Astronomy Tools

Browse all available astronomy tools.

Available tools

Angular Size From Diameter and Distance Exactplanartransversediskatanangulardiameter,degrees,diametercenterlineplaneperpendicularLOS;NOTsphericallimb2asin(R/d)orsmallangle. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Aperture Area cm² Optics Calculator Measured unobscured annular pupil area in cm², not nominal filled disk or eye-normalized throughput. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Aperture Area cm² Optics Practice Create reproducible practice for Aperture Area cm² Optics Calculator from supplied scenarios, returning validated questions and computed answers under the source tool's assumptions and limits.
Apparent to Absolute Magnitude Converter Extinction-corrected absolute magnitude in same passband, independent measured extinction not inferred from distance. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Apparent to Absolute Magnitude Practice Create reproducible practice for Apparent to Absolute Magnitude Converter from supplied scenarios, returning validated questions and computed answers under the source tool's assumptions and limits.
Approximate Comoving Distance From z Bounded 2048-panel Simpson quadrature in flat matter+Lambda Fried mann model, radiation/curvature omitted; angular-distance and lookback integrals are not interchangeable. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Approximate Comoving Distance from z Practice Create reproducible practice for Approximate Comoving Distance from z from supplied scenarios, returning validated questions and computed answers under the source tool's assumptions and limits.
Approximate Lookback Time From z Bounded 2048-panel Simpson quadrature in flat matter+Lambda Fried mann model, radiation/curvature omitted; angular-distance and lookback integrals are not interchangeable. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Approximate Lookback Time from z Practice Create reproducible practice for Approximate Lookback Time from z from supplied scenarios, returning validated questions and computed answers under the source tool's assumptions and limits.
Approximate Luminosity Distance From z Bounded 2048-panel Simpson quadrature in flat matter+Lambda Fried mann model, radiation/curvature omitted; angular-distance and lookback integrals are not interchangeable. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Approximate Luminosity Distance from z Practice Create reproducible practice for Approximate Luminosity Distance from z from supplied scenarios, returning validated questions and computed answers under the source tool's assumptions and limits.
Atmospheric Extinction mag/Airmass Differential same-passband atmospheric extinction against independent reference airmass, signed differences retained. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Atmospheric Extinction mag/Airmass Practice Create reproducible practice for Atmospheric Extinction mag/Airmass from supplied scenarios, returning validated questions and computed answers under the source tool's assumptions and limits.
B-V Color Index Temperature Estimator Ballesteros 2012 approximate temperature from independently dereddened Johnson B−V, bounded−0.4..2 for stellar-color proxy; not reddening inference. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Barlow Effective Focal Length Focal-length scaling from independently measured gain at actual Barlow spacing, not nominal device magnification always exact. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Barlow Effective Focal Length Practice Create reproducible practice for Barlow Effective Focal Length from supplied scenarios, returning validated questions and computed answers under the source tool's assumptions and limits.
Blue Hour Duration By Latitude Lookup Explicittoy eveningblue−6…−4°Sunwindowgeometricdurationfromactualindependentdeclination/latitude,not universalaestheticdefinitionor live ephemeris. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Bortle Class Sky Magnitude Lookup Independently verified site/observer/definition Bortle and limiting magnitude reference; ordinal class not an exact sky luminance. Exact independently verified context/edition key; not embedded or live reference data. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Celestial Equator Altitude By Latitude Uppermeridianaltitudecelestialequatordec0=90−|latitude|,not wholeequatorgreatcircle fixedaltitude. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Chandrasekhar Limit Checker Ideal zero-temperature relativistic electron-degenerate Chandrasekhar 5.83/μe²mass proxy; not exp los ion, rotation or actual stability prediction. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Circumpolar Declination Threshold By Latitude Geometriccircumpolarthresholdsamehemispheredec|δ|≥90−|φ|,boundaryhorizontangent,refractionexcluded. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Civil Twilight End Hour Angle Declaredcivil twilightgeometricSun−6°hourangle,notclocktimestamp/ephemeris/daylength. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Combined Binary Star Magnitude Calculator Stable additive same-passband unresolved binary magnitude; no magnitude arithmetic average. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Dawes Resolving Limit Arcsec Named empirical Dawes 116/Dmmclose equal-brightness visual binary criterion, not Rayleigh wavelength/diffraction or seeing resolution. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Dawes Resolving Limit Arcsec Practice Create reproducible practice for Dawes Resolving Limit Arcsec from supplied scenarios, returning validated questions and computed answers under the source tool's assumptions and limits.
Deep-Sky Sub Length Light Pollution Check Poisson background-variance/read-variance exposure criterion from independently measured same-filter background, not total saturation or optimal sub length. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Deep-Sky Sub Length Light Pollution Check Practice Create reproducible practice for Deep-Sky Sub Length Light Pollution Check from supplied scenarios, returning validated questions and computed answers under the source tool's assumptions and limits.
Distance Modulus Parsecs Calculator Geometric distance modulus 5 log 10(dpc)−5 without extinction. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Eddington Luminosity Limit Calculator Spherical radiative force/gravity balance 4πGMc/κwith independent applicable flux-mean opacity; not hydrogen-only fixed luminosity or actual accretion ceiling. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Eddington Luminosity Limit Practice Create reproducible practice for Eddington Luminosity Limit Calculator from supplied scenarios, returning validated questions and computed answers under the source tool's assumptions and limits.
Exoplanet Density g/cm³ Calculator Idealbulkplanetmean densityg/cm³spherefromactualmass/radius,not SI radius conversionor inferred composition. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Exoplanet Equilibrium Temperature Dec lared absorbed stellar flux reradiation-area convention (4 whole sphere,2 day side,1 sub stellar), unit emissivity, no greenhouse/actual surface temperature. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Exoplanet Period From Transit Spacing Transit timing linear fit with independently identified missing-cycle ordinals, not average adjacent gaps or automatic integer-cycle resolution. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Exoplanet Surface Gravity Calculator ActualidealNewtoniansphericalplanetgm/r²m/s²,not tablelookup/spin/effectiveatmosphericpressure or mass/radiusrelation. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Exoplanet Transit Depth Percent Unblended fully contained opaque planet across uniformly bright stellar disk; grazing, limb darkening and dilution external. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Eyepiece Exit Pupil mm Calculator Ideal visual telescope exit-pupil aperture/magnification; eye clipping and actual field illumination excluded. Model only, not an ephemeris, measured stellar identity or observational guarantee.
F-Ratio Image Brightness Factor Same extended-source radiance/detector/throughput irradiance ratio under f-number²model, not point-source aperture photon ratio. Model only, not an ephemeris, measured stellar identity or observational guarantee.
F-Ratio Image Brightness Factor Practice Create reproducible practice for F-Ratio Image Brightness Factor from supplied scenarios, returning validated questions and computed answers under the source tool's assumptions and limits.
Golden Hour Duration By Latitude Lookup Explicittoy eveninggolden−4…+6°Sunwindowgeometricdurationfromactualindependentdeclination/latitude,not universalaestheticdefinitionor live ephemeris. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Habitable Zone Inner Edge Calculator Caller spectrum/model independently verified two effective-flux boundaries; conditional HZ distance interval, not planet habitability or fixed universal solar limits. Model only, not an ephemeris, measured stellar identity or observational guarantee.
HR Diagram Position Classifier Independently verified HR diagram luminosity/temperature-region criteria with overlapping classifications retained; not actual evolutionary state from location alone. Independently declared positive evidence requirements; overlaps and unknowns retained. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Hubble Law Distance From Velocity Low-redshift linear Hubble distance with independently corrected peculiar motion and caller H0; signed velocity/distance retained, not cosmological inference for largez. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Hubble Time Age Estimate 1/H0 timescale in Julian Gyr, not actual cosmological age without expansion history. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Hubble Time Age Estimate Practice Create reproducible practice for Hubble Time Age Estimate from supplied scenarios, returning validated questions and computed answers under the source tool's assumptions and limits.
Jupiter Mass to Earth Masses Converter Explicit caller independently established Jupiter/Earth mass-unit convention, not confuse nominal GM ratio and actual masses/Guncertainty. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Light Gathering Power vs Eye Calculator Effective unobscured collecting area×independent throughput relative to eye pupil, not visual surface-brightness gain or photopic sensitivity. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Light Travel Time Calculator Compute how long light takes to cover a distance in a vacuum, in seconds and days.
Limiting Magnitude From Aperture Explicit independently calibrated limiting-magnitude aperture proxy, sky/observer/seeing matched by caller; no universal visual limit. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Lunar Phase Illumination Percent Distant-Sun spherical lunar illumination proxy from unoriented 0..180 elongation; phase age/waxing direction not determined. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Magnitude Flux Ratio Calculator Same-passband magnitude contrast converts to first/second flux ratio; brighter smaller magnitude. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Main Sequence Lifetime Calculator Caller calibrated fuel∝mass and luminosity∝mass^exponent lifetime proxy, not universal stellar evolutionary track. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Main Sequence Mass By Type Lookup Independently documented main-sequence spectral-subclass mass reference, metallicity/evolution spread not eliminated. Exact independently documented reference matching, signed discrepancy retained. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Max Central Eclipse Duration Minutes Lookup Independently verified eclipse type/geometry/catalog maximum duration record, not current-location eclipse prediction. Exact independently verified context/edition key; not embedded or live reference data. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Maximum Transit Altitude Calculator Uppermeridianmaximumaltitude90−|φ−δ|,signednegativealtitudesretained,not assume allstarstransitabovehorizon. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Mean Lunar Distance km Lookup Independently verified lunar mean/epoch distance convention, not instantaneous geocentric/topocentric range. Exact independently documented reference matching, signed discrepancy retained. Model only, not an ephemeris, measured stellar identity or observational guarantee.
MKK Luminosity Class Lookup Independently verified MK luminosity class descriptor, spectral classification not automatic radius/luminosity inference. Exact independently verified context/edition key; not embedded or live reference data. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Moon Age Days From Elongation Uniform synodic phase-clock age from ORIENTED 0..360 elongation and independent period; sky separation 0..180 alone cannot distinguish waxing/waning. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Moon Age Days from Elongation Practice Create reproducible practice for Moon Age Days from Elongation from supplied scenarios, returning validated questions and computed answers under the source tool's assumptions and limits.
Moon Apparent Size Perigee/Apogee Arcmin ExactSPHERICALlimb2asin(R/d)Moonangularsizeactualperigee/apogeedistances,not disk2atanor observedpercentageincrease. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Moon Phase Approximation Calculator Meanconstant29.530588853daysynodiccyclefromdeclaredJD2451550.1approxnewmoonanchor,NOT elongation-derivedage/trueeclipse/ephemeriscalculation. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Moonrise Delay Minutes Per Day Actual consecutive lunar-rise timestamp offsets from 24 hours, signed delays retained; caller confirms consecutive events, not universal 50 minutes per day. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Near-Horizon Refraction Arcmin Approximation DeclaredSaemundssonempiricaltruealtitude refractionapproxarcmin0≤h≤15deg,P/Tscaled;actualTRUEaltitude,no precisionhorizon/weather guarantee. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Neutron Star Density t/cm³ Estimate Spherical mean density,1 tonne/cm³=10^9 kg/m³, not neutron-star equation of state. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Neutron Star Density t/cm³ Estimate Practice Create reproducible practice for Neutron Star Density t/cm³ Estimate from supplied scenarios, returning validated questions and computed answers under the source tool's assumptions and limits.
NPF Rule Approximate Shutter Pixels Named simplified NPF(35 N+30 p)/(fcosδ) heuristic, bounded|δ|≤80°; no polar infinity, seeing/demosaicing/sharpness guarantee. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Opposition Brightness Enhancement Factor Same-passband measured opposition/reference flux contrast, no automatic causal opposition-surge attribution or universal planet factor. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Parsec to Light Year Converter Convert a distance in parsecs to light years.
Physical Size From Angular Size and Distance Inverseplanartransversediskangulardiameteratanprojection,0≤θ<180,no sphericalarcsinlimb/distanceinference. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Planet Day Length Lookup Independently verified planet sidereal/solar rotation sign and period convention. Exact independently verified context/edition key; not embedded or live reference data. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Planet Elongation Morning/Evening Classifier Signed east-of-Sun elongation convention: east evening, west morning; local altitude, twilight and observability not inferred. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Planet Escape Velocity Lookup Independently verified planet/reference surface-radius escape-speed convention. Exact independently verified context/edition key; not embedded or live reference data. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Planet Mean Density Lookup Independently verified planet mass/radius/epoch mean-density reference. Exact independently verified context/edition key; not embedded or live reference data. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Planet Moon Count Lookup Independently verified dated confirmed-moon inventory, not current live counts or candidate confirmation. Exact independently verified context/edition key; not embedded or live reference data. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Planet Surface Gravity Lookup Independently verified planet/reference surface or pressure-level gravity convention. Exact independently verified context/edition key; not embedded or live reference data. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Planet Year Length Lookup Independently verified planet sidereal/epoch orbital-period reference. Exact independently verified context/edition key; not embedded or live reference data. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Planetary Conjunction Separation Degrees Checker Actualalreadyindependentmatchedplanetdirectionvector greatcircleseparation/callerlimit,not conjunctiondateephemeris prediction. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Proper Motion Tangential Velocity Calculator Total tangent-plane proper-motion speed with AU/Julian-year coefficient; no radial component. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Pulsar Characteristic Spin-Down Age Pulsar P/(2 Pdot) characteristic spin-down timescale assumes braking index 3 and negligible birth period, not measured true age. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Redshift to Recession Velocity Converter Pure radial special-relativistic Doppler redshift inversion, supports blue shift z>−1; cosmological redshift not a unique SR velocity. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Rise/Set Hour Angle Formula Geometricrissethourangleatanarccosrelationfromindependentactualdec/latitude/crossingaltitude,retainsnever/alwaysflags,nodateephemeris. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Rule of 500 Astrophotography Shutter Caller explicit historical 500-rule exposure heuristic, not pixel-accurate star-trail tolerance or guaranteed sharp exposure. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Saros Cycle Eclipse Repeat Years Saros 223 synodic-month mean timescale from explicit matched period/count, not geographic eclipse-repeat prediction or exact calendar years. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Schwarzschild Radius From Mass Nonrotating uncharged Schwarzschild 2 GM/c²radius; not general spinning horizon radius. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Semi-Major Axis From Period Calculator Inverseidealpointmasstwo-bodyKeplerperiodsemi-majoraxis,centralμincludesactualtotalmass whenapplicable,not keplerperioddirection. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Small Angle Formula Arcseconds Calculator Restricted small-anglelinearθarcsec=D/d×206264.80624709636,D/d≤0.1,theoreticalerrornot exactatanor spherearcsin. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Solar Constant W/m² Lookup Independently verified measurement interval/reference-distance total-solar-irradiance record, not universal immutable solar constant. Exact independently verified context/edition key; not embedded or live reference data. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Solar Noon Equation-of-Time Correction Declaredlocalsolarnoonminutesafterlocalstandardmidnight=720−4(λ−λzone)−EOT,true-minusmeanEOTpositiveSunfast;DSTexcluded. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Spectral Class Properties Lookup Independently verified stellar spectral subclass/edition properties, type not inferred from one temperature. Exact independently verified context/edition key; not embedded or live reference data. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Star Count Limiting Magnitude Band Independently same-sky-coverage catalog cumulative star count vs limiting magnitude, not universal naked-eye count. Matched piecewise-linear observational calibration with no extrapolation. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Star Radius From Luminosity and Temperature Infer spherical effective blackbody radius from independently supplied bolometric luminosity/temperature. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Star Trail Length Pixels Per Minute SiderealrotationtrailRATEpixels/minute atactualdeclinationfixednontrackingdetectorlocaltangentplane,not generic observedmoving-sourcemotion. Actual independent model/unit/frame/epoch/calibration and applicable measurement established;not precise ephemeris,forecast,geodesy operation,identity or safety approval.
Stefan-Boltzmann Luminosity Calculator Spherical blackbody stellar bolometric luminosity 4πR²σT⁴, distinct from per-area emissive flux. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Sunrise, Sunset, and Daylight Calculator Estimate local apparent sunrise, sunset, solar noon, and theoretical daylight from the NOAA solar equations. The sunshine duration is the astronomical maximum, not observed cloud-adjusted sunshine.
Supermoon Size Increase Percent Check Actual angular diameter increase vs independently defined reference and caller screen; diameter not area, no universal supermoon designation. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Telescope Magnification From Focal Lengths Ideal visual telescope angular magnification from focal-length ratio, no usable-image or seeing guarantee. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Tidal Force Ratio Two Bodies Calculator Same local target differential tidal-gradient ratio M/r³, not ordinary inverse-square force ratio. Model only, not an ephemeris, measured stellar identity or observational guarantee.
True Field of View Eyepiece Calculator Rectilinear field-stop true-field angle, not approximate apparent-field/magnification under unknown eyepiece distortion. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Wien Peak Wavelength Calculator Wien displacement wavelength-radiance peak B_lambda, not frequency-radiance peak converted to wavelength. Model only, not an ephemeris, measured stellar identity or observational guarantee.