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Orion Expanse Eyepieces. (A Consumerist Comparative Consideration of Orion's Taiwanese EXPANSE Wide Field Eyepieces in 20mm, 15mm, 9mm and 6mm)

THE GIFT (almost):

The attention-grabbing, new, Pacific Rim product is ORION's four eyepiece set targeted for "Those Extra Wide Open Celestial Spaces"-to quote its catalog byline. Colorfully dubbed, EXPANSE, similar series sets are now understood to be re-stickered in other climes as SkyWatcher. My ownership came through my good friend Wing Eng's in-store purchase of the Taiwanese ocular set (20, 15, 9 and 6mm fl). Here was an offer too good to pass up for any equipment fancier (freak?), especially at the generous complete set price (and renown liberal satisfaction policy). Such was sufficient to revive a generally depressive gift season with its share of elated "ho, ho, hos."

The frosting on the whole development has to be the simply enthralling specifications , for the price: 1) "big eye lens and great eye relief," possibly good enough for most eyeglass wearer (a claimed 13 to 17mm advertised), 2) 1 1/4 inch standard oculars, thus not requiring a 2 inch diagonal, 3) multi-coating [at least on the two outer lenses] for better contrast, and 4) most significant of all, a claimed 66 degree FOV. That later feature propels these EXPANSES into premium EP territory, at thrift store prices. Is this or is this not a recession-beating package? And are these attractive claims real?

But true to form and experience, the prompt and safe arrival of this new equipment was greeted at the outside of the house viewing pad by a dismal week of scope-rattling, blustery wind with the unfriendly, classic Pacific NW driving winter rains for un-waterproofed man or beast or bargain! "What to do," I intoned to my respected mentor friend who had in-store, hand-selected this bargain-basement set just for me with the able assistance of Rich Campbell of ORION, Cupertino. "Why, do one of those comparative studies to give some analytical and objective form to subjective impressions of those EPs' capabilities. And write it up for Cloudy Nights to enlighten others," he threw down the gauntlet. So here it is, tabular statistics and all. And not surprisingly, these studies lead to a simple conclusion--"IT'S A BUY".

One would be hard pressed to invest only $169 plus shipping for this ergonomically handsome black and chrome set of four. Would one hope otherwise to come out with comparable, on-axis resolution not infrequently in-league with some of the best? But the jewel in the crown is the quite EXPANSive, superior--and decently usable-FOV. This borders on that fabled 68 degree angle of certain, but for now unnamed premium wide-viewers. From several renown brands these other "super pan wide fields" typically cost more per unit-even used on AstroMart--than all four do new! That's exciting cosmic math and stellar economics for some under-enthralling times for the ordinary person!


The test vehicles made use of other oculars of varied makes--what was "at hand" in the eyepiece case that approximated matching focal lengths. Some exotic "glass hand grenades" were available to give a more extensive comparison, but a few desirable others did not made it in the comparison. What is here should provide a representative, useful perspective, with some specific bases for appreciation if not acquisition of the set

The classic, hi-tech, Cloudy Night-type test laboratory and instruments (tongue-in-cheek) were used; an interior home hallway of paced-off 42 foot length, one full double page of classified ads of the daily newspaper. And topping all this off is the classic target made famous by BVD's [Better Views Desired, a fine site with test comparisons of birding optics] test procedure. This called for using the miniscule engraved lines on the finest target medium of all, a crisply, government-commissioned portrait of President George. That is NOT Bush, but?Washington--aka father of our country-on a one dollar bill!

A TV Pronto, heavily tripoded, with a proven TV 2 inch mirror diagonal (enhanced? It does not says so) with TV 1 ¼" adapter became the test platform for the eyepieces (aperture 70mm, fl 480mm and f6.86).

A barely legible, garage-sale "free box" tape measure completed the assemblage of the high caliber scientific apparatus. And to proceed in classic Madison Avenue fashion, the observational-subjective impressions, when not possible to quantify or measure were lab-coat clothed with scientific-appearing % scores to impress the innocent or unsuspecting. These include the distorting pin cushion factor (curvature of field optical distortion where edge lines are bowed inward), and the gradual softening or deterioration of resolution toward the edge. At least the figures-duly noted as "guess-timations" to quantified impressions--will afford a relative basis of comparative reflection, appreciation and action. My eyeglasses' front surface measured roughly 15mm distance to my eyeball.


Scribbled on an absconded, used scratch paper fished out of the recycle bin were the following empirical notes. While originally rendered in stooped fascination, with at-times non-descript, almost illegible RX-prescription-like penciled form, this data is now formatted below legibly and hopefully logically..

20mm Test

Overview: This EXPANSE accommodated eyeglass wearers comfortably with eyecup easily rolled down. Rough measurement of eye relief was pegged at more than 17mm so the entire FOV was visible with eyeglass just off the folded eyecup. Field stop was distinct and sharply seen. In physical length, this was the second shortest of the four EPs at 2 9/16 inches tall with eyecup up; 2 3/8 inches with eyecup folded.

Eyepiece-FL, & where specified Apparent Field of View

Pincushion % (approxi-mation)

On Axis Sharpness (approx.)

Measured Total Physical Field of View width @ 42 feet; and relative fall-off in resolution by increments of 1.24 inch (ad column width)

EXPANSE 20mm, specified 66 deg. AFV



19.25 inches. Outermost 1.25" rated "good;" next inner 1.25" rated "very good+." Whole field very, very decently usable

TV Plossl 20mm, specified 50 deg. AFV



14.5 inches. Outermost 1.25" "very good." Whole field very even and very good--very usable.

ORION LV Lan-thanum 20mm, specified 50 deg. APFV



14 inches. Virtually flat, evenly sharp field. Note how narrow FOVis tradeoff to minimize any resolution fall off

Pocono Erfle 20mm, approx 60 deg+ AFV



16.4 inches. Outermost 1.25" rated "good" to "very good." Whole field very, very decently usable

TV Panoptic 19mm, specified 68 deg. AFV


95% Brite contrasty

17.75 inches. Virtually even, very sharp field, albeit with notable mild-moderate pin cushioning. Next largest FOV

Conclusion: Fine Erfle-like curved field of view, with similar drop-off in resolution toward the edge. But the still usable and decent FOV is much wider. It does best other higher-end EPs in pincushion control.

15mm Test

Overview: This EXPANSE also accommodated eyeglass wearers although somewhat tightly with easily rolled down eyecup. With eyeglass in full contact with folded eyecup, the sharp field stop can just be fully seen. Eye relief is roughly measured at 15mm (+ or - 3), probably the shorter of the four. Physically, this is also the shortest of the four at 1 7/8 inches folded, and 2 1/8 inches with the eye cup up.

Eyepiece-FL, & where specified Apparent Field View

Pincushion % (approx.)

On Axis Sharpness (approx.)

Measured Total Physical Field of View width @ 42 feet; and relative fall-off in resolution by increments of 1.24 inch (ad column width)

EXPANSE 15mm, specified 66 deg. AFV



13.8 inches. Resolution roll-off from "excellent" to "good" at 2.5" from edge, to "good(-)" on the 1.25" next to the edge. Pin cushioning more than EXPANSE 20mm. Still very decent, usable field--but shade less clean toward edges.

Meade 13.8mm SWA, specified 67 deg. AFV



12.5 inches. Resolution Erfle-like. At 3" in from edge, that drops to "good"; 2" in from edge sharpness deteriorates to "fair" going to "poor." Pin cushioning is mild.

Meade 14mm UWA, specified 84 deg AFV


95%+ lots of glass

16 inches. Resolution excellent for near flat FOV to edge. Little pin cushioning. Excellent premium EP.

Pocono Erfle 16mm, approx. 60 deg. AFV



13 inches 3 in from edge getting very good to just good; last 2 in from edge degenerating to poor, less sharp, somewhat fuzzy. Pin cushioning edging to moderate.

15mm Siebert (std), claimed 65 deg. AFV



10.3 inches Good sharpness which starts fading 2" from edge, and deteriorates to "fair" for 1.25" next to edge

TV Radian 14mm, specified 60 deg AFV



12 inches. Resolution was fine and even for whole FOV, with minimal to nil pin cushioning

TV Panoptic 15mm, specified 68 deg. AFV


95% Brite contrasty

14 inches. Virtually even, very sharp field, albeit with typical mild-moderate pin cushioning. Near same FOV

Conclusion: Another decent Erle-like performance, with parallel kind of drop-off in resolution toward the edge, but with more usable and decent resolution. Pin cushioning is mild. 3rd widest FOV and almost tied in that with famous and popular Panoptic.

9mm Test

Overview: This barlowed EXPANSE was slightly more comfortable for eyeglass wearer with 16 to 17mm ER with cup folded. Field stop was fairly distinct, but not knife sharp. Second tallest EP of the four series, probably due to the barlowed formula at 2.75 inches folded, and 3 inches up. Apparent sharpness seems positively influenced by better magnification from shorter focal length.

Eyepiece--FL, & where specified Apparent Field View

Pincushion % (approx.)

On Axis Sharpness (approx.)

Measured Total Physical Field of View width @ 42 feet; and relative fall-off in resolution by increments of 1.24 inch (ad column width)

EXPANSE 9mm, specified 66 deg. AFV

<2% flat fld (no edge barreling)


9.25 inches. Barlowed formula flattens FOV so there is near sharp resolution to the edge. Most premium-like view with no pin cushioning.

ORION Mega Vista 10.5mm (disc), specified 67 deg AFV

<2-4% flat field


10 inches. Barlowed formula also well flattened FOV so view appears sharp nearly to edge. Minimal to virtually no pin cushioning gives this the premium look.

10mm Siebert (std), specified 65 deg. AFV



8.4 inches. Surprisingly softer focus, with some fading of edge resolution so last 1.25" drops to "good(-)/fair(+)"

ORION Ultra Scan 9mm (disc), specified 77 deg AFV



10.75 inches. Not a barlowed UWA; hence not a flat FOV. 2.5" in is "good(-)," and last 1.25" to edge is just "fair (-)." Supposedly a 77 degree ultrawide by spec.

Meade 8.8mm UWA (original straight side), specified 84 deg.


90%+ lots of glass

10.5 inches. Barlowed formula with near flat FOV. Sharp to edge although view seems just dimmer. Supposedly 82 degree ultrawide and Nagler-type clone.

Meade 9mm MA, specified 40 deg. AFV


85% or less

5.8 inches. The fabled, under-appreciated EP supplied with entry level scopes, and typically readily sold off. Slight fall-off at edge with pedestrian sharpness for a surprisingly useful, albeit narrow view in fairly flat field.

ORION EPIC ED 9.5mm, specified 55 deg. AFV

<2% flat field


7.5 inches. Barlowed formula aids flat FOV. Virtually even and flat sharpness to the edge, save last 3-5%. Supposedly a slightly larger 55 degree FOV.

Conclusion: This EP's construction is right behind the premium ultrawides, with most using a barlow arrangement. This seems to produce an acceptable to decent eye relief accompanied with pleasing flat FOV (3rd widest), nearly-to-edge sharpness, and overall fine performance. Apart from a drift toward dimness with more lens elements for some, there is less to distinctively separate one EP from another (except the Meade 9mm MA or even the 10mm Siebert).

6mm Test

Overview: This EXPANSE has a FOV fully viewable by eyeglass wearers with over 17mm of ER with the eyecup folded, and no need to contact the eyeglass. Field stop was mushy and least distinct of the four. Physically, this was the tallest of the four at 2 7/8 inches folded, and 3 1/8 inches up. Barlowed formula produced a very viewable high magnification that significantly helped with the apparent sharpness.

Eyepiece-FL, & where specified Apparent Field View

Pincushion % (approx.)

On Axis Sharpness (approx.)

Measured Total Physical Field of View width @ 42 feet; and relative fall-off in resolution by increments of 1.24 inch (ad column width)

EXPANSE 6mm, specified 66 deg. AFV

Near 0;<-2% Slightest barrel@edge


6.25 inches. Barlowed formula produces fully flat FOV Even sharpness to edge with hint of barreling at edge field stop

6mm TV Nagler Zoom 3mm-6mm, specified 50 deg AFV

Minimal 10%


4.25 inches. Narrow 50 degree claimed flat FOV producing even sharpness to edge. Dimmer for lots glass

6.7mm Meade UWA, specified 84 deg. AFV

15% or more


7.75 inches ultrawide FOV sharp to the edge, with curved edge view.

At 7mm ORION Ultra Zoom 7mm -21mm, specified range 40 to 60 deg. AFV

<5% virtual flat field


6.75 inches for a surprising good, sharp view across FOV for zoom. Did not seem as dim as the TV Nagler zoom even for number of lens elements.

7mm Siebert (std), specified 65 deg. AFV



7.4 inches ultravide FOV sharp with slight softening to 1.24" edge to "good," with slight curved edge view

5mm ORION-VixenLanthanum LV, specified 45 deg. AFV


85%+(eye floaters intruding)

3.13 Inches. Like the 20mm above, a decently flat field, but seemingly less sharp for dimness. Narrow FOV is tradeoff to minimize any resolution fall off

*High magnification rendered all views exceedingly sharp down to the finer of details.

Conclusion: All satisfyingly sharp in resolution, with EXPANSE having one of wider field views.


A very useful four lens series at a very attractive price, packaging, and performance. I assume these four will be followed by one or two others to fill in the gap between the 15mm and the 9mm, and perhaps with some sibling specimens lower than 6mm fl.

At the upper end fl (20mm and 15mm) without barlowing, the performance reminds one of enhanced Erfles ranging toward Panoptic-like levels of useful correction. The two shorter fl EPs were fine flat and even FOV performers aided by the barlowed formula. Pin cushioning was practically non-existent. No ghosting or extraneous internal reflections were noted in this test environment, but these might rear their ugly heads with bright stellar or planetary objects.

The physic sizes were moderate size, bearing sufficient heft, and appropriately scaled for 1.25 inch oculars. Cosmetic blue trim line touched off the attractive appearance. Eyecups were usefully sized and pliable. Eyeglass wearers will appreciate the ease of ability to view the whole FOV with the eyecup folded

The one "fly in the ointment" are those "jelly belly" soft, thick, sticky translucent plastic lens caps. For many, that will be a total turn-off. This includes those fastidious about wanting to store their eyepieces back in their generally all-together-too-small original boxes. The caps "sticktion" will make insertion and retrieving all but the shorty 15mm from the box nearly and frustratingly impossible. Resorting to first inserting each EPs back into its zip-lock bag makes the best of a worst situation reflecting a totally ineffective packaging arrangement. So plan on buying regular "317" bottom caps and suitable top ones with all the money you will be saving on the set.


Readers being of sufficient and reasonable perceptive skepticism might wonder about the consistency in the quality of these eyepieces, since this particular set was "hand selected" in-store. Cloudy Night's author -friend, Wing Eng, whose work-route regularly takes him by ORION, Cupertino answered that very concern. By randomly looking at several other sets, he has noted these comparison results from a daytime star test. His independent, in-store, follow-up test was provided as my above report was being finalized. Quoting him

"Expanse 1.25" Eyepieces: (percentage out from the center of the field towards the field edge where distortion of the sun's reflection/artificial star off a power line insulator is noticed

Focal Length Eyepiece Set #1 Eyepiece Set #

20mm 50% 50%

15mm 65% 70%

9mm 80% 75%

6mm 80% 85%

These above figures derived from Wing Eng's own interpretative objectification of personal observations seems to show a reasonably good quality control from ORION's Taiwanese optical assemblers

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