Date: Tue, 24 Aug 1999 08:26:13 -0600 (MDT)
From: Richard Canfield <canfield@helicity.physics.montana.edu>
Subject: MMOC002 Target 

The campaign "Eruptive Flares Associated with Sigmoids during WSM3" (http://solar.physics.montana.edu/max_millennium/ops/op002/op002.html) will continue to follow the backward-S sigmoid in AR 8668, for which coordinates were N22 W50 at 2400 UT on 23-Aug-99.

The latest SXT images show a cusp whose base arches over the southern part of the sigmoid. The cusp is not present at 23-Aug-99 11:00:28, faint at 24-Aug-99 05:46:02, and brighter at 24-Aug-99 07:21:34. These can be seen in the 20 most recent Yohkoh SXT composite images at ftp://isass5.solar.isas.ac.jp/pub/sxt_co/quick/thumb_grid.html

Sarah Gibson provides the following information about pointing:

>From: Sarah Gibson <sg273@damtp.cam.ac.uk>
>To: [snip]
>Subject: coordinate update for Aug. 25/26
>
>An image of a BBSO H-alpha image from 16:10 UT on August
>23, with overlaid crosses marking the center of the sigmoid
>for August 24, 25, and 26 can be found at
>
>http://www.damtp.cam.ac.uk/user/sg273/WSM3/tod24bbso.gif
>
>The coordinates of the crosses for August 25 and 26 are
>
>August 25 14:00 UT x = 892", y = 210"
>August 26 14:00 UT x = 949", y = 193"
>
>The coordinates for August 25 14:00 UT are nearly
>identical to those sent yesterday, and the 4"X4"
>box at the limb is the same as yesterday, shifted slightly
>from the Aug 25 center in order to get loops extending
>out above the limb, and has the following suggested
>central coordinates for observers with limited f.o.v.:
>
>(SHIFTED FOR OBSERVERS WITH LIMITED F.O.V.)
>
>August 25 14:00 UT x = 936", y=209"
>
>On August 26, the sigmoid will essentially be at the limb -
>the grid on the BBSO image is equally spaced 15 degrees
>latitude and longitude, so from this we see that the sigmoid
>will be at approximately
>
>280 degrees polar angle -- on August 26, 14:00 UT