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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/KJAUPDYLFRB3M45H2GZ4JWW5IOQ7VBDF/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "[email protected]",
    "message_id_hash": "KJAUPDYLFRB3M45H2GZ4JWW5IOQ7VBDF",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/KJAUPDYLFRB3M45H2GZ4JWW5IOQ7VBDF/",
    "sender": {
        "address": "kf6kyi (a) gmail.com",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Mark VandeWettering",
    "subject": "[amsat-bb] On the possibility of imaging AO-40 with earth bound\ttelescopes...",
    "date": "2009-10-15T06:57:40Z",
    "parent": null,
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/QUI3GLR4QF6AQ6PPUINMPD5VRFHFQR66/"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "> Has there been any serious attempt to take a photograph of the damaged\n> bird using ground based optical telescopes while it is in sunlight ?\n\nIt's not going to work.   AO-40 just isn't big enough.   For fun,\nlet's worth through\nsome of the details.\n\n> With modern telescopes such as\n> http://www.refractortelescopes.co.uk/reviews/orion/orion-shorttube-80-a-refractor-telescope/\n> or similiar and a modern digital camera and a known RA/DEC co-ordinate\n> of the satellite at any point in its orbit, it should be possible get\n> a fairly decent picture of what is still up there...\n\n> Note RA / DEC are astronomy co-ordinates which should be able to be\n> calculated from AZ/EL or TLE, but I may not be able to do it myself.\n\n> We don't need to track it, but just to image it in several consecutive\n> frames. From: http://www.emergentspace.com/pubs/AIAA_GNC_2002_AMSAT_A040.pdf\n\nTable 1. Nominal Orbit Parameters for AO-40\nOrbit Parameter Value\nSemimajor Axis (km) 36,245\nPerigee Height (km) 1,042\nApogee Height (km) 58,691\nEccentricity 0.797\nInclination (deg) 6.04\nPeriod (hours) 19.1\n\nLet's look at a couple of potential telescopes.  The short tube\nrefractor that you linked to has an 80 mm (roughly 3 inch) aperature.\nAccording to the Rayleigh criterion, that scope should be able to\nresolve angles as small as about 1.5 arc seconds.    At perigee, the\nresolving power is 1042000 * tan(1.5 arc seconds), or about 7.5 meters\n(or 25 feet).    To increase the resolution by a factor of 2, you need\nto to double the  aperature.   To get resolutions down to 1/2 a foot,\nyou need an aperature 50x larger, or 150 inches.\n\nThis doesn't take into account any effects of atmosphere either.\nit's actually fairly rare to get sub arcsecond resolution from any\nearthbound telescope without using adaptive optics.   This limits the\npracticality of high resolution imaging.\n\nImpressive photos of the space shuttle, ISS and HST have been taken\nusing amateur equipment, but these objects are both closer and an\norder of magnitude larger than AO-40.   While we might be able to\nmeasure spin rate and the like by measuring the brightness curve,\nactual imaging of the satellite isn't likely.\n\n73 Mark K6HX\n",
    "attachments": []
}