"Astroplate" is not a commonly used term in astronomy or related fields. It is possible that it is a mispronunciation or misspelling of a related term.

Here are some possibilities:

* Astrograph: A specialized telescope designed specifically for astrophotography (taking pictures of celestial objects).

* Photographic plate: A glass plate coated with a light-sensitive emulsion, previously used in astronomy to capture images of stars, nebulae, galaxies, etc. These are now mostly replaced by digital sensors.

* Astrometry plate: A photographic plate specifically used for astrometry, the branch of astronomy that deals with measuring the positions and motions of celestial objects.

Could you please clarify what you meant by "astroplate"? If you provide more context or a specific situation where you encountered this term, I might be able to give you a more precise answer.