GraXpert on Seestar S50: Fix the Gradient (and When Not To)

GraXpert can fix a gradient in one click. It can also take faint signal with it, and the result can still look cleaner. This first NOVA Handbook episode walks through GraXpert step by step on real Seestar S50 data, then shows how to check what it actually removed, and when the right call is to keep the original. Every panel uses GraXpert's own corrected output and its own saved background model (GraXpert 3.0.2, AI model 1.0.1, Subtraction, smoothing 0.5), so you can reproduce it yourself. NOVA is an autonomous astrophotography engine — it measured every decision in this video itself. Narration is a synthetic voice; the images, code, and decisions are real. If you haven't seen how this project started, watch the Origin episode here:    • I Built an AI Astrophotographer — It Start...   FULL HANDBOOK ENTRY — steps, settings, and decision rules: https://measurethepixels.com/handbook... CODE — full NOVA project, free & open source: https://github.com/measurethepixels/nova WHAT THIS EPISODE COVERS GraXpert 3.0.2 background extraction on Seestar S50 stacks (M81, M45, M27, M1, NGC 7000), in five steps: Load, Model, Correction, Inspect, Measure. Why linear data looks black, and why the preview stretch never changes your pixels AI interpolation, subtraction vs division, and what the smoothing slider really does Inspecting the background model: a smooth model is a good sign, not a guarantee Measuring the result with NOVA's own gradient score: Crab 9.3 → 9.9, M27 8.6 → 9.6 When not to keep it: on the frame-filling North America Nebula, NOVA measured essentially no improvement (9.60 → 9.57) and kept the original CHAPTERS 00:00 Can background extraction lie? 00:23 Step 1: Load (why it's all black) 01:08 Step 2: The AI model 01:19 Step 3: Subtraction vs division, smoothing 02:00 Step 4: Inspect what it removed 02:38 Step 5: Measure the result 03:04 When not to use it: NGC 7000 03:30 Other hosts, versions, what's next 04:07 Wrap-up MY GEAR Affiliate links — I may earn a commission at no additional cost to you. 🔭 Current Seestar S30 Pro: https://amzn.to/46JJQCC The telescope that started the project was my Seestar S50. Full gear list: https://github.com/measurethepixels/n... SOFTWARE NOVA combines open-source tools, custom code, and optional commercial astrophotography software. Free/open-source core: Siril — https://siril.org ASTAP GraXpert Seti Astro tools — https://www.setiastro.com NOVA — https://github.com/measurethepixels/nova Optional commercial tools used by the project include PixInsight and RC-Astro plugins. PROJECT 🌌 Measure the Pixels https://measurethepixels.com 💻 NOVA https://github.com/measurethepixels/nova This episode is part of the NOVA Handbook — one tool or concept, explained with real measurements. The goal isn't AI that simply makes pretty pictures. It's astrophotography by evidence. Measure the pixels. Make the call. #astrophotography #SeestarS50 #GraXpert