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Background
This page explains how to plot and label the
data using the
NASA/IPAC Extragalactic
Database (NED) page in
TheSky. Although
TheSky primarily
uses the
Principal
Galaxy Catalog which contains
nearly 1 million galaxies there may be times when you need to reference the
above page for identifying smaller or obscure galaxies. Using TheSky's
Data | Import feature you can easily
create an SDB file
that allows you to plot the objects, label the objects, slew to the objects, and
so on.
Complete details on
TheSky and databases can be found here. Currently the primary
catalog used by TheSky
for Galaxies is the
Principal
Galaxy Catalog. The catalog has nearly 1 million galaxy entries
and also boasts very good input data as far as positions, magnitudes, and
coordinates. Additional galaxy datasets are also included with
TheSky totaling
500,000 additional objects and were compiled using
TheSky's import
feature.
Here is a page with
complete details on the other datasets supplied with
TheSky.
Let's start with a simple example. Using
the above page NASA/IPAC
Extragalactic Database (NED), search for all objects near the object M51
the Whirlpool Galaxy NGC5194 or also PGC47404 among many other designations.
In the example we are not going to filter out ANY objects just ask for all
objects that are within 20 arc minutes of M51 NGC5194.
NOTE: There is an on-line help
page detailing
How to use the
NED search engine.
The NED page returns the following for our database query.
770 objects within 20 arcminutes of M51 using a NED search!
Query all objects near
M51
Wow 770 Objects! Not all 770 objects shown here
Drag the mouse holding the left mouse button down over the text on the page.
NED sample
This text will then be copied to the clipboard. See below.
Right Mouse Click
on the highlighted text
Choose COPY
Object Name EquJ2000.0 Velocity/Redshift Dist.
No. (* => Essential Note) RA DEC Type km/s z Qual arcmin Refs Notes
1 MESSIER 051a 13h29m52.7s +47d11m43s G 463 0.001544 0.0 967 24
2 MESSIER 051:[TH94] 03 13h29m52.7s +47d11m43s RadioS 458 0.001528 0.0 1 0
3 MESSIER 051:[TH94] 04 13h29m52.8s +47d11m33s RadioS ... ... 0.2 16 0
4 MESSIER 051:[TH94] 02 13h29m52.4s +47d11m52s RadioS ... ... 0.2 1 0
Not all 770 objects shown here!
You can also choose Select All and
"COPY" everything but that will require more work since you will have to DELETE
the text you do not want in the file (i.e. the page headings and search
information).
When the text has been COPIED to
the clipboard you can EDIT | PASTE the text into any text editor. I prefer
WordPad for this but any text editor will work as long as you have the option to
PASTE SPECIAL (as unformatted text). See below.
NOTE: You need to use
the option to Paste Special! The text should NOT be formatted in anyway.
If your text editor does not have the Paste Special option use WORDPAD instead.
Microsoft WordPad
Use "Paste Special"
The point is you do not want the
text to be formatted in order for the header to work. The header text will
not work if you have altered the data in any way. Just one column shift
causes the header to be inaccurate because the fields are not where they should
be.
Here is a subset of the text,770
objects near M51, as copied from the
NED page and pasted
special here. Object Name EquJ2000.0 Velocity/Redshift Dist.
No. (* => Essential Note) RA DEC Type km/s z Qual arcmin Refs Notes
1 MESSIER 051a 13h29m52.7s +47d11m43s G 463 0.001544 0.0 967 24
2 MESSIER 051:[TH94] 03 13h29m52.7s +47d11m43s RadioS 458 0.001528 0.0 1
0
3 MESSIER 051:[TH94] 04 13h29m52.8s +47d11m33s RadioS ... ... 0.2 16 0
4 MESSIER 051:[TH94] 02 13h29m52.4s +47d11m52s RadioS ... ... 0.2 1 0
Now the provided HEADER text I have created will allow you to easily compile the data in TheSky for plotting, searching, labeling, slewing to the objects, etc.
>SEARCH 6,36
>RAHOURS 37,38
>RAMINUTES 40,41
>RASECONDS 43,46
>DECSIGN 49,49
>DECDEGREES 50,51
>DECMINUTES 53,54
>DECSECONDS 56,57
>PARSE "Object Name" 6,36
>PARSE "Object Number" 1,5
>PARSE "Velocity/Redshift km/sec z" 68,82
>PARSE "Qual" 83,88
>PARSE "Dist. arcminutes" 89,94
>PARSE "Refs Notes Phot" 96,111
>PARSE "Posn Vel/z Diam" 114,127
>PARSE "Assoc" 128,133
>OBJECT TYPE 55
>IDENTIFIER NED Data
>CATALOG CLASS=OBJECTS
>LOADMEMORY
>OBJECT TYPE 55
>SEARCH 6,36
>RAHOURS 37,38
>RAMINUTES 40,41
>RASECONDS 43,46
>DECSIGN 49,49
>DECDEGREES 50,51
>DECMINUTES 53,54
>DECSECONDS 56,57
>PARSE "Object Name" 6,36
>PARSE "Object Number" 1,5
>PARSE "Velocity/Redshift km/sec z" 68,82
>PARSE "Qual" 83,88
>PARSE "Dist. arcminutes" 89,94
>PARSE "Refs Notes Phot" 96,111
>PARSE "Posn Vel/z Diam" 114,127
>PARSE "Assoc" 128,133
>OBJECT TYPE 55
>IDENTIFIER NED Data
>CATALOG CLASS=OBJECTS
>LOADMEMORY
>OBJECT TYPE 55
;
; Object Name EquJ2000.0 Velocity/Redshift Dist.
; No. (* => Essential Note) RA DEC Type km/s z Qual arcmin Refs Notes
1 MESSIER 051a 13h29m52.7s +47d11m43s G 463 0.001544 0.0 967 24
2 MESSIER 051:[TH94] 03 13h29m52.7s +47d11m43s RadioS 458 0.001528 0.0 1 0
3 MESSIER 051:[TH94] 04 13h29m52.8s +47d11m33s RadioS ... ... 0.2 16 0
4 MESSIER 051:[TH94] 02 13h29m52.4s +47d11m52s RadioS ... ... 0.2 1 0
Once the newly combined text files have been
saved on your hard disk they will need to be compiled using TheSky's Data |
Import. Use the BROWSE button on the Data | Import dialog to find the
saved text file you have created.
Data | Import
Find your text file here
Note:
The IDENTIFIER for the SDB file to be created is "NED Data".
The Data class is Objects/Points and the Object Type is "Reference Point".
See below.
Compile the text/header
Note total compiled objects at 770
NOTE: Object Type 55 in the header is
type Reference Point. I chose this so the objects are easily identifiable.
See below. By Default the object type reference point is not enabled.
Use the Display Explorer to enable them as shown below.
View | Display Explorer
Enable Reference Point
Better yet. Make a new
object type of your own design for the NED objects. Easy enough.
Using the Display Explorer go down to User-Defined object types | and expand
Type 1. By using the Display Properties you can name your field and also
create a new symbol for the objects. See below.
Holy cow!
That is a lot of stuff!
The
aqua
colored symbols were chosen by me so
they would stand out. The default color for Reference Point is
RED.
Again, it is probably best to use
filters when searching the datasets on the NED page. By being more
specific with your queries you will limit the number of objects to only those of
interest. When the data has been compiled into an SDB you can then search
it as well.
Searching the NED data
Use Edit | Find
Notice the individual entries are listed under
the Sky Databases (SDBs) | NED Data heading. This will take you to the
data quickly and easily.
To label the NED objects on TheSky display use
the option View | Display Explorer | Sky Databases (SDB's) and expand the entry
NED Data as shown. Under the NED Data you will see a list of the fields
available. Check those you want labeled.
The EXTENDED labels must by enabled
to see the objects labeled. Use View | Labels | Extended Labels and make
sure they are enabled here. See below.
Pick the fields to label
Place a check mark next to the field name
Turn on Extended Labels
Place a check mark by Extended Labels
Objects labeled on the display
A bit too busy!
Certainly you can combine as many objects into a
single text file as you like. Just EDIT COPY each match and EDIT PASTE
SPECIAL into a single text file and compile. See below showing 20 degrees
near M81, M51, and M40. Of course these can be ANY size/object searches
you want! Three queries plotted at once
Be creative!
WARNING:
Keep in mind that accessing an SDB file with more than say 100,000 objects can
become a bit slow. The SDB files have not been optimized for fast plotting
like the other native datasets TheSky uses.
Note: If the objects to
be compiled are stars and you compile the data as "star" instead of reference point
the use of the
magnitude is crucial. I have seen datasets that don't have magnitudes. Plotting stars that do not have
magnitudes indicates magnitude zero! The stars will plot extremely
large and look completely unrealistic in this case. Better to use
Reference Point or create your own custom symbol that is magnitude
independent.
To demonstrate. The
Trapezium in the center of M42 the Orion Nebula asking for all objects
within 5 arc minutes of the objects Plotting the data query from the
NASA Extragalactic Data page we get the
following when the object type is "star" before compiling the dataset.
No magnitudes in dataset
= zero!
No magnitude equals Magnitude ZERO
Again, better to use the
Reference Point object instead! Or if you can filter any data to only
return stars that have a magnitude <> 0 that is NOT Equal to Zero.
Because magnitudes can be negative make you don't say only >0 but greater
than or less than zero.
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