Privacy Policy

Messier Catalog: The Greenberg Companion

Effective 28 July 2026

This app does not ask for your name, your email address, or any account. It does not track you, does not contain advertising, and does not sell or share anything about you with anyone.

Who this policy is from

This app is published by Chanan Greenberg, trading as Greenhawk Observatory. Contact details are at the bottom of this page.

Information the app does not collect

The app has no sign-in, no user accounts, and no user profiles. It does not collect or transmit:

• your name, email address, or phone number

• your location

• your contacts, photos, calendar, or files

• any analytics about how you use the app

Information stored on your device

The app lets you mark each Messier object as observed or imaged. Those marks are saved only in the app's own storage on your phone or tablet. They are never sent anywhere, and nobody but you can see them. If you delete the app, they are deleted with it.

Notifications

The app can send occasional announcements, for example when a new astrophotograph is published. This uses Firebase Cloud Messaging, a service provided by Google.

When you install the app it subscribes to a single public announcement channel. Messages are broadcast to that channel and reach every installation at once. No message is ever addressed to you individually, and the publisher receives no list of recipients, no identity, and no contact details.

To deliver a message to your device, Google issues that installation an anonymous registration token. This is handled by Google and is described in the Firebase privacy documentation and Google's privacy policy. The publisher does not access, store, or use it to identify anyone.

You can turn notifications off at any time in your device settings, and the rest of the app continues to work normally.

Links to other websites

Some objects include a link to that object's page on the NASA or Hubble website. Tapping it opens your device's own web browser and leaves the app. Those sites are operated by others and have their own privacy policies. This policy does not cover them.

Working offline

All 110 images and all accompanying text are included in the app itself. Everything except the notification service and the external links works with no internet connection at all.

Children

This app is not directed at children under 13, and it does not knowingly collect information from anyone. Because it collects no personal information from any user, no information about a child is collected either.

Changes to this policy

If this policy changes, the revised version will be posted on this page with a new effective date. Material changes will also be announced in the app.

Contact

Questions about this policy, or about the app, can be sent via the contact page of this website.

Chanan Greenberg · Greenhawk Observatory · greenhawkobservatory.com