Astronomy Focuser

1.25-inch Double Focusing Base M42 for Astronomical Telescopes

Name: 1.25-inch Double Focusing Base M42 for Astronomical Telescopes
Brand: AMADA Microscope

The 1.25-inch double-threaded focusing base with M42x0.75 top and bottom threads provides a 10mm linear adjustment stroke for precise focus control in astronomical telescopes.

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1.25-inch Double Focusing Base M42 for Astronomical Telescopes

Product Overview

The 1.25-inch double-threaded focusing base with M42x0.75 top and bottom threads provides a 10mm linear adjustment stroke for precise focus control in astronomical telescopes. It is constructed entirely of metal, ensuring durability and stability during long exposure imaging. The double helix mechanism allows the eyepiece or zenith mirror to move straight without rotating, maintaining alignment during fine focusing at high magnifications.

Inside diameter1.25"
Stroke10mm
Adjustment accuracy0.05mm
Top external threadM42x0.75
Bottom external threadM42x0.75
Bottom inner ring external threadM31x0.5

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Key Benefits

10mm linear adjustment stroke with 0.05mm accuracy for precise focus control
Double helix mechanism prevents rotation of eyepiece or mirror during focusing
All-metal construction ensures rigidity and long-term durability
M42x0.75 top and bottom threads match common guide and finder mirror interfaces
Compact design fits within tight telescope tube spaces, with height from 46mm to 56mm
Smooth operation even at high magnifications, reducing focus drift during observation

Application Scenarios

Fine focusing during planetary or lunar imaging with a CCD camera
Adjusting focus on a finder scope or guide scope without disturbing alignment
Mounting a zenith mirror in a refractor or catadioptric telescope with stable linear movement
Using with a telephoto lens on a telescope for astrophotography with minimal backlash
Repositioning a guide mirror during long-exposure imaging without rotation

Who It Is For

Amateur astronomers doing planetary and deep-sky imaging
Educational astronomy labs using refractors or catadioptric telescopes
Astrophotography setups requiring stable, non-rotating focus mechanisms
Telescope builders and integrators working with guide scopes and finder systems
Users of telephoto lenses adapted for astronomical use

Problems It Solves

A rotating eyepiece or mirror during focus adjustment disrupts alignment in imaging setups
Standard focusers with single threads introduce backlash and inconsistent movement
Lack of fine adjustment in low-precision focusers leads to missed focus points at high magnifications
Non-metal focusers deform under repeated use or thermal stress
Incompatible thread sizes force the use of adapters that add play and misalignment

Technical Features

Double helix focusing mechanism for smooth, backlash-free motion
Linear movement only - no rotation of inserted components during adjustment
High-precision construction with 0.05mm adjustment accuracy
Top and bottom threads both M42x0.75 for compatibility with guide and finder mirrors
Inner ring thread M31x0.5 for mounting accessories or retaining rings
1.25-inch inside diameter fits standard eyepieces and accessories
Adjustment stroke of 10mm for sufficient range across focus zones
Minimum height 46mm, maximum height 56mm for compact integration
All-metal construction ensures mechanical stability under thermal and mechanical load

Specifications

Inside diameter	1.25"
Stroke	10mm
Adjustment accuracy	0.05mm
Top external thread	M42x0.75
Bottom external thread	M42x0.75
Bottom inner ring external thread	M31x0.5
Minimum height	46mm
Maximum height	56mm
Material	All metal
Focusing mechanism	Double helix
Movement type	Linear only
Compatibility	Guide mirror, finder mirror, CCD eyepiece, zenith mirror

Specifications are taken from the AMADA product data for this item. Confirm critical dimensions with us in writing before ordering.

Customization Options

Available with or without the M31x0.5 inner ring thread
Option to modify thread size on top or bottom if required for specific integration
Surface finish can be specified upon request (e.g. black anodized, polished)

Comparison With Other Options

Single-threaded focusing base	The double helix design reduces backlash and provides smoother, more precise linear movement compared to single-thread systems, which can introduce play during focus adjustment.
Plastic or hybrid focuser	The all-metal construction ensures long-term rigidity and resistance to thermal expansion, unlike plastic focusers that may deform under repeated use or temperature changes.
Standard 1.25-inch focuser without double helix	This model maintains alignment during focus by preventing rotation of the inserted component; standard focusers often allow slight rotation, which disrupts alignment in imaging setups.

Use Guide

Ensure the 1.25-inch accessory is fully seated before adjusting focus
Turn the focusing knob slowly to avoid overshooting the focus point
Use the 10mm stroke for fine adjustments - do not exceed the mechanical limits
Check that the M42x0.75 threads are clean and free of debris before mounting
For imaging, lock the focuser after reaching focus to prevent drift during exposure