TECNOSKY HERSCHEL PRISM 2″ CERAMIC REVIEW

TECNOSKY HERSCHEL PRISM 2″ CERAMIC REVIEW

 PREMISE

For years I have been a fairly good enthusiast of solar observations in white light, for this reason I have been happy to test the Herschel prism with ceramic window proposed by Tecnosky.

It currently costs 390 euros and benefits from a two-year warranty. On the official website of Tecnosky, Furthermore, you can take advantage of the three-part payment option offered by Scalapay. I tested it on three telescopes: a Takahashi FS 128 mm F/8.1, a mineral fluorite doublet; a TeleVue Origin 3-76 mm f/7.4, a vintage cemented triplet; and a Celestron XLT 150 mm F/5, the classic short-focal length achromatic doublet for use at medium-low magnifications.

 

 

 

TECHNICAL CHARACTERISTICS

I'll start by saying that, as the owner of a Baader Cool Ceramic filter and having used an Intes MICRO Herschel prism in recent years, I'm quite accustomed to observing the sun in white light with excellent quality products. Aesthetically, the new prism sold by Tecnosky also displays substance and an excellent design. It comes in a well-padded case with compartments for several accessories.

It is made of an anodized aluminum hull and weighs approximately 880 grams.. To solve the heat dissipation problem very well sSome vents have been inserted in the rear part. There is also a discreet ceramic window that allows almost all the heat produced by sunlight to dissipate. Thanks to this feature, it is possible to use the window as a solar finder, without necessarily having to aim by trial and error or install some solar filter on the telescope finder lens.

Another great feature of the new Herschel prism from Tecnosky is the presence of a two-inch ND3 (neutral density) filter that allows you to further reduce the light transmitted by the prism (declared a reduction of 5%), furthermore the presence of a polarizing filter will allow you to adjust the brightness according to your needs. This is achieved thanks to the anodized red ring. The filter is obviously removable to allow shooting with planetary cameras. For the safety of your eyes, however, you should not remove the ND filter.

 

HOW DOES THIS FILTER WORK?

 

As you may have understood from reading the previous paragraph, this prism must be inserted inside the two-inch eyepiece holder of your refractor (it cannot be used with Newtonian or mixed systems). Sunlight enters the 45° inclined prism and is transmitted only in a minimal percentage, usually from 5.5% to 4.5%. Excess sunlight passes through the heat-absorbing ceramic window. QThis type of tile traps radiant heat without overheating the surrounding environment (if it did, you could burn your legs while observing).  This is one of the safest methods for observing the sun in complete tranquility.

 

WHAT TO OBSERVE?

I believe that white-light observation has been somewhat overtaken—unfairly—by the advent of H-alpha systems. In reality, it is possible to make very interesting observations of the solar photosphere (sunspots, faculae, granulosphere, pores), especially if you use telescopes of a moderate diameter and Herschel prisms instead of the common filters inserted in front of the objective.

 

FIELD TEST

 Visual observation

I reiterate once again that this filter can only be used with refractors; therefore, it cannot be used with Newtonians, Schmidt-Cassegrains, Maksutovs, and the like. In reality, it would be possible to observe with a modified Newtonian by replacing the secondary mirror with this prism, but since most of the heat would be released at the rear, there would be evident internal reflections, in addition to the formation of hot air capable of creating significant focal turbulence.

For this reason, if you have an achromatic, HD, ED, semi-apo or Apo refractor, you can use it with extreme peace of mind. Over the weeks of use I had the pleasure of using it with the above-mentioned refractors and a photographic session was also carried out with a 10 cm F 10 refractor by Antonio Giudici of the GAV of Varese.

For purely visual observations, having some solar filter available, I made some comparisons and I enjoyed a much sharper and more contrasty image with the Herschel prism than with the normal solar film.. Also thanks to the presence of an excellent anti-reflection coating on the prism and the dispersion system, the images are free of reflections, diffused light with a very sharp and high-contrast perception of both sunspots and surface granulation. These findings were visible in all three telescopes, although, obviously, the Takahashi FS128 fluorite telescope produced truly captivating images.

Compared to the solar film, sunspots appear much more contrasting, with a distinct black color rather than a dull, pale color. The penumbra is also much more visible, and the granulosphere appears much more distinct, almost engraved on the solar surface.. Using the 150° achromatic refractor, which certainly isn't great for contrast, the graininess was much more evident with this prism. I also found the polarizer very useful, allowing me to adjust the brightness not only based on the telescope used but also on the sky's transparency conditions.

It goes without saying that the ceramic window allows for much safer observations than the common Herschel prism design, which channels solar energy out of the system. In this case, it would be necessary to avoid exposing our bodies to the radiation.

 

Photographic test

For the photographic test, Antonio Giudici shot a video with a William Optics Zenistar SD telescope, a 66 mm Apo doublet opened at F/5.9. He used a QHY5III 462 C camera, EQ4 mount, 100 frames per 30 frames per second, gain 27, original size 1920×1090, and processed with Registax. Unfortunately, the seeing was only fair.

 

PROS AND CONS

Merits

• Excellent purchase price when compared to other ceramic window solutions
•  Presence of an ND filter to reduce solar radiation to very safe values
• Removable polarizing filter to customize observations
• Constructive care
• Ceramic window
• Easy aiming thanks to the ceramic window
• Sharper and more contrasty images compared to common solar film observations

 

Defects

Honestly, it's hard to find any. Perhaps I would have preferred the instructions for removing the polarizing filter to be included in the box for beginners.

IN SUMMARY

The TECNOSKY 2" CERAMIC HERSCHEL PRISM has proven to be an indispensable quality accessory for white light solar observations. It is well built, designed with quality primers and coatings, and features a removable polarizing filter that allows you to improve your viewing experience based on the diameter of the telescope used and the transparency of the sky, as well as making solar imaging possible at high frames. The price-performance ratio is excellent compared to the competition, as the differences in sharpness and contrast are minimal.

THANKS

I thank Giuliano Monti, owner of Tecnosky for providing the telescope that was the subject of this test. 

DISCLAIMER

This review was published in March 2023. Please note that the impressions of use are entirely personal and given by Binomania testers in complete freedom, without any commercial obligation or relationship, and based on proven experience in using these optical instruments. For any information, updates and/or changes to prices, instrument features, authorized sales points, or other information in general, please contact Binomania directly.  Tecnosky 

Shops suggested by Binomania.co.uk