14.5 Portaball by Jarad Schiffer click to author

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1 14.5 Portaball by Jarad Schiffer click to author Background: I have been an amateur astronomer for about 10 years. I started with a 10 equatorial newtonian, then got an 18 Starmaster with GoTo, which was my main scope for 5 years (and a wonderful scope it was). Then I started having kids. The 18 could fit in my car with just me and my wife, and with us and one child. But it couldn t fit with us and two baby seats. After failing to convince my wife that one of the kids could ride on the roof rack, it was either get a bigger car or a smaller scope. I began looking for the most scope in the smallest footprint I could find, while still having top notch optics. This led me to the aptly named Portaball from Mag 1 Instruments. I had seen a Portaball several years ago at RTMC, although I hadn t gotten to look through it at the time. This scope comes with a Zambuto mirror (the same as in my Starmaster), so I knew the optics would be outstanding. The footprint is much smaller -- the whole scope fits into the sphere except for the base and the truss poles-- so instead of two 30 x30 squares, I would only have to find room for one 22 sphere. I was giving up 3.5 of aperture (14.5 from 18 ) and the GoTo, but I could still have tracking with an equatorial platform, and I was saving a lot of space (plus I wouldn t need to bring a ladder with this scope). I also liked the idea of not having to deal with Dobson s hole, since the best viewing is usually straight overhead. After talking to Peter Smitka (who owns Mag 1 and builds all of the Portaballs himself), I placed my order on April 4, Peter estimated a wait time of 10 months, although it ended up taking just a bit over 12. I got a bit antsy towards the end, but Peter promptly returned my s and was happy to chat on the phone. He even ed some pictures of the scope under construction. The scope arrived on April 15, The equatorial platform is coming from Astrosystems, and they are running behind, so it won t be here for four to six more weeks.

2 It s here! The scope arrived well-packed in five boxes: the barrel for the sphere; a box for the mirror and cell; another for the UTA, stand, and manual; another for the transport cart and miscellaneous bits (collimation laser, etc.); and the tube for the poles. Everything was in good shape. The base sphere contains two batteries to power the fan, secondary heater, and Rigel Quickfinder. These also serve as part of the counterweight to balance the scope radially. There is a larger counterweight in the bottom of the sphere, although it is covered by foam padding to insulate it from the mirror so it doesn t contribute to thermal problems. There are vent holes around the base, with a short section of tube inside the sphere to block stray light from going up into the optical path. The mirror cell is held in the sphere under three retaining blocks. Collimation bolts go down through the blocks to the cell. The mirror is glued onto the six-point cell, and there is a large fan in the center of the cell that blows on the back of the mirror. The mirror is 1.6 thick, although Peter is now getting mirrors from Zambuto for his new scopes. This should help them cool down a bit faster, and also makes the scope a bit lighter.

3 Six-point Mirror Cell with integral fan. I ran into one problem while I was assembling the scope: the three threaded rods that both hold the cell in the sphere and act as the collimation knobs were missing. I was able to cobble something together using ring bolts with nuts glued in position with Lock-Tite to adjust the length. Peter apologized for the error and shipped the bolts to me overnight, but in the meantime the ring bolts worked fine.

4 Temporary fix ring bolts for collimation. Notice the two batteries near the top.

5 The proper knobs look nicer, and are easier to reach. Once the mirror is installed, the rest of the setup is pretty straightforward. It s the same as you d have to do when setting it up for normal use. The six truss poles are identical except for one that has the wires to power the UTA. They thread onto the brass connectors on the base, and there is a ball inside the truss threads that fits into the socket of the brass connector so the truss can be tilted into the proper position. It s a quick and easy setup, and everything only needs to be finger tight to be stable. The upper end of each truss has a hole, and the trusses are aligned in pairs. The UTA is a single ring, with a three-vane curved spider. The secondary mirror is a 2.6 Protostar pyrex mirror with enhanced coatings, for 17% CO. The UTA has three bolts going out sideways, which fit into the holes of the trusses. The knobs for the bolts are held captive, so there is no danger of losing them or dropping them on the primary. The UTA is light enough to be easily held out in one hand. Once the UTA is in place, you attach the focuser plate using two captive screws. A JMI focuser is standard, although I got the Starlight Instruments Feathertouch. Once this is done, the scope is ready to collimate.

6 Brass connectors for the truss poles. One truss is attached next to it.

7 Secondary cage attached, with the focuser in place.

8 Side view of the focuser plate attachment. The square tube is the adapter between the focuser plate and the UTA. You can see the focuser adjustment bolts in the tube.

9 Three-vane curved spider with wire for anti-dew heating embedded in one of the vanes. Collimation took some work the first time, because the focuser had been knocked out of alignment during shipping. First, the focuser had to be squared to the secondary. This was done by loosening two of the bolts that hold the focuser plate to the UTA ring, then adjusting the focuser aim from left to right until the laser centers on the secondary. The secondary is adjusted up and down until the laser hits center dot. Then adjust the tilt of the secondary until the laser hits the center of the primary mirror. Finally, adjust the primary using the three collimation bolts until it reflects back onto itself. I spent a little over an hour the first time, because the focuser and secondary had to be adjusted. When I took the scope to a dark site and reassembled it, the focuser did not need to be adjusted, and the secondary tilt and primary only needed slight tweaking (which took under a minute). It holds collimation pretty well.

10 Once the scope is assembled, put the shroud over it and place the light shield on top. As a side note, the shroud is not optional on the single-ring UTA models (10 and 14.5 ). There is nothing behind the secondary without the shroud, so you absolutely have to use it or you will get light from behind the secondary going directly into the eyepiece. With the shroud and light shield in place, I had no problems with stray light, even on my fairly well-lit driveway. The shroud is held on top by a drawstring that pulls tight over the UTA, and on bottom by a bungee cord that goes over white hooks around the bezel of the sphere. I d heard that earlier models sometimes had problems with the shroud sagging into the light path, but I had no problems (even with heavy dew on Saturday night). Ready to go! Enough about setup how s it do under the stars? As I mentioned earlier, Portaball uses Zambuto primary mirrors. This one came with doc s stating 1/17.8 peak-to-valley wavefront, and a Strehl ratio. I know some people argue about how real those numbers are, but I have looked through quite a few scopes with Zambuto optics, and let s just

11 say that any problems with the view in one of these scopes isn t because of the mirror. I got the electrical package with a large fan built into the mirror cell, and the scope cooled down quite fast both nights I used it. It was giving excellent images of Jupiter shortly after sunset on Saturday while a nearby 20 with another Zambuto mirror but no fan was still boiling. Optically, the scope is excellent. On Jupiter I was able to see the GRS, a dark barge a bit to the right of it, and several festoons in the other equatorial belt. Saturn was very sharp: Cassini division all the way around, the crepe ring, both the shadow of the planet on the rings and the shadow of the rings on the planet. The lack of diffraction spikes is especially noticeable on the bright planets. M13 looked great with lots of stars resolved all the way through. M51 was showing lots of spiral structure, and there was even some in M101 (not as much as in my old 18, but still very nice). I also had a great time galaxy hopping. I had about seven galaxies in one field along Markarian s chain with the 35 Panoptic. M81 and M82 fit into one field easily with a 24mm Panoptic, as does the Trio in Leo. The contrast on the galaxies was excellent, with pitch black backgrounds from a dark site. I even stayed up late enough to catch some nebulas around 3AM. The Swan and the Veil were both low in the sky, but still looked quite nice, especially with a UHC filter. Ergonomically, the scope is a joy to use. The height is perfect for me (Peter customizes the base to your eye height, so no stepladder is needed for viewing at zenith). The ability to freely rotate the tube to any angle means no crouching and straining your neck to look horizontally into the eyepiece at lower angles. Aiming is very easy. You can move in any direction (no axes), making it easy to use even at the zenith. My wife s 14-year old cousin (who had never aimed a scope before) was finding objects by himself after using it for under five minutes (he discovered that γ Leonis is a double star, much to his delight). The combination of convenient eyepiece height and no Dobson s hole means that this scope encourages you to observe at the zenith, where the seeing is usually best. Plus, something about the feel of the motion is just cool: you want to star-hop to the next object to feel the scope move again. You can adjust the stiffness of the motion by waxing or stripping the sphere. The tradeoff is that the smoother the motion, the more sensitive the scope becomes to balance issues.

12 So, are there any drawbacks? Yes, a few. The balance issue becomes a problem with my 35 Panoptic. It will balance anywhere by itself, but only down to about 45 degrees with the Paracorr (below that and the scope starts to fall). I may play with some weights in the sphere when I use it (Peter offered to make me a weight to add underneath the insulation, and I may take him up on it after I play with it some more). Or I may just use the 35 on things above 45 degrees, and the 24 pan on the low stuff. I will also miss the GoTo from the Starmaster (no DSC s possible on this scope, although the equatorial table will fix the tracking I will submit an update when it gets here). I think the advantages outweigh these minor issues. The main reason I got the scope is for the portability, and it fills the bill. Everything except for the base and the truss poles fits into the sphere for transport. I can get the scope in the trunk with room for a suitcase or camping gear, or in one seat of the car. I can leave it assembled in my living room, and if I want to observe I just carry the base out to the driveway, then come back, take the assembled scope on the transport cart and wheel it out to the base, plop it down and start observing.

13 The focuser attaches with velcro the mirror cover for transport. The shroud and light shield also fit inside the sphere.

14 The scope with the UTA on top sits on an inner tube for transport. Plenty of room left for other stuff in the car. It can also ride in the front passenger seat.

15 In the living room, on the transport cart ready to go. So, overall I am very happy with the scope. It is giving up a bit of aperture compared to my last scope, but I think it will get used a lot more. The best

16 way I can come up with to compare this scope to the Starmaster is a car metaphor: The Starmaster is like a luxury sedan with automatic everything and a navigation system it will get you there in style. The Portaball is like a little sport convertible with a stick shift not quite as many features as the luxury model, but a heck of a lot of fun to drive. Jarad Schiffer Jaradschiffer@hotmail.com I have no affiliation with Mag1 Instruments, and my telescope was purchased through the normal ordering process. I took all the pictures used in this review. Balance Update: May 2004 I asked Peter to make some more counterweight for the scope to accommodate my 35 Panoptic plus the Paracorr. He sent me three thin circles of sheet lead, weighing 1.5 lbs each. I removed the mirror and cell, then peeled back the insulation over the counterweight (it is held on with a spray adhesive). I drilled 2 small holes with a bit that he supplied, then placed the lead circles over the original counterweight, and screwed them in place (he supplied the screws as well). Then I replaced the insulation using the same spray adhesive (again, Peter sent a can to me with the weights), and reinstalled the mirror. It took about 30 minutes to do, plus a few hours while I waited for the adhesive fumes to clear before putting the optics back in.

17 Original lead shot counterweights

18 New lead sheet counterweights

19 Insulation back in place Now when the scope is pointed at the horizon with no eyepiece or Paracorr in place, the scope takes just a light nudge to move up, but won t rise by itself. With the 35mm plus paracorr in place (my heaviest combination), a slight nudge will move it down, but it won t fall by itself. So now I can use it with any combination of Paracorr, eyepiece, or eyepiece plus Powermate that I have, and no problems with the scope rising while I change eyepieces. So although I was disappointed that it didn t come perfectly balanced, I have to give Peter full credit for working with me to get it right, and we did get it right. Click to discuss this article in the forums