Post by Mike on Oct 23, 2012 14:13:21 GMT -5
Istar Optical Comet Hunters
A growing interest in achromatic refractors for wide field viewing lead to the design of two “Comet Hunter” telescopes by Istar Optical. The first, a classic achromatic design of 150 mm aperture and 750 mm of focal length (F5). The second also 150 mm at F5 with the objective made of the Istar R30 glass. Most are now familiar with the R30 advanced design which reduces chromatic aberration and spot size by at least 30 percent. Scopes of this design are great for gazing directly into the Milky Way or observing DSOs. However, point it at a bright object and false color will quickly manifest itself with a halo of purple. These are not planetary telescopes. They do well at low magnification and dim objects. If you use them for this intended purpose, you will be quite pleased.
After more than a month of waiting, clear skies were predicted for Friday night. Finally, I would get to test and compare the Phoenix WFT 150 mm F5 with the Ares WFT 150 mm F5 R30. The R30 design has proven successful in longer focal lengths. The much shorter F5 design looks good on paper but until you actually get it out under the stars there always a little uncertainty. In anticipation of the night, scopes were unpacked and fitted with focusers, tube rings and dovetails.
I’ve had a number of inquiries concerning the weight of these short guys. I decided to use my Celestron Advanced Series mount better known as the CG-5 with Goto as one of two mounts for the tests and comparison. The second mount would be a Celestron CGE Pro capable of holding three times the weight of either of these scopes. The first thing you notice when picking the Ares R30 scope up out of its crate is its weight. It’s surprisingly heavy for its size. At only 30 inches long including the dew shield, you’ll be surprised when lifting it to the mount. The build quality is robust. No thin walled aluminum here. Magnesium alloy powder coated CNC machined tube, anodized CNC machined counter cell and back plate make up a scope tube that will not flex, barely react to even drastic temperature change and will last forever. Even the baffles are held in place with polished hex head screws. The black tube and color anodized counter cell and back plate make the scope very attractive (blue on the Phoenix and green on the Ares). The high index glass of the R30 makes it a little front heavy. I moved the front ring as close to the dew shield as possible. When placing the Losmandy style dovetail into the mount saddle I let it slide down to the point of resting against the safety screw head. This achieved the balance I was looking for. Inserting the diagonal and using Televue Nagler eyepieces, that really enhance the wide field viewing experience, further alleviated any balance problem. The tube rings we make are Pro style CNC machined and powder coated. The word I would use to describe is meaty. Heavy duty, very large knobs and black powder coating make these rings not only attractive but more importantly well made to hold your scope safely. We will soon be releasing medium duty tube rings to bring take a little weight off and offer a less expensive option. However, I’ll stick with the Pro style as they look good and guarantee the scope is going no where.
Routine alignment of the mounts helps kill the time waiting for proper lens acclimation. Of the stars that I used for alignment, Vega was the one I was most anxious to look at. How bad would the false color be? Reporting the amount of chromatic aberration in a review for any telescope, during star testing, is difficult. My eyes may be more sensitive to false color than the next guy. I’ve had people look through various achromatic scopes and say they didn’t notice any false color and wouldn’t have if I hadn’t brought it to their attention. On the other hand, I’ve had guys complain about false color when I thought it was minimal. So, you’ll have to rely on my judgment which I know is not very scientific. There is definitely far less chromatic aberration in the R30 scopes. Although there is a purple halo off to one side of Vega, it is far less obvious than when viewed through the classic version which exhibits a purple glow that encompasses Vega. The resulting chromatic aberration exhibited by either of these scopes was not surprising. After all, these are comet hunters and not designed for bright objects. For the rest of the night choosing and viewing targets that these scopes were made for erased any further thought of false color.
After about an hour of acclimation, I began pointing the two hunters toward several targets including M13, M29, M56, M57 and a few doubles. The Televue eyepieces included a Nagler 17 2” Type 4, Nagler 13 1.25” Type 6, Nagler 9 1.25 Type 6 and an Ethos 21 2” my goto eyepiece for many scopes. The Ethos 21 puts any scopes field to the test. How far out can you go until the stars are no longer round? This piece will quickly tell you. The Ares R30 has a flatter field by a small margin over the Phoenix classic. Not by a lot, but stars remain pinpoint further out none the less. Looking directly into the Milky Way, winter or summer, never ceases to amaze me. Thousand of points of light on a dark background will hold your attention for some time. The Ring nebulae impressed and the globular cluster M13 resolved into individual stars. Living about 20 miles outside Fort Myers and surrounded by nothing but orange groves makes for dark and steady skies. You’ll be impressed with the amount of detail these 6 inch scopes show.
I’m happy to say the little CG-5 had no trouble with either scope. I used two 11 pound counter weights on the CG-5 and one 22 pound weight on the CGE Pro. Using the short scopes on the CG-5 was a pleasure. With the legs of the tripod not quite fully extended I could still use my observing chair while viewing objects at the zenith. The mount slewed the short scopes around with minimal effort.
I like the idea of owning one of these for myself. How often do you get out of your car after work, look to the skies and decide tonight is a good night? Even with the scope mounted, I can carry the whole setup out my garage door. Since my driveway is marked for the orientation of the tripod legs, I can be setup and observing in minutes. The well engineered build and optical quality of these telescopes will give many years of great observing.
Phoenix WFT 150-5 Comet Hunter
6 inch doublet objective at F5
Complete tube assembly includes a
two speed fully rotatable Crayford
style focuser.
26 lbs with focuser and tube rings
32 inch tube length with dew shield
Ares WFT 150-5 R30 Comet Hunter
6 inch doublet objective at F5
Complete tube assembly includes a
two speed fully rotatable Crayford
style focuser.
31 lbs with focuser and tube rings
32 inch tube length with dew shield
Both scopes are currently in stock and on sale.
A growing interest in achromatic refractors for wide field viewing lead to the design of two “Comet Hunter” telescopes by Istar Optical. The first, a classic achromatic design of 150 mm aperture and 750 mm of focal length (F5). The second also 150 mm at F5 with the objective made of the Istar R30 glass. Most are now familiar with the R30 advanced design which reduces chromatic aberration and spot size by at least 30 percent. Scopes of this design are great for gazing directly into the Milky Way or observing DSOs. However, point it at a bright object and false color will quickly manifest itself with a halo of purple. These are not planetary telescopes. They do well at low magnification and dim objects. If you use them for this intended purpose, you will be quite pleased.
After more than a month of waiting, clear skies were predicted for Friday night. Finally, I would get to test and compare the Phoenix WFT 150 mm F5 with the Ares WFT 150 mm F5 R30. The R30 design has proven successful in longer focal lengths. The much shorter F5 design looks good on paper but until you actually get it out under the stars there always a little uncertainty. In anticipation of the night, scopes were unpacked and fitted with focusers, tube rings and dovetails.
I’ve had a number of inquiries concerning the weight of these short guys. I decided to use my Celestron Advanced Series mount better known as the CG-5 with Goto as one of two mounts for the tests and comparison. The second mount would be a Celestron CGE Pro capable of holding three times the weight of either of these scopes. The first thing you notice when picking the Ares R30 scope up out of its crate is its weight. It’s surprisingly heavy for its size. At only 30 inches long including the dew shield, you’ll be surprised when lifting it to the mount. The build quality is robust. No thin walled aluminum here. Magnesium alloy powder coated CNC machined tube, anodized CNC machined counter cell and back plate make up a scope tube that will not flex, barely react to even drastic temperature change and will last forever. Even the baffles are held in place with polished hex head screws. The black tube and color anodized counter cell and back plate make the scope very attractive (blue on the Phoenix and green on the Ares). The high index glass of the R30 makes it a little front heavy. I moved the front ring as close to the dew shield as possible. When placing the Losmandy style dovetail into the mount saddle I let it slide down to the point of resting against the safety screw head. This achieved the balance I was looking for. Inserting the diagonal and using Televue Nagler eyepieces, that really enhance the wide field viewing experience, further alleviated any balance problem. The tube rings we make are Pro style CNC machined and powder coated. The word I would use to describe is meaty. Heavy duty, very large knobs and black powder coating make these rings not only attractive but more importantly well made to hold your scope safely. We will soon be releasing medium duty tube rings to bring take a little weight off and offer a less expensive option. However, I’ll stick with the Pro style as they look good and guarantee the scope is going no where.
Routine alignment of the mounts helps kill the time waiting for proper lens acclimation. Of the stars that I used for alignment, Vega was the one I was most anxious to look at. How bad would the false color be? Reporting the amount of chromatic aberration in a review for any telescope, during star testing, is difficult. My eyes may be more sensitive to false color than the next guy. I’ve had people look through various achromatic scopes and say they didn’t notice any false color and wouldn’t have if I hadn’t brought it to their attention. On the other hand, I’ve had guys complain about false color when I thought it was minimal. So, you’ll have to rely on my judgment which I know is not very scientific. There is definitely far less chromatic aberration in the R30 scopes. Although there is a purple halo off to one side of Vega, it is far less obvious than when viewed through the classic version which exhibits a purple glow that encompasses Vega. The resulting chromatic aberration exhibited by either of these scopes was not surprising. After all, these are comet hunters and not designed for bright objects. For the rest of the night choosing and viewing targets that these scopes were made for erased any further thought of false color.
After about an hour of acclimation, I began pointing the two hunters toward several targets including M13, M29, M56, M57 and a few doubles. The Televue eyepieces included a Nagler 17 2” Type 4, Nagler 13 1.25” Type 6, Nagler 9 1.25 Type 6 and an Ethos 21 2” my goto eyepiece for many scopes. The Ethos 21 puts any scopes field to the test. How far out can you go until the stars are no longer round? This piece will quickly tell you. The Ares R30 has a flatter field by a small margin over the Phoenix classic. Not by a lot, but stars remain pinpoint further out none the less. Looking directly into the Milky Way, winter or summer, never ceases to amaze me. Thousand of points of light on a dark background will hold your attention for some time. The Ring nebulae impressed and the globular cluster M13 resolved into individual stars. Living about 20 miles outside Fort Myers and surrounded by nothing but orange groves makes for dark and steady skies. You’ll be impressed with the amount of detail these 6 inch scopes show.
I’m happy to say the little CG-5 had no trouble with either scope. I used two 11 pound counter weights on the CG-5 and one 22 pound weight on the CGE Pro. Using the short scopes on the CG-5 was a pleasure. With the legs of the tripod not quite fully extended I could still use my observing chair while viewing objects at the zenith. The mount slewed the short scopes around with minimal effort.
I like the idea of owning one of these for myself. How often do you get out of your car after work, look to the skies and decide tonight is a good night? Even with the scope mounted, I can carry the whole setup out my garage door. Since my driveway is marked for the orientation of the tripod legs, I can be setup and observing in minutes. The well engineered build and optical quality of these telescopes will give many years of great observing.
Phoenix WFT 150-5 Comet Hunter
6 inch doublet objective at F5
Complete tube assembly includes a
two speed fully rotatable Crayford
style focuser.
26 lbs with focuser and tube rings
32 inch tube length with dew shield
Ares WFT 150-5 R30 Comet Hunter
6 inch doublet objective at F5
Complete tube assembly includes a
two speed fully rotatable Crayford
style focuser.
31 lbs with focuser and tube rings
32 inch tube length with dew shield
Both scopes are currently in stock and on sale.
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