After using the software program APT, more accurate magnitude figures have been calculated. These are based on using SDSS J115551.05-021502.5 r-band and g-band. SDSS J115551.05-021502.5 is nearby and has a spectrum so is a worthwhile reference object. http://skyserver.sdss.org/dr14/en/tools/explore/Summary.aspx?id=12376503...
The results are:
r-band = magnitude 19.160649832, which is ~19 with an error of less than 5%.
g-band = magnitude 20.8305465783, which is ~21 with an error of less than 5%

## Comments

Mr. Richard Nowell

Mon, 05/21/2018 - 11:31

## Update of magnitude figures 21 May 2018

After using the software program APT, more accurate magnitude figures have been calculated. These are based on using SDSS J115551.05-021502.5 r-band and g-band. SDSS J115551.05-021502.5 is nearby and has a spectrum so is a worthwhile reference object.

http://skyserver.sdss.org/dr14/en/tools/explore/Summary.aspx?id=12376503...

The results are:

r-band = magnitude 19.160649832, which is ~19 with an error of less than 5%.

g-band = magnitude 20.8305465783, which is ~21 with an error of less than 5%