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Orion SkyQuest XT4.5 Dobsonion Reflector



My girlfriend wanted to buy her 7-year-old nephew a telescope, and asked my opinion about what to get. I suggested that she rule out the small refractors she was considering, because I do not have good memories or good experiences with these kinds of instruments. They are typically shaky and suffer from mediocre (at best) optics. Though I had no pervious experience with Orion Dobs, I felt sure that the XT4.5 would be a better choice, especially for the intended 7-year-old budding astronomer.

The telescope was shipped directly to the nephew's family, in Colorado, and we were present for the opening, assembly, and first light.

Assembly was easy (missing three screws for the feed from the box, but suitable substitutes were easy to find). Overall, the finished product is quite attractive, very well made, and really cute.

Under the Stars

This is an easy telescope to use. It has a rock solid mount, which moves easily, and is perfect for small observers. The uncommon correct image finder is to my thinking, a good choice. The small size means that you can use both eyes (one looking through, one looking along the edge at bright stars) to quickly find your target. It is also quite sharp across its field. The 7-year-old nephew had no difficulty locating and pointing to bright objects. The low mount made it possible for him to sit or kneel for all of his observing. He was (in his own words) "Cruising" comfortably within minutes of first use. The focuser is 1.25". Its tolerances are good, so there is no slop, and it focuses smoothly. It was even able to support my 12mm Televue Nagler. I think that with the standard 1.25 eyepieces that this scope will probably be used with, this focuser will be fine. There is a small navigation knob at the front bottom of the tube that I have read about in other reviews, where it was considered perhaps questionable, however I will be quick to point out the my 7 year old observing partner's hands almost instinctively went for it when he was moving the tube.

Optics

Incredible (on this unit, anyway). They were astonishingly good. I surmise that the primary is spherical, as the Orion catalog lists a component 4.5-inch f/8 mirror for home-builders, but this mirror star-tested almost perfect. Mirrors were really smooth, no zones or turned edge, and better than 1/6 wave, maybe even 1/7. No kidding. A small secondary (maybe 1", but not measured) aids in making the in-focus airy disk clean and sharp. Images were very contrasty. Stars were perfect little points across the field using the supplied very high quality 25mm Plossl. The 10mm Plossl was also quite good. I applaud Orion for including what was obviously a carefully considered set of good quality eyepieces, offering good views in both of the sweet spots.

We were only able to do lunar high-resolution work, and the small scope performed exceptionally well. The f/8 focal length actually works out quite well in this scope because it allows you to get reasonable magnification without having to go to extremely short focal length eyepieces or Barlows, again making this more user friendly for the intended age groups.

Under the exceptional high altitude skies near Estes Park, Colorado, the little XT4.5 easily reeled in just about every major Milky Way target, including Logoon, Triffid, and Swan Nebulas (All VERY well seen) M11, and M7. All targets were WONDERFUL in this small scope. I had my own 100mm f/5 refractor close by for comparison, and frankly, the XT4.5 was in a totally different league. Optically, it was a FAR better performer than my short refractor on every kind of object I observed.

I tried several of my own eyepieces with good result. Most of my longer eps are 2", so I was limited to using a Televue 15mm Plossl (perfect in this scope), 12mm Nagler (Awsome!!!) and 8mm and 5mm Radians. The mirrors in this scope were more than up to the task. 8mm Radian on the moon was fine, showing clean resolution. The 5mm Radian (180x) provided airy disks that looked as good as those from my MN61 (which is also 900mm focal length, so that makes for similar magnification). Contrast was very high. Again, the small secondary probably makes this happen.

Seriously… This scope would challenge (actually, I think "beat" would be a distinct possibility) most 4" achromatic refractors that I have viewed through in the past. The optics were that good. I think we observers tend to overlook the performance capabilities of smaller (4" to 6") long focal length reflectors. The XT4.5 hits that perfect balance between reasonable field and reasonable magnification. After looking at the wild prices being asked for 4" refractors today, I am surprised that someone hasn't come to the market with maybe a 5" f/7 reflector with dielectric coatings on the primary and secondary to boost reflectivity and contrast that would challenge these high priced refractors.

The real measure of Orion's success with this design was the intensity of my young observing companion's enthusiasm. He quickly mastered the scope, and it was only when I admitted that I was getting chilly that he also conceded that he would go inside with me to get our coats.

If you have read any of my other reviews, you will know that I am a tough critic. I tend to be very quick to point out faults, or areas where I think a product can be improved. I have none to mention for this telescope package. It is, in a word, perfect.

p.s.
Notice that I did not mention price or attempt to qualify my comments by saying something like "This scope is a bargain at $$$". To make that qualification would detract from my opinion of this scope. In my opinion, there is nothing in the marketplace that even comes close to offering the overall combination of excellent optical performance, usability, stability, good design, and well thought out packaging that is being offered here by Orion. They have done astronomy a GREAT service by making such an incredible telescope package available for our younger/smaller observers. That it happens to be inexpensive is only to their further credit.


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