Visual Accessories

2" Advanced Convertible Barlow (BARADV)

Our Advanced Convertible Barlow has a unique design that provides several configurations to increase the focal length of your telescope. It was designed to match the characteristics of small and medium size CCD chips. It is also ideal for high-power visual observation and lunar-planetary-solar photography.

It can be used conventionally by inserting an eyepiece or a camera’s nosepiece into its 2" locking adapter.  Alternatively, the optic section can be separated from the 2" locking adapter and screwed directly into a camera’s faceplate, or threaded nosepiece, or extension tubes for a flexure-free fitting. It has both 42 mm and 48 mm threads for versatility. See system chart for configurations.


  • Flat field for imaging and visual
  • Very effective high-tech coatings eliminate ghost images
  • Screws into front nosepiece of cameras and diagonals
  • Ideal for medium size CCD sensors
  • Greater than 98% light transmission
  • Large field optic eliminates vignetting even with f/6 optics

This redesigned optic features a flatter field, allowing it to be used for deep-sky photography when increased magnification of smaller objects is desired. Naturally, additional exposure time will be required. Changing the spacing distance will change the magnification of the Barlow (90 mm back spacing is ideal, yielding 2.0x magnification). The “sweet spot" of the flatter field is between 1.8x and 2.5x.

The 2-element design preserves the fine color correction of the main objective. The optical elements are precision ground and polished to insure that no aberrations are introduced into the system. The Barlow focal length is -102 mm which is longer than conventional types. This minimizes the divergence of the edge rays and therefore reduces the apparent vignetting common in many eyepieces. The Barlow features a brass locking ring that clamps eyepieces and accessories securely, yet will not mar their fine surfaces.

The Barlow’s flat field is optimized for APS-C and smaller sensors (such as the 8300 and 3200 sensors). Using this Barlow with an f/8 refractor provides round stars over 90% of the field and over 80% of the field with an f/6.3 refractor.

The field of view is compared in the images to the left. The far left image is taken using the AP 175EDF at its native focal length of 1400 mm. The immediate left image is taken with the Advanced Barlow at approximately 2.0x magnification. The image at the right shows a final processed image. Please note the excellent star shapes across the image.
Click image for larger size.

Note the following positions and resulting magnifications:
(Distance from rear of Barlow to focal plane, measured from 2" barrel's 48 mm threads. Subtract 7 mm from spacing distannce below when using 42mm threads)

Minimum recommended mag:   1.8x,              70 mm back focus distance
Normal magnification:               2.0x,              90 mm back focus distance
Maximum recommended mag:  2.5x,              134 mm back focus distance


These two images compare the resolution with and without the Advanced Convertible Barlow using a QSI 683 (5.4 micron pixels) camera with the AP 175EDF at 1400 mm focal length. The left image is shown at 400% screen size and the right image with the Barlow is at 200% screen size, keeping the two images equal in perspective. Click image for larger size.

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MaxBright Diagonal (PMDMAX)

The Astro-Physics 2" MaxBright Diagonal was designed with several unique features to provide optimum performance and years of use.

Dielectric Coatings
The Astro-Physics 2" diagonal has a very high-tech dielectric coating that was developed originally for military optics used in hostile environments such as blowing desert sand. There is no aluminum or other reflective metal used. The reflective surface consists of multiple layers of thin film oxides, similar to those used in anti-reflection coatings. The coatings are deposited using a sophisticated low-stress deposition method.

Advantages of the Astro-Physics Dielectric Coatings:

- Reflectivity is above 99% over the entire 4000 to 7000 Å photo-visual range. Thin film coatings have extremely low surface scatter compared to aluminum or enhanced aluminum coatings. Dielectric coatings (if done right) will result in less scattered light. Examination with a laser source shows approximately a 5 fold reduction in surface scatter, a tremendous improvement over aluminum mirrors.

- T
he main advantage of a dielectric mirror coating (again, if done properly) is that the surface will be durable and will last for a lifetime. It will never tarnish and will be resistant to sleeks when cleaned. This means that for critical planetary viewing you can clean the surface and not have to worry about creating microscopic sleeks which lead to scattered light and lower contrast.

For critical planetary viewing it is important to have the eyepiece and diagonal surfaces as clean as possible. You will find that even after one observing session the diagonal surface will accumulate crud. The inherently high contrast and cleanability of the Maxbright insures that it is never a limiting factor when viewing subtle planetary detail. For cleaning instructions, please
use this link: Cleaning Insructions for the MaxBright Diagonal.

Mechanical Features
Our customers have appreciated the brass locking ring on our adapters and 2" Barlow and have urged us to develop a diagonal with this feature. The recessed brass ring is under the thumbscrew location. As you tighten the thumbscrew, the brass locking ring clamps onto your eyepiece. This provides a more secure grip for your expensive eyepieces than the head of a single screw can provide. As an added advantage, the brass will not mar the surface of your accessories.

The diagonal is accurately square to the optical axis due to the CNC machined parts and special mounting method of the mirror. The baffles and flat black interior allow maximum contrast. It is threaded for 48 mm filters so that you can change eyepieces with ease without changing the filter.

Important: Consider the following dimensions to be sure that the barrel of your accessories will not strike the mirror. When using 2" accessories, the depth from the top of the diagonal to the mirror surface is 1.85" (46.99 mm). When using 1.25" accessories, the depth from the top of the diagonal to the mirror surface is 2.25" (57.15 mm); our 1.25" adapter adds another 0.25" (6.35 mm) height. Remember that if you add filters to your eyepiece barrels, the overall length changes.

The PMDMAX has a net spacing distance of 4.1" (104.1 mm), comprised of 2.75" (69.85 mm) from the center of the ocular opening to the mirror and 1.35" (34.29 mm) from the center of the objective opening to the mirror.

The nosepiece net insertion depth is 1.4" (35.6 mm).

Note: Please consider our optional 1.25" Adapter (ADA125) with brass locking ring and 48 mm filter thread as the perfect compliment to the Maxbright Diagonal when using your 1.25" accessories.

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10 x 60 Baader Planetarium Vario Finder with Illuminated Reticle Eyepiece,
45° Erecting Prism, and Quick Release Bracket (1060VQ)
The 10 x 60 Vario Finder is a fine replacement for our former 8 x 50 Straight-through Finder (discontinued). This new finder is produced by Baader Planetarium and introduces many new features and functionalities.
  • High quality coated 61mm f/4 objective (250 mm focal length)
  • Coarse focusing is provided by the sliding draw tube (35 mm travel), and fine focusing is performed using the threaded objective cell with lens-locking ring (12 mm travel).
  • 1 ¼" brass clamp ring with 3 thumb screws for interchangeable eyepieces and accessories
  • 45° erecting prism with 1 ¼" nosepiece and T-2 thread
  • 25mm eyepiece with variable brightness illuminated measuring reticle
  • Retractable dew shield

The Vario Finder system is unique in that it utilizes a high quality 2-element Zeiss designed objective and an interchangeable T-2 accessory system that will allow the included 45° prism to be switched with user-provided 90° prisms, or used in a straight-through configuration. Because of the exceptional quality of the optics, this finder will also be able to be used as a guide scope employing a variety of new 3rd party guide cameras.

This finder assembly includes a newly designed Astro-Physics custom bracket for mounting in our Quick Release Base (QRBASED). The bracket slides into the dovetail base and then tightens quickly with two thumbscrews. This provides a secure and repeatable method of attachment. A Baader tripod dovetail adapter is also included with the finder.

The bracket assembly includes the bracket ring, alignment screws, and male dovetail base. The nylon alignment screws provide a quick and easy way to align your finder without marring its finish. Note: A Quick Release Base (QRBASED), purchased separately, is required for attachment. The illuminator uses one CR2032 coin battery (included).

Weight: 2 lb. 1 oz. (0.935 kg)

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10 x 60 Vario Finder with Quick Release Guider Bracket Kit (1060VGKIT)

The Astro-Physics designed Guider Bracket greatly expands the versatility and functionality of the Baader 10 x 60 Vario Finder Scope.  By removing the Finder Scope’s 45° prism and reticle-eyepiece and substituting T-2 extension tubes, the finder transforms into a straight-through guide scope.  This unique Guider Bracket provides the robust, flexure-free structure to hold even the heaviest guide cameras.   Whether you use a feather-light camera, such as the SBIG STi, or a heavy-weight, such as the SBIG ST-402, this Guider Bracket will help you master autoguiding.

Please follow this link to additional Guider Bracket information and accessories.

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10 x 60 Quick Release Finder Bracket (S1060QRM)

This stylish quick release finder bracket was developed by Astro-Physics specifically for the 10 x 60 Baader Planetarium Vario-Finder to provide a rigid, yet light weight, mounting system. However, it can be used with any finder that has a body length of at least 3 ¼" (83mm) and a diameter of between 2 3/8" (60 mm) and 2 5/8" (67 mm), allowing it to fit into this bracket with enough room left over for adjustment. This versatile bracket can be mounted in several ways:

The bracket assembly includes the bracket ring, alignment screws, and male dovetail base.

This assembly, with your finderscope, slips into the groove of the base and tightens quickly with two thumbscrews. Now you are ready to go. There are no mounting screws to get lost in the grass or snow and your fingers won't freeze as you struggle with tools. This accessory is a must!

You may want to consider purchasing extra bases that you can mount permanently on your other telescopes. This will allow you to use the same bracket and finder interchangeably. Now you can attach and detach your finder in seconds while retaining the alignment.

Weight:  5.3 oz (0.15 kg)
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Base for Quick Release Finder Brackets (QRBASEM)
This Quick Release base is designed to securely fit scopes from as small as 3” on up, so that it will automatically contour to fit all your scopes.

It mounts onto the predrilled holes of your Astro-Physics refractor or onto other commercial telescopes that utilizes the same side-to-side hole spacing.  It even incorporates inline holes to make it compatible with virtually any scope/focuser combo that is available today. Fortunately, the spacing between the holes of most finder brackets is standardized, whether side-to-side or inline.

The dovetail design of this base accepts these items:

Note that though the dovetail bar of our Guider Bracket Kit will fit this base, we recommend the longer QRBASEG for stability.

The symmetric design of this base makes it easy to rotate the base 180° for either left-handed or right-handed use.  There is even a tapped ¼”-20 center hole, so that it can be attached to dovetail bars to further expand its usefulness. 

The base is small enough that you can leave it attached to your scope. Simply loosen the thumbscrews and slide the finder assembly out. When you place your scope into its case, turn the scope so that the base is in a corner position.

You may wish to purchase an extra base to attach to other telescopes so that you can swap your finder easily from one instrument to another. If your scope has multiple finder bracket holes, you can either have multiple types of finders on your scope or have the ability to quickly switch your finder from one side of the scope to the other.

The mounting hole spacing is approximately 1 3/8" (34.9 mm) side-to-side and uses 10-32 x 5/8" screws for attachment.  The inline hole spacing is approximately 0.78” (20 mm).  The base length is 1.35" (34.3 mm).

Consider adding the Male Dovetail Base (A3251-B) below to other finder accessories that you may have in order to make them compatible with our Quick Release Base!

Weight: 2.2 oz. (0.06 kg)

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Male Dovetail Base (A3251-B)

Our male dovetail base is a versatile accessory - an integral part of our Quick Release Finder Brackets and an essential link for attaching other accessories to our refractors. We include this part in every order of modified Tele Vue Starbeam (STARFMD) finder scope. It is used with the Base for the Quick Release Brackets (QRBASEM), shown above, or with our 7-inch sliding bar. See this link for Tele Vue Instructions.

Hole Pattern Schematic

Weight: 2.3 oz. (0.08 kg)

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Copyright © 2012, Astro-Physics, Inc. - All Rights Reserved
This page was last modified: November 1, 2018

Astro-Physics, Inc.
11250 Forest Hills Road, Rockford, IL  61115, U.S.A.
Phone: 815-282-1513   Fax: 815-282-9847