60 AUSTRALIAN SKY & TELESCOPE April 2019
However, some years ago I read
that several amateur astronomers
had actually accomplished the feat of
tallyingall2,500+Herschelobjects,
includingSky&Telescopecontributing
editorRodMollise.SueFrenchalsolet
me know by email that Larry Mitchell
logged 2,508 Herschel objects. While I
was corresponding with Jim Mullaney
about these achievements, he suggested
thatIcontactdeepskyexpertWolfgang
Steinicke about tackling the remaining
objects in the Herschel catalogues.
Wolfgang shared details with me
on his observations of the so-called
nonexistent objects (largely open
clusters) confirming to me that most of
themdid,infact,exist.Thisleftonlya
handful of objects that have not been
found,someofwhichmayormaynot
have been comets. Once I knew how
many galaxies, clusters, and nebulae
definitely remained in my quest, I was
able to plan my program for the last100+ Herschel objects. My conversations with Wolfgang and
therecoatingofmy40-cmandthe52.5-cmMankascope
encouraged me to go for it.True source or not?
Confusion in transcribing across various catalogues has
ledtosomeobjectsbeinglistedwithwrongNGCnumbers.
Depending on the source, there are 36 to 50 duplicate
observations by Herschel himself of objects that are listed
under two or more Herschel numbers. TheTrifid Nebulaand
NGC 2264together account for six Herschel numbers: Four
numbers are assigned to sections of the Trifid Nebula and
two to NGC 2264, which consists of
the Cone Nebula and the Christmas
Tree Cluster.
One example of an object listed
under the wrong designation is
NGC 5570. I tried to observe it
one night in the spring of 2016
but couldn’t see anything at the
location marked inUranometria
2000.0.Ididseeothergalaxiesnear
that spot, but nothing where NGC
5570 was supposed to be as shown
onthechart.Asitturnsout,NGC
5519, and not NGC 5570, is the true
Herschel Class III object 12.
One of the nonexistent objects
that I was able to eliminate on my
own isNGC 6847in Vulpecula.
IusedtheSTScIpagetoscanthe
area near it and found that the
planetary nebulaNGC 6842fits the
description of Herschel Class II 202.
The only objects that I consider truly
nonexistent are either NGC 420 or
NGC 421 (depending on which of
these two objects is taken to be the
false detection), NGC 3401 and
possibly NGC 5621 (but it may have
been observed by John Herschel).
Some might consider NGC 1908 to
be nonexistent, but I believe that
the field of NGC 1908 does show
a pattern of stars that could be
mistakenforacluster—andIwas
able to find it.
IwantedtomakesurethatI
had covered all possibilities and
so I decided to observe other
deep sky objects in the field of
view of Herschel objects, in case
oneofthemmightbetheobject
that Herschel actually observed.SXFOUR PARTS TO A WHOLEThe Trifid
Nebula (M20, NGC 6514), a star-forming
region in Sagittarius, was initially assigned
threeentriesbyHerschel.Headdedafourth
designation—inadifferentclass—later
(entries highlighted at right).TRIFID NEBULA: TODD BOROSON / NOAO / AURA / NSF; CATALOGUES: PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY OF LONDON (2)CATALOGUE CHALLENGE