Update 23 April 2026
Maximum speed and precision connecting any thermal clip-on device to any rifle scope, with the MODULAR ADAPTER by Rusan
Disclaimer: Thermal clip-on viewers such as the Leica Calonox Sight or Pulsar Krypton etc.. are observation instruments, which 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 to check 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, because it allows you to observe with the quality and comfort of a purely observation viewer, while being designed to be a perfect clip-on to apply to the pointing scope. When you are engaged in night hunting, it is very convenient to be able to observe animals with the Calonox Sight 2, and then apply it to the objective of the riflescope when needed at the moment of shooting. Nevertheless, the same applies to any model and brand of thermal clip-on devices on the market.
To switch to aiming mode, unscrew/remove the eyecup and screw the adapter in its place to attach the thermal clip-on device to the objective of the scope, any scope of any brand, an operation that 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 with respect to the scope (a necessary condition to see the scope’s reticle with the crosshairs perfectly straight), simply with the tactile sensation of having them in line with the scope itself.
The Rusan adapter is made of metal, manufactured with diameter dimensions that vary by 1mm or even less from one model to another, to ensure perfect compatibility with any rifle scope. The quality of materials and workmanship result in an adapter that guarantees a granite-like, highly precise and extremely stable assembly of the thermal clip-on device connected to the scope. Multiple tests have been performed with dozens of shots, even removing and reinserting the Leica Calonox 2 with the adapter on the scope objective, without the point of impact changing by more than 1 cm at 100 meters. This is the European approach to quality. Obviously, such a reliability depends on the quality of materials and assembly, ultimately 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 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
For those who need faster transition from observation to aiming, it is possible to further reduce the times by observing without the eyecup, which does not create any problem with image quality, or even with the Rusan adapter already screwed onto the eyepiece of the thermal device, in which case the eye will be forced to stay slightly further from the eyepiece itself, but without compromising its observation functionality.
Maximum speed and precision for connection, with the MODULAR RUSAN ADAPTER.
Rusan has produced a two-piece modular adapter that offers three advantages compared to the standard one-piece model.
How the modular adapter works.
The Rusan modular adapter is composed of two parts: a ring called MCR-M52 (or MCR-M43, depending on your device) that screws onto the eyepiece of the thermal clip-on device and which can remain screwed onto the eyepiece even during observation, and the rest of the adapter that slips onto and fixes to the objective of the scope (and is therefore identical for any clip-on device), it is called MAR-.. (dots represent the external diameter of the scope onto which it is mounted), closing with a finger the appropriate lever once the adapter is fully inserted, ensuring it is centered with the white arrow at 12 o’clock relative to the scope objective.
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, but compared to the one-piece adapter it allows you to keep your eye at the optimal distance from the lens.
The attachment of the thermal clip-on device to the rifle scopes with the modular adapter is extremely fast: The white arrow on the Rusan ring that screws onto the thermal clip-on device eyepiece 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.
The further advantage of this adapter is that the ring (with the thermal device) has a fixed insertion position, which ensures the device is positioned perfectly in line with the aiming line, avoiding 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 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
- You can use the thermal clip-on device for observation with the Rusan ring mounted, to be ready to apply it quickly to the scope, enjoying 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.
- The transition from observation to aiming with the thermal clip-on device is extremely fast. Simply insert the thermal clip-on device with the Rusan ring in the correct position (indicated by the white arrows on the ring and the other part of the adapter mounted on the scope) and rotate the locking ring less than a quarter turn. Two seconds.
- The thermal clip-on device attaches already perfectly aligned with the scope. 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 to the right or left. 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 before exiting, and thus be certain that when you go to insert the thermal clip-on device it will be immediately perfectly centered. Another important time saving, especially at night.
Given the quality of materials, design and workmanship, the centering retention of the modular adapter against recoil and assembly/disassembly operations is guaranteed.
On the other hand, the modular adapter costs €255 compared to €180/190 for the one-piece version, and 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 and 2.5x magnification that attaches via bayonet to the ring part of the Rusan modular adapter and 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.
