3
Focus:
It is amazing how many people walk up to a solar telescope and take a quick look thru without ever
focusing. Course focus is achieved by moving the diagonal drawtube in and out (only B1200 or B1800).
Medium focus is achieved using the larger knobs on either side of the focuser assembly. Fine focus is
achieved with the 10:1 reduction (smaller knob). The fine focus is often too fine for visual use, but comes in
very handy if you are imaging. Focus so that the edge of the Sun is as sharp as possible.
Tuning:
On the side of the scope is a large black cylinder. This cylinder is the tuning system for the H-alpha
filter. Now we will describe how to bring 656.28nm wavelength on band. The black handle of the cylinder
system has a 4 start thread attaching it to the brass cylinder body. Unscrew the black handle completely and
carefully pull the piston from the cylinder. There may be some resistance and a faint pop as the air enters
the cylinder. This is normal. This has reset the system for your altitude. Carefully re-thread the handle onto
the body and engage the threads about one turn. While looking thru the eyepiece gently turn the black
handle onto the cylinder body. There will be little resistance at first, but as the pressure in the cylinder builds
the resistance will increase slightly. As you turn the cylinder you should see features come into view thru the
eyepiece. Continued turning will result in the wavelength shifting thru 656.28nm and detail will begin to
disappear. Fine-tune the cylinder for the best performance.
A few details regarding the pressure tune system. The amount of pressure being supplied to the etalon
cavity is minimal. It is the equivalent of going from -150m below sea level to about 3,000m. Or around 0.1
Bar, there is no risk of explosion. We are dealing with only a fraction of 1 atmosphere. When not in use we
recommend that you release the pressure by simply backing off the black handle from the cylinder body. If
the system unthreads completely, simply thread it back on 1 turn. It is not necessary to re-set the system
every time it is used. Re-setting may only be required if the system has been sitting for a long period of time.
Re-Focus:
When you feel you have tuned effectively, re-focus the telescope. The finer details should come
into view. Try to relax the eye while observing and let the details come to you.
Change the eyepiece:
When you have a good feel for observing at lower magnifications try to increase the
magnifications in small steps. Place an interesting artifact in the center of the field. Replace the 25mm with a
8 - 12mm eyepiece. Look thru the eyepiece and re-focus carefully. The image has dimmed slightly due to
higher magnification but the details should be easier to see. You can push the magnification as seeing
conditions allow.
Seeing conditions:
Please note that seeing conditions can affect the performance of your telescope in H-
alpha wavelength. Cloud cover, wind, humidity, and air turbulence caused by heat play a major role and can
complicate the observation of details.
Double-Stacking in H-alpha:
Double stacking is also possible with the LS80MT telescope. For this purpose there is the additionally
available double-stack module "DSII/SFPT", item number 0551395. This will be simply inserted between the
red H-Alpha unit and the LS80MT focuser. A detailed mounting instruction is delivered together with the
double-stack module.
This will reduce the bandwidth to <0.5 Angstroms. This significantly increases the contrast on the surface of
the sun, which makes much more details visible on the solar surface.
