Meade 1.25" diagonal prism, Telenegative Barlow #122, 2" diagonal screw size
M3 · length not stated in the sources
If you are replacing a screw on Meade 1.25" diagonal prism, Telenegative Barlow #122, 2" diagonal, the thread is M3. None of the sources we found gives an exact length, so measure the original before you order.
The record covers multiple Meade eyepiece-accessory retaining screws listed as M3-.5 in the ScopeStuff database.
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.
Meade 1.25" diagonal prism, Telenegative Barlow #122, 2" diagonal 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 | Multiple Meade eyepiece-accessory retaining screws listed as M3-.5 in the ScopeStuff database | Confirmed |
Fitment records and sources
M3confirmed
Multiple Meade eyepiece-accessory retaining screws listed as M3-.5 in the ScopeStuff database
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.
- Camera and tripod mounting threads themselves are imperial 1/4in-20 or 3/8in-16 — the metric M2-M4 screws in rig kits are only for the accessory hardware, not the tripod mount.
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Devices whose records share a thread with Meade 1.25" diagonal prism, Telenegative Barlow #122, 2" diagonal, closest length match first.
- Wooden Camera 153250 SSD Guard (RED EPIC) also M3
- Celestron collimation screws, C5/C6/C8 SCT optical tubes also M3
- Gimbal / quick-release plate clamp also M3
- Telescope accessory thumb screws also M3
- Celestron 1.25in Ultima Barlow (1999) also M3
- Samsara CM33 / CM34 dashcam mount also M3
- Universal Red Dot Pattern Mounting Plate (fits Vortex Viper, Burris Fast Fire 3, UTG Reflex Micro Dot, TruGlo Tru-Tec, Crimson Trace CTS-1250, Springfield Dragonfly) also M3
- Celestron EdgeHD 14" OTA secondary mirror collimation screws also M3
Questions about Meade 1.25" diagonal prism, Telenegative Barlow #122, 2" diagonal screws
- What size screw does Meade 1.25" diagonal prism, Telenegative Barlow #122, 2" diagonal use?
- M3 for multiple Meade eyepiece-accessory retaining screws listed as M3-.5 in the ScopeStuff database.
- How long are the screws in Meade 1.25" diagonal prism, Telenegative Barlow #122, 2" diagonal?
- 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 Meade 1.25" diagonal prism, Telenegative Barlow #122, 2" diagonal?
- 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.