October 25 ,2014:
In celebration of my 71st birthday
I bought myself a present, a TPO10RC telescope. I have been using
my SN8 since 2008 to do my imaging. Though it does a nice job at wide
field images with my SBIG STF8300C camera, the SN8 is a bear to
collimate the optics. I never really got it right. There has always
been a problem odd shaped stars. Anyway, I decided to go for a new
Scope and the
TPO10RC was my choice. It's design makes collimating the optics a breeze
compared to the SN8.
The focal ratio of the TPO10RC is f8 where as the SN8 was a f4
the field of view is about half that of the SN8 allowing me to get
closer and more details on various smaller galaxies that appear
tiny in the images made with the SBIG and SN8.
This OTA is made of carbon fiber which is suppose to be very
temperature stable as well as lighter in weight than the steel tube
scopes. Since my Atlas EQ-G is rated for 40 pounds of equipment load I
needed to keep the OTA weight as low as possible. The OTA with focuser
and guide camera pushes me close to that limit.
I opted for a 10" telescope for its greater light capturing
capability. In reading reports from others on the Ritchey/Chretien
telescope, most, that bought 8" models, say they wished that
they had gotten a 10" model. So I went for the 10" right away.
Yeah its more expensive but I think that this will be it for
You can see
that I hung the guide scope on the bottom of the main telescope to
keep the weight as close to the mount's center point as possible.
As of yet the
weather hasn't cooperated for me to take some picture but hope to get
out there soon and try it out.
Just out of
curiosity I checked the collimation of the optics on the new scope
and found that both the primary and secondary needed some minor
adjustments. Collimation looks good now but have to wait for mother
nature to cooperate for me to get some picture to actually see how good
a job of collimating the scope I did.
Still unfavorable weather conditions for checking out the
new toy. Been either cloudy, windy or raining. I guess that's the
way things go. Buy a new telescope and you have to wait a month to
try it cause mother nature throws you a curve ball.
found that then collimation of the TPO10RC is a bit more
complicated than first thought. It would appear that the
focuser is not quite perpendicular to the primary mirror.
Unfortunately the scope does not come with a means to adjust for this
misalignment. In order to correct I need a way to tilt the focuser
slightly to get it aligned with the center of the secondary mirror. To adjust for this
misalignment I've ordered and focuser collimation adapter with will allow me to
adjust the focuser to be aligned properly with the secondary mirror.
The following is a except from the TELESKOP Service web site that
describes the steps to collimate the RC using a laser.
purchased a Baader collimation laser to use in this process.
Teleskop-Service: Collimating a RC telescope
- Adjusting the focuser:
Adjust the focuser at
the collimation adapter until the laser spot
lies exactly on the secondary mirror's center mark. It can be seen
by looking into the front side of the telescope.
- Adjusting the secondary mirror:
The laser beam is reflected by the secondary and you can see the
spot on the matte screen of your laser. Now collimate the secondary
until the laser beam is reflected into the center bore of the matte
- Adjusting the main mirror:
The main mirror is collimated using an artificial or real star. The
artificial star by Geoptik is a great help here. Now defocus the
star image slightly at approx. 150x magnification. By using the
screws on the telescope's back side (push-pull-configuration) adjust
until the shadow of the secondary mirror lies in the center of the
- Final collimation:
Tilting the main mirror has
an effect on the focusers alignment. So
repeat step one "Adjusting the focuser". After this, the RC is
adjusted optimally and gives best performance on- and off-axis.
This seems the simplest method of
collimating an RC. Other methods such as that provided with the
AT10RC, which also has no way to align the focuser, has you bouncing
around adjusting the secondary and primary, which I tried with
(stay tuned for updates )