Northern Polar Alignment
By owning an equatorial mount, you’ll find yourself in the situation to perform a polar alignment to your mount each time you assemble your equipment prior an observation. However, apart from using the setting circles and calculating the polar star position manually, there are a few phone apps worth mentioning that would save you a great deal of time. Before phones and tablets entered our lives amateur astronomers relied on printed paper sheets including an approximate to the polar position reticle sky chart that resembles the finder scope reticle chart in your mount.
Today’s phone apps are able to locate your exact position through the phone’s built-in GPS ability including the exact time and thus calculate more accurately than before the current polar star position allowing you to do a finer alignment to your scope mount.
I will mention three phone/tablet apps starting with the old classic PolarFinder (http://polarfinder.com/) that also exist as Windows and Linux programs available on their website. A version for Mac and Windows phones is on the way *thumbs up*
This app was the very first one that appeared at Play Store but I never succeeded making the reticle image cover up the entire screen as shown in the screenshot. Also its not very obvious in the reticle as where the polar star should be located at.
Northern Polar Alignment
This is a much simpler version of polar finder that supports only the northern hemisphere. You have to set date and time zone manually as well as your longitude every time you enter the app. It has some static text with information on the screen and it doesn’t look overly impressive by any means. It wouldn’t be my first choice or recommendation to anyone in comparison to what is available out in the app stores.
The next app is called PolarFinder developed by Jótzef Lázár and is in my opinion the best choice so far. It uses GPS just as the previous app but has many more options to choose from than any of the previous apps so far.
The best function is that you can change reticle types to ressemble the reticles in the most known mount types. These are Ioptron, Astro-Physics, Losmandy, Skywatcher, Takahashi, Vixen, AstroTrac and StarAdventurer.
The longitude can either be entered manually, or acquired through the phone GPS. You can adjust the markers distance, night mode, date format, star sizes and hemisphere location (north/south).
The image orientation option is greyed out when you choose among telescope types and enabled when you use the “Built-in” reticle type.
AP Polar Align
For the windows phones and tablets out there you’ll find this neat app that by default in night vision mode. You can choose to either allow the phone enter your GPS location or enter it manually. The night vision brightness is adjustable through a slider and the reticle is very easy to understand. A double tap on the reticle image zooms in for more detail. I would say this app is neat and has a very clean layout. Finally, this app is found for free in the Windows Store.