8” f/6 ED Travel Star Refractor
[ARTICLEIMGR="1"]A few words about myself... I’ve been an amateur astronomer for about 7 years now. I own many different scopes and always happy to try new and unusual ones. I’ve owned many different refractors over the last few years including anything from 3”, to 6” long and short Achromats, and 3” to 7” APO’s that I still own and enjoy. I became a little more “picky” about optical performance over the years and ended up keeping my 6” f/5 Achromat only for low power deep-sky views, and the APO’s for solar-system and double stars. I’m far from being an expert, just an average amateur astronomer. I usually observe from Mt.Pinos, which is the best spot in Southern California close to Los Angeles. The Sky gets very dark there, I think something like Mag 6 or maybe even better on most nights. M13 and M31 are easily seen with the naked eye. Plus sitting at 8300 ft. elevation helps a lot when dealing with the atmosphere.
I recently had the opportunity to use this very unique and large aperture refractor. It is made by a talented artist in Toronto Canada and sold under the Travel Star name (I will refer to it as TS in this review). It is as light and compact as an 8” (yes, 203mm!) refractor can get. At 39“ length and only 25 lbs in weight it can be used on medium size mounts visually without much effort. I used it on my GR-2XXL several times. An article advertised on Sky & Telescope magazine back in 1980, by Glenn E. Shaw from the University of Alaska, indicated that a short 8” or so telescope will show the largest number of stars in the same f.o.v, about 5000(!) stars, when used with a wide angle 2” eyepiece and pointed to the densest section of the Milky-Way from a dark site. This instrument seems to be ideal for that purpose. I have a 6” f/5 refractor that I use for sweeping the sky and was wondering how much more will I see through this fast 8” lens. I also own a large 17.5” Dob but I always setup the 6” f/5 right next to it for those wide angle rich field views.
Specifications:
ED Glass Achromat, Aspherical Doublet, Diameter=203mm, f/6, F.L.=1,200mm, EFMC multicoatings. OTA length 39”, OTA weight 25 lbs., Clement Focuser, Losmandy plate. Other focusers and mounting options are available, you can actually specify which focuser and mount you want to use it with, a nice feature.
The Mechanics:
The tube is carefully crafted in three sections, all made of Marine Mahogany, which is a very light and strong type of marine plywood that is not affected by moisture. It can be easily disassembled for transportation. It is then finished with clear lacquer for natural wood finish, a nice touch. While I’m more of a “traditional scope looking” guy, I can see a few advantages to this kind of design: 1. Easy shipping and carry–on as luggage when disassembled. 2. Handling the wooden OTA is pleasant, especially in cold weather. 3. The insulating properties of the light wood tube, eliminates any thermal currents in the tube, a concern in large refractors. It should also help keeping the inside temperature a little higher then the outside temperature and keep the lens dew-free much longer. The lens cell is exposed therefore one can use a standard dew remover heating strap with ease. I didn’t use one but I did use a flexible dew shield from an 8” SCT scope, fits perfectly. The OTA is rigid, and never needed alignment; collimation was always right on. The tube has a single knife-edge baffle installed in the rear section and the inside of the tube is covered with “Black Hole” material throughout. The BH material is some type of velvet that is so “black” that looking down into the tube from the front (see picture), you just can’t see a thing, a very important element when it comes to final image contrast. Looking into the tube through the focuser shows the same blackness without reflections. This particular tube is equipped with a 2” Clement focuser, very smooth and rigid. I understand that it is also available with other kinds of focusers, user selectable, my personal preference would have been the Feathertouch. The lens cell is adjustable by six push/pull screws. (Note: This prototype sample had a different lens cell, therefore the lens was temporarily attached to the tube by four SS screws even though the 6 push/pull screws are available too) To reach focus with a 2” diagonal and without a binoviewer I used two 2” long extension tubes, since the OTA is made extra short to focus with binoviewers without Barlows. This allows for the widest possible views at the eyepiece. The OTA is attached to the mount by user selectable methods. The best part is that you can actually hold the light OTA with one hand and secure it to the plate with the other (something I can only dream about when placing my 40 lbs 7” ED f/9 refractor on the mount, two hands are hardly enough.) One can easily forget that this is an 8” refractor!
The Optics:
Since the Travel Star is sporting a 203mm f/6 ED Doublet and not triplet lens design, I didn’t expect the color correction (CC) to be good enough for any high power views. That turned out to be only somewhat true, noticeable when it came to detailed planetary views. Spherical Aberration seems excellent, with no zones or turned edge issues as seen in the star-test and the 254 LPI Ronchi tester. The fact that this design is using an ED glass seems to help a great deal as far as color correction. The coatings (EFMC) are nice and uniform and are deep purple in color. Describing CC is very difficult so I decided to compare it to my excellent 6” f/8 Celestron Achromat by taking daytime pictures through both of an object about 300 ft away, using my Nikon D50 DSLR at prime focus (unprocessed RAW images). Both scopes have 1200mm focal length. To me, it seems that the TS has a slightly better CC, not by a large margin but it’s definitely noticeable. The TS image below is not as sharp because of heat waves affecting it more then the 6”scope under the hot afternoon sun, through the eyepiece the image was just as sharp from time to time. I think it’s pretty remarkable that the CC is at least as good as the CR150, which is a much slower refractor with a smaller aperture. Not a scientific experiment, of course, so take it for what it’s worth…
Under The Dark Sky:
Location: Mt.Pinos CA. Just before it got dark, we looked at Jupiter at x150. It was showing about 8 belts somewhat similar to the view we had through the nearby 200 TEC refractor. In the TS some purple was surrounding the planet but the disk color was still pretty natural, the TEC of course did not show any false color. When the sky got dark, the purple became a lot stronger and the planet turned yellow, as one would expect from a non-APO refractor. Seeing so many belts on Jupiter became harder but most were still visible. However, looking at stellar object such as globular clusters, Chromatic Aberration wasn’t a major issue anymore. I was using eyepieces down to 3.5mm (x342) and the view remained sharp and contrasty. M13 was resolved to the core at this high power. The TS split the double-double with ease, the individual stars of each pair had a very faint green tint to them but the view was still very sharp with the airy disk easily seen. Vega had purple around it, similar to the view I remember through the 6” f/8 Celestron refractor I still own, but with slightly less CA then the CR150. When it comes to low power, that’s where Travel Star really shines. The views are absolutely breathtaking. One can spend the whole night sweeping our galaxy using the 31mm Nagler alone. Stars are tiny pinpoints on a pitch-black background. The Milky-Way clouds look like those long exposure pictures you see in the magazines. While you never really get such view looking through the eyepiece with common telescopes, this scope rewarded us with those views. A crowd pleaser, no doubt. Familiar targets such as M8, M16, M17, M20 and others showed wealth of details with great contrast and sharpness. The Veil with the O-III filter was unreal, framing each half at a time was a treat. This is one view everyone should see at least once in their lifetime. The center part of the Vail was easy to see with some details showing. Dark nebulas are stunning through Travel Star, some look like giant snakes up in the sky. NGC 6888 the Crescent Nebula always takes me a minute to find in my 6” f/5, not so with the 8”. The difference was obvious, the 8” found it right away and I was able to see the complete round structure, something I’m used to seeing only in much larger Reflectors. No cool down issues noted with this large lens, however, I did have it setup more then an hour before using it.
Conclusion:
I only had the TS as a loaner. At the end of the adventure, I had to give it back to the owner, and it wasn’t easy. I sure will miss this mighty scope.
To summarize I would say that unless you are looking for a serious planetary refractor, this scope is using the design potential to the limit. Deep sky observers will fall in love with it instantly. The 8” TS is a very unique instrument in many ways but mainly because of the fact that you get wide angle “refractor quality” images with such a large aperture and in such a small and light package. We compared the views to a nearby 10” reflector. While image brightness was similar, the reflector couldn’t keep up with the TS in terms of contrast and sharpness. The details in the TS were much better on most objects. If you are super sensitive to CA and like looking at super bright stars and planets, the TS may not fit your bill. However, if seeing an ocean of stars, large nebulas, star clusters and galaxies does it for you, the 8” Travel Star ED will amaze you over and over again.
Oren Soffer Oct’ 2005
I recently had the opportunity to use this very unique and large aperture refractor. It is made by a talented artist in Toronto Canada and sold under the Travel Star name (I will refer to it as TS in this review). It is as light and compact as an 8” (yes, 203mm!) refractor can get. At 39“ length and only 25 lbs in weight it can be used on medium size mounts visually without much effort. I used it on my GR-2XXL several times. An article advertised on Sky & Telescope magazine back in 1980, by Glenn E. Shaw from the University of Alaska, indicated that a short 8” or so telescope will show the largest number of stars in the same f.o.v, about 5000(!) stars, when used with a wide angle 2” eyepiece and pointed to the densest section of the Milky-Way from a dark site. This instrument seems to be ideal for that purpose. I have a 6” f/5 refractor that I use for sweeping the sky and was wondering how much more will I see through this fast 8” lens. I also own a large 17.5” Dob but I always setup the 6” f/5 right next to it for those wide angle rich field views.
Specifications:
ED Glass Achromat, Aspherical Doublet, Diameter=203mm, f/6, F.L.=1,200mm, EFMC multicoatings. OTA length 39”, OTA weight 25 lbs., Clement Focuser, Losmandy plate. Other focusers and mounting options are available, you can actually specify which focuser and mount you want to use it with, a nice feature.
The Mechanics:The tube is carefully crafted in three sections, all made of Marine Mahogany, which is a very light and strong type of marine plywood that is not affected by moisture. It can be easily disassembled for transportation. It is then finished with clear lacquer for natural wood finish, a nice touch. While I’m more of a “traditional scope looking” guy, I can see a few advantages to this kind of design: 1. Easy shipping and carry–on as luggage when disassembled. 2. Handling the wooden OTA is pleasant, especially in cold weather. 3. The insulating properties of the light wood tube, eliminates any thermal currents in the tube, a concern in large refractors. It should also help keeping the inside temperature a little higher then the outside temperature and keep the lens dew-free much longer. The lens cell is exposed therefore one can use a standard dew remover heating strap with ease. I didn’t use one but I did use a flexible dew shield from an 8” SCT scope, fits perfectly. The OTA is rigid, and never needed alignment; collimation was always right on. The tube has a single knife-edge baffle installed in the rear section and the inside of the tube is covered with “Black Hole” material throughout. The BH material is some type of velvet that is so “black” that looking down into the tube from the front (see picture), you just can’t see a thing, a very important element when it comes to final image contrast. Looking into the tube through the focuser shows the same blackness without reflections. This particular tube is equipped with a 2” Clement focuser, very smooth and rigid. I understand that it is also available with other kinds of focusers, user selectable, my personal preference would have been the Feathertouch. The lens cell is adjustable by six push/pull screws. (Note: This prototype sample had a different lens cell, therefore the lens was temporarily attached to the tube by four SS screws even though the 6 push/pull screws are available too) To reach focus with a 2” diagonal and without a binoviewer I used two 2” long extension tubes, since the OTA is made extra short to focus with binoviewers without Barlows. This allows for the widest possible views at the eyepiece. The OTA is attached to the mount by user selectable methods. The best part is that you can actually hold the light OTA with one hand and secure it to the plate with the other (something I can only dream about when placing my 40 lbs 7” ED f/9 refractor on the mount, two hands are hardly enough.) One can easily forget that this is an 8” refractor!
The Optics:Since the Travel Star is sporting a 203mm f/6 ED Doublet and not triplet lens design, I didn’t expect the color correction (CC) to be good enough for any high power views. That turned out to be only somewhat true, noticeable when it came to detailed planetary views. Spherical Aberration seems excellent, with no zones or turned edge issues as seen in the star-test and the 254 LPI Ronchi tester. The fact that this design is using an ED glass seems to help a great deal as far as color correction. The coatings (EFMC) are nice and uniform and are deep purple in color. Describing CC is very difficult so I decided to compare it to my excellent 6” f/8 Celestron Achromat by taking daytime pictures through both of an object about 300 ft away, using my Nikon D50 DSLR at prime focus (unprocessed RAW images). Both scopes have 1200mm focal length. To me, it seems that the TS has a slightly better CC, not by a large margin but it’s definitely noticeable. The TS image below is not as sharp because of heat waves affecting it more then the 6”scope under the hot afternoon sun, through the eyepiece the image was just as sharp from time to time. I think it’s pretty remarkable that the CC is at least as good as the CR150, which is a much slower refractor with a smaller aperture. Not a scientific experiment, of course, so take it for what it’s worth…
Under The Dark Sky:
Location: Mt.Pinos CA. Just before it got dark, we looked at Jupiter at x150. It was showing about 8 belts somewhat similar to the view we had through the nearby 200 TEC refractor. In the TS some purple was surrounding the planet but the disk color was still pretty natural, the TEC of course did not show any false color. When the sky got dark, the purple became a lot stronger and the planet turned yellow, as one would expect from a non-APO refractor. Seeing so many belts on Jupiter became harder but most were still visible. However, looking at stellar object such as globular clusters, Chromatic Aberration wasn’t a major issue anymore. I was using eyepieces down to 3.5mm (x342) and the view remained sharp and contrasty. M13 was resolved to the core at this high power. The TS split the double-double with ease, the individual stars of each pair had a very faint green tint to them but the view was still very sharp with the airy disk easily seen. Vega had purple around it, similar to the view I remember through the 6” f/8 Celestron refractor I still own, but with slightly less CA then the CR150. When it comes to low power, that’s where Travel Star really shines. The views are absolutely breathtaking. One can spend the whole night sweeping our galaxy using the 31mm Nagler alone. Stars are tiny pinpoints on a pitch-black background. The Milky-Way clouds look like those long exposure pictures you see in the magazines. While you never really get such view looking through the eyepiece with common telescopes, this scope rewarded us with those views. A crowd pleaser, no doubt. Familiar targets such as M8, M16, M17, M20 and others showed wealth of details with great contrast and sharpness. The Veil with the O-III filter was unreal, framing each half at a time was a treat. This is one view everyone should see at least once in their lifetime. The center part of the Vail was easy to see with some details showing. Dark nebulas are stunning through Travel Star, some look like giant snakes up in the sky. NGC 6888 the Crescent Nebula always takes me a minute to find in my 6” f/5, not so with the 8”. The difference was obvious, the 8” found it right away and I was able to see the complete round structure, something I’m used to seeing only in much larger Reflectors. No cool down issues noted with this large lens, however, I did have it setup more then an hour before using it.
Conclusion:I only had the TS as a loaner. At the end of the adventure, I had to give it back to the owner, and it wasn’t easy. I sure will miss this mighty scope.
To summarize I would say that unless you are looking for a serious planetary refractor, this scope is using the design potential to the limit. Deep sky observers will fall in love with it instantly. The 8” TS is a very unique instrument in many ways but mainly because of the fact that you get wide angle “refractor quality” images with such a large aperture and in such a small and light package. We compared the views to a nearby 10” reflector. While image brightness was similar, the reflector couldn’t keep up with the TS in terms of contrast and sharpness. The details in the TS were much better on most objects. If you are super sensitive to CA and like looking at super bright stars and planets, the TS may not fit your bill. However, if seeing an ocean of stars, large nebulas, star clusters and galaxies does it for you, the 8” Travel Star ED will amaze you over and over again.
Oren Soffer Oct’ 2005
Funding Member
