Polar Scope Align 4‏+

Polar Scope Align will calculate the position of Polaris or σ Octantis in your Polar Scope reticle for your location (using your phone's GPS or manually), allowing a quick and accurate polar alignment. It is one of the few programs that are accurate in lower latitudes by correcting for atmospheric refraction (so expect results to agree only with precise software and not most simplistic "polar align" apps - see the "Accuracy" section in help for details). It will even allow you to measure and correct a centering error of the reticle. In the settings you can select from a vast collection of reticles, one that matches your own. Pretty much every reticle in the market is supported:
iOptron old & new, Astro-Physics RAPAS & PASILL, various versions of Takahashi EM-10/11/200/400/500, NJP, PM-1, P2-Z, the latest Orion / Skywatcher, the Classic Skywatcher / Orion / Celestron / Meade / EXOS2 / Bresser, the Telrad, Rigel QuikFinder, a couple for Astrotrac / Losmandy / Kenko / Avalon, the Vixen Atlux/SX/SXD/SXP/AXD/GP/GP-DX/Polarie Polar Axis Scopes, a Konus and several Polar Finders: Tuthill, Explore Scientific 8x50, Meade 9x60, Vixen Polaris, Celestron 7x50, Carton Optical. PoleMaster help view for South Hemisphere users.
Feel free to contact the developer with any questions, feature/reticle requests and any problems you have with the app. If you like Polar Scope Align, please consider leaving a review on the app store.

Main features:

-Accurate calculation of Polaris or Sigma Oct for any date and location, including effect of atmospheric refraction (and annual aberration, nutation). Most other apps do not perform precision calculations, so please only compare app readings to accurate sources (USNO, scientific software etc).
-Automatic Time/Location.
-Calculation and correction/compensation for off-center reticles.
-Remember zero position on Celestron / Skywatcher / Orion etc reticles.
-Full app in red-color night mode.
-Moon phase.
-Messier, Caldwell and Bright star database.
-Download and explore DSS color images of the DSO database entries.
-8 calculators useful for observing and astrophotography.

This free version is ad-supported. You can also try the ad-free Pro version with many extra features:

-Ability to manually enter time/date and location (including saving favorites, list of recent locations, loading from world location database, searching online).
-Zoomable reticle view.
-Approximate daytime / no polarscope polar alignment tool. Great for visual use, solar imaging (including eclipses) and even limited short focal length astrophotography. Now with sun shadow calibration for more accuracy!
-Alt-az alignment error display for mounts that calculate it after star alignment (e.g. iOptron iEQ45, CEM60).
-Polar alignment when your scope is not in zero position (for mounts on which you can always access the polar scope).
-Lunar Calendar with solar/lunar rise/set and twilight times.
-Bubble level (using either gyro or accelerometer) and Compass heading, as well as magnetic declination reading.
-GPS accuracy & elevation data.
-Switch to alternative night mode colors, or daytime mode for the tools.
-Red/White/LED light control.
-Deep Space Object Database with 22000+ objects from several catalogs (Messier, Caldwell, NGC, IC, Herschell 400, Sharpless 2, Barnard), along with stars (Yale Bright Star) & planets. The database is searchable and fully configurable with filters, various sorting methods etc.
- Get help finding the DSO Database objects with your non-goto telescope with the Push-To function.
-Connect to and control WiFi-enabled iOptron mounts.
-Over 30 calculators useful for observing and astrophotography, from eyepiece magnification and field of view, to imaging resolution and reducers.
-World astro-weather report based on data from 7Timer!, Met.NO & more.
-Water vapor satellite images.
-Solar Eclipse Simulator.
-List of visible ISS and bright satellite passes.
-iOptron Named Star list, Meade LX200 star list.
-Screen dimming.