| Teleport - portable quality Published in Astronomi 5, 2003 |
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| Technical data Dobson-mounted Newtonian telescope 254 mm parabolic primary mirror, f/5, 1:10 thickness 46.5 mm secondary mirror 2" focuser, 1.25" adapter Rigel Quikfinder Drawer Cooling fan, heated secondary, eyepiece heater Weight ca. 15 kg |
Optional extras Sky Commander digital setting circles Pentax eyepieces Paracorr coma corrector Laser collimator Off-axis mask Baader sunfilter (fits in off-axis mask) Extra counterweights Lightshield |
I bought my first telescope, a 90 mm Meade ETX, in 1996 while I studying at the University of Bergen. It was used as often as possible between all the clouds, and of course I soon wanted something larger and better. I searched on the net for the perfect telescope, and long had my heart set on a large maksutov-newtonian. But, this type of telescope is quite expensive, and needs a large (and expensive) mounting. For the same price I could buy a much larger dobsonian telescope. So started the search for the perfect dobsonian. I wanted something light and compact and with as good optics as possible. Then one day I came across a test of a 10" telescope named Teleport, by the meteorologist and amateur astronomer Todd Gross. He said :"..if I had to keep only one scope, this would probably be it!" This came from a man that has tested more than 50 telescopes, many of them high-end. Every mention I could find elsewhere about this telescope were exuberant.
Teleport is a one-man enterprise in Wylie, Texas, run by Tom Noe. He makes three telescope sizes; 7, 10 and 14.5 inches. What is special about Teleport is its four telescoping struts that enables the telescope to collapse into a box in a moment. The struts are four monopods from Manfrotto. The primary mirror is made by Carl Zambuto, which is reputed to make the best mirrors in the amateur community. Secondary mirror and spider are made by Protostar. This telescope was, and is still as far as I know, the lightest and most compact commercially available telescope in the world.
In the autumn of 2000 I sent my order, and paid half the base price to secure my place in the line. Even though there had never been a single advertisement for the telescope, there was already a long waiting list back then. My order was the first from outside the US. A delivery time of 5-6 months was indicated. Not surprisingly, it took a while longer - 14 long months I had to wait. In the mean time I had moved to Greece. In January 2002 the telescope came with FedEx. After paying taxes and VAT to the greek authorities I finally had the telescope! Everything survived the trip across the Atlantic. One screw had come loose from a monopod and was rattling around on the top of the mirror box, but it was easy to put back in place. The first evening was cloudy and I passed the time by reading the well-written manual and trying to collimate. It turned out the focuser was not particularly precise. The beam from the laser moved in a small circle as the focuser was rotated. I contacted Tom Noe, who sent me a new type of focuser (HC-2 from Kineoptics). This focuser is more precise, and is now standard.
Teleport has many features that are rare in other telescopes. One of the things I like most is the drawer with room for eyepieces and other accessories. A surprising amount of stuff can fit inside. The secondary mirror has a built-in dew heater, and a Kendrick eyepiece heater is supplied as standard. 6 C-type batteries (included!) in the mirror box deliver the power. Small counterweights can be attached to the back of the mirror cell or on the upper cage to adjust the balance. Friction in the altitude can be increased with two screws. The thin primary mirror is held in an open mirror cell, and with the cooling fan running it cools down fast for its size. The batteries lasted one year with frequent use of the fan. The mirror cell has nine points of support and a sling. It is easy to collimate. An Allen key for collimation of the secondary sits on the outside of the upper cage. This is typical of Teleport - everything has its place. A cover fits over the collapsed telescope, and it folds and attaches to the opened telescope with velcro. The top plate is also attached with velcro, as is the control box for the Sky Commander digital setting circles. If needed, one can leave the struts not quite extended if using an eyepiece that requires a lot of in-focus, or if using a binoviewer without a barlow.
The telescope works very well. The Quikfinder is a joy to use. In good seeing the images are sharp and contrasty. The lowest magnification with a 40mm Pentax eyepiece is 32x, and at this magnification all of M45 (the Pleiades) fits in the field of view. The highest possible magnification is most often limited by atmospheric turbulence. As a rule of thumb, a quality mirror should give sharp views up to 50x/inch (in my case 50*10 inches = 500x), and this is exactly what Carl Zambuto guarantees for his mirrors. I mostly observe the planets, Sun and Moon. My favourite magnification is 360x with a 7 mm Nagler and 2x barlow, although this is a bit too much on nights with bad seeing. In the rare cases of very good seeing I increase the magnification to 490x. One night with excellent seeing I used 900x on the Moon and Saturn, and the view was still reasonably sharp, so I would say the mirror holds up to the 50x/inch guarantee. On the Moon I can see the Hadley-rille almost any time, and several times I have seen the rille in the Alpine valley, which is only about 700 m wide. Five stars in the Orion trapezium is usually easy, and the Orion nebula itself looks wonderful from a dark location. I have not been able to spot the Encke-gap in Saturn's rings, but I believe it should be possible under extremely good seeing conditions. Teleport also works very well for observing the Sun with a Baader sunfilter.
The fast f-ratio makes the telescope rather sensitive to collimation errors, but it is seldom difficult to collimate precisely enough. Sometimes I have to adjust the collimation during the night if the temperature changes or if I knock the telescope. At low magnifications field curvature is quite obvious to me, and stars along the edge of the field of view are unsharp. This is not due to any errors in the construction of the telescope, but a consequence of the fast f-ratio. Optionally the Teleport is delivered with a Paracorr coma corrector, which also reduces the field curvature. The movements in altitude and azimuth are smooth and precise. I once tried to track a star at 1800x, and I managed without too much difficulty. The so-called Dobson hole I have hardly noticed.
After more than a year of intense usage I have found a few imperfections. The star test has a sector with soft edge. This is from the primary mirror, since this sector moves when I rotate the mirror. Possibly it is caused by a narrow turned down edge. Otherwise I think the star test looks good. The use of four parallel monopods means the telescope is not as rigid as a truss telescope. The monopods flex a bit under the weight of the upper cage when the telescope is pointed low. If the telescope is collimated when pointing obliquely it will therefore not maintain perfect collimation when pointed either horizontally or vertically. The telescope tends to vibrate or shake in windy conditions. The mirror cell should have been stiffer. Sometimes it is difficult to extend or collapse the monopods, but this is always solved with some wiggling. The light shield is a bit heavy, and requires an extra counterweight. The cooling fan causes vibrations, and must be switched off during observing.
Highly portable
I need only a minute or two to open the telescope, and one minute to close it. The telescope is light enough to be carried with one hand, at least over short distances, and is small enough to fit in the small trunk of a Toyota Yaris. I have taken advantage of the high portability, and tried the telescope at numerous locations in an attempt to find the ideal spot. It is very nice to be able to set up and collimate a 10" scope in 3-5 minutes, and then use only a minute or two to put everything back in the car.
Excellent service
I have frequently e-mailed Tom with questions or comments, and I have always received an answer in a day or two. Tom listens to his customers, and use the time it takes to make a good telescope. This has caused a long waiting list and high prices. Teleport is continually developed - small details are improved here and there. Teleport has a one-year warranty, but in practice it seems like Tom is ready to fix any problem at any time. Recently Tom started cooperating with Bray Imaging in England. The latter will make Teleport-clones for customers outside North America, and they will also produce several parts for Tom with CNC. Bray Imaging aims to make even higher quality Teleports, with Zerodur primaries, quartz secondaries, and carbon fiber struts. The secondary will still be supplied by Protostar, while the primary will be made by an English manufacturer. It remains to be seen whether the English mirror maker can match the quality of Carl Zambuto, but they certainly are ambitious; a precision of at least 1/15th wave is guaranteed! Optionally the telescope can be delivered with cheaper pyrex mirrors (minimum 1/10th wave).
Conclusion
This telescope has a good size aperture, is very compact, light, and has high-quality optics. As a visual instrument it works extremely well. It also somehow works for imaging the Sun, Moon and planets with a web camera, although the lack of tracking is a big disadvantage. However, my tracking platform makes astrophotography much easier, and removes most the of the disadvantages a dobsonian has compared to an equatorially mounted telescope. The total price of the telescope, including shipping, VAT, and customs I have not dared to calculate, but it is rather high. But for me it is worth every dollar.
Rigel Aline - cheap and good.
Published in Astronomi 3 2003 (in Norwegian)
There are a number of collimation tools on the market. They can be divided into the following groups: sight tubes; Cheshire eyepieces; laser collimators and autocollimators. Aline from Rigel is quite new in this market. This small plastic thing looks completely different from a Cheshire eyepiece, but it functions in roughly the same way and has the same area of use - which is adjustment of the primary mirror. Instead of a cutout on the side to let in light Aline has a reflective coating that is lit by the light inside the telescope. Aline works better in my Teleport than my Tectron Cheshire eyepiece. This is because in the Cheshire eyepiece there is a disk in the center that do not reflect light. Looking through the Cheshire this is visible as a black disk. With the mirrors properly collimated this causes the unfortunate combination of a black disk overlapping with the black ring marking the center of my primary mirror. On the other hand, looking through the Aline there is some "air" between the small black dot in the center of the tool and the center ring on the primary. To be fair, if my center ring was of a larger diameter the Cheshire eyepiece would probably have worked as well as the Aline.
The innside of Rigel Aline (left) and my Cheshire eyepiece (right). On each side is a graphic representation of the view through the tool when going from perfect collimation of the primary mirror (top) to almost perfect and fair (bottom) collimation. The outer grey ring is the center ring on the primary, while the black disk is the mirror image of the center part of the tools that do not reflect light. A small deviation from perfect collimation is easy to spot using the Aline, but is not visible through the Cheshire in my telescope.
Aline is easier to use than a Cheshire eyepiece in a rotating focuser. When a Cheshire eyepiece is rotated, the cutout on the side will let in a variable amount of light, and the view through the eyepiece will vary from well-lit to completetly dark. Aline, on the other hand, receveives and reflects the same amount of light no matter how it is rotated, which simplifies the collimation procedure. After dark, Aline can be lit by shining a flashlight down the front of the telescope, while a Cheshire eyepiece is lit by shining into the side cutout.
At Nils Olof Carlin's web pages collimation of newtonians is well explained. He suggests to make a field-stop for the Cheshire eyepiece that will show whether the collimation is sufficiently precise for you f-ratio. This field stop is easy to make and install in the Aline - simply cut a paper ring with the right diameter and attach it with tape.
My field-stop. If the center ring is inside the mirror image of this circle the collimation is acceptable. The reflective surface is a bit discolored after I tried to draw a field-stop with a pen.
Notice that adjustment of the primary mirror is the last step in the collimation procedure. Before this the focuser and secondary mirror must be adjusted. For those steps there are better tools than the Aline (sight tube, and/or laser collimator).
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The first filter |
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At left a defocused star and Jupiter without the filter. At right - the same with the filter. Captured with a Philips Toucam Pro webcamera, 2x barlow and 10" f5 Teleport. The Jupiter images each consist of 18 stacked frames followed by unsharp masking, while the star images are single frames. |
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I made the filter with plenty of slack to avoid any stretching. The filter degraded the image of Jupiter significantly. Details on the planet were blurred, and some light was scattered around the planet and its satellites. The image was dimmed slightly. The star test showed some pretty bad effects of the filter. I suspected some of the degradation came from the wrinkles along the edge of the filter, and decided to make a new filter with less wrinkles. The following night it was tested. |
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The second filter |
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The new filter was much better. Due to the poor seeing it was difficult to compare the level of detail on Jupiter. I could still see some scattered light around the planet. The defocused star image shows that this filter too has some deleterious effects, perhaps from what remains of wrinkles. It degrades the image enough that I never use it. It now only serves as a dust cover while the telescope is not in use. The solar filter from Baader is as far as I know made from the same material, which probably means that is is equally important to avoid wrinkles if you make your own solar filter. Update Oct 17 2002:
Polaris. Each image is the average of around 70 frames, captured with identical settings. Update Jan 14 2003: Update 5 May 2003: More startest images through the filter. The striped pattern is from the filter. It does not correspond to the orientation of a crease in the filter, so it must be inherent in the filter material. I now notice some loss of detail in good seeing when using the filter. Still I find it very useful to keep on when collimating the primary, and at all times when not observing, and during observing in bad to fair seeing. Cooldown is slowed a bit with the filter in place, but my mirror has kept clean much longer than without the filter. |
