Happy Solstice and DU Mini Tutorial

Hello and Happy Winter Solstice to all


For those that think it was yesterday, they are wrong. It is always around the 21st not always on it. This year the winter solstice is on the 22nd December !


This can be demonstrated by a mini tutorial which will also work on the 68k 1.03 version of DU so no one need feel left out.


Run DU and set the time to "2007:12/22 08:00:00.0", the exact time deos not matter but use this anyway. It is best to set this in the "Universal Time" box then everyone will get the same results.

Set up the following in the Report Window.

Column 1:
Date/Time
Universal Time

Column 2:
Topocentric RA/Dec
Sun


You can use Apparent RA/Dec but topocentric will be the same regardless of location. *

* Note: the above is the wrong way round. I have left it as is but correct it here so Lemen's mail still makes sense


Set Advance By to 30 and the time step to minutes and do 10 steps.

Print, View or Save the Report.

The solstice occurs when the sun reaches its most southerly point in the sky, so you are looking for the lowest value of Declination.

As can be seen it bottoms out at -23:26:23.3 at 10:30ish today.


I hope this little tutorial will be of interest to recent DU users still wondering what to do with it


And finally I have not forgotten our antipodean friends, to whom I wish a Happy Summer Solstice !



Bill.


Universal Time | Sun
Date Time | Topocentric RA/Dec
-----------------------+-----------------------
2007/12/22 08:00:00.0|18h00m19.5s -23?26'22.8
2007/12/22 08:30:00.0|18h00m25.0s -23?26'23.0
2007/12/22 09:00:00.0|18h00m30.5s -23?26'23.1
2007/12/22 09:30:00.0|18h00m36.0s -23?26'23.2
2007/12/22 10:00:00.0|18h00m41.5s -23?26'23.3 <==
2007/12/22 10:30:00.0|18h00m47.0s -23?26'23.3 <==
2007/12/22 11:00:00.0|18h00m52.5s -23?26'23.3 <==
2007/12/22 11:30:00.0|18h00m58.0s -23?26'23.2
2007/12/22 12:00:00.0|18h01m03.6s -23?26'23.1
2007/12/22 12:30:00.0|18h01m09.1s -23?26'23.0

@BillE

Nice.

Here are my results;

Universal Time | Sun
Date Time | Topocentric RA/Dec
-----------------------+-----------------------
2007/12/22 08:00:00.0|18h00m19.5s -23?26'22.3
2007/12/22 08:30:00.0|18h00m25.0s -23?26'22.5
2007/12/22 09:00:00.0|18h00m30.6s -23?26'22.6
2007/12/22 09:30:00.0|18h00m36.1s -23?26'22.8
2007/12/22 10:00:00.0|18h00m41.6s -23?26'22.9
2007/12/22 10:30:00.0|18h00m47.1s -23?26'22.9
2007/12/22 11:00:00.0|18h00m52.6s -23?26'23.0
2007/12/22 11:30:00.0|18h00m58.1s -23?26'22.9
2007/12/22 12:00:00.0|18h01m03.6s -23?26'22.8
2007/12/22 12:30:00.0|18h01m09.1s -23?26'22.7


I assume the slight difference is due to location?
I'm at 50:17:01N 05:12:07W.

Lee.

@Lemen

Quote:

It is exactly due to that. In fact you noticed my deliberate typo above [cough].

The topocentric RA and Dec are indeed dependant on the location of the observer. It is the geocentric RA and Dec which should be the same for everyone.

In fact in the next update I will rename the line in the Reports from Apparent to Geocentric to clear things up a bit, if it confuses the co-author of the program I guess everyone else will be even more confused




Bill.

@BillE

Happy Solstice !
I clean forgot about it saturday - but I did get a look at the moon low in the sky yesterday around sunset.

For interest - I was playing around in DU the other day, with the automated advance option in Time Contol - anyroad, the upshot of this was the discovery that there is an event happening ! for those (like me) who dont keep abreast of events as often as they'd like, there will be a Lunar Eclipse on the night of the 21/2/2008 - around 3 am !

... what would be neat is if DU could be made to simulate the moon passing through the Earth's umbra and penumbra.

@agafaster

Quote:

I take it you mean more than just enabling the display of the Earth's shadow, as you must have that enabled to realise there would be a lunar eclipse if you did not know of it beforehand.

If you mean the shadow making the moon plot darker and eventually reddish, then this is plannned for v2.5. The Mac version does it so I should be able to get the Amiga version to do the same.


Bill.

@BillE

Quote:

the second one ! I did wonder what those concentric circles were, but a bit of fiddling, and the realisation that they were nearby when Mars was at opposition t'other day helped !
I reckon a neat bit of shading and colouring can be done in the umbra to get a blood red moon. I'll look forward to it however it comes though !