1. HOW TO SELECT DOUBLE STARS FOR OBSERVATION
GENERAL CONSIDERATIONS
UNDERSTSNDING WDS DATA
USING THE SKY X ON BARC0 TO CONFIRM YOUR PLAN
OTHER PLANETARIUM SOFTWARE – YOUR CHOICE

2. OVERVIEW OF HOW TO SELECT YOUR STARS
WHAT SET OF STARS CAN YOU SEE?
TIME AND LOCATION FACTORS TO CONSIDER:
YOUR SEASON – WHAT PART OF THE SKY YOU CAN SEE
LOCATION - NORTHERN OR SOUTHERN HEMISPHERE
OBSERVATORY HORIZON – SKY VIEW LIMITS
TIME OF NIGHT – BEST AT MERIDIAN
OTHER TIMING FACTORS: MOON, WEATHER
EQUIPMENT FACTORS:
TELESCOPE APERTURE – BIGGER SEES FAINTER
CAMERA AND FILTER – SENSITIVITY AND STAR CLASS (COLOR)
RESOLUTION PER PIXEL – HOW MUCH SEPARATION NEEDED
WITHIN YOUR AVAILABLE SET OF STARS, CONSIDER
CANDIDATE STARS:
MAGNITUDES – BRIGHT ENOUGH FOR YOUR EQUIPMENT (<12)
RELATIVE STAR MAGNITUDES (< 6 DIFFERENCE)
NUMBER OF STARS IN THE SYSTEM – BEWARE OF TOO MANY
ALL KINDS OF INTERESTING FACTORS - GET WDS HISTORY
CHOOSE AT LEAST TWO TARGETS IN CASE ONE PROVES DIFFICULT
RA and DEC refresher
Season for your RA
North or South for your DEC

3. How to select stars for observation
General guidelines to follow:
Select stars that are at a minimum of 6 arc seconds apart.
We have been successful in separating stars as close as 5.5 arc seconds.
Ensure the magnitude differential is no more than 6 magnitudes
The closer the stars in terms of separation, the lower the differential magnitude should be in your selection
With the usage of filters, you can explore greater differential magnitudes
With bright stars, ensure request observations with Red and/or Hydrogen Alpha (Ha) filters in order to filter out some light and prevent over saturation of the CCD chip causing a loss of visible stars near your primary star.
Select stars with in the following Right Ascension
Summer Classes: 18 through 02 RA
Fall Classes: 00 through 08 RA
Spring Classes: 12 through 18 RA
Use the BARC “Telescope Details Side by Side” spreadsheet (located on the desktop of BARC) to pick your telescope of choice
For close stars (ex. WDS separation of 20 arc seconds or lower, ensure you select a telescope that has a “Resolution” less than 1.00 arc sec/pixel
For stars with Declinations below -25 degrees, focus on the Australia telescopes
For stars with Declinations above +25 degrees, focus on Spain and New Mexico.
With stars between the Declinations of +25 and -25, consider using both North and South hemisphere stars

4. How to select stars for observation
Using the WDS to locate stars:
The example below is using a section of the WDS catalog to walk you through considerations for star selection.
In the image below, a selection has been made (highlighted in blue) for illustration purposes
Note the star’s WDS identifier is
From this, we know the RA is 16 and the Declination of -63 places this in the southern hemisphere and best suited for the Australia telescopes.

5. How to select stars for observation
Using the WDS to locate stars:
Next, we need to note whom the discoverer was. In this case, it is RS 403. This will be important in a minute. Make note of it.

6. How to select stars for observation
Using the WDS to locate stars:
Next, determine if the separation is satisfactory for iTelescope.
In this example, the separation is last reported as 10.5 arc seconds.
To determine whether this will be ok with CCD imagery, look at the differential magnitude
The magnitudes for these stars are reported at 8.74 for the Primary, and 13.0 for the secondary. We can image this, but it is advised to use Ha and/or Red filters in your request.

7. How to select stars for observation
Using the WDS to locate stars:
Finally, note the Precise Coordinates.
Write these down. You will need them when ordering your CCD images.

8. How to select stars for observation
Determining where your star is in the sky:
Log into BARC
Once logged into BARC, double click on “The Sky X” icon to open the program

9. How to select stars for observation
Determining where your star is in the sky:
When you open “The Sky X”, the image on the screen will vary in terms of what you see of the sky.
You will need to set the correct location for the observatory that you are going to use.
Under the “Input” menu, select “Location”

10. How to select stars for observation
Determining where your star is in the sky:
Select the tab “List of Locations”
Under “My Custom Locations”, select the site for the telescope that you want to use.
Once highlighted, select the push button “Set As My Location”

11. How to select stars for observation
Determining where your star is in the sky:
Once the location is set, we need to find your candidate star.
Locate the “Search For” window.
Type in the following: WDS (your discoverer code). In this example: WDS RSS 403
Press “FIND”

12. How to select stars for observation
Determining where your star is in the sky:
The “Search For” window will highlight that you searched for WDS RSS 403.
Press second button and your image in the screen will change.

13. How to select stars for observation
Determining where your star is in the sky:
Click on the star
You should see it identified. NOTE: If a different number/name appears, this is normal. There are many “names” for stars. Click around it a little and the WDS identifier will appear.
When it appears, scroll out (mouse scroll wheel is best) to identify where on the sky it is located.

14. How to select stars for observation
Determining where your star is in the sky:
In this case, the star is very close to the South Celestial Pole.
Next, we need to select a time of day that this is visible.
The window highlighted in red will need to be modified slightly.
Select the dropdown menu so it reads “1 Hour”. We are going to use this to “step” time forward and backwards

15. How to select stars for observation
Determining where your star is in the sky:
Next, find the data line labeled “Altitude” in the Object Information Report window.
This needs to be at or above +40.
If it is not, use the “step” time, discussed in previous slide, to adjust the hour of the day until the “Altitude” window reads +40 or higher

16. How to select stars for observation
Determining where your star is in the sky:
In this example, the time of 10:47pm has the star at an altitude of +41
However, let’s say the star, at 10:47pm was at an altitude +20. Click on the “step” function to advance the star until it shows +40 at a minimum. THEN, note the time of day. This will be when your imaging needs to occur.