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Light pollution and the Bortle scale: reading your sky
The darkness of your sky matters as much as your telescope. Light pollution washes out faint objects, and the Bortle scale is the common way to describe how dark a site is.
What light pollution does
Artificial light scatters in the air and raises the brightness of the sky background. Faint objects like galaxies and nebulae are only a little brighter than that background, so as the sky glows more they fade into it and vanish. Bright targets like the Moon, planets and double stars are barely affected, which is why they are the mainstay of city observing.
This is why the same telescope shows far more from a dark rural site than from a town garden: the telescope has not changed, but the contrast against the sky has.
The Bortle scale
The Bortle scale runs from Class 1, a pristine dark site where the Milky Way casts shadows, to Class 9, an inner-city sky where only the Moon, planets and brightest stars show. Most suburban observers are around Class 5 to 7. Knowing your class sets realistic expectations for what deep-sky objects you can chase.
You can look up your Bortle class from a light-pollution map, and a drive of even half an hour to a darker class often transforms the view of faint targets.
Getting more from a bright sky
From a light-polluted site, favour bright targets, use a narrowband or light-pollution filter on emission nebulae, and let your eyes dark-adapt for at least twenty minutes away from white light. A red torch preserves that adaptation.
Aperture still helps in the city because it makes small bright objects brighter, but for faint galaxies the surest gain is a darker sky rather than a bigger telescope.
Match an eyepiece to your telescope
Open the Fit My Telescope toolFrame bright targets with the right eyepieceFind light pollution filter on eBayaffiliateRelated
Sources: Bortle scale (Wikipedia, CC BY-SA) ยท Light pollution (Wikipedia, CC BY-SA)