Happened to be awake at the right time and place and managed to capture this on my tracking setup:
and checking tar1090 to make sure it wasn’t due to some general aviation aircraft with a flakey ADS-B transponder:
370 nmi is really far out and in my neck of the woods 300 is usually the farthest I can get when the atmosphere cooperates (still nowhere near what other people have gotten on these forums, lol).
Sadly, neither tar1090 nor graphs1090 wanted to “certify” this event 
; the range outline didn’t update/expand to the above aircraft’s location nor did it get recorded to the plots:
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As for my best guess as to why this distance didn’t get recorded, I believe the distant aircraft didn’t send enough location packets for readsb qualify it as valid (which makes sense due to some of the sanity checks built-in).
This motivated me to add some DXing monitoring and automatic logging to my little script to supplement the rest of the software I’m running, since I’m likely never going to be able to recreate this perfect situation again (looking at my setup while also having a very, very far range value):
Follow up:
Another one! Very cool.
And the freeze frame data of it:
graphs1090 says otherwise:
I guess I might as well tag the master himself:
@wiedehopf what’s the logic within readsb/tar1090 that determines what counts as the “maximum distance” for an aircraft because apparently I get these discrepancies enough to warrant asking.
For such excursions in a particular direction, 2 even and 2 odd CPR messages are required for the position to be considered “not an error”.
But really it just is what it is, read the source i have to do that myself often enough.
Also note that there is a default range limit in readsb of 360 nmi i believe.
Change that if you want to get tropo.
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Back again in my own thread, but this time with my other site: 470 nautical miles 
3.1 degrees below the horizon, very epic dxing indeed.
@wiedehopf sorry to ping you again but you did mention setting the range limit for readsb; I’m using adsb.im (3.0.5) for this site and didn’t mess with any of the environment variables for range, but I was still able to get this result. However I am using it as a stage 2 setup so I’m guessing this behavior is expected? Just want to make sure.
It’s complicated.
stage2 is multiple instances and the combined one is without range limit while the individual sites do have a range limit set.
that limit only limits display, messages are still forwarded to the combined instance.
Think not on purpose it’s using the default which is 450 nmi for each stage2 site.
While normally on non-stage2 install it uses 300 nmi.
You can always set
READSB_MAX_RANGE=0
In the expert environment variables and it’ll disable all range limits.
