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Posted by Nick Atkinson at 19:06 on 2013 Jun 11
Please advise if any planetarium software will give a plot of an NEO.CheersNick
Posted by Martin Mobberley at 20:04 on 2013 Jun 11
Nick,The basic answer to your question is YES. If you go to: http://www.minorplanetcenter.net/iau/Ephemerides/SoftwareEls.htmlyou will see a list of orbital elements which can be downloaded for use in various popular software packages…. My favourite is Guide (now at version 9.0). Every package has its own way of uploading NEO data, which will be covered in the manual. If all else fails orbital elements can be typed inmanually for a specific object by going to:http://www.minorplanetcenter.net/iau/MPEph/MPEph.htmland entering the object name plus selecting a format for elements output.HOWEVER, planetarium packages become inaccurate if the NEO is passing so close that the Earth’s gravity starts to dominate. In this case using that MPEph web page above is more accurate than a planetarium package if the object is, say, closer than the Earth-Moon distance. It is also important to specify your exact location on Earth as clearly the Earth’s radius of ~4,000 miles can cause a significant shift in apparent position if an object is within a few hundred thousand miles of us!If by ‘plot’ you also mean ‘plot a track’, then certainly Guide 9 can do that too, once the orbital elements are installed. But again, the observer’s location on Earth needs to be accurate and for very close NEOs the track may be inaccurate by a significant amount. For NEOs that are more than, say, half a million miles away the track should be accurate enough for all reasonable telescope slewing purposes…….Martin>Please advise if any planetarium software will give a plot of an NEO. Cheers Nick<
Posted by Nick Atkinson at 19:59 on 2013 Jun 20
Martin,Thank you this. I have sky X and I have now found out how to enter the orbital elements. I did manage to image 1998 QE2 on 2/06/13 but failed on subsequent nights despite having the co-ordinates published by Richard Miles. I suppose because these planetarium packages are not downloading data in real time at best all they can do is plot the path rather than give minute by minute positional data.Nick
Posted by Martin Mobberley at 10:35 on 2013 Jun 21
Nick,>I suppose because these planetarium packages are not downloading data in real time at best all they can do is plot the path rather than give minute by minute positional data.<Downloading data in real time isn’t the issue when it comes to knowing where the NEO is. The first issue is the accuracy of the orbital elements used to calculate the NEO’s position. For brand new NEOs these elements will be very rough, but with more measurements of the NEO’s position, by observers such as Peter Birtwhistle, the orbital elements become far more accurate. Planetarium packages can easily calculate the position for each minute, but when the object is close to the Earth a number of traps lie in wait. If the object is so close that Earth’s gravity starts to play a major role it is better to use the MPC ephemeris position, set for your location on Earth. Planetarium packages work perfectly well until an object is extremely close to the Earth.If geocentric coordinates are used (that is, the observer is assumed to live at the Earth’s core) the object’s position will become increasingly inaccurate as the object closes in….. When CCD fields of view can be aquarter of a degree or smaller this can lead to an object being missed.But downloading data in real time is not the issue, just having accurate orbital elements (these are often updated daily for critical objects), stating your position on Earth accurately and, for the closest NEOs, having software that can cope with an object influenced by Earth’s gravity….for very close NEOs the MPC predictions will be the best.Martin
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