AJames
03-09-2007, 06:43 PM
:) I read Garyh (Stuart) report of today of his wonderful image in the Deep Sky Section of this IIS Site. Taken with 8-inch f/5, he photographed one of the great barred spiral galaxies of the southern skies, NGC 6744 / Caldwell 101 in Pavo. At 8.3v magnitude, this 20x13 arcmin galaxy lies at a close distance (as galaxies go) of 8.1 Mpc. See his image at;
[ See: http://www.iceinspace.com.au/forum/showthread.php?t=23613 ]
What attention though was the need to identify the surrounding field objects, and the need to quick find out what is what?
I though IIS'ers might like to consider something they might not know about. Finding imaged objects is both quick and easy using the Astronomical Database SIMBAD "Query by criteria".
For those that might be interested, here is how to use it. Simply go to the page; http://simbad.u-strasbg.fr/simbad/sim-fsam
This first shows an entry screen for setting various parameters for identifying field or object classifications for a certain sized field. The language script, or SQL statement, and has to be entered into the "search expression box." Now Garyh does not report the size of his field, but knowing visually this field very well, I estimate it is about 4.0 x 3.0 degrees.
Using this search site, enter the follow expression;
region (circle, NGC 6744, 30)
Which means; circular field, name of object, field in arcmin.
Entering a field of 4 degrees is slight too big as it will reveal more than 3000 objects, including many galaxies, stars and other exotic oddities - to many for our search.
By reducing the field to 30 arcmin reveals some 117 objects, here we will find for example the 9.2V magnitude interacting galaxies of IC 4820 at 19h 09m 13.2s -63d 27' 53". Still the Table is too big.
To find the galaxies only, the statement can be easily changed to;
region (circle,NGC 6744, 40) & otype = 'G'
This produces the small Table with only 14 galaxies, which identifies all the galaxies in the field.
To find the galaxies in our 4 deg field, type; instead of 40, type “4d” Ie. Object query :
region (circle,NGC 6744, 4d) & otype = 'G'
This unveils 368 galaxies within this same 4 degree field, but this is again far too many/, So instead, lets limit the magnitudes of the galaxies say to be greater than or equal to 15th V magnitude.
For this, our typed statement now becomes;
region (circle,NGC 6744, 4d) & otype = 'G' & Vmag <=15
Here the 368 galaxies are now reduced to just 15 galaxies, and all of them should be visible in moderately sized amateur telescopes.
Those who want to try this for different types of objects, can also modify the statements which is explained in the Help file (Bar on top right side) – making sure your in the "Query by criteria" option.
If you want to find stars near the galaxy, say above 13.0V magnitude and within 20 min (say to find a suspected supernova on your image);
Simply type;
region (circle,NGC 6744, 20) & otype = '*' & Vmag <=15
This time you will get a list of 9 stars within this criteria.
If information is required on any of these results, just click on the data for any object in the table, and the full details and references then become available for each object selected.
The actual object or "oType" classification, can be found at;
http://simbad.u-strasbg.fr/simbad/sim-display?data=otypes
Probably the popular ones for us amateurs would be;
** - Double Star or Multiple
V* - Variable Star
GroupG - Group of Galaxies
Cl* - Star Cluster
GlcC - Globular cluster
PN - Planetary Nebula
Finally, if you wish say to find all the planetary nebula with twenty degree of NGC 6744, just write he object script as;
region (circle,NGC 6744, 20d) & otype = 'PN' & Vmag <=15
In very little time seven planetary given in the field radius.
I, for example, clicked on IC 4662 (in blue and underlined) and found an interesting object known as a "BCG" - Blue Compact galaxy n the SIMBAD query result. This was actually mistaken for a planetary nebula by K. G. Henize as He 2-269.
To get an STscI image, you can click the "Aladin previewer" (just below the Identifiers Listing, and under the Heading “Plot and Images”.
You can also do a plot of the surround region by "plot around" option. If you set the size to say about 30 arcmin field, then just replace the 10 with 30 arcmin. This produces a little chart of the field around IC 4662. Click on any object within the chart, and this will lead to another single page of that object you have selected. To obtain a nice useful field chart, press the "get the EPS file for this image" at the bottom of the frame, and a much larger version of the chart can be printed and used at the telescope or to identify magnitude limits on images. This chart, however, is unclickable.
[Note: I am unsure if this works on a PC, but it is no problem on the Mac's OS X 10.4 operating system.]
If not, you can click instead on the Aladin Previewer to obtain the StScI image with the object centered in the frame.
Now I have probably hit you with too much, but as you can see, this resource could be very useful to imagers and deep-sky visual observers. I should issue a slight word of warning, that the data used to do this is heavy on the Internet usage. I think this would be a nightmare on some phone-line connected to the Internet, but a broadband connection will be fine.
I would be interested if any observers here have experiences using this wonderful on-line material, or if you know if it might be useful for purposes. You can do a lot more than this, and with commonsense can make observing more interesting and challenging to put that photon envelope.
I look forward to hear your reactions and comments.
Regards,
Nyx
(Sorry if this is too technical!) :doh::doh:
[ See: http://www.iceinspace.com.au/forum/showthread.php?t=23613 ]
What attention though was the need to identify the surrounding field objects, and the need to quick find out what is what?
I though IIS'ers might like to consider something they might not know about. Finding imaged objects is both quick and easy using the Astronomical Database SIMBAD "Query by criteria".
For those that might be interested, here is how to use it. Simply go to the page; http://simbad.u-strasbg.fr/simbad/sim-fsam
This first shows an entry screen for setting various parameters for identifying field or object classifications for a certain sized field. The language script, or SQL statement, and has to be entered into the "search expression box." Now Garyh does not report the size of his field, but knowing visually this field very well, I estimate it is about 4.0 x 3.0 degrees.
Using this search site, enter the follow expression;
region (circle, NGC 6744, 30)
Which means; circular field, name of object, field in arcmin.
Entering a field of 4 degrees is slight too big as it will reveal more than 3000 objects, including many galaxies, stars and other exotic oddities - to many for our search.
By reducing the field to 30 arcmin reveals some 117 objects, here we will find for example the 9.2V magnitude interacting galaxies of IC 4820 at 19h 09m 13.2s -63d 27' 53". Still the Table is too big.
To find the galaxies only, the statement can be easily changed to;
region (circle,NGC 6744, 40) & otype = 'G'
This produces the small Table with only 14 galaxies, which identifies all the galaxies in the field.
To find the galaxies in our 4 deg field, type; instead of 40, type “4d” Ie. Object query :
region (circle,NGC 6744, 4d) & otype = 'G'
This unveils 368 galaxies within this same 4 degree field, but this is again far too many/, So instead, lets limit the magnitudes of the galaxies say to be greater than or equal to 15th V magnitude.
For this, our typed statement now becomes;
region (circle,NGC 6744, 4d) & otype = 'G' & Vmag <=15
Here the 368 galaxies are now reduced to just 15 galaxies, and all of them should be visible in moderately sized amateur telescopes.
Those who want to try this for different types of objects, can also modify the statements which is explained in the Help file (Bar on top right side) – making sure your in the "Query by criteria" option.
If you want to find stars near the galaxy, say above 13.0V magnitude and within 20 min (say to find a suspected supernova on your image);
Simply type;
region (circle,NGC 6744, 20) & otype = '*' & Vmag <=15
This time you will get a list of 9 stars within this criteria.
If information is required on any of these results, just click on the data for any object in the table, and the full details and references then become available for each object selected.
The actual object or "oType" classification, can be found at;
http://simbad.u-strasbg.fr/simbad/sim-display?data=otypes
Probably the popular ones for us amateurs would be;
** - Double Star or Multiple
V* - Variable Star
GroupG - Group of Galaxies
Cl* - Star Cluster
GlcC - Globular cluster
PN - Planetary Nebula
Finally, if you wish say to find all the planetary nebula with twenty degree of NGC 6744, just write he object script as;
region (circle,NGC 6744, 20d) & otype = 'PN' & Vmag <=15
In very little time seven planetary given in the field radius.
I, for example, clicked on IC 4662 (in blue and underlined) and found an interesting object known as a "BCG" - Blue Compact galaxy n the SIMBAD query result. This was actually mistaken for a planetary nebula by K. G. Henize as He 2-269.
To get an STscI image, you can click the "Aladin previewer" (just below the Identifiers Listing, and under the Heading “Plot and Images”.
You can also do a plot of the surround region by "plot around" option. If you set the size to say about 30 arcmin field, then just replace the 10 with 30 arcmin. This produces a little chart of the field around IC 4662. Click on any object within the chart, and this will lead to another single page of that object you have selected. To obtain a nice useful field chart, press the "get the EPS file for this image" at the bottom of the frame, and a much larger version of the chart can be printed and used at the telescope or to identify magnitude limits on images. This chart, however, is unclickable.
[Note: I am unsure if this works on a PC, but it is no problem on the Mac's OS X 10.4 operating system.]
If not, you can click instead on the Aladin Previewer to obtain the StScI image with the object centered in the frame.
Now I have probably hit you with too much, but as you can see, this resource could be very useful to imagers and deep-sky visual observers. I should issue a slight word of warning, that the data used to do this is heavy on the Internet usage. I think this would be a nightmare on some phone-line connected to the Internet, but a broadband connection will be fine.
I would be interested if any observers here have experiences using this wonderful on-line material, or if you know if it might be useful for purposes. You can do a lot more than this, and with commonsense can make observing more interesting and challenging to put that photon envelope.
I look forward to hear your reactions and comments.
Regards,
Nyx
(Sorry if this is too technical!) :doh::doh: