For those of you with an interest in C/2017 U1:

I quote from a brand new article in S&T (by Kelly Beatty, Oct 25 2017)
http://www.skyandtelescope.com/astronom ... lar-comet/



Fridger

_________________

here is a link to a bsp file from horizons telnewt service
https://drive.google.com/file/d/0B6ZYAd ... sp=sharing

_________________
"I don't pitch Linux to my friends, I let Microsoft do that for me."
Using OpenSUSE 42.1 & Scientific Linux 6.7

Thanks John for the link to the A_2017_U1.bsp file. Meanwhile I wrote the .ssc file etc for SPICE from scratch and added some comments about where the various parameters came from:
-------------------------------------------------
"A2017 U1" "Sol"
{
Class "asteroid"
Mesh "asteroid.cms" # default
Texture "asteroid.jpg" # default

Orientation [ 90 1 0 0 ]

Radius 0.08 # educated guess
Albedo 0.1 # guess

OrbitFrame { EclipticJ2000 { Center "Sol" }}

Beginning "1900 01 01 00:00:00.000" # from 'brief' Spice utility
Ending "2101 01 01 00:00:00.000" # 'brief *.bsp'

SpiceOrbit
{
Kernel "A_2017_U1.bsp"
Target "3788040" # from 'brief *.bsp' command
Origin "0" # from 'brief -c *.bsp'
Period 0 # from celestia.Sci code to get aperiodic Spice trajectory
BoundingRadius 1 # not too big since used just for culling
}

UniformRotation
{
Period 6 # guess
}
}
-------------------------------------

A few remarks: celestia.Sci and Celestia code expect Period = 0 for an aperiodic (hyperbolic) Spice trajectory. In one of the scholarly papers about A/2017 U1 some arguments are given for a relatively tiny size (0.16 km ) of the asteroid. Accordingly, the BoundingRadius (used for culling only) should be pretty small, too. Practically all other values came from using the 'brief' utility. As you can see, I used the default asteroid.cms and asteroid.jpg for now.

Here is a screenshot to show that things are working fine.

[by all means click on image and then hit F11 (Firefox)]


Important tests I did were checking the various positions found by the official observers between Oct. 19 and Oct. 25. http://www.minorplanetcenter.net/mpec/K17/K17UI3.html
The accuracy is generally quite OK.

Fridger

_________________

links all over the place
added a zip to the cmod ,bsp,and ssc i posted in the spice kernel section
-- the gray colored texture and not the red one

_________________
"I don't pitch Linux to my friends, I let Microsoft do that for me."
Using OpenSUSE 42.1 & Scientific Linux 6.7

https://arxiv.org/abs/1711.03558

The origin of interstellar asteroidal objects like 1I/2017 U1

We find that about 1.3\,Myr ago 1I/2017U1 has passed within a distance of 0.16\,pc from the nearby star TYC4742-1027-1. It seems unlikely that 1I/2017U1 originated from an Oort-cloud around this star, but it simply trespassed on its way through.



https://en.wikipedia.org/wiki/1I/%CA%BBOumuamua

1I/ʻOumuamua = A/2017 U1

https://arxiv.org/abs/1711.04927

APO Time Resolved Color Photometry of Highly-Elongated Interstellar Object 1I/'Oumuamua

Many thanks everybody for contributions and updating incoming info about our interstellar visitor who is now named “1I/2017 U1 ‘Oumuamua.” In Hawaiian, ‘Oumuamua roughly means “first messenger,” and the 1I indicates that it’s the first interstellar object.

There is also an image of this 400m long object that might challenge JohnVV

Quote from: https://www.jpl.nasa.gov/news/news.php?feature=7006
[Click on image for a bigger size]

Artist's concept of interstellar asteroid 1I/2017 U1 ('Oumuamua) as it passed through the solar system after its discovery in October 2017. The aspect ratio of up to 10:1 is unlike that of any object seen in our own solar system. Image credit: European Southern Observatory / M. Kornmesser

So far so good

Fridger

_________________

i have been away for a week , BUT i have been having "fun" on a 6:1 ( i am using 6:1:1.3 )

and still have it look good

_________________
"I don't pitch Linux to my friends, I let Microsoft do that for me."
Using OpenSUSE 42.1 & Scientific Linux 6.7

Great! Curious to see...

Cheers,
Fridger

_________________