Challenge to sharpen biggest galaxy picture...

[galaxylover]

I linked here to the biggest picture of any galaxy taken by the Hubble telescope of Andromeda, M31. It is such an incredible photo, and when I zoom in, I can see each star.


But, as good as the Hubble is, each star is a bit of a blur due to the very long exposure times, and weaknesses of the photo sensors, etc...so the stars appear much larger than they really are. When you look up at night into the sky, you don't see each star as a blob like these, but rather, a pinpoint of tiniest light, sharp with emptiness around it.

So, the challenge is...is it possible to edit this photo to make each star a much smaller point of light, so the stars would appear as they do in reality?

If it's too big of a project, what about editing just a small frame of a zoomed-in image, like the pic above?

http://www.spacetelescope.org/images/heic1502a/

 

[galaxylover]

I would like to be able to print this out onto a very large picture to use as a wallcovering, so that's why I'm interested in reducing the "blobbiness" of the stars.

 

[Tom Mann]

Of course there are ways to turn each separate fuzzy star in such an image into a bright single pixel. Obviously, if NASA wanted to do this, they could have easily done so. However, you might want to give some thought as to why they didn't take this approach. For example, when Hubble was first launched and they quickly discovered that there was an error in the shape of the primary mirror, why did they spend hundreds of hundreds of millions of $$$ to design and fabricate a corrector plate, then send it up in orbit and install it instead of simply shrinking each star to a few pixels in size using software.

Well, there are several reasons. Probably the most important is that shrinking each star to a pixel throws away a lot of the useful information present in the image. For example, in a normal astrophotograph, brighter stars are always surrounded by larger diameter halos than dim stars. Your mind understands this, and because of this, you actually judge the brightness of stars in such images by the size of their halos, even when the central core is completely clipped (blown out) to exactly the same brightness (ie, pure white) for many of the stars. In addition, since the central pixels of bright stars are almost always blown out, there is no color in that area. However, one will usually find the the outer reaches of the halos retain the correct color of the star, ie, more useful information.

The second reason is that the general consensus is that small radius, sharp edged stars are just not aesthetically pleasing.

Instead of shrinking each star dramatically, as you requested, my suggestion would be to make your goal a much more modest size reduction using a program such as StarShrink, a Photoshop plugin.

There is a great video tutorial for it here: http://www.rc-astro.com/resources/StarShrink/tutorial.html . Note that the narrator repeatedly points out that he always leaves stars slightly blurry instead of going for maximum size reduction, and cites the aesthetics of astrophotography and blowing out color information as reasons, exactly as I stated above.

Finally, you essentially requested someone to shrink the image you supplied. It's of such small pixel dimensions that I think the much larger image in the above video tutorial shows the effect much better and in a more visually realistic setting than trying to work on the image you supplied.

HTH,

Tom M

 

[galaxylover]

Thanks for your response, that's exactly what I was looking for. I don't want the stars to be all the way down to 1 pixel, but their current size is equivalent to a bunch of orion nebulae, which isn't realistic. Being able to shrink 100 billion stars at once is a feat in itself, and being able to select the maximum pixel size helps too, since I don't want to shrink something that is actually supposed to be bigger, like the stars in the milky way that are part of the picture. My dream is to make a wall-size print of this.

 

[Tom Mann]

Glad to have helped. Do come back and let us know how the project is going ... maybe even post a pix or two.

Cheers,

Tom M