RBFocus eXcalibur Flat Panel Review: Automated Flat Frames Made Easy

Introduction

Flat frames are one of those astrophotography chores that never seem to get easier. You wait for the right light, drag equipment outside in the cold, and fiddle with brightness settings until the histogram looks right. The RBFocus eXcalibur aims to remove all of that from your routine. This robotic flat panel mounts directly on your telescope, opens and closes on command, and adjusts its own brightness to capture perfect flat frames automatically.

The eXcalibur is built by RBFocus, a small family company based in Spain. It is not a ZWO product, so it does not work with the ASIAir ecosystem. Instead, it is designed to be controlled from a Windows PC using software like NINA, with an ASCOM driver available from the RBFocus website. If you already run your imaging rig from a laptop, this panel fits naturally into that workflow.

What Is the RBFocus eXcalibur?

The RBFocus eXcalibur is a flip-flap style flat panel. It can open and close itself automatically, either through manual commands or as part of an automated sequence. You can tell it to open the cover, close the cover, or change the brightness of the light, all without touching the telescope.

The panel offers 4,092 steps of brightness adjustment, giving you fine control over the light output. When you open the cover manually, the light turns off automatically, since you do not need illumination when the panel is open. This small touch shows the thought put into the design.

Because the panel is controllable through software, it integrates with tools like NINA and its Flat Wizard. This means you can specify your desired exposure time and target histogram level, and the software will adjust the panel brightness to match. The whole process happens automatically, without you needing to step outside.

Installation and Setup

Installing the eXcalibur on your telescope is straightforward. The panel attaches using adhesive that is designed to be easy to remove later. There is one piece of adhesive holding the flat panel itself, and another holding the robotic arm on top. You can choose the diameter or radius of the flat panel to match your specific telescope.

The panel connects to your computer via USB through the robotic arm. Power is supplied through one of the DC power output ports on a compatible control center, with a small cable running between the robotic arm and the flat panel. Once connected, the panel appears as a simple ASCOM device in your software.

In NINA, the panel shows up in the equipment connection list. You can connect and disconnect it like any other device. The touch interface for NINA provides the same controls as the desktop version, so you can open the cover, close it, and adjust brightness from either interface.

Automated Flat Frames with NINA

The real strength of the eXcalibur becomes clear when you use it with the Flat Wizard in NINA. You can set your target exposure time, say one second, and tell the software to adjust the panel brightness to achieve that exposure while keeping the histogram around 30% of the sensor’s dynamic range.

The wizard then runs through a process of testing different brightness levels. It starts at half the available brightness, then halves it again, checking the histogram each time until it finds the perfect setting. Once it locks in the brightness, it captures the requested number of flat frames automatically.

This automation extends to your imaging sequence as well. You can add an “open flat panel cover” step to your start sequence and a “close flat panel” step to your stop sequence. In the morning, your telescope parks itself, the flat panel closes, and the dust cap is effectively already on. You do not need to do anything.

For anyone who images from a remote setup or simply wants to avoid going outside in the cold, this level of automation is a genuine quality-of-life improvement.

Who Should Consider the RBFocus eXcalibur?

The eXcalibur is not a necessary piece of equipment. You can absolutely capture flat frames without it, using a manual panel or even a t-shirt over the telescope. But the convenience it offers is hard to ignore once you have experienced it.

This panel is best suited for astrophotographers who already control their rig from a Windows PC with software like NINA. If you use an ASIAir or prefer a fully integrated ecosystem, the eXcalibur may not fit your setup. It also requires a compatible control center or power source, so you will need to plan for that.

The price is around €330, which reflects the hand-built nature of a small family company product. It is not cheap, but for those who value automation and efficiency, the cost may be justified.

Buying Advice

Before purchasing the RBFocus eXcalibur, consider your current workflow. If you already use NINA and automate your imaging sequences, this panel will integrate seamlessly and save you time on every imaging session. If you prefer manual control or use different software, check whether the ASCOM driver supports your setup.

The adhesive mounting is easy to install and remove, so you can move the panel between telescopes if needed. The 4,092 brightness steps give you plenty of control for different filters and cameras.

For astrophotographers who want to eliminate one of the most tedious parts of the hobby, the eXcalibur is a compelling option. It is an investment, but one that pays off in convenience and consistency.

Conclusion

The RBFocus eXcalibur robotic flat panel takes the hassle out of flat frame capture. It opens and closes automatically, adjusts its own brightness, and works seamlessly with NINA’s Flat Wizard. While it is not an essential purchase, it is the kind of tool that makes you wonder how you managed without it.

If you are tired of going outside in the cold to set up flat frames, or you simply want a more automated imaging routine, the eXcalibur is worth a serious look.