8" f/6 Portaball
Submitted: Friday, 23rd April 2010 by Mohammed Baddah
A little background first as to why I purchased the Portaball. Having owned a 6” gso dob and a 10” Lightbridge previously, I’ve realised what I like and dislike in a dobsonian reflector more through experience than from reading. The mass-produced Asian reflectors offer excellent value for money, but there are those little frustrations that accumulate over time which no amount of modification will rectify (unless you’re a handyman). For example the movement of the scope when attempting to track an object at high magnifications, and the overly sized and poorly constructed bases.
I researched thoroughly for a dobsonian which was portable, had smooth motion (especially at high magnification), well constructed and lightweight. From all the reviews I read, the Portaball by Mag1 instruments seemed to stand out higher than the others. I saw an 8” f/6 portaball for sale at Astromart which was a little cheaper than purchasing brand new (though still quite expensive relative to the Guan Sheng’s). It cost just under $3k delivered to my door in less than a week, safe and sound. The previous owner had packaged and insulated it extremely well.
Moving along onto the features of the scope…
Portability:The scope assembles neatly into a wooden box, with the UTA sitting comfortably inside the spherical base of the scope. There is a separate section in the box for the portaball stand to be placed in. The poles are housed in a separate tube for storage, nice! The scope is more portable than the 6” gso dob and 100mm refractor I had previously, a big plus for those concerned about storage room.
The fact that it’s lightweight as well (about 15kgs the whole thing) helps allow the scope to be easily moved around, which is especially useful when having to move the scope in the middle of the night to a prime location when locating a specific object.
This feature perhaps took me most by surprise after assembling the portaball. The spherical base removes the dobsonian’s restriction of up/down, left/right movement and allows for a full 360degree revolution, making it the most pleasurable and comfortable telescope I have ever used. The eyepiece can be placed at any angle simply by spinning the portaball to your desired position. The other advantage ofcourse is it’s buttery smooth movement, a definite plus when nudging at high magnifications.
There’s an inbuilt battery inside the base to power the fan underneath the mirror (turned on by the flick of a switch) as well to send power to the UTA for the rigel finder and dew heater. No more messy cables and tripping over in the dark!
It has two handles on the side for easy handling, and I found I could comfortable pick up the whole scope from the base. The portaball assembled felt lighter than carrying the plywood base of the Lightbridge alone!
Perhaps the only disadvantage I can think of is that aesthetically it looks a little ‘odd’ at first as it resembles a large cooking pot more-so than a telescope :P
I’m no optical expert so I can’t really comment much on the specs listed on the certificate. What I have gathered from speaking to people and reading many reviews is that Zambuto mirrors seem to be world-renowned as one of the best in the world. The specs of this 8” mirror read a strehl ratio of 0.997, excellent peak to valley wavefront of 1/44.6, and at optimum atmospheric conditions, Zambuto guarantees a magnification of 50x per inch, giving a maximum magnification of 400x.
The portaball comes with a lid cover which fits snugly on top of the primary collimation screws (not on the mirror itself) for protecting the primary and there’s another cover for the secondary mirror.
Your standard illuminated 1x finder. It is charged via the inbuilt portaball battery. I’ve been accustomed to using a Telrad so it’ll take a while to adjust to the Rigel. It’s supposed to be a quarter of the weight of the Telrad.
Lumicon Green Laser:
Your standard green laser with mounting brackets and adjustable screws.
According to Mag1, the use of the helical focuser is essential for the portaball due to it’s lightweight and keeping the scope balanced on the top. It’s a low profile focuser and designed to have no image shift.
Mine was the older 1.25” version, the newer helical’s are able to accommodate for both 1.25” and 2” eyepieces, although you still can’t use a 31mm Nagler in there ? More on the focuser a little later on…
Shroud + Storm cover + light baffle:
The shroud is made from black ripston nylon and has a very nice feel to it. The light baffle is made from closed cell foam and locks into the UTA via 2 screws. It is easily stored inside the UTA when not in use. Both items are essential for viewing in areas where stray light can enter the optical path of the tube.
The portaball comes standard with a dew heater on the secondary mirror. It is charged via the inbuilt portaball battery and it’s simply a matter of flicking the switch on the UTA. I have not tested it’s effectiveness yet as I haven’t encountered any dew since purchasing it.
The secondary mirror has four screws (unlike the three screws on the gso’s) which are adjusted with the screw driver provided. I’m not too fond of fiddling with screwdrivers in the dark and had contacted Bob for some of Bob’s Knobs as replacement. Unfortunately due to the closeness of the screws, Bob said that his knobs don’t offer a real improvement over the portaballs screws as the knobs need to be positioned in a staggered manner.
The primary screws on the other hand are extremely easy to adjust thanks to the large thumb handles. The seller had provided a farlight 1.25” laser light collimator and a cats eye cheshire, which worked ok though I’d much prefer the 2” Astrosystem laser collimator for collimation as I find it’s more accurate and faster.
Galaxies (using 24mm Panoptic)
The Helical Focuser.
With previous dob’s that I’ve had the focuser has either been a pinion or Crayford style. The helical took some getting used to, however once I had I found it much easier to focus with than the Crayford, a nice surprise.
An issue I encountered was not been able to focus the 10mm Pentax and 8mm TMB eyepiece, whilst the 6mm Radian eyepiece and 24mm Panoptic were able to come into focus fine. I’m not sure if the original owner had asked for such a configuration or not, but I’ll need to contact Mag 1 concerning it.
The main disadvantage here with the portaball is that you cannot use any heavy eyepieces. The heaviest eyepiece I could use was my Pentax 10mm XW (weighing 391g). Anything heavier and the scope takes a nosedive. Apparently when purchasing brand new they can cater the scope to balance for most eyepiece you specify, no 31mm Nagler’s or 28mm UWAN’s though!
I would highly recommend this scope to anyone looking for a high quality portable reflector which is a pleasure to use. It is one of the best reflectors currently on the market and can hardly be faulted except on a few minor issues.
The only problem now is gathering the funds for a larger version!
Links and Further Reading