5 April 2006

I got a request for clarification of my observing report to IOTA from the guy in Japan (I think) who crunches all of the data. Below is my response:

You caught all the inconsittencies in my report that I missed when I transcribed it here. My answers to your questions are inserted below each question.

--- In IOTAoccultations@yahoogroups.com, Mitsuru SOMA wrote:
>
> Dear Charlie Ridgway,
> Thanks for your report of the graze of Celaeno (ZC 536) on
> April 2. The lunar limb profile from your observation is almost
> consistent with the profile from the past observations, and your
> observation is valuable for refining the profile data.
> Concerning your report I have the following questions:
>
> 1. You wrote "Date: 2Apr06 UT, Time: 1115 UT," but I do not
> understand what "1115 UT" means. What does this mean?
> (I understand that the events occurred at around 00h 15m UT)
The time should read 0015 IT as it is noted in the table of events.

> 2. Is it correct to assume that the geodetic datum of your
> coordinates is WGS84?
I know that my GPS is set to WGS84. I have not found any documentation stating what datum is used by the Google Maps API, probably because they source the data from at least four disparate sources, but the general consensus among Google Maps developers is that it is WGS84. The discrepancy between the position determined from Google Maps and that measured by my GPS is 23.6701009 meters. If you look up my location on Google Maps
(http://local.google.com/local?f=q&hl=en&q=St+George, +Staten+Island,+NY&ll=40.645596,-74.074896 &spn=0.000859,0.001655&t=h)
you will see that I was standing in the NW corner of the esplanade near the Staten Island September 11 Memorial (the aerial image predates the construction of the memorial but my corner of the esplanade should be in the center of the map).

> 3. What is the height of your station measured from the mean sea
> level? (Maybe it is close to 0m because your station seems to
> be close to a beach.)
My old GPS did not save the elevation data when it saved the waypoint. I would have to estimate the height at about 1 meter.

> 4. Could you tell me what the optics "TV76" mean and what the
> apertures (units) of the binoculars used are?
The optics used for this data were the Canon 15x50 IS All Weather binocular which has a magnification of 15x and an aperture of 50mm. The otehr binoculars were 22x at 60mm and 20x at 60mm. The TV76 is a 76mm aperture Apo refractor which was used at 48x.

> 5. You reported the event times to the nearest seconds. Is there
> any way to get the event times a little more accurately?
I am listening to the recordings and watching the digital counters on the recorders to get these times. I used tow digital recorders and transcribed the events independantly from each one and the timings are in agreement on all events except one disappearance and reappearance pair where there were off by a second between the two recordings as I am hearing and seeing them. Any assessment under a second would be a pure guess and without any merit.

> 6. The third timing data is given as "00:16:20 UT" but it is
> out of order from the rest. Is it correct to assume that its
> correct time is 00:15:20 UT?
That time should read 00:15:20 UT. And in the graphical representation the marker for 1500 should read 1600.

>
> Thanks, Mitsuru Soma

---

I figured out why I couldn't get sound out of the short wave radio and into the mixer to record the time clicks on one stereo track and my voice on the other. Rocket scientist that I am I was plugging the Line Out wire into the Antenna In jack of the radio rather than into the Headphones jack. I don't know how much difference it made in the actual rediction of the data but I know that I need to get a flashlight and actually read the little symbols next to the jacks the next time I try this. All the cables are labeled so they go into the right jacks, if I can locate them.