Lepus 0.62X Telecompressor Lens
The Optec Lepus 0.62X is a 4-element telecompressor designed by Optec engineers to work with newer, well-corrected Schmidt-Cassegrain telescopes such as the Meade ACF and the Celestron EdgeHD series telescopes. Also known as a focal-reducer, the Lepus provides a 0.62X reduction of the telescope's effective focal length. Lepus works well with most mid-size CCD cameras and Digital SLR cameras having sensor diagonals up to 28mm.
Designed for Corrected Schmidt-Cassegrain Telescopes
Optec's NextGEN series of telecompressors were designed to correct the coma inherent in the classic Schmidt-Cassegrain Telescope (SCT). With optical design improvements by Meade and Celestron, the NextGen series would overcorrect for coma and therefore became unsuitable for use with the ACF and EdgeHD optics. Additionally, image sensors were increasing in size and the addition of filter wheels, off-axis guiders, and adaptive optics units required more back-focus distance between telecompressor and camera.
Lepus is optimized for 100mm of distance between the last lens surface and the image plane. Measured from the telecompressor flange, this distance works out to 105mm as shown at left. Assuming a native focal ratio of f/10, the Lepus 0.62X will reduce the effective focal ratio to approximately f/6.2. Shifting the image plane outward will provide additional reduction but a loss of star quality at the edge of the images. The optimal distance for most SCT's is 100mm with the exception of the C9.25 EdgeHD SCT.
Designed for Midsize CCD's and DSLR's
Lepus can will deliver a fully unvignetted image 22mm in diameter, but will provide well-corrected images out to 28mm with a small amount of light fall-off. Flat fielding is recommended for best results. See Optec's line of Alnitak flat-fielding devices for additional details.
The NGC2818 image at left was provided by Ronny Kaplanian and taken with his Celestron C9.25 EdgeHD, Lepus-HD C9.25 Edition telecompressor, and his Starlight Xpress SXVR-M25C camera in a monochrome mode with separate RBG filtered images. The image sensor on the SXVR-M25C measures 23.5mm x 15mm for a diagonal measurement of nearly 28mm. The image was combined and further processed by Terry Hancock with only slight cropping to remove the stacking artifacts. Click here for a full size image in pdf format.
Image courtesy Ronny Kaplanian. Processing by Terry Hancock.
Klaus Brasch reviewed the Lepus-HD C11 Edition telecompressor with his Celestron EdgeHD C11 telescope for the January 2012 issue of Astronomy Technology Today.
Dr. Brasch writes "The Lepus telecompressor is light weight, well made and yielded pin-point stars across the entire image."
Read the full report at the Astronomy Technology Today website or click the image at right.
Article and link courtesy Astronomy Technology Today and Dr. Klaus Brasch.
The Lepus telecompressor lens design is available in several editions for a number of popular Corrected Schmidt-Cassegrain Telescopes.
- #19405 - Lepus-STL 0.62X with STL camera-side thread is a special edition designed to fit directly into the STL 2.156"x24tpi female thread on the SBIG STT8300-FW8G-AO8 camera. The camera side thread can also be attached to the camera with a special STL-camera fixed length camera mount or the new VLC mounts.
- #19407 - Lepus 0.62X Standard Edition fits into any 2-inch focuser and works especially well with the Meade f/10 and f/8 ACF Coma-Free Schmidt-Cassegrain Telescopes. Camera mounts are available in fixed and variable lengths.
- #19409 - Lepus HD C8 EdgeHD Edition is mounted into a 2"x24tpi thread for direct attachment to Celestron 8" EdgeHD SCT. The mount is close-coupled to maintain optimal image quality.
- #19410 - Lepus HD C9.25 EdgeHD Edition is mounted into a 3.25"x24tpi thread for direct attachment to Celestron 9.25" EdgeHD SCT. The mount is close-coupled to the telescope OTA and have a shorter back-focus to maintain optimal image quality.
- #19411 - Lepus HD C11 EdgeHD Edition is mounted into a 3.25"x24tpi thread for direct attachment to Celestron 11" EdgeHD SCT. The mount is close-coupled to maintain optimal image quality.
- #19414 - Lepus HD C14 EdgeHD Edition is mounted into a 3.25"x24tpi thread for direct attachment to Celestron 14" EdgeHD SCT. The mount is close-coupled to maintain optimal image quality.
User Submitted Images:
Pat Freeman's image of the Veil Nebula was captured using a
Celestron EdgeHD C11 telescope with the #17411 C11HD edition Lepus
telecompressor. This image was taken with a Canon DSLR camera.