Celestron 1.25" 2x Ultima Barlow ('shorty', 1999) retaining screw screw size
M3 · length not stated in the sources
The screws used on Celestron 1.25" 2x Ultima Barlow ('shorty', 1999) retaining screw are M3. None of the sources we found gives an exact length, so measure the original before you order.
It is listed for database entry: 'Celestron 1.25" 2x Ultima Barlow "shorty," 1999 (1) M3-.5'.
This entry is marked confirmed and comes from scopestuff.com.
M3 means a 3 mm nominal diameter with a 0.5 mm thread pitch. Imperial look-alike: #5-40 (3.18 mm) or #4-40 — neither interchanges with M3.
Celestron 1.25" 2x Ultima Barlow ('shorty', 1999) retaining screw screw specifications
One row per fitment record. Head, drive are shown only where the source states them; pitch is the ISO coarse pitch for the thread.
| Thread | Length | Pitch | Head | Drive | Where it goes | Status |
|---|---|---|---|---|---|---|
| M3 | not stated | 0.5 mm | not stated | not stated | Database entry: 'Celestron 1.25" 2x Ultima Barlow "shorty," 1999 (1) M3-.5' | Confirmed |
Fitment records and sources
M3confirmed
Database entry: 'Celestron 1.25" 2x Ultima Barlow "shorty," 1999 (1) M3-.5'
pitch 0.5 mm · tap 2.5 mm · clearance 3.4 mm · PH1 / Torx T10
How to check the screw before you buy
- Camera and optics hardware often uses short screws into thin threaded plates, so check engagement before tightening fully.
- Diameter: across the threads an M3 screw measures about 3 mm with calipers (usually a hair under). If yours measures noticeably more or less, it is a different thread.
- Pitch: 0.5 mm from one thread crest to the next (20 crests per centimetre). A thread pitch gauge or the pitch-gauge tool settles it in seconds.
- Length: measure from under the head to the tip for pan, button, wafer and cap heads; countersunk (flat) heads are measured overall.
- Driver: the source does not name the drive. Standard M3 heads take PH1 for Phillips and T10 for Torx, and a 2.5 mm hex key for socket heads; a bit that fits loosely will cam out and strip the head.
- Tightening: no device-specific torque is published in these records. The site's general figure for M3 is about 80-130 N·cm into metal threads and 35-60 N·cm into plastic bosses; snug it up and stop.
Common mix-ups with M3
- Telescope thumbscrews are sold in a wide non-metric legacy range too (1/4-20, 8-32, 10-32 on many Meade/Celestron mounts), so metric M3/M4 fitment applies mainly to newer/international accessory ecosystems (SkyWatcher, generic 1.25" accessories) and should not be assumed universal.
- Drill chuck retaining screws are commonly LEFT-HAND thread (e.g. M6 x 1.0 LH) — turn clockwise to remove.
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Devices whose records share a thread with Celestron 1.25" 2x Ultima Barlow ('shorty', 1999) retaining screw, closest length match first.
- Celestron EdgeHD 8" OTA secondary mirror collimation screws also M3
- Newport MM-050-HEX-M platform optical mount also M3
- Edmund Optics 30mm Universal Cage Plate also M3
- Aimpoint Micro T-1/T-2/H-1/H-2 standard mount also M3
- Arca-style quick-release plate also M3
- Celestron C8 Schmidt-Cassegrain OTA secondary mirror collimation screws also M3
- Shield Sights optic-ready / dovetail red dot mounts also M3
- Telescope metric thumb screw for telescope parts also M3
Questions about Celestron 1.25" 2x Ultima Barlow ('shorty', 1999) retaining screw screws
- What size screw does Celestron 1.25" 2x Ultima Barlow ('shorty', 1999) retaining screw use?
- M3 for database entry: 'Celestron 1.25" 2x Ultima Barlow "shorty," 1999 (1) M3-.5'.
- How long are the screws in Celestron 1.25" 2x Ultima Barlow ('shorty', 1999) retaining screw?
- None of the sources states a length. Remove one screw and measure it from under the head to the tip (overall for a countersunk head).
- What is the thread pitch of an M3 screw?
- 0.5 mm (coarse), which is the standard pitch for M3 machine screws; a 0.35 mm fine pitch exists but is uncommon. The tap drill is 2.5 mm and the normal clearance hole is 3.4 mm.
- What screwdriver do I need for Celestron 1.25" 2x Ultima Barlow ('shorty', 1999) retaining screw?
- The sources do not name the drive. For M3, Phillips heads normally take PH1 and Torx heads T10; socket heads take a 2.5 mm hex key.
- Can I use an imperial screw instead of M3?
- No. Imperial look-alike: #5-40 (3.18 mm) or #4-40 — neither interchanges with M3. Use a true M3 screw so it does not cross-thread or strip the hole.