Orion Telescopes & Binoculars Short Tube 90 Rich Field Refractor
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154
It's Neato
Pros
Small, bright images, good focuser, robust body, inexpensive
Cons
false color
Recommended it?
Yes
I had seen these advertised for quite a while and hadn't been able to take a look through one, but I've finally been able to now and I must say I'm favorably impressed by this little telescope.
In this review I will cover:
Background
Description and Observations
Performance Observations
Summary
Background:
This telescope is part of a new lineage of small refracting telescopes apparently inspired by the Japanese Vixen brand telescopes (BTW, the Vixens are excellent telescopes- if one should cross your path, take a good look). These telescopes are being made in China and I am not sure how it's being done, but they are producing outstanding telescopes at rock-bottom prices.
Small "Short Tube" telescopes started appearing with the apochromatic (APO) telescopes from Astro- Physics, Televue, and Takahashi. These instruments are designed to give the maximum optical performance for their size in a small, lightweight, and robust package. These telescopes have very short focal lengths with focal ratios around f/6 to f/7 and are able to grasp large sections of the sky. They cover diameters from 70mm to around 105mm. There are larger telescopes related to these, but they essentially lose their mobility as they quickly grow in size and weight. These telescopes have calcium flourite lenses to correct for chromatic aberration, a light refraction effect which causes different colors of light to be bent different amounts so that objects seen through a telescope have artificial color halos. The only drawback to these telescopes is they are phenomenally expensive. For example, a 70mm Televue Pronto is a $950 telescope by itself. In comparison, the mighty Celestron G8 8" catadioptric telescope can be purchased with a large high performance tripod for this price (It will outperform the pronto, but this is a 45lb. piece of hardware). To go to a slightly larger telescope, such as the Televue 85mm takes the price up to $1950 (again without a tripod), and it goes up exponentially from there.
This is where Orion Telescopes came into the picture. A few years ago they introduced their 80mm short-tube refractor. The goal was quite simple- to build a compact refractor with good performance for a good price. The goal was to outperform the department store 60mm telescope by giving people bright views of the most popular observing objects. The 80mm did this and for a while it was selling so well that it took a couple months to buy one. The 80mm f/5 telescope is still available and has even recently been updated to a new version with an improved finderscope.
The Orion Short Tube series telescopes are achromatic. This means they only have correction for chromatic aberration in a more limited area of the visual spectrum than APO telescopes. In other words, the telescope is going to pay for its short focal length by increased false color effects. Depending on the viewing target, these effects can dramatically change what is seen. On dim objects such as nebulae and galaxies which are mostly visible to the human eye in blue or green wavelengths, this effect may be impossible to detect. On other objects, such as the moon, planets, and bright stars, the objects may have false color and brilliant purple halos depending on how well a telescope deals with this problem. It should be remembered that even the expensive APO telescopes sometimes show dim violet halos around bright objects. The main attraction of telescopes such as Newtonian, Schmitt, and Maksutov reflecting telescopes is they all have true-color images since reflection works the same for all light wavelengths. These telescopes pay a penalty in having some image degradation from the secondary mirror in the light path. On the other hand, reflecting telescopes are considerably cheaper to produce per amount diameter than refractors because fewer precision ground surfaces are required, and these are ground from choice materials. In the case of APO refractors, three calcium flourite lenses may have to be ground for every lens which makes it into a telescope (this is one reason they are so expensive).
Since the arrival of Orion's 80mm, several new scopes have shown up. There are several other manufacturers selling this same scope. If you would like one in gloss black, you can purchase it from Celestron. If you would prefer deep blue, Canada Telescopes sells it under a brand name called Sky Watcher. Orion needed to do something new to stay in the market and their answer was the 90mm f/5.6 short tube. This telescope has slightly larger dimensions than the 80mm but sells for $100 more and with a superior eyepiece and a mirror diagonal for astronomical use. A new version of this telescope is now available bundled with an equatorial mount for around $450.
The 90mm Short Tube hasn't had a glitch free introduction- early models had a focuser from the 80mm which actually interfered with the light path and stopped down the usable aperture to 80mm. However, something to note is Orion stands behind its products and was sure to send a replacement focuser to every customer who had one of the serial numbers with the problem. Orion informed the owners affected and immediately supplied the correct part without having to be pressured to do so.
Description and Observations:
On the front end, the telescope objective lens has the green and violet sheen of multicoated optics and has a built in dew cap/ glare shield which can be slid off to get direct access for cleaning (Note: the best practice is to take care to keep the optics clean to begin with because cleaning them will eventually wear off the coatings).
The body of the telescope is aluminum and the coat of gloss white paint is nice and uniform, though there were a couple of under-sprayed spots if you wanted to be really critical, but the dew cap covers them up. The focuser assembly is bolted right in to the back end of the tube and has a one-piece die cast housing. The tripod mount has 1/4-20 threads for mounting on any standard camera tripod interface. The focuser knobs are large and the rack and pinion focuser is extremely smooth and has little backlash between forwards and back (it is almost as smooth as the Televue action is).
The telescope has an intangible "Right" feel to it when held in the hands. It feels very solid, robust, and well balanced. The parts fit well together and the finish is well done. There are some rough spots- the mold lines and sprue attach point on the die cast focuser housing were a bit flat where they had simply been buzzed-off by a grinding wheel, but the paint was uniform and the finish at that location doesn't affect performance. My point here is the telescope looks more like a well made piece of practical equipment rather than an art object.
The layout of the telescope is practical and straight forward. The set screw for locking the focuser is right by the knobs where a hand coming off the focuser to find it in the dark can't help but find it. The finder scope is on a conveniently long stalk so you can look though it without bumping into the telescope even if there is a camera attached. All in all, the telescope is a very common-sense piece of equipment and should be instantly usable to anyone.
Performance Observations:
When it came to looking at objects through the Short Tube 90, I discovered it produces extremely sharp and high contrast images. Like most short focal ratio instruments, its images have a "More Real than Real" quality from their excellent contrast and depth caused by the curvature in the image. When focusing the telescope, images exhibit the "Image snap" where objects pop into obvious focus and have beautiful sharpness which refractors are famous for. The image quality was quite sharp on the moon, some stars, and nebula structures showed up nicely at low power.
The big performance hit is false color. The best description of this is what the moon looked like at low power. The entire edge of the moon had a brilliant yellow-green color which faded inwards to the center. Around the moon there was a vivid violet halo. In a way, the image was striking, but the problem is that this means the image color is never going to be quite right. Individual viewers will have to figure out how much this matters to them. On dimmer objects, the effect isn't so pronounced, and it might help to remember this is not a $2000 telescope. Depending on the viewing parameters, this effect could be crippling or entirely irrelevant. It should be remembered that the moon was the only target I saw where this effect was this strong, although the effect is seen to some degree on any bright object.
Summary:
The obvious comparison I found myself making was with my Celestron C90 which is a Maksutov telescope with twice the focal length of the Short Tube 90. Currently, if you are spending $450, you can purchase either the C90 as the G3 or the Short Tube 90 Equatorial with identical equatorial mounts. The C90 wins on having perfect color and a flatter field. If you want to spend a lot of time looking at the moon and planets, the C90 has a bit of an edge since it doesn't produce false image color. However, the Short Tube 90 does extremely well on deep sky objects such as nebulae and galaxies, which are dimmer. With a any given eyepiece, the Short Tube 90 will encompass twice as wide a patch of sky as the C90 and produce twice the image brightness. The C90 is about half the length of the Short Tube 90 and weighs 2 lbs. less. The Short Tube is rugged and incorporates a full 1.25" diameter focuser so the user has more selection in accessories.
The main question I have on this scope is the cost difference between it and the Orion Short Tube 80. When going from Orion's 80mm Short Tube to their 90mm Short Tube, you pay 50% more to get 1/8 more aperture and 27% more light gathering ability. At this time, Celestron (www.celestron.com) and other manufacturers such as Apogee (www.apogeeinc.com) are introducing 102mm short focal length instruments for about the same price as the Orion Short Tube 90, so it is possible there may soon be better deals to be had on this instrument. It has already dropped from $329 to $299 since it was introduced. If one looks away from refractors, there are many other 90mm instruments available for this telescope's price, so a prospective buyer could chose exactly what sort of telescope performance (near or deep space) they wanted without it affecting the price of what they were buying very much.
I find I really like the Short Tube 90. If the chromatic aberration were a little less apparent, I would have given it a 5 on the rating. I expect it could do quite well for a basic telescope for everyday use for many years. Unlike the expensive APO refractors, if this scope met an untimely end, a replacement would be relatively inexpensive compared to losing a Televue of equivalent size, much less a Takahashi (this would be a good reason to cry). I'd recommend this for deep-sky use and for the money I think it is a pretty good value. I expect it would make a fantastic telescope for a child and a good telescope for everyday use or for tucking in the trunk to take on trips as a general purpose telescope.
In this review I will cover:
Background
Description and Observations
Performance Observations
Summary
Background:
This telescope is part of a new lineage of small refracting telescopes apparently inspired by the Japanese Vixen brand telescopes (BTW, the Vixens are excellent telescopes- if one should cross your path, take a good look). These telescopes are being made in China and I am not sure how it's being done, but they are producing outstanding telescopes at rock-bottom prices.
Small "Short Tube" telescopes started appearing with the apochromatic (APO) telescopes from Astro- Physics, Televue, and Takahashi. These instruments are designed to give the maximum optical performance for their size in a small, lightweight, and robust package. These telescopes have very short focal lengths with focal ratios around f/6 to f/7 and are able to grasp large sections of the sky. They cover diameters from 70mm to around 105mm. There are larger telescopes related to these, but they essentially lose their mobility as they quickly grow in size and weight. These telescopes have calcium flourite lenses to correct for chromatic aberration, a light refraction effect which causes different colors of light to be bent different amounts so that objects seen through a telescope have artificial color halos. The only drawback to these telescopes is they are phenomenally expensive. For example, a 70mm Televue Pronto is a $950 telescope by itself. In comparison, the mighty Celestron G8 8" catadioptric telescope can be purchased with a large high performance tripod for this price (It will outperform the pronto, but this is a 45lb. piece of hardware). To go to a slightly larger telescope, such as the Televue 85mm takes the price up to $1950 (again without a tripod), and it goes up exponentially from there.
This is where Orion Telescopes came into the picture. A few years ago they introduced their 80mm short-tube refractor. The goal was quite simple- to build a compact refractor with good performance for a good price. The goal was to outperform the department store 60mm telescope by giving people bright views of the most popular observing objects. The 80mm did this and for a while it was selling so well that it took a couple months to buy one. The 80mm f/5 telescope is still available and has even recently been updated to a new version with an improved finderscope.
The Orion Short Tube series telescopes are achromatic. This means they only have correction for chromatic aberration in a more limited area of the visual spectrum than APO telescopes. In other words, the telescope is going to pay for its short focal length by increased false color effects. Depending on the viewing target, these effects can dramatically change what is seen. On dim objects such as nebulae and galaxies which are mostly visible to the human eye in blue or green wavelengths, this effect may be impossible to detect. On other objects, such as the moon, planets, and bright stars, the objects may have false color and brilliant purple halos depending on how well a telescope deals with this problem. It should be remembered that even the expensive APO telescopes sometimes show dim violet halos around bright objects. The main attraction of telescopes such as Newtonian, Schmitt, and Maksutov reflecting telescopes is they all have true-color images since reflection works the same for all light wavelengths. These telescopes pay a penalty in having some image degradation from the secondary mirror in the light path. On the other hand, reflecting telescopes are considerably cheaper to produce per amount diameter than refractors because fewer precision ground surfaces are required, and these are ground from choice materials. In the case of APO refractors, three calcium flourite lenses may have to be ground for every lens which makes it into a telescope (this is one reason they are so expensive).
Since the arrival of Orion's 80mm, several new scopes have shown up. There are several other manufacturers selling this same scope. If you would like one in gloss black, you can purchase it from Celestron. If you would prefer deep blue, Canada Telescopes sells it under a brand name called Sky Watcher. Orion needed to do something new to stay in the market and their answer was the 90mm f/5.6 short tube. This telescope has slightly larger dimensions than the 80mm but sells for $100 more and with a superior eyepiece and a mirror diagonal for astronomical use. A new version of this telescope is now available bundled with an equatorial mount for around $450.
The 90mm Short Tube hasn't had a glitch free introduction- early models had a focuser from the 80mm which actually interfered with the light path and stopped down the usable aperture to 80mm. However, something to note is Orion stands behind its products and was sure to send a replacement focuser to every customer who had one of the serial numbers with the problem. Orion informed the owners affected and immediately supplied the correct part without having to be pressured to do so.
Description and Observations:
On the front end, the telescope objective lens has the green and violet sheen of multicoated optics and has a built in dew cap/ glare shield which can be slid off to get direct access for cleaning (Note: the best practice is to take care to keep the optics clean to begin with because cleaning them will eventually wear off the coatings).
The body of the telescope is aluminum and the coat of gloss white paint is nice and uniform, though there were a couple of under-sprayed spots if you wanted to be really critical, but the dew cap covers them up. The focuser assembly is bolted right in to the back end of the tube and has a one-piece die cast housing. The tripod mount has 1/4-20 threads for mounting on any standard camera tripod interface. The focuser knobs are large and the rack and pinion focuser is extremely smooth and has little backlash between forwards and back (it is almost as smooth as the Televue action is).
The telescope has an intangible "Right" feel to it when held in the hands. It feels very solid, robust, and well balanced. The parts fit well together and the finish is well done. There are some rough spots- the mold lines and sprue attach point on the die cast focuser housing were a bit flat where they had simply been buzzed-off by a grinding wheel, but the paint was uniform and the finish at that location doesn't affect performance. My point here is the telescope looks more like a well made piece of practical equipment rather than an art object.
The layout of the telescope is practical and straight forward. The set screw for locking the focuser is right by the knobs where a hand coming off the focuser to find it in the dark can't help but find it. The finder scope is on a conveniently long stalk so you can look though it without bumping into the telescope even if there is a camera attached. All in all, the telescope is a very common-sense piece of equipment and should be instantly usable to anyone.
Performance Observations:
When it came to looking at objects through the Short Tube 90, I discovered it produces extremely sharp and high contrast images. Like most short focal ratio instruments, its images have a "More Real than Real" quality from their excellent contrast and depth caused by the curvature in the image. When focusing the telescope, images exhibit the "Image snap" where objects pop into obvious focus and have beautiful sharpness which refractors are famous for. The image quality was quite sharp on the moon, some stars, and nebula structures showed up nicely at low power.
The big performance hit is false color. The best description of this is what the moon looked like at low power. The entire edge of the moon had a brilliant yellow-green color which faded inwards to the center. Around the moon there was a vivid violet halo. In a way, the image was striking, but the problem is that this means the image color is never going to be quite right. Individual viewers will have to figure out how much this matters to them. On dimmer objects, the effect isn't so pronounced, and it might help to remember this is not a $2000 telescope. Depending on the viewing parameters, this effect could be crippling or entirely irrelevant. It should be remembered that the moon was the only target I saw where this effect was this strong, although the effect is seen to some degree on any bright object.
Summary:
The obvious comparison I found myself making was with my Celestron C90 which is a Maksutov telescope with twice the focal length of the Short Tube 90. Currently, if you are spending $450, you can purchase either the C90 as the G3 or the Short Tube 90 Equatorial with identical equatorial mounts. The C90 wins on having perfect color and a flatter field. If you want to spend a lot of time looking at the moon and planets, the C90 has a bit of an edge since it doesn't produce false image color. However, the Short Tube 90 does extremely well on deep sky objects such as nebulae and galaxies, which are dimmer. With a any given eyepiece, the Short Tube 90 will encompass twice as wide a patch of sky as the C90 and produce twice the image brightness. The C90 is about half the length of the Short Tube 90 and weighs 2 lbs. less. The Short Tube is rugged and incorporates a full 1.25" diameter focuser so the user has more selection in accessories.
The main question I have on this scope is the cost difference between it and the Orion Short Tube 80. When going from Orion's 80mm Short Tube to their 90mm Short Tube, you pay 50% more to get 1/8 more aperture and 27% more light gathering ability. At this time, Celestron (www.celestron.com) and other manufacturers such as Apogee (www.apogeeinc.com) are introducing 102mm short focal length instruments for about the same price as the Orion Short Tube 90, so it is possible there may soon be better deals to be had on this instrument. It has already dropped from $329 to $299 since it was introduced. If one looks away from refractors, there are many other 90mm instruments available for this telescope's price, so a prospective buyer could chose exactly what sort of telescope performance (near or deep space) they wanted without it affecting the price of what they were buying very much.
I find I really like the Short Tube 90. If the chromatic aberration were a little less apparent, I would have given it a 5 on the rating. I expect it could do quite well for a basic telescope for everyday use for many years. Unlike the expensive APO refractors, if this scope met an untimely end, a replacement would be relatively inexpensive compared to losing a Televue of equivalent size, much less a Takahashi (this would be a good reason to cry). I'd recommend this for deep-sky use and for the money I think it is a pretty good value. I expect it would make a fantastic telescope for a child and a good telescope for everyday use or for tucking in the trunk to take on trips as a general purpose telescope.
