CELESTRON 8” SCT: STANDARD OR METRIC?
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Example 1: Black Phillips Collimation Screws
Textured secondary surface with serial number sticker and “CELESTRON” imprint in upper case lettering. Collimation screws are surrounded by a thin ring of smooth plastic and are slightly countersunk into the secondary housing. This is the most common black Phillips configuration.
Type of collimation screw: Metric
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Example 2: Black Phillips Collimation Screws
Textured secondary surface with serial number sticker and 'Celestron' imprint in upper and lower case lettering. Collimation screws are surrounded by normal surface texturing and are not countersunk.
Type of collimation screw: Standard
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Example 3: Black Phillips Collimation Screws
Nearly smooth secondary surface with serial number sticker but no “Celestron” imprint. Screws are slightly countersunk.
Type of collimation screw: Can be either Standard or Metric
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Example 4: Black Phillips Collimation Screws
Smooth secondary surface with serial number sticker and “CELESTRON” imprint in upper case lettering. Screws are slightly countersunk.
Type of collimation screw: Can be either Standard or Metric
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Example 5: Black Phillips Collimation Screws
Fastar secondary with label. Scope can be either with or without EdgeHD optics. (Note: EdgeHD and non-EdgeHD require different knobs.)
Type of collimation screw: Metric
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Example 6: Black Phillips Collimation Screws
Hyperstar compatible secondary. Collimation screws are deeply countersunk into the secondary housing.
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Please contact us using the link below for guidance if you have further questions.
- Celestron C8 Xlt Ota
- Celestron Orange Tube C8
- Celestron C8 Serial Numbers
- Celestron C8 Serial Number Lookup
- Celestron Classic C8 Telescope
Serial number aside, the “ribbed” rear cell indicated this wasn’t no spring chicken. Another tip-off to the C8’s vintage was the weird stuff on the top of the tube. There was a camera piggyback bracket on the rear cell and a corresponding aluminum block on the corrector assembly. In 1987 Celestron production numbers were reduced while the quality was improved. Some of the production cuts were ordered by Alan Hale to allow production technique improvements to be instituted, while some reductions were simply due to waning demand as the post Comet Halley industry-wide hangover revealed the market was saturated. The optics of the Celestron C8 N Advanced Series Telescopes 31061 are manufactured to Celestron's uncompromising standards. The C8-N uses diffraction-limited parabolic primary mirrors for razor sharp star images across a wide field of view. Celestron C-8N Advanced Series Telescope 31061 is mounted on the very rigid CG-5 German equatorial mount. A counterweight, latitude scale, setting circles.
Special Note: The Celestron SCT uses either standard 6-32 or metric M3 collimation screws. It is important to order the correct knobs for your telescope. Allen and set-style factory collimation screws have standard threads. For Phillips collimation screws, the general rule is: Silver are standard; Black are metric. There are exceptions to this rule for black Phillips screws, so we have developed some hints to help you to determine which type of black Phillips collimation screw your telescope uses. Moreover, there are even exceptions to the hints, so if you are unsure of the type of screw in your telescope, you can either 1) pull a single collimation screw and check its threads using the guidelines at the bottom of this page; or 2) order both standard and metric knobs and return those that aren’t needed for a full refund._______________________________
Example 1: Black Phillips Collimation Screws
Textured secondary surface with serial number sticker and “CELESTRON” imprint in upper case lettering. Collimation screws are surrounded by a thin ring of smooth plastic and are slightly countersunk into the secondary housing. This is the most common black Phillips configuration.
Type of collimation screw: Metric
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Example 2: Black Phillips Collimation Screws
Textured secondary surface with serial number sticker and 'Celestron' imprint in upper and lower case lettering. Collimation screws are surrounded by normal surface texturing and are not countersunk.
Type of collimation screw: Standard
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Celestron C8 Xlt Ota
Example 3: Black Phillips Collimation Screws
Nearly smooth secondary surface with serial number sticker but no “Celestron” imprint. Screws are slightly countersunk.
Type of collimation screw: Can be either Standard or Metric
_______________________________
Example 4: Black Phillips Collimation Screws
Smooth secondary surface with serial number sticker and “CELESTRON” imprint in upper case lettering. Screws are slightly countersunk.
Type of collimation screw: Can be either Standard or Metric
_______________________________
Example 5: Black Phillips Collimation Screws
Fastar secondary with label. Scope can be either with or without EdgeHD optics. (Note: EdgeHD and non-EdgeHD require different knobs.)
Type of collimation screw: Metric
_______________________________
Example 6: Black Phillips Collimation Screws
Hyperstar compatible secondary. Collimation screws are deeply countersunk into the secondary housing.
Celestron Orange Tube C8
Type of collimation screw: MetricCelestron C8 Serial Numbers
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Celestron C8 Serial Number Lookup
Celestron Classic C8 Telescope
If you decide to remove a Celestron 8” SCT collimation screw, here's how to determine if the screw has standard or metric threads. (Our knobs are shown in the photograph.) Both factory screws have about the same thread length below the screw head. The metric screw is slightly smaller in diameter, but that isn't really helpful without having samples of both screws. The best way to determine screw type is to count threads. The standard screw has about 10 thread turns over its 5/16 inch length, and the metric screw has about 16 thread turns over its 8 mm length. (Exception: The C8 EdgeHD with black Phillips collimation screws and the Fastar secondary has a longer 12 mm black Phillips secondary collimation screw. This screw is metric with 24 thread turns over its length.)Please contact us using the link below for guidance if you have further questions.