ASTRO: M73 Messier's poorest cluster after M40

M73 is a probable asterism of 4 stars in western Aquarius. It was
discovered by Charles Messier who realized it was just 4 stars. So why
did he include it in his list? Messier gave us the answer when he wrote
of finding M73: "Cluster of three or four small stars, which resembles a
nebula at first glance, containing very little nebulosity; this cluster
is located on the parallel [of declination] of the preceding [M 72]; its
position has been determined from the same star [Nu Aquarii]." So he
found it while logging nearby M72 and thought it possible someone with
an inferior scope might see it as nebulous. while there he added it to
the list.

There has been a lot of debate whether these 4 stars are related or not.
Hipparcos data is a bit too unreliable to solve the issue. Latest
measurements seem to indicate this is an asterism but the issue is still
undecided. You can read about several studies coming to different
conclusions at:
http://messier.seds.org/m/m073.html

I vote for asterism even though one analysis says the odds are 1 in 4
that it is an asterism.

Only about 10 galaxies in the field are listed in NED, all being IR
strong galaxies from the 2MASS survey. The brightest is 2MASX
J20595407-1227455 in the upper left corner at magnitude 16.06. None of
the others even have a magnitude listed.

This was a quick image with half my usual exposure data. It was a
quickie while killing time until the next object on my list came into
position. I'd imaged the double star Arp 40 discovering a nice pair of
galaxies in the field that are rarely imaged. I was hoping something
might turn up in this tiny group's field. Nothing much did but I've
finally, after nearly 60 years of astrophotography finally got an image
of it, short as it is. Due to lack of detail I've posted the image at
1.5" per pixel from my imaging scale of 1" per pixel as it seems to be
all it needs though some prefer full size I'm told so posted that as
well.M73 is a probable asterism of 4 stars in western Aquarius. It was
discovered by Charles Messier who realized it was just 4 stars. So why
did he include it in his list? Messier gave us the answer when he wrote
of finding M73: "Cluster of three or four small stars, which resembles a
nebula at first glance, containing very little nebulosity; this cluster
is located on the parallel [of declination] of the preceding [M 72]; its
position has been determined from the same star [Nu Aquarii]." So he
found it while logging nearby M72 and thought it possible someone with
an inferior scope might see it as nebulous. while there he added it to
the list.

There has been a lot of debate whether these 4 stars are related or not.
Hipparcos data is a bit too unreliable to solve the issue. Latest
measurements seem to indicate this is an asterism but the issue is still
undecided. You can read about several studies coming to different
conclusions at:
http://messier.seds.org/m/m073.html

I vote for asterism even though one analysis says the odds are 1 in 4
that it is an asterism.

Only about 10 galaxies in the field are listed in NED, all being IR
strong galaxies from the 2MASS survey. The brightest is 2MASX
J20595407-1227455 in the upper left corner at magnitude 16.06. None of
the others even have a magnitude listed.

This was a quick image with half my usual exposure data. It was a
quicky while killing time until the next object on my list came into
position. I'd imaged the double star Arp 40 discovering a nice pair of
galaxies in the field that are rarely imaged. I was hoping something
might turn up in this tiny group's field. Nothing much did but I've
finally, after nearly 60 years of astrophotography finally got an image
of it, short as it is.

14" LX200R @ f/10, L=2x10' RGB=1x10', STL-11000XM, Paramount ME

Rick
--
Prefix is correct. Domain is arvig dot net

Rick,

it's a pity that there is no Arp galaxy between these four stars :-)
I still have quite a lot of Messiers missing in my list and this is one of
them. It might be doable with moderate exposure time, so I should image it
at last.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
.com...

M73 is a probable asterism of 4 stars in western Aquarius. It was
discovered by Charles Messier who realized it was just 4 stars. So why
did he include it in his list? Messier gave us the answer when he wrote
of finding M73: "Cluster of three or four small stars, which resembles a
nebula at first glance, containing very little nebulosity; this cluster
is located on the parallel [of declination] of the preceding [M 72]; its
position has been determined from the same star [Nu Aquarii]." So he
found it while logging nearby M72 and thought it possible someone with
an inferior scope might see it as nebulous. while there he added it to
the list.

There has been a lot of debate whether these 4 stars are related or not.
Hipparcos data is a bit too unreliable to solve the issue. Latest
measurements seem to indicate this is an asterism but the issue is still
undecided. You can read about several studies coming to different
conclusions at:
http://messier.seds.org/m/m073.html

I vote for asterism even though one analysis says the odds are 1 in 4
that it is an asterism.

Only about 10 galaxies in the field are listed in NED, all being IR
strong galaxies from the 2MASS survey. The brightest is 2MASX
J20595407-1227455 in the upper left corner at magnitude 16.06. None of
the others even have a magnitude listed.

This was a quick image with half my usual exposure data. It was a
quickie while killing time until the next object on my list came into
position. I'd imaged the double star Arp 40 discovering a nice pair of
galaxies in the field that are rarely imaged. I was hoping something
might turn up in this tiny group's field. Nothing much did but I've
finally, after nearly 60 years of astrophotography finally got an image
of it, short as it is. Due to lack of detail I've posted the image at
1.5" per pixel from my imaging scale of 1" per pixel as it seems to be
all it needs though some prefer full size I'm told so posted that as
well.M73 is a probable asterism of 4 stars in western Aquarius. It was
discovered by Charles Messier who realized it was just 4 stars. So why
did he include it in his list? Messier gave us the answer when he wrote
of finding M73: "Cluster of three or four small stars, which resembles a
nebula at first glance, containing very little nebulosity; this cluster
is located on the parallel [of declination] of the preceding [M 72]; its
position has been determined from the same star [Nu Aquarii]." So he
found it while logging nearby M72 and thought it possible someone with
an inferior scope might see it as nebulous. while there he added it to
the list.

There has been a lot of debate whether these 4 stars are related or not.
Hipparcos data is a bit too unreliable to solve the issue. Latest
measurements seem to indicate this is an asterism but the issue is still
undecided. You can read about several studies coming to different
conclusions at:
http://messier.seds.org/m/m073.html

I vote for asterism even though one analysis says the odds are 1 in 4
that it is an asterism.

Only about 10 galaxies in the field are listed in NED, all being IR
strong galaxies from the 2MASS survey. The brightest is 2MASX
J20595407-1227455 in the upper left corner at magnitude 16.06. None of
the others even have a magnitude listed.

This was a quick image with half my usual exposure data. It was a
quicky while killing time until the next object on my list came into
position. I'd imaged the double star Arp 40 discovering a nice pair of
galaxies in the field that are rarely imaged. I was hoping something
might turn up in this tiny group's field. Nothing much did but I've
finally, after nearly 60 years of astrophotography finally got an image
of it, short as it is.

14" LX200R @ f/10, L=2x10' RGB=1x10', STL-11000XM, Paramount ME

Rick
--
Prefix is correct. Domain is arvig dot net