1 / 18

Collimating an SCT

Collimating an SCT. Common Misconceptions: SCT's don't loose collimation Not as important due to the long focal length Collimating is hard Some “horror” stories about bad SCT's are likely due to mis-collimated optics. A “Perfect” SCT:. An Uncollimated SCT. Uncollimated SCT.

psyche
Download Presentation

Collimating an SCT

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Collimating an SCT • Common Misconceptions: • SCT's don't loose collimation • Not as important due to the long focal length • Collimating is hard • Some “horror” stories about bad SCT's are likely due to mis-collimated optics. Jim McPherson

  2. A “Perfect” SCT: Jim McPherson

  3. An Uncollimated SCT Jim McPherson

  4. Uncollimated SCT Jim McPherson

  5. Collimate on a star • Use an artificial star! • I used a #80 drill through thin aluminum for the first baffle. • Apparent size = baffle1diameter % (length%eyepiece_fl) Jim McPherson

  6. How to Collimate Quickly • 2 stages of collimation: • 1. Centering the secondary shadow • 2. Centering the Airy disk • Both stages use the EXACT same procedure • The final stages will be turning the screws such a small amount that you can barely tell your taking action Jim McPherson

  7. How to Collimate Quickly • Divide the 3 screws into 2 halves Jim McPherson

  8. How to Collimate Quickly • Assign each screw a name: • The one closest to the top is the “12 o'clock” screw • The next two are the right and left screws • Right and left should be from the rear of the scope 12 o'clock Left Right Jim McPherson

  9. How to Collimate Quickly • Step one: • Rotate diagonal to match the 12 o'clock screw • Step two: • Center your target in the 'scope. • Must do this EACH AND EVERY time you adjust a screw • Step three: • Determine which direction the pattern is off in the horizontal plane. Don't worry about vertical yet. Jim McPherson

  10. How to Collimate Quickly • This star is skewed to the left. Jim McPherson

  11. How to Collimate Quickly • If performing a rough collimation, the shadow of the secondary would be at about the 10:30 position in the previous example. • So now looking only at the horizontal error we want to center the pattern horizontally. • ONLY work with the right/left screws in the first step. Don't touch the 12 o'clock screw • To adjust for the above error tighten the screw opposite the error to “pull” it back into the correct place. Jim McPherson

  12. How to Collimate Quickly • You may need to loosen the opposite screw while making the adjustments. Only loosen when you MUST, tight screws are good and you are not likely to warp the secondary. • DON'T TOUCH THE 12 O'CLOCK SCREW! • Remember to keep the star centered while adjusting. Jim McPherson

  13. How to Collimate Quickly • After L/R adjustment: Jim McPherson

  14. How to Collimate Quickly • Now that it is correct horizontally, adjust it vertically • Treat the L/R screws like one screw • Action is reversed compared to the L/R adjustment. • Tightening a screw will push the pattern away from the screw. Jim McPherson

  15. How to Collimate Quickly • Which way do we go? Jim McPherson

  16. How to Collimate Quickly • In this example the pattern is skewed high. • So we would tighten the 12 o'clock screw to push the pattern down, if needed loosen the R/L screws • If the pattern was skewed low, you would tighten the R/L screws, and possibly loosen the 12 o'clock screw. Jim McPherson

  17. How to Collimate Quickly • Overview • Assign screw “names” • Start with secondary shadow • Adjust horizontally • Adjust vertically • Move to diffraction rings • Repeat • Remember to always defocus in the same direction Jim McPherson

  18. Final Result: Jim McPherson

More Related