Photos courtesy of StarStructure Telescopes
I’ve been an avid stargazer for about 8 years,
the term “amateur astronomer” to me, means some that contributes
to science of astronomy on an amateur level. I definitely don’t
do that. I just truly enjoy viewing though telescopes. When I got
into the hobby there wasn’t many choices when it came to the
Truss Tube Dobsonian. Now a days there’s probably over 20 different
manufactures all claiming to build a better Dob. Making a choice on
a truss scope can be a tuff one. I spent time researching many of
the manufactures and found that most use the same materials, optics
and components, so what it really came down to was the telescope it
self. Starstructure Telescopes, fabricated by Mike Zammit, offered
a very attractive, all aluminum, alternative to the wooden truss telescope.
After talking to Mike a few times, I decided to acquire
a 16” F4.5 with Bob Royce optics. Other options included the
Servocat Goto system with the Argo Navis digital setting circles and
mirror cell transport box. While my scope was being built, Mike sent
numerous e-mailed photos showing the scope in various phases of fabrication.
I was very impressed with the fact that Michael manufactures all the
components for the structure in his shop. We had several phone conversations
regarding some size issues that I had in order to load the scope into
my mini van. Mike was very willing to make the changes at no extra
cost. After a 5-month wait, the scope arrived in three well built
wooden crates. I unpacked the scope and inspected all the parts. The
scope was very well packaged as all the components arrived without
a scratch.
Assembling the Scope
Included with the telescope, are two assembly manuals
one for the Goto System and one for the telescope. In addition, two
CD disks for the Servocat goto system and the Argo Navis digital setting
circles are supplied. The goto assembly manual is marked “read
this first”. The Servocat interface and supplied 7-amp hour
battery need to be installed in the rocker box before assembling the
telescope. The Servocat interface is installed through a convenient
slot in the side of the rocker box. All the wiring for the drive motors,
encoders and power supply come installed from Starstructure. The wiring
is very neatly and securely run though the rocker box and all plug-ins
are clearly marked for a quick and simple install. No spaghetti!
Assembling the scope is straightforward. First the mirror
box is placed into the rocker and the remainder of the goto system
is installed. This consists of the altitude encoder, which comes with
the upper wiring harness mounted to the encoder bracket. Next the
altitude drive cable must be wrapped around the drive bushing on the
altitude motor and clipped onto the engage lever located on the top
of the altitude bearing. The altitude bearing has the center hole
with a setscrew pre drilled for the encoder so it’s a simple
push in and tighten. Wrapping the altitude drive cable around the
drive bushing and attaching it to the spring on the engaging lever
takes some getting use too. It’s not an easy task at first,
but seemed to get easier after I did it a few times. Next, the Argo
Navis mounting bracket is installed on the altitude bearing and the
Argo DSC is held in place with Velcro. All the wire plug-ins from
the DSC to the Servocat interface are also neatly run and located
in easy to reach locations.
From here, the Truss Tubes are installed and have to
say it’s of the finest truss assemblies I’ve ever seen.
There are four sets of two that are connected at the top with a triangular
bracket that allows one truss to pivot freely. The other truss is
held solid with a setscrew. This is nice for transport and storage,
as they are collapsible. At the top of each connection bracket there
is a machined slot for the front end assembly to fit in. The lower
truss connection is done with a slot that slides over the thumb bolts
located on the top of the mirror box. After all four truss assemblies
are installed, the slots for the front end connection are automatically
in perfect alignment for the front end to be installed. Another nice
feature is the fact that after you install the trusses and drape the
light shroud over them, the scope is balanced, which makes it very
easy to install the front end at a comfortable height. This truss
system proved to work very nice as the front end literally fell into
place. With the OTA assembled, the next step is to install the primary
mirror and cell. The mirror was shipped in its original box from Bob
Royce Optical and the mirror cell was shipped in the mirror transport
box. I was one of the first to get the new Solid Edge Sling cell as
Mike calls it. The mirror cell looks like a million bucks. It is very
well manufactured and the pivot points for the crossbars and triangles
are on machined balls that move smooth and friction free.
To install the primary you flip two hold-down tabs located
on the top of the mirror cell, place the optic on the cell points
and push into the aluminum sling. This cell is not to be confused
with conventional sling cells. It uses that same basic design as solid
edge-mount cell but the wiffle tree mirror supports are replaced with
a thin metal sling that sits near the center of the mirrors edge.
Like a conventional sling, it supports about 40 percent of the mirrors
diameter. The mirror and cell fit into the mirror box like a glove.
There are two bolts on the bottom of the cell frame that lineup with
holes in the mirror box, you simply cannot make a mistake. After the
cell is in position, the four thumb bolts that hold the cell into
the mirror box lined up perfectly.
With the scope fully assembled, I found it to be very
well balanced in altitude and manual movement was very smooth on both
axes. Collimating this scope was very easy. The secondary was slightly
out of collimation in rotational, but axial and angular were right
on. Turning only the bottom two collimation bolts does the primary
mirror adjustment, the top bolt is locked in place. This seems to
be an accurate method to collimate the primary as I was able to stack
the center spot in the autocollimator quickly. I checked collimation
in three positions 30, 60, and 90 degrees. I could not notice any
movement in the Cheshire but the merged center spots did move slightly
out in the autocollimator. The scope stayed well within collimation
restrictions for this focal length.
Last, the location and time were needed to be programmed
into the Argo Navis DSC and plugged in to the Servocat interface.
With the scope completed I really had to take a step back to check
it out. It really is one of the nicest looking commercially built
Dobsons I have seen. The scope definitely has a quality ATM look to
it. Everything is perfectly placed and the attention to detail is
outstanding.
First Light
First light took place in my driveway, I wanted to better
acquaint myself with the telescope and goto system before taking it
out to a dark site. My first test was to simply drop the scope on
the ground and do a quick two star alignment to see how accurate the
goto system was on the fly. The Argo Navis DSC needs to have the OTA
initialized in a user designated position before doing the reference
stars, I chose vertical. Then I did a quick two star alignment not
necessarily taking care that they were centered in the eyepiece, just
close. I got a warp factor of -.6, engaged the drives and off it went.
With this level of accuracy, I was very impressed with
the goto systems performance. The scope put almost every object in
the field of a 27mm Panoptic. Those that did not come into that field
fell just outside. The spiral search feature in the Servocat pretty
much solves that problem as it makes the scope do a small or large
spiral until you see the object in the field. On this test the system
held objects in the field of a 13mm Nagler 140x for about 15 to 20
minutes depending on what part of the sky it was pointing too. Objects
close to the initial guide stars tracked much better and held in the
field for over 30 minutes. My next test was to do a very accurate
star alignment. I started by checking and leveling the rocker box
on my driveway, next I used a level to do the vertical initialization,
and a 9mm reticle eyepiece for the two star alignment. I got a warp
of 0.0 and now the scope placed every object very close to the center
of the 13mm. Most fell inside the field of a 9mm. Tracking accuracy
was impressive keeping objects in the center of a 9mm for 30 minutes,
longer if I wanted to wait. I feel this scope, along with the Servocat
goto system, would be well suited to do short to moderate imaging
and with a field derotator, who knows.
Seeing was not very good maybe a 5-6 but I did check
out Jupiter showing very nice crisp detail with the 7mm at about 260x.
More then that the night simply would not hold. I also looked at the
double-double in Lyra and was able to split it clean with the 9mm
at around 203x. Antares was an easy split with the 9mm. Globs, at
high power, like M13, M3, and M5 all resolved to the core and showed
nice dark backgrounds, considering the light polluted skies I was
looking through. For kicks, I put a 3mm with a 2X Barlow 1220x, just
to check dampening and smoothness of tracking. I did notice more damping
at the zenith, then at let’s say the 70 to 30 degree ranges.
Judging damping by the rap test I would say about 2 seconds at the
zenith and under 1.5 at lower altitudes. Judging the scope in normal
use, I mean, with a goto system you really don’t touch the scope
except to focus, it was almost immediate.
The scope came with the standard JMI DX3 focuser. I
wish I got the Feather Touch option, this would have made focusing
at high powers much better. Tracking was absolutely jitter free at
any power, very smooth. Before calling it a night I wanted to check
the scope out in manual mode. I disengaged the drives and did some
star hopping. The scope moves very nice in azimuth but did notice
a little sticking in altitude. I later found this to be caused by
the drive cable slipping on the drive bushing. When the altitude drive
cable is removed from the drive bushing the feel of altitude movement
is very smooth. With the scope at 800x I was easily able to maneuver
and hold objects in the center of the field, even at the zenith.
As usual when you buy a new scope the weather never
seems to cooperate. It was some time before I got the scope out to
a dark site.
After almost 2 months I was finally able to get the
scope out. I arrived at my viewing site with little daylight and have
to say, having a scope that sets up quick and easy is a relief, no
tools to grab or loose hardware to deal with, the wiring is already
on the scope just and needs to be plugged in. The scope was setup
and collimated within 15 minutes. At nightfall I rechecked collimation
and needed to tweak it a bit. The seeing was about 6-7, transparency
about 7, typical for summer weather.
I began the night with some low power, wide field views.
Star images were pin point to the edge of the field with nice jet
black backgrounds. Objects like M8, M17, M20, and M27 showed excellent
contrast and detail with the O3 filter. M22, my favorite globular
next to Omega, showed those tight, little, faint stars glistening
in the background, magnificent! M51 easily showed the connection to
the companion. The Veil, showed excellent contrast and impressive
structure. A friend that was with me claimed he was able to see the
central star in M57 but I honestly couldn’t see it.
Unfortunately the only planet up at the time was Jupiter
and it was getting low in the west. I was able to do some high power
views at around 406x and showed nice crisp detail. I did notice a
small hint of tube currents while viewing Jupiter at higher powers
around 600x. Another option that I wish I got was the dew system,
the secondary started to dew up around 2am and the Telrad long before
that. The primary did stay dry all through the night. The remainder
of the night was spent going to everything and anything, really putting
the system to the test. From opens to globs, nebulas to planetaries,
in every case images where excellent and the scope performed flawlessly.
The 7 amp hour battery never showed weakening but the supplied batteries
in the Argo Navis went dead around 3am. I think they were just old.
Before calling it a night I rechecked collimation and it was right
on.
In Conclusion
If I had to nit-pick, I would say that because of the
painted structure you need to be careful when loading and assembling
this scope. I did manage to scratch the mirror box when putting it
into the rocker. Although the scratch isn’t really noticeable
and the scope does come with a bottle of touch-up, I guess it’s
like that first parking lot dent you get in a new car, it just irritates
you. The install of the altitude drive cable could use some improvement.
If you’re like me and need to remove the mirror box in order
to load it, you have to do this every time. I must point out that
it is very easy to take the cable off but, just a little difficult
to put on. The mirror box might benefit from some vent holes in the
top or a small fan to remove the tube currents more quickly. Overall,
I have found this scope to be an excellent performer. It is an easily
assembled, very accurate structure with excellent optics. In closing,
I don’t think that I would have been able to purchase a better
telescope. Maybe one with a slight edge optically but I don’t
think I would have been able to get one better mechanically. When
it comes to optics I feel it goes two ways, one, how much money your
willing to spend and two, what opticians are working with a given
scope builder. When it comes to the structure, it is all about the
person or persons building them. Mike is a very courteous person to
deal with and went out of his way to ensure I got what I needed.
|
