Reference charts
Dense tables, kept accurate and kept specific. Each of these exists because the figure is one people look up repeatedly and rarely find stated plainly, with the formula shown rather than hidden.
8 pages in this section
- Exposure Time by Focal LengthUntracked NPF-rule and 500-rule exposure limits from a 14mm lens to a 2032mm telescope, plus what a star tracker or equatorial... Open →
- Eyepiece Focal Length to Magnification ChartA chart converting eyepiece focal length to magnification across common telescope focal lengths from 400mm to 2032mm, plus exit... Open →
- Maximum Useful Magnification by ApertureA full chart of maximum useful magnification by telescope aperture in mm and inches, with the realistic seeing-limited ceiling... Open →
- Messier Object Visibility by ApertureWhat the classic Messier objects actually look like through binoculars, an 80mm, a 130mm, a 200mm, and a 250mm-plus telescope... Open →
- Mount Payload by Telescope WeightReal telescope tube weights from the spec database checked against the 100 percent visual and 50 percent imaging mount payload... Open →
- Planet Viewing by ApertureWhat Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune and the Moon actually look like at 60mm through 250mm and up, with... Open →
- The Bortle Scale, Explained with a ChartThe full 9-class Bortle scale with naked-eye limiting magnitude, sky brightness, and what each class means for your telescope, plus... Open →
- What You Can See by Telescope ApertureWhat each telescope aperture band, from under 80mm to 300mm and larger, actually shows of the Moon, planets, double stars and deep... Open →
Start here if you are new
- How to choose a telescope, the whole decision in one page
- Complete builds at three budgets, with running totals
- Magnification calculator, the number everyone gets wrong
- What you can see by aperture, honestly