Current Price: $24.37
Buy It Now Price: $24.37
Bids: 0

:: eBay Listing Template ::

store Logo

Astromania 1.25Inch Metal Collimating Cheshire Eyepiece without Laser for Newtonian Reflector Telescope - Long Version

Product Image

Product Features:

  • Product Dimensions: 6 x 1.4 x 1.4 inches
  • Item Weight: 6.2 ounces
  • Shipping Weight: 7 ounces
  • Item model number: SKU_AM_MCEL12
  • Make sure this fits. by entering your model number.
  • Fits in 1.25" focusers and easy to use;simply cap the telescope, remove the diagonal, and place the eyepiece directly in the focuser.
  • For aligning optics of Newtonian reflectors, Dobsonian reflectors, and Schmidt-Cassegrain Telescopes (SCTs).
  • Accurate collimation is essential for high power observing. Stars will become more like pin points of light, and Planetary / Lunar detail will be enhanced.
  • Item was made by aluminum with crosshair at the bottom allow quick and precise centering of the optics.
  • This collimation eyepiece can be used for precisely collimating the Newtonian and Schmidt-Cassegrain reflector telescopes for better image quality.

Product Description

Collimation is the process by which an instrument’s
optical components are brought into precise alignment with its optical axis
and mechanical axis. In other words, all the mirrors and/or lenses should be
centered and angled so that light entering the telescope forms a sharp image
precisely in the center of the eyepiece. If the optics are not properly
aligned, stars will appear not as pinpoints as they should, but rather as
flared, teardrop-shaped “comets” or “sea gulls.” Astromania 1.25Inch Metal
Collimating Cheshire Eyepiece without Laser for Newtonian Reflector Telescope
- Long Version Purpose of the Collimating Eyepiece Aligning the mirrors seems
easy enough, in theory, but in practice it can be difficult without the proper
tools. A common way of collimating—the “quick and dirty” method—is to simply
remove the eyepiece and look down the focuser tube to center the mirror
reflections. The accuracy of this method, however, is not reliable. For one
thing, there is no way to know whether you are looking straight down the
focuser tube; your line of sight could be off by a degree or two. Another
problem is knowing when the reflections of the mirrors are exactly centered.
Just “eyeballing it” isn’t precise enough; the reflections may appear to be
centered when in fact they are not. The Collimating Eyepiece will take care of
both of these problems, allowing you to achieve precise collimation without
“guessing,” and thus improve your telescope’s performance. The Collimating
Eyepiece is a combination of a “sight tube” and a “Cheshire eyepiece.” The
sight tube’s narrow field of view and crosshairs provide a reference for
centering the optical elements during the collimation process. A Cheshire
eyepiece has a polished flat set in the barrel at a 45° angle, which directs
light entering from a cutout in the side of the barrel down into the optical
path. The Cheshire allows quick and easy collimation of the primary mirror,
assuming the mirror has been marked with a spot exactly in its center. Using
the Collimating Eyepiece Collimation can be performed in daylight, when it is
easier to see what you’re doing. However, never point the telescope or the
cutout side of the Collimating Eyepiece at, or anywhere near, the Sun, or
serious and instant eye damage could result! Insert the Collimating Eyepiece
directly into the 1.25" focuser. When using a 2" focuser, place the
Collimating Eyepiece into a 1.25" adapter. If you use a star diagonal with
your telescope, as is common for Schmidt-Cassegrain telescopes, remove it
before inserting the Collimating Eyepiece. The eyepiece should be inserted to
a depth such that the bottom edge of the eyepiece tube appears slightly wider
than the outer edge of the secondary mirror when you look through the sight
hole. Rotate the eyepiece so that the cutout side is directed toward any
available external light. Make sure there is adequate light in the room or
outside so that when you look through the sight hole, you can see the edges of
the secondary mirror clearly. Tighten the thumbscrew on the focuser tube to
secure the Collimating Eyepiece in place. Now, you are ready to proceed with
collimation. Collimation of Refracting Telescopes If you use the eyepiece for
checking the collimation of a refracting (lens) telescope, then you will see
as many reflections as there are lenses in the telescope. If all the
reflections are round and centred, then your telescope is well collimated.
Long Metal Tube with Crosshairs The Cheshire collimation eyepiece is simple
but absolutely effective. With practice, you will be able to collimate your
Newtonian telescope in just a few minutes - especially if simply finely
collimating your telescope for optimal imaging. The Cheshire eyepiece consists
of a long metal tube and a 45° base. The reticule gives you the orientation
required for the optical axis. Collimation of Different Telescope Types Good
collimation is particularly critical for “faster” Newtonians, those with
f-ratios of f/6 or lower. Once the collimation is set, it will hold if care is
taken in transporting and handling the optical tube. However, any sharp jolts
can knock the mirrors out of alignment, as can jostling of the scope in the
trunk of a car or temperature changes over a period of time. Fortunately,
these telescopes are equipped with adjustment screws that permit easy
recollimation. Testing Your Telescope’s Collimation Just point it at a bright
star and slowly rack the image out of focus by with the focusing knob. If the
telescope is correctly collimated, the expanding disk should be a perfect
circle. If it is unsymmetrical, the scope is out of collimation. In reflectors
and Schmidt-Cassegrains, the dark shadow cast by the secondary mirror should
appear in the very center of the out-offocus circle. If the “hole” appears
off-center, the telescope is out of collimation. Care and Maintenance Since
there are no lenses in the Collimating Eyepiece, care and maintenance is
minimal. It is a good idea to remove any obvious dirt on the inside or outside
of the eyepiece so that the dirt does not get into the telescope tube during
the collimation process. To clean the eyepiece, use a blower bulb or a moist
cotton swab to remove dirt from inside the barrel, and simply wipe the outside
with a damp cloth. Make sure not to disturb the crosshairs, as bending or
breaking may result. Read more

Additional information

Size: Long Version
Brand: Astromania




About Us

Terms & Conditions


In order to best serve our customers across the entire US, we use a wide variety of shipping services. eBay only allows us to display three shipping options in the shipping menu above, so please note that a different shipping method might be used depending on your location; however, we will of course make sure your package arrives within the stated delivery time. All of our items are shipped from our warehouses in the US. Our handling time is 2 business days, and with free shipping the shipping time is 3-4 business days. In most cases however we manage to ship much faster: don’t be surprised if the mailman delivers your package within just a few days!


We accept PayPal and all major credit/debit cards. Once checkout is complete is you will have the option to select payment method.


  • After delivery of the package you have 30 days to inspect and check the item. If there is any problem we will gladly accept the return
  • Please note that after 30 days we can no longer accept returns, and unfortunately cannot make exceptions. However, if the item came with a warranty then the manufacturer should be able to honor this warranty.
  • Items can be returned for refunds only. If you would like an exchange then please use the refund to place the order again.
  • When returning a package it needs to be returned in its original packaging, including all accessories, manuals, etc. If any of these are found to be missing, a restock fee will be applied. So make sure not to throw anything away before you know the item arrived in good condition!
  • Once your returned item is delivered back to us, please allow several business days for us to process your return and refund.

    Filed under: Eyepieces & Accessories