Celestia Forums

Hello,
I've installed volcanopele's Solar System Spice addon using the BSP files specified by volcanopele ( some of them were archived). It works fine. My intent was to see how good Celestia's prediction for the Transit of venus due June 5th & 6th this year would be. The result for both the interior and exterior transits were only about one minute from the published timings. Excellent!

However, the displayed planet orbits are a bit odd. Only Saturn is shown togeter with Pluto if dwarf planets are checked. All other planets don't show. I rememer when Spice orbits were being introduced there was an issue and a "true" command had to be included in the ssc.
I've compared the ssc files of the barycentres and planets and they seem to have an identical structure. I also removed all addons (Cassini etc) that might override Saturn's ssc. Nothing helps.

I've attached an image that illustrates the issue.

I wonder if this has happened before and a explanation exists

Many thanks
David

Apologies all,
I downloaded a wrong BSP file and the scc was calling a file not in the Data folder.

David.

--- edit ---

Hello John,
Thanks for the superbly detailed reply.
I am trying to get my head around the Spice file designation in order to get the current and appropriate bsp files. Is there an idiots guide?

I will get there but my eyesight means that reading is quite laborious so I need more time than ordinary mortals!
(I used the archived bsp files because it was an easy option)
I see that the ssc definition has changed structure and I will try to take this on board.

Thanks for the idea of altering the orbit line colour but how do you specify its length in the ssc definition? I've searched for it but so far no luck. The barycentre orbit would be so much better if it could be set at 1 orbit.

I substituted de423.bsp for de421.bsp. It did give slightly differing times for the transit but I suspect that I need to completely update all to the most recent.

Thanks once again,
David.

--- edit ---

Hello John,
Many thanks for the comprehensive overview. I am reading through the various Spice pdfs and very slowly, am getting a sort of understanding.

I will update the Solar System Spice Kernals and ssc's but that will a later task. I might wait until your next "production".

It does seem a pain having to update the ssc's everytime the Spice kernals are updated. Do you think some code could be added to Celestia to read the bsp files and update the date and times? Please ignore this if it is rubbish.

I am not able to find how to control orbit lengths, is it possible?

Again many thanks for your munifcent help.

David.

--- edit ---

Many thanks John,
Sorry for not replying more quickly but during the last 24 hrs. this forum has been down or a least to me.
I had found the answer to the orbit length and after some trial and error discovered that earth years were the units for planets. With a Visible true and Clickable false definition in the ssc I now have barycentre orbits showing on all planets except Jupiter. I'm trying different options at the moment and in my v. slow way will get Jupiter to show up.

Thanks again,
David