Astronomy Specialist


Thanks to the many available adapters, you can easily attach the Prima Luce Lab ESATTO focuser to your refractor for high performance astrophotography. Refractors, especially the apochromatic variety, are perfect instruments for astrophotography since they don't have a very long focal length (you can use them for very long exposures with affordable mounts) and they combine very good performance with easy of use. 

However, many refractors use a focuser that may not be able to adequately support your camera and the accessories used in astrophotography. Let's see how you can improve your refractor telescope by replacing the focuser with the ESATTO!



Some of the problems you may have with standard focuser

Astrophotography, especially of deep-sky objects, requires not only specialized cameras (usually with large sensors and a dedicated cooling system) but also many accessories like large motorized filter wheels. When you have such a large imaging train, the first thing to consider is its weight: most refractors (especially the more affordable ones) are not provided with a high weight load capacity focuser. This is fundamental for perfectly keeping the camera in the exact focus position during long exposures, especially when the telescope is pointed to the zenith.

If your focuser does not have enough weight capacity, your camera and accessories will slip and will bring your sensor out of focus. By using the ESATTO focuser on your refractor, you'll have that high weight capacity, as well as the ability to utilize heavy imaging trains.

Prima Luce Lab ESATTO robotic focuser on SkyWatch Evostar 80ED refractor


If the imaging train weight is higher than the focuser's load capacity, the image train may slip during the imaging session.


How to use the ESATTO focuser on your refractors

The ESATTO is available in different diameters, so you have to choose the one that best fits your telescope based on its specifications. Compact refractors may require the smaller 2" focuser, but larger refractors may need the ESATTO 3" or 4".
The ESATTO is designed to replace your standard focuser, by removing the original focuser from the tube of your refractor and connecting the ESATTO. In order to make this as easy and straightforward as possible, Prima Luce Lab has designed different adapters to suit just about any configuration.


Prima Luce Lab ESATTO robotic focuser on SkyWatch Evostar 80ED refractor


The PL3600230 adapter allows you to easily install the ESATTO on the Skywatcher EVOSTAR 80ED refractor.


Note: if your refractor telescope has a built in corrector (field flattener or reducer), in order to use the ESATTO you must first check if the corrector is inserted in the focuser's draw tube or if it's separated from it. If the corrector is built in to the draw tube, by removing the original focuser you will remove the corrector too and in this case you can't use the ESATTO.
If your corrector is separated from the focuser (for example, like the Borg 90FL f3.9 and 107FL f3.9, the Takahashi FSQ-85/FSQ-106 or one of the many 65mm quadruplets available with different brand names), you can use the ESATTO without a problem.

Prima Luce Lab ESATTO robotic focuser on SkyWatch Evostar 80ED refractor
If the refractor's corrector (at the center in the image above) is separated from the standard focuser (right in the image above) you can use the ESATTO.


Installation example and focus position of your refractor

Refractors usually have very long focuser draw tubes, while the ESATTO is a microfocuser designed for the small and precise movements required in astrophotography. If you remove a focuser with long draw tube and you connect the ESATTO, in order to reach the focus you may need one or more extension tubes to install between the ESATTO and your imaging train.


Prima Luce Lab ESATTO robotic focuser on SkyWatch Evostar 80ED refractor


The focus distance from the camera sensor when using the SkyWatcher Evostar 80ED is 264mm from the telescope tube (when not using a corrector/reducer).


In this scenario we can use the 2" version of the ESATTO and the PL3600230 adapter to connect it directly to the tube. By removing the 3 screws that fix the original focuser to the telescope tube, you can remove the original focuser (please note, sometimes manufacturers use thread lock so you may need to apply force to unscrew the locking screws). Then, install the PL3600230 adapter and connect the ESATTO.


Prima Luce Lab ESATTO robotic focuser on SkyWatch Evostar 80ED refractor


ESATTO 2" installed on the SkyWatcher EVOSTAR 80 ED telescope instead of the standard focuser.


The adapter's optical thickness is designed to make the ESATTO with adapter thickness to be equal to that of the original focuser. This way you will never have problems to reach focus at the focuser draw tube's inner position. However, while the original focuser has 75mm draw tube travel, the ESATTO 2" has 15mm travel. This means that when you focus on stars, your sensor will be at 264mm from the telescope tube. Depending on the different astrophotography accessories that you use, you may need to add one or more extension tubes in order to reach focus position with the ESATTO.


Now your refractor telescope is ready to be used with the ESATTO focuser and you will be able to use heavy cameras and accessories for even the most difficult of deepsky astrophotography targets.


Click here to browse our range of ESATTO focusers and accessories!