The image gallery software categorises all images according to the objects that are tagged within the image. Sometimes, however, it is useful to be able to categorise an image beyond simply the astronomical objects it contains.

To enable you to do this, you will find a number of objects in our object database which are not strictly astronomical objects.

Feel free to tag the following "objects" in your images:

Aurora, Noctilucent cloud, Polar mesospheric cloud, Meteor, Spacecraft, Eclipse, Transit, Conjunction, Observatory, Equipment, Meeting, Historical, Milky Way, Zodiacal light, Gegenschein.

When you upload an image, you will be asked to specify what objects are in your image twice. The "target name" field provides you with a free text-entry, where you can type whatever you like. Under "Objects in image", what you type must exactly match the name of an object which already exists in our database of objects.

When you start typing, you will see auto-completion hints to help you. So, when you start typing "Jup", you will see suggestions of Jupiter or NGC 3242 – the Ghost of Jupiter nebula.

The background colour of the "Objects in image" indicates whether you have correctly matched a known object: a green background indicates a match, while a red background indicates that your text was not accepted.

If you observe a very faint and/or obscure object, you may find it doesn't exist in our database of objects. In that case, simply add the object's name in plain text in the "Target name" field. However, be aware that if the "Objects in image" fields are not completed, your image will not show up in some search results.

The database of objects you can tag in your images includes a huge number of objects. This includes every asteroid with >500 observations in the MPC database, every comet discovered up to mid-2020, and the following deep sky catalogues: Messier, Caldwell, NGC, IC, Abell clusters, Abell PNs, Barnard, Sharpless, Arp, Hickson, Markian, Collinder, Melotte. It also contains every star to 6th magnitude.

However, it is not exhaustive, and faint deep sky objects may not be listed. Try a different designation or common name. If you still cannot find the object you are looking for, simply add the object's name in plain text in the "Target name" field when you upload your image.

There are a number of reasons why our plate-solving software may not be able to fit your image. It assumes all images were taken through a perfect lens, which is a good assumption for small fields of view, but a poor assumption for wide-field images, especially if taken through imperfect optics.

Textual annotations on the image may also confuse the plate-solving engine: it tends to interpret all the letters as bright stars.

There also needs to be a reasonable number of stars visible for the plate-solving software to find a match – solar system objects don't count!