Stars and coma aberration

[panovrx]

http://intothenightphoto.blogspot.com.au/2013/02/overcoming-coma-aberration-part-2.html

Nightscapes with stars are a popular genre on Flickr etc and there is a lot of discussion on the best lenses to use. The Samyang rectilinear wide angles are very popular for this and lenses that you think might be good, like the 24mm f1.4 Canon are actually not good at all. I can confirm that this Canon lens is not very good for stars having rented one for a star panorama. (Coma is the problem). A great lens for other low light subjects though.

 Eventually I just used my Canon 8-15mm. (f4 at 30 seconds at 12mm). Misting is a big problem on cold nights.

http://www.mediavr.com/stars/stars.htm

One peculiarity about star photos is that with modern cameras you can easily record lots of stars but the brightest stars, the ones that we recognize as the constellations, get lost in the myriads of stars. Ideally there would be a filter that thins out the faintest stars without dimming the nebulosities.

PeterM

[Sacha Griffin]

That's a lovely shot Peter. Thank you for sharing.

 

Best Regards,

 

Sacha Griffin

Southern Digital Solutions LLC  - Atlanta, Georgia

http://www.seeit360.com <http://www.seeit360.com/>

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From: [hidden email] [mailto:[hidden email]] On
Behalf Of panovrx
Sent: Friday, September 13, 2013 7:37 PM
To: [hidden email]
Subject: [PanoToolsNG] Stars and coma aberration

 

 

http://intothenightphoto.blogspot.com.au/2013/02/overcoming-coma-aberration-
part-2.html

Nightscapes with stars are a popular genre on Flickr etc and there is a lot
of discussion on the best lenses to use. The Samyang rectilinear wide angles
are very popular for this and lenses that you think might be good, like the
24mm f1.4 Canon are actually not good at all. I can confirm that this Canon
lens is not very good for stars having rented one for a star panorama. (Coma
is the problem). A great lens for other low light subjects though.

Eventually I just used my Canon 8-15mm. (f4 at 30 seconds at 12mm). Misting
is a big problem on cold nights.

http://www.mediavr.com/stars/stars.htm

One peculiarity about star photos is that with modern cameras you can easily
record lots of stars but the brightest stars, the ones that we recognize as
the constellations, get lost in the myriads of stars. Ideally there would be
a filter that thins out the faintest stars without dimming the nebulosities.

PeterM

[Zarl]

> Posted by: "Erik Krause" on Mon Sep 16, 2013 10:39 am ((PDT))
>
> Am 14.09.2013 01:36, schrieb panovrx:
>> One peculiarity about star photos is that with modern cameras you can
>> easily record lots of stars but the brightest stars, the ones that we
>> recognize as the constellations, get lost in the myriads of stars.
>> Ideally there would be a filter that thins out the faintest stars
>> without dimming the nebulosities.
>
> Slight defocus can help to see the constellations clearer. This way
> bright stars appear larger while faint ones get invisible. A sharp image
> can be done in a second step to get the faint stars and the terrestrial
> subjects.

This might work in a similar way with a masking technique in Photoshop
(or GIMP). Take your already shot (focused) image of the sky, on a
copied layer apply a Gaussian blur (start with a small value like 0.5)
and after that compress the levels (Cmd+L in Photoshop) for that layer.
Set layer to brighten only.

Carl

[Erik Krause]

Am 17.09.2013 13:06, schrieb Carl von Einem:
>> >Slight defocus can help to see the constellations clearer. This way
>> >bright stars appear larger while faint ones get invisible. A sharp image
>> >can be done in a second step to get the faint stars and the terrestrial
>> >subjects.
> This might work in a similar way with a masking technique in Photoshop
> (or GIMP). Take your already shot (focused) image of the sky, on a
> copied layer apply a Gaussian blur (start with a small value like 0.5)
> and after that compress the levels (Cmd+L in Photoshop) for that layer.
> Set layer to brighten only.

This might have some effect, but not the same like defocus when
shooting. The reason is that bright stars get overexposed soon. Since
they are a single point when focused correctly they get and stay white.
If defocused the light is distributed across several pixels which aren't
overexposed that fast. This way you might even discover, that stars are
actually colored (like I did years ago when shooting the night sky over
altiplano in Peru - one of the regions with least light pollution in the
world BTW).

--
Erik Krause
http://www.erik-krause.de


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