本帖最后由 xiongyulei 于 2009-10-6 14:14 编辑
嘿嘿，以前是在PK的书上看到 AP 的镜子的，好像是在 埃尔斯岩 上，一个美国的爱好者的 130 的镜子。
不知道这个镜子和 髙橋 大致规格的镜子 从性能上的比较起来如何。
[size=+2]Astro-Physics is asingular force in the little world of amateur astronomy equipment.Roland and Marjorie Christen, its owners (with Roland as chief designerand optician) have become legendary figures, though neither isespecially intimidating in person. They and their company areresponsible for a good part of the telescope landscape of today. Theongoing boom in refractors of all kinds can largely be traced toRoland's pioneeringaffordable triplets. Today's A-P telescopes are less affordable,but are much more refined than those early scopes, and in such demandthat it'simpossible tocall their shop and order a new instrument without first waitingmany years for the chance to do so. To take up this slack, severalother makers ofcomparable telescopes have arisen.
[size=+2]I've purchased four A-Prefractors over the years. I was able to get most of themwith [size=+2]insignificant [size=+2]waitscompared to what people face now. Mysecret? I became aware of their products and started buying themalmost from the beginning, well before the current craze which has ledmore than onefrustrated would-be buyer to lament his bad fortune and circulatebitter opinionsabout A-P's business practices. As more and more A-P scopes reached thefield, enabling stargazers to see andappreciate what a fine refractor of substantial aperture could do,interest built up, until by the late 90s those infamous waitinglists began to lengthen, necessitated by Roland's finite time forfiguring lenses and his unwillingness to compromise the process.
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[size=+2]It's worthremembering where refractors stood in the telescope marketplace of the70s and early 80s. Briefly put, you rarely saw them. The scopes in useby serious observers and photographers were Newtonians andSchmidt-Cassegrains. Refractors were limited to long-focusbeginner scopes of three inches and below, many of dubious quality,most of themsold through catalogs and department stores. Larger ones were rare, andcolor-free apochromats almost non-existent except for extremelyexpensive fluorite scopes from Takahashi. Amateurs desiring largerrefractors had few options. They could get anything up to a 6" f/15(with a tube eight feet long) from the A. Jaegers company, but they hadto assemble it themselves. They could buy a 4" Unitron for alarge sum, or even a 5" or a 6" if they controlled vast personalwealth. Otherwise, there were few choices. Astrophotographers foundsuch scopes largely useless. Only a masochist would photograph deep-skytargets at f/15, and faster scopes were plagued with chromaticaberration.
[size=+2]Myadventure withAstro-Physicsbegan in 1985 when I saw their early advertisements for refractors,which were followed by Richard Berry's review of the original 6-inchf/8 in AstronomyMagazine. At the time I had reflectors of 6, 8, and 10-inchaperture, plus a C-8. But I had started my career as an amateurastronomer with small achromatic refractors. Something about thoseelegant instruments had always appealed to me. A compact,6-inch, color-free version promised something like a perfecttelescope, that chimerical Holy Grail pursued by many a guylike me. This was back when a complete, mounted 6-inch could behad for $2450. To finance the purchase, I sold the C-8 and the6 and 10-inch reflectors, hoping their functions could be takenover by the refractor.
[size=+2]Whenthe scope finally showed up (aboutseven months after ordering), the first thing that struck me was itsimposing, commanding size. Its height exceeded my own! The secondthing was the detail I could see on Mars, then just past a fineopposition. The third thing was how much chromatic aberration Isaw. It had quite a bit...more than I thought was appropriatefor an "apochromatic" telescope. I also found the claims forits performance were exaggerated. Rather than offering"planetary performance that puts 12-inch reflectors to shame",it behaved according to the laws of physics rather than thoseof magic, being comparable to my 8-inch Newt in termsof what it could actually show.
[size=+2][size=+2]Thus began a lengthylove-hate relationship with thistelescope. Roland received a stream of peevish complaints. Formonths I spent more of my viewing time agonizing over the color thanactually looking at and appreciating anything. But as timepassed I was won over by the exquisite things I saw throughthis instrument. Star images were much more perfect and stablethan those offered by my reflectors. Once set up, the telescopeworked almost at once, with little cool-down time needed, andnone for collimation. The 706 mount was extremely solid, ifnot very fancy. I saw Gamma Andromedae B as a notchedfigure-8. I saw stars down to magnitude 14.7. The view of theSaturn occultation of 28 Sagittarii was glorious. Eventually the colorerror, which tended to improve as the scope fully stabilized, came toseem unimportant, or at least tolerable.
[size=+2]Nevertheless,when the opportunity cameto upgrade to the new 6-inch f/9 StarFire design, I took it,though I hated to see the original scope go. The new scopeshowed false color only on the brightest stars. The moon andplanets were now shown in their natural colors. As an artist,that came as a relief to me. Pluto was easy to spot in thistelescope. I eventually found myself wanting a moresophisticated mount. Although the Astro-Physics products werevastly improved over the old 706, they were also vastly moreexpensive. I compromised a bit, buying one of the firstLosmandy G-11 mounts, an excellent, relatively inexpensivemount. While not exactly rock steady with a refractor of thislength, it's fine for visual use as long as the wind isminimal. Any guided astrophotography would be a challenge withthis combination. The A-P 900 mount would be preferable, but itcosts more than what I paid for all three of my 6"refractors combined! I keep putting myself on the waiting list forthese mounts, but then I keep turning them down, since I do not yetpossess enormous wealth.
[size=+2]Afew years later, Roland introducedtheEDT telescopes. At the 1993 Winter Star Party, a friend of minebrought his 6-inch StarFire, the same model as mine, while nextdoor was a new EDT of the same size and focal ratio. Isauntered over to this scope, confident that the new glasscould not produce a noticeable improvement over the StarFire.But to my horror and chagrin, I found the images in the EDTwere a bit tighter and more contrasty than those in the olderStarFire. Worse, while observing Jupiter, I found that incomparing the two scopes, I could now discern a slight violethaze surrounding the planet in the StarFire! Falling prey tothe same perfectionistic quest for incremental improvements thatfells many other amateurs, I soon put in an order for my own155mm f/9 EDT. Buying it at the steep price of $3,200 was a stretch forme, even after selling the StarFire for a bit more than I paid for it.I bet many of my readers wish they could call A-P now and order a new155mm refractor for $3,200! I got it just in time for the SL-9 crash onJupiter. I believe it was the last f/9 made. It immediatelystruck me as the most perfect telescope I had ever owned. Itshowed no false color whatsoever, even on Sirius at high power.Images were otherwise flawless as well. This was the firsttelescope I ever owned which I could use without everquestioning its optical performance, which is a great luxury.When I observe with it, I concentrate on the object, and notthe telescope. I always know it's delivering the finest imagethat can be had for its aperture. It's a comfort and a pleasureto use such an instrument.
[size=+2]Inthe spring of 2002I underwentone of those squirmy little fits of dissatisfaction which sometimesafflict amateur astronomers. In my case I was bugged by thesmallness and color of my trusty little TeleVue Pronto. Istarted thinking about the TeleVue 85. Then, like a miracle, myname came up on the AP waiting list for the most hallowed ofall small scopes, the 92mm Stowaway. This avatar of the rareoriginal model is f/6.6 instead of f/4.8. Although it wasexpensive (almost as much as what I paid for my 155 EDT), Idecided to splurge, knowing that I should at least be able toget my money back out of it, barring the total collapse of theeconomy. [size=+2]Thescope arrived at the end of July2002, and of course it is truly a jewel. Here's my initial assessmentaswritten to Roland:
[size=+2]The weatherhere for the past two nights has been soupy andhumid, so conditions have been poor for deep-sky objects. However, theseeing is nearly perfect, giving me a good chance to check out theStowaway.
[size=+2]I'm not anexpert star tester, but I'm unable to see anyreal difference between the in-and-out of focus star images at 180X.When racked out to show a few Fresnel rings the patterns are crisp,perfect, and identical on either side. In focus, the stars areawesome Airy disks with one or two delicate diffraction rings.
[size=+2]Double starperformance is all that I could want. At RTMCthis year, Roger Ceragioli, an optician from the University of ArizonaMirror Lab, brought a 90mm triplet apochromat he had made, about f/11(he was the same guy who star tested my 155mm EDT at the Grand Canyonrecently). Anyway, I looked at Epsilon Bootis through it and was mostimpressed with the clean split. My Questar never does as well.It always blends the secondary into the bright first diffraction ring.Well, the Stowaway handled the star as beautifully as Roger's scope. Italso delivered a clean, pretty split on Delta Cygni. On Nu Scorpii, itcleanly split the fainter pair, and elongated the brighter, closerpair,which I believe is about 1".
[size=+2]I have lookedat a few DSOs, but will have to await abetter night to do much with them. I did get some resolution of M5, andquite good resolution of M13. The sky was so murky I couldbarely even see M4. It will be good to get this scope back tothe California desert.
[size=+2]Now, I said Iwasn't going to complain about color error,and I'm not. I am going to comment on it though. I wassurprised that when viewing Vega at 180X I could just see themerest ghost of a violet halo around it. When I focused in abit I saw a faint violet fringe, and when I focused out I saw afaint yellow-green one.
[size=+2]I do notconsider this to be a problem, as it will never beobtrusive. I was surprised though because I've never seen anycolor, in or out of focus, or under any circumstances, in my 155. Ifigured that a smaller scope with similar glasses would be thesame, even if it does have a shorter focal ratio. Go figure.
[size=+2]Mechanically Ilike most aspects of the scope. Thetwo-speed focuser is cool. I initially had reservations aboutthe rings and slide bar arrangement, but I find it works prettywell on my Telepod head. I do think it would be better if therings could be quickly loosened by hand to facilitate balancechanges. The TeleVue tube ring is great in this regard.
[size=+2]I am puzzled bythe dew cap...it's so short, sticking outonly about two inches in front of the lens. If you're going to providethis elaborate sliding baffled dewcap, which spends most of itstime retracted and adds almost no bulk, why not make it twiceas long? I can't believe it's going to be very effective as adew cap, and hauling Kendrick stuff around with it would be ahassle.
[size=+2]I also thinkthere should be some provision for adding afinder or a sighter of some kind. I really wanted to add a Starbeam,butif I did I suppose it wouldn't fit in the case anymore. I have stuck aRigel Quikfinder on it. Yes, not very aesthetic, but at leastit's not a Telrad.
[size=+2]Oh...the caseis great, very practical and well thought out.
[size=+2]When I got thescope it looked huge, being used to Prontos,but it seems to be shrinking as I look at it. It is as heavy as I'dwantto carry through an airport though. So I'm glad it's not a Traveler.
[size=+2]Rolandreplied with an interestingcomparison of the two objectives that explained the differencein color correction on the Stowaway.
[size=+2]Sincethen I've been ever more impressedby the capabilities of the Stowaway. It's the closest thing to a magictelescope I've ever seen. I often find it hard to believe how small itis when I'm confronted with the beauty and the perfection of the viewsit provides. You can read an even more obsessively detailed review ofit here.
[size=+2]Moon shotthrough 92mm Stowaway with afocal Olympusdigital camera, November 2002
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[size=+2]Hereare excerpts from other lettersI've written to Astro-Physics about the performance of thesetelescopes:
[size=+2]6-inch f/8
[size=+2]I want to tell youabout the great time I had viewing theSaturn-28 Sagittarii occultation with my 6" f/8. Considering the waytheweather has been, it's miraculous that we had a string of three superbnights including July 2-3. We had dry air and very good seeing, even atSaturn's low altitude. The 6" gave probably the best view of SaturnI'veever seen, equal to what I saw with the 12" Zeiss refractor atthe Griffith Observatory. At 250x, the image was crisp and flawless. Itwas one of the very few times I've come close to forgettingthe optics and seeing only the actual object floating before me. Theonly thing that gave away the illusion was the Airy disk anddiffraction ring of 28 Sagittarii. The Encke division was unmistakableduring the best moments, a black hairline in the ansae of the A ring.The globe was very delicately shaded and detailed. During theoccultation, the star was visible throughout its passage behind the Aring. It even faded in and out a few times as it passed behindthe planet itself. It was extremely gratifying to observe this rareevent with such a wonderful set of optics.
[size=+2]6-inch f/8
[size=+2]We recently had apublic star party here at Morehead wherethree telescopes were in use: a C-8, a 24-inch Boller & Chivenscassegrain, and my 6" f/8. We looked at the Moon and a numberof deep-sky objects. The refractor impressed most people as thebest telescope there. It was hard to explain why the viewthrough it was so much nicer than what they saw through the biglight-bucket in the dome (the 24"). I was surprised how good aview of M42 I was able to provide despite the moonlitsemi-urban skies...at 50x, with a UHC filter, the delicatewinglike extensions were beautiful.
[size=+2]For what it'sworth, a few people remarked on the purple glowsurrounding stars like Rigel and Sirius. I told them it was a defect ofthe telescope, but they liked it anyway because they thought it waspretty. Maybe I should have thrown it out of focus to make iteven prettier for them!
[size=+2]6-inch f/8
[size=+2]For years I'vebeen trying to make Antares look like somethingbesides a sparkly red glob of light with a greenish area on oneside. I knew it would take a combination of excellent seeingand a good-sized telescope capable of imaging stars perfectly.I now have the telescope, and I got the seeing in March atabout 5 AM. At 300x, I finally got a clear view of thecompanion of Antares as a separate bit of light, just themerest fleck, but definitely separated. I think it would bepretty easy if Antares ever attained much altitude...
[size=+2]I'vetried other tricky double stars too, with excellent results. Oneexample is Eta Coronae Borealis, mags 5.6 and 5.9 at 0.97",perfectly and neatly split. The star has a companion, mag 12.6, 66"north, which I saw fairly easily at 150x, although the sky transparencywas fair at best that night.
[size=+2]I've had somepretty good deep-sky views with the 6" too. M13at 150x is a starry mass throwing spidery arms of stars off in alldirections. The brightest of the individual stars are bright enough tohold with direct vision. Also at 150x, the Ring Nebula is big andintensely bright, with a pearly center and a hint of green color.
[size=+2]6-inch f/8
[size=+2]MoreheadPlanetarium sponsored two observing sessions forComet Bradfield this past weekend, and I set up my 6" f/8 bothtimes. A number of other scopes were present, including a C-8,a Meade 2080, and a 13" Odyssey. The Great Refractor ruled theevening like a queen rules over the serfs. Bradfield wasdistinctly brighter in the SCTs at the same power, but in imagequality and mechanical stability they couldn't touch therefractor, especially when it came to observing Jupiter. Theseeing was very calm both nights, and the detail visible at200x and 240x was essentially infinite during the moments ofperfect stability. There's a long white streak in the SEB thatseems to wrap about halfway around the planet, and the Red Spotwith its hollow are prominent. Many spots, festoons, and minorbelts were seen too.
[size=+2]The guy with the2080 was blown away by the refractor'sperformance. He hung around for hours looking at Jupiter and deep-skyobjects through it. He was amazed when I identified the Jovian moons bytheir disk sizes and general appearance. As for stability, therefractorwas doing its usual Rock of Gibraltar imitation, while both SCTs didthehula if brushed by eyelashes.
[size=+2]I also found theNorth America nebula for another(inexperienced) observer using his 13" Odyssey and my UHC filter. Itwaseasy to see, but I didn't think it was much more conspicuous than it isin the 6". A smaller high-contrast telescope is just as good assome monster for looking at dim, huge nebulae, at least if youuse a low enough power to keep the same exit pupil size (Iprefer about 5mm).
[size=+2]I'm graduallylearning some important lessons about thistelescope. For one thing, the degree of color error it shows isextremely dependent on the scope's thermal stability. If it hasto cool 20° or so, it can show a colorful image for morethan an hour, but then it undergoes a rapid, almost sudden,improvement.Jupiter's color error has always bothered me most, but lastweekend, the violet glow was very subtle once it had settleddown. It was, I'm happy to say, negligible. I have really come toregardthis telescope as a treasure over the past few months.
[size=+2]Sunspotsshot through 155mm EDTwith afocal Olympus digital camera, October 2002
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6-inch f/8
[size=+2]A few weeks ago Ilooked at Gamma Andromedae B at 300X withgood seeing. I distinctly saw the star, with its 0.5" separation, as a"figure eight" of two merged but discrete star images. One thing thatlent credibility to this observation was that I noticed the two imagesweren't the same size, though at the time I had the mistakenidea they were of equal magnitude. I was also impressed withthe purity of color of the star when slightly defocused...it was deepindigo, in contrast with the golden primary.
[size=+2]Deep-sky objects:I recently had a very fine look at the VeilNebula with 38X through a UHC nebula filter (it was alsovisible without the filter). The section involved with 52 Cygniterminates in an impressive, hard-edged, scimitar-like spike.The whole nebula had plenty of thready, twisted detail. I onlyhad a minute to look before clouds rolled in. To my surprise, Icould still see the nebula through thin clouds that blotted outthe dimmer stars.
[size=+2]I looked at theTrapezium at 200x. Knowing there are more thanfour stars there, I searched and easily spotted 2 more. They turned outto be mag 11, so no great feat to pick up. But they were stillsomething I'd never noticed before.
[size=+2]6-inch StarFire
[size=+2]Just thought youmight like to hear about the Grand CanyonStar Party which I attended at the beginning of the month. I crammedthe6" StarFire into my Celica and had it as my constant andintimate companion throughout my 5 1/2 week trip. At the starparty it was set up in company with Newtonians and SCTs ranging in sizefrom 17.5 " down to 6". Hundreds of people came through. I usually hadthe StarFire aimed at Jupiter. Many people were surprised that such arelatively small instrument so outperformed the big guys on the planet.After the planet got too low I went for deep sky objects, where thecompetition from the mirrors was keener. Nevertheless, I was able toimpress some guys from Australia with views of the Veil, North America,etc. Actually, "impress" is too weak a word. One of those characterswaspractically going into spasms of envy. I told him that if I couldafforda StarFire, anybody could; he replied that I obviously didn't live inAustralia.
[size=+2]6-inch StarFire
[size=+2]I'm oftengratified at the views it provides of even somefairly obscure deep sky objects. For example, the globular cluster NGC6712 in Scutum is large, bright, and surprisingly well-resolvedat 160x. Right next to it, the planetary IC 1298 is a big, easypuff of grey light. They both fit easily into the star-spangledfield of a 22mm Panoptic.
[size=+2]6-inch StarFire
[size=+2]My StarFire beatCornell's 12" f/15 Fecker refractor onSaturn! The Fecker had terrible color...the planet and rings were veryyellow, surrounded by an intense violet-red glow. The image was atriflefuzzy, and had lower contrast and slightly less detail. Only the faintmoons were better seen. This was with really solid seeing, too.
[size=+2]The 6", on theother hand, was razor-sharp, color free, andjust showed more, including the Encke gap in the ansae of therings, which I didn't see with the 12".
[size=+2]You should haveseen the puzzled looks on the faces of thevisitors when they tried to figure out why my (relatively) tinytelescope gave a better view than the jumbo cannon in the dome.It was all I could do not to smugly smirk. It was more than Icould do, actually.
[size=+2][size=+2]155mmEDT [size=+2](photo byJay Ouellet)
[size=+2]The first thing Igot a good look at was Jupiter, and I mustsay my jaw dropped at the sight of it. I caught it at dusk, when theseeing was steadiest and the brilliance of the disk not toooverwhelming. It looked like a drawing done with Prismacolorpencils, the belts intricately inscribed in shades of umber.I've seen white ovals, dark rods, arches and festoons. I don'tthink I've seen anything that couldn't be seen with the (6-inchf/9 StarFire), but I do see a slight improvement in contrastand color rendering.
[size=+2]Naturally, I thenexamined the fiendish star Vega to see justwhat kind of telescope I have here. At 210X it's like looking at thestar through a perfect unobstructed reflector...there's no trace ofcolor except the star's natural pale electric blue. The near-focusimages are much more symmetrical on either side of focus than the oldStarFire's were... The focused image is clearly superior. Withthe old scope, focus on brilliant stars was rather ambiguous...ittendedto "mush" through focus on something as bright as Vega. Focusis much more decisive with the EDT. You don't have to guesswhich point is best. Also, the diffraction rings are different.With the old scope, I usually saw 8-10 diffraction ringssurrounding brilliant stars. I never quite understood why therewere so many. With the EDT, so far I've seen no more than 2, abright inner one and a much fainter second one.
[size=+2]Vega at a mediumpower is like nothing I've ever seen...abrilliant point of astonishing purity on a truly black background. It'sgorgeous, worth looking at for its own sake.
[size=+2]With that out ofthe way, I started doing some actualobserving. I looked at Zeta Herculis, one of the toughest doubles Iknow, a close unequal pair. I could split it with the old sixes, albeitbarely. But the EDT let me clearly separate the stars for the firsttimeand get a good look at the secondary. I used 300X and 600X for that. Itwas the first time I ever actually used 600X to observeanything.
[size=+2]Other than that, Ilooked at a good assortment of deep-skyobjects, including NGC 6572, a tiny planetary in Ophiuchus. In a 22mmPanoptic it was startling, like a bit of sunlit turquoisefloating in the field. I looked at the faint galaxy 6384 inOph, the Crescent Nebula 6888 in Cygnus (which is a full ovalwith a UHC filter), and a bunch of other stuff.
[size=+2]With this purchasemy obsessive quest to obtain the ultimate6" telescope comes to an end. I sometimes reflect (or should Isay refract) on the logic of devoting so much money to a 6"telescope, when for the same money I could be looking throughan excellent 18" reflector. If I lived in an area with reallydark, steady skies, I'd prefer the reflector. But when I'msitting beneath the skies we actually get out here, I'm happyto be using an Astro-Physics refractor. Even when I had areally nice 14.5" reflector, I used the StarFire more than halfthe time. It is amazing and gratifying to see what is visiblein a 6" if you take the trouble to look.
[size=+2]155mmEDT
[size=+2]It seems that Igot my EDT just in time! Who could possiblyhave foreseen the unprecedented observing opportunity providedby S-L 9?
[size=+2]July 19 wasstunning, my first good chance to see much due tothe haze and bad seeing. As soon as I sighted Jupiter in the 155 EDT Iinstantly saw a black spot far in the south-at 45X! Going to 210X I waspresented with a view such as I never imagined I'd see in my lifetime-3huge impact sites marching across Jupiter's SPZ. K was about tomove off the disk and looked like a black dent in the limb. Thebiggest spot, the then-newly-formed L, was near the meridian, and wascolossal, in the GRS league. The third spot, G, was almost aslarge and had only recently come into view.
[size=+2]My view of the Land G spots improved as they straddled themeridian, looking like eyespots on some microorganism. Both had tiny,sharp, black cores offset toward the following edge. Theoverall appearance of both spots was a dark, soft-edged duskygrey. L was outlined or defined on its preceding edge by adarker comma-shaped semicircle. The tiny cores certainly addedto their eyelike appearance.
[size=+2]92mm Stowaway
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[size=+2]I just wanted youto know about the Stowaway's public debut atStellafane, which on Saturday night was about as clear and crisp as itgets there. It was the first really dark night the Stowaway hasseen. It performed as well as I could hope for or expect. Thecluster NGC 7789 in Cassiopeia was a beautiful, finely resolvedcloud of stars at 50X. The bright arc of the Veil filled thefield with detail with the help of a UHC filter. Comet Hoenigwas an easy, slightly mottled glow, looking almost as good asit did in a nearby 10" Dob of uncertain parentage. At 28X theMilky Way showed masses of starry mist riddled with darkintrusions. Sue French even showed me her Toadstool Cluster,French 1.
[size=+2]I look forward tofurther exploring the limits of this scopeback in CA. It's certainly gratifying to have that much scopein a case that small.
[size=+2]The scope is sounobtrusive that few people noticed it orknew what it was. I considered jumping up and down andshouting, but finally decided that privacy was good too.
[size=+2]155mm EDT
[size=+2]I recentlyreturned from the Grand Canyon Star Party, wherefor a week of crystal-clear nights my 155 EDT was set up forpublic use beneath dark skies. On one night of very fine seeingRoger Ceragioli, an optician from the Mirror Lab at the U of A,came by and asked if he could star test the scope. I said sure,being pretty confident there was nothing grossly wrong withit. He fiddled around for a while and finally announced he haddiscovered slight over or undercorrection (he couldn'tremember which it was). I saw what he meant, with the Fresnelrings being slightly less well defined on one side of focusthan the other. He forebore to try to put a wavefront number onthe error, but called it "unimportant but not trivial". He alsodetected the "tertiary spectrum", but I didn't see what hemeant there.
[size=+2]Being a pair ofdouble star fans, we then examined a number ofthem, and what a pleasure that was. Antares just stood there with itscompanion rendered as a perfectly clear Airy disk. You could just sitthere and stare at it. Nu Scorpii was also perfectly shown as fourdelicate Airy discs. Delta Cygni was also perfect, while ZetaBootis, which I believe is closing, was barely resolved at 400X or so.After that, Roger pronounced it an "exquisite" objective.
[size=+2]Even with Jupiteras low as it was, I was able to providesharp views, often following it all the way down into the trees beforegiving up on it. Most visitors proclaimed it the best view ofthe planet available, and it had stiff competition in the form ofnumerous bigger scopes. A fair number said similar things about thedeep-sky views, referring to them as "clearer" than what theywere seeing elsewhere. One night later in the week the Moon wasrevealing jaw-dropping detail. I wished I could just stare at itmyself,but the lines of tourists were long.
[size=+2]92mm Stowaway
[size=+2]With the seeingvery good last night I decided it was time fora definitive showdown between the venerable 89mm Questar and thatpromising upstart the f/6.6 92mm Stowaway. The Q starts out with a 3%aperture disadvantage, but that's not enough to explain the fact thatit was whomped, stomped, and tromped by the Stowaway.
I used both scopes at 180X: the Q with a 12mm Brandon and its internal1.7x Barlow, and the Stowaway with a 6.7mm Meade Ultra Wide and a 2xDakin Barlow. Both scopes had hours to cool.
On Saturn, the cloud belt on the planet and the crepe ring were bothharder to see in the Questar. The Stowaway showed glimpses of a coupleof faint moons which were invisible in the Q. In glancing from onescope to the other, the superiority of the Stowaway was strikinglyobvious.
The differences were even more dramatic on Jupiter. The Stowaway showedmuch delicate detail in the equatorial belts: a bay, a dark barge, somesplitting of the SEB into northern and southern components. In the Qthe belts were essentially featureless. Even knowing where thesedetails were, they were difficult or impossible to see in the Q. Theshadow of Callisto was also easier to see in the Stowaway. In the Q themoons showed distinct diffraction rings and looked like stars (albeitvery sharp stars). In the Stowaway the rings were almost indiscernible,and the moons looked more like moons.
The Q gave nice views. But the Stowaway was so much sharper, brighter,and more contrasty that it was hard to believe both scopes were almostthe same size. Its views of Jupiter were so exquisite that it was hardfor me to tear my eyes away. What a glorious little telescope. Inaddition, my recent tests of limiting magnitude showed stars down to13.5 at least. I have not tested the Q at better than 12.6.
[size=+2]92mm Stowaway and 155mm EDT
[size=+2]Last weekend wasgorgeous here, so I was out on two nights with the 155mm. It was myfirst time splitting Gamma Virginis (Porrima) since it started to openup again. It's now at about 0.8". Despite crappy seeing at its lowaltitude, I was usually able to see two little balls touching eachother at powers of around 400X. I also looked at Eta Geminorum(Propus), which has the reputation of being tough. The close unequalpair was pretty easy at around 300X, reminding me of a dimmer, closerversion of Antares and its companion. I earlier tried this pair fromFlorida with the Stowaway, but got nowhere with that aperture. The mostfun I had last weekend was looking at the moon with my binoviewer. Thedetail I saw everywhere at 230x was stunning. Among the things thatparticularly caught my eyes were the hairlike shadow cast by the Cauchyfault, the U-shaped mountain range inside the crater Fabricius, therilles near Plinius which seem to run along a low, broad swelling onthe mare, and the strange buried crater Lamont.
In February I had the Stowaway down at the Winter Star Party. We hadonly two mostly usable nights there this year, so I didn't get to dotoo much. I made a drawing of M42 and looked at a number of otherthings, including a section of Barnard's Loop and some extremelyobscure objects like the open clusters Tombaugh 1 and 2, which arepretty challenging for such a small scope. I spotted 8 galaxies in theFornax cluster. I tried to split Sirius, but the scope was too small.The previous year I was able to see Sirius B with the 155mm from there.
In January I used the 92mm to see Comet McNaught low in the twilight.Last fall I used it and the 155mm to see Comet Swan.
In June I had the 155mm out at the Grand Canyon Star Party. It has beenthere several times, and the 92mm has been there at least twice. Eitherscope entertains hundreds of tourists with views of Jupiter andwhatever else I feel like showing. They both collect lots ofunsolicited remarks about their views being the best available at theparty. I often wind up trying to explain why this is so without beingtoo insulting about the SCTs and reflectors used by most of the otherguys. I hope to make it out there again this June, and if so I willprobably bring one of the APs.
Finally, I used both scopes last spring to see the fragments of CometSchwassmann-Wachmann.
So, I hope this eases your mind about whether I still use the scopes. Iknow I don't write about my experiences the way I used to, but I didthat mostly back when I was still figuring out what these scopes coulddo. I now have a pretty good idea, so I tend to just use them withouttalking about it very much. If I ever get another of your scopes, I'msure you'll hear all about my initial results with that one too. |
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