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Edmund Astroscan meets Orion StarBlast |
In the left corner, telescopic champion for over forty years...my classic Edmund
Astroscan 2001 wide-field telescope which dates from 1977. In the right corner, da' contender...my fresh-from-the-box Orion
StarBlast, which boasts quite a few similarities to the vintage
Astroscan--but some major differences as well. Our contest tonight is intended to decide which of these two stylish instruments is best equipped and capable of traveling the world in search of clear skies and faint fuzzies; which, in other words, will join me as principle observing equipage on my next deployment--stargazing from both shipboard and shoreside sites. And may the best telescope win!
The rules are simple; both telescopes will be tested for image quality (including incidence of coma, a common artefact of short focal-length, wide-field optics), focus across the field of view, and ease of use. Identical eyepieces will be used to view a variety of deep-sky objects in the evening, to include M45 (the Pleiades), M42/3 (Orion's famous nebula), and the Hyades. If skies remain clear in the morning comparisons of Saturn, Jupiter and Mars will be attempted.
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Well, we can easily see who's taller. |
Despite very different mountings, these two telescopes are actually quite similar; the
Astroscan's spherical lower body moves freely on a triangular cast aluminum base while the
StarBlast moves ALT/AZ (Altitude/Azimuth, or side-to-side, up-and-down) on a quasi-Dobsonian wooden mounting. Both 'scopes us single-power (1X) finders; the Edmund offering has a cast-aluminum peep-sight while the more techie Orion instrument has a battery-powered red-dot finder (again, 1X) which works in essentially the same way as the peep-sight. Both are also quite portable; the
Astroscan (at 12 lbs)has a shoulder-strap and the
StarBlast (at 13 lbs) a built-in handle
Optically these two telescopes share very similar designs; the
StarBlast has a 113mm (4.5") parabolic mirror as compared to the
Astroscan's 106mm (4.25") primary, both with focal ratios of F/4.0. This gives the
StarBlast a focal length of 450mm (18") and the
Astroscan an f/l of 425mm (17"). These are
very close numbers; in fact the only significant difference (on paper) between these two optical systems is that the
StarBlast's primary and secondary mirror are fully collimatable--they can be adjusted for better performance.
Astroscan's optics are pre-collimated, which means that the owner doesn't have the option of "tuning up" the 'scope.
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The primary mirror collimation knobs on the StarBlast are visible in this photo. |
Will this make a major difference tonight when I focus both telescopes on the Pleiades and alternate views through their identical eyepieces? I don't know. I have my suspicions and a few expectations,
but I'll keep those quiet until I file my report on tonight's comparisons.
Clear Skies, Folks!