CLAUDE: appropriateCenterDC AUTO level from the reference buffer render

getCenterAverage() is null in the pose flow, so the auto DC level silently
no-op'd (composite virtual sky stayed at -4511). Derive the level from the
reference buffer render itself - perSensorImagesFromTD(gpuQuad, true)[0]
sky-half median - i.e. the exact data being zeroed, right after
setReferenceGPU uploads it. Failure-safe warnings preserved; explicit
curt.dc_center and adoption/persistence semantics unchanged.

Verify: pose run -> console 'AUTO center DC level', composite virtual sky ~0.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/main/java/com/elphel/imagej/cuas/rt/CuasPoseRT.java

@@ -449,9 +449,11 @@ public class CuasPoseRT {
 	 * TD points and costs float32 mantissa bits; LWIR is ADDITIVE: day/night and seasons
 	 * shift the level, they do not scale it - the borrowed center reflects its own
 	 * footage vintage).
-	 * Level: curt.dc_center; 0 = AUTO - median of the top (sky) half of the borrowed
-	 * center average image, then ADOPTED into curt.dc_center (persisted on the next
-	 * configuration save - borrowable later, like the photometric calibration).
+	 * Level: curt.dc_center; 0 = AUTO - median of the top (sky) half of the reference
+	 * buffer render itself (the exact data being zeroed; the borrowed center average
+	 * image is NOT available in the pose flow), then ADOPTED into curt.dc_center
+	 * (persisted on the next configuration save - borrowable later, like the
+	 * photometric calibration).
 	 * Mechanics: the CLT of a UNIFORM image (the DC pattern - identical for every
 	 * converted tile) is obtained through the existing back-propagation convert
 	 * (setImageCenter + no_kernels + use_center_image, the CorrectionFPN recipe), then
@@ -468,27 +470,30 @@ public class CuasPoseRT {
 			final int           debugLevel) {
 		final GpuQuad gpuQuad = center_CLT.getGPUQuad();
 		double level = clt_parameters.curt.dc_center;
-		if (level == 0.0) { // auto: median of the top (sky) half of the borrowed center average
-			final ImagePlus imp_avg = center_CLT.getCenterAverage();
-			if (imp_avg == null) {
-				System.out.println("appropriateCenterDC(): no center average image - reference NOT offset");
+		if (level == 0.0) { // auto: median of the top (sky) half of the reference buffer render
+			// Level from the reference render ITSELF (the exact data being zeroed):
+			// getCenterAverage() is null in the pose flow, which silently no-op'd the
+			// appropriation (composite virtual sky stayed at the raw center level).
+			// The reference CLT was just uploaded by setReferenceGPU. By Claude on 07/05/2026.
+			final float [] apx = com.elphel.imagej.cuas.CuasMotion.perSensorImagesFromTD(gpuQuad, true)[0];
+			if (apx == null) {
+				System.out.println("appropriateCenterDC(): reference render unavailable - reference NOT offset");
 				return;
 			}
-			final float [] apx = (float []) imp_avg.getProcessor().getPixels();
-			final int width = imp_avg.getWidth();
-			final int top_pix = (imp_avg.getHeight() / 2) * width;
+			final int width = gpuQuad.getImageWidth();     // valid after the imclt above
+			final int top_pix = (gpuQuad.getImageHeight() / 2) * width;
 			final float [] samples = new float [top_pix];
 			int n = 0;
 			for (int i = 0; i < top_pix; i++) if (!Float.isNaN(apx[i])) samples[n++] = apx[i];
 			if (n == 0) {
-				System.out.println("appropriateCenterDC(): center average all-NaN in the sky half - reference NOT offset");
+				System.out.println("appropriateCenterDC(): reference render all-NaN in the sky half - reference NOT offset");
 				return;
 			}
 			Arrays.sort(samples, 0, n);
 			level = samples[n/2];
 			clt_parameters.curt.dc_center = level; // adopt: persisted on the next config save
 			System.out.println("appropriateCenterDC(): AUTO center DC level = "+level+
-					" (median of the sky half of the borrowed center average), adopted into curt.dc_center");
+					" (median of the sky half of the reference buffer render), adopted into curt.dc_center");
 		}
 		// the DC pattern: CLT of a uniform image through the back-propagation convert
 		final int [] wh = center_CLT.getGeometryCorrection().getSensorWH();

src/main/java/com/elphel/imagej/tileprocessor/CuasRtParameters.java

@@ -31,7 +31,7 @@ public class CuasRtParameters {
 	public boolean  rend_test =       false; // MINIMAL RT ingest+render test (CuasRender.testRenderSequence, takes precedence over pose test): per scene raw /jp4/ -> conditionSceneToGpu -> virtual-grid render at BORROWED stored pose+ERS rates -> -CUAS-RT-RENDER hyperstack [s00..s15, merged][scenes], comparable to -CUAS-INDIVIDUAL/MERGED-CUAS-DBG. Certify THIS before the pose test. // By Claude on 07/05/2026
 	public double   fz_inter =        10000.0; // RT fat zero, INTER (pose/motion: scene x virtual-center correlation). DECOUPLED from the legacy gpu_fatz*/AUX switches (which stay untouched for non-RT/FOPEN). Value is for a single physical-pair amplitude; FZ ~ amplitude^2 in the GPU normalize - scale down x4..x16 for consolidated-average applications as needed. 10000 = the proven oracle INTER operating point (the lean code erroneously used the INTRA value before). // By Claude on 07/05/2026
 	public double   fz_intra =        2000.0; // RT fat zero, INTRA (ranging/disparity: sensor-pair correlations within one scene). Reserved for the RT ranging path; same decoupling/scaling notes as fz_inter. // By Claude on 07/05/2026
-	public double   dc_center =       0.0; // DC level of the BORROWED center (CLT-RESTORED/average): subtracted from the reference CLT at appropriation so it matches the zero-sky conditioned scenes (MCLT has no clean DC/AC split - a DC constant costs float32 accuracy). 0 = AUTO: compute as the median of the top (sky) half of the borrowed center average, adopt the value here (persisted on config save - borrowable later without our data, like the photometric calibration). Slow targets do not influence this shift. // By Claude on 07/05/2026
+	public double   dc_center =       0.0; // DC level of the BORROWED center (CLT-RESTORED/average): subtracted from the reference CLT at appropriation so it matches the zero-sky conditioned scenes (MCLT has no clean DC/AC split - a DC constant costs float32 accuracy). 0 = AUTO: compute as the median of the top (sky) half of the reference buffer render (the borrowed center as uploaded), adopt the value here (persisted on config save - borrowable later without our data, like the photometric calibration). Slow targets do not influence this shift. // By Claude on 07/05/2026
 	public double   psf_radius =      1.0;   // sensor PSF radius for LoG pre-filter
 	public double   n_sigma =         4.0;   // cutoff LoG kernel array, number of sigmas
 	public int      pyramid =         7;     // temporal pyramid levels