N. Mirabal, J. P. Halpern, J. Kemp, & D. J. Helfand (Columbia U.)
report on behalf of the MDM Observatory GRB follow-up team:

"The potential K-band counterpart of GRB 000418 reported by
Klose et al. (GCN #645) is present in an R-band image which
we obtained on the MDM 2.4m telescope on April 21, 03:33 UT.
Its position is (J2000) RA 12 25 19.30, Dec. +20 06 11.1,
with an uncertainty of 0."5.  Under non-photometric conditions
we measure R = 21.52 +/- 0.12 for this candidate, referenced
to a USNO star at (J2000) RA 12 25 25.62, Dec. +20 04 57.8 which
is listed as R = 15.4.  An additional systematic uncertainty
of 0.2 mag should be assumed based on the dispersion among
other USNO star magnitudes in this field.

Further observations are needed to determine if this object
is fading.

This message may be cited."

N. Mirabal, J. P. Halpern (Columbia U.), R. M. Wagner (Ohio State U.)
report on behalf of the MDM Observatory GRB follow-up team:

"We reobserved the suggested afterglow candidate for GRB 000418
(Klose et al., GCN #645) in the R-band using the MDM 2.4m telescope.
The object at position (J2000) RA 12:25:19.30, Dec. +20:06:11.1
has faded to R = 22.59 +/- 0.23 on April 27.26 UT from our previous
detection at R = 21.52 +/- 0.12 on April 21.15 UT (Mirabal et al.,
GCN #646).  The second measurement was made with a non-standard broad
R filter.  Both magnitudes are referenced to the same USNO star at 
(J2000) RA 12:25:25.62, Dec +20:04:57.8 which is listed as R = 15.4.
The corresponding power-law decay index would be -0.84 +/- 0.20.
The magnitude of the decline and its rate are plausible for a GRB
afterglow, but further confirmation is desired.

This message may be cited."

N. Mirabal, J. P. Halpern (Columbia U.), R. M. Wagner (Ohio State U.)
report on behalf of the MDM Observatory GRB follow-up team:

"We obtained additional R-band images of the afterglow candidate
for GRB 000418(Klose et al., GCN #645) using the
MDM 2.4m telescope. The object located at (J2000) RA 12:25:19.30,
Dec. +20:06:11.1 has an estimated magnitude R = 22.8 +/- 0.31 on
April 28.3 UT, this magnitude is referenced to USNO star
(J2000) RA 12:25:25.62, Dec +20:04:57.8 (R = 15.4).
The decline is consistent with the -0.84 +/- 0.2 power-law
derived from previous detections (Mirabal et al., GCN #646,#650). In
addition we note that the OT appears to be slightly extended which might
be an indication of residual light from an underlying host galaxy.

This message may be cited."