پــایــگــــــاه اطــــلاع رســـــانـــی هــــلال مـــــاه

www.Helalemah.ir

امروز : سه شنبه مورخ 5 مرداد 1400 هجری شمسی ، مطابق با 17 ذیحجه 1442 هجری قمری ، مطابق با 27 جولای 2021 میلادی

سئوال دکتر محب الله دورانی از آقاي رستمي و پاسخ ايشان در خصوص رصد هلال رمضان 1432

 
پاسخ آقاي مهندس رستمي به آقاي دكتر مهيب
Dear Dr. Durrani

Very thanks you for your questions on the crescent of Ramadan at the daylight.
 
I saw the crescent only by telescope and it was invisible by naked eye on the 31 July 2001.

I think the crescent was invisible after the 18:15 because the crescent was near of horizon and dust did not allow to seen the crescent again.
 
I tried to seen the crescent at the 18:15 and saw it very hardly. It took about a few minutes to matching of my eyes with the too much light of sky inside the ocular.
 
Of course, I predicted that the crescent invisible at the 18:50 by my triangle model. I determined amount of ir-m parameter of this model by 26 observations of daytime in 2007. I have not published its paper in English yet. Triangle model is:


ir-m=27.13*W 0.139*h-0.493*[dh]
 
That W= the crescent wide, h = altitude of crescent and [dh] = absolute of the relative altitude between the moon and the sun.
 
If the ir-m equal to 10, Then the crescent visible by 10" telescope.
If the ir-m equal to 30, Then the crescent visible by naked eye.
 
I have seen crescents at the daytime more than 10 times.

Best Regards
S.GH.Rostami
مكاتبه ي آقاي دكتر مهيب با آقاي مهندس رستمي
 
السلام عليکم
 Dear brother Rostami,

Jazakumullahu Khairun for the detailed report from your personal observatory!
 
If I may, I would like to request some additional information, if available on your Hilal observation of 31 July 2011 from your personal observatory. I am trying to determine atmospheric extinction near the horizon as compared to at higher Crescent Moon altitudes.
 
You had mentioned:
"First sighting time = 17:05 by 8” Celestron Telescope (NexStar SE model)
"Last sighting time = 18:15
"Sunset = 19:51; Moonset = 20:07"
 
I am presuming that the sighting was ONLY through the Celestron Telescope.
What was the reason that the last sighting was at 18:15 since there was an additional 1 hour 36 minutes before Sunset (19:51)?
Was an unaided eye (without telescope or binoculars) sighting of the Crescent Moon successful on 31 July 2011?
 
Jazakumullahu Khairun.
Mohib.
 

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