Update 23 April 2026
Maximum speed and precision connecting thermal clip-on devices to any rifle scope with the modular adapter by Rusan
Disclaimer: Thermal clip-on viewers such as the Leica Calonox Sight or Pulsar Krypton are observation instruments. They can also be used in combination with a pointing scope through an adapter. When used in the latter function, they are suitable for night shooting. We recommend checking any possible legislation restrictions to the ownership and/or usage of such products in your area.
From observation to aiming with the Rusan one-piece adapter
We discuss the adapter for the Leica Calonox Sight 2 because it is perhaps the best thermal clip-on on the market as an observation device. It allows you to observe with the quality and comfort of a purely observation viewer. At the same time, it is designed to be a perfect clip-on for your pointing scope. When engaged in night hunting, it is very convenient to observe animals with the Calonox Sight 2. Then you can apply it to the objective of the riflescope when needed at the moment of shooting. However, the same applies to any model and brand of thermal clip-on devices on the market.
How to switch to aiming mode
To switch to aiming mode, unscrew or remove the eyecup. Then screw the adapter in its place to attach the thermal clip-on device to the objective of the scope. You can do this with any scope of any brand. Moreover, this operation can be done easily even in the dark.
The adapter slips onto the objective and is fixed simply by closing its locking lever with a finger. The large buttons in the center of the top part of the thermal unit then allow you to position the instrument well centered. This centering is relative to the scope reticle. A necessary condition to see the scope’s crosshairs perfectly straight. Simply use the tactile sensation of having them in line with the scope itself.
Superior materials and manufacturing precision
The Rusan adapter is made of metal. It is manufactured with diameter dimensions that vary by 1mm or even less from one model to another. This ensures perfect compatibility with any rifle scope. The quality of materials and workmanship result in an adapter that guarantees a granite-like assembly. Furthermore, the adapter offers highly precise and extremely stable connection of the thermal clip-on device to the scope.
Multiple tests have been performed with dozens of shots. Even after removing and reinserting the Leica Calonox 2 with the adapter on the scope objective, the point of impact changed by no more than 1 cm at 100 meters. This is the European approach to quality. Obviously, such reliability depends on the quality of materials and assembly. It ultimately reflects the quality control of the device you are using.
Here is a video showing how the Rusan adapter works.
The adapter for clip-on devices is distributed by Forest Italia and costs €180 (arm 52-) or €190 (arm 43-), VAT included. It can be ordered directly here. For information contact info@forestitalia.com – 045 8778772. When ordering, it is recommended to provide the model of the rifle scope to be associated with the clip-on device.
Observation options with minimal setup changes
For those who need faster transition from observation to aiming, you can further reduce the times. First, observe without the eyecup. This does not create any problem with image quality. Alternatively, you can screw the Rusan adapter onto the eyepiece of the thermal device. In this case, the eye will be forced to stay slightly further from the eyepiece itself. However, this does not compromise its observation functionality.
Maximum speed and precision for connection with the modular Rusan adapter
Rusan has produced a two-piece modular adapter. This design offers three advantages compared to the standard one-piece model.
How the modular adapter works
The Rusan modular adapter is composed of two parts. The first is a ring called MCR-M52 (or MCR-M43, depending on your device). This ring screws onto the eyepiece of the thermal clip-on device. It can remain screwed onto the eyepiece even during observation. The second part is the rest of the adapter. It slips onto and fixes to the objective of the scope. This part is identical for any clip-on device. It is called MAR-.., where the dots represent the external diameter of the scope objective onto which it is mounted.
Close with a finger the appropriate lever once the adapter is fully inserted. Ensure it is centered with the white arrow at 12 o’clock relative to the scope objective.
Using the modular adapter for observation
To use the clip-on device for observation, the Rusan ring screwed onto the eyepiece certainly does not offer the comfort of the soft rubber eyecup. However, compared to the one-piece adapter it allows you to keep your eye at the optimal distance from the lens.
Extremely fast attachment process
The attachment of the thermal clip-on device to the rifle scope with the modular adapter is extremely fast. The white arrow on the Rusan ring screws onto the thermal clip-on device eyepiece. This arrow indicates where to insert it in correspondence with the white arrow on the Rusan tube mounted on the scope objective. Then simply rotate the sliding locking ring less than a quarter turn in a bayonet lock on the eyepiece ring.
Perfect alignment guaranteed
The further advantage of this adapter is that the ring (with the thermal device) has a fixed insertion position. This ensures the device is positioned perfectly in line with the aiming line. You avoid further adjustments to get the reticle perfectly aligned with the screen of the thermal device.
Click here for the link to Rusan’s video on how the modular adapter works.
The Rusan modular adapter is distributed by Forest Italia Srl and costs €255, VAT included (€180/190 for the standard one). It can be ordered directly here, or at the best gun shops. For information contact info@forestitalia.com – 045 8778772. When ordering, it is recommended to provide the model of the rifle scope to be associated with the thermal device, or to indicate the external diameter of the scope objective based on the tables shown below.
The advantages of the modular adapter, in summary
- Full observation capability with Rusan ring mounted: You can use the thermal clip-on device for observation with the Rusan ring mounted and remain ready to apply it quickly to the scope. Moreover, you enjoy the entire field of view perfectly. If you do the same with the Rusan one-piece adapter mounted on the thermal clip-on device, the thickness of the adapter tube makes observation less convenient.
- Extremely fast transition from observation to aiming: The transition is extremely fast with this adapter. Simply insert the thermal clip-on device with the Rusan ring in the correct position. The white arrows on the ring and the other part of the adapter mounted on the scope indicate proper alignment. Then rotate the locking ring less than a quarter turn. Two seconds is all it takes.
- Thermal clip-on device attaches already perfectly aligned: This is the least intuitive but most important advantage compared to using the one-piece adapter. With the latter, you must ensure that the thermal clip-on device is centered relative to the scope’s aiming line. Otherwise, the scope’s reticle will appear rotated. The fixed insertion position of the ring on the rest of the adapter allows you to perfectly center the part to be fixed on the scope. Therefore, when you insert the thermal clip-on device it will be immediately perfectly centered. This is another important time saving, especially at night.
Given the quality of materials, design and workmanship, the centering retention of the modular adapter against recoil is guaranteed. Assembly and disassembly operations will not affect this precision.
On the other hand, the modular adapter costs €255 compared to €180/190 for the one-piece version. Additionally, for pure observation, the rubber eyecup of the device is certainly more comfortable and pleasant.
Here is a video tutorial on how to mount the modular adapter.
The Rusan 2.5x eyepiece for best observation, with diopter adjustment included
Rusan has produced a small (6cm by 90g) high-quality eyepiece with diopter adjustment. It offers 2.5x magnification and attaches via bayonet to the ring part of the Rusan modular adapter. This transforms the thermal clip-on device into an observation viewer truly at the same level as pure observation viewers. Here you will find all the details.
