Talk:Coma (optics)

The photo illustrating coma isn't showing coma. The tails on the rain drops are an artifact of the flash duration. Coma looks completely different. — Preceding unsigned comment added by 76.100.0.237 (talk) 00:48, 4 December 2011 (UTC)

.

The coma figure is wrong. The rays from a zone outside the central zone should NOT intersect in the image plane, but in front of (left of) it. That is why the rays from such a zone make a blur circle on the image plane. The blur gets larger as the zone is more outward. That is the whole idea of coma.

The smaller sketch on the right, with the small circles, is correct.

Alex Vermeulen Zoetermeer The Netherlands

Dec. 22, 2008

Comment by 143.129.132.9
COMMENT from READER: I disagree with the drawing illustrating coma. This is incorrect. It should be like here:

http://commons.wikimedia.org/wiki/File:Lens_coma.png

thus creating a "comet-like" blur directed AWAY from the optical axis.

(The explanation is analogue to spherical aberration). —Preceding unsigned comment added by 143.129.132.9 (talk • contribs)

Assistance needed
What is the proper way of listing a patent application as reference so that one can look at the description at an online URL? I was going to use the template from citation templates but it had a number of fields which weren't listed on the reference. See http://www.freepatentsonline.com/4571036.html for details of the description. Trilobitealive (talk) 01:37, 30 November 2010 (UTC)

Removal of Meade Ad
IO was the one who put it up, I wasn't trying to perform linkspan. I was legitimately trying to find information about coma (as part of a search for a new telescope) and I thought a side by side comparasion of a coma and coma free picture would be helpful. In general, I think a link to an ad for short articles is better than no reference. I don't think ads should be removed as spam without a "proper" reference to replace them.

Here is the link I put in, in case anyone wants to check:
 * A side by side comparasion of an ACF and Schmidt-Cassegrain telescope showing Coma

Drxenocide (talk) 17:22, 25 March 2011 (UTC)


 * Sorry if the removal came off as an accusation of linkspaming, not my intention. Consensus is it is not really ok to link ads for many reasons. The specific rational is WP:LINKSTOAVOID #5, "Links to web pages that primarily exist to sell products or services". Fountains of Bryn Mawr (talk) 20:10, 16 April 2011 (UTC)

File:Coma and chromatic aberration.jpg
In my opinion the image File:Coma and chromatic aberration.jpg has absolutely nothing to do with coma. I see no coma in it, a better image is needed. -- Basilicofresco  (msg) 07:32, 5 December 2011 (UTC)

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Diagram of the lens having coma is wrong
The diagram with the lens showing coma is wrong. With coma, an off-axis point is focused on the same image plane by every part of the lens, but on another location on the image plane. What the image now shows is that different parts of the lens focus the off-axis point on different image planes but that is called spherical aberration. Eugene Hecht in his Optics makes this clear. Also take a look at: http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/coma.html Fbrandse (talk) 07:42, 9 September 2023 (UTC)