By Daniel Opdyke

Over the past few weeks I have been working on a small astrophotography software project called NINA Live Stacker. The goal is simple: create a lightweight local web app that can run on a modest Windows mini PC at the telescope, watch a NINA image folder, and show a live-stacked preview in a browser.

NINA already does an excellent job handling capture, sequencing, camera control, filter changes, and mount coordination. I did not want to replace any of that. Instead, I wanted a companion tool that focuses only on the live-viewing side of an imaging session. The app watches the folder where NINA saves FITS files, reads the FITS headers, identifies the current target/session/filter, applies matching calibration frames, aligns incoming exposures, stacks them, and displays the result in a browser.

One of my main goals was to make the viewer accessible from more than just the imaging PC. The preview can be opened on the mini PC itself, another desktop or laptop on the local network, a phone browser, or through VPN when away from home. This makes it easier to check progress without constantly sitting at the telescope computer or remoting into the imaging PC.

The current version includes a setup page for choosing the NINA lights folder, calibration folder, and live output folder. It can build master calibration frames from individual darks, flats, biases, and dark-flats, and it shows basic stack information such as target, filter, frame count, total integration time, calibration status, and alignment progress. The viewer itself is intentionally uncluttered: mostly the live-stacked image, with a small information overlay that can be hidden on mobile.

I tested the app using a Butterfly Nebula dataset captured with a ZWO ASI533MC Pro and a dual narrowband filter. The app successfully grouped the light frames into a session, matched the calibration data, aligned the frames, and produced a live stack that compared well with the stack in Siril. That was an encouraging milestone, because it showed that a simple, lightweight approach can still be useful for monitoring an imaging session.

This is still an early project, not a polished commercial-style application. There are plenty of things I would like to improve, including better rejection of poor frames, better stretch controls, more robust calibration matching, and a smoother installer. But it is already usable enough that I think other NINA users may find it interesting, especially anyone running a small Windows mini PC at the scope.

I built this project because I wanted something automatic but not mysterious. The app should always show what target, session, filter, and calibration frames it thinks it is using. My hope is that it becomes a practical little tool for checking live progress during long imaging sessions, especially from a phone or laptop elsewhere in the house or anywhere in the world.