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Yes—but the best free app depends on what you mean by “identify.” If you are standing at a manually aimed telescope and want guidance to a named galaxy, use AstroHelm with a securely mounted phone. If you already have a sky photograph, Sideris can plate-solve it and return coordinates. For names drawn over a finished astrophotograph, Akastroid is the most direct option. Aladin with astrometry.net is the deeper desktop workflow for FITS files and crowded fields, while Stellarium supplies free, open-source sky context rather than automatic image annotation.
The important distinction is between pointing a telescope, solving where an existing image points, and annotating the objects visible in that image. The guide below matches each job to a tool and explains the equipment, file types, settings and limitations involved.
Three different jobs called “galaxy identification”
A phone app cannot solve every astronomy task in the same way. Decide which result you need before installing anything.
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Guiding a manual telescope to a galaxy
This is a live observing problem. You point the telescope roughly, let the phone photograph the field, and the software compares the star pattern with a sky catalogue. The app then tells you how to move the telescope until the requested galaxy is centred. AstroHelm is designed for this phone-first use and can work without cellular service or Wi-Fi after setup.
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Finding the coordinates of an existing image
A plate solver determines the image’s right ascension, declination, scale and orientation from the stars recorded in the frame. Sideris is a lightweight mobile choice for a saved sky photograph; it can return celestial coordinates and place the solved frame on an interactive sky map.
Putting object names on an astrophotograph
Annotation starts with a solved image and cross-matches the field against object catalogues. The result is a preview or exported image with labels and markers for galaxies, nebulae, clusters and stars. Akastroid focuses on this finished-image workflow. Aladin combined with astrometry.net provides a more technical desktop route, especially for FITS data.
Best free options at a glance
| Tool | Platform | Input | Coordinates | Labels on image | Offline or integration notes | Extra hardware |
|---|---|---|---|---|---|---|
| AstroHelm | iOS and Android | Live phone-camera view through a telescope | Yes, as part of continuous plate solving | Guides framing rather than primarily annotating a finished file | On-device solving; no cellular service or Wi-Fi required; supports ASCOM Alpaca, INDI and LX200 communication | Rigid phone mount or telescope adapter |
| Sideris | Android listing; verify current availability for your device | Saved night-sky photo | Yes | Places the solved image on a sky map; not primarily an export annotator | Free plate solves are offered; current quota and terms can change | None beyond the camera that created the image |
| Stellarium | Linux, Windows and macOS | Interactive sky model and observing plan | Shows catalogue coordinates and sky position | No automatic labels on your own photograph | Free, open-source planetarium; the current site lists version 26.2 | None |
| Akastroid | Web-based tool | Astrophotograph preview | Uses a plate-solved field | Yes; marks galaxies, nebulae, clusters and bright stars, using recorded size, orientation and shape for galaxy markers | Free to try; exact limits may change | None |
| Aladin plus astrometry.net | Desktop | Usually a FITS image, with WCS metadata | Yes | Yes, through catalogue overlays and investigation | Free, powerful research workflow with a steeper learning curve | Computer and a suitable FITS file |
| Galaxy Zoo | Web project and educational resources | Galaxy images supplied by the project | Not a general-purpose solver for your image | Not a personal-photo annotation tool | Citizen-science classification project rather than telescope control or plate solving | None |
AstroHelm: best for a phone-guided manual telescope
AstroHelm continuously plate-solves the sky to guide you toward galaxies, nebulae, planets and stars or to help frame a target for photography. Its defining advantage is that the solving runs on the device, so a phone can be used in the field without mobile data or a Wi-Fi connection.
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- An iPhone or Android phone with a working camera.
- A manual telescope with a field visible to the phone camera.
- A rigid smartphone telescope adapter that holds the phone squarely over the eyepiece or optical path.
- A target name or coordinates, plus enough darkness and focus for the camera to record several stars.
A loose clamp is the most common avoidable problem. If the phone shifts between solving attempts, the apparent field changes and the guidance becomes unreliable. Choose an adapter whose clamp fits your phone width and whose eyepiece collar matches the telescope; check both dimensions before buying.
Live pointing procedure
- Install AstroHelm on iOS or Android and allow camera access.
- Attach the phone to the telescope with the adapter. Tighten every joint, then gently tap the tube to check that the framing does not move.
- Focus the telescope and phone camera on stars. A blurred field or a single bright star gives the solver too little pattern information.
- Start the app’s plate-solving view and wait for a recognised field. Keep the telescope still during the initial solve.
- Select the galaxy you want. Follow the directional guidance, making small adjustments rather than swinging the tube rapidly.
- Let the app solve again after each move. Stop when the target is centred or framed for your camera.
Connecting a computerised mount
AstroHelm can communicate with astronomy software through ASCOM Alpaca, INDI and LX200 protocols. That makes it useful beyond a purely manual setup, but the exact connection steps depend on the mount, operating system and control software. Confirm that your mount exposes one of those protocols before planning an automated workflow; the app’s documented phone-guidance use does not require a motorised mount.
Rank #2
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- Precise 3-Axis Alignment for Cleaner Shots (Patent Pending) — This 3-axis digiscoping adapter lets you adjust your phone left/right, up/down and forward/back to line up the camera with the eyepiece. The Z-axis adjustment helps reach the right eye relief, reducing dark edges or vignetting for clearer photos and videos.
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- Shoot Without Touching the Scope — Use the included Bluetooth remote with this phone scope adapter to take photos or videos without tapping your phone and shaking the image, making it easier to capture sharper shots and share your view.
- Fits Most Phones & Many Standard Eyepieces — This smart phone adapter for telescope fits most iPhone and Android smartphones from 2.36"–3.44" wide / 60–87.5 mm. It also fits eyepieces with an outer diameter of 0.86"–2.4" / 22–61 mm.
Sideris: a lightweight solver for a saved phone or camera image
Sideris is intended for the situation in which the photograph already exists. Its Google Play description calls it a plate-solving companion and interactive star map: submit a night-sky image, receive its true celestial coordinates and inspect the solved frame in a map context.
When it is the right choice
- You photographed a galaxy field and forgot the exact pointing.
- You want to confirm whether a frame contains the object you expected.
- You need a visual map match rather than a desktop FITS-processing pipeline.
Use the original, uncropped image when possible. Cropping away too many stars, applying aggressive noise reduction or saving a very small screenshot can leave the solver without enough pattern information. If the app rejects a frame, try a larger version with stars that are in focus and not saturated.
Recommended Free Tools
Free-use qualification
The listing says users can try free plate solves, but mobile store quotas, subscriptions and platform availability can change. Check the current listing on the day you install it, particularly if you expect to solve many images in one session.
Stellarium: the free sky atlas that explains the result
Stellarium is a free, open-source planetarium for Linux, Windows and macOS. It renders a realistic sky as seen with the naked eye, binoculars or a telescope; the current official page identifies version 26.2.
What Stellarium does well
- Shows where a galaxy should be at a selected date, time and location.
- Lets you search catalogue names and inspect neighbouring stars and deep-sky objects.
- Helps plan an observing session before taking the telescope outside.
- Provides the sky context needed to interpret coordinates returned by a plate solver.
Stellarium is not, by itself, a dedicated automatic annotator for a JPEG, PNG or FITS astrophotograph. The practical combination is to solve the image with Sideris, astrometry.net or another solver, then use Stellarium to understand the field and plan a follow-up observation.
Rank #3
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Akastroid: the straightforward route to labels on an astrophotograph
Akastroid’s annotation tool plate-solves an image and places labels for galaxies, nebulae, clusters and bright stars on its preview. Galaxy markers can use the object’s recorded size, orientation and shape, so the overlay can indicate the extent and direction of a galaxy rather than displaying only a point.
Recommended workflow
- Prepare a clean, full-resolution astrophotograph. Keep the original file separate from any annotated copy.
- Upload or open the image in Akastroid’s annotation tool.
- Allow the field to be plate-solved. If the solve fails, return to the original, less-processed image and try again.
- Review the proposed labels. Bright stars and well-known objects are easier to verify than extremely faint galaxies.
- Adjust the annotation preview so labels do not obscure the object you want to show, then export or save the result according to the tool’s current options.
Akastroid is best understood as a post-capture presentation tool. It does not replace a planetarium for planning or a mount-control system for pointing.
Aladin plus astrometry.net: the deeper desktop workflow
For FITS images, crowded galaxy fields or research-style inspection, a free Aladin and astrometry.net workflow offers more control. A typical process plate-solves the image, writes world-coordinate-system (WCS) information into the FITS file and then overlays catalogues in Aladin.
How the pieces fit together
- Submit the image to astrometry.net or run a compatible local solver. The solver recognises the star pattern and calculates the field centre, scale and orientation.
- Save the resulting WCS-enabled FITS file. WCS is the metadata that tells software which celestial coordinate corresponds to each pixel.
- Open the file in Aladin and load catalogue overlays. You can inspect many faint galaxies and other objects that are present but not obvious in the raw image.
- Compare catalogue positions with the image, then export a view or retain the FITS file for later analysis.
Plate solving only establishes where the image points. The names and classifications come from the catalogue cross-match performed afterward. This distinction matters when several faint galaxies fall close together: a coordinate solution can be correct even when a catalogue overlay still needs careful checking.
Galaxy Zoo: useful astronomy, but not a personal-photo identifier
Galaxy Zoo is a citizen-science classification project, not a one-click plate solver for your telescope photographs. NASA describes its 2007 beginning with one million galaxies imaged by the 2.5-metre telescope used for the Sloan Digital Sky Survey; later work included Hubble and Euclid imagery. Participants classify structures in supplied survey images, helping researchers study galaxy shapes and features.
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- With this universal smartphone telescope adapter, you can connect your phone to a telescope or microscope to take images of the moon and cells, or to a spotting scope to take images of birds and other objects.
- Smartphone mount compliable with microscope, telescope, binoculars, monocular, night vision spotting scope. Fit eyepiece diameter 22mm～ 44mm(0.86"-1.73").
- Optimized weight, lighter and reduce the pressure on the telescope eyepiece, weight: 75 g / 2.65 oz.The body is made of high-strength PA plastic. The surface of the mobile phone and eyepiece has a soft EVA pad to avoid scratching and damage.
- Warranty service:If you have questions about installation and not using, please contact us in time, we will reply and deal with your problems as soon as possible.
Use Galaxy Zoo when you want to learn how galaxies are classified or contribute to a science project. Use a plate solver and catalogue overlay when the question is “Which galaxy is in my image?”
Choose a workflow by your file and observing setup
Manual visual telescope, phone attached
Choose AstroHelm. The phone must see the telescope’s field, and the mount must remain rigid while the app solves and guides. This is the only option in the shortlist built primarily around continuous, live guidance to a named target.
JPEG or PNG captured earlier
Try Sideris for coordinates and a sky-map match. If your goal is a shareable image covered in object names, send the same photograph to Akastroid after solving or use a desktop workflow.
Deep-sky camera producing FITS
Use astrometry.net to create WCS metadata, then inspect the field in Aladin. FITS preserves the metadata and image information needed for more precise catalogue work than a compressed screenshot.
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Use Stellarium to select targets, check their position and understand the surrounding star field. It is a planning and visualisation layer, not the automatic identifier for the final photograph.
Best Value
- Capture What You See Through Your Scope — TRIDAPTOR turns your spotting scope, telescope, monocular or microscope into a smartphone viewing and camera setup. View through your phone screen instead of staying pressed against the eyepiece, then capture and share birds, wildlife, targets, celestial objects and distant views.
- Precise 3-Axis Alignment for Cleaner Shots (Patent Pending) — This 3-axis digiscoping adapter lets you adjust your phone left/right, up/down and forward/back to line up the camera with the eyepiece. The Z-axis adjustment helps reach the right eye relief, reducing dark edges or vignetting for clearer photos and videos.
- All-Metal Build, No Phone Sagging — Rigid aluminum construction helps keep your phone steady and aligned, unlike flimsy plastic telescope phone adapters that can flex, tilt or lose position. Rubber pads help protect your phone and eyepiece from scratches.
- One Adapter for Most Phones — The telescope phone mount fits most iPhone and Android smartphones from 2.36"–3.44" wide / 60–87.5 mm. No need to buy a new adapter every time you upgrade your phone or scope.
- Check Eyepiece Size Before Ordering — This smart phone adapter fits many spotting scope eyepieces within 0.86"–2.4" / 22-61 mm outer diameter. Please measure your eyepiece before purchase. Compatible with most Vortex, Swarovski, Celestron, Nikon, Zeiss, Kowa and Leupold eyepieces.
Hardware and image preparation that affect every solve
Rigid phone mounting
For AstroHelm, the main accessory is a rigid smartphone telescope adapter. Match the adapter to the phone’s dimensions and the eyepiece diameter. A design that lets the phone twist or sag changes the field between exposures and can prevent repeat solves.
Focus and exposure
- Focus stars until they are compact points rather than large discs.
- Avoid clipping most stars to white; a solver needs the relative pattern, not just the brightest object.
- Use enough exposure to record several stars, but avoid such a long exposure that every star trails.
- Keep the lens and eyepiece clean. A fingerprint can reduce contrast across the entire field.
File choices
Keep the original camera file. A full-resolution JPEG or PNG is usually more useful to a mobile solver than a messaging-app thumbnail. For scientific cameras, retain the FITS file and its metadata; converting it to a screenshot discards information that Aladin and WCS tools can use.
What these apps can and cannot prove
None of the listed products has a common published benchmark for solve speed or identification accuracy, so it is not justified to call one objectively the most accurate. A successful plate solve establishes the pointing solution; it does not automatically prove that every faint smudge has been correctly identified.
The Tool Desk
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Troubleshooting failed or misleading results
The app cannot solve the field
- Return to the uncropped, higher-resolution image.
- Refocus so stars are distinct.
- Increase exposure slightly if only one or two stars are visible.
- Reduce exposure or gain if the frame is saturated.
- For a phone on a telescope, tighten the adapter and keep the tube still during the solve.
The coordinates look wrong
Confirm the image’s orientation and field of view, then compare the solution with a known bright star in Stellarium. If a camera was rotated or the image was flipped during processing, the orientation may differ even when the centre coordinates are correct.
Labels cover the galaxy
Use Akastroid’s preview controls to move or reduce annotations, or export a clean copy and a labelled copy separately. In Aladin, adjust catalogue overlays instead of permanently painting labels into the original FITS file.
The free allowance has run out
Free policies are service-specific and can change. Sideris explicitly offers free plate solves but does not guarantee a permanent quota in the description; Akastroid is described as free to try. Recheck the current store or service terms rather than assuming unlimited use.
A practical decision checklist
- I need directions while standing at a manual telescope: AstroHelm plus a rigid phone adapter.
- I need coordinates from an existing mobile image: Sideris.
- I need names drawn over a finished image: Akastroid.
- I have FITS files or a crowded deep-sky field: astrometry.net followed by Aladin.
- I need a free atlas and observing plan: Stellarium.
- I want to practise galaxy morphology classification: Galaxy Zoo, understanding that it does not solve personal telescope photos.
Start with the least complicated tool that produces the result you actually need. Move to the Aladin and astrometry.net workflow when you require FITS preservation, catalogue overlays or investigation of many faint objects.
Quick Recap
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