an inclinometer app, place the phone/tablet on the telescope to adjust the altitude.
Simulated view of Andromeda (M31) with an 8 inch reflector with a suburban sky (no moon):
Budget choice for visual observation only:
Mak 90 mm (3.54 inches) (example: Celestron C90)
Dobson 8 inches (203 mm) (example: Orion XT8)
Characteristics:
Catadioptric - Maksutov-Cassegrain
focal length=1250mm
aperture=90mm
f-ratio=13.9
Good details of the Moon, bands of Jupiter, ring of Saturn
Very limited for deep sky objects, can split many double-stars.
Small, grab-n-go, can "work" with a photo tripod.
Works also as a spotting scope with the 45 deg diagonal.
Magnification (up to x150)
Price under 200 USD.
Characteristics:
Reflector
focal length=1200mm
aperture=203mm
f-ratio=5.9
Good details of the Moon, bands of Jupiter, ring of Saturn.
Magnification between x100 and x200. (12mm to 6mm eyepieces)
Possible to use for deep sky objects (with a clear sky, no moon, no light pollution).
Magnification x50 (24mm eyepiece).
Transportable (can fit on the back seat of a sedan car) best trade off between aperture/price/transportability.
Magnification (up to x400)
Price under 400 USD.