Help

This page explains every part of Zenigo. New here? Getting started walks you through the first night step by step.

The screen

Directions at the top: How many degrees to turn the telescope left or right (azimuth) and to tilt it up or down (altitude) to reach the target. The line below shows the distance to the target and where the position comes from. Tap that line to choose another target; the small ✕ next to it clears the target, so the red ring, the arrow and the directions disappear. Before the first locate it shows how high the target stands and in which direction.
Map or image: The camera image or the star map, with stars, constellation lines, names, Messier objects, planets and the horizon with the cardinal points. The orange crosshair is where the telescope points; map and image are shifted so that it always stays in the middle of the screen, even when the phone sits crooked on the tube, the red ring is the target and the red arrow shows the way to it. Green circles mark the stars recognised in the last image.
Menu (top right): The pill with the Z logo opens the menu: solve a photo, sky map, filter, settings, the current position, Tonight for your location and links to this help. Links marked with an arrow open another website in a new tab. On phones, menus and panels slide up from the bottom and can be swiped down to close. On tablets and computers they open at the right side and float over the map, which stays where it is; the buttons move next to the panel; close them with ✕ or the Esc key.
Status (bottom left): What the app is doing or has done, for example “Solved · 42 stars · 0.8 s”, and below it the source: live camera, photo or sky map, and whether it follows the compass or the motion sensor. Active extras appear here too: a compass correction or a filter. Their ✕ switches them off.
Gestures: Pinch or double-tap to zoom, drag to pan or, on the free sky map, to look around. Tap a star, planet or Messier object for its details.

Buttons

The round buttons on the right. A dimmed button can’t be used right now; tap it to see why.

Quick settings: The settings you change at the telescope: pointing (camera or top edge), location with GPS, red light, which camera, the eyepiece in use and the eyepiece view, eyepiece point and compass correction with one-tap reset, and button labels. All settings opens the full settings.
List: Your observing list for tonight; the number shows how many objects are still to do.
Find target: Choose what you want to look at: quick picks, a list of what is well placed now (higher than 15°), or search by name, Messier number or star name.
Filter: Choose what the map shows. Lights up while a filter is active. See Filter.
Eyepiece point: Tell the app where the telescope points relative to the phone. Available after a locate, or with Align on the map. See Eyepiece point.
Continuous: Locates again and again by itself while the camera runs. After the first solve each further one only checks the predicted position, which takes a few milliseconds. Needs the live camera.
Align: Lets the map and the directions follow the phone’s movement. See Sky map, camera and Align. On iPhone the first tap asks for permission to use the motion sensors.
Camera: Switches the live camera on or off. Off, you see the sky map.
Locate: The large orange button. Starts the camera if needed, captures a few frames and works out exactly where the camera points (plate solving). With a gallery photo loaded it solves the photo.

Sky map, camera and Align

Zenigo knows four ways of working out where you are looking. The status at the bottom left always shows which one is active.

Free sky map: Without camera and without Align you see the sky above your location as a map. Drag to look around, pinch to zoom. Handy for planning.
Compass: With Align on but before any locate, the map follows the phone using compass and motion sensor. Good for rough orientation, for example at dusk or through clouds, but often 10° or more off because the telescope’s metal disturbs the compass. A compass correction improves this.
Located: After a successful Locate the position comes from the stars themselves and is accurate to a fraction of a degree.
Motion sensor: With Align on after a locate, the gyroscope carries the exact position along while you push. It stays accurate for minutes; tap Locate again now and then, or use Continuous.

Pointing more than about 50° up, the compass is unreliable, so the app keeps its last good value and relies on the gyroscope. Near the zenith a Dobson needs large azimuth turns for small movements on the sky; the app points that out.

How locating works

Locate averages several camera frames, finds the points of light and compares their pattern with a catalogue of about 5,000 stars down to magnitude 6. That works anywhere in the sky and doesn’t need the compass or the location; the location is only used to convert the result into directions for your telescope.

The first locate also measures the camera’s field of view and saves it. It takes up to about ten seconds, later ones about a second.
It needs around ten stars in the image. Fields narrower than about 10° can’t be solved, so it does not work through the finder or the eyepiece.
Trees, houses and clouds are ignored as far as possible, but the more open sky, the better.
Gallery photos can be solved too (menu → Solve a photo from the gallery). Their field of view is searched every time.

Eyepiece point

The phone never sits exactly parallel to the tube. The eyepiece point stores the offset between camera and telescope, so the crosshair and the directions refer to the telescope.

Centre a bright star in a low-power eyepiece by hand.
Tap Locate.
Tap Eyepiece point, then the same star on the screen. The tap snaps to the nearest star and confirms it by name.

Without image detection (camera off, or top edge mode): turn on Align, centre a bright star in the eyepiece, tap Eyepiece point and then tap that star on the map. The app corrects the compass by the azimuth difference and stores the height difference between phone and telescope. The crosshair then marks where the telescope points, accurate to about a degree near that star; repeat it on another star when you move far across the sky.

Tap the button again to cancel. Camera and top edge mode each keep their own eyepiece point. Settings shows the stored offset, for example “2.8° right and 13.9° above the image centre”, and can reset it to the image centre. Set it again whenever the holder has moved.

Targets and object details

Targets are the Sun, the Moon, the planets, all 110 Messier objects, about 1,900 further deep-sky objects (NGC, IC and other catalogues, for example “NGC 869” or “North America Nebula”) and the bright named stars. Tap any object on the map for its details: brightness, distance (Moon and planets), altitude and azimuth right now, coordinates and the distance from the eyepiece. Set as target makes it your target; on the current target the button reads Remove as target. “Clear target” in Find target does the same.

The buttons at the bottom open good sources in a new tab:

Messier objects: SEDS Messier Database (data, photos, observing notes), In-The-Sky (visibility and finder charts), Wikipedia
Sun, Moon and planets: NASA Science, Wikipedia
Stars: Wikipedia and SIMBAD (the professional star database)

Telrad rings and eyepiece view

Enter your telescope and eyepieces once in Settings → Telescope and eyepieces: the focal length of the telescope, and for each eyepiece its focal length and apparent field (printed on it or in its specs, about 50° for a Plössl). The app works out the magnification and the true field, for example 25 mm in a 1200 mm telescope: 48× and 1.1°. Choose the eyepiece you are using in Quick settings.

Rings on the map: Around the crosshair the map can show the Telrad rings (red, 0.5°, 2° and 4°, as in many star charts), the true field of the eyepiece (white) and of the finder (dashed). So you see before looking whether the target will be in the field.
Eyepiece view: A round view at the bottom left shows what you should see in the eyepiece: stars to magnitude 9, Messier and other deep-sky objects at their true size, the Moon and planets, and your target, or a red arrow at the edge pointing towards it. Tap it (or its label) to switch between eyepiece and finder; ✕ hides it. Switch it on in Quick settings or Settings.
Orientation: A Newtonian such as a Dobson and a straight-through finder show the sky upside down, a star diagonal on a refractor shows it mirrored, a right-angle correct-image finder shows it upright. Choose this in Settings. How far a Newtonian turns the view also depends on where the focuser sits and how you look in: compare the view with the eyepiece once and turn it with Turn the view by until the star patterns match.

With the eyepiece entered, “should be in the eyepiece” at the top appears when the target is well inside its true field.

Filter

The Filter button chooses what the map shows. Presets:

Everything: All stars, names, constellation lines, planets, Messier and other deep-sky objects.
Solar system: Only Sun, Moon and planets.
Deep sky: All deep-sky objects, stars down to magnitude 5 for orientation, no planets.
Naked eye: Stars down to magnitude 5, constellations and planets.

Below the presets you can switch individual classes: Sun/Moon/planets, stars with a slider for the faintest magnitude, star names, constellation lines, the deep-sky classes galaxies, globular clusters, open clusters, nebulae and planetary nebulae, Beyond Messier for the NGC, IC and other objects, and satellites (only online). Each class has its usual chart symbol: ellipse for galaxies, circle with a cross for globular clusters, dashed circle for open clusters, square for nebulae, circle with a dot for planetary nebulae.

The further you zoom in, the more you see: the wide map shows stars to magnitude 6.5; zoomed in, fainter stars down to magnitude 9 appear, and more of the fainter NGC and IC objects. Messier objects are always shown. Large objects such as the Andromeda Galaxy are drawn at their true size once that is bigger than the symbol.

Your target is always shown, and Find target always searches everything. While a filter is active it is shown at the bottom left; ✕ shows everything again.

Observing list and logbook

The list is what you want to see. Add objects with the star in their details or next to them in Find target; with an empty list, Add tonight’s best objects fills it with the planets and bright deep-sky objects that are well placed tonight. Open it with the List button (the number shows how many are still to do).

The list is sorted by when objects get low, so the ones that set first come first. Each row shows the type, brightness and when it is best placed, the altitude now, and a bar for the night: the amber part is when it stands above 20° in darkness, the red mark is now. Objects that are low or below the horizon now are dimmed at the end, with the time from when they are well placed.
Newly added objects are marked “New”, and the list scrolls to the newest one. With Add in the list, Find target opens; tap the star next to objects, close it, and you are back in the list.
Tap a row to make it your target. Next (at the bottom of the list and next to the target at the top of the map) jumps to the next object that is well placed.
On the map, objects on your list have a small amber star, objects you have seen a green tick.

The logbook records what you have seen. In an object’s details tap Seen: date and time, eyepiece and magnification, altitude, Moon and site are filled in. Choose easy, hard or not found, optionally seeing and transparency (1–5, kept for the rest of the night) and a note, then Save or Save, next to go straight to the next object on your list. Objects seen tonight move to “Seen tonight” in the list. Marked one by mistake? Its ✕ there removes it from seen tonight: tonight’s logbook entry for it is deleted, and it goes back to “To do”.

The logbook (Menu → Logbook) shows your progress (Messier objects, planets, nights), suggests Messier objects you haven’t seen that are well placed tonight, and lists the entries by night; tap one to change or delete it. Object details show how often and when you last saw an object.

List and logbook are stored only on your device. Clearing the website data in the browser deletes them, so export a backup now and then: Export CSV for a spreadsheet, Export backup (JSON) to restore it with Import a backup, also on another device.

ISS and satellites

With an internet connection the map shows the ISS, the Chinese space station Tiangong and about 150 other bright satellites. Bright cyan dots are lit by the Sun and can be seen, with a short tail showing where they came from; grey rings are in Earth’s shadow and invisible. The ISS is always labelled, other satellites when you zoom in. Tap one for its height, distance and a link to Heavens-Above, or make it your target: the directions at the top then follow it.

Orbits change quickly, so the app loads them fresh from the internet (from CelesTrak, through our server) and doesn’t keep them: offline, satellites are not shown. Switch them off in the Filter. With the time set to later, the map shows where they will be, for example to catch the next ISS pass. Satellites move up to about a degree per second, too fast to follow by pushing a Dobson; it is easier to wait at a point of their path.

Time: the sky later

To plan, look at the sky at another time: Menu → Time. Drag the slider (12 hours back to 24 hours ahead), use the buttons Now, ±1 h, Dark tonight, Midnight and End of darkness, or pick any date and time. The map, the directions at the top, the target search (“well placed”) and the object details then show the sky at that time, and the time keeps running from there.

While another time is shown, it appears at the bottom left; tap it to change it, ✕ returns to now. With Align on, the map shows what will be in the direction of the phone at that time. Locate, the eyepiece point and aligning on a star need the sky as it is now, so they switch back to the current time.

Compass correction

The phone’s compass is often several degrees off, especially near the metal of a telescope. After a locate with Align on, Zenigo compares the compass with the exact direction from the stars. If they differ by more than about 1.5°, it asks: “The compass is −12.3° off. Correct it?”

Correct saves the measured value and uses it in compass mode from now on.
✕ dismisses the question. It only comes back if the measured error changes by more than 3°.
While a correction is active, “Compass corrected −12.3°” is shown at the bottom left. Its ✕ removes the correction, and the compass is used as it is again. Settings → Compass offers the same.

The correction only matters before the first locate. After a locate the position comes from the stars.

Aligning on a star by hand: in compass mode, aim the telescope (or the top of the phone) at a bright star or planet, tap it on the map and choose I’m pointing at it. The app sets the compass correction so that the direction matches. This works without camera and is the best way to make top edge mode accurate. If the altitude differs a lot as well, the location is probably wrong.

Without camera: top edge

If you don’t want to use the camera, for example with the phone strapped flat along the tube or held in the hand like a pointer, choose Settings → Pointing → Top edge. The top edge of the phone then counts as the pointing direction, and the map shows what lies in that direction.

The map always stays upright, like in a planetarium program: up on the screen is towards the zenith, down towards the horizon, however you hold the phone, whether you point up or down, with the screen facing up or towards you, or with the phone strapped to the side of the tube. Moving the telescope right moves the sky to the left, as in the eyepiece of a finder. Pointing straight at the zenith, “up” is undefined; the map then keeps its last orientation.

Align switches on automatically; the position comes from compass and motion sensor only.
The camera can be used in this mode too, if a periscope mirror or prism turns its view over the top of the phone. When you start the camera, the app asks whether the image is mirrored: choose Mirrored image on for a single mirror or a simple 90° prism, Without mirroring for optics that keep the image the right way round (two mirrors, a roof prism). The answer is remembered for the camera and can be changed any time with Mirrored image in Quick settings. Locate, Continuous and the eyepiece point then work as usual; the first Locate with Align on teaches the app where the camera looks. The image is flipped so that the screen side of the phone is up: with the phone on top of the tube, the sky is upright in the image as well. While the camera image is shown, the view turns with the phone (it has to match the image); without it, the map is upright again.
The compass is often several degrees off, and the phone is rarely exactly parallel to the tube. Centre a bright star in the eyepiece and set the eyepiece point on it: that corrects both at once, and the crosshair then marks where the telescope points.
Expect an accuracy of one to a few degrees: enough with a finder or a low-power eyepiece, not for small objects at high magnification.

Settings

Pointing: Whether the back camera looks along the telescope (default, needed for Locate) or the top edge of the phone points along it.
Location: Latitude and longitude of your observing site; GPS fills them in. Needed for every direction the app shows.
Camera: Which camera Locate uses. “Back camera (automatic)” is the phone’s main camera. The list also shows other cameras of the phone and any connected USB webcam or HDMI capture device; the names appear after the camera has been started once. Field of view and eyepiece point are remembered separately for each camera. With an external camera, Align is off, because the phone’s motion sensors don’t know how that camera moves; use Locate or Continuous instead.
Mirrored image: Switch this on when the camera looks through a mirror or prism, for example a 90° mirror so the phone can lie flat on the tube. A mirror turns the image into its mirror image, and a mirrored star pattern can’t be matched with the catalogue. With the option on, the app flips the image back before locating and showing it (left to right in camera mode, top to bottom in top edge mode). It works with both pointing modes: in camera mode for a mirror that sends the view anywhere, in top edge mode for a periscope over the top of the phone, where the app asks about it when you first start the camera. It is remembered per camera. Align keeps working: with Align on, the first Locate also teaches the app in which direction the mirror sends the view (it recognises any 90° arrangement, e.g. a periscope mirror looking out over the top of the phone). From then on the map follows the phone as usual.
Camera field of view: The angle the camera covers along the long side of the image, measured on the first successful locate (typically 60–75° for main cameras). Measure again if you switch camera or zoom. The search range limits where the measurement looks.
Compass: Shows and removes the compass correction.
Capture: Frames to stack: how many video frames are averaged per locate; more frames show fainter stars but take longer and blur if the telescope moves. Sensitivity: how faint a point of light may be to count as a star; higher finds more stars but also more noise. If your phone supports it, controls for exposure, ISO, focus and zoom appear here as well.
Display: Fill the screen with the image (or show it whole), mark the detected points of light, red light.
Telescope and eyepieces: Telescope focal length, your eyepieces (focal length and apparent field), the finder’s field of view, the rings on the map and the eyepiece view with its orientation. See Telrad rings and eyepiece view.
Eyepiece point: Shows the stored offset and resets it to the image centre.

The most important of these are also in Quick settings (the button at the top of the button column). Red light tints the whole app red to keep your eyes dark-adapted; labels next to the buttons can be switched off once you know them. In the menu, Show sky map switches from camera or photo back to the map.

Tonight

The Tonight section of the menu starts with Darkness, Moon and what’s up, calculated on the phone for your location, also offline:

Darkness: sunset, start and end of astronomical darkness (Sun 18° below the horizon), sunrise, and a timeline showing when the Moon is up. Below it: how long it is dark and moonless tonight. In summer, when it never gets fully dark, the darkest phase is shown instead.
Moon: phase, how much is lit, rise and set.
Planets that are well placed tonight, with their highest point after dusk.
Best deep-sky objects: the brightest Messier objects that climb above 30° in darkness, with the best time. Tap any of them for details or to make it your target.

For what the app can’t calculate, one good website per topic, opened for your location:

Seeing and clouds: meteoblue: Forecast of cloud layers, seeing (how steady the air is) and transparency for the next days.
Light pollution: lightpollutionmap.info: How dark the sky is at your site and where darker places are nearby.
ISS and satellites: Heavens-Above: When the ISS passes over, how bright and in which direction. Bright satellites can be confused with stars in the camera image.

Observing the Sun

Never look at the Sun through a telescope or finder without a certified solar filter covering the front of the telescope. Focused sunlight blinds instantly and permanently, a single glance is enough.

Choosing the Sun as a target first asks you to confirm that a certified full-aperture filter (ISO 12312-2 or solar film) sits on the front of the telescope, that the finder is covered or removed and that children are supervised. Locate doesn’t work in daylight, so guidance to the Sun relies on compass and motion sensor. To aim without looking, turn the tube until its shadow is as small and round as possible.

Offline and updates

Once added to the home screen and opened online, Zenigo works completely offline: star catalogue, calculations and solving all run on the phone. When a new version is available, a message “A new version of Zenigo is available” appears with an Update button. You can ignore it; the current version keeps working until you update. If no message appears, close the app completely and open it again.

Camera and sensor access

Zenigo asks for the camera (for Locate) and, on iPhone, for motion and orientation access (for Align). If you declined once, the browser remembers it and won’t ask again; a web page can’t open the settings for you either. When this happens, the app shows the steps for your device and a button to reload. Here they are in full:

iPhone and iPad

Camera, in Safari: tap aA (or the page icon) on the left of the address bar → Website Settings → set Camera to Ask or Allow. Then reload the page.
Camera, app on the home screen: open the Settings app → Apps → Safari → Camera → Ask or Allow. If that doesn’t help, remove Zenigo from the home screen and add it again from Safari.
Motion and compass: iPhone remembers a refusal only until the tab or Safari is closed. Close the Zenigo tab (or quit Safari, or close the app completely) and open it again, then tap Align and choose Allow. If your iOS version shows it, also check Settings → Apps → Safari → Motion & Orientation Access.

Android

In Chrome: tap the icon on the left of the address bar → Permissions → allow Camera and Motion sensors, or tap Reset permissions. Then reload.
App on the home screen: long-press the Zenigo icon → App info → Permissions, or in Chrome → ⋮ → Settings → Site settings → Camera / Motion sensors.
Blocked motion sensors don’t produce an error, they just send nothing. If Align shows nothing after a moment, the app assumes they are blocked and shows these steps.

Computer

Click the icon on the left of the address bar (Chrome, Edge) or open the site settings (Safari → Settings → Websites → Camera) and allow the camera for Zenigo. Then reload.

Troubleshooting

“Only a few stars detected”: It isn’t dark enough, the area is too empty or the camera exposes too briefly. Aim at a part of the sky with brighter stars, raise Frames to stack and Sensitivity, and if your phone offers it, a longer exposure or higher ISO in Settings → Capture. Make sure the camera is focused and the lens is clean and not fogged up.
“Field of view not found” or “No match”: If the camera looks through a mirror or prism, switch on Mirrored image. Otherwise get more open sky into the image. If you changed camera or zoom, tap Measure again in Settings. A wrong search range can also prevent the first measurement.
The directions are off although the map looks right: Check the location in Settings, and set the eyepiece point again. It is wrong as soon as the holder has moved.
Compass mode is far off: Normal near a metal tube. Accept the compass correction after a locate, or move the phone away from metal. Locating makes it exact anyway.
The view flips or rotates when pointing high: Turn on the phone’s rotation lock (iPhone: Control Centre; Android: quick settings). Lying flat, the phone can’t tell portrait from landscape.
The map jumps or shakes: Strong magnetic disturbances or fast jerks. After a locate the gyroscope takes over and the view becomes calm.
Camera not available: The camera access was declined. See Camera and sensor access for the steps on your device. If the camera is used by another app, close that app first.
“This device provides no orientation data”: The motion sensors are blocked or missing. See Camera and sensor access.
The app shows an old version: Tap Update when the message appears, or close the app completely and open it again.

Questions

Does it cost anything?: No. Zenigo is free, without account and without ads.
Which devices work?: Current iPhones and Android phones with Safari or Chrome, and tablets and computers with Chrome, Edge or Safari. For Locate, the camera has to show a few stars in a short exposure, which most phones from the last few years manage. Without a usable camera, the top edge mode and the sky map still work; on a computer you can use a USB webcam.
How accurate is it?: After a locate the camera’s direction is known to a fraction of a degree. In practice the limit is how well the eyepiece point is set and whether the holder stays put. A low-power eyepiece with a field of about one degree is a good start.
Can I use a webcam or another camera instead of the phone?: Yes, if the browser sees it as a camera: a USB webcam on a laptop or on an Android phone that supports USB cameras, or a DSLR or mirrorless camera through an HDMI capture stick. Mount it on the tube with its own lens and choose it in Settings → Camera. It needs a field of view of at least about 10°, so it can’t look through the telescope itself. A DSLR photo copied to the phone can also be solved with “Solve a photo from the gallery”.
Does it work with other telescopes?: Yes, with any manually moved telescope where the phone can be mounted on the tube. The directions are given as azimuth and altitude, which suits Dobsonians and other alt-azimuth mounts best.
What happens to my data?: Camera images, location and sensor data stay on your phone and are never uploaded. Details in the privacy policy.
Something doesn’t work or you have an idea?: Write to zenigo@christianranz.com.