Twinkle Clock vs Astral Book
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Twinkle Clock
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Twinkle Clock turns your screen into a night sky — a clock face made of twinkling stars and constellations. FREE • 12 zodiac constellations, swipe to switch • A twinkling starfield with the time overlaid on constellation lines PRO (one-time purchase) • All 88 official constellations • ~8,900 naked-eye stars across the whole sky • The Milky Way and the Moon & planets (Mercury–Saturn) • Nebulae, star clusters, and galaxies • Tap any star, the Moon, or a planet to read about it • Time Travel — pick any date and time to see what the sky looked like (or will look like) • Major meteor shower activity windows Available on iPhone, iPad, Mac, Apple TV, and Apple Vision Pro.
Astral Book
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The easiest way to log your stargazing sessions. Astral Book is an astronomy observation journal for amateur astronomers. After each session at the eyepiece, record your targets, seeing, transparency, equipment, and photos — all in one place. No internet needed, even at remote dark sky sites. 【What You Can Do】 ▷ Observation Log Record object name, object type (planet, moon, star, nebula, cluster, comet, meteor & more), date/time, location, seeing (1–5), transparency (1–5), notes, and photos. Search and filter past sessions by object, notes, date, location, or equipment. ▷ Calendar View See which nights you observed on a monthly calendar. Swipe to browse months and revisit your history at a glance. ▷ Target List Add objects you want to observe. Log a session for any target and it's automatically marked as done and removed from the list. ▷ Messier Catalog Browse all 110 Messier objects. Observed objects are automatically checked off so you can track your Messier completion progress. ▷ Same Object History From any log entry, quickly see every time you've observed the same object — when, where, and under what conditions. ▷ Observation Sites Save your favorite dark-sky sites with Bortle scale ratings. ▷ Night Mode Switch to a red-tinted theme that protects dark adaptation while you're at the eyepiece. ▷ Observation Card Sharing Generate a visual observation card and share it via social media or messaging. ▷ CSV / ZIP Export & Import (Free) Export observations as CSV. Create a ZIP backup with photos, sites, equipment, and wish list. Restore from a previously exported CSV or ZIP. ▷ PDF Export (Free) Export your observation journal as a PDF report to share or print. ▷ Equipment Management (Pro) Register your telescopes, eyepieces, and cameras, then link them to your logs. One place to see what you used to observe what. ▷ Saved Gear Sets (Pro) Save favorite telescope + eyepiece + camera combos as templates so logging a session takes one tap. ▷ Observation Statistics Charts for total sessions, unique object types, monthly session counts, and sessions by site — see your observing patterns over time. 【Who It's For】 ・Observers tired of notebooks or notes apps with no search or statistics ・Visual observers who want to properly track seeing and transparency ・Observers who want to review results by telescope or binoculars ・Messier catalog chasers tracking their progress ・Anyone keeping a "next target" wish list ・Astronomy club members sharing observation reports ・Observers at multiple sites from backyard patio to remote dark sky 【Your Data Stays With You】 All data is stored locally on your iPhone/iPad. Nothing is sent to the cloud or any external server. No account required. No risk of losing years of records if a service shuts down. Use ZIP backup to move data when changing devices. 【Fully Offline】 Works completely without internet at remote dark-sky sites. No connection required (except during in-app purchase processing). 【Pricing】 ・Free: up to 20 observation logs (includes CSV / ZIP / PDF export & import) ・Astral Book Pro (one-time purchase): regional pricing — unlimited logs + equipment management + gear sets One purchase. No subscription. No recurring fees. ——— Developer: Kore Apps Support: support@kore-apps.com ———
Screenshots
Verdict
The clearest difference is update cadence: Astral Book at weekly against Twinkle Clock's every 3 weeks. Astral Book also leads on iOS requirement (15.0 vs 17.0). On price, ads, in-app purchases and device support there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Twinkle Clock sells 1 one-off in-app purchase and Astral Book sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.
Twinkle Clock ships an update every 3 weeks, Astral Book weekly. The most recent releases landed on October 27, 2026 and October 24, 2026 respectively.
| Parameter | Twinkle Clock | Astral Book |
|---|---|---|
| Price | Free | Free |
| Update frequency | Every 3 weeks | Weekly — better |
| Ads | No | No |
| In-app purchases | Yes | Yes |
| Devices | iPhone, iPad, Mac, Vision Pro — better | iPhone, iPad, iPod |
| Requires iOS | 17.0 | 15.0 — better |
| Further details — not scored | ||
| Size | 23 MB | 55 MB |
| Age rating | 4+ | 4+ |
| Developer | Hiroyasu Hirai | kazuki korenori |
In-app purchases
Twinkle Clock
- Twinkle Clock Pro$24.99
Astral Book
- Astral Book Pro$5.99









