Review of Stellarvue 102EDT
by Charter Member Steven J. Mack, Esq.

Background

I am 39 years old, and have been interested in astronomy most of my life. Unfortunately, I only owned the “gasp” department store type telescopes for the most part. I did however have very good binoculars (Nikon) that I used much more frequently since I was disappointed by the views in the inexpensive telescopes. A few years ago I decided that I wanted a “serious” telescope and began my research. I wanted a scope that would fit the needs of my interests, including visual observing and photographic endeavors. I am not big on adding reducers and flatteners so I wanted to keep such items to a minimum. I tend to overanalyze to the point that sometimes something new comes out while I am still making my decision. I have a technical background in computers; however, I am a reformed computeraholic (less than 14 hours a day...) and now just practice law. I have owned various inexpensive refractors, including a Swift MarkII 60mm spotting scope which I still have and is probably as old as I am. More recently, I have owned and sold a 4.5 inch reflector on an Eq mount and then a Stellarvue 80mmf9.4 achromat. I currently own three telescopes; the SVEDT, the Swift and an 80mmf9 achromat.

Build Of Scope

I have had and used this scope now for approximately six months and it is truly an amazing, dynamic telescope. This scope is similar to other "Semi-Apo" telescopes in terms type of glass (ED), color correction and lack of any aberrations. The owner of Stellarvue, Vic Maris, won't say it, and refuses to use the term (“Semi-Apo”), since it is really a marketing tool in his opinion (and mine too for that matter). Stellarvue emphasizes that this scope is an achromat not an apochromat. The term “Semi-Apo” is a bit nebulous, but suffice to say these types of scopes are typically scopes that contain at least one element of ED type Glass, and are not quite colorless (color fringing). Because most people can relate to that term, and this scope falls into that category, for the purposes of this review I will use it.

Everything fits tightly and smoothly and feels solid.

The focuser is made by JMI (DX1) adapted specifically for Stellarvue and is a Crayford type focuser that is fully adjustable and smooth (see photo). The dual speed, rotating focuser is really what sets this scope apart from other similar scopes, it is that good. The rotating focuser allows you to position the EP to a comfortable viewing position no matter the angle of the scope. Unfortunately, that is one design that did not last, the focuser no longer rotates. Apparently, SV found that some of the focusers went out of alignment when people (usually not the owners) would grab the JMI knob when rotating it and ruin the focuser.

The two speed focuser is buttery smooth. The left side allows for general focusing and the right side allows for the minutest adjustments. The nicety of the two speed focuser, especially for photography cannot be overemphasized. According to JMI’s website, the dual speed is: 0.075" and 0.39" of Travel per Revolution of Knob, that’s about a 5.2 to one ratio. The focuser has a baffle in it as well, which I would recommend removal of when you take pictures (pops in and out rather easily) as it does vignette the photo if you shoot from Prime focus (see photos). The vignette though is not a total block, as you still get stars in the vignetted area; it is just a reduced exposure (see photo of Pleiades). If you shoot from the eyepiece, I saw no vignetting (see photo of Sun and Moon). This particular issue never bothered me, because it was very easy to remove and replace the baffle, but SV is always improving their designs, and the EDT is no exception. SV has since changed the design of the baffles. The new wider baffle system cannot be removed, but it no longer causes any photo issues as the two baffles in this new system are wider, fitted into the tube and pressed into place.

Photos by Steven Mack, unless specifically designated.

Pleiades, SV102EDT, 1 hour, Fuji SuperHQ 100.

The sliding dew shield is a nice feature for portability and is tight and smooth, feeling like it locks into place. The paint finish is smooth and glossy with the tube painted white and the focuser and dew shield painted black, which appears to be baked on.

The one thing that I do not like, and have complained about, is the lens cap. It is ill fitting and not near the same quality as the rest of the scope. To SV's credit, according to the owner, they are in the process of redesigning the cap and will provide all past owners with the new cap when it is available for a nominal fee (around $15.00). *** In the process of writing this review, I have received the new lens cap. It is machined out a single piece of metal and fits tightly in the end of the dew shield. The black finish matches the scope perfectly. It has a very nice acrylic SV logo in the center. The older cap was bulky and added almost an inch to the length for storage and additional width; this one takes virtually no extra space and is definitely what should have been provided with this scope to begin with (see photos).

The scope is a closely spaced ED triplet (All three lenses are in the front of the scope next to each other), hence the name EDT. The primary element is an ED element (true ED glass, not FK5 which is considered to be “fake ED” by some manufacturers - The owner has stated publicly that the lens was his own design and melt) the other elements are unknown as the owner keeps the design a guarded secret. I have no problem with this since protection of such secrets assist in quality control and combating copycats, but it sure creates quite a stir in the amateur community!

As stated above, the scope is a triplet design and the system is designed to be flat overall. The triplet lens system allows better zonal control and a flatter, better corrected field. Although the scope is an incredible visual scope, where it shines is photographically. This scope has a very sharp, bright and a flat field with no aberrations, perfect for astrophotography. This is an interesting design given that other scopes require the use of an external field flattener. One of my goals was not to spend more money on add on devices. Most triplets that are designed this way are apochromatic, which is why this scope is so unique!

The EDT is very short and portable. At F6.1 (621mm) it is only 2o inches long and weighs approximately 9 pounds, which makes it airline portable. For those fans of the “more aperture is better but I still want something portable” club, this fits the bill. Unfortunately, the airline portable cases that SV sells do not fit the EDT, so you have to find your own case. I converted a lightweight plastic toolbox by adding foam and cutting it to fit.

Through The Scope

The view through the lens is tack sharp edge to edge and incredibly flat though all of my eye pieces (EP’s). The EP’s I used for testing day and night were the Tak 5mm LE (124x, .419 tfov, .8 exit pupil), an inexpensive SV 9mm Plossl (69x, .726 tfov, 1.5 exit pupil), 16mmT2 Nagler (39x, 2.116 tfov, 2.6 exit pupil) (truly one of the great “spacewalk” EP’s), 20mm Orion Ultrascopic (31x, 1.677 tfov, 3.3 exit pupil) (an incredible EP for the money) and a very nice wide field SV 32mm Plossl (19x, 2.581 tfov, 5.3 exit pupil).

No astigmatism whatsoever in my sample, and the star test, to me, appears to be absolutely beautiful. Please see Thomas Backs article, A Star Test Primer: . Concentric rings clear as a bell, both sides of focus and evenly lit. I am no expert and certainly one can read various publications on star testing, including the leading book by Harold Richard Suiter, “Star Testing Astronomical Telescopes”. The star test is done by defocusing and over-focusing on a bright star ever so slightly. Generally speaking, you should see concentric rings evenly lit with no aberrations in the rings. I have looked at star tests through several scopes including several Stellarvue models (apo and achro), as well as Tele Vue, Borg, Meade and others, and found that the Stellarvue and Tele Vue are certainly two of the most consistent. I have not had the opportunity to look through a TMB or an AP scope, but at the time, I did not consider them as a part of the limited line of telescopes I was interested in, given my narrow requirements and price range.

On a scale of 1 to 10, I would rate the lens a “9”. The only reason I rate the lens a "9" instead of a "10" is because I am comparing this particular lens against all lenses that I have looked through, and, frankly, as has been stated ad nausem, this is not an apo. An apo would be a "10", but it is pretty close in terms of contrast and lack of aberrations. I know that differences exist between apochromatic lenses as well, but I am lumping apo lenses into the 10 category just so you get the idea.

I did a comparison of similar and not so similar scopes prior to my purchase. I had the opportunity to look through other "Semi-Apos", other achromats and apochromats for three straight days comparing them during the day and at night, although not "side by side", within a few yards of each other at RTMC (with the exception of an 85mmf8.8 apo which was side by side). I compared Tv102, Pronto, Various BORG models, Meade, a Megrez and a Stellarvue 85L apo. I found that for the incorporated features (such as the flat field) and build quality that I wanted, as well as my budget; this scope fit the bill perfectly. In the evening we had the moon. Unfortunately, during RTMC this last year (2002), we had a very bright moon and some haze during the evenings. I compared the moon, contrast and detail, as well as color on the limb. The only other items that could be seen due to the moon, was Vega and a few other miscellaneous stars, but I did see some nice wide field views. Again, the images were sharp, contrasty and flat. The stars are pinpoint with a nice black background.

When focusing on an object the two speed JMI focuser is fantastic; Green one side of focus, purple on the other. When you get all or most of the color out (depending on the object), you are in focus. No colors are present except on the brightest objects, and even then it is minimal and can almost be focused out. I do expect to see some color on bright objects given the speed of this lens (f6.1) and the non-apo design. Interestingly, I previously owned a SV 80mmf9.4 achromat. When I purchased the EDT, Mr. Maris told me to expect more color in the EDT, given the size of the lens (102mm) and the Speed (f6.1). He was right (but not by much); however, I preferred the extra aperture (4 inch vs. 3 inch), the speed (f6.1 v. 9.4) for taking pictures, and the incredible flat wide field, its portability (airline carry-on) not to mention the focuser. When you compare apples to apples, it’s hard to beat the price with all the features, build quality, finish and quality optics.

This is not an apo, nor did I expect it to be, but it does not carry the 4 inch apo price either. The scope retailed for $1695.00. The cost of the focuser alone on the EDT is $400 - $500, and if you deduct that from the price, it puts it in a similar price range of standard 4 inch achromats (non-ED type) without field flatteners (another $200 - $300.00). Of course I am comparing new to new pricing, not what the used market may bear.

I saw that another reviewer mentioned that he saw purple haze during the day as compared to an apo. I only mention this because, while I do not dispute what he saw, I am sure he is reporting what he did see, but I can only say that after comparing this scope with apochromatic scopes for three days, I did not see the same. I had the Stellarvue 85mmf8.8 apo (which has absolutely no color)that I compared side by side for three days, and several that I was able to look through just a few yards away. The comparison was made by looking at the same spot with similar magnification. The first target was a bright white tent against the light blue sky, and the second target was bright green leaves against the light blue sky. I saw no purple haze whatsoever, however, through the EDT you could see some color (purple or green depending on which side of focus) on the edge of the white against the blue, but again, with the focuser, it could almost be focused out to a point where it was not distracting. The apo showed no color whatsoever on any object. As I have previously stated, the color correction for the EDT is very similar to other non-apo ED scopes, albeit a little less thanks to the focuser. I used the same EP’s as I described previously.

The Company

The last thing that I wanted to discuss is the company. When I first ordered my scope I had a problem with the delivery notification. I was a bit miffed, but the problem was remedied immediately and cordially by the owner of the company, Vic Maris.

In my experience, this is but a sliver of the customer service that you can expect. I have been able to reach Mr. Maris by phone or email, and the answers to my questions have come fast and friendly.

I was able to place my name on the waiting list without any money down (I had to give my credit card number, but it was not charged until the scope was shipped), but even after I received the scope if I was dissatisfied for any reason, Stellarvue has a generous 30 day money back guarantee.

Final Words

Now the sad note: This scope was discontinued by Stellarvue due to the cost of the ED glass. It rose so much that the company discontinued this model because they would have to sell it for too much money, taking it out of the realm of being competitively priced. As it sits, the new price is about 25% less expensive than a new Tele Vue 102 OTA (which is an apo); however, if you consider the focuser and field flatness you can bump that difference up to about 40% or 50%. Unfortunately, if the price were to go up, the scope would no longer fit in its nitch. Although SV has ceased offering the telescope, according to SV they have enough lens sets on hand to make 25 more by special order (a total of 100), then they are done.

If what I described is what you are looking for and if you can find one, grab it, you won't be disappointed. Sorry, I have no intention of selling mine!

The Following Pictures by Stephen Pitt, , show the wide flat field of the telescope, as well as photographic prowess of this scope.

Above, the Rosette Nebula through an SV102 EDT at f6.1 for forty-five minutes using Fuji Provia 400F pushed 2-stops. Photo by Stephen Pitt.

Below, the Omega Nebula, M17. Acquisition: SV 102 EDT f6.1, Fuji Provia 400f +2 for 60 minutes. Photo by Stephen Pitt.