APOD Moon reference tool

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Joined: Sun Dec 05, 2010 12:46 am

APOD Moon reference tool

Post by snesin » Sun Dec 05, 2010 12:59 am


Often when I am looking at a particular APOD, I like to get a feel for how big the field angle is. I have found the best way for me is to compare it to a picture of a full Moon.

I wrote a tool that adds a scaled picture to the background of APOD pages, a watermark photo of the Moon. I am hoping you will take a look. There are instructions and example links here:


I am sure you all fight to keep the pages simple, and I am all for that. The site is beautiful because of that. No scripts, no flashing, except the occasional mouseover image. I think that is great, one of the few islands of sanity on the web.

However, I hope you will consider incorporating this reference tool directly into the pages. It would be simple to do, and I would lend whatever help necessary.

Obviously, not every page would benefit from the reference Moon (terrestrial shots, where the Moon would be too big, etc). But for those that would, it would be great to see it automatically show.

To get the watermark to show automatically, all you would need do is add one line to the page, like so:

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<script defer src="http://foundationdotjs.org/ApodMoon/ApodMoon.js" degrees="2.6"></script>
If you were not keen on it showing automatically, you could tie it to a link in the description, where when you click on something like "spans 4 degrees", the watermark Moon is shown then. To do this, set the auto attribute of the script to false:

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<script defer src="http://foundationdotjs.org/ApodMoon/ApodMoon.js" degrees="2.6" auto="false"></script>
then somewhere in the description you would have a link like:

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... this picture spans <a href="#" onclick="return ApodMoon.show();">2.6 degrees</a> of the sky...
If you wanted other ways to specify the size or display, I would be honored to customize the script however needed to make it as easy as possible for you.

Of course in the end, the files should all be hosted on the APOD server (and will also work in CD form). If the files were put directly into the apod folder the line would be something like:

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<script defer src="ApodMoon.js" degrees="2.6"></script>
There are only five files, the one small script file, and four GIF files. You can download them all and host them wherever you need to:

All should all be kept in the same directory. There are no copyright issues with the script or the pictures. I wrote the entire script, and I have released it unconditionally into the public domain, hoping you will take me up on this. A friend named Ron Waters took the photo I made the watermarks from, and he has released those as well, also hoping something comes of this.

I appreciate your consideration in this matter. I think it would make a low-impact, unintrusive but beneficial addition to your great site.

Thank you for the time and effort you already put in,

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Re: APOD Moon reference tool

Post by rstevenson » Sun Dec 05, 2010 1:49 am

I like it. Thank you for doing this. I too hope that the APOD folk incorporate it.


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Re: APOD Moon reference tool

Post by NoelC » Sun Dec 05, 2010 3:11 am

Great idea.


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Re: APOD Moon reference tool

Post by rlocsin » Mon Dec 06, 2010 11:20 pm

This is a really useful tool! Having a sense of scale is really nice. How do we get this added as an option to APOD?

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Re: APOD Moon reference tool

Post by ddale51 » Wed Mar 16, 2011 5:16 am

I put up a post not long ago about this topic before I realized that this one existed. http://asterisk.apod.com/viewtopic.php?f=28&t=22756

The idea of the moon overlay option is one I highly desire to be incorporated in all celestial APOD photos. At least, dear APOD guys, please indicate in the text of each celestial picture the number of angular degrees encompassed by the photo. Thank you.

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Joined: Wed May 11, 2011 12:08 pm

Picture of the Day

Post by waynehorne » Wed May 11, 2011 12:15 pm

I enjoy the picture of the day'
It would helpful if they could place a distance scale on the picture as a reference.