I found an interesting object when I blinked images from the DSS Plate Finder https://archive.stsci.edu/cgi-bin/dss_plate_finder with photos obtained on 2025-11-03 at the remote telescope T75 of iTelescope.Net in Chile. This year I discovered SN 2025umq (Type Ia supernova https://ui.adsabs.harvard.edu/abs/2025ATel17361....1R/ in the galaxy SDSS J004819.14+075856.8) this way, but this time the object was not in new photographs, but in archival ones.
I found a possible bright missed supernova in the ESO 157-27 galaxy on the POSS-II F plate (1994-12-28 12:45:00, exposure time 70 minutes). I measured magnitude R = 12.3 compared to the R magnitudes of nearby stars from the ATLAS catalog (Tonry, et al., 2018). My measured J2000.0 position: 04:25:32.31 -56:51:20.09.
GSC2.3 position = 04:25:32.2 -56:51:21.8; GSC2.3 magnitude R = 10.02; name GSC2.3 S12G005521. Now this is AT 1994au https://www.wis-tns.org/object/1994au (in the TNS).
For comparison: 1994-12-28 DSS Red plate and image from DESI Legacy Surveys: https://www.wis-tns.org/system/files/uploaded/F.%20D.%20Romanov/tns_1994au_a...
No nearby minor planets found via Minor Planet Checker, there are no similar supernovae in the list http://www.cbat.eps.harvard.edu/lists/Supernovae.html and in the Transient Name Server. It does not look like a defect in the plate because the rays are similar to those of other stars. There are no objects nearby in other images from other years.
I have previously found similar astronomical transients - possible missed supernovae AT 1991bm in the galaxy UGC 11180 and AT 1992bw in the galaxy UGC 43 - in the images from the DSS Plate Finder (I mentioned this in my paper: https://ui.adsabs.harvard.edu/abs/2022arXiv221212543R ), like the possible dwarf nova Romanov V1 (on two POSS plates for 1958, more details about this: https://ui.adsabs.harvard.edu/abs/2018OEJV..190....1R/ ). This is likely one of the brightest possible missed supernovae.
Filipp Romanov (AAVSO).