CCD satellite tracking

From: Greg Roberts (
Date: Thu Feb 21 2002 - 08:12:44 EST

  • Next message: John locker: "Re: CCD satellite tracking"

    This was prepared for another satellite group but since this might
    be of interest to others I am posting it also to SeeSat
    CCD Imaging:
    As some of you know I use a CCD imaging system that is proving fairly
    successful and I would like to encourage others to do something similar
    as it makes observing more comfortable and one can end up with a recording
    of an observing session that one can analyse later.
    There are currently two ccd cameras available that look like they have
    potential - this is the PC164C and the 2006A. The former is available
    for $129 and has a quoted sensitivity of 0.0003 lux and the latter is
    available from
    model 2006X at 69 UK pounds and sensitivity 0.003 lux- see also
    model 2005XA.
    I DONT have either but they appear suitable and are more sensitive
    than my 0.01 lux ccd. (Standard disclaimer -- I dont have any
    connection with this company blah blah blah - except that I cannot say
    I am a satisfied customer since I do not have either ( but Im seriously
    thinking about it!))
    Okay, assuming you are prepared to waste some money, where does one start
    and what does one need?.
    First of all these are video cameras so, as they stand, you cannot capture
    still images (except perhaps as a screen capture) nor do long exposures (
    little use in satellite tracking unless you want a satellite trail).  The
    shutter speed is automatically determined by lighting conditions and you
    normally have no control over such . Depending on where you live in the
    world you either need an NTSC or a PAL version - as far as I can see the
    PC164C is an NTSC version ONLY and the 2006A is a PAL version - make sure
    you get the correct version otherwise you may have problems displaying
    images from such. The version to get will be the same (NTSC or PAL) that
    your television set uses.
    The cameras supplied do NOT come with lenses or a power supply. I suggest
    you get the appropiate 12v DC power supply when you purchase the unit. Do
    NOT buy a lens - these are expensive and have little use in satellite
    tracking. However if you are feeling flush with money then go ahead - at
    least you will be able to make videos of your family etc!
    The units probably have a BNC connector on the back for your video output
    and a socket for the 12v power supply- sometimes these are both in the same
    cable -ie one connection and the cable carries both video and +12v DC. You
    can have a fairly long run of co-axial cable - in my case my CCD camera came
    with a 30 metre length - anyway please make sure you get the correct cable
    and power supply when ordering the particular camera.
    How does one display the image coming out of the coax cable ?  If you have a
    VHS video recorder this is the easiest way-
    plug the video coax cable into the video input of your recorder. (You may
    have to switch your recorder into AV mode) . All being well, with the video
    recorder switched on, you can record the video signal and at the same time
    view the image on your TV set - assuming you have connected your video
    recorder so you can watch videos on your TV set. This is probably the
    cheapest way to do it - if you have a video recorder that is!
    Alternatively you need a composite video monitor - if you played around with
    the early Apple and TRS80 computers (and probably others BBC ? /Atom/ZX81)
    you will have this lying around somewhere. Mine come from a closed circuit
    TV system used in a local bank where they had a security monitoring system
    installed.  Buying these monitors new is quite expensive but you should be
    able to pick up one quite cheaply in a second hand computer shop/flea market
    etc -  again make sure that the monitor is video composite and either NTSC
    or PAL and working  ( as you need).
    Another alternative exists and that is to buy a TV card for your computer -
    these normally have a composite video input socket and it allows you to view
    the image on your computer monitor. It is however not very practical to
    store the video data on your pc as the files will be ENORMOUS.  I record
    onto a video recoder - the standard domestic VHS recorder - and then play
    the tape back into my TV card in the computer. The TV cards are quite
    cheap - you dont need anything very fancy-just make sure you have a
    composite video input socket. Try and avoid a USB card as this only adds
    unneccesary expense.
    The only other thing you need is a lens. These I buy second hand from used
    camera dealers or shops that buy someone elses junk cheaply and sells to you
    at a reasonable (sometimes!) profit. Such lenses are remarkably cheap since
    invariably they are obsolete ( in terms of current cameras) and have odd
    connections to a camera - eg you cannot fix a Leica lens onto a Minolta
    camera body. In our case we dont have to bother - we will probably have to
    devise our own way to attach the lens to the ccd body so normally can ignore
    the connection mechanism.
    For satellite use we are looking at getting a fairly decent magnitude and at
    the same time getting a reasonable field of view.
    This limits us somewhat as its difficult to get a 3 degree field on a
    reasonable sized aperture, so look at getting a lens with a focal length of
    around 70 to 105 mm - I use a 25mm focal length lens on my wide angle ccd -
    field about 10 degrees, and a 70 mm on my narrow field ccd - field about 3.5
    degrees.  Go for as fast an f/ratio as possible.... unfortunately its
    difficult to get a 70mm lens at f/1.2  and a typical 105mm lens is only
    f/3.5. The f/ratio controls how bright the image is, and thus how faint you
    can see so if you had to choose between a f/1.8 lens and an f/2.8 lens of
    the same focal length then go for the f/1.8.
    Remember f/ratio controls brightness of image and how faint you can "see"
    and focal length controls your field of view.
    There is no need to have a fancy tracking system like CoSaTrak - all you
    need is a crude alt/azimuth mount that can point accurately to about 1
    degree and you point it at the appropiate region of sky . Make sure the lens
    is focused properly - focus is extremely sharp since we are working with
    fast lenses at short focal lengths - it should focus on infinity-assuming
    you have been able to get the lens to focus properly onto the ccd chip with
    your homemade lens/ccd body attachment. Plug the video signal cable into
    your recoder/video monitor/computer and sit down in comfort in a warm room
    and watch the screen.
    You should see stars - adjust the monitor controls to MAXIMUM contrast and
    your BRIGHTNESS control to give a background that is grey -- ie you can
    actually see the speckles of the ccd electron noise. If you turn the monitor
    brightness down to show the stars as white dots on a black background then
    you will miss the fainter satellites, so turn up your BRIGHTNESS so the
    background noise is clearly visible.
    You should now be able to see satellites cross the field. If you want to go
    further then things get a little more complicated since you need accurate
    time somehow - I have a homemade time display unit which displays the time
    on the screen so its also recorded on video tape. If you video record the
    video coming in then you have to devise a way to identify the star field and
    make satellite measurements - that could be the subject of another "HOW
    TO..." if anybody wants it. The purpose of this HOW TO is just to be able to
    see satellites.
    Finally what sort of magnitudes can one hope to see-- I live virtually in
    the middle of Cape Town so I have terribly bright skies - so much so I
    considered it a waste of time trying to see satellites naked eye - the naked
    eye limit being usually around +3.5 and maybe +4.5 on a good night-
    depending in which direction I look. With my 0.01 lux camera I can see stars
    down to about magnitude +8.5, and satellites down to about +7.8.  At a rough
    guess I would say the 0.003 lux camera will get you about a magnitude
    fainter, and the 0.0003 lux camera even more - its difficult to give more
    accurate figures . If you have darker skies you should see even fainter - I
    think I am safe in saying that whatever magnitude you can see in 7x50
    binoculars you will see with these CCD sensitivities.
    For those that use a fixed telescope/binoculars for observing you could
    attach the ccd camera onto the binoculars/telescope (similar to a "finder")
    and have a video recorder running all the time whilst you observe visually
    - you will then have a record of what you looked at and in many cases will
    have the satellite image to look at afterwards and confirm your
    Just make sure you use a long enough video tape.. eg a 240 minute tape if
    observing for more than 3 hours . I dont recommend using the slow speed mode
    on a video recorder - the image quality is bad enough without making it
    I think I have covered all the main points - if anyone has questions Ill be
    pleased to answer if possible.
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