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

已授权您依据自由软件基金会发行的无固定段落及封面封底文字（Invariant Sections, Front-Cover Texts, and Back-Cover Texts）的GNU自由文件许可协议1.2版或任意后续版本的条款，复制、传播和／或修改本文件。该协议的副本请见“GNU Free Documentation License”。http://www.gnu.org/copyleft/fdl.htmlGFDLGNU Free Documentation Licensetruetrue

	本文件采用知识共享署名-相同方式共享 3.0 未本地化版本许可协议授权。
	您可以自由地： 共享 – 复制、发行并传播本作品 修改 – 改编作品 惟须遵守下列条件： 署名 – 您必须对作品进行署名，提供授权条款的链接，并说明是否对原始内容进行了更改。您可以用任何合理的方式来署名，但不得以任何方式表明许可人认可您或您的使用。 相同方式共享 – 如果您再混合、转换或者基于本作品进行创作，您必须以与原先许可协议相同或相兼容的许可协议分发您贡献的作品。
	本许可协议标签作为GFDL许可协议更新的组成部分被添加至本文件。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

许可协议

已授权您依据自由软件基金会发行的无固定段落及封面封底文字（Invariant Sections, Front-Cover Texts, and Back-Cover Texts）的GNU自由文件许可协议1.2版或任意后续版本的条款，复制、传播和／或修改本文件。该协议的副本请见“GNU Free Documentation License”。http://www.gnu.org/copyleft/fdl.htmlGFDLGNU Free Documentation Licensetruetrue

	本文件采用知识共享署名-相同方式共享 3.0 未本地化版本许可协议授权。
	您可以自由地： 共享 – 复制、发行并传播本作品 修改 – 改编作品 惟须遵守下列条件： 署名 – 您必须对作品进行署名，提供授权条款的链接，并说明是否对原始内容进行了更改。您可以用任何合理的方式来署名，但不得以任何方式表明许可人认可您或您的使用。 相同方式共享 – 如果您再混合、转换或者基于本作品进行创作，您必须以与原先许可协议相同或相兼容的许可协议分发您贡献的作品。
	本许可协议标签作为GFDL许可协议更新的组成部分被添加至本文件。http://creativecommons.org/licenses/by-sa/3.0/CC BY-SA 3.0Creative Commons Attribution-Share Alike 3.0truetrue