Re: Geosat Solar Transit?

From: satcom (john@satcom.freeserve.co.uk)
Date: Sun Mar 05 2006 - 04:34:17 EST

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    Tried to figure this out a couple of years ago Jeff.....and came to the same 
    conclusion as Tony.
    The objects would be too small to resolve.
    
    I have manged to see transits of leo craft down to 2 arcseconds with an 8 
    inch scope , but  0.25 arcseconds  , even with a much larger aperture would 
    be near impossible....the target being lost in the "noise".
    
    I did wonder at one stage if it might just be feasible using a large 
    telescope and a projection of the Sun's disk onto a large screen.
    
    However , just for fun , and as here in Europe we have the  seven bird Astra 
    fleet to look at , back in 2003 I did a composite of what such an image 
    might look like....mainly to see how much of the disk the co-located birds 
    would cover.
    
    The result can be seen here.....
    
    http://www.satcom.freeserve.co.uk/astrasunout.jpg
    
    
    Regards,
    
    John
    
    
    ----- Original Message ----- 
    From: "Tony Beresford" <dberesford@adam.com.au>
    To: "Jeff Umbarger" <jumbarger2000@yahoo.com>; <seesat-l@satobs.org>
    Sent: Sunday, March 05, 2006 6:08 AM
    Subject: Re: Geosat Solar Transit?
    
    
    > At 14:21 5/03/06, Jeff Umbarger wrote:
    >>Hey All,
    >>     With the declination of the sun between -10 and 0
    >>degrees declination for the next few weeks, would this
    >>not mean that if we were monitoring the disk of the
    >>sun, we would see geosats transiting the sun for the
    >>northern hemisphere? At my latitude (+33.0 deg) the
    >>geosats appear at around -5.25 deg declination and
    >>that is where the sun will be next Tuesday. Has anyone
    >>ever seen this before? That is, is worth watching for?
    > Jeff,
    > The problem is the extremely angular size of even the
    > largest geosat solar panel span.
    > A back of the envelope calculation says a 30meter span
    > at 36 megameters is about a 1/4 arcsecond.
    > so we are talking about a 20 inch telescope
    > to resolve it theoretically. However the killer is the
    > irradiance from the photosphere which will fill in
    > any dark patch of airy disk size , let alone something
    > much smaller.
    >
    > Tony Beresford
    >
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