DGM Opticsä OA-
Seriesä
instruments offer some of the finest optics and innovative mechanical design
utilized by any telescope available to the amateur astronomer today. Outlined here are basic procedures to
help you attain optimal performance from your OA-Seriesä
telescope.
Once you have received your
OA-Seriesä
telescope carefully unpack all components and inspect for any damage that may
have occurred during shipping. Although it is rare for damage to have occurred during
shipping, it is very important to contact DGM Opticsä so a
claim can be filed as soon as possible with the shipping company.
Depending on your model, all the
OA-Seriesä
telescopes require some assembly. The OA-4.0ä is
easiest of all the OA- Seriesä
telescopes as far as assembly and requires only that the primary mirror is
installed in the tube assembly and the split yoke is secured around the
circumference of the tube assembly. To install the primary mirror, carefully
unpack the primary mirror and remove the (3) machine screws that are attached
to the large platter. Then, with the small orientation hole in the large
platter aligned with the focuser, gently slide the entire assembly into the
tube and, using the predrilled holes in the tube attach the mirror cell and
primary to the tube assembly. Next set the tube assembly in the “Split Yoke”. Placing
the split yoke assembly around the tube assembly and securing it by clamping
the adjustable draw latch on the split yoke does this. Caution: Adjust
the draw latch only as tight as is needed to hold the tube assembly securely.
Then place the split yoke and tube assembly onto the mount struts. You can now
proceed to the alignment step.
If you have purchased the OA-5.1
ATSä, the OA-5.5ä, the OA-6.5
ATSä, or the OA-7.0ä, you will
need to attach the large base plate to the small base plate and strut assembly.
To do this, find the (2) 3/8” nuts and 3/8” fender washer attached to the 3/8
machine screw and bushing assembly. Then, remove the 3/8” nuts and 3/8"
fender washer attached to the machine screw. Next, carefully insert the
bearing/machine screw assembly on the bottom of the small base plate and strut
assembly into the bushing on the large base plate assembly. Now, place the
fender washer through the 3/8” machine screw and thread the (2) 3/8” nuts onto
the machine screw. Tighten the first 3/8” nut “finger tight” against fender
washer, then with an adjustable wrench hold the first 3/8” nut in place and
tighten the second 3/8” nut down to “lock” the assembly in position. If you
find that the mount has excessive play, repeat the procedure described above to
attain the desired motion and “free play” in the bushing/bearing assembly.
Also, note that this procedure may have to be repeated several times until your
mount has been “broken in”, or with seasonal changes in relative humidity and
temperature. You can now follow the basic primary mirror installation as
described for the OA-4.0ä and proceed to the align step.
Because of the size and shipping
weight of the OA-9.0ä the
scope and mount are shipped in a disassembled state. All necessary hardware is
included for assembly of the mount, and all wood screw holes are predrilled for
easy assembly. Also, the fiberglass tube for the OA-9.0ä is a “cut
tube” which can be disassembled for transport. Once you have assembled the
mount and tube assembly you can continue on to the alignment step.
The OA-Seriesä telescopes secondary mirrors are permanently mounted and
aligned prior to shipment and rarely require anything more than to be checked
prior to aligning the primary. Here is the procedure. First, you will notice
that a small indelible ink mark has been placed in the center of the primary
mirror. This mark provides a visual reference to the center of the primary when
aligning the secondary mirror. Using an empty film can, with a ¼ inch hole
drilled in the center and placed in the barrel of the focuser, the mark on the
primary mirror should be centered when viewed with your eye on top of the film
can. Next remove the film can and with your eye remaining centered over the
barrel of the focuser move your eye back to approximately 6 inches away. Repeat
this step at distances of 12, then 18, then 24 inches. At each step the
secondary should appear concentric and centered with regard to the barrel of
the focuser with your eye remaining centered on the optical axis as you move
farther from the focuser barrel. If it appears that the secondary is not in
correct alignment you can manipulate the secondary by carefully bending the
secondary on the brass rod that attaches the secondary to the “L” stalk the
supports the whole assembly to the interior of the tube. If you cannot achieve
a satisfactory alignment contact DGM Opticsä and I will be happy to assist you. If your secondary
mirror appears to be in correct alignment you can proceed to “part B” of the
alignment.
Next comes the easy part: the
primary. To provide a constant reference, the primary mirror alignment should
be done with the scope pointing on the horizontal looking at a white
background. Looking into barrel of the focuser, with no eyepiece, and your eye
centered over the barrel of the focuser, you should see only the primary with
no image of the secondary visible. Next, if you have a standard OA-Seriesä scope (OA-4.0ä, OA-5.5ä, or
OA-7.0ä), move
your eye slightly towards the rear of the scope, (the 6:00 o'clock position if
the front of your scope is 12:00 o'clock). If the instrument is correct in
alignment you should see a small “sliver” of the secondary mirror at the 12:00
o'clock position on the primary mirror. The key to aligning an off-axis
Newtonian telescope is in the fact that primary is actually a segment taken
from a larger “parent mirror” and it is beneficial to think of it in that way.
When looking into the focuser barrel, think of an imaginary “center line’
running through the primary from 12:00 o'clock to the 6:00 o'clock position on
the primary. This imaginary line runs from the thickest to the thinnest part of
the primary and it also points back to the center (apex) of the old “parent
mirror”. If the alignment appears incorrect, use any needed combination of the
primary mirror cell adjusters to bring the image of the secondary mirror to the
correct position on the “center line”. The procedure for the ATS scopes (OA-5.1
ATSä, OA-6.5
ATSä, and
OA-9.0ä) is
different only in that the “sliver” of the secondary will be at the 6:00o`clock
position, instead of the 12:00o`clock position. Other than that the procedure
is the same.
The star test is the final confirmation of the correct
alignment of your OA-Seriesä
telescope. The test consists of centering a bright star, beginning at low
power, and observing the in and out of focus star images, then repeating the test
with progressively higher power eyepieces. In all cases, with the star centered
in the field of view, the image should be round and concentric with no trace of
astigmatism or coma, (elongation of the star image), both inside and outside of
focus. If you find that the image is not concentric when centered in the field
of view it is usually only a matter of using the "center line"
adjuster on the primary mirror cell and moving the image to the center of the
field of view until it is correct. The "center line" adjuster is the
adjuster that is marked with the small hole in the large plate of the primary
mirror cell. Once you have established the correct alignment by star testing
you can note the visual position of the secondary "sliver" and
quickly perform accurate alignments. Also, be sure that your scope has reached
complete thermal equalization before performing the star test(s). If you are
confident that all alignment steps have been completed correctly and still are
not sure if the alignment is optimal please feel free to contact DGM Opticsä for
technical support.
Cleaning the optics should be performed whenever the
primary or secondary mirrors have an excessive amount of foreign material on
the optics, or when the optical performance is obviously degraded due to
surface contaminates. DGM Optics uses the technique describedä, but
other methods may be used if preferred.
Start by removing the primary
mirror and cell from the tube assembly. Do not remove the primary itself from
the mirror cell as the method described can be done with the mirror in place.
The (3) machine screws used to secure the mirror cell in the tube can be
removed during the cleaning process.
1. Prepare a
solution consisting of 20 parts distilled water and 1 part mild dish washing
soap.
2. Using, unscented,
plain white, bathroom tissue take 10-12 two-ply sheets and fold
into a square pad, then fold the square pad in half and set on a clean oil free
surface.
3. Then, set
aside 6-8 cotton balls on a clean oil free surface.
4. Next,
with the mirror facing up, place the mirror cell assembly under running, room
temperature water for about (1)
minute.
5. Turn the
water off and pour a generous amount of the premixed distilled water solution
over the surface of the primary mirror.
6. Then take
the cotton balls and saturate them with the premixed distilled water solution
and lightly swirl them on the surface of the mirror. You don’t
have to swirl the mixture so as to create a lot of bubbles on the surface,
agitate it only enough to see a hint of the soap in the solution. That will
usually be sufficient to remove most stubborn dirt or stains on the surface.
7. Next, with the mirror facing up,
place the mirror cell assembly under running, room temperature water for (1)
minute, except after one minute turn off the water and quickly flush the
surface with a generous amount of distilled water.
8. After the
surface has been flushed with distilled water quickly turn the mirror cell
assembly on its side to drain off excess water. Then take the bathroom tissue
pad and lightly and gently blot the remaining water
from the surface.
9. Next, using a paper towel,
carefully wipe up the water on the large and small platters of the primary
mirror cell. Avoid turning the assembly upside down, and also, avoid touching
the freshly cleaned mirror surface. Inspect and repeat procedure if necessary.
Reinstall mirror cell assembly in tube assembly.
Because
of the crucial nature of the secondary mirror alignment, it is advisable to
remove and/or clean it only if there is an excessive amount of contaminants on
the surface. To remove the secondary, loosen the hex nut/threaded rod assembly
that secures the mirror itself to the "L" shaped stalk. If you need
remove the secondary for cleaning be sure to measure the exact distance that
the second hex nut is threaded into the brass rod. That will mark the
position when the secondary is reinstalled. If possible, use cleaning methods
that allow the secondary mirror to remain in place. Try blowing the surface off
with low pressure air or wiping the surface with a soft camel hair brush and
then gently rake the surface with a bathroom tissue pad dampened with a small
quantity of alcohol or methanol. And as always, DGM Opticsä will be
glad to give technical support if needed.
DGM
Opticsä OA-
Seriesä Dobsonian
style mount offer some of the smoothest tracking and most comfortable viewing
possible with a Dobsonian mounted telescope. The optical tube assembly is set
in DGM Opticsä Split
Yokeä. The Split
Yokeä allows
the tube to be balanced and rotated for comfortable viewing of any portion of
the sky.
All
bushing, bearing and trunion parts are custom made using Teflon (TFE) and
Ultra-High Molecular Weight Polyethylene (UHMW). These materials feature
excellent friction coefficients with high chemical and temperature resistance.
The wood is a beautiful, high grade, Atlantic Birch triple coated with a clear
polyurethane finish that will last for years. The finish can be cleaned and
polished with any commercial wood preserving products any time you want to
bring back the "new finish" shine.
As for
Teflon (TFE) and Ultra-High Molecular Weight Polyethylene (UHMW) components,
they need only to be kept free of abrasive materials, which may inhibit the Alt-Azimuth
motion(s) of the mount. Cleaning these components by wiping the surfaces with a
clean cloth that has been lightly dampened with acetone or alcohol. Note:
It is recommended that chemical resistant gloves be worn when using such solvents.
Also, the vertical bushing/bearing assembly should be periodically treated with
machine oil such as WD-40, or similar products, to inhibit corrosion of the
machine screw and double nut locking assembly.
The OA-
Seriesä mount
utilizes a black anti-static Ultra-High Molecular Weight Polyethylene (UHMW)
disc on the large base plate with the small base plate/strut assembly riding on
Teflon (TFE) pads. Periodically the base plates can be disassembled and cleaned
of any debris, and then treated with WD-40 to increase the smoothness of
azimuth motion. The OA-4.0ä mount
features, believe it or not, vinyl LP records as the surface the Teflon pads
ride on.
The OA-4.0ä is now
offered with a "Teflon strap clutch". This simple, inexpensive,
device is built in to one of the struts and applies controlled friction to the
trunion bearing and prevents the tube assembly from "falling down"
when various eyepieces are used. This device requires no special maintenance.
However, a thin coat of WD-40, or machine oil, can be applied to the assembly
where the components contact, the trunion bearing, and the Teflon strap. When
additional clamping is applied, the smoothness of the altitude motion is
enhanced. Also, the "Teflon strap clutch" is available with any of
the OA- Seriesä
telescopes, and can be easily retrofitted to your scope if you need more
friction with the altitude bearing motion. Contact DGM Opticsä for more details.
1. Do not
loosen the "split yoke" draw latch with tube pointing up. Doing this
can result in the tube sliding down on the small mount platter and damaging the
tube assembly or the mount.
2. Do not
store the Standard OA-4.0ä for long periods (2+ hours) at temperatures
greater than 140 degrees
Fahrenheit. The Standard OA-4.0ä uses PVC (Polyvinyl Chloride)
tubing for the optical tube assembly and is rated for that temperature.
3. If
possible try to bring your OA- Seriesä telescope into an intermediate temperature area after observing in cold weather. This
will help inhibit "sweating" on the optics that can be harmful to
thin film mirror coating.
4. And,
Finally, Do Not Look Directly at the Sun with your OA-
Seriesä, or ANY
Telescope.