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Unboxing and First Impressions: Ostara 102ED APO Refractor


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Hi there,

As some know, I was recently asking for advice on a recent purchase, the Ostara 102ED Premium APO Refractor package, and I was asked to post a review of the scope as few people here seemed to be using one. I haven't had a chance to get it out under the stars yet but I will do so as soon as time and weather permit. I have had a chance to get the box from the courier and unpack it properly, so get ready for some gratuitous unboxing photos! There is apparently a lot about this scope and package that is basically undocumented, even from Ostara's own promotional PDFs which are floating around. This may account for the relative lack of experience with it in the community, so lets hope this can be a start.

I will begin by saying that I have received a number of great surprises while unboxing and assembling this scope, so follow me please as I unveil a rather fine example of a cheap Chinese refractor.

The Unboxing

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The package arrived in a gigantic packing box formed from some unholy union of two other boxes, held together by FRAGILE tape and prayer.

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Inside, a box within a box and an accessories bundle. Let's start with those.

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First up, the finderscope. I've seen these marketed separately and get strong reviews for clarity and ergonomics, having one included in a package with no apparent compromise on quality would be fantastic.

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Yup.... this was still factory sealed. Picked up as bankrupt stock for a criminally low (I've since confirmed, below cost) price and still in the factory-folded moisture bags.

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Hmmm... peeling Ostara label. No surprise as these are actually KMO scopes rebadged for a half-dozen different companies. I'll have to decide if I keep these labels or just peel them off and have an anonymous ninjascope.

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Nice right-angle finder but something catches my eye....

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YES! This finder is a fully-fledged scope in its own right accepting 1.25" eyepieces with a proper fitting! Some adhesive visible down inside near the field stop but damn.... again this is a bundled piece. Nothing in the literature to suggest it either, this is a HUGE bonus as it opens it up for use with an autoguider.

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Illuminated eyepiece with helical focuser, identical to one I got with an Altair Astro finder I bought from (and ultimately returned to) Astronomia last month. These focusers do not always hold their position under the weight of the illuminator so we shall see if this is a problem for this unit also. Good news, you can see that this is coated glass.

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Multicoated optics on a finderscope.... if our fathers could see us now... the optics have a hellish red antireflective layer that is unique in my collection.

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What devilry is this? Threads, flocking and knife-edge baffles inside a finderscope?? Overengineering always welcome. When you look down this little scope it yields a view not a million miles away from my ST80; bright, clear and actually minimal CA thanks to the smaller aperture.

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Ok, now the accessory bundle.

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The diagonal; I had zero information on this upon purchase and even Ostara's website doesn't give many clues....

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...but I shouldn't have worried. This is solid and CNC-machined, identical to similar units going for around £100 at the moment. The only downside is that unlike fully machined diagonals this one has a screw-in nosepiece. It's high-grade, but can still unscrew under enough rotational stress.

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Integrated machined 1.25" adapter with brass compression rings....

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....and what's this here? 99% reflectivity? They've essentially thrown in a premium dielectric diagonal like it's nothing and failed to tell anyone?? This is turning into a litany of desire...

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Now the eyepiece, my second two-inch. Looks fairly normal... SWA 70deg is nice but not going to set the world on fire, has a safety ridge.

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Nice engraving and knurled grip, feels extremely solid and reassuring, no rattle or wobble.

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Gorgeous fully-multicoated optics here.

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Clean as a whistle, fully blackened lens edges, baffling, flocking, threaded for filter use. This one is up there with the £60+ class.

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Nondescript illuminator, standard CNC machined aluminium. This one fortunately works properly out of the box (even has a battery in it) unlike the one I was forced to return with my old RA Finder.

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Tube rings for the finder.... boring but high quality CNC machined.

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Now let's see what Santa brought....

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This is advertised as a 'flight case' and I can certainly attest to its strength and durability, it weighs an absolute TON and comes with key-locking latches so you can send it through baggage claim without anyone getting sticky fingers. These are upwards of £150 wherever you go to buy them.

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Plenty of spare surrounding foam to carve out accessory gaps; the foam actually flows all the way around the tube, it isn't hollow-floor like some of the cheaper laser-cutting services out there.

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You handsome devil.

[continued]

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Superb craftsmanship here, I have to take my hat off to KMO. The in-house Crayford is butter-smooth but reassuringly tight and stable when focused, and the top locking screw allows the whole assembly to rotate smoothly when loosened. Perfect in every way for holding heavy astrophotography rigs, it even has three tension screws for the 2" compression ring. An interesting fact here is that you get a 1.25" ring on the main focuser and another one on the diagonal, so lots of flexibility.

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Here it is sitting next to my C9.25 and a SkyWatcher 1145P Newtonian. It fits right in, between my big scope and my little ones, although at f/7 it is notably longer than the f/5 fast fracs on the market.

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As an Apochromatic Refractor, it passes the standard Sofa Test with ease.

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The doublet objective lens; not exactly sure which ED glass is in use, but I suspect FPL-51 or equivalent rather than high-grade Fluorite you see on TeleVues. I anticipate some technical CA. The coatings on this scope are an unusual reddish-brown colour I've never seen before.

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The antireflective coatings doing their job well; Ostara consider this a whole system FMC. The dew shield extends quite significantly, around 6", with a smooth, firm action and doesn't move at all unless made to do so and reaches full extension with a recognisable thunk.

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A neat little touch, the push-fit lens cap is lined with little felt patches so the paint stays intact. The screw-on aluminium cap for my ST80 is much higher grade but this one doesn't take endless irritating rotations to remove.

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Another cheap branding label, likely to remove these. Despite appearances the paintwork is somewhat iridescent, under sunlight it looks absolutely stunning as an instrument and seems to repel fingerprints unlike the Equinox series and their piano black.

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The rear assembly is solid as a rock, precisely machined with no rattle and no hollow spaces. The Crayford is dual-speed 11:1 and the bar is completely immobile under pressure. Both focus ratios are smooth but secure, and knocking the knob results in zero focus shift. You can only focus this scope if you fully intend to do so. There's a little resistance at full retraction but this is easing as I redistribute the grease.

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The scope can be held in one hand quite easily at around 4.5kg, but retains the expensive-feeling heft of a premium refractor.

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And there it all is. All in all a spectacular deal, not sure if I'd be willing to pay the full £1,500 RRP they ask so I'll have to get it out under the stars to confirm. If you're moving up from amateur to semi-professional astronomy this will provide you with a raft of easily-transferable top-drawer accessories that you can throw into any of your other setups easily.

Thoughts and Impressions

First thoughts on this scope.... wow. The package notwithstanding, the fittings and mechanical excellence here are bested only by the top-end semi-legendary APOs that cost more than a car, ten times the price of this package. Almost every tiny little touch and feature has been accounted for and included, some of which like rotating focuser assemblies and triple-fixing brass compression rings are often quoted among the reasons to start investing in premium OTAs.

Handling, assembling and mounting this scope is a breeze, it fits the bill of grab-and-go although the weight will demand a proper mount, a Vixen Porta at a minimum. Once you start adding 2" accessories the total weight goes up fast, so for light work it may be best sticking to small but high quality 1.25" accessories.

Another telling example is that despite my ownership of a 9.25" SCT that sits on an HEQ-5 mount, this is the first tube I've unwrapped to elicit 'Ooohs' and 'Aaahs' from my nearest and dearest.... the sentiment seems to be "We can tell it's expensive but we can't tell why". I faced stern questioning when the SCT came home, but this scope has gained immediate domestic acceptance based on signature looks alone :)

The quality of the APO itself remains to be seen due to the new scope curse, I'll post a Ronchigram image and some star testing results once Vega creeps out from behind the clouds!

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Many of us, at the past, would never imagine to wish an istrument like this.....

Thanks to Chinese reverse engineering, we can buy and enjoy tons of Newtonian inches, excellent focusers, premium objectives etc.

I am worring about American and European equipment manufactures future, but i still love my (sold) equinox 120.

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Nice looking scope. It looks identical to ones with Orion (USA) and a few other brand names on them which I believe use an FPL-51 (or equivalent) ED element in the objective lens.

I have a Japanese made Vixed 102mm ED which is f/6.5. It's amazing the level of CA control that can be achieved with a relatively fast, inexpensive ED doublet these days :smiley:

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Nice looking scope. It looks identical to ones with Orion (USA) and a few other brand names on them which I believe use an FPL-51 (or equivalent) ED element in the objective lens.

My thoughts also; I am not expecting FPL-53 in this, likely -51 or Hoya FCD10. I've done some daylight tests and there is the tiniest ghost of CA visible on tree branches against a bright white (clouded :mad: ) sky, but it's something I have to know to look for and physically move my eye around to catch a glimpse of. When my CA-hunting technique is the same one I use to find dim galaxies, I know it's well under control :grin:. Another interesting fact is, the CA 'spectrum' is not what I am used to with my ST80 which for all that I love it, has colour like you wouldn't believe. The glimmer of colour in the Ostara, when I catch it, it more sharp violet and more grubby dark red; it seems that the CA is limited to the absolute outer edges of the visual spectrum, it's sort of like the effect of those 'fringe killer' or 'UHC' filters when I put them in the cheap refractor but of course, the main image is free of a filtered colour cast.

I have a Japanese made Vixed 102mm ED which is f/6.5. It's amazing the level of CA control that can be achieved with a relatively fast, inexpensive ED doublet these days :smiley:

I envy your ownership of a Vixen but sadly just too rich for my blood. My girlfriend has kindly accepted this scope into the family on the basis of being all shiny and pretty, but if I'd paid RRP (or Vixen prices...) I think I'd be in the doghouse :rolleyes:

These new ED doublets are astonishing as you say. With modern CCDs and processing available to everyone, we can eliminate the remaining minor aberrations that non-research grade scopes are bound to have, and just get on with enjoying the sky rather than constantly fretting about the equipment.

Speaking of equipment, first clear night I get I'll post a Ronchigram of this scope, I'd love to have some experienced eyes looking at the optical performance :smiley:

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At the general qualiy and cost that scopes like these are being made for coming from China the UK retailers are going to have to start stocking and supplying them the same as the more recognised brands. Otherwise they will miss the opening in the market.

Who did you purchase the scope from?

No mention of customs etc so I assume a UK supplier.

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At the general qualiy and cost that scopes like these are being made for coming from China the UK retailers are going to have to start stocking and supplying them the same as the more recognised brands. Otherwise they will miss the opening in the market.

There is some truth to this, although the guarantees offered by the distant Chinese factories are not nearly as accommodating as those found here in Europe. The dealer is expected to eat all the transportation costs in both directions, which certainly isn't a good deal for a small astro retailer turning the minor profit margin that this industry provides for. As long as the Eastern suppliers don't get too greedy and start trying to jack the prices near those of TeleVue and the like, I can see a market for these scopes.

Who did you purchase the scope from?

No mention of customs etc so I assume a UK supplier.

Bankrupt stock. Apparently a small bazaar-type multi-interest store went out of business and an enterprising individual picked up a pair. Both went on eBay for ~£500.

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An excellent review Stratis,

I was so absorbed into the detail of your review, I really enjoyed it! Hopefully the clouds clear we'll get to see a decent review on it's performance, Seeing the quality on there it looks really good!

For myself I bought a TS 115 Triplet F7 Refractor paid around 1700 euros, I have to agree that the Engineering quality is quite superb, it looks very similar to your scope, the coatings on my are a lot different than yours, however it's delievered fantastic images and does the job for me, I would like to afford a Triplet ED Refractor of the similar size like your Taks. Borgs and Televues, but they so so expensive I could buy a sports car for kind of money! I would expect sheer quality to pay that kinda of money, But these cheaper alternatives coming out might not be same level of quality as these ultimate performers but they do come extremely close, And sometimes I feel that buying branded scope, Yeah point taken it's excellent, but because it's a Televue, a Tak, or a Borg, I feel that you're just paying for name. Other's might disagree, but I don't have budget of around £3000 to splash out on a Triplet ED scope!!!

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...I envy your ownership of a Vixen but sadly just too rich for my blood. My girlfriend has kindly accepted this scope into the family on the basis of being all shiny and pretty, but if I'd paid RRP (or Vixen prices...) I think I'd be in the doghouse :rolleyes:....

If I'd paid the new price of the Vixen, I'd have been in the doghouse too !

Thank goodness for used equipment :smiley:

I believe one of our members, Mark at Beaufort, has a very similar, if not identical, scope to yours which I've had a look through on a couple of occasions. I seem to recall the performance being virtually identical to my Vixen, ie: very nice :smiley:

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I loved the report. Kept me smiling for quite a while. I really believe the 100mm class of scope is, on balance, around the best overall size. I regretted buying an 80mm class scope quite quickly.

Just one thing though. I can't find any reference to the scope being an APO other than your report. Is it an APO ?

Dave.

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Just one thing though. I can't find any reference to the scope being an APO other than your report. Is it an APO ?

Well, this is a difficult question.

There is no formal definition of what makes an APO, some manufacturers have been using the term, some are using the term 'semi-APO', others are avoiding the definition completely and sticking with the better-defined 'Enhanced Dispersion' label.

Ernst Abbe defined an apochromatic optical system as;

"...an objective that brings three widely spaced wavelengths to the same focus and is corrected for spherical aberration and coma for two widely separated wavelengths. Additionally, one of the crossing points for color correction should also coincide with one of the crossing points for spherical aberration and coma. Furthermore, that crossing point should lie as close as possible to the Fraunhofer yellow, e-line."

There are no apochromats on the market for any price that fit Abbe's criteria; only the very highest-grade scientific microscopes attain this height.

Thomas M. Back (of TMB Optical fame) knocked out a looser definition criteria;

· Peak Strehl at 550 nm of >0.95

· Diffraction limited (>0.8) over the entire C (red) to F (blue) range

· Has at most 1/4 wave spherical error over the C–F range and achieves at least 1/2 wave correction of the violet (g) wavelength.

Even this definition is rarely achieved, only FPL-53 of the finest figuring and Fluorite systems can hit this mark. None of the 'ED' scopes from China meet this definition, neither do the Equinox range which are considered APO and have legions of loyal fans. Even using FPL-53, the most minor miscollimation of the doublet lenses will reintroduce CA with a vengeance, lending weight to the statement that a fine FPL-51 system will beat a misfigured FPL-53. User testimonials of Chinese-made ED scopes (below the Esprit Pro series) overwhelmingly admit to the presence of minimal colour fringing as a technical fact but not an operationally relevant one.

The first set of daylight and twilight tests of this scope seem to suggest a few things;

  • Chromatic Aberation does exist on bright fringes, but is subjectively only a fifth to an eighth of what I see in an f/6 achromat with a 10mm EP
  • The CA spectrum is strongly attenuated to the upper violet and low red ranges, offering strong contrast on all terrestrial objects available.
  • The optics seem entirely free of zoning, astigmatism or spherical aberations; this is the highest quality lens I've ever used (Ostara claim they are hand-finished in the UK)

From daylight I would say that no, this is not an 'APO' by any formalised definition; as a corollary I would say that this has zero impact on image quality for me, there may be more sensitive individuals out there who cannot bear even the brownish red and barely-visible hard-violet you'll see through this scope but I must stress it is as minimal as it could be before disappearing entirely; I don't think my CCD imager would even pick it up.

This scope pretty much hits the mid-point of every scale refractors are judged on; mid-aperture, mid-focal length, mid-weight, mid-CA, mid-price. It's not a 'true' APO but it beats the 'semi-APO' I've looked through quite handily. It offers an image similar to an f/14 achromat but maintains a length and weight between a short tube and a yard cannon. The price is above what you'd pay for a nice 152mm achromat from the same factory, but way way below a 102mm triplet APO that linger north of two thousand.

I make it a point to be as critical of my scopes as I can be, there's nothing worse than first-rush cheerleading for what is fundamentally a scientific instrument; so far the only thing that's annoyed me about this is that it isn't quite light enough to fit on a SkyWatcher AZ GOTO mount so I'll probably need to use the HEQ-5. Optically it's like falling through the sky on tonight's sunset and showed me the details on a tower block's satellite dish from over a mile away; I can't fault it without being unnecessarily picky.

Star tests to follow :)

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Interestingly, my Vixen ED102 F/6.5 and Skywatcher ED120 F/7.5 deliver pretty much the same in terms of CA correction. The former is believed (Vixen never confirmed it) to use an FPL-51 ED element and the latter uses FPL-53.

I see a tiny "splash" of CA around the brightest stars and a bit around Venus. At focus I see no obvious CA around the lunar limb although it appears as a thin fringe of either pale green or violet either side of focus. Luckily I prefer to view objects at focus !

Both the scopes seem well corrected for spherical aberration as far as I can see from their star tests under good seeing conditions.

From what I've read there are lots of factors apart from the ED glass used that contribute to the quality or otherwise of CA control and other aberrations. The choice of glass used for the mating element, the quality of figure and polish of the lens elements and the accuracy with which they are held within the objective cell being major factors.

It used to be thought that the Chinese could not make a decent ED doublet or triplet apochromat but I think there are enough examples around now to thoroughly disprove that :smiley:

It looks a really nice scope Stratis and I hope you get some great views with it :smiley:

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