摘要

This image shows Alnilam lighting up NGC 1990. The photo was taken by Glen Youman of the website astrophotos.net. As of March 2004, the image is also available at http://astrophotos.net/images/nebula/ngc1990.jpg .

The page http://astrophotos.net/pages/Nebula/NGC%201990.htm lists the following information about the image:

NGC 1990 Orion Foresthill, California December 1998 FS-128G (ag, ST-4) hPJ400, stack of two 45 minute exposures

NGC 1990 surrounds the belt star Epsilon Orionis. This reflection nebula is of such low magnitude as to be invisible in all but the larger scopes. There are two very faint detached reflection nebulae in the lower left of the photo, my star charts do not identify these nebulae.

Copyright information

已授權您依據自由軟體基金會發行的無固定段落、封面文字和封底文字GNU自由文件授權條款1.2版或任意後續版本，對本檔進行複製、傳播和／或修改。該協議的副本列在GNU自由文件授權條款中。http://www.gnu.org/copyleft/fdl.htmlGFDLGNU Free Documentation Licensetruetrue

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	已新增授權條款標題至此檔案，作為GFDL授權更新的一部份。http://creativecommons.org/licenses/by-sa/3.0/CC BY-SA 3.0Creative Commons Attribution-Share Alike 3.0truetrue

The following email confirms that the image is under the GFDL. Email addresses have been modified to prevent spam.

 Date: Wed, 24 Mar 2004 07:17:51 -0800 (PST)
 From: Glen Youman <gyouman at sbcglobal.net>
 To: William T. Mahan <wtm2 at duke.edu>
 Subject: Re: Request to redistribute one of your photos

 Mr. Mahan-
  
 You have my permission to use and redistribute any and all of my web-site
 images under the conditions you have listed in your subject e-mail.
  
 NGC 1990 was a film based image.  I no longer have access to a negative scanner
 but if you need to rescan the image, I will gladly mail the original negative.
 
 "William T. Mahan" <wtm2 at duke.edu> wrote:
 Dear Mr. Youman,
 
 I wanted to let you know that I enjoyed your astronomy photos at
 astrophotos.net. I found it by searching Google for a star I wanted
 images of, while doing research for the free online encyclopedia
 "Wikipedia". I thought that your images (and one in particular) might
 be worthy of inclusion in our growing document.
 
 Wikipedia (http://www.wikipedia.org) is a free encyclopedia that is
 collaboratively edited by volunteers from around the world. Our goal is
 to create a comprehensive knowledge base that is not only available at
 no charge, but is also freely distributed.

 I am specifically seeking your permission to use your photo of NGC 1990
 for an article I am writing about Epsilon Orionis:
 http://www.astrophotos.net/images/nebula/ngc1990.jpg

 I'd like to include your image in this article:
 http://www.wikipedia.org/wiki/Alnilam . (To get a sense of the freedom
 of Wikipedia, you yourself can edit this page without registration,
 right now!)

 We can only use your materials if you are willing to grant permission
 for it to be used under terms of the GNU Free Documentation License.
 This means that although you retain the copyright and authorship of your
 own work, you are granting permission for all others (not just
 Wikipedia) to use, copy, and share your materials freely -- and even
 potentially use them commercially -- so long as they do not try to claim
 the copyright themselves, or try to prevent others from using or copying
 them freely.

 You can read this license in full at:
 http://www.wikipedia.org/wiki/Wikipedia:Text_of_the_GFDL
 (note: To keep things simple, we don't use Invariant Sections,
 Front-Cover Texts, or Back-Cover Texts)

 This license also expressly protects creators "from being considered
 responsible for modifications made by others" while ensuring that
 creators get credit for their work. There is more information on our
 copyright policy at:
 http://www.wikipedia.org/wiki/Wikipedia:Copyrights

 We chose the GNU FDL license because it is the best available tool for
 ensuring that our encyclopedia is and can remain free for all to use,
 and for providing credit to everyone that donates text and images. It
 may or may not be compatible with your goals in creating the materials
 available on your website -- that's for you to choose. Please be assured
 that if permission is not granted, your original materials will *not* be
 used at Wikipedia -- we have a very strict policy against copyright
 violations.

 If you agree, we will credit you for your work in the image's permanent
 Description Page, noting that it is your work and is used with your
 permission, and we will provide a link back to your website.

 Thank you for your time.

 Kindly,
 Wil Mahan

 ---------------------
 Glen Youman
 Penryn, California
 http://www.astrophotos.net/ - Home page
 http://www.penryn-esd.k12.ca.us/ -Penryn School
 http://astro.sci.uop.edu/~sas/ -Stockton Astronomical Society
 http://www.darksky.org - International Darksky Association

授權條款

已授權您依據自由軟體基金會發行的無固定段落、封面文字和封底文字GNU自由文件授權條款1.2版或任意後續版本，對本檔進行複製、傳播和／或修改。該協議的副本列在GNU自由文件授權條款中。http://www.gnu.org/copyleft/fdl.htmlGFDLGNU Free Documentation Licensetruetrue

	此檔案採用共享創意 姓名標示-相同方式分享 3.0 未在地化版本授權條款。
	您可以自由： 分享 – 複製、發佈和傳播本作品 重新修改 – 創作演繹作品 惟需遵照下列條件： 姓名標示 – 您必須指名出正確的製作者，和提供授權條款的連結，以及表示是否有對內容上做出變更。您可以用任何合理的方式來行動，但不得以任何方式表明授權條款是對您許可或是由您所使用。 相同方式分享 – 如果您利用本素材進行再混合、轉換或創作，您必須基於如同原先的相同或兼容的條款，來分布您的貢獻成品。
	已新增授權條款標題至此檔案，作為GFDL授權更新的一部份。http://creativecommons.org/licenses/by-sa/3.0/CC BY-SA 3.0Creative Commons Attribution-Share Alike 3.0truetrue