このサイトの「そら」で つかって いる データの 出典と ライセンスです。
（画面の 中の「この 空に ついて」からも たどれます）

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1. 星の 位置・明るさ・色
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Yale Bright Star Catalogue, 5th Revised Ed. (Preliminary Version)
  Hoffleit D., Warren Jr. W.H. (1991)
  Astronomical Data Center (NSSDC/ADC)
  VizieR / CDS カタログ V/50
  https://cdsarc.cds.unistra.fr/viz-bin/cat/V/50

肉眼で 見える 6.5 等までの 8,404 個を 取り出し、赤経・赤緯・V 等級・B-V 色指数・
バイエル符号・星座を 同梱して います。

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2. 星座の 線、星座の 名前、天の川の かたち
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d3-celestial
  https://github.com/ofrohn/d3-celestial

Copyright (c) 2015, Olaf Frohn
All rights reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

3. Neither the name of the copyright holder nor the names of its contributors
   may be used to endorse or promote products derived from this software
   without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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3. しょうぎの きまりの 判定
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tsshogi (MIT License)
  https://github.com/sunfish-shogi/tsshogi

指せる手の 最終判断・千日手・入玉の 判決に つかって います。