From a Jan/Feb 1995 review in Southern Sky Magazine:
"Using imported optics from the well-regarded U.S. optical manufacturer D & G Optical, Melbourne's Don Abbes has designed and produced an optical tube assembly for the Australian market and christened it "The Octagon"-a six inch F/15 achromat…….Optical evaluation was performed on a cold Melbourne night, with no wind, crystal clear skies and good seeing. First up was Jupiter, right at the zenith. I own a fine 310 (12 ½") reflector but, never have I seen so much detail so easily. The contrast was stunning. At 150x the belts stood out as razor sharp and a multitude of other surface detail was easily apparent, more than could have been drawn. Several deep sky objects were also viewed, and again the contrast was exceptional……Several doubles were also tried, and provided lovely satisfying views. Subjectively this was a fine instrument, providing great images with an acceptable amount of chromatic aberration. There was no trace of astigmatism."
"This is the sixth folded refractor I have built. (using a 5" F/15 D&G lens)
In over six decades of observing, both as an amateur and a professional
astronomer, I have only once used a 5-inch glass as good as this one....The
color correction at F/15 is excellent, I have seen more color in
semi-apochromats. The bright lunar limb appears razor sharp and colorless and
shadows at the phase terminator are jet black. Many scopes can produce quite
good steller diffraction patterns yet fall short in planetary imaging. Only
unobstructed optics of very good surface quality and with the right amount of
figuring can yield the contrast and crispness that your lens provides
when viewing the major planets. Thanks for doing things right-and at a modest
"The sketches above show a cotrast effect associated with a recent white spot/area formation. (Saturn 6" F/12 refractor) There were Don Parker's CCD images in recent (12/96) Sky & Telescope that are similar to the sketches. Based on the reports in the article, my observations were the earliest…….P.S. …I alerted Don Parker & A.L.P.O. after the 9/11/96 observation. See Sky & Telescope Dec. 1996 pg. 11…..I enjoy using the 6" very much."
"The 15" lens is absolutely superb in every way….Powers over 1000 are common when the atmosphere allows….This great lens is a testimony to the lens makers art and I will always be grateful."
"I have observed through Mr. Olivarez's 10" D & G refractor at the moon and Jupiter and the performance was superb! Thank you for your service and for producing such excellent optics!"
"I wanted to take this opportunity to formally thank you for the special effort you made in restoring our Clark lens. It is unfortunate that some time ago, circa 30 years, the lens had been "worked on" to its detriment…..The improvement has been evident to all observers bar none. Furthermore, one of our most diligent and experienced observers has rated the scope as now being perhaps better than the scope that has been our best for the last 30 years….."
"Enclosed are notes and drawings of recent observing sessions with the 8" F/12 refractor you made for me. On March 21, 1993, I had great views of Mars and Jupiter. On March 26th, with a disk diameter of only 8".11, Mars was exquisitely defined. The bright area on the limb, next to Syrtis Major, was well seen….Jupiter was also impressive. The small white spot in the enclosed Jupiter drawing looked perfectly round and stood out very well over its bright surroundings. I have now resolved Zeta Cancri (0" .62 separation) on three different nights. Also, last night, and much to my surprise, the 8" easily resolved Eta Geminorum (magnitudes 3.3 and 6.5: separation 1" .4). I had never been able to resolve this double with any telescope. Burnham's Celestial Handbook states, 'Eta Geminorum is a well-known double star, though difficult for telescopes smaller than 12 inches in aperture.' More reports to be sent soon."
"A superb view of the moon! (with newly installed D & G 10" folded refractor) The longitude of the lunar terminator was -28 degrees and the craters Plato, Copernicus, Tycho & Clavius were not far from the terminator. I could see the four craterlets in Plato with the twin craterlets resolved into two (one was smaller than the other). I also saw three craterlets on the floor of Archimedes."
"I took the opportunity of the great seeing conditions to look at the ejecta blankets of the craters Copernicus and Bullialdus. The ejecta blanket of Copernicus was beautifully presented at 195x and resolved into fine detail at this power and at 254x. There were long graceful narrow ridges emanating from Copernicus. These were overlaid with tiny craterlets, channels and rilles! The floor of Copernicus was also very detailed as were its crater walls."
"The ejects blanket of Bullialdus was also resolved into long, very narrow "ridges" that extended for long distances from the crater walls. Among these graceful long ridges were tiny craterlets and craterlet chains. Again, the sight was both impressive and beautiful!"
"For a long time I have wished to be able to see the complex ejecta blankets of both Copernicus and Bullialdus minutely resolved. Tonight, I got my wish!"…."On another night the interiors of THEOPHILUS and CYRILLUS were very well defined. The central peak of Theophilus was seen to be composed of four parts instead of the usually noted three. I was impressed to note that SACROBOSCO A has a very tiny craterlet sitting right on the rim of its wall - amazing resolution!"
"……Thank you so much for such a super job!!!"
"I want to thank you for the excellent 6" F/15 OTA that you made for me. This outstanding lens is, without any doubt, made with great dedication. Thank you, not only for the exquisite performance of this telescope, but for your patience in answering questions and for your services."
"I had a chance to use your refractor (6" F/12) under better seeing conditions last night, and it was fantastic! I'm now a believer! Because of full moon, we looked only at Jupiter, Saturn and the Moon, but all of these offered excellent contrast and showed more detail than I've seen with much larger scopes. Atmospheric conditions, clearly not the telescope, were likiting seeing at 360x, and I can't wait for a better night. The chromatic correction is excellent, really not a problem even on bright objects….."
"I was observing Saturn (8" F/12 refractor) with a single EP at 600x and the image was regularly coming into razor sharp focus. I could also use my binoviewer with my highest power EP's at 325x with the same results. I sat out there at 3:00 in the morning saying "thank you….thank you….! It was absolutely stunning! I'm sure you don't get paid enough for what you do, but if gratitude means anything…..you've got mine."
“ (11” F/15)…..As I studied the defocused image, I was amazed at how perfect it was on both sides of focus. I spent a considerable amount of time observing Mars and the moon. Detail was incredible….more than I've ever seen before. ….observing ADS 11479(HD171745) in Hercules. The double has 6.4mag & 6.7mag components with 0.70 arc separation. The 11” provided a nice wide split at 581x. Later that night I focused on another double in Pegasus, ADS 16836 (72 Peg) having two equal 6.0mag components and a separation of 0.53 arc seconds. The 11” again showed a nice clean split with tight airy discs…..my first look at Saturn with the 11” was simply wonderful. I was able to push the power to 511….”
“The images in the 8” are very sharp. Probably the sharpest I've ever seen. My 7” apo doesn't give that kind of performance. The images were so sharp I stayed up all Saturday night….The image of NGC 7006 was the best I recall ever seeing, even in a ____14” at a dark-sky location. And, of course, Swaturn was very impressive, the best I recall ever seeing it…..I set up my 10”______Newtonian a few nights earlier, and there was no comparison in performance. …your refractor has consistently given the best images of any telescope I have. Your refractor is just an excellent, beautiful, instrument. Thanks.”
“ (5” F/12)..I want to thank you for making me such a special scope…. I have never spent so much time on Saturn. More detail than I have ever seen before. Contrast on deep sky makes for stunning views. Images are surprisingly bright….This scope performs beyond its aperture and has changed the way I observe. …Thank you for making an instrument of this caliber affordable…”
“ (5” F/12)…The optics are excellent and the telescope has performed beautifully….Again, thanks for building a very fine instrument!”
“ (6” F/15)…Viewing the moon last night was amazing indeed. The contrast and sharpness of the image was excellent. Tiny craterlets were viewed that I have never seen before with any of my other instruments, of which all are larger and of excellent optical quality. I want to thank you again for this really fine lens.”
“Just wanted to quickly tell you we stole the show over the weekend with the 10” f/12 refractor. I was greatly impressed with the views your lens offered us…so was everyone else, and I mean everyone else…..”
“A few years ago I purchased a 12 ½” F/6 mirror from your company….. At star parties I continuously get remarks on how much better the images are in my scope. I am completely thrilled with the mirror you sent. Thanks so much…”
“ (6” F/12)…What a fantastic scope…. Your optical quality in the star test is excellent….. God speed on continuing the fine workmanship and business.”
“ (5” F/10)…The 5” has performed very well and I am always amazed at all the detail observable on the Martian disk. …Thanks for a great refractor.”
“ (6” F/12)……The lens resolves right down to its theoretical limit and then some. For example, the stars W Leonis and B Delphini, while not fully resolvable, are nevertheless clearly elongated. None of my larger reflactors can matchy the lens' performance on these stars…..With deep sky objects the star clusters are the real standouts. The individual star images are sharply defined points. Especially memorable are NGC 2266, NGC 6819, M92, and NGC 7789. …Thanks again for all the skill and craftsmanship that went into making it.”
“ (6” F/15)…Thank you very much for the 6” lens you made for me. …Amazing resolving power!! Especially on the moon , Saturn, etc…..”
"Many thanks for the Newtonian mirror you made for me…..Everyone in the club was impressed by the sharpness and brightness of the images, including our club president (who is 65+ and has seen his share of good and bad mirrors). ….Needless to say at this point, I am extremely pleased with this mirror. I wanted a good, serious telescope all my life (I'm now 40). You've made me very, very happy. Thanks again!"
"This past summer I did have a few chances to use my scope in good seeing, and have formed the opinion that the mirror is very nearly perfect. I want to thank you for an excellent optic…"
"….the 5" lens is excellent in every respect,….round spurious steller disks at nearly 600 power…"
"….the 5" F/12…superb definition and high contrast makes one feel as though the aperture is half again the size. Color? I've seen some APO designs with more…"
"The 5.7" F/8.4 that you reworked several years ago for _____ is performing admirably in the rebuilt Peltier Merry-Go-Round. Your firm did a great job on it!"
"Just a short note to thank you for the 5" F/12 refractor you made for me. Our staff here at the observatory has subjected it to a host of different tests, and we all agree that it is of excellent optical quality. The new push-pull cell is a nice improvement."
"..(6" F/15).It is a physically beautiful system, and preliminary tests show excellent optical quality."
"The color correction of your 10" F.15 lens is better than a ______8" F/15 semiapochromat! We tested your lens with a Zygo Interferometer. The test person said D & G really knows how to make a good lens."
"Deepest gratitude for the superb 5" F/10 lens. Many beautiful double stars have been resolved including Gamma Ceti, Eta Corona, 25 Canes, Zeta Herculis and Zeta Orionis. Thanks again for the outstanding lens and low price."
"I thought I'd see what the 6" F/15 achromat could do on the trapezium. I had tried this a couple of times before with an _____7" F/9 and always saw 5 of the 6 stars. With your 6" F/15 I saw all six stars of the trapezium."
"The 6" F/15 is performing better than I ever imagined any 6" scope was capable. Planetary images have hard sharp edges with no noticeable color! Thanks again…"
"For years I believed no American refractor could match the optical quality of my ____. Well, I was wrong! I wish D & G Optical continued success."
"A careful examination of the diffraction patterns shows textbook images inside and outside of focus. Repeated tests show no evidence of zonal defects, spherical aberration, coma or astigmatism…"
"The detail we reviewed that night with the 12" D & G objective on Saturn and Mars would startle you at the eyepiece…."
"The 8" refractor performs magnificently! Planetary and deep space viewing are superb. You've really outdone yourself with the quality of the lens. Thanks so much for a job well done."
"I've had an opportunity to observe through the 10" F/15. Saturn's rings showed bright and finite divisions: Cassini's division was very apparent as was Encke. Even though Mars was 2 months away from opposition, the detail was impressive!….thanks again for the quality you put into the 10" lens, It's the best I've ever seen!"
"The 6" F/12 refractor you built for me has been performing exceptionally well on the Moon, Mars and Jupiter, even under less than perfect seeing conditions. Sharpness and contrast are exceptional: in over thirty years of serious viewing, I have never seen so much detail on the moon, so many faint light ovals on Jupiter, or so much structure within the belts, festoons and in the GRS. I was also surprised by the virtual absence of false color, which is hardly noticeable at best focus. The mechanical construction is outstanding as well, with a very solid high-resolution focuser, and easily adjustable push-pull lens cell. Congratulations on a truly exceptional, high quality instrument!"
"Your optic lens is high quality! Clean rendering of planetary details. Thank you for first class work!"
"It has been 2 years since I bought one of your 5" refractors. I have since compared it to scopes of similar and larger aperture. So far I have found nothing to compare with its performance. The color correction on my scope is nothing short of phenomenal. There is no detectable spherical aberration, coma or astigmatism. I wanted to thank you for making such incredible views of the heavens available to me and many others through your dedication and commitment to quality."
"My 5" F/10 is an excellent performer. Star images are presented as perfectly round, airy disks even at 400x. Thank you for the excellent work at a great price."
"Well, what can I say! Star tests show the 5" lens to be perfect! Almost no color, even on the moon. Everyone who has looked through this telescope has been impressed."
"Thanks for your timely completion of the task and your businesslike commitment to your optical endeavors."
"Side by side comparison between the 5" F/10 and my ______ was "no contest"! The refractor was easily superior. I just couldn't believe there would be such a difference, but seeing is believing!"
"The 6" lens is giving excellent results. The color correction is superior to a nearby 6" lens of the same focal length but of different manufacture."
"I wanted to thank you for the excellent work you did on the mirror and the quick and friendly service which you provided. At a time when is seems amateur astronomy is having growing pains on the part of the manufacturers it was very nice to do business with a company such as yours."
"We finally got a break in the cloud cover last night long enough to get a good look at Jupiter after the collision with comet Shoemaker-Levy about 10 days ago. Through my 6" F/12 D & G refractor, the numerous dark splotches were quite dramatic and pronounced, some even said ominous looking. Several of us had set-up our telescopes, but everyone was soon lined up at the D & G where the image was clearly superior. I was certainly very pleased with the performance of my D & G refractor last night!"
"My 5" F/15 D & G objective saw first light on March 11th. I have tried it on the moon and Venus with no false colors that these old 77 years old eyes can detect. Thanks again!"
"I'm writing to tell you the pleasure I'm having using the 6" F/12 recently purchased from you. I'm very impressed with the performance of this scope in all respects. The contrast and clarity of image is superb and maintained through 350 to 450 power providing incredible lunar and planetary images. I'm now a believer that for the best images a large refractor can't be beat."
"The 5" F/10 refractor is performing beautifully. Double stars are now worth seeing. Saturn and Jupiter have never looked better."
"The 5" F/10 lens has been received and is in operation. M13 was superb. Each star seemed to resolve in competition with each other. I have found this lens system to be of excellent quality."
"You have satisfied a lifelong dream, an observatory size refractor, at a price I could afford, in less than two months. Wow!"
"Just a note to let you know I did get my 5" F/10. In the course of testing and collimating I found comet Tsuchiya-Kiuchi, tracked Castor at 768x and saw a mag 13.0 comparison star at 40 degrees altitude in cirus clouds! The improvement over my _______is amazing, both in brightness and resolution."
"First light was on Oct. 27 (6" F/12 lens) and the images were super! Thanks again for a great job."
"Just a few lines to let you know I have been able to use the 6" refractor purchased from you and the lens seems excellent. Thanks for a very good telescope at a reasonable price."
"Have had possession of the 6" F/12 telescope for about 18 months now…Besides being optically excellent, it is a real eye stopper. In looking through 6", 8" and 12 ½" telescopes of other types I get a better, sharper, crisper image in your product. The owners of the above agree!"
"My 6" F/12 D & G telescope showed the companion NGC next to M35 better than a 12 ½" reflector nearby. You are supplying a superb quality product for the money."
"Congratulating you on what is obviously an excellent objective and your production of an attractive tube assembly."
"I have recently had an opportunity to do some observing with a 10" F/8 mirror you made. It is a fabulous optic! It beats the pants off any other 10" I have ever used. Your work on that mirror went beyond science and into art."
"Just had a view last night through one of your 10" F/8 mirrors. Star tests and high power moon test show this mirror to be as close to perfect as any mirror that I have in my 30 years of experience tested."
"Thanks for all your help, the mirror was well worth the wait."
"The 10" F/6 mirror is now operational. I was utterly amazed at the power and performance of this mirror. I have truly seen less in ______…."
"I wanted to thank you for doing such a good job refiguring my 6" F/8 mirror. It received a high degree of scrutiny by my friends and I was considered by all to have an excellent figure."
"Thanks for the great job (refiguring 8" mirror). Best views of Jupiter in 10 years!"
" I want to thank you for the excellent 8" F/5 mirror you made for me. After living with a poor 8" ______ mirror for a couple of years, a sharp image is a welcome relief! Star testing of the D & G mirror showed virtually identical diffraction patterns on either side of focus. Double stars that were impossible with the old _______8" mirror are easy now. The latest to yield were E 1819 mags 7.8, 7.9 Sep. 0.8" and E 1883 mags 7.6, 7.6 Sep. 0.7"! The telescope's main use is deep sky and all I can say is everything looks brighter and sharper thanks to D & G."
"I wanted to send you a report on my observation with th 5" F/12 refractor I
purchased from you. We compared the D&G refractor to a ______7"
Maksutov-Cassegrain____ and a 10" F/6 Dobsonian. ....The two day
observational comparisons consisted of Solar, Lunar, Planetary, Deep-Sky, and
the new comet Linear, while it was in the constellation of Perseus. .....the
lens is fantastic! It compared as well and in most cases better than the
other two scopes. A very slight and I mean slight amount of color was seen
while observing Vega. Other than that one observation with Vega no other
color was seen in the Moon, Saturn, or Jupiter. .....All views were razor
sharp, bright, and crisp. We saw detail in objects we had not seen
before.....The lens is very smooth and very well corrected. Thank you for an
outstanding job and product."
"This week I received back the 2.4" _____ refractor I sent to you for
respacing, repairs and collimation. ....You did a magnificent job repairing
and collimating my scope and should be commended for your fine quality work.
....Thanks for a very professional job!"
" (refitting, etc 4" ______lens) In summary I am very satisfied with the job.
The lens went from 'obviously something wrong here' to "performs as one would
expect from a quality 4" refractor'. Thanks again - I am impressed with your
work and integrity."
"Well I now have a new telescope. Not from D&G, but they deserve the credit.
Over the summer I picked up an old home-made 5" F/15 refractor......I never
could get any image of the planets or moon into a crisp focus.....I then
called D&G.....The images are remarkably improved......Thanks again for your
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