Data Access
By using the
Simbad Astronomical
Database you can submit queries for objects by name, coordinates, catalog
number, etc. This can be very handy! Because this is an on-line
data service ostensibly they can provide access to literally terra bytes of
data.
The query can be as simple as
show me everything around object Messier 51. Or very complicated
similar to
TheSky's Data Wizard whereby the user can create a filter limiting the
search criteria. There are examples found on the
Simbad page. Regardless of the query made
this page shows how to take the matched criteria and plot, label, and search
for it in TheSky.
This example uses a search by
identifier where the object entered is Messier 51. Just enter M51 in
the search identifier field, search 15 arc minutes AROUND the object M51, then
SUBMIT the query.
Here is the query.
it.
NOTE: Not all 846 objects displayed. Yes there are 846 objects found in a 15 arc minute field around object M51. This is why having access to the
on-line service with terra bytes of data is often useful. If you cannot find an object in TheSky's native databases this is another good way to identify
it.
Next drag the mouse pointer
over the text starting from identifier to the end of the list of objects.
Right Mouse Drag text
When the entire text is
highlighted you can right mouse click in the text then "Copy" the text to
the clipboard. See below.
Right Mouse Click
on the highlighted text
Choose COPY
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 then 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.
Following is the text as Copied to
the Clipboard then Edit | Paste Special with no formatting here.
identifier |otyp| FK5 (2000.0/2000.0) | B&V magnitudes | sp. type | nref
---------------------------------------------------------------------------------
M 51 | Sy2| 13 29 52.37 +47 11 40.8 | 8.8 : | Sc | 1504
[LPS2002] 16 | *| 13 29 52.32 +47 11 40.8 | | | 1
[LPS2002] 6 | *| 13 29 52.31 +47 11 39.2 | | | 1
[LPS2002] 15 | *| 13 29 52.36 +47 11 42.8 | | | 1
.... and so on.
Now all you need to do is
attach the header text below which defines the fields and allows the data to
be compiled! Just as you did before you can mouse drag the text
that follows here and copy it to the clipboard for pasting into the query
text.
>SEARCH 1,26
>ALIAS 1,26
>RAHOURS 34,35
>RAMINUTES 37,38
>RASECONDS 40,44
>DECSIGN 47,47
>DECDEGREES 48,49
>DECMINUTES 51,52
>DECSECONDS 54,57
>MAGNITUDE 71,80
>PARSE "Object Name" 1,26
>PARSE "Object Number" 1,26
>PARSE "MAGNITUDE" 71,80
>PARSE "otyp" 28,31
>PARSE "B&V Magnitudes" 63,80
>PARSE "Spectral Type" 82,93
>PARSE "nref" 94,99
>OBJECT TYPE 55
>IDENTIFIER Simbad M51 <---Add
M51 making it clear when searching Simbad objects!
>CATALOG CLASS=OBJECTS
>LOADMEMORY
>OBJECT TYPE 55
See below showing exactly
how to grab the header text.
Then just add the header to any query made on the
Simbad page. See
below.
>SEARCH 1,26
>ALIAS 1,26
>RAHOURS 34,35
>RAMINUTES 37,38
>RASECONDS 40,44
>DECSIGN 47,47
>DECDEGREES 48,49
>DECMINUTES 51,52
>DECSECONDS 54,57
>MAGNITUDE 71,80
>PARSE "Object Name" 1,26
>PARSE "Object Number" 1,26
>PARSE "MAGNITUDE" 71,80
>PARSE "otyp" 28,31
>PARSE "B&V Magnitudes" 63,80
>PARSE "Spectral Type" 82,93
>PARSE "nref" 94,99
>OBJECT TYPE 55
>IDENTIFIER Simbad Objects
>CATALOG CLASS=OBJECTS
>LOADMEMORY
>OBJECT TYPE 55
M 51
| Sy2| 13 29 52.37 +47 11 40.8 | 8.8 : | Sc | 1504
[LPS2002] 16
| *| 13 29 52.32 +47 11 40.8 | | |
1
[LPS2002] 6
| *| 13 29 52.31 +47 11 39.2 |
| |
1
[LPS2002] 15
| *| 13 29 52.36 +47 11 42.8 |
| |
1
Now since the header text
does all the work all you have to do is COMPILE the data using TheSky's
Database Compiler. Data | Import. See below.
Data | Import
Browse the text file on your drive
Find the text file with both
the data and the header attached and Compile the text into an SDB file.
NOTE: Make sure the number of
objects compiled makes sense. The total objects is 837 as shown. If this does not match the query you have made a mistake!
Edit Find M51
All objects shown as red Reference Points!
Make sure you have the object
type Reference Point set to visible. Use the View | Display Explorer
and type in Reference point. Place a check mark next to Reference
Point as shown.
Turn on Object Type
Reference Point
When the data is compiled the
entries will show under Edit | Find under the Sky Databases (SDBs) entry. In
this case Simbad M51.
NOTE: Use the
options Frame object and/or Object information! These are very handy. When enabled you can sroll through the list and go right to each object.
Frame object
Object Information
Using View | Display Explorer
find the Simbad M51 entry under the Sky Database (SDBs) entry. Expand
the group and pick the fields you want to label here. The example
shows labeling the Object Number.
Choose the fields to
label
Check fields to label on screen
Keep in mind this can be a bit
confusing! See below.
A bit messy!
All objects now labeled
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 larger datasets supplied with TheSky.
Note: If the objects to
be compiled are stars and you compile the data as "star" instead of
object type "reference point"
the use of the
magnitude is crucial. I have seen datasets that don't have magnitudes for
the stars only coordinates. Plotting stars that do not have
magnitudes indicates a magnitude of zero and this is problematic! The stars will plot extremely
large and look completely unrealistic. See below showing this. Better to use
object type "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
None 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 <> 0.00. Because stellar magnitudes can
be - negative values (brighter) you must use NOT EQUAL to ZERO.
Keep in mind this may cause no objects to be found!
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