AstroPix allows you to make quick, general searches, browse popular topics, or create advanced, specific searches. All searches will return a grid of thumbnails of images that match the query.
Hover over the images to see a pop-up box that shows a little more information. On a mobile device, the first touch will display the pop-up box, and the second touch will go to the image page.
To quickly find a group of images on a topic, just use the text search box at the upper right side of the pages. This text will be matched against several key fields in the image database. You can not refine a basic search, but you can always start a new one and add or subtract terms.
The Browse tab on the menu bar will display a selection of common searches. Just click on one of the topics to see the current inventory on that topic. The browse topics are just shortcuts to pre-made advanced searches.
It is possible to create a very specific search that matches against specific metadata tags. The search is very flexible and can contain a combination of and/or operations. By default, a search will look for "All" terms, requiring every element of the search to match. It can be changed to "Any" which will return images that satisfy at least one of the search terms.
Add new search terms by clicking the green "+" button, and delete a search term with the red "-" button.
The search criteria are shown at the top of a results page, allowing you to further refine the terms and submit a new search.
This is a full list of the currently-supported fields that can be used in advanced searches.
Sometimes you may want to do a more specific search that combines both "All" and "Any" criteria. AstroPix allows for nested searches that can combine these for very flexible searches.
Nested searches in AstroPix work just like iTunes "Smart Playlists".
To create a nested search group, click on the blue ellipsis ("...") button. The new search group can have its own Any/All criterion that applies only to its nested elements.
It is easier to see how these work by looking at some examples. For instance, here is a search that returns images that meet all of these criteria:
Here is another search that looks for X-ray data paired with either optical or infrared data:
For a final example, this search returns NASA images that mention "Fireworks" in either the title, description, or object name.
Advanced searches allow for very precise matches, but some searches may not return expected results without understanding the way data is represented in the database.
Due to the database architecture, searching on a term using the "Does Not Contain" comparison will only return results that have an entry in that field, but that does not match the search term. It will not match items that have left that field entirely blank. In a future update the will be an additional "Is Blank" search option.
Note that not all images have been tagged will all terms. Requiring a match in a specific tag will automatically fail on an image lacking that tag. Thus being too precise with a search could inadvertently miss items of interest that have not been fully tagged.