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Mag 1 Instruments Portaball 8 |
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REVIEW ARCHIVES Refractors Barlow
Lenses LINKS FAVORITE LINKS NASA
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The telescope can not be purchased off-the-shelf, but has to be ordered from the manufacturer, Peter Smitka. Delivery time is in the 4 – 6 months range. The telescope comes without eyepieces. Some extras can be purchased with the telescope. The reviewed item was delivered with a light shroud and a laser collimator. Eyepieces and other accessories used: University Optics Konigs and Orthoscopics (24mm, 16mm, 9mm and 5mm), Lumicon O-III filter. Background of the ReviewerI have been active in the hobby for more than 30 years, and have owned several scopes, reflectors, refractors and catadioptrics. I limit my activity to visual observation, considering “astrophotography” to be an expensive word. I know the sky very well, and the GOTO utility is not interesting to me. My favourite objects are double stars. I can do quick observing from my garden, and can reach dark observation sites with excellent conditions within less than one hour. I have owned the Portaball for about 5 months, the weather has been bad for most of the time, but occasionally observation conditions have been excellent. Practical Experience with the PortaballThis is by far the best telescope I ever owned. I can hardly think of any telescope within the size range up to 8 inches that would serve my needs better. I emphasise that this is not a telescope for the person who wants the GOTO facility, automatic tracking or wants to do astrophotography. However, the last two issues can be resolved by adding an equatorial platform. Optical Performance At F/6 the Portaball is an all-round instrument. From a dark site the Veil nebula in Cygnus is easily seen without a filter, and other elusive objects like the nebulosity near z Orionis (NGC2024 and IC434) can be detected. However, a filter (UHC or O-III) is needed to see the Rosette nebula. Many galaxies and planetary nebulae show considerable detail due to the high contrast of the Zambuto primary. Much time can be spent examining e.g. M33 or the M81/M82 group, and M51 displays spiral structure. On double stars the Portaball behaves like a refractor (of course perfectly apochromatic). When seeing conditions allow, perfectly clean splitting is achieved on pairs like h Coronae Borealis, z Bootis and z Cancri. Star colours appear beautifully. For stars brighter than 7’th magnitude it is possible to estimate the spectral class of the star from the colour, even telling the difference between an F and a G class star. Due to this, most star clusters are incredibly beautiful in this telescope, and the number of objects showing a decent amount of detail is great. Before acquiring the Portaball, I considered lunar and planetary observation to be uninteresting. The Portaball is, however, an excellent planetary instrument, showing a lot of detail on Jupiter, Saturn and the Moon. Jupiter displays faint diffraction spikes arising from the spider vanes. If these were not present, the image would be very close to that of a high-class apochromatic refractor. Working at a power of 240x is no problem with the Portaball. Seeing conditions, however, sometimes limit the achievable resolution. Very faint stars can be detected with this telescope. From a site with good (not excellent) viewing conditions I have been able to view stars at magnitude 14.2. I believe that under the best conditions it will be possible to get close to magnitude 15. Portability and Ease
of Operation Optical excellency is not the only reason for selecting a Portaball telescope. Portability is another important factor. The telescope is easily disassembled, and the whole instrument except the truss poles can be packed in the lower OTA unit (the sphere). It can be transported in any car, by bus, train or plane (not as cabin luggage, but still not a problem). I am lucky enough to have a shield where I can keep my telescope at outside temperature. Therefore I will normally keep my telescope assembled. As such the telescope can still be carried by one hand, and I use the Portaball as an oversized, but still handy “Pronto”. It is no big deal to take out this scope for a 10 – 20 min session (e.g. to see if the GRS on Jupiter is emerging, or any satellite transits are coming up). I also keep the scope assembled when I transport it by car. When using public transport I disassemble it. From the disassembled state, 5 – 7 minutes are needed for assembly and re-collimation. An adult Portaball user will be seated during observation. Due to the free rotation of the OTA, the eyepiece will always be in a convenient position. Tracking is done manually, and after a few minutes of training, any object is followed so effortlessly that the user feels that the telescope just is an extension of the natural eyesight. At very high powers, an equatorial platform may be a desirable accessory, but up to 240x power, manual tracking is just fine. One more advantage with the Portaball: Traditional Dobs have a difficult zone near the zenith, and equatorially mounted scopes have problems near the pole. The Portaball moves freely everywhere. The only region I feel there is a problem is near the horizon. Below about 15 degrees altitude the Portaball becomes difficult to use, and it may even be necessary to tilt the base in order to get really low. Customer Service I am highly satisfied with the service by manufacturer Peter Smitka. He is truly concerned about providing the customer with the best possible product, always gives prompt answers to any question, and even after delivery of the telescope he has provided a lot of valuable advice. It is possible to specify modifications to the basic design, like a 2” focuser, undersized secondary and so on. Excellence of Craftsmanship The Portaball is beautifully made, with first class components and materials. Some amateurs have commented that the telescope “looks funny”, and when I ordered the telescope I also had a feeling that I sacrificed the “Pride of Ownership” which I could have acquired through buying a Takahashi or some other expensive brand. After having owned the Portaball for a few months, I have completely changed my view about this. I consider the telescope to be a real beauty, and it is obvious that this telescope will last for decades without any need for maintenance (except, perhaps re-aluminizing the mirrors). Final Comments The base price of this telescope is $1380. There are a few extras, however, which are recommended, but not a must. The light shroud is recommended whenever there is a chance of disturbing stray light. A laser collimator is also highly recommended, for the owner who frequently disassembles the telescope. With both these items the price gets above the $1500 limit. Anyhow it is possible to buy a Portaball, add a couple of good eyepieces and still end up with less that $1500. It is possible to get a cheaper telescope with a larger aperture than the 8-inch Portaball. It is also possible to get a high-end refractor with a lot of sophisticated features for less, or one of these computerized scopes. My recommendation is to choose the scope that gives most fun for the money. For me the natural choice was the Portaball. It is a handy “Pronto”, a high resolution apochromat and a deep-sky instrument that readily can be taken to places where the 8 inches of aperture really perform to the limit. Submitted by Inge Skauvik - inge.skauvik@hydro.com - Haavik, Norway
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