| Date UT | Observers | Weather
| First seen | Last Seen | Position |
| Telescope | Description
|
| May 11.23 |
N. Biver, H. Dahle, O. Guyon
| No haze, No cirrus, some clouds
| 5:28 UT (alt.+5 Sun -6) | 5:43 UT (alt.1.2+/-0.2 )
| - |
| 84x256 L
| Easily visible, nearly stellar (poor seeing), Tail 4-5' PA 70 |
| May 12.21 |
N. Biver, H. Dahle, O. Guyon
| Too many clouds towards the comet
| - | -
| - |
| 42x256 L
| Hidden by clouds |
| May 13.24 |
N. Biver, H. Dahle, O. Guyon
| No haze, No cirrus, Many clouds
| 5:47.5 UT (alt. +163'+-10') | 5:51.0 UT (alt.+110'+/-5')
| 5:49.6 UT: alt.+121'+-10' |
|
| 42x256 L
| Easily visible, nearly stellar, Tail 4-5' ? PA ~100
Comparison stars: Rigel, Aldebaran (at same altitude) and probably 44 per. |
| May 14.2 |
-
| Cloudy
| - | -
| - |
| May 15.22 |
N. Biver
| Thick cirrus up to an alt. of 5-8
| - | -
| - |
| 42x256 L
| Hidden by clouds, but aldebaran observed 2 min.: nothing 0.5 around |
| May 16.24 |
N. Biver, H. Dahle, O. Guyon
| No haze, some cirrus, few clouds
| 5:45 UT | 5:58 UT (alt. 1.9+/-0.2)
| 5:58 UT: R.A.=4h47.5 (+-15' or more...) (J2000.0) Dec.=+1253' (+-15') |
| | 5:49 UT: 4.8 left, 1.4 up / Aldebaran |
| | 5:58-6:09: 9 ori at Dec.+20' N., R.A. +11.0min. (approx.) |
| 42x256 L
| Fuzzy spot elongated PA 170-350, bluish, Tail 5' PA 110 Comparison stars: 53, 9, 4 Ori. |
| May 17.24 |
N. Biver, H. Dahle
| Slightly hazy, few clouds
| 5:45 UT | 6:04 UT (alt. 63' +/-5')
| 5:47.3 UT: R.A.=4h54.65 (+-2') (J2000.0) Dec.=+1115' (+-2') |
| | Measured 11.8' (+-1.8') PA 100 (+-5) from 6 ori. |
| 42x and 169x256 L
| Elongated PA 170-350, clearly fuzzy and bluish,
Narrow Tail 10' PA 100, Comparison stars: 9, 4, 6 and 7 Ori. |
| May 18.24 |
N. Biver, H. Dahle
| Hazy on 1-2 only, no clouds (nearby)
| 5:45.5 UT | 6:04 UT (alt. 68' +/-5')
| 5:59.3 UT: R.A.=5h03.1 (+-4') (J2000.0) Dec.=+0904' (+-3') |
| | Measured 70' (+-1.5') PA 249 (+-1.5) from 13 ori. |
| | 5:47.7 Measured 40' (+-4') PA 290 (+-5) from a 7.4 mag. star. |
| 42x and 169x256 L
| Distinct pseudo-nucleus, broad tail with
Narrow Tail 0.2 PA 115, Comparison stars: 28, 31, 16 and 14 Ori. |
| May 19.24 |
N. Biver
| Clear skies (slighly hazy, but nice blue-green flash)
| 5:40.3 UT | ~6:06 UT
| 5:47.4 UT: R.A.=5h10.72 (+-0.06m) (J2000.0) Dec.=+0659.0' (+-0.8') |
| | 4 measurements with SAO112475,112500,112511,112512. |
| 42x and 84x256 L
| Distinct pseudo-nucleus, coma brighter on Sunward side,
broad tail PA 100 to 130 with Narrow Tail 0.2 PA 130, Comparison stars: 28, 34, 31, 16 and 14 Ori. |
| May 20.24 |
N. Biver, O.Guyon
| Slighly hazy, few, shrinking, clouds
| 5:35.0 UT | ~6:02 UT
| 5:51.0 UT: R.A.=5h18.0 (+-0.18m) (J2000.0) Dec.=+0449' (+-2.5') |
| | 2 measurements with SAO112556. |
| 42x and 84x256 L
| Faint tail 0.15 PA 140; Comparison stars: 22, 23, 34, 31 Ori., SAO112556, SAO112708 - (Ref. HV) |
| May 22.24 |
N. Biver
| Some clouds, and cirrus at the horizon
| 5:53.5 UT | 5:58 UT
| - |
| 42x256 L
| Comet more diffuse and hard to see (Cirrus / not much easier than a comet of m1=13.5 in a dark sky); Comparison stars: 28, 31 Ori., SAO132233 - (Ref. HV) |
I may now put an end to these observations, since mag. estimates are certainly
biased, due to absorption and bright background which makes the comet appear
smaller than it is - though comparison stars are observed at same altitude.
May 21.0 UT.
Note: I have seen some confusion (e.g. IAUC6910) about the PA of the tail(s):
shouldn't we measure it CCW from the direction of the North (not CW from the
South, i.e. PA=130 instead of 50)?
[GIF 33 K] May 18.2: 14 x 14' Drawing (25.6cm L 84x) 
[GIF 51 K] May 19.2: 14 x 14' Drawing (25.6cm L 84x)