Comet Book2.7.5 - App Store

The Comet Book app clearly shows when Comets can be viewed and in which direction. The direction and elevation of a Comet can change noticeably in a day due to its fast apparent motion. The moon and a bright planet may be convenient as a guide to find the comet though they have large apparent motion, too.

This app determines where Comet is in the sky when it becomes visible at your observing site. You can easily start your observation of a Comet by using Comet Book as a guide to the direction and elevation of the comet.

In addition, the new “3D Solar System seen from Space” mode allows you to view the motion of Comets and planets turning around the sun. Please take a look the comet’s movement around our solar system.

Version History Some bugs have been corrected. 2.7.5 Apr 22 We have updated the app to support comet orbital-element eccentricities up to 10.0. 2.7.4 11/18/2025 Some bugs have been corrected. 2.7.2 09/20/2025 Addressed an issue where the comet list was not being saved. 2.7.1 08/31/2024 The COMET BOOK app now allows you to download comet orbital elements from the Minor Planet Center and select any comet to display. 2.7 08/07/2024 We have fixed an issue that was occurring on some devices. 2.6.1 04/05/2024 Some bugs have been corrected. 2.6 10/03/2023 Expanded the variable range of dates. 2.5.3 07/05/2022 The indication on the screen is disturbed with certain models of iPhones has been corrected. 2.5.2 05/29/2021 Some corrections have been made to mend inconvenience. 2.5.1 07/27/2020 The current local time button has been added to make it easier to find comet in the sky by holding the device over the head when you choose the comet. 2.5 07/22/2020 Comet's passing through date at perihelion or perigee is available for display on the screen.
When Comet passed the best time to view, the date you boot the app is set in the center of the Date and Time slide bars. 2.4 12/18/2018 Fixed that it was not possible to start up in Japanese and German modes. 2.3.1 05/10/2018 Comet Book is available in German language. 2.3 05/07/2018 Using the “3D Solar System seen from Space” mode will allow you to view the motion of Comets and planets turning around the sun. 2.2 03/29/2018 The program has been updated to meet the change of a data format of orbital elements for comet and some bugs have been corrected. 2.1 10/05/2017 The URLs of our support page were changed and some corrections have been made to mend inconvenience. 2.0.7 07/07/2017 Software update has been done and bug was fixed.
Tracking was not properly excuted when the direction of device was changed from vertical to horizontal. 2.0.6 01/02/2017 The APP is available for iOS 10.
The names of stars and constellations are enlarged in the star charts to improve legibility in the screen of iPhone. 2.0.5 12/21/2016 The problem that the orbital elements of comets might not be updated normally was corrected.
Aquisition of the orbital elements of Comet was changed to correspond with SSL. 2.0.4 04/05/2016 The problem that the orbital elements of comets might not be updated normally was corrected. 2.0.3 03/31/2016 The start up screen has been corrected.
The semicircular star chart shown in the previous versions is changed to the full frame star chart.
The scrolling of the star chart is improved to the make the motion of the star chart smoother on the display. 2.0.2 11/23/2015 The semicircular star chart shown in the previous versions is changed to the full frame star chart.
The scrolling of the star chart is improved to the make the motion of the star chart smoother on the display.
The background color of the star chart has been changed to a blue tint.
The APP is available for iOS9. 2.0.1 11/16/2015 It corresponds to iOS8. 1.3.1 01/24/2015 1. If Comet is selected, the illumination of unselected Comet is diminished in order to easily distinguish the selected one from others.

2. A swipe icon that allows you to scroll the star chart is set up on the lower right corner of the screen. If the double circles swipe icon appears on the screen, it allows you to swipe the star chart left and right in semicircular star chart screen.

The star chart can be moved up and down or left and right with a swipe in the full screen star chart.
Besides, the star chart can be zoomed in with a pinch gestures up to 5 times in the full screen star chart.

Tapping the swipe icon will change the screen from the star chart that synchronizes with a real view of night skies to the fixed star chart that does not follow your viewing direction, and vice versa. The present mode of the swipe icon will be switched each time the swipe icon is tapped.

If your on-line terminal unit does not have a function of electronic compass, the star chart is stayed with the swipe mode and cannot be switched to the other mode displaying your viewing direction.

3. The stars of 4.5th magnitude and brighter are displayed in the semicircular star chart and the stars of 6th magnitude and brighter are displayed in the full screen star chart. 1.3 12/17/2013