ORION TELESCOPES & BINOCULARS 8743 User manual

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Orion®2x 3-Element
Barlow Lens, 2"
#8743
A barlow lens is one of the most valuable accessories you
can buy. In simplest terms, it doubles the magnification of
any eyepiece placed into it. This essentially doubles the
number of magnifications available to you without the pur-
chase of more eyepieces. It helps obtain high powers with
longer focal length eyepieces which have comfortable eye
relief – no more jamming your eye into the tiny lens of a short
focal length eyepiece! A barlow lens also improves many
eyepieces’ performance when used with short-focal length
telescopes, since most eyepiece designs work better when
the incoming light is more parallel.
The 2" barlow lens is especially versatile since it can be
used with either 2" or 1.25" eyepieces. Its three-element
design will give you superior color correction to two-element
designs, a clear advantage for higher-power observing. It will
work with any telescope that has a 2" focuser.
How to Use the Barlow
First, observe the outer end of the barlow that contains the
thumbscrews (Figure 1). Notice there is a 1.25" opening. This
opening will accommodate any 1.25" eyepiece. If you loosen
the shorter thumbscrew, you will be able to remove the 2"-to-
1.25" adapter to reveal a 2" opening that will accommodate
any 2" eyepiece (Figure 2).
When inserting an eyepiece into the barlow lens, simply place
the eyepiece’s barrel into the barlow’s opening (2" or 1.25")
and tighten the barlow or adapter thumbscrew until the eye-
piece is securely connected (it should not slip if you gently tug
it outward). You may notice as you tighten the thumbscrew a
brass compression ring encircles the eyepiece barrel with an
even grip; this compression ring design prevents the thumb-
screw tip from marring the eyepiece barrel.
Now you are ready to connect the barlow to your telescope.
If your telescope is a Newtonian, insert the barlow into the
focuser drawtube, and tighten the thumbscrews of your
focuser onto the barlow’s barrel. If your telescope is a refrac-
tor or Cassegrain, insert the barlow into the 2" star diagonal
and make sure it does not “bottom out” or otherwise hit the
surface of your star diagonal’s mirror or prism.
A barlow lens can be placed before the star diagonal, (direct-
ly in the visual back of your telescope) giving you a higher
than 2X magnification factor. This configuration requires sev-
eral inches of outward focus travel, and may not reach focus
without the use of extension tubes.
Figure 1. The Orion 2x 3-element barlow lens, 2".
Barlow thumbscrew
(short)
1.25" Opening
2"-to-1.25"
Adapter
thumbscrew
(long)
Barrel
Figure 2. Removing the 2"-to-1.25" adapter reveals the
opening for a 2" eyepiece.
2"-to-1.25" Adapter
2" Filter threads
IN 277 Rev B 01/09
2" Opening

Focusing
Point your telescope at an object, placing it in the eyepiece’s
field of view. It is most convenient to use a wide-field eyepiece
(typically a 25mm or 32mm Plössl) to do this. If you are focused
on a celestial object and your telescope is equatorially mount-
ed (and polar aligned), you may engage your tracking motor to
keep the object in the field of view. Once you have found and
centered your intended target, add the barlow to your eyepiece,
insert the combination into your focuser or diagonal, and re-
focus with your telescope focuser. If you are re-focusing with a
2" eyepiece, the barlow will not require much inward or outward
focus travel relative to the eyepiece’s focus unless the barlow
cannot be fully inserted into the drawtube or diagonal. If this is
the case, some inward focus travel will be necessary. For 1.25"
eyepieces, the barlow requires approximately 1" of outward
focus travel relative to the eyepiece’s focus.
Useful Magnifications
The barlow combined with your eyepieces can provide many
useful magnifications. The upper limit will be 50-60x per inch
of telescope aperture. For example, if you have a 4-inch tele-
scope (102mm), you will get a clear image up to approximately
200-240x.
No matter what telescope you use, its view will be limited by
the stability of the air in the upper atmosphere. If this air is
steady (“good seeing”) you can support the highest power. If
the air is unsteady (“bad seeing”), and you use high power,
it will appear as if you are looking at your target through a
mirage on a desert highway—wavy and smeared. In that case
it is best to use low to medium power (30-120x). Seeing can
vary through the course of a night, minute by minute, so high-
power observing can take some patience.
Keep in mind that when the barlow is inserted, magnification
will be doubled, but the image will be four times dimmer.This is
an inherent principle of physics that cannot be avoided.
Use of Filters
A 2" filter can be threaded onto the bottom of the 2"-to-
1.25"adapter. This prevents having to move the filter from
eyepiece to eyepiece if using 1.25" eyepieces. If using a 2"
eyepiece, thread the filter directly onto the barrel of the eye-
piece itself.
Care and Maintenance
Leave the barlow lens out to dry after use. If it is capped with
moisture on the surface of the glass, fungus may grow on the
optical coatings. Therefore, place the endcaps on the barlow
only when you are sure it is completely dry. For storage, leave
the caps on and place it in an appropriate enclosure, prefer-
ably a dedicated eyepiece case with foam padding.
The lens elements of the barlow are coated with anti-reflection
multi-coatings, which can be damaged with careless handling.
Avoid touching lens surfaces with your fingers or any coarse
material. Clean the lenses if they get noticeably dirty. Always
use lens cleaning tissue and fluid specifically designed for
telescope optical coatings. Do not use regular tissue or fluids
made for eyeglasses or household use. Do not disassemble
the barlow to clean it, with the exception of the barrel, which
may be unthreaded to better access the lens surfaces.
To clean the lens surfaces, first blow air on them with a blower
bulb or compressed air to remove any large particles. Then
brush the lens surfaces with a soft lens brush and blow air on
them again to remove any dislodged particles. Put a couple
of drops of lens cleaning fluid on a sheet of lens tissue (never
directly on the lenses). Wipe the lenses gently with a circular
motion, taking care to avoid undue pressure or rubbing, which
can scratch the coatings. Quickly remove the excess fluid by
wiping with a clean, dry lens tissue.
Specifications
Lens design: Triplet (three lens elements)
Magnification factor: 2x
Lens coatings: Fully multi-coated
Eyepiece compatibility: Accepts 2" eyepieces or
1.25" eyepieces with included
adapter
2"-to-1.25" Eyepiece adapter: Threaded for Orion 2" filters
Weight: 13 oz.
One-Year Limited Warranty
This Orion 2x 3-Element Barlow, 2" is warranted against defects in materials or workmanship for a period
of one year from the date of purchase. This warranty is for the benefit of the original retail purchaser only.
During this warranty period Orion Telescopes & Binoculars will repair or replace, at Orion’s option, any
warranted instrument that proves to be defective, provided it is returned postage paid to: Orion Warranty
Repair, 89 Hangar Way, Watsonville, CA 95076. If the product is not registered, proof of purchase (such
as a copy of the original invoice) is required.
This warranty does not apply if, in Orion’s judgment, the instrument has been abused, mishandled, or
modified, nor does it apply to normal wear and tear. This warranty gives you specific legal rights, and
you may also have other rights, which vary from state to state. For further warranty service information,
contact: Customer Service Department, Orion Telescopes & Binoculars, 89 Hangar Way, Watsonville,
CA 95076; (800)-676-1343.