See also the Recommendations for stellar-magnitude sources.
The International Comet Quarterly OBSERVATION KEYS [2010 Jan. 6] TABULATION OF COMET OBSERVATIONS MAGNITUDE METHOD KEY Following are key letters for the methods used in making total visual magnitude estimates (these appear in column MM in TABULATION OF COMET OBSERVATIONS): a = orange filter used on SOHO spacecraft with C2 and C3 coronagraphs, spanning wavelength range 540-640 nm (see Biesecker and Green 2002, ICQ *24*, 95) B = VBM (Van Biesbroeck-Bobrovnikoff-Meisel) or simple Out-Out method [formerly noted in the ICQ as the Bobrovnikoff method] b = VBM method using RCA #4549 image intensifier (see method 'e' below) C = unfiltered total CCD magnitude (fairly well approximates the Johnson V band) c = unfiltered nuclear CCD magnitude (fairly well approximates the Johnson V band) D = Cousins B filter E = Extrafocal-Extinction (or Beyer) method (cf. M. Beyer 1968, Astron. Nachr. 291, 257) e = Extrafocal-Extinction (or Beyer) method using RCA #4549 image intensifier (cf. D. A. Sutherland 1974, J.A.L.P.O. 24}, 218) F = total magnitude obtained using Meade CCD interference filter CM-500 Visible (infrared blocking filter), supplied with their Pictor 416 CCD camera [ICQ 123] f = "nuclear" magnitude obtained using Meade CCD interference filter CM-500 Visible (infrared blocking filter), supplied with their Pictor 416 CCD camera [ICQ 123] G = CCD magnitude with a Corion NR-400 "minus-infrared" filter; William Liller, who used this combination, says that it "gave a very nice broadband-V passband" (see Liller 2001, ICQ *23*, 93) g = CCD magnitude with Gunn g filter (+ RCA CCD w/ observer LAR) H = Cousins I filter with CCD I = In-focus i = visual observation using an image intensifier (observer MER used RTC XX 1390 image intensifier, which has unfiltered sensitivity from 300-950 nm) J = Kron-Cousins V filter employed (peak transmission at 550 nm) [initiated by observer ROQ] j = Kron-Cousins V filter employed (m2 estimate) K = clear filter used on SOHO spacecraft with C3 coronagraph, spanning wavelength range 400-850 nm (see Biesecker et al. 2002, Icarus 157, 323) [use beginning in July 2001 (see ICQ 123); note that the old "Keen method" deploying "K" as MM was changed to a special-notes code] k = CCD magnitude with Cousins R filter L = photoelectric B l = CCD magnitude with a Wratten 25 (red) filter, introduced in 1996 by William Liller "to reduce the atmospheric extinction"; he used the letter "R" to refer to them (Liller 1997, Planet. Space Sci. 45, 1507) M = Modified-Out method discussed by C. S. Morris (ICQ 2, 69) N = called magnitude of nucleus or condensation, but usually some ambiguity as to whether or not the magnitude refers more to a total magnitude instead (used mostly with pre-1970 observations extracted from the literature) O = Out-of-focus method (specific type not mentioned) [intended for historical observations only] o = visual extrafocal comparison using RCA #4549 image intensifier (see method 'e', above) P = photographic [intended for historical observations only] p = photographic with Kodak 2415 film Q = "out-out"; supposed to be same as VBM method, but it's not always clear what observer intended [intended for historical observations only] q = R-band magnitude for nuclear condensation R = photoelectric R r = CCD magnitude with Gunn r filter S = VSS (Vsekhsvyatskii-Steavenson-Sidgwick) or In-Out method [formerly called the Sidgwick method in the ICQ] s = VSS method using image intensifier (see method 'e', above, for observer Sutherland, who used an RCA #4549 intensifier; for observer MER, see method 'i', above) T = Magnitude estimated from a TV monitor t = total visual magnitude (no other information provided; historical obs. only) U = photoelectric U u = CCD-derived V nuclear magnitudes (m2) V = photoelectric V v = photoelectric with filters to match visual W = photoelectric (no band given) w = 1P21 photometer + Kodak W64 filter [R. B. Minton writes (1974) that "this surface-filter combination closely matches the spectral response of the dark-adapted eye"]. X = ortochromatic film + yellow filter, which is a system very close to the V band [according to observer MIL02] Y = CCD magnitude with Wratten No. 15 (yellow) filter, "which gives an effective response at about 680 nm (and blue cutoff at 520 nm)" [initiated by observer ROQ] Other notes: Photographic magnitudes are now indicated under MM by the letter "P", and photoelectric magnitudes are indicated there by the band letter ("L" for B, "U" for U, and "V" for V; new letters will be assigned as necessary). Photoelectric magnitudes with stated errors of > ± 0.3 or greater get a colon (:) listed after the magnitude, as of 1982 data; such data stated as ± 0.3 gets a '+' instead of a colon. The letter "W" under MM stands for photoelectric magnitudes in which no specific band was mentioned (visual band assumed); this will no longer be acceptable for future observations, but is retained for observations which already exist in the ICQ master file. SPECIAL NOTES KEY NOTE: A left bracket, [, before a magnitude indicates the comet was not seen. (If the comet was seen, and an observer simply says that it was fainter than a given magnitude, a '>' sign is used, instead.) Published after the date in the ICQ (and listed in computer and on magnetic tape files between the reference and the observer code) are symbols and letters to indicate special observing conditions or factors [NOTE: some of these symbols have not yet appeared (and some will never appear) in the printed ICQ]: * = an observation completely replacing one previously published in the ICQ & = comet observed at altitude 20 deg or less with no atmospheric extinction correction applied ! = observation corrected for atmospheric extinction in a proper manner by the observer; prior to September 1992, this was the standard symbol for noting extinction correction, but following publication of the extinction paper (July 1992 ICQ), this symbol is only to be used to denote corrections made using procedures different from that outlined in ICQ 14, 55-59, and then only for situations where the observed comet is at altitude > 10. $ = comet observed at altitude 10 degrees or lower, observations corrected by the observer using procedure in ICQ 14, 55-59 (July 1992). # = minor data change made in archive only (change published in textual form in ICQ, or not published at all in ICQ) [USED ONLY INTERNALLY] + = supplementary descriptive information also published in ICQ % = comparison star(s) were reduced to visual magnitudes via their B-V colors using one of the formulae in the ICQ Guide to Observing Comets, first ed., p. 65 (Howarth and Bailey 1980, or Stanton 1981) A = Pogson's "step method" or "Argelander method" stated; no other info provided [for historical observations only] a = [formerly 'A'] atmospheric extinction correction applied by observer using Table Ia of Green (1992, ICQ 14, 55-59). B = a V magnitude based on a conversion from a B photoelectric magnitude (with same qualifications as for C, above) b = same as B, except that B-V was not measured, but assumed (usually B-V is about +0.7) C = a V magnitude based on a conversion from an R photoelectric magnitude (the observer must state a proper conversion formula, V-R); if an R magnitude is given with errors > ± 0.2 mag, then V gets a colon (:) after the magnitude. c = same as C, except that V-R was not measured, but assumed (usually V-R is about +0.52) d = local extinction coefficients derived for local atmospheric conditions, and used in application of atmospheric-extinction correction; the value A' of Green (1992, ICQ 14, 55-59) is thus re-computed, but the remaining procedures of that paper are followed f = single 50-mm binocular objective lens was used close to the eye for defocussing images G = Naked eye estimate, with glasses used to defocus comparison stars (for bright comets only) i = ambiguity concerning which instrument was used to make coma diameter, DC, and tail information; the specified instrument was that used for the magnitude estimate I = use of infrared-block filter with CCD; supposedly gives response similar to that of an unfiltered CCD K = "Modified" VSS method, using binoculars with the comet in-focus in one eyepiece and with the comparison stars out-of-focus in the other eye- piece (cf. R. A. Keen 1985, ICQ 7, 48) [originally used as a MM code] l = limiting stellar magnitude for a CCD observation in which the comet was not detected r = binoculars were reversed, such that one looked through the (larger) objective lens acting as the eyepiece, and the eyepiece acted as the objective aperture [for the magnitude estimates of bright comets] s = [formerly 'S'] atmospheric extinction correction applied by observer using Table Ic of Green (1992, ICQ 14, 55-59). S = CCD photometry with an R60 filter (expected to be similar to, but not the same as, that of a standard R filter) T = a V magnitude based on a conversion from a Thuan-Gunn g, r, or i photo- electric magnitude (with same qualifications as for C, above); cf. Jewitt and Danielson 1984, Icarus 60, 435. t = exposure on Kodak T-Max (b&w) film using an image intensifier (for observer MER, see method 'i', above) w = [formerly 'W'] atmospheric extinction correction applied by observer using Table Ib of Green (1992, ICQ 14, 55-59). x = denotes that a secondary source was consulted for primary-source magnitudes; an example is extracting Tycho-catalogue magnitudes from the amateur software "Guide 6.0". THE SECONDARY SOURCE SHOULD ALWAYS BE SPECIFICALLY CITED, and will appear in the descriptive information in the ICQ to supplement the tabulated data. INSTRUMENT KEY A = camera lens B = binoculars C = Cassegrain reflector D = Schmidt reflector E = naked eye F = twin catadioptric Newtonian binocular G = coronagraph (introduced for the solar-orbiting SOHO LASCO C3 coronagraph, which has an external occulter that "shadows the small 9.6-mm entrance aperture from direct sunlight" -- SOHO website); it is essentially a refracting instrument [ICQ 119] H = hyperboloid astro-camera I = Multiple-Mirror Telescope, F. L. Whipple Observatory (when the f-ratio was 9, at the Cassegrain focus) J = Jones-Bird telescope* K = Klevtsov-Cassegrain (essentially a Maksutov-type instrument but having a sub-aperture corrector after the secondary mirror, instead of the full aperture corrector in front of the primary) L = Newtonian reflector M = Maksutov reflector N = 1x monocular made by taking two identical lenses and using one as an objective and one as an eyepiece O = opera glass P = prime focus of a reflector q = "small telescopes" with aperture in range 4-10 inches (see note under instrument "r", below) [FOR HISTORICAL DATA ONLY] Q = "for observations with the largest telescopes" (see note under instrument "r", below) [FOR HISTORICAL DATA ONLY] r = "small telescopes and finders" with aperture not exceeding 4 inches (after Bobrovnikoff 1941, Contrib. Perkins Obs. No. 15, p. 5) [FOR HISTORICAL DATA ONLY] R = refractor S = Schmidt-Newtonian telescope T = Schmidt-Cassegrain reflector U = coude focus of a reflector V = Volosov-Newtonian reflecting telescope (has two lenses -- double-convex and planoconcave) with a Newtonian spherical mirror; designed by Pechatnikova and Volosov in Leningrad in 1943 (information provided by V. L. Korneev in 2000) W = Wright-Schmidt reflector Y = Ritchey-Chretien telescope * According to Henk Feijth, several members of the Dutch Comet Section use a 10-inch-aperture (25.4-cm) Jones-Bird telescope, which is a modi- fied Newtonian with a spherical f/4 primary mirror: "Just before the light strikes the flat after being reflected, it passes through a Barlow-like achromatic lens that corrects the spherical aberration of the primary mirror. The system is f/6 and also corrected for coma." CCD DATA KEYS [given in brackets is the ICQ reference where the key was announced] CCD cameras: Key CCD Camera AAL Artemis 285AL-a (see http://www.artemisccd.co.uk/icx285.htm) [ICQ 144] Ap4 APOGEE AP47p [ICQ 124] Ap7 Apogee Ap-7 or Ap-7p [ICQ 124] Ap9 Apogee Alta U9000 (see http://www.ccd.com/alta_u9000.html) ATI ATIK 2HS BT1 BITRAN BT-11 [ICQ 124] CKD Canon Kiss Digital camera [ICQ 144] Dil DillCam (used on 2.0-m Faulkes Telescope-North) [ICQ 136] DSI Meade DSI Pro [ICQ 144] FLD Finger Lakes Instrumentation (FLI) Dream Machine [ICQ 144] FLI Finger Lakes Instrumentation (FLI) CM91E [ICQ 144] FL9 Finger Lakes Instrumentation (FLI) PL09000 [http://www.flicamera.com/fli/proline.html] H24 Hi-Sis 24 [ICQ 121] MCV Mutoh CV-16II or CV-16 [ICQ 123] MX9 Starlight MX-916 [ICQ 121] Nik Nikon D50 digital SLR camera PIC Pictor 416 [ICQ 123] PIX Pictor 216 XT [ICQ 128] PSI Photometrics Star-I [ICQ 124] QHY QHY-6 (website http://qhyccd.com/) [ICQ 144] S1C a Russian CCD camera (chip unknown; via BOR04, BAR06) [ICQ 132] SC2 SOHO LASCO C2-coronagraph camera [ICQ 123] SC3 SOHO LASCO C3-coronagraph camera [ICQ 123] SE7 SBIG ST-7E [ICQ 124] SE8 SBIG ST-8E [ICQ 124] ST0 SBIG STL-6303 ST1 SBIG ST-1001E [ICQ 124] ST2 SBIG ST-2000XM [ICQ 124] ST3 SBIG STL1301E [ICQ 144] ST4 SBIG ST402 ST6 SBIG ST-6V [ICQ 121] ST7 SBIG ST-7 [ICQ 121] ST8 SBIG ST-8 [ICQ 121] ST9 SBIG ST-9E [ICQ 121] STE StarLight Express SXL8 [ICQ 140] STL SBIG STL-11000M [ICQ 140] STM SBIG ST-10XME STT SBIG ST-10E STX SBIG ST8-XME SXV Starlight Xpress SXV-H9 [ICQ 142] CCD camera chips: Key CCD Camera Chip CAC 22.7-mm x 15.1-mm (APS-C) CMOS for Canon Kiss Digital camera [ICQ 144] EEV 2048x2048 EEV 42-40 [ICQ 136] EXV Sony ExViewHAD tm [ICQ 144] F48 Fairchild CCD486 4000x4000 CCD [ICQ 140] ICX Sony ICX259AL [ICQ 144] ICY Sony ICX285AL [ICQ 142] ICZ Sony ICX-424AL K10 KAF-1001E (Kodak) [ICQ 124] K16 KAF-1600 [ICQ 123] K26 KAF-0261E [ICQ 121] K32 KAF-3200ME K40 KAF-0400 [ICQ 121] K41 KAF-0401E [ICQ 123] K42 KAF-0402ME (Kodak) [ICQ 128] K4E KAF-0400E [ICQ 123] K6E KAF-1602E (Kodak) [ICQ 124] K6F KAF-6303E K6M KAF-1603ME (Kodak) KA0 KAF-0401 (Kodak) [ICQ 124] KA1 KAI-11000M (Kodak) [ICQ 140] KA2 Kodak KAF-1301E [ICQ 144] KA9 KAF-09000 KAI KAI-2000M (Kodak) [ICQ 124] M47 Marconi 47-10 [ICQ 124] PF1 Philips FT12 [ICQ 140] SAL Sony 285AL [ICQ 144] SIA SIA502AB (SITe); formerly called TK512 (Tektronics) [ICQ 124] T24 TC-241 CCD chip (UV enhanced - CCD camera type SBIG ST-6V) [ICQ 123] T25 TC255 [ICQ 120] TH7 TH7883CDA (Thomson) [ICQ 124] TK1 thinned TK1024, Tektronik 1K 1024x1024 [ICQ 121] TK2 Tektronik TK-1024-AV [ICQ 144] Computer software used for photometric reduction of CCD images: Key Software name A32 Astrometrica 3.25 [ICQ 123] AIP AIP for Windows (Berry and Burnell) [ICQ 142] AFo Astrometrica used with Focas software (see information on WWW at http://astrosurf.com/cometas-obs/_Articulos/Focas_i/Focas_i.htm) [ICQ 133, 13] A41 Astrometrica 4.1 [ICQ 124] AfP ASTROART for Photometry [ICQ 123] AA3 ASTROART for Photometry, version 3.0 [ICQ 140] FPr FitsPro [ICQ 120] GAI GAIA software ver. 2.5-3 (C) 1997-2000 Central Laboratory of the Research Councils (U.K.), authors: Peter W. Draper and Norman Gray e-mail: email@example.com [ICQ 123] IRA IRAF [ICQ 136] IPL IPLab [ICQ 124] Izm Izmccd software [http://izmccd.puldb.ru/index2.htm] MIm MaxIm DL/CCD [ICQ 124] Mir Mira OPS CCDOPS (SBIG) [ICQ 121] PHO PHOTOM software developed by a student of R. D. Schwartz at the University of Missouri at St. Louis to reduce aperture measurements, and Schwartz's own software program to produce magnitudes SI3 StellaImage 3 [ICQ 124] SI4 StellaImage 4 [ICQ 126] SI5 StellaImage 5 [ICQ 134] SI0 Stella Image (Japanese software programmed by K. Kadota and sold by Astro Art Co.) [ICQ 144] NOTE: We are advised that software such as "Guide 6.0", "Guide 7.0" [ICQ 121], "Guide 8.0", and "The Sky (ver. 5)" [ICQ 121] do not have any means to measure magnitudes (they have only lists of comparison-star magnitudes), so key codes "G70" and "Sky" are withdrawn. MAGNITUDE-REFERENCE KEY See the table at this website.