Asteroid (99) Dike Occultation Nov. 17, s. Virginia to s. Arizona

The occultation of UCAC2 44112722 by (99) Dike was observed from Roanoke, VA and Palominas Obs., AZ

The path prediction was quite accurate, confirmed by nearby observers who had misses near both limits

New: 2005 Nov. 17

From: David Dunham [dunham@starpower.net]
Sent: Thursday, November 17, 2005 3:13 AM
To: Michael R. Good
Cc: IOTAoccultations@egroups.com
Subject: (99) Dike: CCD drift occultation at Roanoke, VA

Michael,
      Many thanks for this observation.  With Bruce
Gary's observation, it shows that the predicted path
was quite accurate (I wish the Nov. 15 Tercidina path had
been that accurate!) and with bracketing negative
observations, the path is quite well-determined:

Dist. = distance in km from S. Preston's predicted
central line, + north, - south:

Dist.  Result, observer

+44 no occ'n, Derald Nye, Corona de Tucson, AZ
+31 2.36s occ'n, Michael Good, Roanoke, VA (your observation)
-27 short occ'n, Bruce Gary, Hereford, AZ
-31 ?, Tim Farris, Nashville, TN, prob. no occ'n, need to check
-35 no occ'n, Doug Snyder, Palominas, AZ

Yes, It's very late here, so later we'll see how your time
compares with Bruce Gary's time, to see if the actual
occultation was later than predicted.  I'll try to post
your images on my Web site many hours from now.  Prediction 
information can be found on Steve Preston's Web site.
Later I will add Derek Breit's station list here.

David

At 02:23 AM 11/17/2005, you wrote:
>David,
>
>I recorded the occultation of (99) Dike using CCD Drift.
>Two images are here: 2x2 bin of field, 1x1 bin of drift.
>
>    04h 23m 55.2sec [calculated begin, UTC on 11/17/05]
>    2.36 second duration [calculated]
>
>Location:
>    MPO: Mike's Place Observatory http://members.cox.net/mrgood
>    Lat = 37.2116N
>    Lon = 80.0786W
>    Elev = 1600'
>Optics:
>    10" f/10 LX200, SBIG ST10XME, AO7 (in path only).
>Temp:
>    40F and falling
>Weather:
>    Clear and windy; seeing variable 2/5 to 3/5 (5 best)
>Moon:
>    98.37% illuminated
>    21d 10m 16s angle between (99) Dike and moon
>
>Plate Scale:
>    Measured 0.878 arc seconds per pixel (8 catalog stars from asteroid
>image)
>    (1x1 binning with f/6.3 reducer through AO7/CFW8 to ST10XME. Clear
>filter).
>
>Started Drift exposure Nov 17, 2005 @ 04h 22m 45sec (using handheld GPS)
>    Switched off telescope at 04h 23m 00sec, watching GPS with hand on
>switch.
>    Estimate 0.1 sec response time here, since I could anticipate off time.
>
>The moon makes it more of a challenge to stretch the image to easily measure
>the gap, which is faint, and is coincident with star due west of target. CCD
>used at 1x1. Drift image has reflections from moon (could not use dew shield
>due to high winds).
>
>Target Star (15 sec exposure):
>    Star  = 84.119, 766.992  (X,Y pixels of centroid)
>    Edge of star = 91, 766  (not used)
>
>    Start of Gap = 864 for X-axis
>    End of Gap =   897 for X-axis
>
>    Width of target trail (y axis) = 770 - 762 = 8 pixels
>    Therefore assume true "start" of trail as X = 84 + 4 (half width) = 88
>
>    24h * 3600sec/hr = 86400 sec/day
>     360deg * 3600sec/deg = 1,296,000 arcsec/day
>       1296000/86400 = 15 arcsec per real sec
>
>Time of start = 864 - 88 = 776pixels * 0.878arcsec/pixel
>            = 681.328 arc seconds
>                 681.328 / cos(Dec=35d)
>             681.328 / 0.819
>           = 826.091 arc seconds (corrected for Dec)
>
>      826.091 / 15 = 55.1 + 0.1second response time
>
>      04h 23m 00s + 55.2 second (corrected for response time)
>        = Occultation started at 04h 23m 55.2sec [calculated]
>
>Delta Gap = 33 pixels.
>         33 pixels * 0.878 = 28.974 arc seconds
>           28.974 / cos(declination)
>            = 28.974 / 0.819
>             = 35.377 arc seconds [corrected for dec]
>
>       35.4 {corrected for Dec) / 15 sec/asec
>          = 2.36 second duration
>
>Its late - did I do the math right? Gotta be at work early tomorrow. Good
>night.
>
>Sincerely,
>Michael R. Good
>