What customers say about my products
„After many years of observing with a 15 cm telescope, I decided to move a little higher. I always wanted to build my own telescope so I took the chance and started the making of a 25cm truss dob. I wanted to have an extraordinary telescope - and the heart of such a telescope is extraordinary quality optics.
When I examined the various sources of parabolic mirrors, I happened to see the offer of Libor Němec - he had finished 250 mm mirror of ideal focal ratio f/5.3 and claimed an excellent value of the Strehl coefficient of 0.98! Its price was very good so I did not hesitate and ordered the mirror. At first I was somehow skeptical - after all, optics of such quality would belong among the world extra-class and the price of similar mirrors goes significantly higher. Initial tests showed mild overcorrection and slight astigmatism, which I took as confirmation of my initial skepticism.
Then I ordered a new high quality secondary mirror from Antares, equipped my telescope with a fan to improve cooling and added a shroud to avoid turbulence inside the tube. WOW, the image quality was suddenly absolutely fantastic! The star test is now almost perfect, with very similar intra- and extrafocal diffraction patterns. If there is a night of good seeing then my telescope gives incredibly sharp and contrasty images. Under favorable conditions, I watched the moon with almost 600x magnification - it is hard to find words adequately describing the view. As it would be from the Apollo ship window... In direct comparison with 20 and 30 cm SCTs of well-known manufacturer the image in my telescope was significantly better. I could see the central star in the Ring Nebula, and I saw objects on the border of the 15th magnitude. I have no doubts about the great quality of Libor’s mirror – if you are looking for excellent optics, I can warmly recommend. I am 100% satisfied.
“
Michal Bareš, 250mm f/5.3 mirror
„When I was deciding where to take my ultra light mirror, I was looking for something thin, around 30 mm. Finally, the choice fell on the mirror with the diameter of 405 mm and the thickness of 25 mm (borofloat glass), which comes from Libor Němec. It is already really thin, but I decided to take a risk, and I hope that the surface will be figured properly. It was obvious that such a thin mirror will demand absolutely precise mounting, and so I built the mounting with 27 points.
I was very curious about the "first light". This even happened at Libor’s place in his tube, but the mirror lay only on nine points, with no lateral support, only supported by three pillars on the sides, so observing close to the horizon led to deflection of the mirror and caused moderate astigmatism. However the view of Saturn (it was quite high), was wonderful, especially when there was good seeing.
When Libor was giving the mirror to me, at first he did not want to, because he thought it was not as good as it could be, and so he wanted to make a new one for me. But eventually I convinced him and I took the mirror. I must say I definitely do not regret it. After finishing the telescope and mounting it to all 27 points, with support around the mounting, and after fixing up a few small problems the picture is virtually perfect now. Under excellent conditions it is possible to use 500 times magnification without any problems, when a star shows symmetrical diffraction pattern, with a clearly defined Airy disc and diffraction rings around it. Unfortunately, such conditions are pretty much rare here, so my shortest commonly used eyepiece is a 7 mm Nagler Type 6, which together with a Paracorr and a 1738 mm focal length mirror (f/4.3) provides 285 times magnification.
“
Martin Myslivec, thin 405mm f/4.3 mirror
„As I consider myself a handy man it was always my dream to build a larger telescope. On the other hand I somehow did not feel qualified for production of optics. Therefore I started search on the internet for optics producers. As it is, one quite often chooses with respect to the price of a product (if you are just building a house, it can not be otherwise - my case). After a short search I found Libor Němec’s site. Together, we exchanged a few e-mails, where we agreed on the parameters of the mirror, delivery date and other details. When Libor told me the price, I immediately ordered the mirror – the price surprised me pleasantly.
I wanted to use the telescope primarily for astrophotographs, so I chose not such a large mirror, but well proven "classic" – a parabolic mirror with the diameter of 200 mm and f/4.3 speed. Libor even recommended me a manufacturer for a secondary mirror so I could start the construction. The optics was made in time. Due to the lack of free time I finished the telescope a few months later though...
After taking first few photographs, I began to doubt the quality of the mirror. There was a diffraction image composed of great amount of fine rays, instead of diffraction cross caused by secondary mirror holder, so the bright stars looked “hairy”. Though after a few tests, I found out that hairiness is caused by the fuzzy tube edge pasted with black velvet wallpaper. Once I made a small curtain on the edge of the tube, the diffraction pattern was as it should be. So the mirror is perfectly alright than.
For visual observation I am happy with the optics, too. Under ideal conditions I can use 400-500 times magnification for the Moon without any significant deterioration of the picture quality. When looking at the Pleiades, Jupiter or Saturn my knees always start shaking :). Just beautiful, nice sharp Pleiades stars, planets have high-quality contrast images (of course within the limits of the size of optics). I can say that negotiations with Libor were always absolutely fair, smooth and when there is added a favorable price and quality, I do not have any complains then. I am planning to make a larger Dobson (400-500 mm) and the optics will be again provided by Libor ...
“
|
M33 |
M27 |
M78 |
|
M31 |
||
František Bílek, mirror for Newton 200/860
„I bought a 254 mm mirror and after a variety of (mostly not very successful) attempts to build a telescope, I decided to give it to someone who can do it.” I chose Libor Němec (at that time I had almost no idea about good telescope producers but we negotiated a favorable price). When I saw a couple of finished telescopes at his place, I started to think, whether to pay a bit more and get the collapsible 300 right away. It did not last long and I called Libor and made the decision.
So today I have a collapsible Newton of 300mm/1500mm on Dobson mounting. Everything works perfectly, the optics draw beautifully, but I consider the manipulation as a major advantage. Composition/dismantling is no problem, nothing scrubs and force is not needed. Due to the robust construction, there is no need for frequent collimation, although the tube consists of three parts. The observation itself is also no problem. The truth is, that today I would spend extra money for the vertical axis bearing, but at the time of purchase I had limited finances. Still, I managed to watch an overflying ISS on teflon with about 90 times zoom without any problems (it was possible to distinguish individual modules, however, not astronauts’ faces :-). Maintain Saturn at 333 times magnification is not such a big problem, neither.
The telescope has been serving me for two years, still to my satisfaction. If you want a telescope for observation and you do not have a stable observatory in the garden then you will be excited with collapsible Dobson. Mechanically and optically it is excellent and the ratio of storability / diameter is unbeatable.“
Martin Kočí, telescopic dobson 300/1500
„I watched the sky for a long time just with my eyes or with a binocular at most. More I watched the less satisfactory it got so I began to look for a telescope that is designed for star observation. At first I started to look for it at commercial producers, but eventually somebody told me that the quality is questionable and that there are people who construct custom-made telescopes and of better quality. And so I soon found Mr. Drbohlav’s site and I realized that it is possible to have a telescope of such dimensions, which I had never even dreamed of! But there was a problem – they were too heavy and bulky, and I needed to drive to the countryside to see stars. But fortunately I found Libor Němec’s site and suddenly I realized that even a "big" telescope is available for me also from the practical point of view! I did not hesitate too long (I was really so excited) and ordered a telescope.
Its construction took less than a year and it is a telescopic Dobson, with the diameter of 250 mm and 1500 mm focal length. It weighs only 12 kg and it can be disassembled in a way that it can fit well onto one car seat. I was a bit afraid that assembling it to a "working" position will always be a problem, but everything is designed and made so that now it takes me less than 5 minutes, I can handle it myself without any help, and it certainly is not "trouble", on the contrary. It runs very nicely in Teflon bearings, they do not rub or slide too much, so the movement is beautifully smooth and now I can watch, for example, ISS flyover so I can keep it in the visual field almost all the time. Another thing, that surprised me, is stable collimation. I was afraid that frequent folding and disassembling will require collimation almost every night but the opposite is true, and I collimate really very rarely, and that is more for training, because it practically is not necessary :-) When I went to pick the whole telescope up at Libor’s place, the first object we tested the telescope on was Saturn. I really did not expect to see what I saw! It was still dusk and a beautiful image the planet appeared in the vision field, with a beautiful ring split by a wide dark zone – Cassini’s division, and a bit further by another dark strip – Encke division. Now Saturn is closing and it is not as good as it was, but I am looking forward to seeing it again in a few years, the view was just perfect and I often enjoyed the view.
I can see stars of 14th magnitude without any problems; the number of NGC galaxies I can see is simply enormous; with respect to magnification, the shortest eyepiece I dispose of has f = 4mm, that gives 375 times magnification ... And I know that limiting for me is not the optics quality but the air quality (seeing). But when conditions allow it, the Moon with such magnification is simply wonderful! The optics would certainly withstand even greater magnification but it is no longer convenient due to very rapid movement of the object out of the visual field. I know that I did not make bad choice, and this is perhaps the reason that when I wished to a step further (yet bigger diameter), I again contacted Libor and I ordered another, this time a 400 mm Dobson, which is about the maximum that can be used in one person and transported in a standard passenger car. After all, dealing with Libor is very fair, especially when he is willing to adjust to everybody’s requirements.
I am sure that I can not do more for my experiences under the star sky. And even now I am looking forward to fulfilling my next dream :-)
“
Jan Mikát, telescopic dobson 250/1500
„Since May 2007 I have had Libor’s telescope with the diameter of 400mm and focal length of 1,800mm. He gave it to me during “Hvězdobraní” gathering in Litice. I also had a 300mm telescope of the same design prior to this one and I was very satisfied with it. When purchasing a bigger telescope the choice was obvious.
The weather was fine in the next months so I could therefore properly test the telescope on various objects. After the 300mm I did not expect any significant improvement in objects depiction, but I was very pleasantly surprised by the possibilities that were revealed before me. The diameter is important ... an immense help is the telescope storability. The proportions in the collapsed state are sufficiently small to fit into a standard passenger car. Assembly – expanding of the tube is simple and fast, thanks to a clever design and accurately fabricated parts. Screws fit into tapped holes without any difficult search of the proper tube position, you can just pull it out to a backstop and it fits. Operating of Dobson mounting is smooth both in azimuth and in elevation and it allows fine adjustments even in larger magnification. So I have no idea why it is claimed that Dobsons are generally very clumsy for observations near zenith. I have never had any insurmountable problems with this, and I have always got where I needed to. A large diameter of the telescope allows deep insights into the universe, indeed. Without any problems, with a good seeing, I managed to get onto 15.5mag., the very limit of the optics. I am able to track flat objects e.g. comets even at 14.5mag. Galaxy, that has 15mag. Absolutely amazing views are of broken nebulas or the spherical star clusters. You can see interesting details even in galaxies, in galaxies clusters, especially Abell 1656 surprised me, it is really possible then to see dozens of these objects, it is something totally extraordinary. I use the telescope primarily for visual estimates of comet brightness. This telescope is the peak of what I have had so far. It meets all my requirements for the quality of processing, view and mobility. It is a good piece of work Libor - Thank you.
“
Michal Kobliha, telescopic Dobson 400/1800
