The California Extremely Large Telescope (CELT) was a proposal for an extremely large telescope design first proposed in the 1990s by a consortium of Californian Universities.
The CELT had a positive reception and continued to be developed,[2] and was renamed the Thirty Meter Telescope (TMT) around 2003–4.
The CELT was one of the earlier and more successful proposals for extremely large telescopes.
[2] This rather naturally provides a large, 20 arcminute field of view with less than 0.5 arcsecond images (100% enclosed energy).
This focus is free of coma and only suffers from astigmatism, which grows quadratically with field angle.