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Home > Classifieds > Astromart Classifieds > CCD Cameras ASTRO > Classified #198664

For Sale: *** "If thy eye offend thee, pluck it out!” ***

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Well, not quite. But if you’ve been trying to focus your 35mm or CCD camera by traditional means, you really are bound for failure.

The reason is very simple:  Your eye automatically compensates for images that are out of focus by up to 3%.  So, even though you think you have attained a pinpoint image through a parfocal eyepiece or viewfinder, this still may not correspond to the proper film-plane or backfocus distance your camera needs. 

You do not need to do a lot to prove this hypothesis: just count the number of times you hit the electric focuser button when you are viewing a planet.  It seems that the image you are seeing is never good enough or stabilized.  This is not due to changes in the optical chain, rather the automatic compensations your eye continually makes to satisfy the brain's interpretation, misinterpretation, and reinterpretation of the image.  Eyes are wonderful technical instruments for normal wide-field viewing, but generally lousy for focusing on specific points.  Some anthropologists believe this is an evolutionary leftover from our hunter-gatherer days.  Instead of time making improvements in our vision, it preferred to make improvements in our brains.  One of those improvements was the ability to easily distinguish patterns.

The only way to achieve proper focus for astrophotography is to bypass the above problem altogether.  And this is exactly what the Series IV ‘Stiletto’ focuser does.  Instead of relying on attaining a pinpoint image for your eye, you are presented with a source of light that has a highly visible pattern running across it.  Seeing changes in the pattern while focusing is very easy and not subject to reinterpretation of the brain or dependent on the acuity of your eyesight. While this is not a "what-you-see-is-what-you-get" approach like other methods, it is a foolproof "what-you-need-is-what-you-get" solution to focusing. 

See for yourself.

Clear Skies!
Richard

 

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