Tuesday 15th July 2014 I rediscover a Dwarf Nova - already discovered in 1998 - that was classified incorrectly as a supernova!

A much better night but still poor seing. I ran a 20 point T Point model and set up two galaxy runs between 18h and 19h RA and19h and 20h RA. Pointing is not bad but I found it necessary to synch the first galaxy in each run into the T Point model.  I have been unable to cool the chip too far because of condensation - the dessicant will be refreshed tomorrow. 

I was checking a galaxy I had imaged (PGC 63176) when I spotted a galaxy (not on my list) that seemed to have a SN possibility. This is the plate solved image that I used with the SkyX to identify the unknown galaxy.

This is the same image with annotation.

 

It turned out that this object had actually been listed as a supernova SN1998di and was later found to be a dwarf nova in outburst. Here are the details from Dave Bishop's excellent Supernova website. Courtesy of D. Bishop:

More details here

 This extract from IAU Circular 6983 explains it all.

So it is not a supernova but an object in our own Galaxy. A line of sight effect that led to an incorrect identification in 1998 - something to be wary of.

Another "might have been" discovery.

 I need to track down any observations since 1998 to check if it has remained at that brightness, My image was unfiltered - I need to reimage with B and V filters and check its magnitude at the AAVSO.