Posts by ajtribick

by ajtribick
17.02.2020, 20:56
Forum: Add-on releases
Topic: Updated stars.dat including Gaia DR2 data (update 2020-02-15)
Replies: 24
Views: 643

Re: Updated stars.dat including Gaia DR2 data (update 2020-02-15)

In your database has all HIP/TYC stars? Unfortunately not. The main reason for this are that the cross-matches to Gaia DR2 are incomplete. In the case of HIP2 stars I can fall back to XHIP for distance information but this is not possible for TYC2. There are also some stars in Gaia DR2 that do not ...
by ajtribick
16.02.2020, 20:48
Forum: Add-on releases
Topic: Updated stars.dat including Gaia DR2 data (update 2020-02-15)
Replies: 24
Views: 643

Re: Updated stars.dat including Gaia DR2 data (update 2020-02-15)

I saw differences between GrantHutchinson's catalog (found on celestiamotherlode : http://celestiamotherlode.net/catalog/show_addon_details.php?addon_id=1114) and gaia catalog ! This is expected. That catalogue (originally by Pascal Hartmann, converted to Celestia 1.4.0 format by Grant Hutchison) i...
by ajtribick
15.02.2020, 18:19
Forum: Add-on releases
Topic: Updated stars.dat including Gaia DR2 data (update 2020-02-15)
Replies: 24
Views: 643

Re: Updated stars.dat including Gaia DR2 data (update 2020-02-15)

Good to know it works on 32-bit! One way of finding out how many stars there are in a stars.dat file is to take the file size in bytes, subtract 14 (to account for the file header, which incidentally also contains the number of stars) then divide by 20.
by ajtribick
15.02.2020, 12:19
Forum: Add-on releases
Topic: Updated stars.dat including Gaia DR2 data (update 2020-02-15)
Replies: 24
Views: 643

Re: Updated stars.dat including Gaia DR2 data (update 2020-02-15)

Fixed an issue with duplicate stars which resulted from not accounting for duplicate entries in the SAO cross match. The v0.1.2-alpha release is linked in the first post of the thread.
by ajtribick
16.01.2020, 07:02
Forum: Add-on releases
Topic: Updated stars.dat including Gaia DR2 data (update 2020-02-15)
Replies: 24
Views: 643

Re: Updated stars.dat including Gaia DR2 data (update 2020-02-15)

Janus wrote:However, small issue.

They require a gaia account to do the queries.
Something you should warn people about.
Indeed, that's why it's the second bullet point in the Prerequisites section of the README.md that's displayed on the main page of the repository on GitHub.
by ajtribick
12.01.2020, 19:30
Forum: Add-on releases
Topic: Updated stars.dat including Gaia DR2 data (update 2020-02-15)
Replies: 24
Views: 643

Re: Updated stars.dat including Gaia DR2 data (update 2020-02-15)

A quick question. Does the Gaia data include stellar motion? If so, how hard is it to calculate XYZ movement from it? I know this limits the time the movement is valid for, but I can live with a few million years, it will do. Gaia DR2 does contain proper motions and radial velocities. This informat...
by ajtribick
12.01.2020, 17:34
Forum: Add-on releases
Topic: Updated stars.dat including Gaia DR2 data (update 2020-02-15)
Replies: 24
Views: 643

Re: Updated stars.dat including Gaia DR2 data (update 2020-02-15)

Good point, I renamed the zip file.

an improvement over the perl script used to make the original DB.
Well, I do like to believe I've gotten a little better at coding over the last decade or so...
by ajtribick
12.01.2020, 13:45
Forum: Add-on releases
Topic: Updated stars.dat including Gaia DR2 data (update 2020-02-15)
Replies: 24
Views: 643

Updated stars.dat including Gaia DR2 data (update 2020-02-15)

Since I wasn't able to post this on the Celestial Matters forum (possibly a glitch in their website), I thought I'd also post it here. Here are the Python scripts for generating a stars.dat from the Gaia DR2 data, using the subset of stars cross-matched to HIP2 and TYC2. XHIP is used to fill in the ...
by ajtribick
27.02.2017, 18:38
Forum: Physics and Astronomy
Topic: TRAPPIST-1 system: 7 Earth-sized planets
Replies: 37
Views: 7796

Re: TRAPPIST-1 system: 7 Earth-sized planets

I agree it is somewhat difficult to get the orbital elements right, particularly when most of the cases you are likely to come across are wrong. Nevertheless I do find it slightly surprising that almost no-one seems to check whether the transiting planets in their add-ons actually transit the star f...
by ajtribick
25.02.2017, 11:41
Forum: Physics and Astronomy
Topic: TRAPPIST-1 system: 7 Earth-sized planets
Replies: 37
Views: 7796

Re: TRAPPIST-1 system: 7 Earth-sized planets

Posting here because I see this mistake being made time and time again. Celestia interprets orbital elements as being with respect to the ecliptic plane, while sources typically give them with respect to the sky plane tangent to the star. Plugging the numbers straight into the ssc without doing the ...
by ajtribick
22.07.2012, 16:42
Forum: Bugs
Topic: Binary orbits incompatible with radial velocities
Replies: 58
Views: 23523

Re: Binary orbits incompatible with radial velocities

Do what you want. I'm out.

I really don't see much point in creating bad feelings by messing with people's pet code. I've got other things to be spending my free time on.

Enjoy the summer.
by ajtribick
22.07.2012, 14:51
Forum: Bugs
Topic: Binary orbits incompatible with radial velocities
Replies: 58
Views: 23523

Re: Binary orbits incompatible with radial velocities

Fridger, You have had ample opportunity in this time to present a fix for this issue that you would be happy with. Instead you choose to keep insulting me, denying you made any mistake whatsoever, assumed bad faith on my part when I presented the fix the first time (yes I got the credits wrong, but ...
by ajtribick
22.07.2012, 09:53
Forum: Bugs
Topic: Binary orbits incompatible with radial velocities
Replies: 58
Views: 23523

Re: Binary orbits incompatible with radial velocities

I thought this point has finally been clarified! Obviously NOT. As I pointed out earlier, the RV data and the RV theoretical prediction do each depend on a z-axis sign convention . Here is the reminder: http://www.celestiaproject.net/forum/viewtopic.php?f=3&t=15994&start=43 Either sign conv...
by ajtribick
22.07.2012, 06:58
Forum: Bugs
Topic: Binary orbits incompatible with radial velocities
Replies: 58
Views: 23523

Re: Binary orbits incompatible with radial velocities

:roll: I insist that there was nothing INCORRECT in the coordinate system that I used. This sentence should be reformulated properly. The coordinate system I used simply did not match the sign convention (z-axis) corresponding to the radial velocity data that you included later. Well somehow your &q...
by ajtribick
21.07.2012, 18:13
Forum: Bugs
Topic: Brown dwarf oddness
Replies: 10
Views: 4569

Re: Brown dwarf oddness

Have to allow stars to reflect light first...
by ajtribick
21.07.2012, 12:59
Forum: Bugs
Topic: Brown dwarf oddness
Replies: 10
Views: 4569

Re: Brown dwarf oddness

Yes confirmed that the transition happens at T6/T7 for standard spectral types (without modification of temperature). On the other hand the properties of this brown dwarf are highly implausible! If you don't force the radius to be 0.87 times solar, the absolute magnitude you have assigned causes Cel...
by ajtribick
21.07.2012, 10:40
Forum: Bugs
Topic: Binary orbits incompatible with radial velocities
Replies: 58
Views: 23523

Re: Binary orbits incompatible with radial velocities

A further update on this fix. Rewritten version of spectbins.stc to fix the coordinate system, and the following issues: ⋅ Used quaternion multiplication for transformations, this is easier to understand than the original calculation. ⋅ Removed the dependency on non-public, undoc...
by ajtribick
18.07.2012, 22:33
Forum: Bugs
Topic: Sun's visible diameter
Replies: 4
Views: 3062

Re: Sun's visible diameter

This is a side-effect of trying to represent the huge range of lighting on a computer monitor with limited dynamic range. There's no particularly good resolution to this without rewriting the render engine to handle HDR properly.
by ajtribick
18.07.2012, 22:30
Forum: Bugs
Topic: Brown dwarf oddness
Replies: 10
Views: 4569

Re: Brown dwarf oddness

I think this may have something to do with the disappearance of the glowing halo at temperatures <1000 K (based on experimentation, I'm not sure where in the code this is defined) From the source code (star.cpp), the temperatures for T-type objects are defined as follows: static float tempT[10] = { ...

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