Telescope Performance
🔭 Dawes' Limit (Resolution)
The theoretical resolution limit for a telescope of given aperture.
👁️ Light Gathering Power
How much more light your telescope gathers compared to the dark-adapted human eye.
⭐ Limiting Magnitude
Faintest star theoretically visible with your telescope under perfect conditions.
📐 Magnification
Maximum useful magnification is typically 2× aperture (mm).
🎯 Exit Pupil
Optimal exit pupil for most viewing is 2-6mm. Below 1mm wastes light.
🌌 True Field of View
The actual sky area visible through your eyepiece.
Astrophotography
📸 Image Scale (Pixel Scale)
Arcseconds per pixel. Match to seeing (1-4 arcsec typical).
🖼️ Field of View (Camera)
Total field of view your camera/telescope combination captures.
📊 SNR Calculator
Higher SNR = better image quality. SNR > 10 is typically detectable.
⏱️ Exposure Time for SNR
Time needed per sub-exposure to reach target SNR.
🔢 Integrated SNR
🔗 Stacking Calculator
📷 Dynamic Range
📡 Sub-Exposure Calculator
Maximum sub-exposure before sky dominates noise.
🔦 Photon Noise Calculator
🌡️ Narrowband Doppler Shift
Redshift/blueshift for narrowband targets. Use negative for blueshift.
🎨 Narrowband Filter Bandwidth
Filter tolerance for imaging moving targets.
Observing Conditions
🏔️ Air Mass
At horizon = ∞, at zenith = 1. Expect extinction above 2-3 AM.
🌡️ Extinction (Magnitude Loss)
Light lost due to atmospheric scattering.
👁️ Seeing Conditions (FWHM)
Image quality limited by atmospheric seeing.
📏 FOV for Objects
How many times an object fits across your field of view.
Star & Brightness
✨ Magnitude Difference
Each magnitude = 2.512× brightness difference.
🔗 Binary Star Combined Mag
Visual magnitude when both stars are unresolved.
📡 Point Source Detection
Estimated S/N for detecting a point source.
🎚️ Bortle Scale to Sky Brightness
Visual sky brightness for given Bortle class.
Eyepiece & Camera
🔍 Eyepiece True FOV
📷 Camera Detector Size
True focal length accounting for crop factor.
⚖️ Barlow/Traveler Magnification
New magnification with Barlow or reducer.
📐 Focal Ratio Calculator
Lower f/ratio = faster scope = more light per area.
Sun & Solar
☀️ Solar Filter ND Required
⚠️ NEVER look at the Sun without proper solar filtration!
🌞 Solar Angular Size
Varies from 31.5' (aphelion) to 32.5' (perihelion).
🎯 Solar System Objects Angular Size
Planetary
🪐 Planet Angular Size
Angular diameter of planet at given distance.
💡 Planet Magnitude
Planet magnitude at current distance vs reference.
🌅 Planetary Elongation
Angular distance of planet from Sun. Best viewing when >30°.
📐 Angular Separation
Angular separation between two celestial objects.
☄️ Comet Brightness
Predicted magnitude using m = m₀ + 5log₁₀(r) + k(1 - r/q) with q=1.
Timing & Location
⭐ Star Trail Exposure (500/400/300/200)
Maximum exposure before noticeable star trails at given focal length.
📅 Julian Date Converter
🧭 Altitude & Azimuth
📷 Downsampling Calculator
Ideal sampling is ~1-2× seeing (typically 1-2 arcsec/px for seeing-limited). For lucky imaging, 0.5"/px or less is better.