SolarMax II 90 3.5" F/8.8 solar telescope with 30mm blocking filter

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This Coronado SolarMax II 90 solar telescope is designed to do much more for you than merely show you sunspots, as an ordinary white light solar filter can. Its Hydrogen-Alpha solar filter reveals features of the Sun that are normally hidden by the fierce glare of this nearest of stars – features that change constantly as you watch. The high resolution 90mm aperture of the SolarMax II 90 reveals intricate and subtle details in the ever-changing tapestry of prominences leaping off the edges of the solar disk, the explosive upheavals of flares on the Sun’s disk, and the subtle mottling of granulation across the face of the Sun.

The Coronado SolarMax II 90 solar telescope by Meade starts with a brass and black 800mm focal length 90mm aperture f/8.8 refractor. It has been custom-built to provide high definition Hydrogen-Alpha solar feature views using Coronado’s unique RichView tuning Hydrogen-Alpha solar filter.

The two-piece solar filter consists of a tunable sub-aperture etalon in the body of the scope and a large 30mm clear aperture blocking filter in the scope’s 1.25” star diagonal. 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 of prominence and surface detail alike. The filter is thermally stable, so there is no drifting off the H-Alpha line as the filter heats up during use. The 30mm clear aperture of the blocking filter portion of H-alpha system built into the star diagonal is designed to provide full disk single eyepiece views of the Sun for single eyepiece visual use, binoviewing, and imaging with large 35mm-equivalent chip size DSLR and CCD cameras. There is also a somewhat more economical 15mm blocking filter version of this scope designed for imagers who do not need quite as wide an illuminated field for use with medium (APS-C) chip size DSLR or CCD cameras.

The new and revolutionary RichView tuning assembly of the Meade Coronado SolarMax II 90 represents a breakthrough in solar observing. This patented system allows very precise direct tuning of the primary filter etalon by a lever in the side of the scope body to shift the filter’s passband off the H-Alpha line. This lets you observe Doppler-shifted solar activity to 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. No other commercially available H-Alpha telescope can provide the tuning range and accuracy of the SolarMax II 90. Now you can tune for the highest contrast views of active regions, flares, filaments, and other surface detail, or quickly and easily re-tune for prominences on the solar limb.

The SolarMax II 90 has a manual 1.25” drawtube that extends for rough focusing. A helical focusing ring around the drawtube then provides the appropriate final fine focusing. This method provides enough back focus to allow both visual observing and imaging.

A set of Coronado Cemax 1.25” eyepiece is standard equipment, providing magnifications of 32x with a 1.62° field, 44x with a 1.18° field, and 67x with a 0.78° field. You can use most 1.25” eyepieces with the Coronado SolarMax II 90, as well. Any good quality 50° field Plössls will work well, as their contrast is generally good and their fields are wide and flat. For still higher power views, consider adding the Coronado Cemax 2x Barlow to your system. Like the Cemax eyepieces, its performance and coatings are optimized for solar observing.

A hard carrying case is standard equipment to transport and store the 90mm Coronado SolarMax II. A clamshell mounting ring is provided to let you mount the 30” long 23 lb. SolarMax II 90 telescope on a suitably-sturdy astronomical mount by adding an optional dovetail mounting plate. The supplied Coronado Sol Ranger Sun Finder makes it easy to center the Sun’s image in the eyepiece. The Sol Ranger connects to the supplied SolarMax II 90 clamshell scope mounting ring as can be seen in the image above.

A “double stack” version of the SolarMax II 90 (#SMT90DS-30) is also available that adds a second tunable SolarMax II filter to the front of the scope. Double-stacking the filters improves the scope’s already outstanding resolution and contrast by cutting the passband from <0.7 Ångstrom to a very narrow <0.5 Ångstrom. This improves the contrast and visibility of subtle disk features, although it slightly reduces the brightness of prominences.

Focal Length:
This is the length of the effective optical path of a telescopeor eyepiece (the distance from the main mirror or lens where the lightis gathered to the point where the prime focus image is formed). Focallength is typically expressed in millimeters.

The longer the focallength, the higher the magnification and the narrower the field of viewwith any given eyepiece. The shorter the focal length, the lower themagnification and the wider the field of view with the same eyepiece.

Focal Ratio:
This is the ‘speed’ of a telescope’s optics, found by dividing the focal length by the aperture. The smaller the f/number, the lower the magnification, the wider the field, and the brighter the image with any given eyepiece or camera.

Fast f/4 to f/5 focal ratios are generally best for lower power wide field observing and deep space photography. Slow f/11 to f/15 focal ratios are usually better suited to higher power lunar, planetary, and binary star observing and high power photography. Medium f/6 to f/10 focal ratios work well with either.

An f/5 system can photograph a nebula or other faint extended deep space object in one-fourth the time of an f/10 system, but the image will be only one-half as large. Point sources, such as stars, are recorded based on the aperture, however, rather than the focal ratio – so that the larger the aperture, the fainter the star you can see or photograph, no matter what the focal ratio.

This is the ability of a telescope to separate closely-spaced binary stars into two distinct objects, measured in seconds of arc. One arc second equals 1/3600th of a degree and is about the width of a 25-cent coin at a distance of three miles! In essence, resolution is a measure of how much detail a telescope can reveal. The resolution values on our website are derived using the Dawes’ limit formula.

Dawes’ limit only applies to point sources of light (stars). Smaller separations can be resolved in extended objects, such as the planets. For example, Cassini’s Division in the rings of Saturn (0.5 arc seconds across), was discovered using a 2.5” telescope – which has a Dawes’ limit of 1.8 arc seconds!

The ability of a telescope to resolve to Dawes’ limit is usually much more affected by seeing conditions, by the difference in brightness between the binary star components, and by the observer’s visual acuity, than it is by the optical quality of the telescope.

1.29 arc seconds
This is the diameter of the light-gathering main mirror or objective lens of a telescope. In general, the larger the aperture, the better the resolution and the fainter the objects you can see.
The weight of this product.
23 lbs.
1 year
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Visual Accessories
Barlow Lenses (1)
1.25" 2X CEMAX Barlow enhanced for solar viewing
by Coronado Instruments
  • 90mm f/8.8 optical tube, <0.7 Ångstrom SolarMax II filter, RichView internal tilt-tuning, combined 30mm aperture BF30 blocking filter and 1.25” star diagonal, Cemax 1.25” eyepiece set, lens cover, clamshell mounting ring, Sol Ranger finder, hard case.
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Coronado Instruments - SolarMax II 90 3.5" F/8.8 solar telescope with 30mm blocking filter

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Our Product #: SMT90-30
Manufacturer Product #: SMT90-30
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The <0.7 Ångstrom H-Alpha solar filter of the Coronado SolarMax II 90mm solar telescope combines with unique RichView tuning and a large 30mm blocking filter to provide you with high definition views, binoviews, and 35mm format imaging of solar flares, prominences, and more . . .

. . . our 38th year