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Posted by Stephen Durr at 19:38 on 2011 Mar 22
David, I managed the morning display but other duties called me away so I missed the finale which was a shame, but not to worry I am sure there will be other opportunities. Steve
Posted by Callum Potter at 14:56 on 2011 Mar 22
Hi Paul,the player that is now available on that video page will now stream (at least should – you might need to be a little patient as it gets going), so you don’t need to download the file to watch (though that may be easier to do so, at your leisure, offline).Thanks, Callum
Posted by David Arditti at 14:09 on 2011 Mar 22
Yes, there was a huge prominence at 12:08 on Sat 19 March. I missed it, but I saw remains in the afternoon which were still quite big.
Posted by David Arditti at 17:51 on 2011 Mar 21
Nick’s problem will only apply if you regularly GOTO on opposite sides of the mount. If you stick mostly to one side, as I do, adjusting the clock or time displacement so you don’t swap sides, there will be no effect from non-orthogonality of the mount. If you do swap, there will be an effect on pointing accuracy (though many telescopes have major pointing effects from shifting optics/collimation as well). So far as I can see, there will never be an effect on tracking accuracy (what I presume Nick means by "guiding"), provided the mount is correctly polar aligned.David
Posted by Nick Atkinson at 18:41 on 2011 Mar 19
My problem is a slight orthagonal differance from the mount and the telescope. This is detected by picking a star on the meridian and changing the telescope from side to side. This is achieved by adjusting the clock by plus or minus one hour.Any dispacement in RA is a measure of this. I have been intending to shim up the mounting plates but have never got round to this. Once done it should improvove both the pointing accuracy and guiding.Must get this done but I have a 50 -50 chance of chosing the right end!
Posted by Nick Atkinson at 18:28 on 2011 Mar 19
I am opposed to this change. When working in Northern Ireland at the time it was very depressing not seeeing daylight until 10am in the morning. Should the Republic of Ireland continue with GMT in the winter there will be a time barrier on the border. I have similar experiance in Scotland maybe they will continue with GMT too.
Posted by Stephen Durr at 13:21 on 2011 Mar 18
Callum, no problem with the video and thanks for putting it up. Steve
Posted by Callum Potter at 14:24 on 2011 Mar 17
Hi Paul,on YouTube the max video duration is 15mins – so a bit short.in any case – you would be downloading the same number of bytes – just when viewing on Youtube its a bit more gradual… and they are not stored on your machine. I have been looking for a way to view the video ‘live’ on the site, but the things i have tried don’t seem to ‘stream’ the video to you (downloads it all and then shows it) – though perhaps its the way the video is made.Any experts on this sort of stuff out there ?Callum
Posted by Paul A Brierley at 19:03 on 2011 Mar 16
Hi Callum,That’s a big file 250mb.Is there any chance it can be uploaded onto YouTube?
Posted by Stephen Durr at 20:09 on 2011 Mar 14
Very nice images and well done with image of the month. Steve
Posted by Stephen Durr at 19:56 on 2011 Mar 14
Thank you David, I am hoping to do much more with the sun as far as imaging is concerned and also increase my knowledge about our local star. I think the Lunt solar telescope is extremely good value and am looking forward to pushing the double stack to its limit. Steve
Posted by Steve Holmes2 at 16:04 on 2011 Mar 14
Nice work Graham. Calculation trumps logic every time, I fear! I had also done a bit more work on this (manually, not using detailed calculation) and had already found the Nov 2002 and Apr 2041 events. I was only really looking for alignments in the evening sky so I would not have found some of the cases you did anyway.This work showed that the 780day synodic period of Mars was as important as the almost 20yr conjunction period of Jupiter/Saturn. This can be seen in your events in 811, 813 and 815 and other 2yr-apart pairings. I also found I had underestimated the role of Uranus: in a 40yr period it moves quite a lot! I think this is probably what accounts for the large gap between 2041 and 2154: the outer giants are simply not close enough together then to allow the others to fit into the bit of the sky that’s left. The pairs of events a couple of months apart seem to be due to the rapid motion of Mercury, re-appearing to the appropriate side of the sun before Venus has had time to move out of alignment.Your work does show though that my hunch that such alignments are not all that rare seems to be true, particularly if one further restricts oneself to the five major planets. Pity the next one isn’t until 2041 though!As to "morsels" more generally, you might have noticed that I posed an almost exactly similar question myself on the forum some time ago (with no replies at all!!). As I said at the time, I have set up a section of my personal website as a "Theory" section, in which I have placed a number of articles in the style of Jean Meeus’ books. It can be found at http://www.steveholmes.net/astro-theory. Some of the articles are very (very!) long but if you think they might survive the journey to the BAA Computing site then I would be honoured to port them across.
Posted by Graham Relf at 15:07 on 2011 Mar 14
Thanks for your comments Steve. I think they are all quite valid. I have done some analysis myself and written up the result as the start of a new "Morsels" page on the Computing Section site: http://britastro.org/computing/morsels.htmlYou will see that it does not quite answer my original question but a more restricted one: all major planets in the right order.Would you, or anyone, like to contribute further morsels, or ideas for subjects?
Posted by David Arditti at 14:09 on 2011 Mar 14
Good result Stephen. I use more or less the same system. The Sun is certainly worth looking at at the moment.
Posted by Steve Holmes2 at 17:15 on 2011 Mar 13
I suspect alignments of this sort will be more common than one might think, but will definitely come in "seasons".Given the slow motion across the sky of the gas giant planets, it is clear that once the J-S-U-N-(P) order has been established it will persist for many years. Conversely, as Mercury and Venus move very quickly (one circuit of the sky per year, approximately) in this time there will be many occasions for the order Me-V to happen while they are "to the right of" the sun but "to the left of" Jupiter. The only problem child is thus Mars, as its motion is quite fast and so its oppositions, for example, shift by over 45deg per occasion.The problem might thus reduce to what is the maximum angle allowed between Mercury and Neptune/Pluto? More than 180deg and all planets will not be simultaneously visible, but they will still be in order, nonetheless.For example, on page 348 of "More Mathematical Astronomy Morsels" (aka Morsels II), Jean Meeus tabulates the occasions from 1979 to 2020 when all five naked-eye planets are simultaneously visible in the night sky. This shows that in December 2004 and January 2005 they are arranged in order of distance. Further checks with my astronomy programme shows that Uranus, Neptune and Pluto are also in order, and to the west of Saturn. All planets are thus in the correct order. However! There is a very large gap between Saturn and Uranus and so the outer three are not visible at the same time as the inner five, and even in the best case (11th December) by the time you get to Pluto the arc is almost 360deg. Does this count, therefore?[Amazingly, for a couple of hours before midnight on 11th Dec, the moon is between the Sun and Mercury and so every one of the "heavenly bodies" is then in the correct order! This will of course not be visible at all in the UK, however.]While J-S-U-N-P will persist for many years, Jupiter will get more than 180deg in front of Saturn about 10yrs after being close to it. It will then be to the east again after about another 10yrs, but the pair will now both be to the west of the U-N-P grouping. It will be another 20yrs (the Jupiter/Saturn conjunction period) until they both emerge to the east of the U-N-P grouping again (but of course much further east). I would thus expect that there would have been "correct order" groupings 20 or 40yrs before the 2004/5 set – before, because Saturn was already well to the east of Uranus in 2004/5. Anyone care to check?
Posted by Norman Lavender at 07:12 on 2011 Mar 13
Thank you Callum and Andrea.Having re-read the statement in the book it does follow on from a description of the alt-azimuth mount and describes the equatorial mount as an alt-azimuth tipped over. From that point of view it would appear it is indeed talking about measurement from the zenith.However for a novice this is a bit confusing as in most descriptions of polar alignment (i.e. in Norton’s Star Atlas") explicitly refers to the angle relative to the horizontal.
Posted by Andrea Tasselli at 21:58 on 2011 Mar 12
Actually I think that it is relative to the position you measure the angle from. If it is from the zenith then the angle is 90-lat.Andrea T.
Posted by Callum Potter at 21:43 on 2011 Mar 12
Question is (in the book), does it mean relative to horizontal or vertical ?Callum
Posted by Norman Lavender at 19:34 on 2011 Mar 12
I don’t know why my last post got repeated 3 times? I hope it doesn’t happen again.
