The Mighty Reflector

If you’re just starting out in astronomy, chances are someone has recommended a reflector telescope — and likely it was a Dobsonian. Dobsonians are a type of reflector telescope that uses a simple mount to operate and mirrors to gather and focus light. They are popular because they are inexpensive relative to their aperture (the size of the mirror), easy to set up and use, and provide great views of the night sky.

John Dobson revolutionized amateur astronomy in 1965 when he designed an affordable and simple alt-azimuth (alt-az) mount that made it easy to move the telescope up, down, left, and right. While Dobsonian telescopes are excellent for viewing the stars and deep space objects, they usually don’t come with computerized mounts. This means finding stars, planets, and galaxies is a manual process, which can be tricky for beginners.

Celestron Changes the Game

In 2020, Celestron changed the game by introducing StarSense Explorer Technology. This innovative system uses a StarSense Dock, a special bracket that attaches your smartphone to a StarSense Explorer reflector telescope. The dock holds the smartphone in place over a built-in mirror. The mirror reflects the star patterns in the sky into the smartphone’s camera, allowing the system to determine exactly where the telescope is pointed.

Celestron’s StarSense Explorer app then uses a technique called “plate solving” to analyze the star patterns and help guide you to celestial objects. This “Push-To” system is different from a motorized “Go-To” system, where the telescope moves automatically. While StarSense Explorer technology was a huge step forward, Celestron only offers this system with specific StarSense Explorer telescopes. Unfortunately, if you already own a standard Dobsonian, you can’t just buy the dock and app from Celestron to upgrade your telescope.

Meet AstroHopper!

AstroHopper is a free and open-source web application developed by Artyom Beilis, a software developer and amateur astronomer from Israel. Similar to Celestron’s StarSense Explorer system, AstroHopper helps users locate objects in the night sky by transforming a smartphone into a “Push-To” system.

AstroHopper works by using the smartphone’s gyroscope and gravity sensors to track changes in angle as you move the telescope. This method is similar to using digital setting circles but relies entirely on the smartphone’s sensors. AstroHopper is a progressive web application that works through a web browser and continues to function even when offline, as long as it is cached by the browser.

How to Setup and Use AstroHopper

Setting up AstroHopper is easy! Follow these steps:

1. Attach your smartphone to the telescope with the top part of the phone pointing in the same direction as the telescope’s eyepiece. Unlike sky observation apps that use the camera to simulate a view of the sky, AstroHopper works with the phone screen parallel to the telescope’s direction.
2. Open AstroHopper and calibrate the compass by moving your phone in a figure-eight motion. This improves the accuracy of the compass.
3. Align your telescope with a bright, easily identifiable star or planet near the object you want to observe.
4. Tap the “Align” button and then tap on the star or planet you selected. A 3-second timer ensures the phone is steady before confirming alignment.
5. Once aligned, tap on the object you want to observe. AstroHopper will show a line indicating the direction to move the telescope. It will also display the altitude and azimuth changes needed to align with the target.
6. Move the telescope until the altitude and azimuth values are close to zero. Your target should now be in view.
7. For each new object, repeat the alignment process, as smartphone gyroscopes lose accuracy after multiple movements.

Create a Permanent Installation of AstroHopper to Use Offline

AstroHopper can be installed as a regular application on your smartphone, allowing you to use it even without an internet connection.

To install AstroHopper:

• Open the URL AstroHopper
• Follow these steps based on your device:
  • Android/Chrome: Tap on “…” near the URL and select “Install App” or “Add to Home Screen.”
  • Samsung Browser: Tap on the ↓ symbol near the URL.
  • Android/Firefox: Tap on “…” near the URL and select “Install.”
  • Android/Edge: Tap on “…” at the bottom and select “Add to Phone.”
  • iPhone/Safari: Tap the “Share” button, scroll down, and select “Add to Home Screen.”

To test offline functionality:

1. Close all applications and browsers.
2. Put your phone in “Flight/Airplane” mode to disable Wi-Fi and data.
3. Tap on the AstroHopper icon to make sure it works properly without an internet connection.

Keep Looking Up!

AstroHopper is a game-changer for telescopes that don’t have a computerized “Go-To” or “Push-To” mount, offering the power of a “Push-To” system without the need for expensive add-ons. With a simple smartphone attachment and a free web application, you can easily navigate the night sky and find countless celestial wonders. Whether you’re a beginner or an experienced stargazer, AstroHopper makes exploring the universe more accessible than ever. So, grab your telescope, download AstroHopper, strap your phone to your scope, and keep looking up!

Clear skies and happy stargazing!