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Posts Made By: Dan D DuBal

July 17, 2002 07:48 PM Forum: Deep Sky Observing

Re: Milky Way from my backyard!

Posted By Dan D DuBal

I know what you mean. It's not uncommon for a suburban nighttime sky to "gain" another ~0.3-to-0.5 magnitude or so around the 2am-3am timeframe. It can occur when some key light sources (perhaps only one or two) in your neighborhood or section of town are extinguished. Fewer lights; darker sky. Some nights it happens; some nights it don't.

I'm sure glad when it does.

Best wishes.
-Dan

July 19, 2002 03:56 PM Forum: Eyepieces

Re: Monocentric anyone?

Posted By Dan D DuBal

I plan on putting together a monocentric eyepiece... *someday* (a few other LONG-overdue projects will take first priority, over the next few months). Perhaps my timing will coincide with the "return" of Jupiter & Saturn.

Steinheil monocentric triplets are available from Edmund in a few focal lengths. They carry Hastings triplets, too.

Once I give it a try, I'll check back and relay my impressions.

The greatest advantage might be in the category of surface scatter. I recall one particular report in which an experienced stargazer, trying a monocentric for the first time, noted less scatter in it than in another "standard" eyepiece.

--I'll try and find the article. It may have been Jay Freeman.

I'll happily deal with a 30-degree apparent field, if the monocentric yields a discernible advantage in image fidelity.

Best wishes.
-Dan

August 14, 2002 08:34 PM Forum: Eyepieces

Siebert 22.5mm Ultra Plus

Posted By Dan D DuBal

(From Ryan A.'s query in "Equipment" forumsmile

This was the first & only 22.5mm U.P. I've seen in the field. They're still quite new & rare.

This is not a review. I'll note impressions of the eyepiece & the view it yielded, but I'm working from memory. No A-B comparing was done. I'm still largely unfamiliar with both the eyepiece & the scope it fed. Keep grains of salt handy :-)

The eyepiece: a 1.25-inch 22.5mm Ultra Plus, Harry's latest design, uses a stainless steel barrel/body & hard slide-fit eyecup sleeve. The sleeve fit snugly around the body (no slop). "Below" the sleeve was a beefy twin o-ring, functioning (I think) as barrel stop &/or sleeve stop (user's choice). Sleeve was snug enough that my own preference would be to use the ring as barrel stop (parfocal with another eyepiece).

Being Edmund-sourced, the lenses' polish & coatings appeared superb.

The views: I think of the 22.5mm U.P. as a 60-degree, long-eye-relief, widefield orthoscopic. The owner's scope is a Nexstar 80GT (*very* fast & designed for wide fields @ moderate magnification). In the 80GT, the 22.5 yields ~18x over a ~3.3-deg. field. Over two nights, it fed on brighter Messier & NGC clusters, nebulae, & galaxies. I peeked at maybe 20ish, including Ms 7, 8, 11, 13, 16, 17, 20, 31, 45, 57, NGC 6992, Double Cluster, & more. At no time was I unimpressed by the U.P. Yes, the combo yielded some off-axis astigmatism (expected). However, the image "sweet spot" was robust, perhaps the central ~70% zone. Tight, hard, stars within; reasonable astigmatism beyond (akin to my Meade SW at ~f/7). No rabid seagulls; o-a astigmatism well controlled, given the f/5 system. I'm astigmatic myself; not sure how much (if any) my eyes contributed to the astigmatism seen.

No vignetting. No black-outs. No kidney beans. Can't comment on lateral color or induced chroma (no benchmarks for comparison).

Nutshell: I like the 22.5mm Ultra Plus & want to see more of it. When I do, I'll pay more attention, make comparisons, & take notes.

Hope this babble wasn't vague or useless. If any specific ??s, let me know.

Best wishes.
-Dan

September 25, 2002 04:44 PM Forum: Binoviewers

Make mine Leica

Posted By Dan D DuBal

Last December, I happened across a current-vintage Leica head & incline prism assembly from a DM series microscope. Since then, I've removed the head from the prism assembly and integrated a 1.25-inch barrel and 1.25-inch eyepiece collars (all of which came from two Celestron prism diagonals). Eventually, I'll refine the base of the Leica and incorporate a short-as-possible bayonet or "dovetail" ring interface. The goal is a modular viewer fed by interchangeable 1.25-inch and 2-inch barrels and a dedicated (no eyepiece collar) 1.25-inch mirror diagonal. For now, the integrated Celeston hardware is fine.

The Leica's dichroic beamsplitter and elliptical Pyrex mirrors yield outstanding image fidelity. Since my primary reasons for "going bino" are related to Luna- and planet-viewing benefits (floaters "reduction" and binocular comfort/ease), I don't mind the head's 22mm aperture.

The Leica sees use in both my MK67 and the Pentax 75, with the 2.5X Powermate serving as intermediary.

My next step is to add a couple more eyepiece pairs. For now, I have a pair of 9mm Meade Series II orthoscopics and a pair of cheap-o ~25mm binocular eyepieces. The cheap-os are uncoated Kellners, I think. In fact, one or more of their elements might actually be plastic (polycarbonate). While they're obviously little more than low-mag (and low-grade) substitutes (while I ponder my 22-25mm options), the Leica's fidelity is so good that the cheap-os actually do a fine job (aside from their prominent ghosts). The Powermate surely helps, too, as does the inherent fidelity of the scopes feeding them.

As I continue to both refine *and use* the viewer, I'll try and make it a point to come back here and share my experiences. And I'll try not to bore everyone. :-)

Best wishes and cheers.
-Dan

November 6, 2002 08:28 AM Forum: Off Topic Discussions

Re: Checking E-Mail...

Posted By Dan D DuBal

Are you surveying, or actually wanting advice?

If you are surveying:
I check email about 3-4 times during the course of a day (evening included).

If you are wanting advice:
"Too often" and "not often enough" are entirely subjective (i.e. dependent on individual needs, tastes, et.al). All I can offer is, "Check email as often/frequently as needed."

Best wishes.
-Dan

December 23, 2002 08:24 PM Forum: Pictures of Me and My Telescope and........

Mak, The Brain, & Brainless

Posted By Dan D DuBal

Weekend Under the Stars, 8/2001, near Fox Park, Wyoming
Elevation ~9100'
Me (aka Brainless) & my Intes MK67 (on Pentax M2)
Bill Becker's MK65 (on Vixen GP) at right
A favorite t-shirt
Elastic "sock" bandage hiding snugly wrapped gauze, surgical tape, & an I.V. insert on back of wrist/forearm

Brain took a couple nights off from trying to take over the world. Must not have agreed with him...

Cheers, grins, and Happy Holidays.
-Dan

January 1, 2003 01:26 AM Forum: Equipment Talk

Re: converting a C90 from .965 to 1.25

Posted By Dan D DuBal

Hi Walt.

The most-popular solution is the "Large Accessory Ring." I know Orion Binocular and Telescope used to sell this adapter (& still may, though it's not listed in their catalog). Scopetronix does indeed carry the LAR. Perhaps a Celestron dealer can help you find one.

A standard 1.25-inch Celestron visual back would then screw onto the LAR.

Scopetronix also sells a visual back which screws directly onto an ETX90/105/125 rear port -- no LAR needed. I believe this adapter fits the C90, as well, but you might double-check with Scopetronix on that point. Perhaps another Astromarteer can confirm this. If it *does* fit the C90, then let me know -- I have a spare and would be happy to send it your way (gratis). What a deal, eh?

I'll keep on eye on this thread.
Best wishes.
-Dan

April 16, 2003 07:37 PM Forum: DVDs and Music and Books That You Recommend

Ramblings

Posted By Dan D DuBal

A Not-Necessarily-Top-10 List...

Movies:
"The Local Hero"
"Dark City"
"Secret World Live" (Peter Gabriel concert vid)
"Cinema Paradiso"
"The Complete SCTV Collection" (if only it existed... SOMEBODY! PLEASE!)

Music:
"Blues Traveler"
"Moondance" - Van Morrison
"Locusts & Wild Honey" - The Blessing
"Freeze Frame" - J. Geils Band
"Vs." - Pearl Jam

July 6, 2003 11:00 PM Forum: Solar System Observing

Huygens Challenge Revisited (pt. 3)

Posted By Dan D DuBal

"Pen Light" & Company:

During these sessions, I also viewed Mars via the Pentax 75 EDHF, noting comparisons with the Explorer’s performance. Again I used the aperture masks, yielding effective ratios of f/10 & f/12.5. I won’t babble too much about how the Pentax fared. As expected, the Pentax was a showoff when not limited by ocular aberrations. Both Huygenians struggled with the faster scope, even in "Pentax 40" & "Pentax 50" modes. The superior correction of the Pentax/Tak combo (~67x) was evident at 40mm (relative to the Explorer/H12.5mm combo). Image fidelity was higher: more sharply defined; better contrast (both low- & high-level) & cleaner hue saturation. The EDHF did very well with its lifetime cohort, the 6mm Abbe (~83x). The level of detail visible through either mask was generally similar to that of the Tasco/Tak combo (~107x). However, the Abbe allowed the Pentax to strut its stuff at full aperture (f/~6.7). Sure, by going full bore with 75mm, I may have digressed from the spirit of Ron B[ee]’s Huygens Challenge, but what the heck; I’ll just call it a benchmark :-). In all aspects, the full-aperture views given by the LE & the Abbe were simply superior, with more detail seen (& more easily so). Tyrrhenum & Syrtis/Iapygia were recognizable, & each hinted at threshold mottling & shades/hues. Of course, at ~67x & 83x, these hints were slight at best. And how about that SR4mm (125x)..? You know what? The little mutant aint half bad, if you feed it premium optics. Full aperture made it struggle a bit, but the details already noted (SPC, Tyrrhenum, Syrtis/Iapygia, yellowish hue) were still there (just not as cleanly rendered). This may have been a function of magnification, but I can’t verify that.

So, what did I learn from the "Huygens Challenge?" What might one glean from such semi-sane & semi-useful experiments with "Jason & the Huygens-nots?" Why would someone in their not-so-right mind spend 10 hours over 3 mornings staring at Mars through 40mm & 50mm apertures? Well, if nothing else, the sessions gave my eye a fine workout. No doubt my observing skill has benefitted greatly from my years of using such small scopes & pushing their limits. Now, I’m more eager to point my relatively monstrous Intes MK67 at Mars & see what’s what.

That brings me to the main reason I launched this crazy "Jason the Explorer" adventure: one word, three letters...
F U N
I mean, THAT’S WHY WE ALL DO THIS... isn’t it?

The Explorer is an entertaining little cyclops, but I’ll be devoting much of my gazing time through September to Mars, & I’m hoping to push the limits of the MK67. I won’t balk at using all tools on hand, too – filters, sketches, binocular viewer, maybe even an apodizing mask. Should be a major kick.

Best wishes & loads of fun.
-Dan

P.S. for Ron B[ee]: Thanks for your spirit & enthusiasm. It sparked some reading & research about Huygens, & I discovered that he & I share the same birthday. Kind’a cool. :-)

July 6, 2003 11:13 PM Forum: Solar System Observing

Hugens Challenge Revisited (pt. 2)

Posted By Dan D DuBal

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!).