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Coma Barlow Bino-100

0.75x APO Reducer

A stunning Reducer from APM. Add a second scope for less!. Click for details. From £589.00



The superb new APO Binoculars. Click for details. £2629.00

Coma Correcting Barlow

Our new Photo Visual 2.7x ED Barlow designed by Gerd During. Click for details. Only £149.00


The Outstanding APM Barlow Lens

© Astrograph Ltd 2016

Technical Data






Camera Connection

Eyepiece Connection

Telescope Connection

Eyepiece Clamping

Max Length                   


Back Focus

Fully Illuminated Field

Optimised Imaging Field

Focal Length                    


APM Barlow Test

Click for larger image

The APM Coma Correcting Barlow re-defines what is possible with a Barlow lens at a surprisingly low price. It has been designed for us by Gerd Düring in Germany following much discussion with users as to what would represent the ideal Barlow lens. We believe this is it.

This new fully Apochromatic design provides a magnification factor of 2.7x and uses a 1.25” lens cell. This lens cell is a 2 element cemented doublet incorporating an FK61 ED element (similar to O’Hara FPL-51). The elements are fully broadband multi-coated and provide 99% light transmission of wavelengths from 400-700nm.

A unique feature of the design is that it is optimised for use with f4 Newtonian telescopes and provides full coma correction for this type. This allows users to view detailed objects at the edge of field with the same clarity as if they were centred. Dobsonian users will find this particularly useful as often objects tend not to be centred on axis with this design.

Despite the optimisation of the optics to correct for coma that is present in Newtonians, the optical quality of our Barlow also allows it to be used with any other type of telescope including our own Apochromatic Refractors. Due to its coma compensating design it will therefore introduce coma to none Newtonian designs. However following testing with a number of telescopes types, we have found the image to still be almost perfect to the very edge of field. Colour correction and optical quality are equal to Fluorite Barlow’s costing many times more. In use we believe you will detect no loss of quality with our Barlow at all even when used with types other than Newtonians.

The design has been optimised for both visual and imaging purposes from the beginning. The fully corrected flat field image circle of our Barlow is 26mm making it suitable for use with a variety of imaging sensors up to APS-C when used at the recommended back focus distance of 112mm.

To provide the maximum number of options for users, our Barlow can be adapted for both visual and imaging use as follows;

For eyepiece use there is a 1.25” adapter using our rotary clamping system. This provides a much better fixing for your eyepiece than single screw based clamps. This attaches to an extension section which allows you to achieve the optimal 112mm back focus and a 30mm image circle. The design also features options for both 1.25” and 2” mounting to your telescope. Both mounting options feature safety undercuts to prevent the Barlow falling out of your telescope!

The eyepiece clamp and extension can then be removed to reveal a T2 thread. This allows for direct mounting of a DSLR T2 mount or CCD camera. Alternatively you can just use the nosepiece which also has a T2 Thread. For the ultimate flexibility, the lens cell itself can be removed and screwed to a standard 1.25” thread. These options provide the approximate correct back focus distance for different imaging setups which can be optimised by using spacers depending on your cameras flange to focal plane distance. The APM Coma Correcting Barlow is available for only £149.00 inc VAT as a photo visual set.

Coma Correcting ED Barlow

Doublet Cell with ED Element

Broadband Multicoated




1.25” / 2”

Rotary Brass Clamp




Min 30mm



200 grams