[BAA Comets] Visual equivalent magnitude of C/2013 US10

[Nick James]

This morning presented my first opportunity in a while to image C/2013 
US10 from Chelmsford. Unfortunately there was still a lot of drifting 
cloud and I had to wait rather late to get some frames that were not too 
badly affected by cloud. My wide-field image with an SXVR-H18 on the 
back of a Megrez 72, f/6 is here:

http://www.nickdjames.com/2013US10/2013us10_20151220_0633_ndj.jpg

It is not a very deep image due to the rapidly increasing sky brightness 
and some drifting cloud but I get a total magnitude of 6.84 using my 
median technique.

Half an hour earlier I got an image using iTelescope T07 at Nerpio, 
Spain (SBIG STL-11000, 0.43m, f/6.8). The sky was clear but the dawn was 
coming up fast so, again, the image is not particularly deep:

http://www.nickdjames.com/2013US10/2013us10_20151220_0559_ndj.jpg

I get a magnitude of 6.76 using this system which is remarkably similar 
to the much smaller system in Chelmsford which is encouraging.

The current COBS visual estimates are around 6.2 - 6.4.

Nick.