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(meteorobs) Re: orange Iridium



Thinking about the following Iridium question and answer some more,

>>Iridiums... I have yet to see an "orange" one. Is this
>>effect common? What would sun angle have to do with the coloration? The
>>light gets to the Iridium without passing through the atmosphere, and the
>>reflected light comes to the observer generally well above the horizon. Am I
>>missing something here?
>
>=============================
>
>Yes, you are missing something here.  At that time of day sunlight was
>indeed passing through the atmosphere before striking the satellite, then
>passing back through a tremendous amount of atmosphere to get to me.  Time
>and location . . .
>
>J.


combined with the observed circumstances,

>1999 October 28
>0534 hrs MDT
>Limiting Magnitude:  4.2
>
>Point meteor seen at approximately 30d above horizon and bearing about
>358d.
>
>Flare reached a maximum magnitude of about -3.7
>
>Color of flare:  white
>
>...  Meteor was definitely a point, no discernable
>movement up or down could be seen.  Immediately following the final 
>flare a
>dull orange object was seen to travel downward.  The initial magnitude 
>of
>the object I would guess at about +3.5.  The object faded rapidly, being
>visible for no more than 0.5s from my location.


the satellite (in a relatively high orbit)  would have to be located near
the earth's shadow  in order to be colored orange by light traveling through
the atmosphere first.  This one was located almost due north, and the shadow
would have been in the west at that hour.  The flare is labeled as white ;
only the fading satellite was called "orange."  I don't know why that would
happen.  None of my Iridium fadeouts have been orange.  Something at 30
degrees elevation I would not call shining through a "tremendous amount"  of
air.  (The location given is very close to Polaris -- I am assuming that is
accurate.)   Below 10 degrees I would say that.  All Iridiums I have seen
showed obvious motion also.  I haven't seen any fainter than +2m at the
peak, but they must be around to much fainter magnitudes -- distance from
the "center line" is all that determines the magnitude.  Once you get a
little experience with meteors you won't have any trouble telling the
difference between meteors and Iridiums.

Norman

Norman W. McLeod III
Staff Advisor
American Meteor Society

Fort Myers, Florida
nmcleod@peganet.com

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