Astro
Physics Starfire 130 EDT F8 Review
Five-inch (125-130mm) apochromats make
great planetary and lunar scopes because they resolve to the maximum allowed by
seeing in most places on most nights (c. 1”) and yet are still fairly light and
compact. One of the most storied 5” apo’s, one intended specifically for visual
use at high powers, is Astro Physics’ 130 EDT.
This telescope is widely regarded as
one of AP’s very finest and thus one of the best small planetary scopes you
could buy. Trouble is that statement has to be backed up with several caveats.
The easiest to deal with is the ‘buy’
part because you can’t, new at least – these haven’t been made since 2002. Even
if AP do another run, you’ll only get one if you’ve been on the waiting list
for 20 years or if you win a lottery (literally). You’d have to find a used one
as I did.
The more difficult caveat to deal with
is the ‘widely regarded’ bit. That’s because this telescope – the 130 EDT – was
made in multiple runs over about a decade and not all the scopes in those runs
were the same (or even all that similar in the details). So
are all the variants as highly regarded? I just don’t know and struggled to
find out. Which means we’ll have to overlook the considerable lore and hype,
just take this telescope on its own merits as usual.
At
A Glance
|
Telescope |
AP 130 EDT
Starfire |
|
Aperture |
130mm |
|
Focal
Length |
1040mm |
|
Focal
Ratio |
F8 (Second
run 8.35) |
|
Length |
914mm w/o
dewshield |
|
Weight |
7.3 kg OTA |
Data from AP/Company 7/Me.
Design
and Build
As I said, AP
produced several runs of this telescope with varying details. If you’re
thinking of buying one this matters and you should do your own research: AP
themselves are very approachable and support their older products too.
The first run
appears to have started around 1991 (when this was built) and continued until
around 1995.
AP then later
did two further runs from 1999 or so until 2002. The later scopes just employ a
cut-down 155/1085 EDF lens (the EDT name was retained for marketing reasons) with
a slightly longer focal length (1085mm vs 1040mm).
In any case,
this is an early scope from the first run, made (according to AP) in 1991 with
an air-spaced objective.
I should
mention the F6 versions, 130 EDF and 130 GT (Gran Turismo – Roland is a muscle
car fan), which have been made in more recent runs.
130 EDT objective
with inset laser test showing its triplet design, possibly with two different
flint elements.
Current
production Stowaway lens for comparison.
Optics
‘EDT’ simply
stands for ED Triplet, so unsurprisingly the objective is a 130mm air-spaced
(in this case and confirmed by AP) triplet with an internal positive crown
sandwiched between two negative flints (see laser test above). That’s good
because ED crowns are usually more delicate and softer than flint glasses and
benefit from being out of harm’s (and dew’s) way in the middle.
From there
things get murkier, because (at risk of repeating myself) AP produced several
runs of this telescope with different characteristics and glasses. This early
130 EDT is an F8 (later ones were F8.35) and probably employs FPL-52 as its ED
glass crown, where later versions used FPL-53. The flints may be ZKN7 or possibly
BK7 (though the two appear different – see laser test above).
Did the later
runs – where the lens is purportedly a cut-down 155 EDF - use a
different/better ED glass, such as FPL-53, perhaps mated to a different flint?
Probably, but I can’t find out for sure. Were the later runs better corrected?
Again, probably, but then again Roland has said not really.
A related question is oil-spaced or air-spaced? A 130 EDT could be either.
It turns out that the early F8 objectives (like this one) are all air-spaced,
whilst the later F8.35 EDF-based lenses are oil-spaced (AP confirmed this).
So it should be easy enough to figure out whether yours is oil or air-spaced.
But if you’re unsure, the best way is to find the serial number – written in pencil on the edge of the lens – and ask AP.
Another possible way to check is to consider the colour of the objective glass.
Oil spaced lenses were wrapped at the edge in Kaptan tape which is yellow and tends to give the whole objective a yellowish hue
(or so I’ve read – I haven’t personally seen an oil-filled AP lens from this era).
AP lenses
are generally of the highest quality, even if they don’t provide test reports
as (for example) LZOS do. Roland is known to ruthlessly reject blanks with too
many inclusions or bubbles or with poor homogeneity, blanks which would
probably end up in lenses elsewhere. Both the Traveler and Stowaway I’ve owned
had something special about their lenses in terms of sharpness and contrast at
very high power and I’ve wondered if this is why.
Note that unlike
the smaller Traveler, the 130 EDT does have collimation hex-bolts, placed on
the outside of the cell.
One thing
that definitely isn’t of the very best about this particular lens is its
coatings, which seem to be rather paler and more reflective than modern ones.
Tube
The Traveler
I reviewed had an all-CNC tube and a clever sliding dew-shield built-in; everything
threaded together and the baffles were an all-in-one foam item. That early
Traveler was finished in gloss black paint. Meanwhile, modern APs like my
Stowaway have a tough cream powder coating that’s more subtly textured than,
say, a TeleVue.
In contrast,
this 130 EDT has a more traditional tube, made (I think) of rolled aluminium
coated with a glossy white paint finish and fitted with knife-edge baffles. Unlike
later APs, the objective cell is not thread-on, but is attached with tiny hex
bolts.
The
dew-shield is an unusual, detachable design that pushes over a flange on the
lens cell in use, but can be flipped and slid over the tube for compact
storage. This works because the front and rear have a slightly different
diameter. It’s a quick and ingenious system that’s simple and adds no weight,
but means the dew-cap is a loose fit with the scope stored because it then
covers the narrower end of the shield.
The plus
side of this system is that – despite being an F8 - the 130 EDT is one of the
smallest and lightest 5” apochromats, weighing in at a just over 7Kg without
its rings. It’s thus the same weight as a Takahashi FS-128 from the same era,
but is more compact. Most ~5” apochromats are much heavier and bulkier (a big
advantage that’s true of most AP scopes).
Note that
the later F8.35 version was the same weight, but slightly longer as you’d
expect.
Focuser
Astro-Physics
focusers are one of a few distinct and original designs that have persisted for
decades, though some recent APs have started to come with Starlight
Instruments’ Feathertouch focuser. That’s
understandable given the quality of the Feathertouch
and the effort it must save AP, but it’s a shame because – like the Classic
Takahashi focuser – the AP units have their own character and merit.
In this
early (but I think still CNC milled) example, the 2.7” drawtube boasts lots of
travel (about 4”), beautifully machined internal baffling and chunky knobs milled
from solid aluminium. The 130 EDT (all of them I think) came with a
single-speed focuser appropriate to its slower focal ratio and wider
sweet-spot.
The specs
are similar to 2.7” Takahashi (with whom AP was openly competing) focusers of
that era, but the action is quite different: heavier and less buttery smooth,
but with even better control of slop and shift. The action is different from a
light and oily-slick Feathertouch too.
The 2”
visual back has a single set screw and a lock-ring, but it threads on and could
be swapped for the more modern version with three screws for extra stability
and orthogonality.
The whole focuser
is held into the tube adapter with a kind of dovetail and a set-screw. It’s
easy to remove and can be upgraded with a dual-speed version if you wish (at a
cost direct from AP of about $1100 at the time of writing). Should you bother?
The answer has little to do with the scope, but rather how stable your mount
is. As we’ll see, when hugely over-mounted on an AP1200 dual-speed just wasn’t
necessary. More marginally mounted on a Vixen SX2 (a medium mount with a weight
and capacity of ~10 Kg), vibes mean it’s hard to get perfect focus without fine
adjustment.
Heavy duty
2.7” focuser – fabricated by AP, stable and lots of travel, but single speed.
Traveler
version of the same 2.7” focuser, fitted with an after-market dual speed
pinion.
Mounting
I’ve rather
ruined the suspense on this section – as I said above, I mounted it on an AP1200
(capable of hefting almost ten times as much) and on a small-medium sized Vixen
SX2 which was close to its maximum capacity of ~10 Kg, but still quite usable
with the 130 EDT, albeit with some slow-to-settle vibes (the AP1200 setup was
completely vibe free at any power).
This 130EDT
came with typical AP rings, which are CNC-made and very slim to reduce weight.
These are coated in the crinkle black that was universal on scopes from the
1950s-1970s, but more recent ones will be anodised. You should still be able to
buy rings from AP at the time of writing.
The rings
have useful hole arrangements top and bottom that allow attachment to AP’s own
plates and dovetails: for the AP1200 sessions, I mounted them directly on a
massive fixed plate that really adds to stability. For the Vixen, I used a
cheap 3rd party dovetail that just bolted on to the central ¼-20
threads of the AP rings, but AP do make a much more refined Vixen-fit dovetail
of their own.
AP130EDT (over)
mounted on an AP1200: fixed plate makes for zero vibes.
Accessories
AP sell a
full range of accessories, mostly machined in house with the very highest
design and fabrication quality and prices to match. Obvious accessories for the
EDT include the dual-speed focuser already mentioned, along with rings and
various plates and dovetails including Vixen/Sky-Watcher fit (see above) and Losmandy’s heavy-duty ‘D’ system.
Like most AP
scopes, this EDT came in a handsome custom-made case that has a wooden carcass
covered in grey leatherette and lined with cut foam (which is starting to
harden and crumble a bit after 30 years).
Classic
wood-framed AP case.
In
Use – Daytime
My usual
(qualitative only) daytime test of viewing silhouetted branches at 100x yielded
very low (but not quite absent) levels of false colour and spherochromatism - a
trace of purple and violet around the branches and when focusing through.
In
Use – Astrophotography
Unlike
Takahashi F8s of the era, which were intended mainly for visual use on the
Solar System, even back in 1991 AP was building scopes for astrophotography
(not yet ‘imaging’) with film cameras. So unsurprisingly, though F8 is a bit
slow, the basics are good, very good.
The triplet objective
gives a better corrected field than most doublets (and some other triplets too),
even without a flattener: see the corner crop of a full frame image of the M42 region
very modest stellar distortion. Coverage at full-frame is good (maybe not
surprising given that most astrophotographers back then would have used at
least 35mm film, if not medium format). Violet bloat on bright A-O stars is
commendably low.
Like most
well-corrected apochromats with ~1m focal length, whole-Moon images are detailed,
sharp limb to limb and feature excellent contrast and give good results in
crummy seeing. If you’re used to SCTs this will surprise you!
Meanwhile,
the heavy-duty focuser has little image shift and should be well up to carrying
a CCD, though you might need the fine-focus upgrade (or an add-on electric
focuser).
M42: single
frame straight from the camera. Canon EOS 6D MkII
full frame, 30s, ISO 3200.
Left corner
crop of full frame image above: good coverage and undistorted stars.
Unprocessed
snap of the Moon is super sharp and detailed.
In
Use – Observing the Night Sky
General
Observing Notes
The focuser’s
smooth knurled knobs are a bit slippery given the heavy action and benefit from
a 2-hand twist. Focus snap is absolute.
Despite
being thirty years old, the focuser has zero image shift, with a very precise
though ‘heavy’ and slightly ‘grainy’ mechanical feel that’s the same as the Traveler’s. The only effect of lots of use is that the
central part of the travel is slightly freer than the ends and can lead to it
shifting on its own with a heavy camera or eyepiece (easily controlled with the
side-mounted tension knob).
F8+
refractors are usually unfussy when it comes to eyepieces and the 130 EDT
worked well with every eyepiece I tried, from cheap-and-basic (Meade Plossl) to
rare-and-costly (ZAO and TMB Mono’).
Note: the
130 EDT is a famous planetary telescope, so I’ll go into as much detail as I
can on its planetary performance, adding new observations as I make them over
time. Skip if you’re not interested.
Cool
Down
This is quite
a large air-spaced triplet and cooldown is quite slow, as expected. The view
isn’t great for the first 30 mins, decent after an hour, but takes even longer
to deliver its best views. This is one (perhaps the only) area where it really
trails an FS-128.
Star
Test
The star
test suffers from bad seeing more than in some other refractors that I recall,
with pulsating cells obscuring the diffraction pattern. I can’t explain this,
but when the seeing settles the star test seems near perfect.
The
Moon
The 130 EDT
delivered excellent gibbous Moon detail with bino’d
15mm Panoptics plus ~~2x barlow
in the binoviewer giving about 150x. Notable fine detail on view included the
filigree of rilles in Gassendi, the Gruithuisen domes, Plato craterlets (at
least 4), Rima Hippalus and concentric phantom craters in both Dopelmayer and Vitello.
A day later
I feasted on the rilles beyond Mare Humorum, Billy, Schickardt,
the odd ink-spill shadow of Promontarium Laplace when
the rest of Sinus Iridium is in full white glare, the striped walls of
Aristarchus.
Flare from the
lunar limb into space is among the lowest I’ve ever seen. Glancing Moonlight on
the objective viewed from focuser reveals very low levels of surface scratching
too.
As
expected, the 130 EDT is a wonderful and all-you’d-ever-need lunar scope.
Mars
On a snowy late January night with a high freezing mist, transparency
was low with only the Moon, Mars and one zenith star visible; but seeing below
the inversion was slow and stable. At 271x with a 4mm Zeiss Abbe Ortho
eyepiece, Mars was a perfect little gibbous world with some albedo markings
still visible at less than 10” across, long after the 2020 opposition.
Further nights of viewing on Mars allowed me to really stretch the 130
EDT and to do some critical eyepiece comparisons at the same time. Some
detailed notes follow if you’re interested:
A few nights later in gelid but clear and stable conditions, with Mars
at just 8.3”, I got an even better view of the Red Planet with the 130 EDT –
just perfect and sharp at 217x with a 5mm Nagler Zoom, with the dark albedo
region of Mare Cimmerium as a dark stripe centre
planet. Focus snap at this power was perfect and there was no light bleed or
softness, just a trace of red sloughing into the seeing in focus and around the
edge of the out of focus blur.
Even at a ridiculously high 361x - with a 6mm Zeiss Abbe Ortho’ in a 2x
Zeiss Abbe Barlow giving 3mm effective F.L. - the image remained sharp and with
good contrast, the albedo detail still visible.
I settled on an intermediate magnification, with 5mm eyepieces giving
217x, swapping repeatedly between a 5mm Nagler Zoom, a 5mm TMB Mono’ and a 10mm
Zeiss Abbe in the 2x barlow. I couldn’t convince
myself of any major differences between these fine planetary eyepieces, beyond differing
FOVs, but I did note that the Mono’ seemed perhaps a touch sharper and higher
contrast as it so often does.
On another night of slow, steady seeing in late winter 2021, with Mars
at 35° altitude and just 6.5” in size, I upped the power trying to see some
albedo detail. With 5mm eyepieces giving 217x, I again noticed the Monocentric
gave a slightly crisper image than the Nagler Zoom, with less red flare into
the waves of seeing. Mars at that power was a clean gibbous disk but too small
to identify albedo markings.
Going to 3mm eyepieces giving an extreme 362x, I slightly preferred the
image with a 6mm ZAO + Zeiss 2x barlow to the Nagler zoom.
Mars surprised as a fairly well defined, ochre gibbous world with Syrtis Major
centre planet and unmistakeable in steady moments.
Uranus
At just 3.4”, Uranus looked really good in the 130 EDT – one of the
very best views I’ve ever had of the planet. At 217x with the 5mm setting on a
Nagler Zoom, it was a proper, hard-edged planetary disk, not the faint and
fuzzy ‘is it a star?’ you often get. It had a pale blueish grey hue, not the green
you see in images.
Much as expected, the 130 EDT is an excellent planetary
refractor.
Deep
Sky
Despite
having old fashioned coatings with a few percent lower transmission than the
best today, the 130 EDT delivered great deep-sky views with pinpoint stars
edge-to-edge with good eyepieces.
Smaller DSOs
are an obvious use for a refractor of the 130 EDT’s skills, so I slewed over to
the Blue Snowball. It gave a great view, with the nebula looking like ... well,
an oddly blue snowball really! Job done.
The Great
Nebula in Orion indeed looks pretty great at 57x with a 19mm Panoptic: sweeping
nebula arms, a dense inner box with lots of structure and the dark lanes
clearly visible. The ‘hole’ where the hot Trapezium stars have blasted away the
nebula gases is really apparent, the Trapezium itself perfect and glittering.
Double
Stars
The Double Double and Rigel were easy splits. Something harder was
required for a scope that should revel in doubles. So
I slewed over to 36 Andromedae which has a separation of just 1.2” and was
surprised by a fairly easy split at 217x, its appearance the way the Double Double looks in a good 3” refractor at 100x. You would need
a night of really perfect seeing and a double under 1” to really push the 130
EDT’s mettle.
Buy
the 130 EDT for its lunar and planetary finesse, but stay for some great deep
sky views and truly diffraction-limited performance on doubles.
Summary
So is this
30-year-old design still a winner in the modern era? I think so. Critical
high-power performance is superb, up there with one of my all-time favourites
and its original competitor, Takahashi’s wonderful FS-128. I was reviewing an
SW 120 ED at the same time and the AP was much better for critical viewing and
not only because of the extra aperture (not a criticism of the SW which is a
great scope and a real bargain).
Is it
perfect? No. At this aperture, a more recent 130 EDT or an LZOS 130 F9, might eliminate
that last bit of spherochromatism that bleeds red light off Mars in mediocre
seeing. Cooldown – typical of a triplet – takes longer than a ~130mm doublet.
Meanwhile, the heavy focuser action and slippery knobs make a dual-speed
focuser a useful upgrade from the original.
But if you
want a full-on planetary apochromat that’s small and light enough for easy
transport and stable on small-medium mounts, the 130 EDT still has few
competitors. The cachet of the AP brand and artisanal construction give pride
of ownership too.
Like most AP products, the original 130
EDT is a little bit special despite its advanced years.
