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FastFourierTransform
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The Gaia Mission

02 Oct 2020 05:32

A-L-E-X wrote:
Source of the post Hi, whats the difference between these and what I downloaded from Phunnie?  I actually tried both his 30 million and 15 million star add-ons and while I found the 30 million add-on workable, there was some graphics flickering from time to time so I switched to the 15 million star add-on which is working fine.

This thread is not about the addon to SE but about what the addon is based on, a.k.a. the Gaia mission. Phunnie could at best base its addon on the available data at the time, which is Gaia DR2. Here we are talking about Gaia DR3, more stars, better astrometry and other things I've explained in the previous post.
 
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The Gaia Mission

07 Oct 2020 13:14

Thanks, this explains the different sizes of the add-ons, as I have them all saved.  The original DR1 5 million star add on was 400 MB, while the DR2 5 million star add on was less than 200 MB.
 
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FastFourierTransform
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The Gaia Mission

08 Oct 2020 04:15

A-L-E-X wrote:
Source of the post Thanks, this explains the different sizes of the add-ons, as I have them all saved.  The original DR1 5 million star add on was 400 MB, while the DR2 5 million star add on was less than 200 MB.

This is not possible. Let me clear some possible misunderstandings (If there are any):
Gaia DR1 (data release number 1) was a catalog of 1.4 billion stars (exactly 1,142,679,769). But the first release lacked enough observations to perform accurate stellar parallaxes by its own (thus distances). Thanks to the "old" Tycho-2 and Hipparcos catalogs we could establish some constraints on the new Gaia DR1 data so for the stars appearing in these catalogs we were able to yield a catalog of parallaxes putting everything into the mix. From the 1.4 billion stars in DR1 we got only 2 million (exactly 2,057,050) in the TGAS (Tycho-Gaia Astrometric Solution), which is the 0.18% of the catalog. Thus, at most Phunnie could have made a 2 million star addon for DR1 (not 5 million).

In Gaia DR2 (the current most recent data release, until December 3) contains 1.7 billion (exactly 1,692,919,135) stars. Now with lots of parallaxes. But Phunnie based its addon not in all of the DR2 parallax measurements but in a secondary catalog created by Bailer-Jones et al which estimated distances using a statistical analysis on the parallaxes. The Bailer-Jones distance estimates include 1.3 billion stars (exactly 1,331,909,727) of the Gaia DR2 (78.7% of the catalog). Phunnie did a wonderful job selecting only the best estimates and that's why the addon is at most of 30 million stars (which is just the 2.25% of what Gaia DR2 yielded in "distance measurements").

Phunnie could have made a larger addon with currently available data since Gaia DR2 is huge! but some artifacts might appear in SpaceEngine (due to large uncertainties and biases for the farthest stars), making the gameplay seem unnatural. And also because SpaceEngine is currently uncapable of handling that many catalogued objects without crashing.

I think you are confusing the first realease of Phunnie's addon for SpaceEngine with other later enhancements he did. These were all based on the real data of Gaia second data release (DR2), not in DR1 or any other. Now we are expecting for December the third data release (DR3), which will contain more stars. But that is probably not going to change the addon since it is limited by SpaceEngine capacity to the point it can't even give you the entire DR2 now. Thus the improvements for SpaceEngine will come in the form of better parallax measurements, and more precise distances (a 20% better estimates in many cases).
 
A-L-E-X
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The Gaia Mission

08 Oct 2020 04:44

FastFourierTransform wrote:
A-L-E-X wrote:
Source of the post Thanks, this explains the different sizes of the add-ons, as I have them all saved.  The original DR1 5 million star add on was 400 MB, while the DR2 5 million star add on was less than 200 MB.

This is not possible. Let me clear some possible misunderstandings (If there are any):
Gaia DR1 (data release number 1) was a catalog of 1.4 billion stars (exactly 1,142,679,769). But the first release lacked enough observations to perform accurate stellar parallaxes by its own (thus distances). Thanks to the "old" Tycho-2 and Hipparcos catalogs we could establish some constraints on the new Gaia DR1 data so for the stars appearing in these catalogs we were able to yield a catalog of parallaxes putting everything into the mix. From the 1.4 billion stars in DR1 we got only 2 million (exactly 2,057,050) in the TGAS (Tycho-Gaia Astrometric Solution), which is the 0.18% of the catalog. Thus, at most Phunnie could have made a 2 million star addon for DR1 (not 5 million).

In Gaia DR2 (the current most recent data release, until December 3) contains 1.7 billion (exactly 1,692,919,135) stars. Now with lots of parallaxes. But Phunnie based its addon not in all of the DR2 parallax measurements but in a secondary catalog created by Bailer-Jones et al which estimated distances using a statistical analysis on the parallaxes. The Bailer-Jones distance estimates include 1.3 billion stars (exactly 1,331,909,727) of the Gaia DR2 (78.7% of the catalog). Phunnie did a wonderful job selecting only the best estimates and that's why the addon is at most of 30 million stars (which is just the 2.25% of what Gaia DR2 yielded in "distance measurements").

Phunnie could have made a larger addon with currently available data since Gaia DR2 is huge! but some artifacts might appear in SpaceEngine (due to large uncertainties and biases for the farthest stars), making the gameplay seem unnatural. And also because SpaceEngine is currently uncapable of handling that many catalogued objects without crashing.

I think you are confusing the first realease of Phunnie's addon for SpaceEngine with other later enhancements he did. These were all based on the real data of Gaia second data release (DR2), not in DR1 or any other. Now we are expecting for December the third data release (DR3), which will contain more stars. But that is probably not going to change the addon since it is limited by SpaceEngine capacity to the point it can't even give you the entire DR2 now. Thus the improvements for SpaceEngine will come in the form of better parallax measurements, and more precise distances (a 20% better estimates in many cases).

Thanks- I wonder how large the files will be?
This is what I was referencing.....
Extreme-5Mstars20LALL.pak  size 406,526  downloaded 12/8/18
vs
5M-1L.pak  size 155,154  downloaded 9/25/20
also, despite the large file size, the earlier file loaded fairly quickly with SE (load time 1 min).
now I use the 14M-14mag.pak file size 395,741 downloaded 9/25/20
That takes about 3 min to load at startup.

I used that 30 million star pak that you referenced for awhile, but it took about 8 min to load and although the program didn't crash for me, the window flickered quite a bit.  It was 30M-15mag.pak  size 794,645  downloaded 8/3/20

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