Classic Ortho 18mm, 1¼" Eyepiece (HT-MC)

Baader Classic Ortho/Plössl eyepieces

Baader Classic Ortho/Plössl (Q-Turret) 1¼" Eyepieces

HT-MC-coated

Parfocal eyepieces with a very high transmission, very good contrast and a field of view which is free of distortions because of this design. The multi-coating eliminates almost all internal reflections. The eyepieces provide 50° apparent field (6/10/18mm Ortho), sharp field stops and excellent ergonomics for comfortable observing. The eyepiece body is made without plastic, while the lenses use heat-resistent cement, so that all four Classic eyepieces can be used for solar projection.

Classic optical design of orthoscopic eyepieces

The lens assembly consists of one plano-convex eye lens and a triplet-element (or two doublet elements in case of the Plössl) with heat-resistent cement, so there are only four glass-air-surfaces in each of the Classic Eyepieces. Everything is made of sturdy metal, with the only exception of the eyecups and dust covers. For better heat protection, each eyepiece has got two seperate field stops for a better distribution of the heat during solar projection. All interior metal surfaces as well as the edges of the lenses are carefully covered matt black to effectively suppress stray light, even when the telescope is pointed straight at the sun. Of course, the hard anodised barrel has got a 1.25" filter thread.

Looking into the eyepieces, you'll see the effect of the anti-relex-coating and the blackened lens edges. The coating is so good that it seems like there are no lenses at all! On our optical bench, we couldn't find any disadvantages compared to so-called "planetary eyepieces" which cost five times more.

The Ortho eyepieces use the same glasses and the same optical design as the old orthoscopic Zeiss Jena eyepieces.

The 32mm-Plössl-eyepiece is the perfect eyepiece for a large field of view at telescopes with 1,25"-focuser; eyepieces with longer focal lengths don't provide a larger field of view (but a smaller apparent field). The field stop diameter is as large as possible for a 1 ¼“ nosepiece; that's why even eyepieces with a longer focal length can't show a larger piece of the sky.

Technical data of the Baader Classic (Q-Turret) eyepieces

Focal length (mm)	Optical design	Barrel	Lens elements / groups	Apparent field of view	Parfocal	EyeRelief (mm)	Field stop (mm)	Height (mm)	Diameter	Weight
6	Classic Ortho	1¼"	4 / 2	52°	yes	5	5	34,2	34,8	37g
10	Classic Ortho	1¼"	4 / 2	52°	yes	8	8,7	41,12	34,8	48g
18	Classic Ortho	1¼"	4 / 2	52°	yes	14,67	16,8	54,46	34,8	81g
32	Classic Plössl	1¼"	4 / 2	50°	yes	21	26	78,8	34,8	94g

Baader Classic Ortho/Plössl-eyepieces for Digiscoping and as Planetary Projection Eyepieces

Standard Barlow elements often can not provide enough magnification for taking images of the planets. Classical eyepiece projection is the solution if you want to increase the focal length by 4x or more. The Classic Orthos provide the necessary high magnifications in combination with an OPFA (Eyepiece Projection adapter). Orthoscopic eyepieces are well-known for high sharpness on the axis and very good transmission – perfect for planetary observations. So, it is possible to get sharp views of the planets even at very high magnifications.

Using an OPFA, you can set the magnification almost without limits by changing the distance between eyepiece and camera sensor. You can find information on calculating the resulting focal length in the description of the OPFA-system. For best results and highest resolution, you should use the Fluorit Flatfield Converter (FFC / 3x-8x) instead, which was designed especially for projection photography.

Photography with Classic Plössl, smartphone and Celestron NexYZ

The Classic Plössl is perfectly suited for afocal projection with the ADPS (Afocal Digital Projection System) and a compact camera with fixed lens – the eyepiece's large lens on the camera side reduces vignetting, so that you can use a larger part of the camera sensor. The lower magnification and the resulting larger field of view make this combination very interesting for images of the surface of moon or sun (the latter only with a suitable solar filter).

Both the 32 mm Classic Plössl and the 18 mm Classic Ortho are also ideal for photography with a smartphone (digiscoping). The housings are long enough for smartphone adapters such as the Baader Lightweight Smartphone Adapter (LSA) # 2967000 or the Celestron NexYZ #825821. Simply center the camera lens above the eyepiece and use the camera zoom to adjust the image to the camera's field of view.

The lean housings of the Classic-eyepieces with diameters of less than 35mm fit without any problems into all common projection adapters and can also be used without problems for visual use at any binoviewer.

Solar Projection

Solar projection has gone somewhat out of fashion in recent years, partly because the classic, open solar projection screens do not completely seal off the beam of light, leaving areal risk during observation, and partly because the classic eyepieces for solar projection without cemented lenses are no longer produced in good quality. The UV-cured cement with which many eyepiece lenses are combined to a unit in favor of quick lens mounting is not heat-resistant, so that the eyepieces become blind during solar projection because such cementing can easily burst.

Both the Classic Orthos and the 32 mm Plössl use a heat-resistant cement and have been successfully and repeatedly tested continuously for up to six hours on refractors with lens diameters of 150 mm (150/2250 mm and 150/1200 mm) without any damage to the lenses or the metal parts of the eyepieces. Thanks to the double-staggered metal field diaphragms, even inaccurate tracking is not a problem, only the black anodization of the housing can fade slightly on the inside if the focused sunlight falls on the field stop for an extended time instead of passing centrally through the eyepiece.

With the Classic Ortho/Plössl eyepieces, eyepieces are finally available again with which solar projection is also possible without the lens cement being destroyed or plastic parts inside evaporating and forming a milky layer on the optics of the telescope.

Classic eyepieces in continuous use for solar projection on 6" refractors