diff --git a/Makefile b/Makefile
index de0d914..0d4404c 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,5 @@
-PYTHON=python
-
 SRCS:=$(wildcard logs/*.csv)
-IMGS1:=$(patsubst %.csv, %-avg.webp, $(SRCS))
+IMGS1:=$(patsubst %.csv, %-avg_pwr.webp, $(SRCS))
 IMGS2:=$(patsubst %.csv, %-peak.webp, $(SRCS))
 IMGS:=$(patsubst logs/%, imgs/%, $(IMGS1) $(IMGS2))
 
@@ -11,27 +9,27 @@ all: imgs/ $(IMGS)
 imgs/:
 	mkdir -p $@
 
-imgs/%-avg.webp: logs/%.csv
+imgs/%-avg_pwr.webp: logs/%.csv
 	tmpfile=$$(mktemp /tmp/spec.XXXXX.png) && \
-					$(PYTHON) ./plot_wf.py avg 60 $< $$tmpfile && \
+					./plot_wf_longterm.py -a avg_pwr -r 60 -o $$tmpfile $< && \
 					convert $$tmpfile -quality 100 $@ && \
 					rm $$tmpfile
 
 imgs/%-peak.webp: logs/%.csv
 	tmpfile=$$(mktemp /tmp/spec.XXXXX.png) && \
-					$(PYTHON) ./plot_wf.py peak 60 $< $$tmpfile && \
+					./plot_wf_longterm.py -a peak -r 60 -o $$tmpfile $< && \
 					convert $$tmpfile -quality 100 $@ && \
 					rm $$tmpfile
 
 # high-resolution (in time) images, not generated by default
 
-IMGS_HIGHRES:=$(patsubst %.csv, %-highres.webp, $(SRCS))
+IMGS_HIGHRES:=$(patsubst %.csv, %-avg_pwr-highres.webp, $(SRCS))
 
 .PHONY: highres
 highres: imgs/ $(IMGS_HIGHRES)
 
-imgs/%-highres.webp: logs/%.csv
+imgs/%-avg_pwr-highres.webp: logs/%.csv
 	tmpfile=$$(mktemp /tmp/spec.XXXXX.png) && \
-					$(PYTHON) ./plot_wf.py avg 10 $< $$tmpfile && \
+					./plot_wf_longterm.py -a avg_pwr -r 10 -o $$tmpfile $< && \
 					convert $$tmpfile -quality 100 $@ && \
 					rm $$tmpfile
diff --git a/plot_wf_longterm.py b/plot_wf_longterm.py
index eae97a2..0b5f22d 100755
--- a/plot_wf_longterm.py
+++ b/plot_wf_longterm.py
@@ -37,7 +37,7 @@ for inputfilename in args.input:
             stream = LZMAFile(filename=inputfilename, mode='r')
         else:
             print(f"Loading '{inputfilename}' as uncompressed stream...")
-            stream = open(inputfilename, 'r')
+            stream = open(inputfilename, 'rb')
 
         for line in stream:
             # extract the timestamp