منبع: سایت کمان آسمانی
From: Alireza Mehrani
To: Prof. Bernard Yallop
CC: Mohammad Odeh
Dear Prof. B. Yallop
Whit greetings from sunny Esfahan!
These are some points about Moon Crescent Observation I gathered during sunset on Tuesday November 5, 2002 in north of Shiraz. The location of observation had the latitude of 30:05 and longitude of 51:06 with the elevation of 2200 meters. The altitude of the mountains in the west horizon was 0.5 degree. I had drowned the visibility line of the crescent with the optic tools on the map of the Iran (with the scale of 1:1000000). My location was 7 km north of this line, and the amount of "q" parameter at this point and at the "best time" was -0.233. The sky in the west horizon was covered with thin and compact layers of clouds. These layers of clouds had made parallel lines with horizon. The sky of the west horizon was totally clear in two parts. One of them was in the altitude of 6 degree and the other in the altitude 3 degree. During the sunset, the crescent was in the upper clear part. But due to the light of the sun it was not observable. It was 22 minutes after the sunset when I observed the crescent it the lower clear part. I was using the 12x70 binoculars. What made me surprised was the fact that despite my presupposition I found this crescent easily; and if the sky was not cloudy, I could observe sooner after the sunset. Moreover, I was confident if I had moved more towards north from the visibility line I had drawn based on your criterion, I would have been able to observe this crescent with the same binoculars or more powerful ones such as 20x120 and 40x150. In Iran, one of my friends in Shiraz too was able to observe the crescent using 20x50 binoculars. However, the amount of "q" for his location was -0.228 which is based on your criterion in visibility location with optic tools. I hope that this report will be useful/applied for you.
Jim Stamm wrote:
Starry Night (planetarium software) shows the crescent to be less than 1 degree altitude at this time and place.
Mohammad Odeh wrote:
Greetings Dear Jim,
Which time and location are you referring to? After 22 minutes of sunset which is 17:37 LT the crescent was 1.7 degrees above the 'ideal horizon' But due to his high altitude, the depression of horizon at 2200 meters above sea level is about 2 degrees, thus the actual altitude of the crescent 22 minutes after sunset was about 3.7 degrees, which is very acceptable.
By the way Br. Alireza in your detailed report at http://www.jas.org.jo/ram23.html you mentioned that your altitude is 52:06, while in the previous email you said it is 51:06. Please which one is correct?
Sorry in the below question I meant to say "Longitude" not "altitude"
Alireza Mehrani wrote:
Please accept my apology. I had an error in my email .The longitude is 52:06. The sunset time behind the mountains of western horizon was17:09 LT. The first observation of the crescent was at 17:31 LT. According to Moon Calculator (ver 6.0) software the altitude of the crescent was 2.353° (Topocentric) at 17:31 LT.
My numbers now agree very closely with Alireza. I believe Starry Night was off because I did not manually input 3.5 hours added to UT for Iran Time Zone. I guess I should state that, "I was off!" My apologies.
No problem dear, and thank you for your concern.
Mohammad Shawkat Odeh.
Jordanian Astronomical Society (JAS).
P.O. Box 141568 Amman 11814 Jordan.
Fax: +1-707-2210918 (In USA).
JAS URL: http://www.jas.org.jo/
JAS WAP: http://www.jas.org.jo/wap/
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