1.25" Solar Wedge (Herschel wedge) for refractors

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The Lunt 1.25” Solar Wedge (Herschel Wedge) is used to observe the sun in white light with refractor telescopes only, without using a filter over the objective lens. Unlike glass and film objective solar filters, the Lunt Solar Wedge does not selectively filter any of the visual wavelengths, thereby providing a true all-wavelength white-light view without the image degradation from the scattered light inherent in standard objective filters. Visual and photographic images through the Solar Wedge are noticeably superior in resolution and contrast to even the finest and most expensive glass and film objective solar filters.

The Lunt Solar Wedge uses a precision-polished wedge prism in a 1.25” star diagonal housing to deflect 95% of the sunlight away from the visual and photographic light path. The original 200 year old Herschel wedge prism design simply dumped the unwanted 95% of the light out through the underside of the prism housing (where the user had to be careful not to place any object or body part into this output beam to avoid burns). Instead, the Lunt design directs this unwanted light to a circular grating within the wedge housing, which scatters the energy within the housing’s blackened interior. Vents at the top and bottom of the housing allow cooling air to flow through the housing to dissipate the heat from this scattered light. The circular grating (the red circle seen at the rear of the prism housing) will get hot during use, and care should be taken not to touch it during use and until it has had time to cool down after observing.

The remaining 5% of the light used for observing and imaging is reduced to the desired brightness level by a precision-polished neutral density filter permanently built into the wedge housing. Since the neutral density filter is always in the system, there is no chance of accidentally viewing the unfiltered light as with some other Herschel wedges. Because the Lunt Solar Wedge produces polarized light, Lunt recommends that you thread an optional polarizing filter into the barrel of your eyepiece for visual use. Rotating the eyepiece with the polarizing filter installed lets you adjust the image brightness to a comfortable visual level with larger aperture refractors.

The amount of sunspot detail and surface granulation will surprise even the most experienced solar observer. Penumbra resolve into a staggering array of fine wispy details with a wide range of contrast never visible with an objective filter. The solar disc is set against a jet-black sky, like observing the full moon at night. With the Lunt Solar Wedge, it becomes obvious that the lack of detail and contrast experienced with objective white-light filters was not so much due to the atmospheric seeing as you had thought, but rather due to the short-comings of the objective filter itself. There is no resolution or contrast loss across the full field during full-disc solar imaging and the image will not break down during high magnification visual observing.

CAUTION: Because the full energy and heat of the sun enters the unfiltered telescope aperture with this system, the Lunt Solar Wedge should only be used with air-spaced refractor telescopes under 150mm in aperture. In addition, the refractor must not have a corrector lens or lenses at the back, such as found in a Petzval-type scope. Optical elements like refractor corrector lenses or the secondary mirror of a reflector telescope become very hot from the concentrated unfiltered solar energy and can be damaged. The internal baffles and components of catadioptric scopes (Schmidt-Cassegrains, Maksutov-Cassegrains, etc) can likewise be damaged. Choose your telescope with care to avoid damage to the scope when using a Solar Wedge.

Likewise, care and common sense should always be used whenever observing the Sun. An occasional break from observing, with the scope turned away from the Sun, will give you and your scope a chance to cool down. Equatorially mounted scopes that are tracking the Sun automatically should not be left unattended when using a Lunt Solar Wedge.

The weight of this product.
8 oz.
1 year
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1. ERIC on 6/26/2014, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
I use the version for 1 1/4 inch eyepieces and put a polarizing filter on the eyepiece. This is for a 5-inch f/7/5 triplet refractor. It compares favorably to a full-aperture, front-end glass filter (Thousand Oaks), which is good, but which does not bring out the detail in the sunspots and, yes, granulation the way the Herschel wedge does. What the says is true about "seeing" not explaining everything - the resolution definitely deteriorates after early morning for the glass front-end filter, but amazingly this Herschel wedge produces a fine image in the afternoon!
I do move the telescope off the sun after viewing for no more than a few minutes - the heat sink (red dot) - as others have mentioned - does get warm, but not dangerous to the touch.
The competition - at considerably more price - is, of course, Baader.
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2. James on 5/15/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
Purchased a 1.25 inch solar wedge for viewing and imaging the Sun. Five stars on both counts! Image is still uncomforatbly bright even with a 100mm f/9, however the use of a solar continium filter, moon filter or polarizer brings it to a comfortable level. Sharp, clear sunspots can be seen and photographed (I use an Imaging Source camera) and are superior to any glass filter/Baader film option.
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3. Craig on 5/1/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
Lunt does a great job on their Herschel wedge. I bought the 1.25" but I've used both the 2" and 1.25" versions and they're both fantastic. Both are very nicely constructed with precise machining and both are optically outstanding. Each also comes with a good quality metal case with custom foam cutouts for storage and transport.

The 2" version I tried produced a slightly yellow view, which I found pleasing to the eye. The 1.25" inch one I bought produced a pure white image. I suspect this difference has more to do with the permanently installed ND filter than anything else. If you install a polarizing filter on your eyepiece, you can fine tune the brightness of the image by rotating it in the wedge- a very nice feature especially if you're zooming in and out.

One thing to consider with a Herschel wedge is where the rejected light goes. On the Lunt wedges that energy is dissipated through a heat sink (the red disk), which works very well and has not, in my experience, become hot enough to be a hazard.

I would definitely recommend this to anyone with a qualify refractor looking for the best possible white light views of the Sun. Using my AP 130 and the Herschel Wedge I routinely see granulation across the entire disk, incredible detail around sunspots, and subtle contrast near the limb. It's also a great compliment to H-Alpha, especially if you can dual mount the scopes and align them so you can study features in both white light and H-Alpha by moving back and forth between the eyepieces.
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4. Eric on 9/27/2012, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
Just received my new Lunt Herschel Solar Wedge in only 3 days, thank you Astronomics!

I bought the 1.25" not the 2" for two reasons.
1: The 2" were sold out and more importantly,
2: I found that not all of my refractors can achieve focus with a 2" diagonal. The first scope I tested with this new gear was a very cheap yet stout 90mm achro of unspecified focal length, somewhere around an f6 if I had to guess. Not a bad view and nothing burst into flames so a good test. I summoned my courage and brought out my 80mm ED APO triple and set up between clouds. One thing I should note from the first scope was the brightness of the sun's image. Even down 10mm to the eighty, being an ED APO, was brighter still. Definitely put a polarized ND filter on the end of your eyepiece and it does indeed allow fine tuning of the brightness when turned in the diagonal. The views through the APO at 96 power were crisp and well defined. Perhaps even slightly better than the 8" f4 newt with a film objective filter. Not too shabby. One main reason I bought this is that it eliminates the need for me to buy a different sized filter for each of the 4 refractors. Alas I could not put this to the real test, my f8.3 XLT 120 because the clouds came to stay. I love that scope for lunar and planetary and the CG-4 mount tracks nearly perfectly which is a real bonus for public observing. I will update once I have set up and tested the XLT. Clear skies!

Update 9/30/12, had a chance to set up the 120mm XLT. The stated limit for telescope size for the Herschel is 150mm and I believe that is possible as long as you are careful. With the full aperture exposed the view was again very bright to the point of being uncomfortable and the ceramic at the back did indeed get hot, not enough to burn but you would not want to keep holding it. The end cap for the scope has a step down port or "choke" on it. This steps the aperture down to about 50mm. Designed for lunar observing this has the effect of reducing CA and brightness. Now bear in mind you can use the full aperture and a filter to adjust the image but that is like maximum rpm to an engine in first gear. Why burn up the ceramic when you do not need too? The Herschel cooled down noticeably and the fringe color was reduced greatly. Once I put the polarizing filter on the eyepieces the CA quickly disappeared . Note that this scope normally has almost no color for an achro. The extra focal length coupled with some orthos or wide field EP's really brought out details I have never seen before. I even used my bino viewers for the first time in ages. 2x Barlow on the nose and I was in sun spot mode. the medium dark areas around the actual sunspots showed texture at the edges and light bridges across the spots became visible. I highly recommend this to anybody interested in in white light solar observing and getting bang for your buck!
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Lunt Solar Systems - 1.25" Solar Wedge (Herschel wedge) for refractors

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Lunt Solar Systems - 1.25" Solar Wedge (Herschel wedge) for refractors
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Unsurpassed white light solar surface detail and contrast from refractors up to 150mm in aperture is yours with the 1.25” Lunt white light Solar Wedge . . .

. . . our 38th year