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Ninety Minutes With Leo I

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S. R. W.

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Apr 6, 1997, 4:00:00 AM4/6/97

90 Minutes With Leo 1 - An Article By S. Waldee

INTRODUCTION.

In the list of "DEEP SKY CHALLENGE OBJECTS"
printed in each edition of the OBSERVER'S =

HANDBOOK, published by the Royal Astro-
nomical Society of Canada, noted authors
and observers Alan Dyer and Alister Ling =

recommend a minimum aperture of 30 cm =

(11.8 inches) for observing Leo 1, a dwarf =

galaxy and satellite of our Milky Way,
although they encourage users of smaller
instruments to tackle their selected sky
objects: a collection including some of
the most obscure and low-surface-brightness
galaxies, nebulae, and clusters that one
could ever hope to investigate with a
visual telescope.

On p. 1061 of the 2nd volume of his
CELESTIAL HANDBOOK (published back in
1966 before the advent of today's =

popular fashion of observing with =

large-aperture altazimuth scopes), =

Robert Burnham, Jr. writes a perceptive
section on the galaxy Leo I, and its
'little brother' Leo II, never discovered
visually in the heyday of the great
eagle-eyed observers of Barnard's era.

I really can't fault Burnham's warning
that Leo I is "almost impossible to =

observe visually in any telescope owing
to the extremely low surface brightness"
(especially after spending a large part
of two moonless observing sessions with
my eye glued to eyepiece fields of the =

region of Leo I for about an hour
and a half!) The object requires at
least several satisfactory conditions,
and will not be perceptible to any and
every observer who merely trains a =

telescope on the galaxy's coordinates: =

especially if the viewer intends merely =

to "sweep around" the field of brilliant =

Regulus in order to find the galaxy. =

Yet, since in the amateur astronomers'
newsgroup we have had recently at least
"2-1/2" reports of viewing Leo I with
scopes varying from 15 cm to 25 cm in
aperture, Leo I is not a challenge that
any observer should overlook, in order
to stretch the boundaries of viewing
skill. =

OBJECT DIMENSIONS AND CHARACTERISTICS.

This observer first tried in early
February, 1997, and reported an equivocal
and ambiguous sighting. After reading
the comments of Jay Reynolds Freeman
and Akkana Peck, studying the original
Palomar discovery image, thinking about
the effects and performance of telescope =

optics, and preparing a foolproof chart,
the results on a second new Moon night
in April have been distinctly better.

As this writer reported earlier here,
Leo 1 (UGC 5470 or MCG+02-26-027) is located =

near Regulus in the constellation Leo at:
=

10h, 8.5m RA; +12=B0,18' Dec. =

It is a dwarf-class galaxy of large
apparent angular diameter: The Deep-Sky
Field Guide to the Uranometria 2000.0 =

(p. 189) specifies 12x9 arcminutes, while
the Saguaro Astronomy Club Database (used =

for the computer program "The Arizona =

Database") rates it at 10.7 x 8.3',
while it may be measured along its longer
axis for some 28 arcminutes in the =

deepest exposures with huge telescopes,
according to Burnham. =

There is a corresponding discrepancy in
visual magnitude ratings according to
these sources: either 10.2 or 11.3
respectively. Were the galaxy a narrower
edge-on type of smaller angular diameter,
but the same visual magnitude, even a =

Messier in smoky Paris might have
spotted it in a small refractor: yet =

the vague light of Leo I's stars is so
spread out that it is barely above the
background luminosity and sky glow.

On the original Palomar Sky Survey =

discovery plate (available on the
web: see reference section below) with
which by A. G. Wilson first observed
the galaxy in 1950, most of the 20
arcminute angular diameter between the =

brilliant star Regulus and Leo I is
suffused with stray light, which bounced
around the surfaces of the glass plate =

used for the exposure in the fast 48-inch =

Schmidt Camera at the Hale Observatory at
Palomar mountain. That photograph
partially resolves Leo I into a mottled
clump of stellarings of 20th magnitude
and fainter, with numerous RR Lyrae-type
variables (old, bright giants that are
good "distance candles".)

If the surface brightness as reported in
the Uranometria is indeed 15.1 mag/square
arcminute, then Leo I is at least one-
fifth as bright as typical galaxies
often viewed by amateur astronomers
(which are often in the range of 12-13th
mag/sq arcminute.)

Leo 1 is NOT included in the large group
of objects in the constellation discusssed
in Skiff & Luginbuhl's OBSERVING HANDBOOK,
featuring items detectable in various =

apertures from 6 cm to 30 cm. David Eicher
makes no particular recommendations and
gives no description in his book THE
UNIVERSE FROM YOUR BACKYARD, other =

than to describe the object's faintness and
obscurity. It is to be found neither in
Lorenzin's 1000+ nor Sanford's OBSERVING =

THE CONSTELLATIONS. Surely this =

object could be considered a likely
candidate for compulsive-obsessive
observers with a certain masochistic =

streak! =

PREPARATIONS FOR OBSERVING.

Experience has long taught this particular
user of a small amateur telescope (20 cm
or 8") to suspect that the simplest =

representations of faint objects like
Leo I -- as seen on chart 13 of the
Sky Atlas 2000.0 or p. 189 of the
Uranometria -- will be unsatisfactory.
True, if perhaps the bright M-31 were =

situated a mere 20 arcminutes from =

brilliant 1.4 magnitude Alpha Leo =

(Regulus) it would be easy to spot. =

But if one is an ordinary mortal, observing =

with typical equipment, merely =

"trolling" for Leo I near Regulus =

will NOT likely succeed in securing =

it in the eyepiece field.

The writer's first attempt was made more
or less this way (although a narrow-field
printed chart using faint stars from
the Hubble guidestar catalog was available
for corroborating reference.) Leo I was
suspected at the outset, but the detailed
chart soon corrected the misperception.
When the precise star field was located,
the glow of the galaxy was so diffuse
that the author was unwilling to make
an unambiguous claim that it had been
"definitely seen."

For the second observation, more elaborate
preparations were undertaken.

First, the optics of the scope were =

considered. As assumed -- and quickly
confirmed in practice -- it is simply
NOT possible using any mere portable
amateur scope of typical design, to =

position the precise starfield of Leo I =

in the visual field of view of any =

usable ocular, avoiding the direct =

image of Regulus, AND to simultaneously
and totally eliminate that star from =

the actual imaged prime focus field of =

the telescope.

With any of the author's eyepieces
(2.5 to 35 mm) in the instrument and
the scope's position carefully =

adjusted so that the precise star-
field of Leo I was at the edge of
the field, placing Regulus' glow
as far out of view as possible,
the brilliant star was immediately
visible in the prime-focus image
seen through the focuser barrel as
soon as the ocular was withdrawn.

Thus the bright star's glare will =

bounce around inside the telescope =

optics. Less than the best baffling,
the diffraction artifacts from the =

vanes of the diagonal mirror's spider,
reflections off the plating on a =

focuser drawtube, or even light
scatter from dust particles on the
optical surfaces will tend to
degrade the absolute contrast range
available. So will poor coatings
on telescope optics, or inferior
eyepieces, degrade the images.

It is recommended that the observer =

take extra care NOT to view Regulus
in either the telescope optics or
even in the finderscope employed!
This author noted that when his =

eyes were fully dark-adapted (and
2 hours were allowed for Leo I) =

that if the scope were accidentally
swept across the position of
Regulus, he cringed in discomfort!
The brilliant image left a visible
bright "trail" in his vision that
took 2 or 3 seconds to disappear.
Too many of these experiences will
diminish one's ultimate ability to =

detect the faint glow of the
galaxy.

In fact, judging from hindsight, the
author should not have spent his day
outdoors doing the spring window-cleaning!
Even using dark sunglasses, his eyes'
sensitivity would have been somewhat =

diminished, compared to staying indoors
in low light as William Herschel often
did when planning difficult observations.

The finder chart employed by this
writer for the second viewing of Leo
I was far better than the printed
chart made from a planetarium program
(even a sophisticated one that showed
Hubble guide stars down to nearly 15th
magitude.) Instead, an actual picture =

was utilized, prepared to agree with =

the expected eyepiece field of view
and image orientation.

On Saturday, 6 April, after a discussion
with the present writer, Mel Bartels
uploaded to his website (see below) a =

CCD image of Leo I that was prepared =

with a 6-inch f5 Newtonian. After =

downloading the file, this author used =

a graphics editing program to invert =

the image for black stars on white =

background (to minimize the ink needed =

for printing), with 'stretched' contrast
that increased the density of the faint
smudge of Leo I. An image with field =

size of about 1 degree was then output =

on a desk jet printer, and served as
the finder chart, to be viewed with only
the faintest red light illumination. =

The picture, though prepared with =

equipment within the reach of amateurs, =

including everything visible in the =

Hubble guidestar plot, as well as some =

fainter field stars. There was also --
in similarity to the Palomar discovery
plate -- a diffraction spike from =

Regulus that intersected Leo I's image,
plus a diffuse glow that extended over
halfway to Leo I after the contrast was
enhanced. That turned out to be not
dissimilar to what was actually observed
by eye.

CONDITIONS FOR OBSERVING.

Successful observations of the faint
Horsehead dark nebula require special
attention to sky transparency. Now that
the efficient hydrogen-beta eyepiece
filters are available, it is no longer
necessary to seek the absolutely darkest
skies or to use only the biggest scopes. =

But the object should be seen when closest
to the meridian, and when sky transparency
is best. =

Leo I is a barely-visible faint patch =

against a field that may be infused with some
scattered light from Regulus. The Horsehead, =

however, is a dark object seen in relief
against a noticeably brighter nebular glow.
In both cases, the ultimate viewing contrast
is the deciding factor of success, not
merely the amount of light gathered. And
achieving that contrast demands excellent
sky transparency.

Observing in smoky or hazy skies will most
likely nullify the chances to view these =

two faint objects. Attempting to observe
the objects when they are placed at a low =

elevation above the horizon will certainly =

diminish one's likelihood of success. =

Luckily, recent high winds across Northern
California had swept most of the air =

pollution particulates out of the atmosphere =

where this observer views on private property
at an altitude of 3,200 ft. above sea level, =

not far from the Santa Clara valley. There =

is still some noticeable light pollution =

(which is greatly reduced in some directions =

as well as overhead), but on the outset of the =

observations reported here, the naked eye
stellar magnitude limit was little better than
5.5 magnitude (at around 1400 UT, the =

stars 52, 46 and 37 Leo -- at 5.5 and 5.4 -- =

could be held with averted vision, and 42 =

Leo -- 6.1 -- was suspected.)

The sky darkness was no doubt somewhat =

better: the nearsighted author's old,
poor uncoated spectacles reduce the
limit about a half-magnitude compared =

to the experience of other far-sighted
observers. 2-1/2 hours later, with =

Leo I elevated only about 45 degrees above
the horizon, the sky darkness had
dramatically increased: now, SAO 99266
(5.8 mag, near 5.5 mag Leo 51) and
other faint stars stretching between
Regulus and Zosma (68 Delta Leo) became
directly detectable. Yet, this venue =

offers by no means "pristine desert skies", =

so observers near urban areas may take =

heart!

During the two sets of observations of
Leo I reported here, seeing varied =

from an initially somewhat-rough "5"
to a much steadier "7" or better =

after midnight (on the Pickering
scale of 1 to 10, from terrible to
excellent.)

At first, there were several =

diffraction rings visible around =

Algeiba's members, but they were =

broken and turbulent. However,
Mars showed excellent detail at =

magnifications of 425 to 500x: yet
careful scrutiny revealed sudden
bursts of turbulence -- lasting for
fractions of a second -- though the
long-term image sharpness was good.
Later, as usual for this mountain
site, calmness of seeing improved
dramatically in time for a second, =

better sighting of Leo I. =

The author has often noted when
observing the faint central stars of
many planetary nebulae, that somewhat
turbulent seeing will make the star
wink out completely if it is near
the limit. Under gross conditions of
air turbulence, this has been noticed
with the faintest and smallest of
narrow-diameter extended objects, too.
Since it is probably necessary to
verify faint field stars near Leo I,
the author would recommend waiting
for good seeing to aid in achieving
absolute identification of the =

stellar field of this faint galaxy.

The foreground stars located in the =

boundary of the galaxy -- which range
from 14.3 mag to 15.5 mag -- were not
clearly seen with the relatively low =

powers used to view the galaxy: to
achieve the absolute magnitude limit
of the author's 8-inch scope it is
often necessary to boost magnification
to 200-400x. At such high powers,
the background glow is reduced to
near pitch black, and best contrast on
point sources is achieved. But the
surface brightness of a diffuse =

object like Leo I would fade to
utter invisibility at such magnifications,
at the exit pupils obtained in a small-
aperture scope.

Yet the author was surprised that at
the lower powers used to detect Leo I, =

there was no difficulty in seeing =

the prominent field stars of the =

CCD image, down to about 13.7
magnitude. In fact, the visual
field glow from Regulus was almost =

as bad as the Palomar picture, or =

the enhanced-contrast Bartels CCD image. =

In addition, the author's Newtonian
had a nasty spider diffraction spike
that threatened to interfere with
the exact region of Leo I. Much
care and patience had to be exercised
in the exact positioning of the scope
and establishing just the right true =

field of view from the eyepiece, as
well as in obtaining the best possible
image contrast by choosing the correct
exit pupil.

VISUAL VS. PHOTOGRAPHIC SIZE

The Bartels CCD image -- even if =

cranked up to highest possible =

contrast -- depicts Leo I's outer
extent as being no more than =

about half the diameter as shown
in the computer program GUIDE 3.0.
And, correspondingly, this author's
visual impression reduced the
apparent diameter even more. The
best guess from many averted glance =

"vision peeps" (to use Lowell's
phrase) was a detectable diameter
of no more than 3 to 5 arcminutes.

The best analogy the writer could =

offer would be to a defective view =

of NGC-2491, the faint and distant =

globular cluster nicknamed the =

"Intergalactic Wanderer", which =

measures 4.1 arcminutes diameter. =

If the sky suddenly went haywire =

due to clouds or fog and the =

globular faded out to unresolved
near-invisibility...that would be
the impression Leo I gave in the
best averted-vision images obtained
during this session.

EXIT PUPIL AND FIELD OF VIEW.

When the author used low powers
and a large exit pupil, it was =

almost impossible to ignore the
upper-atmospheric airglow as
well as field glare from Regulus.
At 50x, with an exit pupil of
nearly 4 mm, the region near
the two 11.5 magnitude "bright"
stars nearest the galaxy was not
utterly dark. Despite the fact
that the visual diameter of Leo I
would be found to be at least
twice the distance between these
stars, the galaxy's faint glow did =

not immediately "leap" into one's
ken.

A variety of magnifications yielded
no satisfactory confirmation. Finally,
the author employed his standard
"small galaxy" combination of eyepiece
and Barlow which yields about 125x at
an exit pupil of about 1.6 mm. After
trying all kinds of scope maneuvers
and rotations, a best-placement for
the field was determined, so that the
galaxy would be ideally located for
averted glimpsing, but would not be
stuck up against the eyepiece field
stop. At the appropriate magnifi-
cation and positioning, the background =

glow was diminished as much as =

possible, yielding best contrast.

Thus, in the first half of the Leo I
observing session (when the object
was closest to the meridian, but not
at the best sky limiting magnitude) =

the galaxy was finally detected at
the absolute outposts of dimness
that could be perceived! No outer
boundaries could be judged, and
no image could be held for an
indefinite period. It was necessary
either to sweep the eyes continuously
across the field (keeping the region
generally averted) or gently to rock
the telescope. The result was not
much more satisfying than the previous
attempt to view the galaxy in February.

Had this been the author's only experience
with Leo I this session, he would have
suspected that the object was "assuming
facts not in evidence." The eye and
brain can perform remarkable feats of
self-induced tomfoolery. Even a modest
observer who intends no self-deception
can be taken in. So many other oculars
were tried, with fields narrow and wide,
and powers high and low, but with no
better confirmation.

The observer of this report did not have
his own Wratten #12 "minus blue" filter
available for this session; he had merely =

an inappropriate Wratten #15 Deep
Yellow, with slightly less transmission
and a different spectral balance. No
enhancement was expected, and none was
provided. Theoretically, to judge from
the report by Jay Freeman (Sky &
Telescope, March 1997, p. 117) the
Wratten #12 may help increase visibility
of dwarf galaxies with populations of
old red stars.

Initially, a general purpose light-pollution
rejection filter provided no enhancement when
the galaxy was near the zenith, and the
naked eye limit was about 5.5 to 5.8.

Later that night, however, around 0830 UT =

on 4/7/97, as stated earlier, the background
darkened, though the galaxy had slipped =

in elevation to the western horizon. Yet
this time, now that seeing was steadier, =

and about a half-magnitude darkness =

improvement had been gained, the galaxy was =

less ambiguous. Also, the author had =

already spent an hour experimenting with =

the charts, telescope, and oculars, and =

was supremely confident of the field =

stars and positioning. =

Leo I was spotted without much difficulty, =

and in less elapsed time, after 0830 UT. =

Standard averted vision was essential.
Furthermore, some prolonged gazes of
a second or two were attempted before
shifting the eyes. Perhaps this helped
slightly to accumulate faint light;
in addition, now with the broadband LPR =

filter, the galaxy showed up better against
an absolutely black background at 125x
and an exit pupil of 1.6 mm (this is one
of the very few instances the author has
experienced of such a filter having
ANY appreciable help with a galaxy!)

That the observing conditions were now
quite fine was confirmed by sightings
soon made of some other objects:

NGC 5903 in Libra: 11.5 mag, 2' x 1.7';
NGC 5898 (same) : 11.5 mag, 1.7 x 1.7';
both galaxies easily seen at about 85x; =

in fact, a great pleasure and tonic =

to the eyes, after the struggle for Leo I!

NGC 5663: galaxy in Libra, 1.0' by 0.8',
14.5 visual mag, surface brightness 14.1:
just barely detected at over 200x.

Planetary PK342+27.1, known as Merrill
2-1; visual mag. 11.6 (Marling/Uranometria);
7 arcsecond disk (16th mag. central star
of course not seen with 8" scope!): nebular =

disk easy to detect with OIII filter.

NGC 5897: 8.6 Mag globular, 12.6' in
diameter; 13th magnitude brightest =

stars. Despite Eicher's caveat that
"small backyard scopes" cannot =

reveal the stars of this distant =

globular, the object was not only
partially resolved at 85x, but also
numbers of stars were detected across
its face: from 6 to a dozen of the
brightest were held with averted
vision. Were they foreground
field stars or actual cluster members?

Sharpless 2-1: emission and reflection
nebulosity field; traces of irregular
illumination were detected with a
narrowband nebular filter.

CONCLUSIONS.

Since respondents on the Internet
newsgroups have been naturally-selected =

for their disputatiousness, there
will be much room for disagreement, =

although no one else has the present =

author's particular set of eyes! =

So, while the specifics of the
reported observation cannot readily
be challenged, the conclusions =

definitely may be.

The present writer suggests that Leo I
is a remarkable "test case" object
for small to large amateur scopes. The
smaller instruments lack the light
gathering to force enough photons
through the eyepiece to make much
of a shattering impression. However,
the larger scopes may suffer from
intense glow around Regulus, and may
even pick up atmospheric light
scattering from this bright star that
could tend to wash out the contrast.

The author suggests that the condition
most appropriate for viewing Leo I
is to achieve best contrast, not =

merely with scope aperture, but by
the most careful attention to the
observing technique employed, the
sky conditions, and the faithful
documentation of the position of
this elusive object.

Not a casual "star-party" object, Leo I
bears careful preparation and long
scrutiny when observed under less
than "world-class" conditions, or
with small telescopes.

Now, on to Leo II! However, this
incredibly faint dwarf of 17.5 mag/
sq arcminute surface brightness
will certainly elude an 8-inch =

aperture visual telescope, so its
photons must be gathered with a
larger instrument and in a darker
sky than those afforded the =

author.

Sincerely,
STEVE WALDEE
Waldee-Wood Astronomical Software
=

- - - - - - - - =

References:

Finder Chart: =

CCD Image with 6" f5 Newtonian,
by Mel Bartels. Available at his
website, at page of CCD images:

http://www.efn/org/~mbartels/

(The author gratefully acknowledges
the cooperation of Mel Bartels for
providing this remarkable image on his =

website!)

Palomar Discovery Plate:
STSci Digitized Sky Survey at:

http://stdata.stsci.edu/cgi-bin/dss_form

(NOTE: first, request coordinates for
object, as given above in article; then
request download of field width desired
up to 60' in GIF or FITS format.)

Sky Charts: SKY ATLAS 2000.0 by
Tirion; Sky Publishing; =

Uranometria 2000.0, vols.
1, 2; Tirion, Rappaport, Lovi;
Willman-Bell;

THE DEEP-SKY FIELD GUIDE TO =

URANOMETRIA 2000.0, Cragin,
Lucyk, Rappaport; Willman-Bell

BURNHAM'S CELESTIAL HANDBOOK by
Robert Burnham, Jr.; Dover;
Vol. 2, p. 1061.

PROJECT PLUTO: Guide CD-Rom
Planetarium Program, incorporating
Hubble Guide Star Catalog; Project
Pluto, 168 Ridge Road, Bowdoinham,
ME 04008. Charts prepared courtesy
of Charles Chew.

OBSERVER'S NOTEBOOK, Sky & Telescope,
March 1997, p. 117

THE UNIVERSE IN YOUR BACKYARD by
David Eicher, Kalmbach Publishing,
pp. 109-110, 113.

OBSERVER'S HANDBOOK, 199_, Ed. Bishop; =

Royal Astronomical Society of Canada.

SAGUARO DATABASE, Computer Program.
Available in shareware files listed
on Astro-Net at =

http://www.rahul.net/resource/regular/programs/programs.html

- - - - - =

Copyright (c) 1997 Stephen R. Waldee - All Rights
Reserved. Permission is hereby granted to
any non-commercial astronomy club newsletter =

for reprints if all notices are included.

S. R. W.

unread,

Apr 6, 1997, 4:00:00 AM4/6/97

Ninety Minutes With Leo 1 - An Article by
S. Waldee

INTRODUCTION.

In the list of "DEEP SKY CHALLENGE OBJECTS"
printed in each edition of the OBSERVER'S

HANDBOOK, published by the Royal Astro-
nomical Society of Canada, noted authors
and observers Alan Dyer and Alister Ling

recommend a minimum aperture of 30 cm

(11.8 inches) for observing Leo 1, a dwarf

On p. 1061 of the 2nd volume of his
CELESTIAL HANDBOOK (published back in
1966 before the advent of today's

popular fashion of observing with

large-aperture altazimuth scopes),

Robert Burnham, Jr. writes a perceptive
section on the galaxy Leo I, and its
'little brother' Leo II, never discovered
visually in the heyday of the great
eagle-eyed observers of Barnard's era.

I really can't fault Burnham's warning
that Leo I is "almost impossible to

observe visually in any telescope owing
to the extremely low surface brightness"
(especially after spending a large part
of two moonless observing sessions with
my eye glued to eyepiece fields of the

region of Leo I for about an hour
and a half!) The object requires at
least several satisfactory conditions,
and will not be perceptible to any and
every observer who merely trains a

telescope on the galaxy's coordinates:

especially if the viewer intends merely

to "sweep around" the field of brilliant

Regulus in order to find the galaxy.

Yet, since in the amateur astronomers'

newsgroup we have had recently at least
"2-1/2" reports of viewing Leo I with
scopes varying from 15 cm to 25 cm in
aperture, Leo I is not a challenge that
any observer should overlook, in order
to stretch the boundaries of viewing
skill.

OBJECT DIMENSIONS AND CHARACTERISTICS.

optics, and preparing a foolproof chart,
the results on a second new Moon night
in April have been distinctly better.

As this writer reported earlier here,
Leo 1 (UGC 5470 or MCG+02-26-027) is located

near Regulus in the constellation Leo at:

10h, 8.5m RA; +12°,18' Dec.

It is a dwarf-class galaxy of large
apparent angular diameter: The Deep-Sky
Field Guide to the Uranometria 2000.0

(p. 189) specifies 12x9 arcminutes, while
the Saguaro Astronomy Club Database (used

for the computer program "The Arizona

Database") rates it at 10.7 x 8.3',
while it may be measured along its longer
axis for some 28 arcminutes in the

deepest exposures with huge telescopes,
according to Burnham.

There is a corresponding discrepancy in

visual magnitude ratings according to
these sources: either 10.2 or 11.3
respectively. Were the galaxy a narrower
edge-on type of smaller angular diameter,
but the same visual magnitude, even a

Messier in smoky Paris might have
spotted it in a small refractor: yet

the vague light of Leo I's stars is so
spread out that it is barely above the
background luminosity and sky glow.

On the original Palomar Sky Survey

discovery plate (available on the
web: see reference section below) with
which by A. G. Wilson first observed
the galaxy in 1950, most of the 20
arcminute angular diameter between the

brilliant star Regulus and Leo I is
suffused with stray light, which bounced
around the surfaces of the glass plate

used for the exposure in the fast 48-inch

Leo 1 is NOT included in the large group
of objects in the constellation discusssed
in Skiff & Luginbuhl's OBSERVING HANDBOOK,
featuring items detectable in various

apertures from 6 cm to 30 cm. David Eicher
makes no particular recommendations and
gives no description in his book THE
UNIVERSE FROM YOUR BACKYARD, other

than to describe the object's faintness and
obscurity. It is to be found neither in
Lorenzin's 1000+ nor Sanford's OBSERVING

THE CONSTELLATIONS. Surely this

object could be considered a likely
candidate for compulsive-obsessive
observers with a certain masochistic

streak!

PREPARATIONS FOR OBSERVING.

Experience has long taught this particular
user of a small amateur telescope (20 cm
or 8") to suspect that the simplest

representations of faint objects like
Leo I -- as seen on chart 13 of the
Sky Atlas 2000.0 or p. 189 of the
Uranometria -- will be unsatisfactory.
True, if perhaps the bright M-31 were

situated a mere 20 arcminutes from

brilliant 1.4 magnitude Alpha Leo

(Regulus) it would be easy to spot.

But if one is an ordinary mortal, observing
with typical equipment, merely

"trolling" for Leo I near Regulus

will NOT likely succeed in securing

it in the eyepiece field.

For the second observation, more elaborate
preparations were undertaken.

First, the optics of the scope were

considered. As assumed -- and quickly
confirmed in practice -- it is simply
NOT possible using any mere portable
amateur scope of typical design, to

position the precise starfield of Leo I

in the visual field of view of any

usable ocular, avoiding the direct

image of Regulus, AND to simultaneously
and totally eliminate that star from

the actual imaged prime focus field of

the telescope.

With any of the author's eyepieces
(2.5 to 35 mm) in the instrument and
the scope's position carefully

Thus the bright star's glare will

bounce around inside the telescope

optics. Less than the best baffling,
the diffraction artifacts from the

vanes of the diagonal mirror's spider,
reflections off the plating on a

It is recommended that the observer

take extra care NOT to view Regulus
in either the telescope optics or
even in the finderscope employed!
This author noted that when his

eyes were fully dark-adapted (and
2 hours were allowed for Leo I)

detect the faint glow of the
galaxy.

In fact, judging from hindsight, the
author should not have spent his day
outdoors doing the spring window-cleaning!
Even using dark sunglasses, his eyes'
sensitivity would have been somewhat

diminished, compared to staying indoors
in low light as William Herschel often
did when planning difficult observations.

was utilized, prepared to agree with

the expected eyepiece field of view
and image orientation.

On Saturday, 6 April, after a discussion
with the present writer, Mel Bartels
uploaded to his website (see below) a

CCD image of Leo I that was prepared

with a 6-inch f5 Newtonian. After

downloading the file, this author used

a graphics editing program to invert

the image for black stars on white

background (to minimize the ink needed

for printing), with 'stretched' contrast
that increased the density of the faint
smudge of Leo I. An image with field

size of about 1 degree was then output

on a desk jet printer, and served as
the finder chart, to be viewed with only
the faintest red light illumination.

The picture, though prepared with

equipment within the reach of amateurs,

including everything visible in the

Hubble guidestar plot, as well as some

fainter field stars. There was also --
in similarity to the Palomar discovery
plate -- a diffraction spike from

CONDITIONS FOR OBSERVING.

But the object should be seen when closest
to the meridian, and when sky transparency
is best.

Leo I is a barely-visible faint patch

against a field that may be infused with some
scattered light from Regulus. The Horsehead,

Observing in smoky or hazy skies will most
likely nullify the chances to view these

two faint objects. Attempting to observe
the objects when they are placed at a low

elevation above the horizon will certainly

diminish one's likelihood of success.

Luckily, recent high winds across Northern

California had swept most of the air

pollution particulates out of the atmosphere

where this observer views on private property
at an altitude of 3,200 ft. above sea level,

not far from the Santa Clara valley. There

is still some noticeable light pollution

(which is greatly reduced in some directions

as well as overhead), but on the outset of the

observations reported here, the naked eye
stellar magnitude limit was little better than

5.5 magnitude (at around 0600 UT, the

stars 52, 46 and 37 Leo -- at 5.5 and 5.4 --

could be held with averted vision, and 42

Leo -- 6.1 -- was suspected.)

The sky darkness was no doubt somewhat

better: the nearsighted author's old,
poor uncoated spectacles reduce the
limit about a half-magnitude compared

to the experience of other far-sighted
observers. 2-1/2 hours later, with

offers by no means "pristine desert skies",

so observers near urban areas may take

heart!

During the two sets of observations of
Leo I reported here, seeing varied

from an initially somewhat-rough "5"
to a much steadier "7" or better

after midnight (on the Pickering
scale of 1 to 10, from terrible to
excellent.)

At first, there were several

diffraction rings visible around

Algeiba's members, but they were

broken and turbulent. However,
Mars showed excellent detail at

better sighting of Leo I.

The author has often noted when

observing the faint central stars of
many planetary nebulae, that somewhat
turbulent seeing will make the star
wink out completely if it is near
the limit. Under gross conditions of
air turbulence, this has been noticed
with the faintest and smallest of
narrow-diameter extended objects, too.
Since it is probably necessary to
verify faint field stars near Leo I,
the author would recommend waiting
for good seeing to aid in achieving
absolute identification of the

stellar field of this faint galaxy.

The foreground stars located in the

boundary of the galaxy -- which range
from 14.3 mag to 15.5 mag -- were not
clearly seen with the relatively low

object like Leo I would fade to
utter invisibility at such magnifications,
at the exit pupils obtained in a small-
aperture scope.

Yet the author was surprised that at
the lower powers used to detect Leo I,

there was no difficulty in seeing

the prominent field stars of the

CCD image, down to about 13.7
magnitude. In fact, the visual
field glow from Regulus was almost

as bad as the Palomar picture, or

the enhanced-contrast Bartels CCD image.

In addition, the author's Newtonian

had a nasty spider diffraction spike
that threatened to interfere with
the exact region of Leo I. Much
care and patience had to be exercised
in the exact positioning of the scope
and establishing just the right true

field of view from the eyepiece, as
well as in obtaining the best possible
image contrast by choosing the correct
exit pupil.

VISUAL VS. PHOTOGRAPHIC SIZE

The Bartels CCD image -- even if

cranked up to highest possible

contrast -- depicts Leo I's outer
extent as being no more than

"vision peeps" (to use Lowell's
phrase) was a detectable diameter
of no more than 3 to 5 arcminutes.

The best analogy the writer could

offer would be to a defective view

of NGC-2491, the faint and distant

globular cluster nicknamed the
"Intergalactic Wanderer", which
measures 4.1 arcminutes diameter.

If the sky suddenly went haywire

due to clouds or fog and the

globular faded out to unresolved
near-invisibility...that would be
the impression Leo I gave in the
best averted-vision images obtained
during this session.

EXIT PUPIL AND FIELD OF VIEW.

When the author used low powers
and a large exit pupil, it was

not immediately "leap" into one's
ken.

glow was diminished as much as

possible, yielding best contrast.

Thus, in the first half of the Leo I
observing session (when the object
was closest to the meridian, but not
at the best sky limiting magnitude)

Initially, a general purpose light-pollution
rejection filter provided no enhancement when
the galaxy was near the zenith, and the
naked eye limit was about 5.5 to 5.8.

Later that night, however, around 0830 UT

on 4/7/97, as stated earlier, the background
darkened, though the galaxy had slipped

in elevation to the western horizon. Yet
this time, now that seeing was steadier,

and about a half-magnitude darkness

improvement had been gained, the galaxy was

less ambiguous. Also, the author had

already spent an hour experimenting with

the charts, telescope, and oculars, and

was supremely confident of the field

stars and positioning.

Leo I was spotted without much difficulty,

and in less elapsed time, after 0830 UT.

That the observing conditions were now
quite fine was confirmed by sightings
soon made of some other objects:

NGC 5903 in Libra: 11.5 mag, 2' x 1.7';
NGC 5898 (same) : 11.5 mag, 1.7 x 1.7';
both galaxies easily seen at about 85x;

in fact, a great pleasure and tonic

to the eyes, after the struggle for Leo I!

NGC 5663: galaxy in Libra, 1.0' by 0.8',
14.5 visual mag, surface brightness 14.1:
just barely detected at over 200x.

Planetary PK342+27.1, known as Merrill
2-1; visual mag. 11.6 (Marling/Uranometria);
7 arcsecond disk (16th mag. central star
of course not seen with 8" scope!): nebular

disk easy to detect with OIII filter.

NGC 5897: 8.6 Mag globular, 12.6' in
diameter; 13th magnitude brightest

stars. Despite Eicher's caveat that
"small backyard scopes" cannot

reveal the stars of this distant

Sharpless 2-1: emission and reflection
nebulosity field; traces of irregular
illumination were detected with a
narrowband nebular filter.

CONCLUSIONS.

Since respondents on the Internet
newsgroups have been naturally-selected

for their disputatiousness, there
will be much room for disagreement,

although no one else has the present

author's particular set of eyes!

So, while the specifics of the

reported observation cannot readily
be challenged, the conclusions

definitely may be.

The author suggests that the condition
most appropriate for viewing Leo I
is to achieve best contrast, not

merely with scope aperture, but by
the most careful attention to the
observing technique employed, the
sky conditions, and the faithful
documentation of the position of
this elusive object.

Not a casual "star-party" object, Leo I
bears careful preparation and long
scrutiny when observed under less
than "world-class" conditions, or
with small telescopes.

Now, on to Leo II! However, this
incredibly faint dwarf of 17.5 mag/
sq arcminute surface brightness
will certainly elude an 8-inch

aperture visual telescope, so its
photons must be gathered with a
larger instrument and in a darker
sky than those afforded the

author.

Sincerely,
STEVE WALDEE
Waldee-Wood Astronomical Software

- - - - - - - -

References:

Finder Chart:

CCD Image with 6" f5 Newtonian,
by Mel Bartels. Available at his
website, at page of CCD images:

http://www.efn/org/~mbartels/

(The author gratefully acknowledges
the cooperation of Mel Bartels for
providing this remarkable image on his

website!)

Palomar Discovery Plate:
STSci Digitized Sky Survey at:

http://stdata.stsci.edu/cgi-bin/dss_form

(NOTE: first, request coordinates for
object, as given above in article; then
request download of field width desired
up to 60' in GIF or FITS format.)

Sky Charts: SKY ATLAS 2000.0 by
Tirion; Sky Publishing;

Uranometria 2000.0, vols.
1, 2; Tirion, Rappaport, Lovi;
Willman-Bell;

THE DEEP-SKY FIELD GUIDE TO

URANOMETRIA 2000.0, Cragin,
Lucyk, Rappaport; Willman-Bell

BURNHAM'S CELESTIAL HANDBOOK by
Robert Burnham, Jr.; Dover;
Vol. 2, p. 1061.

PROJECT PLUTO: Guide CD-Rom
Planetarium Program, incorporating
Hubble Guide Star Catalog; Project
Pluto, 168 Ridge Road, Bowdoinham,
ME 04008. Charts prepared courtesy
of Charles Chew.

OBSERVER'S NOTEBOOK, Sky & Telescope,
March 1997, p. 117

THE UNIVERSE IN YOUR BACKYARD by
David Eicher, Kalmbach Publishing,
pp. 109-110, 113.

OBSERVER'S HANDBOOK, 199_, Ed. Bishop;

Royal Astronomical Society of Canada.

SAGUARO DATABASE, Computer Program.
Available in shareware files listed
on Astro-Net at

http://www.rahul.net/resource/regular/programs/programs.html

- - - - -

Jay Reynolds Freeman

unread,

Apr 7, 1997, 3:00:00 AM4/7/97

> Ninety Minutes With Leo 1 - An Article by
> S. Waldee

Very thorough, Steve.

Incidentally, some of your recent comments prompted me to think a
bit about why I was having so little glare from Regulus -- just out of
the field -- when looking at Leo I in my 6-inch Intes Maksutov. I
think the answer is basically that I was using a 1.25-inch diameter
eyepiece in a 2-inch to 1.25-inch reducer, in a 2-inch focuser. The
barrel of my 20 mm Erfle cuts like a cookie cutter through the "focal
disc" (your term) of the Intes. The field stop of the eyepiece is
about 24 mm diameter, and at 1500 mm focal length, the 20 arc-minute
distance from Regulus to Leo I is about 11 mm. So if I put the center
of Leo I half way from the center of the field of the Erfle to the
edge -- about 6 mm out from center -- with Regulus outside the field
of view in the same direction, then Regulus is a total of 6 + 11 = 17
mm away from center, or a full mm outside the eyepiece barrel
(actually a little more, when you do the math with more decimal places
than I have shown here).

Furthermore, at f/10, the entire converging beam of light from
Regulus will then miss the side of the barrel -- none of it will get
into the inside of the eyepiece directly. That light will hit the
inner surface of my 2/1.25 bushing -- which is blackened -- and any
residue that reflects diffusely off the black surface will typically
require another reflection or two, likely off blackened surfaces as
well, before it can get into the eyepiece. Thus it is no surprise
that Regulus was no bother for my observations. Even if the
separation from galaxy to star is not exactly 20 arc minutes, I can
always put the galaxy a little closer to the edge of the field.

The only time I have been bothered by bright stars near, but not in,
the field, has been when using 1.25-inch eyepiece in a 1.25-inch
focuser, or a 2-inch in a 2-inch. In those conditions,
grazing-incidence reflections off the inside of the focus tube -- even
if it is blackened -- can cause problems.

> Now, on to Leo II! However, this incredibly faint dwarf of 17.5
> mag/ sq arcminute surface brightness will certainly elude an 8-inch

> aperture visual telescope ...

I have a couple of quite convincing observations of Leo II in my
C-14, including one in which I did not have an exact position, made
a drawing of what I thought I saw, and only later compared it with
the position on a chart and found that I was right on. Maybe I will
be silly enough to try it in the Intes...

Jay Reynolds Freeman -- fre...@netcom.com -- I speak only for myself.

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