[BAA Comets] 46P now 6th magnitude

[Nick James]

Hi all,

Denis Buczynski has been imaging this comet from 58 deg north latitude 
so it is definitely observable from the UK when the weather co-operates. 
A chart showing the comet's track through December is here:

https://www.britastro.org/node/16287

The attached is a single 180s Green filter exposure of 46P taken with 
iTelescope T14 in New Mexico. This is a Tak 106mm FSQ with a 4x2.5 
degree FoV. The image was reduced using comphot against UCAC-4 V mags. I 
get a total magnitude of 6.1 with a coma diameter of 37 arcmin. This is 
similar to the visual mags on COBS and with the result that David Swan 
reported using iTel T9 and the same analysis tool a few days ago:

https://www.britastro.org/node/16500

I think this shows that comphot can give results that are consistent 
with visual if you use the right instrument. I have imaging booked on 
T14 every few days now up until mid December and so this will be an 
interesting test of how well we can determine magnitudes of such a 
diffuse object.

Please try to observe this object through December and consider using 
comphot to analyze your images. You can download it from here:

https://www.britastro.org/node/11124

Nick.
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 11.65  10.72  10.19   9.80   9.48   9.22 # Counts
 11.65  10.75  10.19   9.80   9.50   9.24 # Median annuli
Total integrated magnitude: 6.15 (radius 1105.4 arcsec)
COMPHOT: 1.2.8 2018 11 28.251   6.15  36.85  19.89  24.30  37.02   638.8   3.50 Astrometrica 4.10.0.431 Nick James 0046P Calibrated-T14-nickdjames-0046P-20181127-230111-Green-BIN1-W-180-001.fit
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IIIYYYYMnL YYYY MM DD.DD eM mm.m:rrAAA.ATF/xxxx  dd.ddnDC &t.ttmANG ICQ XX*OBSxxf InT APERTURcamchip SFW C ## u.uu xx.x PIXELSIZE
---------- ---- -- --.--  - --.- U4 10.6Y 5----  --.--              ICQ XX JAMaaI     -------STL KA1 CMP 5  7*          --.----.- T14, New Mexico
046        2018 11 28.25  Z  6.1 U4 10.6Y 5a180  36.85              ICQ XX JAMaaI     C36.85mSTL KA1 CMP 5  7*           3.5s 3.5 T14, New Mexico Comphot version 1.2.8