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Hugens Challenge Revisited (pt. 2)

Started by DrThud, 07/06/2003 11:13PM
Posted 07/06/2003 11:13PM Opening Post
Jason & Family:

First: the H20mm eyepiece (40x) yielded minimal Martian detail, even with the glare-reducing 40mm mask. Still, the planet’s gibbous profile & yellowish hue were obvious, & I discerned the SPC as a definite albeit dimensionless white contrast feature. Tyrrhenum was even subtler. The view at full aperture showed less-than-good fidelity. While f/13 sounds long, it’s still quite short for any Huygenian, & it showed: contrast & sharpness suffered, even on axis.

The 18mm Kellner allowed for slightly easier & better views at both 40- & 50mm, with the SPC’s circumpolar "melt line" peeking into view as little more than a subtle sub-polar band – a low-contrast smear, not obviously tied to the SPC. While full-aperture views with the Kellner were better than with the H20mm, I saw no additional detail, due to irradiation/glare. (Strange to think a 60mm scope can show Mars as "too bright!")

Please note: views at 40-44x were indeed miniscule. At those mags, Mars’s apparent diameter is ~12-13’ (tad more than 1/3 Luna’s apparent naked-eye diameter). One learns to "see small" when using junior scopes in the 500-800mm range.

Moving up to 64x with the H12.5mm made a big difference at both 40 & 50mm. Gibbous profile was better defined, & Mars seemed a tad more yellow-pink. The SPC was resolved (though still merely a “spot”), with the melt line slightly improved (both contrast & aspect). The slanted/diagonal aspect of Tyrrhenum (relative to Mars’s polar axis) was obvious. Tyrrhenum also appeared broader than the melt line, but both dusky features seemed little more than dim & subtle brushstrokes. Later on, Syrtis Major & Iapygia began to revolve into view, & I was able to discern their big patch as its own entity – distinct & well separated from (& darker than) Tyrrhenum. Again, I felt the smaller masks @ f/16 & f/20 were better suited to the H12.5mm & showed more than did the Explorer’s full 60mm aperture.

Jason & the Non-stocks:

The Tak 7.5mm offered ~107x - a big jump in magnification. It's correction also allowed full-aperture views with good off-axis fidelity – far better than provided by the Huygenians at the Explorer’s inherent f/13 ratio. The polar cap showed elongation, & the melt line was both better defined & more obviously “tied to” the cap. Almost all aspects of Mars’s visual appearance were improved via the Tak LE (over the H12.5mm), save one exception: gross contrast between the dusky mare & the lighter-hued plains. This was simply a function of magnification.

The Pentax Abbe (~133x) magnified the view further but yielded no additional detail (nor any improvement thereof). High-level contrast appeared similar as with the Tak LE.

Finally, the SR4mm. I didn’t expect much at 200x, & those expectations were indeed met :-). Contrast suffered, & the mare faded nearly to invisibility. However, the SPC was still visible at all three apertures (>133x per inch @ 40mm!).