Celestron Power Seeker 70 mm Refractor
2006-06-15
Figure 1. The Celestron Power Seeker
2
70 mm F/13 refractor: overall it's an interesting looking telescope.
Introduction
A small aperture, long focal length refractor was the
standard beginner's telescope for many years. There were a few good models, as well as many poor quality
ones that promised magnifications of hundreds of times. Common advice was to stay away from
those telescopes promising very high magnifications, and instead buy from a
reputable manufacture. For this
review I purchased a beginner's 70 mm refractor (shown in Figure 1) that is
made by a very well-known manufacture.
However, Figure 2 shows that in this case they also promise 675
power! The goal of this review is
to see how well the Power Seeker lives up to its promise.
Figure 2. Here we have a reputable manufacture
promising a rather high magnification.
Carrying Case
As shown in Figures 3 and 4 the telescope comes in a fairly
nice cloth case. There are Velcro
straps to hold everything in place.
It is a tight fit however, and there is not much to keep the tripod from
scratching the optical tube.
Figure 3. The telescope comes in a rather nice
cloth carrying case.
Figure 4. Everything you need is included, but
how good is it?.
Optical Tube
The tube is extruded aluminum and is very unusual in that it
has a square cross-section. The
"Celestron" lettering, shown in Figure 2, is painted on. On the inside (Figure 5), the tube is
flat black with a single baffle. A
nice touch is that the lens cap has a string tether to keep it from getting
lost. The lens cell is made from
plastic and is not adjustable.
However, because of the large focal ratio (F/13) the lack of collimation
adjustment should not be a big deal.
Permanently attached to the tube is a base for mounting to a standard
photographic tripod.
Figure 5. There is a single baffle in the square
tube. There is also another baffle
in the focuser tube.
Focuser
The focuser (Figure 6) is made entirely of plastic but is
surprisingly smooth, mostly because of the lack of sticky grease common in
cheap telescopes. There is also a
built-in compass in case you become lost while observing (or you have trouble
locating Polaris). Unfortunately,
this particular compass didn't work properly. The diagonal is integral to the focuser mechanism and is not
meant to be removed. It has a
clever rotating design with several locking detents as shown in Figure 7.
Figure 6. The rack-and-pinion focuser is made
entirely of plastic. Note the
built-in compass.
Figure 7. The diagonal allows the eyepiece to be
rotated to several positions. The
position shown here allows you to observe while lying on the ground - perhaps
after a few too many cool ones.
Finder Scope
Included is a small finder scope (Figure 8), which has a
decent helical focuser. There is a
rather clever pivoting mount. Alas, this finder has some of the worst optics I
have ever looked through.
Figure 8. The finder scope has an interesting
mount. Its optics are awful.
Mount & Tripod
The mount (Figure 9) is similar to a standard photographic
tripod. The legs are made from
very thin aluminum and have pointed feet.
The spreader bars (Figure 10) and eyepiece tray (Figure 11) are nicely
designed. Overall the tripod is
lightly built but is adequate for low power observing.
Figure 9. The tripod uses a photography-style of
mount.
Figure 10. The spreader bars are nicely designed.
Figure 11. An eyepiece tray attaches quite easily
to the spreader bars.
Accessories
Included with the scope is a small cloth case for the eyepieces
(Figure 12), which is slightly too small to be used easily. Each eyepiece also has a nice plastic
tube to keep it clean. Thrown in
(Figure 13) is a copy of "TheSky".
Also included is a thin paper manual.
Figure 12. Eyepieces, lens cloth, and a barlow
come in a separate carrying case.
Figure 13. A CD of Celestron's "TheSky" was
included..
Shown in Figure 14 are the two eyepieces and a 3X
barlow. The barlow is made of
plastic and weights only a few grams.
The eyepieces are 20 mm and 4 mm.
Figure 14. Two eyepieces and a barlow are
included.
Performance
In use it was immediately apparent that there is a serious
problem with the optics. Figure 15
shows a typical image: there is a haze that dramatically reduces image
contrast. Consequently, there is
no obvious in-focus position.
Figure 15.
This image of Saturn were taken
with a Canon A70 digital camera, 2X TAL barlow, and a Televue13 mm
eyepiece. It was purposely
overexposed to better illustrate the haze that appears in images.
It was noted that the diagonal's prism was very small and
blocked light going to the eyepiece.
By removing a set screw, the entire diagonal could be removed. The focuser tube is a non-standard
size, so I made an adapter from a piece of plumbing. Using a 13 mm Televue eyepiece and no diagonal improved
things. However, a star test
showed a generous amount of spherical aberration. I was, with difficulty, just able to resolve Jupiter's major
cloud bands. There was also a
serious mechanical problem with the lens cell. It turned out that the lens cell was held in place with a
bit of glue. It fell off during
first use as shown in Figure 16.
Figure 16.
The lens cell was only glued in
place and fell off during the first use.
The tripod was shaky but would be acceptable for use with
the 20 mm eyepiece (45X). It was
sometimes difficult to reach the tripod levers while looking through the
eyepiece. The entire telescope is
very light and is easy to move around.
Conclusions
Looking at this telescope, I got the impression that
considerable thought went into its design. If its optics had been better, it may have been a reasonable
choice. Unfortunately, the optical
quality was surprisingly bad: a long focal ratio refractor is normally quite
forgiving of optical defects. For
example, the old 60 mm department store refractors (like the Carl Wetzler
reviewed on CloudyNights) had
better optics than this one.
This particular example was terrible at 45 power.
In the end how well does it meet its promise of 675 power?
Both optically and mechanically it would be unusable at 675 power. In conclusion, the old advice stills
hold: if a telescope promises very high magnifications, then consider another
model.
