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Barlow lenses, their magnification factors and working distances
Again and again the question arises whether a barlow provides the correct magnification at all. It is often overlooked that the magnification factor always depends on the correct working distance - you can read more about this in this PDF using the VIP Barlow as an example: Different Magnifications with the VIP-Barlow # 2406101 To settle this question once and for all, we took a few comparative shots on an ED80/600 telescope with a monochrome camera. Due to the seeing on a hot summer at an outside temperature of 30 °C, the shots of a neighbouring roof were somewhat unsteady, so that the sharpness of the individual frames is only of limited use for judging the quality of the Barlow lenses, but here we are only concerned with the scale of the image. On this occasion, the focus shift was also measured: A barlow moves the focus point and is often used to come into focus when there is not enough back focus. To do this, the actual barlow lens element is placed deeper in the focuser and the focus moves outwards. The reference shot: Fokal, without an additional barlow lens At first, a shot without an additional barlow... -
The camera at the eyepiece
Pitfalls and opportunities In this article we want to show the different ways to enlarge the image or to take pictures through the eyepiece quickly and easily with a camera. These techniques are interesting for photographing the moon and planets as well as for anyone who wants to photograph through an eyepiece - for example, for nature photography through a spotting scope. "Getting closer" is the goal of many photographers. In other words, the longest possible focal length to image the objects as large as possible on the sensor. A practical rule of thumb for astronomers is that the sun and moon appear on the sensor approximately with a diameter of just under one centimeter per meter of focal length. Since long focal length telescopes quickly become very unwieldy or at least require a very heavy mount, it is difficult - especially as an amateur - to reach for the largest possible telescope. A 14" Schmidt-Cassegrain with 3900 mm focal length, as it can be found on many observatories, is for most people the longest focal length telescope, which they can access at least through a club membership. So how do you get closer? The answer is simple: a magnifying... -
Eyepiece Projection - How good can it get?
Question: With eyepiece projection, the image at the edge is extremely blurred. What could be the reason for this? For eyepiece projection with our Morpheus and Hyperion (zoom) eyepieces, we recommend a distance between eyepiece and T-ring of 40 mm on full-frame cameras, in addition to the 55 mm that were the flange focal distance of all "SLR" and DSLR camera bodies for decades when a T-ring was placed in front. Only with a T-ring that maintains this distance can old lenses with a T-thread deliver sharp images. Therefore, it has been tried to take this distance into account in all designs, because this is the only way to ensure that the sharpness performance is optimal. Of course, all this is only valid to a limited extent today - because the DSLR standard is losing it importance and the term „T-ring“ is all too often reduced to the mechanical thread and not the correct distances. In our brochure on digiscopy, we have therefore stated the back focal distance of 55mm. With a DSLR (full frame or APS-C), this distance is also maintained in good approximation with modern, narrow T-rings, which are intended for use on telescopes, where every millimetre often... -
25th anniversary of TEC - Apochromats of the top class
The "Telescope Engeneering Company" has long earned a reputation as a top-class telescope manufacturer. The family business in the US state of Colorado has been manufacturing telescopes of the highest quality in small series since the 1990s. Before TEC manufactured the first refractors in the year 2000 (regular production of APO140 started in 2002), TEC were offering Sitall mirror sets from LOMO (upto 1.4m) and MAKs from 150mm to 300mm. The distribution of these products is stopped. The three Petrunins are based on class instead of mass, therefore the delivery times are long! But the quality is also outstanding: TEC is one of the few manufacturers in the world that still masters durable oil-spaced triplet lenses. This results in particularly robust and stable optics that cool down very quickly and effectively. During the 15 years that Baader Planetarium has been importing TEC telescopes to Europe, only one oil-spaced lenses had to be renewed. We can therefore vouch for the quality and long-term stability of this oil-spaced lenses. Read more about the advantages of oil-spaced lenses for apochromatic triplet objective. In years of work, TEC has now succeeded in manufacturing all device classes with a genuine Fluorite as a middle element. In...
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Eyepiece Projection - How good can it get?
Yuri Petrunin (183 cm tall) with a TEC APO 200 f/8 Fluorite Apochromat (#1351030 , € 40500,-)
The "Telescope Engeneering Company" has long earned a reputation as a top-class telescope manufacturer. The family business in the US state of Colorado has been manufacturing telescopes of the highest quality in small series since the 1990s.
Before TEC manufactured the first refractors in the year 2000 (regular production of APO140 started in 2002), TEC were offering Sitall mirror sets from LOMO (upto 1.4m) and MAKs from 150mm to 300mm. The distribution of these products is stopped.
The three Petrunins are based on class instead of mass, therefore the delivery times are long! But the quality is also outstanding: TEC is one of the few manufacturers in the world that still masters durable oil-spaced triplet lenses. This results in particularly robust and stable optics that cool down very quickly and effectively. During the 15 years that Baader Planetarium has been importing TEC telescopes to Europe, only one oil-spaced lenses had to be renewed. We can therefore vouch for the quality and long-term stability of this oil-spaced lenses. Read more about the advantages of oil-spaced lenses for apochromatic triplet objective.
In years of work, TEC has now succeeded in manufacturing all device classes with a genuine Fluorite as a middle element. In terms of transmission and colour purity, these optics are far superior to all "APOs" with ED lenses or similar, which are available today. If you haven't seen the difference with your own eyes, you can't imagine it. It is last bit of sharpness that literally gets you going when you focus on an oil-spaced triplet lens with Flurite as a middle element is an incomparable experience.
TEC is currently the only company, which offer an impressive range of optics from 140mm up to 300mm aperture in series production.
Also the TEC APO 140 f/7 Fluorite Apochromat (#1351005 , € 10680,-) - the most popular size of all TEC telescopes TEC is now available as fluorite apochromat. It is for everyone’s needs. The scope is light weight, portable, and can be used for visual or CCD imaging. With the suitable field flatteners and reducers a world of possibilities is open to you. Due to its optical design, even solar observation is possible, whether with H-alpha filters or whitish light using a Herschel Prism.
TEC APO 140 f/7 Fluorite Apochromat (#1351005 , € 10680,-) :
- Apochromatic Triplet Objective
- Clear aperture 5.5" (140 mm), focal length 980 mm
- Excellent color correction thanks to glass combined with Fluorite as a middle element
- The color correction is optimized for visual use with focus shift less than 0.02% from 436nm to 1000nm.
- Durable oil spaced lens - Why an oil-spaced triplet-lens?
- 3.5" Feather Touch Focuser of Starlight Instruments
TEC APO 140 f/7 Fluorite Apochromat (#1351005 , € 10680,-)
TEC APO 160 f/7 Fluorite Apochromat (#1351010 , € 17600,-)
TEC APO 180 f/7 Fluorite Apochromat (#1351080 , € 26100,-)
The currently available bino-telescopes of several manufacturers usually have apertures between 80 and 120 mm. TEC only starts at 140 mm.
As customers requested, TEC has started to offer astronomical binocular telescopes or "binoscopes". Such instruments offer an extrordinary usability and functionality for visual astronomy. The well-known advantages of binocular viewing can be found in perfection here.
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