Re:Satellite Photography

From: Greg Roberts (
Date: Wed May 20 2009 - 10:09:04 UTC

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    Morning all
    Gerhard addressed the following comments to me:
    >- 640 x 427 pixels could then be the standard to set the camera to ?
    >- .png format the standard ?
    >- for your work will do at max telephoto.
    >- will do stacking for party pictures.
    >- on a alt/az tracker do you not think this
    >will be a excellent gift to the wife? Your opinion will be apreciated or
    >are there simpler stuff on the market ? your opinion please.
    Sorry for the delay in replying - I observed last night till 1am and am now busy
    processing the results.
    I just happened to use 640 x 427 -- all I did was reduce the size of your 
    image of 1600 x 1067 to 640 x "something" and maintaining the aspect ratio ,so 
    ended as 640 x 427 pixels so there is nothing "magic about the numbers used. I 
    a little surprised that it didnt come out 640 x 480 so it looks like your camera
    has its own format size. Anyway , for the present, I would not say its necessary 
    reduce your image size- although it will save you storage space. Scott also has 
    large image format from his CCD camera and 2x bins it which reduces the size by 
    factor of 2 and 4x (?) smaller in file size ( I think:-)).
    Re using PNG - a similar type of answer - PIXY -which was the program I did the
    astrometry on your image, either wants a FIT or a PNG file- it was easy enough 
    convert your image to PNG format. I think PNG is actually superior to a JPEG 
    (in theory) since JPEG uses compression - whether the difference is significant 
    your case I dont know -- I wouldnt think there would really be much difference.
    Yes I would prefer you use a longer focal length-especially for the high 
    Okay on your "party pictures" :-))
    I had at look at the "Acuter All in One camera/spotter and telescope mount". I 
    not seen this before and know ZERO about it. I went to the SKYWATCHER site and 
    didnt give much more info - Ill do a search on the Internet and see if the 
    can be located. It LOOKS useful but thats all I can say at this stage so hang 
    your R3000 a bit longer and tell your wife she will have to wait -- do you think 
    really believe its for your wife ? :-)))  -- I must try that argument on my 
    Scott suggested the "cube" - this also looks nice but I think is quite a lot 
    expensive than the one you mention - I think its around $600 - I have seen it
    advertised here in South Africa.  Again I have NO real knowlegde of it - I seem 
    recall there was some disagreeable "flop" in it but I am open to correction.
    Re dead pixels - there is software available to map these pixels and remove them
    from the image, however I would not bother with this. If we eventually use APEX
    for your reductions APEX takes care of the problem internally so there is no 
    need for
    flat fields, dark frames, dead pixel mapping etc- not even necessary to do any 
    processing at all as APEX does it all .
    Okay back to measuring
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