The brightness of 161/Hartley-IRAS is particularly noteworthy. One prediction gives a bright 8-9th magnitude around July 14 using the formula m1=5.5+5 log Δ+17.0 log R. However, the comet is not detectable visually. Even in the 60cm reflector it was faint and estimated to be at 14-15th magnitude. This formula was well tested by research and observation and is supposed to be accurate, but the results sometimes betray the predictions. I worked out the formula m1=9.5+5 log Δ+15 log R, based on the standard formula, in which the coefficient of log R is 10 or 15. The results from this formula will not deviate much from the prediction. The magnitude prediction of the comet is not easy. It often turns out to be wrong even though a well tested formula is used. This comet is very diffused without a nucleus and looks like a glowing fog.

CK01Q040 2004 11 29.38299 19 28 16.01 +67 01 15.1 14.2 T 372 CK04Q010 2004 11 29.41042 23 44 03.96 +39 29 33.4 11.5 T 372 CK04Q010 2004 11 29.42326 23 44 02.80 +39 29 41.7 372 PK05J05Q 2005 06 06.53056 13 45 48.36 +06 17 00.8 372 0032P 2004 11 29.41563 02 35 47.55 +11 40 57.8 12.8 T 372 0032P 2004 11 29.41927 02 35 47.35 +11 40 57.8 372 0069P 2005 01 17.65556 09 06 27.70 +28 11 54.2 16.8 T 372 0069P 2005 02 02.55764 08 57 34.27 +33 09 24.7 16.5 T 372 0162P 2004 11 16.53715 22 56 04.72 -04 05 00.5 15.5 T 372 0162P 2004 11 29.40347 23 13 16.40 +10 55 52.5 372 0162P 2004 11 29.42917 23 13 18.57 +10 57 29.3 13.4 T 372 0161P 2005 07 14.68715 04 43 01.23 +78 35 41.4 14.5 T 372 0161P 2005 07 14.76997 04 44 48.76 +78 40 02.5 14.4 T 372