Detailed information about this product's features  T-Max passband tuner
This Coronado SolarMax 90 is a brass and black 800mm focal length 90mm aperture f/8.9 refractor for Hydrogen-Alpha solar observing. It has a built-in sub-Ångstrom H-Alpha solar filter and a straight-through 30mm BF30 blocking filter designed for prime focus full-disk solar photography with 35mm film and large format CCD cameras, as well as visual observing. The SolarMax 90 is the largest Hydrogen-Alpha solar telescope ever to be mass-produced and is in use around the world in private observatories and professional research facilities alike. It has been optimized for very high resolution/high contrast visual and photographic imaging of activity on both the solar disk and the Sun’s limb. Prominences leaping off the edges of the solar disk, the explosive upheavals of flares on the face of the Sun, the low contrast mottling of granulation across the face of this nearest of stars, all are captured vividly by this premium-quality solar scope.
The scope’s custom-designed achromatic doublet lens uses special multi-layer antireflection coatings on all air-to-glass surfaces to optimize anti-ghosting and improve contrast. These vacuum-deposited hard coatings will provide a lifetime of detailed solar observing. The scope delivers both diffraction-limited high resolution performance and the extremely high contrast needed to see small and subtle surface details as well as the full explosive power of flares and prominences growing larger than the Earth and subsiding in real time.
The two-piece solar filter consists of a full-aperture 90mm etalon in front of the objective lens and a 30mm clear aperture blocking filter built into the scope body (rather than the smaller 15mm blocking filter built into the star diagonal of other SolarMax 90 scopes). A separate conventional 1.25" star diagonal is provided for visual observing.
A T-Max passband tuner is installed between the solar filter etalon and the objective lens. This lets you mechanically tilt the filter’s passband off the H-Alpha line to observe Doppler-shifted solar activity. This will let you determine whether Doppler-shifted features, such as flares, are moving towards you or away from you as they leap off the surface of the Sun. For more details, click on the “T-Max" icon above.
The 30mm blocking filter is built into the telescope body instead of being mounted externally as with the 15mm blocking filter versions. This lets you can mount 35mm format film and CCD imaging equipment in a straight-through configuration behind the 30mm blocking filter for prime focus photography. The 30mm clear aperture of the blocking filter portion of the H-Alpha system is matched in size to the focal length of the telescope to allow 35mm film cameras, digital single lens reflex cameras, and large chip/35mm format CCD cameras to record full disk prime focus images of the Sun. The versions of the SolarMax 90 that use a smaller 15mm blocking filter built into their star diagonals allow only very high magnification afocal imaging of small portions of the Sun’s disk through an eyepiece. The 30mm blocking filter aperture also allows you to use a Barlow in front of the SolarMax 90’s diagonal to allow the use of a binoviewer with the SolarMax.
The solar filter has a <0.7 Ångstrom passband, centered on the 6562.8 Ångstrom H-Alpha line. The sub-Ångstrom passband width gives you an ideal balance between the visibility of prominences versus disk features. The filter is thermally stable, so there is essentially no drifting off the H-Alpha line as the filter heats up during use. (Thermal stability is 0.005Å per degree centigrade.)
The SolarMax 90 has two manual drawtubes that extend for rough focusing. One is located between the telescope body and the helical focusing ring around the drawtube. This 2" drawtube should be fully extended for visual and imaging work. The helical focuser provides the appropriate final fine focusing of the second manual 1.25" drawtube that projects through the helical focuser. This second drawtube can be extended as needed to achieve focus with camera adapters and with the conventional 1.25" star diagonal (with no blocking filter) that is provided to let you use the supplied 1.25" CEMAX eyepieces for visual observing.
A full set of 1.25" Coronado CEMAX eyepieces comes standard with the SolarMax 90. These eyepieces use proprietary anti-reflection multicoatings that have been optimized for the highest possible contrast during solar viewing of subtle prominence and surface detail. The set includes 25mm (32x), 18mm (44x), and 12mm (67x) CEMAX eyepieces. Also included, to double the magnification of the supplied CEMAX eyepieces, is the Coronado CEBAR 2x 1.25" Barlow. Like the CEMAX eyepieces, its performance and coatings are optimized for solar observing.
You can also use most 1.25" eyepieces in your collection with the Coronado SolarMax 90. Any good quality 50° field Plössl will work well, as a Plössl’s contrast is generally good and its field wide and flat. For optimum solar detail, however, the Coronado CEMAX eyepieces have a small, but visible, solar viewing contrast advantage over a conventional eyepiece designed for nighttime deep space observing.
A hard carrying case is supplied as standard equipment to transport and store the SolarMax 90. The scope comes with a clamshell tube mounting ring that allows you to mount the rather heavy (23 lb.) 30" long scope on most altazimuth and equatorial astronomical mounts. Also included is a Coronado Sol Ranger Sun Finder to make it easy to center the Sun’s image in the eyepiece. The Sol Ranger connects to the SolarMax 90’s clamshell mounting ring.
The SolarMax 90 can be “double stacked" by adding a second SolarMax 90 filter and T-Max to the front of the existing filter. Double filtering improves the scope’s already outstanding <0.7 Ångstrom performance by cutting the passband to a very narrow <0.5 Ångstrom. This improves contrast on very subtle disk features. Two factory-matched “double-stacked" versions of the SolarMax 90 are available at lower prices (and with somewhat higher performance) than simply adding a separate second 90mm filter and the appropriate adapters to the scope yourself at a later date.
One is the #SM90305, which adds a factory-matched internal 60mm etalon to the standard SolarMax 90 single 90mm external etalon scope. The smaller size, and consequently lower cost, of the 60mm internal etalon keeps the price of this dual etalon scope considerably below that of adding a complete second 90mm external etalon.
The second scope, the #SM9030DS, is a true double-stack model that adds a second factory-matched external 90mm etalon to the standard SolarMax 90. The cost is almost the same as adding a second 90mm external etalon yourself separately at a later date, but the factory matching of the etalons provides higher performance than simply adding an unmatched etalon yourself later.
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