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Equipment Discussions >> Reflectors

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JCB
sage
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Reged: 10/04/04

Loc: France
Re: Coma and magnification--a mystery new [Re: jpcannavo]
      #5674414 - 02/11/13 04:43 PM

Quote:

But, this effect - if significant - would actually work in reverse. Just as the keener ear more easily discerns poor fidelity in an audio system, noticing off-axis coma is an exercise in visual acuity. Thus with sharper vision, the off axis coma of the primary mirror would stand out more - not less - relative to a sharp on-axis image. Similarly, with decreasing visual acuity, the same amount of off-axis coma would present a less apparent deviation from the consequently softened on axis image.




Your explanation sounds very logical. However, I've noticed strange things when testing binoculars. The situation is similar: large pupils (4 – 5 mm), with aberrations in the instrument, coma being very common (easy to check by the use of a small monocular behind the eyepiece to magnify the image). I expected that small defects of binoculars would be easily detected with my left eye, because it is slightly better than my right eye. In fact it's the opposite, as if my left eye were more tolerant for small aberrations. My only explanation is that the optical aberrations of my right eye and the aberrations of the instrument are combined to damage the image.

Visual acuity at large pupils is probably a complex function of eye aberrations, density of cones, and properties of the retina.

I should try the same experiment with my telescope, and verify if coma appears differently in my two eyes at low powers.

Jean-Charles


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Starman1
Vendor (EyepiecesEtc.com)
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Reged: 06/24/03

Loc: Los Angeles
Re: Coma and magnification--a mystery new [Re: JCB]
      #5674428 - 02/11/13 04:48 PM

Quote:


I should try the same experiment with my telescope, and verify if coma appears differently in my two eyes at low powers.

Jean-Charles



Good call. I've never done this. It should be an interesting experiment.


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