Joe Bergeron's Astro-Physics Page
singular force in the little world of amateur
Roland and Marjorie Christen, its owners (with
Roland as chief designer
and optician) have become legendary figures,
though neither is
especially intimidating in person. They and their
responsible for a good part of the telescope
landscape of today. The
ongoing boom in refractors of all kinds can
largely be traced to
affordable triplets. Today's A-P telescopes are
but are much more refined than those early scopes,
and in such demand
call their shop and order a new instrument without
many years for the chance to do so. To take up
this slack, several
other makers of
comparable telescopes have arisen.
purchased four A-P
refractors over the years. I was able to get most
to what people face now. My
secret? I became aware of their products and
started buying them
almost from the beginning, well before the current
craze which has led
more than one
frustrated would-be buyer to lament his bad
fortune and circulate
about A-P's business practices. As more and more
A-P scopes reached the
field, enabling stargazers to see and
appreciate what a fine refractor of substantial
aperture could do,
interest built up, until by the late 90s those
lists began to lengthen, necessitated by Roland's
finite time for
figuring lenses and his unwillingness to
compromise the process.
remembering where refractors stood in the
telescope marketplace of the
70s and early 80s. Briefly put, you rarely saw
them. The scopes in use
by serious observers and photographers were
Schmidt-Cassegrains. Refractors were limited to
beginner scopes of three inches and below, many of
most of them
sold through catalogs and department stores.
Larger ones were rare, and
color-free apochromats almost non-existent except
expensive fluorite scopes from Takahashi. Amateurs
refractors 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 had
to assemble it themselves. They could buy a 4"
Unitron for a
large sum, or even a 5" or a 6" if they controlled
wealth. Otherwise, there were few choices.
such scopes largely useless. Only a masochist
would photograph deep-sky
targets at f/15, and faster scopes were plagued
My adventure with Astro-Physics began in 1985 when I saw their early advertisements for refractors, which were followed by Richard Berry's review of the original 6-inch f/8 in Astronomy Magazine. At the time I had reflectors of 6, 8, and 10-inch aperture, plus a C-8. But I had started my career as an amateur astronomer with small achromatic refractors. Something about those elegant instruments had always appealed to me. A compact, 6-inch, color-free version promised something like a perfect telescope, that chimerical Holy Grail pursued by many a guy like me. This was back when a complete, mounted 6-inch could be had for $2450. To finance the purchase, I sold the C-8 and the 6 and 10-inch reflectors, hoping their functions could be taken over by the refractor.
When the scope finally showed up (about seven months after ordering), the first thing that struck me was its imposing, commanding size. Its height exceeded my own! The second thing was the detail I could see on Mars, then just past a fine opposition. The third thing was how much chromatic aberration I saw. It had quite a bit...more than I thought was appropriate for an "apochromatic" telescope. I also found the claims for its 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 those of magic, being comparable to my 8-inch Newt in terms of what it could actually show.
Thus began a lengthy love-hate relationship with this telescope. Roland received a stream of peevish complaints. For months I spent more of my viewing time agonizing over the color than actually looking at and appreciating anything. But as time passed I was won over by the exquisite things I saw through this instrument. Star images were much more perfect and stable than those offered by my reflectors. Once set up, the telescope worked almost at once, with little cool-down time needed, and none for collimation. The 706 mount was extremely solid, if not very fancy. I saw Gamma Andromedae B as a notched figure-8. I saw stars down to magnitude 14.7. The view of the Saturn occultation of 28 Sagittarii was glorious. Eventually the color error, which tended to improve as the scope fully stabilized, came to seem unimportant, or at least tolerable.
the opportunity came
to upgrade to the new 6-inch f/9 StarFire
design, I took it,
though I hated to see the original scope go.
The new scope
showed false color only on the brightest
stars. The moon and
planets were now shown in their natural
colors. As an artist,
that came as a relief to me. Pluto was easy to
spot in this
telescope. I eventually found myself wanting a
sophisticated mount. Although the
Astro-Physics products were
vastly improved over the old 706, they were
also vastly more
expensive. I compromised a bit, buying one of
Losmandy G-11 mounts, an excellent, relatively
mount. While not exactly rock steady with a
refractor of this
length, it's fine for visual use as long as
the wind is
minimal. Any guided astrophotography would be
a challenge with
this combination. The A-P 1100 mount would be
preferable, but it
costs more than what I paid for all three of
refractors combined! I keep putting myself on
the waiting list for
these mounts, but then I keep turning them
down, since I do not yet
possess enormous wealth.
few years later, Roland introduced
EDT telescopes. At the 1993 Winter Star Party,
a friend of mine
brought his 6-inch StarFire, the same model as
mine, while next
door was a new EDT of the same size and focal
sauntered over to this scope, confident that
the new glass
could not produce a noticeable improvement
over the StarFire.
But to my horror and chagrin, I found the
images in the EDT
were a bit tighter and more contrasty than
those in the older
StarFire. Worse, while observing Jupiter, I
found that in
comparing the two scopes, I could now discern
a slight violet
haze surrounding the planet in the StarFire!
Falling prey to
the same perfectionistic quest for incremental
fells many other amateurs, I soon put in an
order for my own
155mm f/9 EDT. Buying it at the steep price of
$3,200 was a stretch for
me, 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 new
155mm refractor for $3,200! I got it just in
time for the SL-9 crash on
Jupiter. I believe it was the last f/9 made.
struck me as the most perfect telescope I had
ever owned. It
showed no false color whatsoever, even on
Sirius at high power.
Images were otherwise flawless as well. This
was the first
telescope I ever owned which I could use
questioning its optical performance, which is
a great luxury.
When I observe with it, I concentrate on the
object, and not
the telescope. I always know it's delivering
the finest image
that can be had for its aperture. It's a
comfort and a pleasure
to use such an instrument.
The scope arrived at the end of July 2002, and of course it is truly a jewel. Here's my initial assessment as written to Roland:
The weather here for the past two nights has been soupy and humid, so conditions have been poor for deep-sky objects. However, the seeing is nearly perfect, giving me a good chance to check out the Stowaway.
I'm not an expert star tester, but I'm unable to see any real 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 are awesome Airy disks with one or two delicate diffraction rings.
Double star performance is all that I could want. At RTMC this year, Roger Ceragioli, an optician from the University of Arizona Mirror 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 Canyon recently). Anyway, I looked at Epsilon Bootis through it and was most impressed 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. It also delivered a clean, pretty split on Delta Cygni. On Nu Scorpii, it cleanly split the fainter pair, and elongated the brighter, closer pair, which I believe is about 1".
I have looked at a few DSOs, but will have to await a better night to do much with them. I did get some resolution of M5, and quite good resolution of M13. The sky was so murky I could barely even see M4. It will be good to get this scope back to the California desert.
Now, I said I wasn't going to complain about color error, and I'm not. I am going to comment on it though. I was surprised that when viewing Vega at 180X I could just see the merest ghost of a violet halo around it. When I focused in a bit I saw a faint violet fringe, and when I focused out I saw a faint yellow-green one.
I do not consider this to be a problem, as it will never be obtrusive. I was surprised though because I've never seen any color, in or out of focus, or under any circumstances, in my 155. I figured that a smaller scope with similar glasses would be the same, even if it does have a shorter focal ratio. Go figure.
Mechanically I like most aspects of the scope. The two-speed focuser is cool. I initially had reservations about the rings and slide bar arrangement, but I find it works pretty well on my Telepod head. I do think it would be better if the rings could be quickly loosened by hand to facilitate balance changes. The TeleVue tube ring is great in this regard.
I am puzzled by the dew cap...it's so short, sticking out only about two inches in front of the lens. If you're going to provide this elaborate sliding baffled dewcap, which spends most of its time retracted and adds almost no bulk, why not make it twice as long? I can't believe it's going to be very effective as a dew cap, and hauling Kendrick stuff around with it would be a hassle.
I also think there should be some provision for adding a finder or a sighter of some kind. I really wanted to add a Starbeam, but if I did I suppose it wouldn't fit in the case anymore. I have stuck a Rigel Quikfinder on it. Yes, not very aesthetic, but at least it's not a Telrad.
Oh...the case is great, very practical and well thought out.
When I got the scope it looked huge, being used to Prontos, but it seems to be shrinking as I look at it. It is as heavy as I'd want to carry through an airport though. So I'm glad it's not a Traveler.
with an interesting
comparison of the two objectives that
explained the difference
in color correction on the Stowaway.
I've been ever more impressed
by the capabilities of the Stowaway. It's the
closest thing to a magic
telescope I've ever seen. I often find it hard
to believe how small it
is when I'm confronted with the beauty and the
perfection of the views
it provides. You can read an even more
obsessively detailed review of
through 92mm Stowaway with afocal Olympus
digital camera, November 2002
Here are excerpts from other letters I've written to Astro-Physics about the performance of these telescopes:
I want to tell you about the great time I had viewing the Saturn-28 Sagittarii occultation with my 6" f/8. Considering the way the weather has been, it's miraculous that we had a string of three superb nights including July 2-3. We had dry air and very good seeing, even at Saturn's low altitude. The 6" gave probably the best view of Saturn I've ever seen, equal to what I saw with the 12" Zeiss refractor at the Griffith Observatory. At 250x, the image was crisp and flawless. It was one of the very few times I've come close to forgetting the optics and seeing only the actual object floating before me. The only thing that gave away the illusion was the Airy disk and diffraction ring of 28 Sagittarii. The Encke division was unmistakable during the best moments, a black hairline in the ansae of the A ring. The globe was very delicately shaded and detailed. During the occultation, the star was visible throughout its passage behind the A ring. It even faded in and out a few times as it passed behind the planet itself. It was extremely gratifying to observe this rare event with such a wonderful set of optics.
We recently had a public star party here at Morehead where three telescopes were in use: a C-8, a 24-inch Boller & Chivens cassegrain, and my 6" f/8. We looked at the Moon and a number of deep-sky objects. The refractor impressed most people as the best telescope there. It was hard to explain why the view through it was so much nicer than what they saw through the big light-bucket in the dome (the 24"). I was surprised how good a view of M42 I was able to provide despite the moonlit semi-urban skies...at 50x, with a UHC filter, the delicate winglike extensions were beautiful.
For what it's worth, a few people remarked on the purple glow surrounding stars like Rigel and Sirius. I told them it was a defect of the telescope, but they liked it anyway because they thought it was pretty. Maybe I should have thrown it out of focus to make it even prettier for them!
For years I've been trying to make Antares look like something besides a sparkly red glob of light with a greenish area on one side. I knew it would take a combination of excellent seeing and a good-sized telescope capable of imaging stars perfectly. I now have the telescope, and I got the seeing in March at about 5 AM. At 300x, I finally got a clear view of the companion of Antares as a separate bit of light, just the merest fleck, but definitely separated. I think it would be pretty easy if Antares ever attained much altitude...
I've tried other tricky double stars too, with excellent results. One example 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 transparency was fair at best that night.
I've had some pretty good deep-sky views with the 6" too. M13 at 150x is a starry mass throwing spidery arms of stars off in all directions. The brightest of the individual stars are bright enough to hold with direct vision. Also at 150x, the Ring Nebula is big and intensely bright, with a pearly center and a hint of green color.
Morehead Planetarium sponsored two observing sessions for Comet Bradfield this past weekend, and I set up my 6" f/8 both times. A number of other scopes were present, including a C-8, a Meade 2080, and a 13" Odyssey. The Great Refractor ruled the evening like a queen rules over the serfs. Bradfield was distinctly brighter in the SCTs at the same power, but in image quality and mechanical stability they couldn't touch the refractor, especially when it came to observing Jupiter. The seeing was very calm both nights, and the detail visible at 200x and 240x was essentially infinite during the moments of perfect stability. There's a long white streak in the SEB that seems to wrap about halfway around the planet, and the Red Spot with its hollow are prominent. Many spots, festoons, and minor belts were seen too.
The guy with the 2080 was blown away by the refractor's performance. He hung around for hours looking at Jupiter and deep-sky objects through it. He was amazed when I identified the Jovian moons by their disk sizes and general appearance. As for stability, the refractor was doing its usual Rock of Gibraltar imitation, while both SCTs did the hula if brushed by eyelashes.
I also found the North America nebula for another (inexperienced) observer using his 13" Odyssey and my UHC filter. It was easy to see, but I didn't think it was much more conspicuous than it is in the 6". A smaller high-contrast telescope is just as good as some monster for looking at dim, huge nebulae, at least if you use a low enough power to keep the same exit pupil size (I prefer about 5mm).
learning some important lessons about this
telescope. For one thing, the degree of color
error it shows is
extremely dependent on the scope's thermal
stability. If it has
to cool 20° or so, it can show a colorful
image for more
than an hour, but then it undergoes a rapid,
Jupiter's color error has always bothered me
most, but last
weekend, the violet glow was very subtle once
it had settled
down. It was, I'm happy to say, negligible. I
have really come to
this telescope as a treasure over the past few
shot through 155mm EDT
with afocal Olympus digital camera, October
A few weeks ago I looked at Gamma Andromedae B at 300X with good seeing. I distinctly saw the star, with its 0.5" separation, as a "figure eight" of two merged but discrete star images. One thing that lent credibility to this observation was that I noticed the two images weren't the same size, though at the time I had the mistaken idea they were of equal magnitude. I was also impressed with the purity of color of the star when slightly defocused...it was deep indigo, in contrast with the golden primary.
Deep-sky objects: I recently had a very fine look at the Veil Nebula with 38X through a UHC nebula filter (it was also visible without the filter). The section involved with 52 Cygni terminates in an impressive, hard-edged, scimitar-like spike. The whole nebula had plenty of thready, twisted detail. I only had a minute to look before clouds rolled in. To my surprise, I could still see the nebula through thin clouds that blotted out the dimmer stars.
I looked at the Trapezium at 200x. Knowing there are more than four stars there, I searched and easily spotted 2 more. They turned out to be mag 11, so no great feat to pick up. But they were still something I'd never noticed before.
Just thought you might like to hear about the Grand Canyon Star Party which I attended at the beginning of the month. I crammed the 6" StarFire into my Celica and had it as my constant and intimate companion throughout my 5 1/2 week trip. At the star party it was set up in company with Newtonians and SCTs ranging in size from 17.5 " down to 6". Hundreds of people came through. I usually had the StarFire aimed at Jupiter. Many people were surprised that such a relatively small instrument so outperformed the big guys on the planet. After the planet got too low I went for deep sky objects, where the competition from the mirrors was keener. Nevertheless, I was able to impress some guys from Australia with views of the Veil, North America, etc. Actually, "impress" is too weak a word. One of those characters was practically going into spasms of envy. I told him that if I could afford a StarFire, anybody could; he replied that I obviously didn't live in Australia.
I'm often gratified at the views it provides of even some fairly obscure deep sky objects. For example, the globular cluster NGC 6712 in Scutum is large, bright, and surprisingly well-resolved at 160x. Right next to it, the planetary IC 1298 is a big, easy puff of grey light. They both fit easily into the star-spangled field of a 22mm Panoptic.
My StarFire beat Cornell's 12" f/15 Fecker refractor on Saturn! The Fecker had terrible color...the planet and rings were very yellow, surrounded by an intense violet-red glow. The image was a trifle fuzzy, and had lower contrast and slightly less detail. Only the faint moons were better seen. This was with really solid seeing, too.
The 6", on the other hand, was razor-sharp, color free, and just showed more, including the Encke gap in the ansae of the rings, which I didn't see with the 12".
You should have seen the puzzled looks on the faces of the visitors when they tried to figure out why my (relatively) tiny telescope 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 I could do, actually.
155mm EDT (photo by Jay Ouellet)
The first thing I got a good look at was Jupiter, and I must say my jaw dropped at the sight of it. I caught it at dusk, when the seeing was steadiest and the brilliance of the disk not too overwhelming. It looked like a drawing done with Prismacolor pencils, the belts intricately inscribed in shades of umber. I've seen white ovals, dark rods, arches and festoons. I don't think I've seen anything that couldn't be seen with the (6-inch f/9 StarFire), but I do see a slight improvement in contrast and color rendering.
Naturally, I then examined the fiendish star Vega to see just what kind of telescope I have here. At 210X it's like looking at the star through a perfect unobstructed reflector...there's no trace of color except the star's natural pale electric blue. The near-focus images are much more symmetrical on either side of focus than the old StarFire's were... The focused image is clearly superior. With the old scope, focus on brilliant stars was rather ambiguous...it tended to "mush" through focus on something as bright as Vega. Focus is much more decisive with the EDT. You don't have to guess which point is best. Also, the diffraction rings are different. With the old scope, I usually saw 8-10 diffraction rings surrounding brilliant stars. I never quite understood why there were so many. With the EDT, so far I've seen no more than 2, a bright inner one and a much fainter second one.
Vega at a medium power is like nothing I've ever seen...a brilliant point of astonishing purity on a truly black background. It's gorgeous, worth looking at for its own sake.
With that out of the way, I started doing some actual observing. I looked at Zeta Herculis, one of the toughest doubles I know, a close unequal pair. I could split it with the old sixes, albeit barely. But the EDT let me clearly separate the stars for the first time and get a good look at the secondary. I used 300X and 600X for that. It was the first time I ever actually used 600X to observe anything.
Other than that, I looked at a good assortment of deep-sky objects, including NGC 6572, a tiny planetary in Ophiuchus. In a 22mm Panoptic it was startling, like a bit of sunlit turquoise floating in the field. I looked at the faint galaxy 6384 in Oph, the Crescent Nebula 6888 in Cygnus (which is a full oval with a UHC filter), and a bunch of other stuff.
With this purchase my obsessive quest to obtain the ultimate 6" telescope comes to an end. I sometimes reflect (or should I say refract) on the logic of devoting so much money to a 6" telescope, when for the same money I could be looking through an excellent 18" reflector. If I lived in an area with really dark, steady skies, I'd prefer the reflector. But when I'm sitting beneath the skies we actually get out here, I'm happy to be using an Astro-Physics refractor. Even when I had a really nice 14.5" reflector, I used the StarFire more than half the time. It is amazing and gratifying to see what is visible in a 6" if you take the trouble to look.
It seems that I got my EDT just in time! Who could possibly have foreseen the unprecedented observing opportunity provided by S-L 9?
July 19 was stunning, my first good chance to see much due to the haze and bad seeing. As soon as I sighted Jupiter in the 155 EDT I instantly saw a black spot far in the south-at 45X! Going to 210X I was presented with a view such as I never imagined I'd see in my lifetime-3 huge impact sites marching across Jupiter's SPZ. K was about to move off the disk and looked like a black dent in the limb. The biggest spot, the then-newly-formed L, was near the meridian, and was colossal, in the GRS league. The third spot, G, was almost as large and had only recently come into view.
My view of the L and G spots improved as they straddled the meridian, looking like eyespots on some microorganism. Both had tiny, sharp, black cores offset toward the following edge. The overall appearance of both spots was a dark, soft-edged dusky grey. L was outlined or defined on its preceding edge by a darker comma-shaped semicircle. The tiny cores certainly added to their eyelike appearance.
I just wanted you to know about the Stowaway's public debut at Stellafane, which on Saturday night was about as clear and crisp as it gets there. It was the first really dark night the Stowaway has seen. It performed as well as I could hope for or expect. The cluster NGC 7789 in Cassiopeia was a beautiful, finely resolved cloud of stars at 50X. The bright arc of the Veil filled the field with detail with the help of a UHC filter. Comet Hoenig was an easy, slightly mottled glow, looking almost as good as it did in a nearby 10" Dob of uncertain parentage. At 28X the Milky Way showed masses of starry mist riddled with dark intrusions. Sue French even showed me her Toadstool Cluster, French 1.
I look forward to further exploring the limits of this scope back in CA. It's certainly gratifying to have that much scope in a case that small.
The scope is so unobtrusive that few people noticed it or knew what it was. I considered jumping up and down and shouting, but finally decided that privacy was good too.
I recently returned from the Grand Canyon Star Party, where for a week of crystal-clear nights my 155 EDT was set up for public use beneath dark skies. On one night of very fine seeing Roger 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 with it. He fiddled around for a while and finally announced he had discovered slight over or undercorrection (he couldn't remember which it was). I saw what he meant, with the Fresnel rings being slightly less well defined on one side of focus than the other. He forebore to try to put a wavefront number on the error, but called it "unimportant but not trivial". He also detected the "tertiary spectrum", but I didn't see what he meant there.
Being a pair of double star fans, we then examined a number of them, and what a pleasure that was. Antares just stood there with its companion rendered as a perfectly clear Airy disk. You could just sit there and stare at it. Nu Scorpii was also perfectly shown as four delicate Airy discs. Delta Cygni was also perfect, while Zeta Bootis, which I believe is closing, was barely resolved at 400X or so. After that, Roger pronounced it an "exquisite" objective.
as low as it was, I was able to provide
sharp views, often following it all the way
down into the trees before
giving up on it. Most visitors proclaimed it
the best view of
the planet available, and it had stiff
competition in the form of
numerous bigger scopes. A fair number said
similar things about the
deep-sky views, referring to them as "clearer"
than what they
were seeing elsewhere. One night later in the
week the Moon was
revealing jaw-dropping detail. I wished I
could just stare at it
but the lines of tourists were long.
very good last night I decided it was time for
a definitive showdown between the venerable
89mm Questar and that
promising 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 that
it was whomped, stomped, and tromped by the
92mm Stowaway and
gorgeous here, so I was out on two nights with
the 155mm. It was my
first time splitting Gamma Virginis (Porrima)
since it started to open
up again. It's now at about 0.8". Despite
crappy seeing at its low
altitude, I was usually able to see two little
balls touching each
other at powers of around 400X. I also looked
at Eta Geminorum
(Propus), which has the reputation of being
tough. The close unequal
pair was pretty easy at around 300X, reminding
me of a dimmer, closer
version of Antares and its companion. I
earlier tried this pair from
Florida with the Stowaway, but got nowhere
with that aperture. The most
fun I had last weekend was looking at the moon
with my binoviewer. The
detail I saw everywhere at 230x was stunning.
Among the things that
particularly caught my eyes were the hairlike
shadow cast by the Cauchy
fault, the U-shaped mountain range inside the
crater Fabricius, the
rilles near Plinius which seem to run along a
low, broad swelling on
the mare, and the strange buried crater
Words and images copyright by Joe Bergeron.