Orion Optics OD150 User manual

Owners manual for models:
OD150, OD200, OD250, OD300, OD350 and OD400
Contents
1 Introduction
2 Main parts of telescope
3. Model differences
4. Assembly
5. Checking things
. Collimation
7. Using the telescope
8. Care and Maintenance
9. Accessories and upgrades
Orion Optics UK Ltd

Thank you for buying one of our Dobsonian range of telescopes. The following will give you all the
information you need to allow you to assemble, use and, maintain your telescope. If you carry out the
procedures correctly the telescope will give you many years of faultless usage. Please take note in
particular of the details on care of optics, if these notes are ignored or not carried out properly, damage
to the optical coatings could result. Please read through this document before commencing assembly
of the telescope, familiarise yourself with the names of the major components. And finally, when
assembled, above all, enjoy it.
This section will show you the main parts of the telescope and their function within the telescope.
Nearly all the parts on all the range have the same name and function but, because of differing model
sizes, the actual shape of the part often varies.
Shown here is a typical model with most external components labelled. Certain items are shown in
greater detail.
Introduction
Main Telescope parts

TYPICAL DOB ONIAN MODEL
Fig 1

Apart from the obvious difference of aperture and physical size and shape, all the telescopes from the
OD150 up to and including the OD400, are remarkably similar. Differences occur mainly in the
technical specifications between the standard models and the de-luxe models.
The main areas of ‘visible’ differences are:
Finder scope. Standard are supplied with a 30mm aperture finder, De-Luxe with a 50mm finder
but both work off exactly the same principle.
Focuser. Standard are fitted with a rack and pinion 2” focuser (150mm models use a
31.7mm focuser) The De-Luxe utilises a 2” precision Crayford focuser.
Both the above two items are covered in more detail later.
Differences which cannot be readily seen until you begin to use the telescope:
Optics. Standard models are supplied with our normal coatings, De-Luxe models have our
hi-tech Hilux high reflectivity coatings applied to both mirrors. This typically
transmits around 25% more light to your eye than standard telescope optical
coatings. 1/4PV wavefront optics are fitted to the standard models and 1/ PV to
De-Luxe models. With the De-Luxe models, you should also have a Zygo print out
of data of the telescope on optical test.
You may have requested and had some additional equipment added to your telescope, this is not
covered in this manual.
Model differences

DOB ONIAN BA E ECTION UNA EMBLED
Fig 2
To assemble the base choose a hard, flat surface. Do not try to assemble on a carpeted or similar
surface as the mount will not fit squarely together. First of all, fix the back panel to the base assembly
with one of the assembly screws, use the supplied Allen key. DO NOT TIGHTEN the screw at this
stage. See Fig 3.
Assembly

Fig 3
Next, fix one of the side panels to the base and back panel, see Fig 4

Fig 4
Again, DO NOT TIGHTEN the screws yet. Now attach the other side panel, see Fig

Fig 5
The base is now assembled and you are about to align the 4 main sections together. This requires a
hard, flat surface. Lie the mount down on its side opposite the back panel and adjust the panels until it
lies flat on the floor. If you have tightened the screws too much it will not lie flat and you will need to
slacken them. Once the mount is lying flat, tighten gradually the screws until they are fully tight and the
mount is lying perfectly flat. Stand the mount up and you are now ready to add the telescope tube and
cradle assembly.
The easiest method of placing the telescope tube and cradles on the mount is to hold the two trunnion
bearings as you would the carrying handle on a suitcase, one in each hand. Carefully position the two
bearings directly over the top of the semi circular cut out on each of the side panels and lower the
bearings until they lie snug against the four rectangular pieces of PTFE in the cut outs. The telescope is
now ready for checking prior to use.

Fig 6
Before beginning to use the telescope there are a few things you need to check out first. This will
ensure you have a trouble free viewing session ahead of you. The fist thing to check is if the trunnion
bearings are lying snug a set square on the PTFE Alt. Bearings. On the smaller aperture models it is
unlikely you will come across a problem here but on the larger models occasionally a slight
misalignment occurs. Fig shows the location of four of the alignment screws on one side of the
trunnion bearing on larger models. These four screws, in conjunction with the four other screws shown,
will allow you to exactly align the bearings to the mount. This combination of ‘push/pull’ screws is
allowing the bearings to be slightly skewed against the hidden trunnion blocks which are inside the
trunnion bearings but unfortunately not visible. Once aligned, it will not be necessary to adjust them
again unless you completely dismantle the mount.
The next thing to check is the collimation (optical alignment) of both mirrors to the tube and each other.
Many people worry about collimation because on large, short focal length telescopes can be
sometimes difficult. However, if you follow the following, exactly, you will have no problem, probably.
If the telescope has travelled well to you, you may well still have a perfectly collimated telescope as in
Fig 7. Unfortunately most telescopes move out of alignment to varying degrees when being transported
over long distances. In those cases, you may well see something like Fig 8 or Fig 9. The secondary
mirror is slightly out in fig 8 and in f9, both mirrors are slightly out.
Not a problem:
The following is by no means a definitive description of collimating a Newtonian, neither is it the easiest
method to teach or learn. However, it has the advantages of being free, no equipment needed,
and, once learned, the principle can be applied to most telescopes. I will refer in the text to a `Polo mint'
It is the easiest method I know to refer to a particular view through the telescope when using this
procedure. For those who have lived a very sheltered life, a Polo mint is a circular white mint with a
central hole of approximately 25% of the overall mint's diameter.
Checking things
Collimation

Technical stuff!
If you can have someone to help in this procedure you will find things are resolved much, much quicker.
Procedure:
The first thing, which must be done, is to examine the telescope in daylight when positioned
horizontally (ish) and facing an even light coloured surface. In your house and pointing towards a light
painted wall or similar is ideal. If you point it to a surface which is unevenly lit, uneven colouration, or
texture, it can deceive your eyes in positional aspects.
If you can leave about 10 foot between the end of your tube and the `wall', so much the better.
Stand as far away from the end of the tube and look down it. You should see everything symmetrical.
When you position your head so as to see an even amount of inside the tube surrounding your mirror,
your eye should be blotted out with the secondary holder. Try it you will immediately see what I mean. If
you are too close to the tube this pre-test is not possible. If symmetry is not obvious the main
mirror's collimation is out. Get your ‘assistant’ to slacken just one of the nuts at the base of your mirror
cell end of the tube while you are viewing down the tube. Only ¼ turn and you will see a movement in
the annulus of inner tube/mirror/your eye relationship changing. Adjust the mirror wing nuts until you
are getting exactly the same view from each side of the mirror/tube. You will find that when you have
reached the correct position of your mirror's collimation that any view from one side of the edge of the
tube, is identical to a view at 180 degrees opposite.
Cell used on all models 300mm and larger.

150, 200 and 250mm models use three adjustment
screws only and closed cell.
It sound complicated but it really is a simple operation once you try it.
At this stage you will probably find your mirror is pretty much collimated to begin with, unless, some
excessive ‘twiddling’ has been going on before hand. Unless you achieve symmetry here, no amount of
trying to collimate on a star will be possible. Most collimation problems by far occur with the secondary
mirror's position and attitude. Achieve a good symmetry with the primary and the following will be that
much easier.
Up to this point there has been no need to look into the eyepiece draw tube. If you have tried to
collimate your primary mirror by looking into the draw tube you have probably got it wrong because any
positional errors in your secondary will affect the main mirrors orientation, and so on………….
The secondary mirror has several positional axes, all of which have to be within reasonably tight
tolerances. The mirror can rotate towards you, away from you, tilt towards you and away from you and
move up or down the telescopes optical axis (the main mirror's axis). To discus all these here will take
far too much time and text so, I am assuming that you are seeing concentric `circles' of your
eye,

Secondary spider arrangement
Just to give you an idea what you may see when you look in the focus mount with no eyepiece fitted,
there are three sketches below which show what you could see when you point your telescope at a
light coloured wall in daylight. A reminder is required here, NEVER, EVER POINT YOUR TELESCOPE
AT THE SUN. If you do and look in the draw tube or eyepiece, you have a very good chance you will
loose the sight in that eye due to it being badly burned.
Fig 7 Fig 8 Fig 9
Once you have achieved this above view (may differ a little in certain models), theoretically you will
view correctly collimated images, but, unfortunately, to achieve the above is very difficult
without considerable practice. Don't worry if you can't get it exactly as the pic, any small differences you
will remove in the star collimation.
Star collimation:

Point your telescope at a bright star and have approximately a 25mm eyepiece in the draw tube. Focus
the star, if OK, use a much higher power eyepiece, minimum 10mm. If it focuses to a symmetrical point,
enjoy your evenings viewing and read no further. If you are seeing a flare to one side of the focused
star image some collimation is needed.
Assuming you have a flare to one side carry out the following: Put your low power eyepiece in and
defocus inside the telescopes focal point until you see a `Polo mint' image occupying about 10% of
your field of view. If your collimation is a way out the `hole' will be off center. Here is where your
apprentice comes in again. You need to adjust the three screws around the edge of the central part of
your spider, the section which holds your secondary mirror and it's holder. Very carefully ask your
assistant to unscrew any of the screws about 1/8th of a turn whilst you are looking at the out of
focus image. The object of the exercise here is to move the image in your field of view in the direction
of the thickest part of the `mint' If the adjustment of the chosen screw is moving your image
in the wrong direction, move it back to its original position and then select the correct screw(s) to
achieve this motion of the out of focus image in the required direction. I say screws because you only
have options of 120 degree movement by adjusting any one screw, two screws may need adjusting by
various amounts to achieve the correct direction. Careful here, very small amounts are needed.
When you have moved the out of focus image in the required direction, try refocusing the telescope
and you will see an immediate improvement in the reduction of flaring. Continue with the 25mm
eyepiece until all looks symmetrical. Then, repeat the procedure with a higher power eyepiece.
Eventually you will be able to collimate your telescope with this method in a couple of minutes. When
the hole in the mint is central, a focused image should show you pin sharp images. Do not expect to
see small pin sharp images of very bright stars, there is so much light from them condensed into a very
small disc that your eye cannot cope, the sparkly effect is caused by this. To test your telescope for
final collimation, try about a third magnitude star.
In daylight following this procedure you can look into your focus mount draw tube and make a mental
note of what it looks like, the relationships of eye reflection etc., etc. You will probably see that
perfect symmetry is not present. The reason for this is that there is an added tolerance on the
secondary's dimensions, which will allow correct optical collimation within a `band' of some positions of
your secondary. It is possible to achieve both visual symmetry and optical symmetry (collimation) but it
will take considerable practice and achieve virtually no difference in the telescope's performance.
I appreciate purists will frown on the last sentence above and several others, but, this is about getting
you outside looking at sharp, symmetrical star images and fine planetary detail, it is not intended as a
lesson in optical physics and engineering. Experience in collimating will allow you to check in seconds
as to whether your telescope, or anyone else's, is correctly collimated. In a short period of time you will
appreciate the difference a well collimated telescope makes to the quality of star images, and, you will
strive to get just that bit better collimation, and hence, performance out of your telescope.
If anyone needs any elaboration on any of the above points, feel free.
Good viewing!

When your telescope is fully collimated you need to set up your finder scope. First thing is, you need to
focus it for your own eyes. To do that, when outside and viewing some object at least a kilometre away,
loosen the ring towards the top end of the finder by rotating it and the top most section of the finder.
Both will come loose and you can then screw in or unscrew the longer top section until the finder
focuses perfectly for you. Then tighten the ring against this top section. It will not need focusing again.
The next step is to align the finder with the telescope itself. You need to locate some celestial bright
object in your telescope with a low power eyepiece. When you have it in view, adjust the two screws (3
or on some models) until the cross hairs of the finder scope are exactly on the celestial object. For
accuracy, the moon is a little too large for this; pick a bright star or planet. When done you need to test
how well it is aligned. Move your telescope on its base until you find another bright object in the cross
hairs, check if it is in the centre of the view in your eyepiece. If its not, adjust your telescopes position
until it is the centre and then just adjust slightly you finder scope until the object lies directly under the
cross hairs.
When your telescope is fully assembled, collimated and set up, you are now in a position to start using
it. Set up the ‘scope on a relatively level, hard surface. Try to have the best views of the sky towards
the south as most objects will appear in this area of the sky at some time in the year. Find the object
you want to view in your finderscope and insert a low power eyepiece, 25mm or similar. Now turn the
knobs on the focuser mount to focus the image. Try a higher power eyepiece, around 10mm. See how
the image is more magnified. Don’t forget, Never look directly at the sun with a telescope, eye damage
will almost certainly result.
Our Dobsonians use two types of focusers. The standard range uses a normal type rack and pinion
focuser. The 150mm models use a 31.7mm size and the remaining, a 2”, 50.8mm size. They are
straightforward to use and have just a simple rotating knob(s) for focusing and a locking knob to secure
the position when focused.
The De-Luxe range use our Crayford 2” focuser. All 2” focusers, regardless of design, include an
adaptor for 31.7mm equipment. The Crayford below has just two screws to adjust focusing pressure.
These are shown below. Adjust these to achieve a pressure setting to your liking.
Using your telescope

OC-1 Cray ord. On our Dobsonian models, where itted, the draw tube is silver in colour.
Virtually all parts of your telescope are resistant to normal usage and, to the sometimes aggressive
weather we can have. There are though two or three exceptions and these need special care and
attention.
Whenever possible, always store your telescope tube indoors, in a dry room ideally. Its not important if
its unheated as long as its dry and little dust.
Before putting your tube in a suitable storage position after having used it outside, carry out the
following procedure. This will extend the life of your optics for years.
When you bring indoors your telescope tube, the parts of the telescope are usually much colder than
indoors. This means that often condensation will collect on the optical surfaces of your mirrors, just as
steam condenses on a cold mirror in a bathroom. If you put your telescope away in this condition, the
moisture can remain on the mirrors for hours and, slowly, but very surely, start to attack the coatings.
By far the best method is to blow, by means of a hair dryer or fan, air directly onto both mirrors until the
condensation disappears. Then, and only then, put the dust caps on the tube end(s) and the plug into
the focus mount and store the tube correctly.
We don’t recommend cleaning the mirrors unless you have the correct equipment and are experienced.
A small amount of dust will cause far less of a problem compared with the possible damage which can
be caused with incorrect cleaning.
The tube external surfaces can be wiped down with a cloth moisten with water or a dry cloth to remove
dust.
The mount can be stored within a garage or outhouse but make sure it is kept dry as dampness will dull
the powder coating on the aluminium.
Care and Ma
intenance

The main accessories for our Dobsonians are listed below. For price and further details either view our
CD-Catalogue or, visit our web site for the appropriate items.
Eyepieces. For best results use Lanthanums. They are excellent and have features to make them ultra
user friendly
Failing Lanthanums, take a look at Super Plossls. Very good eyepieces, cheaper than Lanthanums, not
as many features but give very good results.
Filters. For visual use on enhancing planetary detail, reducing the glare of the moon or, enhancing the
views of faint deep sky objects if you have light pollution at your viewing site.
Depending on which model you have, it is possible to upgrade the optical performance of your
telescope, although it is easier, and less expensive to do this at the time of ordering. See our web site
or CD- Catalogue for the optical options.
If you have any problems with your Orion Optics’ Dobsonian please contact initially your supplier of the
telescope and they will contact us with details. If you chose to buy direct from our Factory Shop, please
phone our contact number 01270 500089 or email us at [e-mail]
Orion Optics
Units 21 and 22 Third Avenue
Crewe
Cheshire
CW1 XU
England
Phone [phone] / 251559
Fax [phone]
Orders o[email protected]
Sales enquiries [e-mail]
Technical [email protected]o.uk
Accessories and Upgrades