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Newtonian Collimation

Newtonian Collimation. Marc Feuerberg. Rank, in order of importance, elements for high quality planetary views: Optical quality of eyepiece Optical quality of telescope Collimation of optics Steadiness of atmosphere (seeing) Thermal equilibrium of optics Using high-magnification eyepiece.

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Newtonian Collimation

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  1. Newtonian Collimation Marc Feuerberg

  2. Rank, in order of importance, elements for high quality planetary views: • Optical quality of eyepiece • Optical quality of telescope • Collimation of optics • Steadiness of atmosphere (seeing) • Thermal equilibrium of optics • Using high-magnification eyepiece

  3. Rank, in order of importance, elements for high quality planetary views: • Optical quality of eyepiece • Optical quality of telescope • Collimation of optics • Steadiness of atmosphere (seeing) • Thermal equilibrium of optics • Using high-magnification eyepiece Answer: reverse order

  4. Coma-free diameter at focal plane is equal to focal ratio, cubed, times .022 • F10 = (10^3)*.022 = 22mm • F5 = (5^3)*.022 = 2.8mm • F4 = (4^3)*.022 = 1.4mm

  5. 3 Steps: • Align focuser with secondary • Align secondary with primary • Align primary with focuser

  6. 1. Align focuser with secondary • Use single-beam laser • Use cheshire • Use long drawtube with pinhole

  7. 2. Align secondary with primary • Laser – single beam point to center spot • Cheshire – center whole primary

  8. 3. Align primary with focuser/eyepiece • Laser – return single beam hits center of eyepiece (not recommended) • Barlowed Laser – shadow of donut (center spot) hits center of eyepiece • Cheshire – center return reflection of center spot/donut

  9. Cheshire – all 3 steps • Laser – return beam hits center of eyepiece • Barlowed Laser – shadow of donut (center spot) hits center of eyepiece • Cheshire – center return reflection of center spot/donut

  10. Step 3: manual adjustments

  11. What’s important? • Step 1 alignment? No. • Step 2 alignment? No. • Step 3 alignment? Yes! • Primary and secondary stable? Yes!

  12. What’s important? • Using laser good for step 3? No. • Due to focuser/drawtube sensitivity • Using barlowed laser for step 3? Yes! • Using cheshire for step 3? Yes!

  13. Other tips • Check primary alignment (step 3) at • Multiple scope altitude positions • Multiple temperatures • Can do a star test on Polaris as a double-check • Proper collimation incorporates proper secondary offset

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