iStar Phoenix 204-6 Achromatic Refractor

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James S. McEvoy

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I have been an amateur astronomer since 2002 and have owned just about every type of telescope commercially available. These include 8, 11, and 14-inch SCTs, 4” ED apochromatic refractor, and 15” Dobsonian. Life happens and circumstances change. We ended up in rural northwestern Wyoming about 2 miles outside of a small town. It is reasonably dark at my home but not pitch black due to scattered bright lights on adjacent properties as well as sky glow to the west from the town. How to observe?

I am strictly a visual astronomer and enjoy the moon, planets, double stars, and selected deep sky objects. As I’ve gotten older, I’ve noticed that I’m less comfortable standing while observing for very long. I prefer to be seated. Hence, a large Dobsonian reflector, while tempting, was not ideal. The mount that I use has a weight limit of about 60 pounds. While that is robust, an 11 or 12” SCT would be about the limit. I especially enjoy the views through refractors and decided that the best option for more photons was a large aperture achromat.

ISTAR Optical was the company that attracted my interest. I discussed my situation and options with Ales Krivanek and settled on the Phoenix 204-6 achromat. I have never looked through a large refractor so I was keenly interested. It took several weeks for the instrument to be assembled and shipped but it finally arrived safely. It was very well packaged and fully intact. I was able to lift it myself [weight 31.1 lbs] but I enlisted some help to get it onto the mount. The optical tube is made of a white strong somewhat lighter material to reduce weight. The tube rings are well thought out, strong, and easy to adjust. The dust cover attaches to the margin of the dew shield with magnets. This means that you don’t have to slide the shield down in order to cover the objective at the end of your observing session. Nice touch.

Ales provides the excellent Moonlight Focuser, which accommodates all of my focusing needs, including the use of Powermates and binoviewers. A finder scope is not provided but that was not a major problem. I attached a Telrad to thin padding wrapped around the OT. I didn’t want to mare the finish of this beautiful instrument in any way.

How does it perform? The first thing I noticed is that 8” of unobstructed photons provide sharp stars with more vibrant colors compared to smaller instruments. I could just split Castor [separation 4.2”] into its A and B components at moderate magnification. I made a 4” mask out of metal and attached it to the dew shield magnets. With semi-apo filters, I was able to split Izar (epsilon Bootis, separation 2.8”) at high magnification but there was obvious chromatic aberration. Low magnification views of Jupiter and its moons were pleasing. Uranus showed its color but no detail on its tiny disk. For DSOs, M57 the Ring Nebula was very clear and pleasing to view with its star field.

Lunar observation is definitely possible with the Phoenix. Is there C. A.? Yes, mostly on the limbs. It is greenish or purple and varies in conspicuity and location depending on the position of my eye at the ocular.  Semi-apo filters reduce it slightly.

 

 

 To me, it is not overly intrusive, although that may be a matter of opinion. Using low to moderate magnifications, I have had delightful times studying the lunar terrain.  I would not use high magnification with this instrument.

The Phoenix provides wonderful wide field views of DSOs. Individual galaxies in the Virgo cluster were not particularly bright but it was easy to see two or more in one FOV. M64, the Black-Eye Galaxy in Coma Berenices, was faint but the core was visible. I saw the famous dust lane at 110X. M13 the Hercules globular cluster was also wonderful at low to moderate magnifications. The stars appeared fine, almost like sugar. Many stars were resolved as fine points.

 I turned my attention to some objects in Sagittarius. M22 showed a dense core and fine stars scattered out from the center. M8 the Lagoon Nebula showed the northern portion of its nebulosity, somewhat improved with an appropriate filter.  These objects are quite low in my sky and are obscured by a bright light on adjacent property. I would think that viewing them from farther south at a very dark site would yield significant improvement.

M31 and its satellite galaxies were wonderful even with the moon approaching first quarter. I’ve never had a finer view of this object. I have seen it brighter and more magnified in larger instruments but as a very good friend of mine told me, “brighter is not necessarily better.” I would love to see this with the Phoenix at a truly dark site.

The Phoenix is optimized as a low magnification, wide FOV instrument with very good contrast. Stars are sharp and fine. The brightest stars show a little false color that was not a big deal to me. [I did not mess around with out of focus viewing of bright stars]. The instrument excels at deep sky objects and surrounding star fields. This gives a different “feel” compared to high magnification views in longer focal length instruments. It does well on globular and open clusters and brighter planetary nebulae. Some emission nebulae are also pleasing. I can’t wait to see M42!  Extended objects like M31 are wonderful.

The Phoenix is NOT a high magnification instrument. I rarely use it over 100X. Therefore, it is not intended for detailed planetary work or for fine resolution of distant globular clusters or faint galaxies. You can do respectable observing of the moon. It is not good for separating tight double stars [I would advise a smaller 4 or 5” apo for that], although widely separated binaries are pleasing.

In conclusion, this is an excellent instrument for visual astronomy at reasonably dark sites. If you enjoy refractors and want to experience wide FOV astronomy, then I can heartily recommend the Phoenix. This is one that I’m keeping!

 

Jim McEvoy