The world of adapters is diverse and not easy to understand. This is due to the wide variety of thread and plug sizes that optics and accessories may have.
In astronomy, two plug sizes have become established, which are often indicated in the old unit inches ("):
- 1.25" corresponds to 31.8 millimetre
- 2" corresponds to 50.8 millimetres
Many eyepieces, but also cameras, have connectors in one of these two sizes, which can be inserted into the telescope’s focuser.
If a 1.25" connector is to be inserted in a focuser with a 2" connector, a 1.25"/2" adapter is required. This is an example of a reducer adapter: where a connection is reduced from a larger size to a smaller one. The reverse is called an extension adapter.
Another very important category of adapters is camera adapters. These are used to connect cameras to optics or to accessories. The T2 thread (M42x0.75), which enables a screw connection, is very well established for this purpose. Lighter cameras without many accessories can also be easily connected to the telescope via a socket.
For astrophotography it is important that the aperture is large enough to illuminate the sensor (no vignetting) and the optical length matches the focal point.
![Omegon 2“ Extension tube, 35mm optical path](/Produktbilder/normal/54437_1/Omegon-2l-Extension-tube-35mm-optical-path.jpg)
Omegon
2“ Extension tube, 35mm optical path
$ 29.90
![Omegon 2'' extension tube with 50mm optical path](/Produktbilder/normal/55072_1/Omegon-2-extension-tube-with-50mm-optical-path.jpg)
Omegon
2'' extension tube with 50mm optical path
$ 39.90
![Omegon 1.25'', 30mm extension tube](/Produktbilder/normal/33231_1/Omegon-1-25-30mm-extension-tube.jpg)
Omegon
1.25'', 30mm extension tube
$ 19.90
![Omegon extension tube 45mm 2''](/Produktbilder/normal/81073_1/Omegon-extension-tube-45mm-2-.jpg)
Omegon
extension tube 45mm 2''
$ 29.90
![ASToptics Extension Tube - M48 - Filter thread - 10mm Length](/Produktbilder/normal/57633_1/ASToptics-Extension-Tube-M48-Filter-thread-10mm-Length.jpg)
ASToptics
Extension Tube - M48 - Filter thread - 10mm Length
$ 27.90
![TeleVue 0.50" Length Accessory Tube for 2.4"](/Produktbilder/normal/19093_1/TeleVue-0-50-Length-Accessory-Tube-for-2-4-.jpg)
TeleVue
0.50" Length Accessory Tube for 2.4"
$ 66.00
![Omegon 2'' extension tube, 80mm optical path](/Produktbilder/normal/54438_1/Omegon-2-extension-tube-80mm-optical-path.jpg)
Omegon
2'' extension tube, 80mm optical path
$ 49.90
![ASToptics Extension tube M48 Fine tuning Kit - 0.5mm; 0.8mm; 1mm](/Produktbilder/normal/57846_1/ASToptics-Extension-tube-M48-Fine-tuning-Kit-0-5mm-0-8mm-1mm.jpg)
ASToptics
Extension tube M48 Fine tuning Kit - 0.5mm; 0.8mm; 1mm
$ 27.90
![ASToptics T2 extension tube - 6mm long](/Produktbilder/normal/57865_1/ASToptics-T2-extension-tube-6mm-long.jpg)
ASToptics
T2 extension tube - 6mm long
$ 27.90
![ASToptics Extension Tube M48 Filter thread - 4mm Length](/Produktbilder/normal/57776_1/ASToptics-Extension-Tube-M48-Filter-thread-4mm-Length.jpg)
ASToptics
Extension Tube M48 Filter thread - 4mm Length
$ 22.90
![ASToptics T2 extension tube - 9mm in length](/Produktbilder/normal/57641_1/ASToptics-T2-extension-tube-9mm-in-length.jpg)
ASToptics
T2 extension tube - 9mm in length
$ 27.90
![ASToptics Extension Tube M48 - 2" - Filter thread - 16mm Length](/Produktbilder/normal/57843_1/ASToptics-Extension-Tube-M48-2-Filter-thread-16mm-Length.jpg)
ASToptics
Extension Tube M48 - 2" - Filter thread - 16mm Length
$ 38.90
![ASToptics T2 extension tube - 4mm long](/Produktbilder/normal/57864_1/ASToptics-T2-extension-tube-4mm-long.jpg)
ASToptics
T2 extension tube - 4mm long
$ 22.90
![ASToptics Extension tube T2 Fine tuning Kit - 0.5mm; 0.8mm; 1mm](/Produktbilder/normal/57846_1/ASToptics-Extension-tube-T2-Fine-tuning-Kit-0-5mm-0-8mm-1mm.jpg)
ASToptics
Extension tube T2 Fine tuning Kit - 0.5mm; 0.8mm; 1mm
$ 27.90
![ASToptics Extension Tube M48 Filter thread - 11mm Length](/Produktbilder/normal/57784_1/ASToptics-Extension-Tube-M48-Filter-thread-11mm-Length.jpg)
ASToptics
Extension Tube M48 Filter thread - 11mm Length
$ 33.90
![ASToptics M54*0.75 - 5MM extension ring](/Produktbilder/normal/57936_1/ASToptics-M54%2A0-75-5MM-extension-ring.jpg)
ASToptics
M54*0.75 - 5MM extension ring
$ 33.90
![ASToptics Extension Tube M48 Filter thread - 7.5 mm Length](/Produktbilder/normal/57777_1/ASToptics-Extension-Tube-M48-Filter-thread-7-5-mm-Length.jpg)
ASToptics
Extension Tube M48 Filter thread - 7.5 mm Length
$ 27.90
![ASToptics T2 extension tube - 7mm long](/Produktbilder/normal/57672_1/ASToptics-T2-extension-tube-7mm-long.jpg)
ASToptics
T2 extension tube - 7mm long
$ 27.90
![Paton Hawksley Extension tube Spacer SA](/Produktbilder/normal/54302_1/Paton-Hawksley-Extension-tube-Spacer-SA.jpg)
Paton Hawksley
Extension tube Spacer SA
$ 22.90
![ASToptics Extension tube M48 - Filter thread - 5mm long](/Produktbilder/normal/57637_1/ASToptics-Extension-tube-M48-Filter-thread-5mm-long.jpg)
ASToptics
Extension tube M48 - Filter thread - 5mm long
$ 22.90
![ASToptics Extension tube Variable M48 extender, 23-29mm](/Produktbilder/normal/57790_1/ASToptics-Extension-tube-Variable-M48-extender-23-29mm.jpg)
ASToptics
Extension tube Variable M48 extender, 23-29mm
$ 77.00
![ASToptics T2 extension tube - 30mm](/Produktbilder/normal/57673_1/ASToptics-T2-extension-tube-30mm.jpg)
ASToptics
T2 extension tube - 30mm
$ 33.90
![ASToptics Extension Tube M48 Filter thread - 25mm Length 2"](/Produktbilder/normal/57828_1/ASToptics-Extension-Tube-M48-Filter-thread-25mm-Length-2-.jpg)
ASToptics
Extension Tube M48 Filter thread - 25mm Length 2"
$ 56.00
![ASToptics M54*0.75 - 8mm extension ring](/Produktbilder/normal/57935_1/ASToptics-M54%2A0-75-8mm-extension-ring.jpg)
ASToptics
M54*0.75 - 8mm extension ring
$ 33.90
![ASToptics T2 Extension tube - 5mm long](/Produktbilder/normal/57643_1/ASToptics-T2-Extension-tube-5mm-long.jpg)
ASToptics
T2 Extension tube - 5mm long
$ 22.90
![ASToptics T2 extension tube - 12mm long](/Produktbilder/normal/57911_1/ASToptics-T2-extension-tube-12mm-long.jpg)
ASToptics
T2 extension tube - 12mm long
$ 33.90
![ASToptics T2 extension tube - 8mm long](/Produktbilder/normal/57872_1/ASToptics-T2-extension-tube-8mm-long.jpg)
ASToptics
T2 extension tube - 8mm long
$ 27.90
![ASToptics Extension Tube M48 - 2'' - Filter thread - 9 mm Length](/Produktbilder/normal/57939_1/ASToptics-Extension-Tube-M48-2-Filter-thread-9-mm-Length.jpg)
ASToptics
Extension Tube M48 - 2'' - Filter thread - 9 mm Length
$ 27.90
![ASToptics T2 extension tube - 15mm long](/Produktbilder/normal/57639_1/ASToptics-T2-extension-tube-15mm-long.jpg)
ASToptics
T2 extension tube - 15mm long
$ 38.90
![Artesky Extension tube Fine Tuning Ring Set M54](/Produktbilder/normal/69993_1/Artesky-Extension-tube-Fine-Tuning-Ring-Set-M54.jpg)
Artesky
Extension tube Fine Tuning Ring Set M54
$ 32.90
![Artesky Extension tube Fine Tuning Ring Set M48](/Produktbilder/normal/69993_1/Artesky-Extension-tube-Fine-Tuning-Ring-Set-M48.jpg)
Artesky
Extension tube Fine Tuning Ring Set M48
$ 32.90
![Artesky Extension tube Fine Tuning Ring Set T2](/Produktbilder/normal/69993_1/Artesky-Extension-tube-Fine-Tuning-Ring-Set-T2.jpg)
Artesky
Extension tube Fine Tuning Ring Set T2
$ 27.90
![ASToptics Extension tube M48 (2") fine tuning ring - 1mm (aluminium)](/Produktbilder/normal/57660_1/ASToptics-Extension-tube-M48-2-fine-tuning-ring-1mm-aluminium-.jpg)
ASToptics
Extension tube M48 (2") fine tuning ring - 1mm (aluminium)
$ 7.90
![ASToptics Extension tube M48 (2") fine tuning ring - 2mm (aluminium)](/Produktbilder/normal/57867_1/ASToptics-Extension-tube-M48-2-fine-tuning-ring-2mm-aluminium-.jpg)
ASToptics
Extension tube M48 (2") fine tuning ring - 2mm (aluminium)
$ 11.90
![ASToptics Extension tube T2 fine tuning ring - 2mm (aluminium)](/Produktbilder/normal/57662_1/ASToptics-Extension-tube-T2-fine-tuning-ring-2mm-aluminium-.jpg)
ASToptics
Extension tube T2 fine tuning ring - 2mm (aluminium)
$ 6.90
![ASToptics Extension tube T2 fine tuning ring - 1mm (aluminium)](/Produktbilder/normal/57657_1/ASToptics-Extension-tube-T2-fine-tuning-ring-1mm-aluminium-.jpg)