GRB 000926 was detected by three instruments in the Interplanetary Network (IPN: Ulysses, Konus-WIND, and NEAR), and localized to a 35 arcmin² error box which was circulated via the GRB Coordinates Network (GCN) 20.3 hours after the burst (Hurley 2000). The Earth-crossing time for the burst was September 26.9927 UT. As observed by Ulysses, it had a duration of approximately 25 s (placing it in the "long duration'' burst category), a revised 25-100 keV fluence of $6.2\times 10^{-6}$ erg cm^-2, and a revised peak flux over 0.25 s of $8.6\times 10^{-7}$ erg cm^-2 s.

The error-box of GRB 000926 (Hurley 2000) was observed in the R-band with the 2.56-m Nordic Optical Telescope (NOT) and the Calar Alto (CA) 2.2-m telescope on 2000 September 27.85 UT (20.64 hours after the burst). Comparing with red Palomar Optical Sky Survey II exposures an OT was found in the error box (Gorosabel et al. 2000; Dall et al. 2000). Spectra were obtained at the NOT on both September 27 and September 28; these spectra revealed a strong metal absorption system at a redshift of $z=2.0375\pm0.0007$ , which in all likelihood is due to gas in the GRB host galaxy (Møller et al., in prep). The OT was observed during the following weeks at the NOT, CA and also with the Isaac Newton Telescope (INT), the 1.0 m telescope at the US Naval Observatory at Flagstaff Station (USNOFS), and in the IR with the 8.2-m Subaru telescope and the 3.8-m United Kingdom Infrared Telescope (UKIRT). The logs of optical and IR observations are given in Tables 2 and 5. A finding-chart and R-band images of the OT at three different epochs are shown in Fig. 1.

**Table 1:** *UBVRI* magnitudes for the four secondary calibration stars A-D.
star/filter	U	B	V	R	I
A	$19.070\pm0.069$	$18.499 \pm 0.021$	$17.635 \pm 0.010$	$17.025 \pm 0.021$	$16.553 \pm 0.028$
B	$19.596\pm 0.119$	$18.662 \pm 0.025$	$17.508 \pm 0.010$	$16.811 \pm 0.022$	$16.265 \pm 0.030$
C	$18.920\pm 0.086$	$19.047 \pm 0.036$	$18.449 \pm 0.016$	$18.026 \pm 0.028$	$17.655 \pm 0.038$
D	-	$20.822 \pm 0.141$	$19.459 \pm 0.045$	$18.529 \pm 0.065$	$17.694 \pm 0.069$

Table 2: The journal of NOT, CA, INT and USNOFS observations and the results of the photometry.
UT Obs. mag Seeing Exposure time

(arcsec) (sec)

U-band^a

Sep. 27.9484 NOT $20.437 \pm 0.047$ 1.35 1000

Sep. 28.8291 NOT $21.732 \pm 0.224$ 1.29 450

Sep. 29.8493 NOT $22.816 \pm 0.131$ 1.16 900

B-band^a

Sep. 27.8881 NOT $20.432 \pm 0.034$ 1.00 100

Sep. 27.9673 CA $20.733 \pm 0.034$ 2.42 1200

Sep. 27.9894 CA $20.727 \pm 0.038$ 2.41 1200

Sep. 28.0057 CA $20.796 \pm 0.039$ 2.59 1200

Sep. 29.8346 NOT $22.890 \pm 0.122$ 1.19 500

Sep. 29.8688 NOT $22.856 \pm 0.082$ 1.20 600

Sep. 30.8688 NOT $23.489 \pm 0.097$ 1.20 1200

V-band^a,b

Sep. 27.906 INT $19.906 \pm 0.0135$ 1.0 300

Sep. 27.910 INT $19.933 \pm 0.0135$ 1.0 300

Sep. 27.915 INT $19.936 \pm 0.0141$ 1.0 300

Sep. 27.9237 CA $19.910 \pm 0.025$ 2.22 900

Sep. 29.9557 NOT $22.324 \pm 0.121$ 1.29 600

Sep. 30.839 INT $22.987 \pm 0.096$ 1.0 600

R-band^a,b

Sep. 27.8547 NOT $19.326 \pm 0.015$ 0.83 300

Sep. 27.8594 NOT $19.343 \pm 0.011$ 0.84 300

Sep. 27.8639 NOT $19.322 \pm 0.011$ 0.86 300

Sep. 27.8651 CA $19.329 \pm 0.034$ 1.44 900

Sep. 27.8684 NOT $19.342 \pm 0.008$ 0.82 300

Sep. 27.8729 NOT $19.349 \pm 0.011$ 0.87 300

Sep. 27.8774 NOT $19.366 \pm 0.010$ 0.90 300

Sep. 27.8820 NOT $19.349 \pm 0.010$ 0.91 300

Sep. 27.892 INT $19.394 \pm 0.022$ 1.0 300

Sep. 27.896 INT $19.411 \pm 0.022$ 1.0 300

Sep. 27.901 INT $19.421 \pm 0.023$ 1.0 300

Sep. 27.9109 CA $19.452 \pm 0.020$ 2.01 900

Sep. 27.9658 NOT $19.538 \pm 0.011$ 1.06 300

Sep. 27.9705 NOT $19.526 \pm 0.014$ 1.09 300

Sep. 27.9750 NOT $19.567 \pm 0.015$ 1.01 300

Sep. 27.9795 NOT $19.542 \pm 0.017$ 1.02 300

Sep. 27.9840 NOT $19.553 \pm 0.023$ 1.00 300

Sep. 28.097 USNOFS $19.71 \pm 0.03$ 2.0 3 $\times$ 600

Sep. 28.8356 NOT $20.723 \pm 0.025$ 1.06 300

Sep. 28.8911 NOT $20.774 \pm 0.036$ 1.05 500

Sep. 28.9595 NOT $20.875 \pm 0.036$ 1.19 600

Sep. 29.110 USNOFS $20.94 \pm 0.04$ 1.8 3 $\times$ 600

Sep. 29.138 USNOFS $20.95 \pm 0.04$ 1.9 4 $\times$ 600

Sep. 29.170 USNOFS $21.08 \pm 0.05$ 2.0 4 $\times$ 600

Sep. 29.8414 NOT $21.740 \pm 0.043$ 0.86 600

Sep. 29.9478 NOT $21.897 \pm 0.083$ 1.17 600

Sep. 30.83 NOT $22.494 \pm 0.070$ 0.90 2400

Oct. 2.84 NOT $23.514 \pm 0.153$ 1.14 1500

Oct. 6.85 NOT - 1.29 2700

Oct. 27.84 NOT - 1.10 4700

Nov. 3.84 NOT - 1.26 2400

Nov. 4.84 NOT - 1.12 3600

I-band^a,b

Sep. 27.919 INT $18.959 \pm 0.029$ 1.0 300

Sep. 27.924 INT $18.992 \pm 0.029$ 1.0 300

Sep. 27.929 INT $19.007 \pm 0.029$ 1.0 300

Sep. 27.9370 CA $18.861 \pm 0.032$ 2.22 900

Sep. 27.9433 NOT $19.014 \pm 0.014$ 0.72 600

Sep. 27.9510 CA $18.890 \pm 0.022$ 2.16 900

Sep. 29.8608 NOT $21.218 \pm 0.051$ 0.79 600

Sep. 30.839 INT $21.956 \pm 0.029$ 1.0 600

$\textstyle \parbox{8.8cm}{ $^a$\space Only for the NOT $R$ --band measurements ... ...ll Bessel; CA -- all Johnson; INT: Sloan i, Harris R \& V; USNOFS : Bessel R. }$

**Table 2:** The journal of NOT, CA, INT and USNOFS observations and the results of the photometry.
UT	Obs.	mag	Seeing	Exposure time
			(arcsec)	(sec)

U-band^a
Sep. 27.9484	NOT	$20.437 \pm 0.047$	1.35	1000
Sep. 28.8291	NOT	$21.732 \pm 0.224$	1.29	450
Sep. 29.8493	NOT	$22.816 \pm 0.131$	1.16	900
B-band^a
Sep. 27.8881	NOT	$20.432 \pm 0.034$	1.00	100
Sep. 27.9673	CA	$20.733 \pm 0.034$	2.42	1200
Sep. 27.9894	CA	$20.727 \pm 0.038$	2.41	1200
Sep. 28.0057	CA	$20.796 \pm 0.039$	2.59	1200
Sep. 29.8346	NOT	$22.890 \pm 0.122$	1.19	500
Sep. 29.8688	NOT	$22.856 \pm 0.082$	1.20	600
Sep. 30.8688	NOT	$23.489 \pm 0.097$	1.20	1200
V-band^a,b
Sep. 27.906	INT	$19.906 \pm 0.0135$	1.0	300
Sep. 27.910	INT	$19.933 \pm 0.0135$	1.0	300
Sep. 27.915	INT	$19.936 \pm 0.0141$	1.0	300
Sep. 27.9237	CA	$19.910 \pm 0.025$	2.22	900
Sep. 29.9557	NOT	$22.324 \pm 0.121$	1.29	600
Sep. 30.839	INT	$22.987 \pm 0.096$	1.0	600
R-band^a,b
Sep. 27.8547	NOT	$19.326 \pm 0.015$	0.83	300
Sep. 27.8594	NOT	$19.343 \pm 0.011$	0.84	300
Sep. 27.8639	NOT	$19.322 \pm 0.011$	0.86	300
Sep. 27.8651	CA	$19.329 \pm 0.034$	1.44	900
Sep. 27.8684	NOT	$19.342 \pm 0.008$	0.82	300
Sep. 27.8729	NOT	$19.349 \pm 0.011$	0.87	300
Sep. 27.8774	NOT	$19.366 \pm 0.010$	0.90	300
Sep. 27.8820	NOT	$19.349 \pm 0.010$	0.91	300
Sep. 27.892	INT	$19.394 \pm 0.022$	1.0	300
Sep. 27.896	INT	$19.411 \pm 0.022$	1.0	300
Sep. 27.901	INT	$19.421 \pm 0.023$	1.0	300
Sep. 27.9109	CA	$19.452 \pm 0.020$	2.01	900
Sep. 27.9658	NOT	$19.538 \pm 0.011$	1.06	300
Sep. 27.9705	NOT	$19.526 \pm 0.014$	1.09	300
Sep. 27.9750	NOT	$19.567 \pm 0.015$	1.01	300
Sep. 27.9795	NOT	$19.542 \pm 0.017$	1.02	300
Sep. 27.9840	NOT	$19.553 \pm 0.023$	1.00	300
Sep. 28.097	USNOFS	$19.71 \pm 0.03$	2.0	3 $\times$ 600
Sep. 28.8356	NOT	$20.723 \pm 0.025$	1.06	300
Sep. 28.8911	NOT	$20.774 \pm 0.036$	1.05	500
Sep. 28.9595	NOT	$20.875 \pm 0.036$	1.19	600
Sep. 29.110	USNOFS	$20.94 \pm 0.04$	1.8	3 $\times$ 600
Sep. 29.138	USNOFS	$20.95 \pm 0.04$	1.9	4 $\times$ 600
Sep. 29.170	USNOFS	$21.08 \pm 0.05$	2.0	4 $\times$ 600
Sep. 29.8414	NOT	$21.740 \pm 0.043$	0.86	600
Sep. 29.9478	NOT	$21.897 \pm 0.083$	1.17	600
Sep. 30.83	NOT	$22.494 \pm 0.070$	0.90	2400
Oct. 2.84	NOT	$23.514 \pm 0.153$	1.14	1500
Oct. 6.85	NOT	-	1.29	2700
Oct. 27.84	NOT	-	1.10	4700
Nov. 3.84	NOT	-	1.26	2400
Nov. 4.84	NOT	-	1.12	3600
I-band^a,b
Sep. 27.919	INT	$18.959 \pm 0.029$	1.0	300
Sep. 27.924	INT	$18.992 \pm 0.029$	1.0	300
Sep. 27.929	INT	$19.007 \pm 0.029$	1.0	300
Sep. 27.9370	CA	$18.861 \pm 0.032$	2.22	900
Sep. 27.9433	NOT	$19.014 \pm 0.014$	0.72	600
Sep. 27.9510	CA	$18.890 \pm 0.022$	2.16	900
Sep. 29.8608	NOT	$21.218 \pm 0.051$	0.79	600
Sep. 30.839	INT	$21.956 \pm 0.029$	1.0	600

Radio and X-ray afterglow measurements have been reported by Frail et al. (2000) and by Piro et al. (2000). Optical afterglow measurements have also been reported by Price et al. (2001). This paper includes preliminary reduced NOT and CA observations from Hjorth et al. (2000), Fynbo et al. (2000b) and Gorosabel et al. (2000) for which the finally reduced data appear in this paper.

2 Observations