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Untitled Document

ATTENTION: Buckeyestargazer.net will be closed 7/12/2024 - 7/28/2024.  Orders placed during this time will be fulfilled in the order they were received beginning July 29, 2024.   Thanks for your patience and your business!

Duncan Mask for SCT Collimation

A Duncan Mask can be used to easily and quickly collimate your SCT. Instructions are provided below.    

The mask comes in three sections that "snap-fit" together and can be taken apart for easier storage (C5 and C6 are one piece). 

Feel free to contact me if you do not see your scope listed.


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Printed in durable, temperature tolerant PETG filament.

Duncan-C5 - $23
Hole dia. 50mm
Celestron 5" SCTs
Duncan-M8 - $24
Hole dia. 72mm
Meade 8" LX200/GPS/90/GPS LX50/Model 2080 (F10)
Duncan-C8-NF - $24
Hole dia. 67mm
Celestron 8" SCT (non-Fastar/Hyperstar)
Duncan-M8F6.3 - $24
Hole dia. 75mm
Meade 8" Model 2080 (F6.3)
Duncan-CClassic8 -$24
Hole dia. 72mm
Celestron "Classic8" (specific scope only)
Duncan-M8LXACF - $24
Hole dia. 77mm
Meade 8" LX90ACF/ LX200ACF/LS8ACF
Duncan-C9.25-NF - $25
Hole dia. 85mm
Celestron 9.25" SCT (non-Fastar/Hyperstar)
Duncan-M10
Hole dia. 78mm
Meade 10" LX200/GPS/ 90/GPS/LX50/LX3/2120
Duncan-C11-NF - $31
Hole dia. 92mm
Celestron 11" SCT (non-Fastar/Hyperstar)
Duncan-M10LXF6.3 - $26
Hole dia. 85mm
Meade 10" LX200 F6.3
Duncan-C14-NF - $42
Hole dia. 104mm
Celestron 14" SCT (non-Fastar/Hyperstar)
Duncan-M10LXACF - $26
Hole dia. 89mm
Meade 10" LX200ACF/90ACF
Duncan-C6 - $26
Hole dia. 57mm/73mm
Celestron 6" SCT (Fastar, Hyperstar, EdgeHD)
Duncan-M10LX600-850 - $26
Hole dia. 122.4mm
Meade 10" LX600/850ACF
Duncan-C8 - $27
Hole dia. 71mm/78mm
Celestron 8" SCT (Fastar, Hyperstar, EdgeHD)
Duncan-M10LXEMC - $26
Hole dia. 87mm
Meade 10" LX200 EMC
Duncan-C9.25 - $28
Hole dia. 91.5mm/106mm
Celestron 9.25" SCT (Fastar, Hyperstar, EdgeHD)
Duncan-M12LX200 - $36
Hole dia. 89mm
Meade 12" LX200/LX200GPS
Duncan-C11 - $34
Hole dia. 98mm/111mm
Celestron 11" SCT (Fastar, Hyperstar, EdgeHD)
Duncan-M12LX850 - $36
Hole dia. 126mm
Meade 12" LX850
Duncan-C14 - $45
Hole dia. 116mm/127mm
Celestron 14" SCT (Fastar, Hyperstar, EdgeHD)
Duncan-M14LX200 - $42
Hole dia. 130mm
Meade 14" LX200/LX200GPS
Duncan-M14LXACF - $42
Hole dia. 136mm
Meade 14" LX200ACF
Duncan-M14LX850 - $42
Hole dia. 136mm
Meade 14" LX850
Duncan-M16LX200 - $47
Hole dia. 115.5mm
Meade 16" LX200/LX200GPS
Duncan-M16LXACF - $47
Hole dia. 145mm
Meade 16" LX200ACF

Instructions for use:

1.  Make sure your scope has cooled to ambient temperature. 
2.  Point the scope at a bright star that is high in elevation.
3.  Place the mask on the scope.  Orient the mask such that the three snap fit connection lines point to the 3 collimation screws on the Secondary as shown in the scope image to the left. 

4. A camera works best, but you can also use a high magnification eyepiece.  Grossly defocus the star. You should see three arcs that correspond to the three cutouts.

5.  As you bring the star closer to focus the curves will change into lines pointing to a common center.    

6.  Use the lines to adjust the collimation screw opposite the line.  As you adjust the screw the line will move toward the center.  The goal is to form a perfect Y where the lines touch in the center.