I've tried to compile the current master branch of KStars on a Raspberry PI4 running Raspbian buster and I was unable because there is no libstellarsolver-dev version available. Are there any spacial procedure to try the new internal solver on RP4?

Nope Jasem, that is not a bug, that is how stellarsolver solves images so quickly. Note it is not that the sextractor spawns different threads, but that the solver spawns different threads whether it uses the internal solver or the external astrometry solver. That takes advantage of our modern multi-core processors to plate solve using either different scales or different depths simultaneously. You can choose to not use a parallel algorithm to solve using a profile like "Fast Solving" but if you do so, it is basically like using classic astrometry.net and will probably take a long time to solve. Solving in parallel can reduce the time to solve from several minutes to several seconds, but your computer needs to be able to handle it of course.

Ok so that's the way it is supposed to work, but I can check later today and make sure I didn't make some kind of mistake that makes it sextract multiple times. It should really just sextract once, and then solve in parallel.

Hi Rob, still testing. This time M57 with Internal SEP | StellarSolver | 7-MidSizedStars
the log from the console:
log-odds ratio 6.27045 (528.717), 0 match, 0 conflict, 0 distractors, 48 index.
RA,Dec = (39.889,13.9498), pixel scale 2.56679 arcsec/pix.
log-odds ratio 1.05603 (2.87494), 0 match, 0 conflict, 0 distractors, 44 index.
RA,Dec = (258.413,36.6353), pixel scale 10.3865 arcsec/pix.
log-odds ratio 1.2692 (3.55799), 0 match, 0 conflict, 0 distractors, 30 index.
RA,Dec = (23.1084,11.2561), pixel scale 8.57688 arcsec/pix.
log-odds ratio 1.96608 (7.1426), 0 match, 0 conflict, 0 distractors, 41 index.
RA,Dec = (12.684,38.5105), pixel scale 4.94093 arcsec/pix.
log-odds ratio 0.176617 (1.19317), 0 match, 0 conflict, 0 distractors, 41 index.
RA,Dec = (294.565,28.0511), pixel scale 3.43981 arcsec/pix.
log-odds ratio 5.18655 (178.851), 0 match, 0 conflict, 0 distractors, 39 index.
RA,Dec = (2.65817,66.7499), pixel scale 3.38983 arcsec/pix.
log-odds ratio 6.42666 (618.109), 0 match, 0 conflict, 0 distractors, 42 index.
RA,Dec = (39.889,13.9498), pixel scale 2.56679 arcsec/pix.
log-odds ratio 6.27045 (528.717), 0 match, 0 conflict, 0 distractors, 48 index.
RA,Dec = (39.889,13.9498), pixel scale 2.56679 arcsec/pix.
log-odds ratio 1.05603 (2.87494), 0 match, 0 conflict, 0 distractors, 44 index.
RA,Dec = (258.413,36.6353), pixel scale 10.3865 arcsec/pix.
log-odds ratio 1.2692 (3.55799), 0 match, 0 conflict, 0 distractors, 30 index.
RA,Dec = (23.1084,11.2561), pixel scale 8.57688 arcsec/pix.
log-odds ratio 1.96608 (7.1426), 0 match, 0 conflict, 0 distractors, 41 index.
RA,Dec = (12.684,38.5105), pixel scale 4.94093 arcsec/pix.
log-odds ratio 0.176617 (1.19317), 0 match, 0 conflict, 0 distractors, 41 index.
RA,Dec = (294.565,28.0511), pixel scale 3.43981 arcsec/pix.
log-odds ratio 5.18655 (178.851), 0 match, 0 conflict, 0 distractors, 39 index.
RA,Dec = (2.65817,66.7499), pixel scale 3.38983 arcsec/pix.
log-odds ratio 6.42666 (618.109), 0 match, 0 conflict, 0 distractors, 42 index.
RA,Dec = (39.889,13.9498), pixel scale 2.56679 arcsec/pix.
log-odds ratio 1.66006 (5.2596), 0 match, 0 conflict, 0 distractors, 31 index.
RA,Dec = (232.93,1.17752), pixel scale 0.0925072 arcsec/pix.
log-odds ratio 2.05037 (7.77074), 0 match, 0 conflict, 0 distractors, 35 index.
RA,Dec = (251.416,-28.3884), pixel scale 0.0721848 arcsec/pix.
log-odds ratio 131.397 (1.16159e+57), 14 match, 0 conflict, 21 distractors, 19 index.
RA,Dec = (283.396,33.0297), pixel scale 0.634585 arcsec/pix.
Hit/miss: Hit/miss: ++++++++-+-+-+-+

---

+

---

+(best)

---

Signal: SIGSEGV (Segmentation fault)

the stack:
Ekos::RemoteAstrometryParser::setEnabled remoteastrometryparser.cpp:149
Ekos::Align::solverFinished align.cpp:3420
Ekos::Align::solverComplete align.cpp:3395
QtPrivate::FunctorCall<QtPrivate::IndexesList<>, QtPrivate::List<>, void, void (Ekos::Align::*)()>::call(void (Ekos::Align::*)(), Ekos::Align*, void**) qobjectdefs_impl.h:152
QtPrivate::FunctionPointer<void (Ekos::Align::*)()>::call<QtPrivate::List<>, void>(void (Ekos::Align::*)(), Ekos::Align*, void**) qobjectdefs_impl.h:185
QtPrivate::QSlotObject<void (Ekos::Align::*)(), QtPrivate::List<>, void>::impl(int, QtPrivate::QSlotObjectBase*, QObject*, void**, bool*) qobjectdefs_impl.h:418
QtPrivate::QSlotObjectBase::call 0x00007f16220d75ae
doActivate<false> 0x00007f16220d75ae
QMetaObject::activate 0x00007f16220d0977
StellarSolver::ready moc_stellarsolver.cpp:364
StellarSolver::processFinished stellarsolver.cpp:352
QObject::event 0x00007f16220ce129
QApplicationPrivate::notify_helper 0x00007f1622c76cc3
QApplication::notify 0x00007f1622c7fc70
QCoreApplication::notifyInternal2 0x00007f16220a06aa
QCoreApplicationPrivate::sendPostedEvents 0x00007f16220a2fa1
postEventSourceDispatch 0x00007f16220fb837
g_main_context_dispatch 0x00007f16206c1fbd
<unknown> 0x00007f16206c2240
g_main_context_iteration 0x00007f16206c22e3
QEventDispatcherGlib::processEvents 0x00007f16220fae92
QEventLoop::exec 0x00007f162209f1bb
QCoreApplication::exec 0x00007f16220a7354
main main.cpp:348
__libc_start_main 0x00007f1620d080b3
_start 0x000055ad671954ee

Do you have an idea where I should place a breakpoint?

This one is my fault, git pull and run again.

CLion opened a tab named kstars(disassembly)
and highlghited the assembler code

cmp $0xfffffffffffff000,%rax

which is part of

__GI___poll:
endbr64
mov %fs:0x18,%eax
test %eax,%eax
jne 0x7f1620df6ad0 ; <__GI___poll+32>
mov $0x7,%eax
syscall
cmp $0xfffffffffffff000,%rax
ja 0x7f1620df6b20 ; <__GI___poll+112>
retq
sub $0x28,%rsp
mov %edx,0x1c(%rsp)
mov %rsi,0x10(%rsp)
mov %rdi,0x8(%rsp)
callq 0x7f1620d78760 ; <__libc_enable_asynccancel>
mov 0x1c(%rsp),%edx
mov 0x10(%rsp),%rsi
mov %eax,%r8d
mov 0x8(%rsp),%rdi
mov $0x7,%eax
syscall
cmp $0xfffffffffffff000,%rax
ja 0x7f1620df6b32 ; <__GI___poll+130>
mov %r8d,%edi
mov %eax,0x8(%rsp)
callq 0x7f1620d787c0 ; <__libc_disable_asynccancel>
mov 0x8(%rsp),%eax
add $0x28,%rsp
retq
nopl 0x0(%rax)
mov 0xd5349(%rip),%rdx ; 0x7f1620ecbe70
neg %eax
mov %eax,%fs:(%rdx)
mov $0xffffffff,%eax
retq
mov 0xd5337(%rip),%rdx ; 0x7f1620ecbe70
neg %eax
mov %eax,%fs:(%rdx)
mov $0xffffffff,%eax
jmp 0x7f1620df6b07 ; <__GI___poll+87>

The crash happened between <__libc_enable_asycnccancel> and <__libc_disable_asycnccancel> when the solver was succesfull (?)
Have a look at the console output:
log-odds ratio 131.397 (1.16159e+57), 14 match, 0 conflict, 21 distractors, 19 index.
RA,Dec = (283.396,33.0297), pixel scale 0.634585 arcsec/pix.
Hit/miss: Hit/miss: ++++++++-+-+-+-+

Jasem, promised!

M57 was solved in seconds (Internal SEP | StellarSolver | 7-MidSizedStars), great!

Will try the Iris Nebula.

It took just 20 seconds and the Iris Nebula was solved.
Good work!

Now I have to take a look at your changes:
kstars/ekos/align/align.cpp | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

The Stellar Solver works with Internal SEP | StellarSolver | 7-MidSizedStars.
I have 1250mm focal length and a small scope.

M65 (Leo Triplet) - no problem.

I tried again tonight with the Canon camera and RedCat and solving, if (and that’s a BIG if) the camera is well focused, succeeds in less than a second. Nice!!! Thanks again Rob!!!

Have you tried to use the solver to load an image and then slew to it? It still makes Kstars crash in 80% of the cases for me. It does not seem to matter which solver options I am selecting.