Your Feather Touch focuser has
Your focuser drawtube has a long 110mm (4.33”) travel. It has two scales (one on either side) that are
Because your Feather Touch focuser is so smooth in operation and moves so freely, it can only hold a limited amount of weight (generally about 1 lb.) without drifting out of focus when the focuser drawtube is not horizontal and has a significant vertical component. The focuser there- fore contains an
The brake consists of a lever arrangement within the focuser’s pinion block. Adjusting the thumbscrew under- neath the pinion block causes the lever to press a friction pad onto the pinion. This increases the torque needed to turn the focus knobs. If the thumbscrew is turned all the way in (only 1 to 1½ turns), the pinion shaft and drawtube are locked into position at the desired focus for long expo- sure imaging. Visually, partial tightening of the internal brake offers a virtually infinite range of braking force to accommodate various eyepiece and accessory weights.
A
Three focuser rotation handles and recessed finger grips in the locking ring around the front of the focuser body let you adjust the focuser rotation angle. While holding the 2” accessory adapter of the focuser steady with one hand, use the rotation handles to turn the locking ring slightly counterclockwise to unlock the focuser. Rotate the focuser to the desired new orientation. While again holding the 2” accessory adapter steady, turn the locking ring back clock- wise to lock the focuser in place at the new angle.
Your focuser drawtube glides on three stainless steel straps that mate with Teflon bearing surfaces to provide very tight yet extremely smooth motion. This design elimi- nates the need for grease between the housing and draw- tube. A greaseless drawtube prevents the collection of dirt that may eventually cause problems between these surfaces, so no routine focuser maintenance is required except for an occasional wipe down of the drawtube with a soft cloth.
FINDERSCOPE
No finderscope is provided with your
dealer for an appropriate finder if you do not already have one that is suitable.
COOL DOWN TIMES
For any optical system to give its best wavefront (sharp- est and highest contrast images), the optics must be at or very near the temperature of the surrounding air. This “cool down” time needed to reach ambient temperature varies considerably, as the temperature of the telescope must change from a typical 72° Fahrenheit indoor temperature to an outdoor temperature that can range from a high of over 100° down to 20° below zero or less.
With small doublet refractors, the cool down (or heat up) time is quick, usually less than 30 minutes. In larger refractors, or in subfreezing temperatures, it can take a tele- scope one to two hours to reach its best performance. This is particularly true with triplet refractors, where the ther- mal load of the center lens is isolated from the surround- ing air by the lenses on either side of it. This slows the transfer of the center lens heat load to the outside air.
If you’d like to shorten the wait to reach thermal equi- librium in backyard observing, place your telescope in an unheated garage for a few hours before observing. This can shorten the cool down process considerably.
Another technique for shortening cool down time in the field is to retract the dew shield to allow direct expo- sure of the lens cell and lens to the night air so they reach thermal equilibrium faster. Refractors show a noticeable undercorrection during cool down. By comparing a star’s image on both sides of focus you can determine when the images are similar and the lens is near optimum correc- tion. At this point, slide the dew shield back out to its fully extended position. This provides a quicker cool down time, and will generally still keep the lens from dewing up.
Only on the highest dew point nights will the objective form dew on the front optical surface. If you live in a high humidity climate, however, we recommend the regular use of a dew heater strip.
The best way to avoid dew forming on the lens after you bring your telescope into the house is to take your closed telescope carrying case outside with your scope, where the case can also reach ambient temperature. When you are finished observing, cap your telescope with its dust caps and place it into the carrying case. Bring it into the house and let it slowly warm back up to room temperature, then remove the dust caps to allow any trace of dew to evaporate. Once the objective is free from dew, replace the dust caps and store your scope away.
CLEANING
The best policy is not to let your lens get dirty and/or dusty in the first place. The use of the dust caps is highly recommended. However, no amount of preventative mea- sures will stop the objective from eventually collecting dust and airborne pollutants on the first optical surface.
We recommend that you do not clean the objective too often, no matter how frequently the urge to do so may hit you. A few specks of debris on the lens will not be visible in your images, as they are not in the focal plane. They don’t block enough light to measure, let alone be seen.
Depending on how often you use your scope, and the amount of pollutants in your air, you may have to clean your scope as often as twice a year, but generally no more
than that – and preferably no more than once a year. If the front lens surface becomes dusty, smeared, or shows fin- gerprints or any other surface
First, gently blow away any surface dust or particles with a clean air blower (a child’s ear syringe or a photographer’s camel’s hair brush with attached blower bulb, for example). The use of canned or compressed air should be avoided, if possible, as the propellant in the can may spit out and leave
If you want, or need, to use compressed air to remove stubborn particles, use a high quality compressed air duster (the
Moisten a ball of USP grade pure cotton with a few drops of a
Use a very small amount of liquid – not so much that the fluid could be wicked between the lenses by capillary action. Do not drip the cleaning fluid directly onto your lens. Do not, at any stage, apply hard pressure. Using a fresh piece of cotton or a
If you want to take the ultimate step in cleaning, a final rinse with HPLC grade acetone, or any
Avoid overcleaning your scope. The multicoatings on the lens are quite hard and durable. However, frequent overzealous cleaning can scratch the coatings if all the dust particles (which are often tiny flecks of windborne rock) are not removed before you start pushing a damp tissue around the lens surface. Clean your optics only when ab- solutely necessary. If you take proper care of your scope,
cleaning should rarely be needed.
COLLIMATION
Your telescope was carefully collimated prior to ship- ment to your dealer. With normal care the optics will keep that alignment permanently. However, if the telescope takes a very strong blow in shipping or while transporting it to your observing site, there is the small possibility that you may have to recollimate the lens. The lens cell has three pairs of
To gain access to the collimation screws, remove the black trim
Collimation screws
(1 pair of 3)
Lens cell
Trim ring /knife
edge baffle
removed from
dew shield
Dew shield
fully
retracted
How to
access the collimation screws
We recommend either of two collimation methods. In the first, a “Cheshire” eyepiece (available from Tectron or your telescope dealer) is inserted directly into the eyepiece holder (without using a star diagonal). The Cheshire method can be used indoors or in the field, day or night.
The dust cover is placed over the lens cell to seal the objective end of the scope and keep light from entering the optical tube. A bright light source is aimed at the open- ing in the side of the Cheshire eyepiece. You can use the light from the sky outdoors during the day. At night or in- doors, aim the light of a flashlight directly at the opening in the side of the Cheshire.
Look through the hole in the end of the Cheshire. You will see a series of faint circles of reflected light against a black background. If the circles of light are all concentric, your scope is in collimation. If the circles of light are not concentric, adjust the
The taller screw is the actual collimation screw, while