Deep Sky Finder Calculator
Estimate how many galaxies, nebulae, and star clusters are observable with your telescope from your location.
Inputs
Results
Total DSOs
289
How to Use This Calculator
- Enter Telescope Aperture (in), Naked-Eye Limiting Mag, and Latitude (°N).
- Set Month (1-12).
- Review the Total DSOs result.
- Use Galaxies and Nebulae to inform your decision.
- Use the chart to visualize the results and explore different scenarios by adjusting inputs.
How the result changes with Naked-Eye Limiting Mag
| Naked-Eye Limiting Mag | Total DSOs |
|---|---|
| 2.55 | 121 |
| 3.92 | 200 |
| 5.58 | 294 |
| 6.95 | 372 |
What each input means
- Telescope Aperture (in)
- Diameter of your telescope's primary mirror or lens in inches
- Naked-Eye Limiting Mag
- Faintest star visible to naked eye from your site (5.5 = suburban, 6.5 = dark rural)
- Latitude (°N)
- Your geographic latitude (positive = north, negative = south)
- Month (1-12)
- Observing month — different DSOs are visible in different seasons
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersTelescope Aperture (in) = 8, Naked-Eye Limiting Mag = 5.5, Latitude (°N) = 40, Month (1-12) = 6 = 4 input(s) provided
- Calculate GalaxiesGalaxies114 = 114
- Calculate NebulaeNebulae58 = 58
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