Know what you caught last night, before you stack a single frame.
Clear nights are rare - every hour counts. Point AstroLoupe at your capture folder, step through the frames with the arrow keys, and see whether focus held, whether the corner stars are round, and whether the tilt you've been chasing is actually there.
Native to Apple Silicon, built for serious deep-sky astrophotographers - works alongside N.I.N.A., ASIAIR, or whatever you already capture with
Every imager knows the ritual: pour the coffee, open the capture folder, and quietly hope that the night went perfectly. AstroLoupe is a fast viewer joined to the measurements that answer the questions you'd otherwise ask by eye.
GPU-rendered with a PixInsight-style auto-stretch, so faint detail is visible the moment a frame opens. Step through the night as fast as you can press the arrow keys.
One-shot-colour frames are demosaiced and colour-balanced on the fly - mono frames stay neutral.
Opens FITS (incl. RGB cubes & 32-bit float), XISF, TIFF/PNG and camera RAW (CR3/NEF/ARW/DNG), reading EXIF metadata from RAW just like a FITS header.
The GPU renders every frame; batch analysis fans out across all CPU cores. Ninety 60-megapixel subs are measured by the whole machine, not one core.
True field of view, orientation and pixel scale, matched against a bundled all-sky star catalogue. Seeded from the header, or fully blind across every core.
Scroll, pinch, click-to-zoom, drag a marquee, or snap to 1:1. Grab-and-drag to pan.
A 3Γ3 grid of magnified crops - centre, edges and corners - to compare star shape across the field at a glance.
Median HFD per region, drawn as a distorted quad that points at the tilt - with a tilt percentage.
Per-region eccentricity as an intuitive axis ratio, with direction and a traffic-light colour - the tell that separates corner coma from tracking error.
A dense field of elongation vectors where colour and length signal quality: tiny green is round and flat, growing red is trouble. Tilt or curvature draws a coherent pattern to the corners.
A gentle heatmap of star size across the whole field, drawn from FWHM - which, unlike HFD, doesn't grow with brightness, so it isolates real focus, curvature and tilt. Average it across a session and sensor tilt appears as a clean gradient you can measure.
Measure every light in the folder and average them for a far more reliable tilt estimate, with a significance figure and a plain High/Medium/Low verdict.
Averages drift-subtracted corner elongation across a session for a stable back-focus verdict: radial means too close, tangential too far.
Every metric in one sortable table, opening with a keeper recommendation: classic FWHM pruning, or SNR contribution modelled on quality-weighted integration. Drag the orange cut line to tune the cut - it shows the predicted stack-SNR cost - then send the discards to the Trash, recoverable if you change your mind.
One button rolls up tilt, back-focus, guiding stability, dither/drizzle, sharpness and focus trend, sky transparency (with cloud-episode detection) and the keeper plan into a single graded report with a plain-language headline - the whole night's verdict before you open a single other tool.
One tap switches every figure - including the per-star labels in the viewer - between HFD in pixels and FWHM in arcseconds, computed from the header's focal length and pixel size.
Plot HFD, FWHM, eccentricity, SNR or star count across the folder: focus drift, a passing cloud or a bad run of guiding at a glance.
Sky background, robust noise and median star SNR for every frame - in the clipping tool and the grading table.
A moon graphic and percentage for each frame's capture time - how much moonlight was in play.
Browse the full, ordered header - keyword, value and comment - with a live filter.
Unstretched per-channel histogram focused on the tails, warning on shadow and highlight clipping - the clipped regions circled on the image.
Filter by object, filter, camera or filename - and the browser shows only lights by default, keeping calibration frames and masters out of the way.
Watches the capture folder and updates as new subs land, asking first before scanning very large folders.
A deep-sky image passes through three pieces of software on its way to being a picture. AstroLoupe gives you a proper look at the subs between capture and stack. Its ultra-fast design and GPU architecture outperforms at this task.
Your rig runs the session and fills a folder with subs while you sleep.
Step through the night, measure what happened, and grade what goes forward. Soft subs stop here - and so do mechanical faults, caught before the next clear night rather than after it.
Calibrate, register and integrate the keepers. Fewer soft subs in, sharper master out.
Stretch, gradients, colour - the part everyone actually sees.
Nothing to migrate and nothing to replace: AstroLoupe reads the folder your capture software writes, and hands the survivors straight to whatever you stack with.
βI was frustrated with slow software. Looking at my subs meant loading them into software built to stack them - a step that took forever and was never quite answering the questions I was asking. I craved a low-latency diagnostic tool like AstroLoupe. If this tool saves you one night of stacking soft frames, or finally settles whether that corner is tilt or curvature, it has done its job.
Clear skies.β
Michael Wells - author of AstroLoupe