How to practice deep-sky? Instruments & Books
From
the naked-eye to the biggest telescope, there are deep-sky objects worth to be
studied
In
this section, I will give you an outlook regarding instruments
and books for practicing Deep Sky. It is subjective and
reflects just my experience, but perhaps it can help you to develop your own
opinion about what you really need.
I have owned different instruments along 25 years. My first instrument
was an old 7x50 binoculars pair that my father gave me one summer. That is how
the astronomical bug bit me, looking through the Milky Way at random. I started
buying as books on astronomy as I could afford. I spent many years in the Asociacion Valenciana
de Astronomia (AVA), which helped me to develop
observing abilities. I recommend to any beginner to join to his/her local
astronomy club, and to assist to star parties and lectures as the best way to
introduce oneself in the deep sky world. I am currently member of the Webb Society (since almost 20 years ago), although I left definitely AVA some years
ago. My interest remains being deep sky.
I started observing seriously with an old 6 cm refractor (60/700 mm) for
a couple of years, then with a 12 cm Newtonian reflector (120/810 mm). Finally
I built a 25
cm F/D 4.8 Newtonian reflector (254/1200 mm),
which has been my main telescope for many years. The telescope was very heavy
although powerful enough to give me access to thousands of DSOs. However, I was
restricted to observe within a small village, surrounded by parasite lights.
Definitely, it was very mediocre observing place for deep sky, by the border of
the dome of light of a medium size city, but the limitations forced me to
develop good observing abilities. I finished being able to reach the limits of
the instrument, but I was eager of really good skies. For that reason, when I
came back home after 4 years abroad for study reasons, I decided to buy a 10" Meade LX200 and change my observing style.
Catadioptric telescopes are the best compromise balancing power and
transportability. I think that it is nonsense to build a fixed telescope in a
place that will be ‑sooner or later‑ ruined by light pollution. A
smaller instrument will show better images if it can be transported to a better
place. Transportability wins. The 10" Schmidt-Cassegrain telescopes are
light enough to be setup easily and neatly more powerful than the popular
8". With good eyepieces, a 10" SCT offers fantastic deep sky images.
So I have got a good set of eyepieces (7, 9 and 13 Naglers T6,
a 22
mm Panoptic, and some other Plossl and Köenig), and I bring the telescope to a good place to observe; never in the
city. I have found that the combination 13 mm Nagler and focal
reducer/flattener (x0.63) is the best one to get astonishing DS images,
extremely crisp and contrasted.
GOTO telescopes
are wonderful tools. They allow finding easily many objects without effort. But
that is the problem: they make you to loose the contact with sky. This contact,
which starts learning the paths among stars (i.e., starhopping) up to locate your
target, is the most unavoidable step in the process of becoming an expert deep
sky observer. Never
gave it up, or skip it. Learn first the
constellations and spend at least a year making starhopping. And from time to
time, switch off the power, and enjoy the sky by yourself. Even without power
supply or star tracking, the LX200 is a comfortable telescope to find what you
want, still in altazimut mode. I have to say that I do it frequently: less
parafernalia, and more sky contact makes you more delighted.
I also like very much observing with large binoculars. Currently, these
are a 25x100
Celestron SkyMaster pair with a parallel
9x50 finder (small picture on the left). Formerly, it was a 20x80 Zeus binos pair. In combination with the LX200, giant binos makes the
starhopping process easier, and in addition, the binoculars provide a second
perspective in the observed object very worthy.
However,
too much parafernalia makes one reluctant to observe. For this reason, I tried to reduce the
equipment. For field work I considered essential a set of two reference books
(picture on the right) and the minimal accessories. The books include
photocopies of the original sources, so moisture and deterioration are not so
problematic. The field atlases are also photocopies stored into plastic folders
(see below).
Anyway,
loading the car makes one always lazy. So except in situations where you are
spending two or more nights, think twice before loading your car with tons of
material that likely you will not use. Less equipment fully enjoyed will let in
you better memories.
Good
sky maps are essential. I have a unique star
atlas, in my opinion the best star atlas, which I prepared myself with the old
release of INDEX. It consists of 12,000 maps (see the pictures). Each of these maps shows a 1º x 1º area
enlarging the surroundings of 12,000 deep sky objects with stars exceeding
12.5 magnitude. It is a terrific combination
with Section C of the Herald‑Bobroff AstroAtlas (HB-C) or Uranometria
2000. Frequently you need to know exactly
where the fuzzy you are chasing lies to perceive it.
Thus,
I usually choose the HB-C (left) to navigate to the place where my target is
located. Then, if necessary, I switch to my map collection (left and below) to boost the detail and to spot the object. The HB-C provides panoramic views, and usually
plots at least a 9 magnitude star near the object, that can be seen in the
corresponding one-degree circle. This is essential: a smaller atlas, such as
Sky Atlas 2000, does not guarantee plotting at least one star close enough to
the object, and makes more difficult the identification. I have tried the
collection for half a year and I can affirm that is the best star atlas I have
tried ever.
For getting truly functional maps, I prepared an index
section listing the objects first by constellation, then by RA, and then by
DEC, that allow locating any object in a few seconds.
Each
A4 page in the collection contains 54 maps gathered in blocks of six maps each
(right picture), and printed at 600 dpi. I stored them in two plastic folders,
able to keep 2 ´ 120 A4 pages (indexes and maps). The main folder contains a
selection of the 6,000 best DSO, and the second, an extension for faint
galaxies, galaxy clusters and objects that did not pass the filtering
conditions. As you can see, any of the 12,000 objects is presented with its
basic data and a field of 1 degree centered on it. Just take the atlas you
prefer and compare the details. I am now working in a program to plot high
resolution maps. Moreover, I am considering in the near future a project of
developing a new printed atlas, more powerful than the Millennium Atlas.
Do
you want this atlas for you? I have prepared a PDF document with the first 5800
maps. It is free, follow this link.
25x100 giant binoculars are far better than conventional 7x50 or 10x50, but even x25 do not
allow exploiting but in a small fraction the capabilities of 10 cm lenses.
These considerations led me to the idea of seeking something similar to a giant
binocular, but with larger magnification. Could a large spotting scope be
useful in deep sky?
Finally, I found something that fits in this idea. It is a large spotting scope, which combines a 2.5 cm zoomed finder (x6-x25) with a 10 cm zoomed
compact refractor (x25-x100). Both objectives can be interchanged by flipping a
mirror. I have mounted it on an excellent Manfrotto 055pro tripod with a
M405 geared head. The light path is folded, so the instrument is surprisingly
compact and light. In order to make this telescope more functional, I coupled a
9x50 finder and a Manfrotto three-axis system on the geared head to make
starhopping faster though keeping accuracy. The picture on the left shows the
appearance of all the components assembled.
Zooming
the image reveals a lot of detail, and objects that are totally faded at less
magnification become visible. It is amazing to see how magnification brings to
visibility objects totally imperceptible at x25. Obviously, the optical quality
is not as good as in a true astronomical refractor, but anyway it is much
better than that of giant binoculars. This is an instrument for deep-sky
objects, not for planets. The coatings are excellent, which is a very good
point. That comfort was the main reason to bet for it. This instrument seems to
have found a gap to fill, especially when the cold and wind are intense. In
adverse situations, I unfold the tripod, fix the spotting scope, deployed two
legs, lean the tripod by the car window (south oriented), and I observe warm
from inside. Better than nothing! Furthermore: I must confess that starhopping
in a summer night with just this instrument, the Herald-Bobroff astroatlas and
the collection of maps to catch hard objects is really delicious, an experience
that reminds my first years in deep sky observing.
My
opinion about spotting scopes in astronomy remains poor: they cannot compete
when compared with true astronomical telescopes. However, for occasional
observing, they offer the advantage of being easier to setup. And this model
falls in a new category, in terms of aperture, magnification and deep sky
possibilities. Anyhow, I am starting to use it. Time will tell.
Recently, I decided to go a step beyond, and I
bought two astronomical achromatic refractors. The first was a Synta 120 mm at F/D 8.3 to be used as secondary telescope. This
telescope is a perfect companion for the Meade LX200, with a very good star
definition. The second is a short tube Synta 150 mm at F/D 5 to be used as a grab-and-go instrument. These
telescopes are discussed in detail here. Currently,
the most comfortable telescope is the 150 mm, which has converted in my favorite
telescope owing its comfort and pleasant images. In a small azimuth mount, it
can be brought to the roof with accessories, books and two foldable chairs in a
single operation, so it is perfect for short observing sessions. The 120 mm
Synta is fantastic for planetary/Moon observation. The residual chromatic
aberration is non objectionable and easy to tame. The spotting scope is now for
bird watching, since the new short tube is much better and powerful.
In
my case, the beginning of the learning process was not the purchase of an
instrument, but books. Since this practice was never stopped, I have finished
gathering a very good collection. I can recommend the most useful:
STAR ATLASES
During many years, the Sky Atlas 2000 combined with Uranometria 2000 (in
both cases, first edition) have been my preferred atlases. If you have not got
a star atlas yet, do not doubt: start with these. Both atlases are the opus
magna of Wil Tirion, the best star cartographer in the world. Do not invest in
atlases plotting fewer stars (6.5 magnitude atlas) except as a second choice,
or for reference (e.g., Norton's, Star Atlas 2000, Bright Star Atlas 2000).
Even if you are starting, they are insufficient for real deep sky work. Bet for
a more powerful atlas from the same beginning.
The
cartography of Sky
Atlas 2000 (sample on the right) is meticulous,
well designed and very readable; it's a pleasure to use it. There are three
editions of Sky Atlas 2000: the so‑called field edition (white stars on a
black background), desk edition (black stars on a white background) and deluxe
edition (also black stars but with color deep sky objects and Milky Way, and a
slightly larger scale), each of them in both laminated and unlaminated
versions. If you are thinking in using the originals in the field, take into
account that the unlaminated field and desk editions (and all laminated
editions) are rather bulky (larger than an A3 page in size), so perhaps the
unlaminated deluxe edition may be more convenient, since the pages are well
protected by plastic covers, spiral bond and the pages are folded. I own the
three unlaminated editions (the desk and field first editions, and the deluxe
second edition), but for field use I have always preferred reduced photocopies
of the desk edition in A4 sheets, since are these are handier and I can put them
together with other atlases, tables and reference sources in a large reference
book (see above). Sky Atlas 2000 is accompanied with a tables book (sold
separately), but I used from the beginning a personal tables collection
prepared with INDEX.
The limiting magnitude of Sky Atlas 2000 is ca. 8.1. This was increased
to 8.5 in the second edition (twice stars), which is excellent for binoculars
and for beginners. But sooner or later you will want catching fainter targets,
and you will need more stars to locate them: You will be forced to complete the
Sky Atlas 2000 with Uranometria 2000. This second atlas
has been also published in two editions. The first edition plots substantially
more stars, but less objects (about 10,000 in the first edition and 30,000 in
the second one). I found this paradoxical: fainter objects need more reference
stars, not less, but they indeed removed stars. The limiting magnitude (ca.
9.5) and number of stars is insufficient to set by sure the position of many
objects. However, the chart arrangement (from east to west) and navigation aids
are far more comfortable in the second edition. Also, the stars are plotted in
a continuous scale and not in steps, getting a more realistic representation of
star patterns (this feature was also implemented in the second edition of Sky
Atlas 2000). In any case, Uranometria 2000 is a very good atlas. Both editions
are also accompanied with the respective deep sky field guides, which are a
collection of tables with the basic data of the plotted objects, but as
mentioned, I prefer my own tables book for field use: it is more compact, more
field-oriented and the number of listed objects is even greater.
And now what I'm currently using as main field atlas: the Herald-Bobroff
AstroAtlas. I like particularly this atlas. It
represents a turning point in celestial cartography, with some innovations:
● The symbols are
far more informative than in any other atlas.
For instance, double stars are plotted with position angle, distance and
secondary star. And special coding indicates the type of galaxy, the
concentration class in globular clusters, the Trumpler class in open clusters,
or the period and variation range in variable stars. Spectral type is shown in
stars with the small white lines within stars.
● It includes a
variable level of detail. There are six series
of maps. The first one (Section A) shows only object distribution. Then, there
are two full atlases, one equivalent to Norton's (Section B, 6.5 magnitude atlas)
and other similar to Uranometria (Section C, 9.5 magnitude atlas). The
remaining sections (D-F) boost the detail of some selected regions.
● The chart
arrangement makes navigation easier. The different
sections are related, full atlases are east‑to‑west arranged and
neighboring maps conveniently labeled.
The
negative points are few. I'd like for instance that all objects were labeled
(especially planetary nebulae), or symbols more readable (lines are too thin).
By the way, the grids are almost invisible, and this is a very negative point.
However, the key point is that only some areas (most in the Milky Way) are
zoomed, not all. Just think in locate a truly faint galaxy in the middle of a
constellation such as Pegasus or Draco. No way.
However,
complemented with the minimaps collection, the B and C
sections may give rise to an almost ideal, hard-to-beat, star atlas. I have
reduced the B and C sections to A4 size, marking the constellations patterns on
the B maps, and I have stored them together with the mini-maps indexes in a 60
plastic-sheets folder. A second folder contains the first 5800 mini-maps
(brighter objects), and I have prepared a third folder with more mini-maps to
include fainter objects and galaxy clusters. So, I start the starhopping
process with the H-B, toggling to the collection in the final steps of
starhopping, when the H-B atlas does not give me the detail level I need. It is
amazing the number of faint objects I can spot helped with the mini‑maps.
Finally, the best amidst the current deep sky atlases: the Millennium Star Atlas. Unfortunately, it is out of print, but it represents the state of the
art in sky cartography, with ca. 1,000,0000 stars.
This
atlas is very expensive and massive: it consists of three heavy volumes with
about 1500 maps up to 11 magnitude, with a very large scale, but comparatively
short in deep sky objects (around 10,000). I daren't use it in the field: it is
too precious to bear the risk of damaging it by moisture or tearing a page by
accident in the darkness. On the other hand, when I finished the 4.2 release of
INDEX I got more functional maps, with more stars and objects, such as this one or the maps shown above. Thus, at
least in my case, the Millennium remains safe at home, as a desktop reference.
I cannot imagine anybody using the Atlas in the field, but some people report
this.
Maps
can be scanned and printed for field usage. The sample map on the left spans
the M31 area. I think that it demonstrates clearly that the level of detail of
Millennium is out of any scale when compared with standard atlases.
Beside
the weight, size and of course, price, the only drawback I have found is the lack
of DSOs for an atlas of this power. 10,000 DSOs are indeed too few: it is a
pity the high number of potentially useful reference stars wasted without
taking advantage of them. The 30,000 DSOs in Uranometria 2000 will be perfect
for this truly massive atlas. Anyhow, it covers nicely all what any deep sky
observer would like to find.
A
second edition, softbound and notably cheaper, is now available from Sky
Publishing Corporation. This edition can contribute to outspread this atlas,
still too restricted.
Only computer‑generated maps can offer something comparable to the
Millennium. I hope to report them in a further updating of the contents of this
page, but by now just compare the picture above taken with the Millennium Star
Atlas with a similar plot generated with CNebulaX.
More stars with far more details, and other services that a printed atlas
cannot offer. It can be installed in a portable PC. If we are in our observing
place, and have access to a PC, computer generated maps can be the definite
answer to deep sky maps.