What’s the best telescope to use under light pollution?

BBC Sky at Night Magazine's Scope Doctor Steve Richards solves your astronomy ailments.

The lights from towns and cities can blot out views of the night sky. Credit: iStock

I live in San Juan, Puerto Rico and would like to observe from my ninth-floor balcony. Can you recommend a telescope for a city environment?

Steve says: “There are two main types of light pollution: sky glow and local source. Sky glow is the orange glow caused by the many light sources in a city; local source is light from, say, a single streetlight or a neighbour’s house.

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Your choice of telescope should be based on the same criteria that you’d use for a dark observing site.

A large aperture instrument will collect more starlight than a small aperture regardless of the ambient light conditions so it will pay to buy the largest aperture that you can afford.

But in your case, living up on the ninth floor, this choice needs to be tempered with consideration for storage at your home and carrying the gear to and from your apartment.

There’s a strong argument for buying a Go-To mount as the light pollution in Puerto Rico will make it more difficult to select suitable stars for manual star hopping to celestial objects.

You need to strike a compromise here and an 8-inch Schmidt Cassegrain from either Celestron or Meade, mounted on an altazimuth Go-To mount would give you a good aperture in a compact format.

Adding an extended light shield to the front of the telescope would not only reduce the risk of dew but would also help to reduce the interference from local light sources.

Also get a good pair of 10×50 binoculars so you can get quick views of the night sky.”

Some more useful guides that might help:

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Email Steve your astronomy queries to contactus@skyatnightmagazine.com and they could be answered in a future issue of BBC Sky at Night Magazine.