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Coronado T-Max Tuner 90mm with Tele Vue BinoVue



Coronado T-Max Tuner 90mm with Tele Vue BinoVue

by Joseph Drapell (drapell@sympatico.ca)


A small and light 90mm set up: Takahashi Sky 90, TeleVue BinoVue, and Coronado H-Alpha filter on an AZ3 Mount with a counterweight and comfortable slow motion controls. Do not forget the adjustable observing chair and an old fashioned parasol or a beach umbrella!

H-Alpha System on a Budget Mount???

It looks like it will shake crazily - but it does not! The scope (thanks for the reviews, Dave Novoselskyi) is blissfully short. Even with the Extender-Q and the Tele Vue Binovue in place, the inexpensive tripod and AZ3 mount absorb all vibrations in 1 to 1.5 sec. The slow motion controls allow me to follow objects with precision and comfort. The Coronado 90mm filter and the mounting ring are not light, but the Extender-Q with the BinoVue balances it almost perfectly at the horizon. Near the zenith, the scope has to be balanced with a counterweight. I devised a simple counterweight system using a standard ¾" shaft, which is held by a bolt right through the mounting plate.


It works, it's easy, and since I don't do astrophotography I don't need an expensive GOTO or EQ mount. The Altitude Slow Motion control determines where the counterweight should slide. As long as both Up and Down directions work with equal ease, the system is balanced. (The re-balancing is not needed much at midday, but may be needed more frequently when the sun is closer to the horizon.)

Coronado T-Max Tuner 90

From the Coronado website:

Some events on the Sun, notably active flares and coronal mass ejections (CMEs), are extremely fast moving. If such features occur on the disc of the Sun, their high velocity towards the observer results in their wavelength being Doppler shifted shorter than Ha. If the velocity is high enough, this wavelength could be outside the passband of the filter and the feature would not be observable. The T-Max allows the user to de-tune the Solarmax slightly to bring such phenomena into better visibility. The T-Max fits between the Solarmax and its adaptor plate. A simple lever movement accomplishes the tilt necessary to move the passband of the filter. Because of the filter's position at the front end of the telescope, this does not compromise the performance of the filter nor limit the Ha field of view as is the case with rear mounted filters.


The T-Max Tuner 90 is a beautifully engineered and machined black anodized ring. (The 60mm T-Max Tuner is identical, just proportionately smaller.) Rotate the small brass wheel until all solar prominences and surface details disappear, and the image brightens for clear and uncluttered views of the sunspots. This view often allows greater magnification. Rotate the brass wheel counterclockwise, and the wonderous and magnificent H-Alpha views slowly return. At first, I thought this was identical to the tunable Prom15 Blocking filter I had with my initial 60mm Coronado system. But longer acquaintance with the T-Max Tuner showed me otherwise. Some solar events the Prom15 BF does not reveal are visible and significantly enhanced by the T-Max Tuner. Patience and some experience is required, as these events do not appear every time.

The solar disk can get dark and soft, so obviously the complex filter sometimes limits usable magnification. I can go higher on the moon than on the sun in H-Alpha. This could be due to greater daytime air turbulence. Does it matter? Not to me, since I love what I see. The experience is so absorbing that it retains its fascination and mystery. On successive days, I can watch the same sunspots traversing the solar disk. As with nighttime observing, more experience helps in seeing more detail.

Comparison of 60mm AND 90 mm SolarMax

I started with the 60mm Coronado setup at first. I used the baby Tak FS60-C and the Prom 15T blocking filter, as I could not see myself spending so much more money for additional aperture. The 60mm was a beautiful setup, which I could pick up and carry outside with one hand. It gave gorgeous sharp views of all the H-Alpha elements except the chromosphere. The image was not large, of course. As a very unscientific comparison, the 60mm SolarMax produces a solar image about the size of a plum, but the 90mm's image is the size of a large cantaloupe. (To determine this I open my left eye and focus on my left hand, placed where the star diagonal is -actually the blocking filter- and simultaneously view the solar disk with my right eye, as if it were placed on my palm.)

Naturally, the image can be made much larger, but the scope, the atmosphere, and the filter itself will determine the useful magnification. The jet stream is also quite influential. For jet stream conditions, I often visit www.wunderground.com/US/Region/US/JetStream.html. Also, see the review "Planetary Eyepieces" (Peer Reviewed Article) by Daniel Mounsley (Cloudy Nights, August 2002).

The 60mm will satisfy even the most demanding observer, but if you can swing it, get the 90mm! Would I like to go to 140mm? Of course, but the weight and cost of such a system does not appeal to me.

About the Scope and Tele Vue BinoVue

Dave Novoselski has posted excellent information on both the Coronado H-Alpha filter and the Sky90. The new Sky90 is a most satisfying refractor. In my opinion, the Sky90 is a revolutionary scope design, the smallest go-anywhere OTA. The short (500mm focal length) provides the widest rich field views and least vibration in windy conditions. For lunar and planetary work, the integral Extender-Q makes the focal length very similar to the Tele Vue 102. I like to mount the Rigel Quick finder on the retractable dew shield, since I can rotate it to the most comfortable working position. The dew shield is so well constructed that whether extended or retracted no re-calibration of the Rigel finder is necessary. The scope is beautifully made, without excess or pretence, and the collimation is perfect.

Much has been written about the advantage of observing with both eyes. Since the Tele Vue Binovue must be used with the integral 2x barlow, it works fabulously on planetary, lunar, and H-Alpha views, and also on the brighter DSO. The 3-D quality of the solar disk is a "must-see" experience. The mottled surface details improve with different positionings of the solar image within the FOV, and two eyes build and complete the view. I am most satisfied with a relatively low magnification of 58x. Paired 28mm Edmund RKEs in the Tele Vue binovue (integrated 2x barlow) and with the 1.6x Extender-Q provide 58x magnification (if my math is correct). On days of exceptional seeing, one can use 20mm or even shorter eyepieces.

A Few Beefs:

Binovue: The 2x barlow in the Tele Vue BinoVue is very heavy and long. Some helical diopter adjustment on the right eye would be nice. More secure fittings would prevent the binoviewer from rotating and accidentally falling to the ground.

Coronado: could include more info with their excellent products. As for mounting the ERF front filter on the Sky90, I would prefer a threaded adapter plate to a friction fit. The little screws have to bite into the paint of my dew shield. All this is very minor in light of the H-Alpha views. My life was absolutely changed by observing and experiencing our nearest star.

About Myself

I have been observing about 3 years, observing H-Alpha solar about half of that. Thanks to Allister St. Claire of Cloudy Nights, I have been able to refine my knowledge, equipment and skills. I am a visual artist. For me, the image quality is paramount. This has led to some financial sacrifices. Yet, in the end, my wife and my 14-year-old daughter have joined me in my nighttime and daytime voyages of learning. I have never had a better hobby. What we have seen of the universe has inspired my wife's poetry and my abstract paintings. (Who says that abstract art has no meaning?) I prefer my actual and often "imperfect" views to the best astrophotography, due to the authenticity and the immediacy of the experience. Jack Newton's H-Alpha superb photographs led me to solar observing in the first place; they are great to have, but I want the actual observing even more.

Equipment Owned

In actual sequence:

  • NextStar 5, which became my teacher.
  • Tele Vue 102
  • Tak FS60-C
  • Takahashi Sky 90
  • 8" Skywatcher Dob
  • 10" Orion XT Dob
  • Portaball 12.5" (Zambuto mirror)
  • Tele Vue BinoVue.
  • Binoculars: 7x50, 10x 50, 10x70, 26x70 and finally 25x100 (which I plan to review soon).
  • For wide views, I love the small Naglers Type 5 and 6, and for the rest I use the new RKE (Edmund).
  • The last scope I acquired is a spotting scope (Pentax PF-80EDa) which I plan to review soon.

Our dark observing site is an island in Georgian Bay (Canadian side of Lake Huron). Solar system observing (planets, lunar and H-Alpha) is quite wonderful for us from a heavily insulated flat roof downtown.


Edited by Jeff Verona (09/29/02)




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