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Using a field flattener with a standard DSLR Camera. Our doublet and triplet refractors are designed to work visually. They are also capable of taking stunning images when used with a camera combined with a dedicated photographic field flattener. The field flattener improves the pinpoint sharpness of stars across the field. The field flattener goes between the camera and the focuser. When using a DSLR camera, simply attach a t-ring to the camera, thread it onto the field flattener and thread the flattener onto the focuser.

DSLR t ring SFF3-48 400

The Importance of proper spacing: The photographic field flattener must be placed at a precise distance from the camera’s internal ccd sensor. If the spacing is incorrect, the performance will be compromised. Our stock flatteners are made to work with DSLR cameras. The distance from the t-ring to the internal ccd sensor on a DSLR camera is about 55 mm. This distance from the camera’s sensor to the front is also known as its “backfocus.”

Non DSLR ccd cameras usually have a much smaller backfocus. In this case, one must purchase threaded extension tube(s) and/or spacer rings to attain the desired backfocus distance of 55 mm.  


Extension tubes and spacer rings: Extension tubes come in various sizes like 5 mm, 10 mm, 20 mm, 30 mm. They thread in between the field flattener and the camera. Spacer rings come in 1, 2 and 3 mm sizes and are placed between the extension tubes. Using a combination of spacer rings and extension tubes, the proper distance of 55 mm from the flattener to the ccd sensor may be obtained.

SFE adapters400

Using the SFF3 field flattener with a CCD camera:

The camera shown to the right has a 38 mm backfocus. So a 5 mm and 10 mm extension tube is used along with a 2 mm spacer ring to obtain the proper spacing of 55 mm. This spacing is measured from the back of the stock field flattener.

You will notice that we have underlined the word stock when describing our field flatteners. Stock field flatteners are made with a machined extension that optimizes them for a 55 mm back focus. In addition to stock flatteners, we can machine a rear extension that is a different length. This is necessary if the ccd camera has a back focus that is more than 55 mm. In this case, call us to get a quote for a custom adapter.

Apogee AltaandSFF focuser480

Using the SFF7 type field flattener with CCD Camera:

For the SFF7 type flatteners, place the spacer ring(s) and or extension tube(s) between the flattener lens and the adapters as shown to the right.

sff7 flattener spacers450

Stellarvue® designs and handcrafts the finest refractor telescopes and provides programs and experiences to foster a greater appreciation of our natural world and to encourage individual exploration of the universe.

All specifications and prices are subject to change without notice. Designs and materials are often modified to improve them. All copy and photographs are copyright 2013 and may not be used without permission.

Stellarvue trademarks and service marks, logos, product and service names are trademarks of Stellarvue (the "Stellarvue Marks"). Without Stellarvue's prior permission, these marks may not be displayed or used in any manner. Some products may be patent pending and we consider all of our designs proprietary. Stellarvue will take necessary action against any dealer in the USA carrying imitations of our proprietary products. Dealers are warned to check with us first before purchasing similar products as there may be illicit copies of products we specifically designed. Such products may only be sold by authorized Stellarvue dealers. Contact or call (530) 823-7796 for more information