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You can download a public sky-survey image by entering an object name or sky coordinates into an archive’s image service, choosing a survey and field size, and selecting an output format. For a quick view, JPEG or GIF is convenient; for astronomy software and analysis, choose FITS. The Digitized Sky Survey (DSS) and Pan-STARRS1 (PS1) have different access routes and data caveats, so choose the service that fits your target and intended use.
The key decisions are practical: which archive serves the survey you want, how much sky to retrieve, whether the chosen DSS band covers your target, and whether you need a display image or a file with astronomy metadata. You do not need a scripted workflow for a single image, but repeat retrievals may be easier with the tools each archive documents for automation.
Choose a survey and access route
For a one-off image, start with an interactive archive service. The European Southern Observatory’s (ESO) Online Digitized Sky Surveys service accepts an astronomical object name or J2000 right ascension and declination. Its form lets you set image dimensions, choose a survey, and select an output format. The Space Telescope Science Institute’s (STScI) Mikulski Archive for Space Telescopes (MAST) provides DSS extractions as well as the primary image-access route for Pan-STARRS1 images.
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| Need | Route to use | What it offers |
|---|---|---|
| A single DSS image | ESO Online Digitized Sky Surveys form | Object-name or J2000 coordinate input, image dimensions, survey selection, and output-format selection. |
| DSS retrievals in a script or batch | ESO remote DSS client | Coordinate and field-of-view requests; can resolve an object name through SIMBAD and retrieve FITS images. |
| A PS1 cutout or color view | MAST Image Cutout Service | Interactive browsing, color views, and JPEG or FITS cutouts. |
| A larger PS1 image | MAST Image Cutout Service | Retrieval of larger skycell images, in addition to cutouts. |
These access options are documented by ESO and MAST. Check the relevant service documentation for current interface and retrieval details before starting a large or automated job.
A useful way to decide is to begin with the product rather than the interface. If you want a single view of a target, the interactive form or cutout service is the direct route. If you need multiple DSS fields, ESO’s remote client is designed for multiple requests in one command and integration into scripts. If the target is in PS1 and the cutout is not wide enough, MAST also offers larger skycell images. The target survey, desired field, and intended use together determine the sensible route.
Download a DSS image through ESO
Use the online form for an individual field
- Identify the target. Enter an astronomical object name or its J2000 right ascension and declination. If you use coordinates, make sure they refer to the same target location you intend to retrieve.
- Set the image dimensions. Choose a field large enough to include the object and its surrounding context. The requested dimensions affect how much of the sky the resulting image covers.
- Choose the survey. Select the DSS survey band appropriate to your purpose, and keep its sky coverage in mind. The three DSS2 bands do not cover the same fraction of the sky.
- Choose the output format. Select JPEG or GIF for convenient viewing, or FITS if you need an astronomy-oriented file with metadata for use in astronomy software.
- Submit the request and save the result. Use the downloaded file in a viewer or analysis workflow suited to its format. A display image should not automatically be treated as calibrated measurement data.
The ESO service also implements the International Virtual Observatory Alliance’s Simple Image Access Protocol (SIAP). That protocol is relevant to software and archive integrations; most people looking for one image can use the interactive form instead.
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1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsFor coordinate-based retrieval, the location you enter is the anchor for the requested field, so verify the target position before submitting. For a named target, the service accepts the object name directly. Think about the dimensions before downloading: a close view may be adequate for seeing the object, while a wider view can retain surrounding context. The service offers controls for image dimensions, survey, and format, so make those choices together rather than treating the output as a generic picture.
SIAP is an access protocol rather than a separate image format. Its importance is mainly for software that connects to image archives or for integrations that need a consistent access method. It does not change the basic decisions a reader makes about target, field size, survey band, or file format. For a one-time request, the browser form is the simpler path; for a workflow that calls the archive programmatically, consult ESO’s protocol and client documentation.
Use the remote client for repeat or scripted retrievals
ESO documents a remote DSS client for requests that need to be repeated or automated. It accepts coordinates and a requested field of view, can optionally resolve an object name through SIMBAD, and retrieves a FITS image. ESO’s example requests a 10 by 10 arcminute field; that is an example, not a required size for every target.
- Review ESO’s current client instructions. The documentation identifies version 2.5x and Linux x86 support, and notes that several older platforms are no longer supported. Confirm the current download and platform instructions before installing or relying on the client.
- Choose how to specify the target. Supply coordinates, or use the documented optional object-name resolution through SIMBAD.
- Set the field of view. Request the angular dimensions needed for the image. A small field can omit useful surroundings; a larger field returns more sky than a close inspection may require.
- Request FITS and inspect the result. The documented client retrieves FITS images. ESO says DSS extraction headers include keywords that relate pixel positions to celestial coordinates, which astronomy packages can use for viewing, conversion, or analysis.
- For multiple targets, follow the client’s batch guidance. ESO says the client is suited to submitting multiple requests in one command and to integration with scripts and automated observing tools. Check its current documentation for exact command syntax and operational limits.
The browser service remains an alternative if the client is unavailable on your system or if you only need a small number of fields.
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The client is most useful when the same retrieval process must be repeated, not simply because a request includes coordinates. It lets a workflow specify target coordinates and a field of view and retrieve FITS output; the documentation also describes optional name resolution through SIMBAD. ESO’s 10-by-10-arcminute example illustrates one request size, not a universal recommendation. Set the field according to what needs to appear in the image.
Before installing the client, check ESO’s current platform and version notes. The documentation identifies version 2.5x and Linux x86 support and says several older platforms are no longer supported. Those details may change, so do not assume that an older download or platform reference still applies. If you cannot use the client on your system, the interactive browser form is a documented alternative for a small number of fields.
Download a Pan-STARRS1 image through MAST
MAST identifies its Image Cutout Service as the primary route for accessing PS1 images. The service supports interactive browsing, color views, JPEG and FITS cutouts, and retrieval of larger skycell images. MAST also provides a notebook example for scripted downloads.
- Open the MAST Image Cutout Service. Use the interactive service for a single target or the documented notebook approach when you need a scripted workflow.
- Find the target and choose the image area. Select the cutout or larger skycell image that suits the amount of sky you need. A cutout is suited to inspecting a particular region; a larger skycell is an option when that small view is insufficient.
- Select the view and format. PS1 images use five broadband filters—g, r, i, z, and y. MAST provides color views and JPEG or FITS cutouts; select the available view and output that match your task.
- Save and identify the downloaded product. Keep track of the selected filters, image type, and whether the file is a cutout or a larger skycell. Those details matter when you later interpret or compare images.
- Consult MAST’s documentation before analyzing pixel values. In particular, do not assume PS1 stack-image pixel values are linearly proportional to flux.
PS1’s five broadband filters provide different image selections; they are not a single generic band. When retrieving or comparing products, note which filter or filters were selected and whether the result is a color view, an individual cutout, or a larger skycell image. MAST supports interactive browsing as well as a notebook example, so a one-off inspection and a scripted retrieval have documented routes without requiring the same workflow.
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Scan for outdated or missing drivers - takes under a minuteDriver Scan →Repair Windows errors before they cause bigger problemsFix Now →A larger skycell is not automatically the better choice: use it when the cutout does not contain enough of the sky for your purpose. Conversely, when the question is about one small region, the cutout route is more directly suited to that view. Keep the product type and filter information with the downloaded file, especially if you will revisit it later or compare it with another image.
Choose JPEG, GIF, or FITS
Choose the file type according to what you intend to do with the image, not just how it looks in a browser. JPEG and GIF are convenient for visual inspection. FITS is the astronomy-oriented option when you need image data and astronomy metadata for a software workflow.
| Format | Best suited to | What to keep in mind |
|---|---|---|
| JPEG | Quick viewing or sharing a visual image. | A viewable image is not, by itself, evidence that pixel values are calibrated for quantitative work. |
| GIF | Quick viewing where the service offers it. | Like JPEG, it is a convenient display format rather than the astronomy-oriented choice described for analysis workflows. |
| FITS | Viewing, conversion, or analysis with astronomy packages. | ESO says its DSS extractions include header keywords that relate pixel positions to celestial coordinates. FITS format alone does not establish that every image is a calibrated, linear science product. |
ESO’s STScI-hosted DSS service offers FITS, JPG, and GIF extractions. ESO’s own DSS documentation describes the metadata in its FITS extractions. For PS1, MAST offers JPEG and FITS cutouts and warns that stack-image values have a non-linear relationship to flux.
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In practical terms, choose JPEG or GIF when you primarily need an image to look at or share. Choose FITS when your next step involves astronomy software, retaining coordinate information, or further inspection of image data. The FITS header is part of the value of the file: for ESO DSS extractions, its keywords relate pixel positions to celestial coordinates. Converting a FITS image to a display format may be useful for viewing, but do not rely on the rendered copy as a substitute for the original data and metadata when coordinates or analysis matter.
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Format is not a guarantee of scientific calibration. A file can be FITS and still require product-specific interpretation. MAST specifically warns that PS1 stack-image pixel values relate non-linearly to flux. Check the documentation for the particular product before treating pixel values as measurements; do not assume a JPEG, GIF, displayed color image, or FITS filename alone says how values map to flux.
Check DSS2 band coverage before choosing
ESO’s Online Digitized Sky Surveys page reports the following DSS2 coverage figures. The page provides no publication year, so these figures are attributed to the service as accessed in 2026.
| DSS2 band | Sky coverage reported by ESO |
|---|---|
| Blue | 45% |
| Red | 98% |
| Infrared | 99% |
Coverage is a practical constraint: a band that is suitable for one target may not have a corresponding image for another location. The figures differ substantially, so do not assume that the blue, red, and infrared surveys cover the same sky area. If the selected band does not return the field you need, check the available DSS2 coverage in another band.
The reported numbers are DSS2-specific and should not be generalized to PS1 or to every image in every archive. In particular, the blue figure is markedly lower than the red and infrared figures. If band choice is flexible, checking availability before building a workflow around one DSS2 band can prevent a missing-field surprise. The figures are the coverage reported on ESO’s service page and were accessed in 2026; consult that page for current service information.
Understand what the downloaded image can tell you
Display image versus image data
A downloadable file is not automatically a calibrated science product. JPEG or GIF is appropriate when the purpose is to inspect or share an image visually. FITS is more suitable when you need image data and astronomy metadata, but the format alone does not guarantee that pixel values have a particular calibration or a simple relationship to flux.
This distinction helps prevent a common category error: a survey image service makes images accessible, but the fact that an image can be downloaded does not by itself establish that its pixel values support a chosen measurement. Visual inspection and quantitative analysis are different tasks. For visual inspection, a display format may be enough. For analysis, retain the astronomy-oriented file and consult the archive documentation for that product’s properties.
PS1 stack values need special care
MAST warns that pixel values in PS1 stack images are related non-linearly to flux. That warning matters if you plan to use pixel values as measurements or compare them quantitatively. Before doing so, consult MAST’s documentation for the relevant image product and its limitations; do not infer a linear flux scale from a displayed image or from the FITS extension alone.
In particular, do not treat a color rendering as a direct numeric representation of brightness or assume that a stack’s stored values can be compared as though they were linearly proportional to flux. If your goal is simply to locate or view an object, this caveat need not prevent you from using the service. It becomes important when the intended task depends on interpreting pixel values quantitatively.
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Use FITS metadata in the right workflow
ESO says its DSS FITS extractions carry header keywords needed to relate pixel positions to celestial coordinates. Astronomy packages can use that information to display, convert, or analyze the image. If your task depends on coordinate alignment, preserve the FITS file and its header rather than relying only on a rendered JPEG or GIF.
The metadata is particularly relevant when you need to connect locations in the downloaded image to positions on the sky. A JPEG or GIF may preserve the visual appearance that is useful for sharing, but ESO describes the coordinate-related header information in its DSS FITS extractions. Keep the original FITS product if that relationship matters to your work.
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The field size, survey, and output format determine whether a download serves its intended purpose. Before submitting a request, decide whether you need just the target or its surroundings, whether the target is covered in the chosen DSS band, and whether you need a viewable image or an astronomy-data file.
- For a quick look at one object: use an interactive DSS or PS1 service, select a field that includes enough context, and choose a convenient display format.
- For coordinate-aware work: request FITS where available and retain its metadata for astronomy software.
- For repeated DSS fields: consider the documented ESO remote client rather than manually submitting each form request.
- For PS1 access beyond a small region: check whether a larger skycell image is more appropriate than a cutout.
- For quantitative use: verify the documentation for the specific data product, especially for PS1 stack pixel values.
These services’ interfaces, output options, coverage descriptions, and platform support can change. Use the official ESO or MAST documentation for the current details of a particular request.
A short decision checklist can make the request more reliable:
- Choose the archive and survey. Use ESO’s Online Digitized Sky Surveys for DSS access or MAST’s Image Cutout Service as the primary route for PS1.
- Locate the target. Use an object name or, for ESO’s DSS form and remote client, J2000 coordinates. The client can optionally resolve an object name through SIMBAD.
- Set the area. Select image dimensions or a field of view large enough for the target and context. For PS1, decide whether a cutout is enough or a larger skycell is needed.
- Choose an output you can use. Pick JPEG or GIF for simple viewing where offered, and FITS for astronomy-oriented viewing or analysis workflows.
- Check the product caveats. Verify DSS2 band coverage and consult MAST’s documentation before using PS1 stack pixel values quantitatively.
Do not assume that all route details are permanent. The ESO batch-tool documentation identifies version 2.5x and Linux x86 support and notes that several older platforms are no longer supported; the archive interfaces, formats, and coverage descriptions can also change. Check the current official service instructions before an installation or an automated job.
Frequently Asked Questions
How do I download a sky image for specific coordinates?
Use an official image service that accepts coordinates. ESO’s Online Digitized Sky Surveys form accepts J2000 right ascension and declination; set the image dimensions, choose a DSS band and output format, then submit the request. For repeat DSS retrievals, ESO’s remote client accepts coordinates and a requested field of view.
Where can I get a FITS image of an object?
ESO’s DSS service offers FITS extractions, and its documented remote DSS client retrieves FITS images. MAST’s Image Cutout Service also provides PS1 FITS cutouts. FITS is suited to astronomy workflows, but the format alone does not guarantee a particular calibration or a linear relationship between pixel values and flux.
How do I download a Pan-STARRS image cutout?
Use MAST’s Image Cutout Service, which MAST identifies as its primary access route for PS1 images. It supports interactive browsing, color views, and JPEG or FITS cutouts; MAST also provides a notebook example for scripted downloads. PS1 images use the g, r, i, z, and y broadband filters.
Should I choose a DSS2 blue, red, or infrared image?
Choose based on the band you need and whether the target field is covered. ESO reports DSS2 coverage of 45% for blue, 98% for red, and 99% for infrared, so the bands do not cover identical sky areas. If your chosen band does not provide the field, check another available DSS2 band.
Can I use PS1 stack-image pixel values as direct flux measurements?
Do not assume they are linearly proportional to flux. MAST warns that PS1 stack-image pixel values have a non-linear relationship to flux. Consult MAST’s documentation for the specific product before using pixel values quantitatively.
Do I need the ESO remote client to download DSS images?
No. The ESO browser form is suitable for a small number of fields. The remote client is intended for repeated or batch retrievals and can be integrated into scripts. Check ESO’s current client instructions, including platform and version details, before installing it.
The Bottom Line
For a single image, use ESO’s DSS form or MAST’s PS1 Image Cutout Service, enter the target, choose a suitable field and band, and select a format for your task. Use FITS when astronomy metadata and software workflows matter; use JPEG or GIF for quick visual inspection. Check DSS2 coverage and MAST’s warning that PS1 stack values are non-linear with flux before quantitative use.
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