[bigjoe (JOSEPH)]

Double star tips

THIS WAS A LIST I COMPILED WITH THE HELP OF STEVE (Tinderboxsky), Matt t,bombardon and some others.

1: SEEING - Must be very good for tough doubles.

2: ALTITUDE - Well above the horizon in
a lot of instances.

3: APERTURE -Depends on separation, magnitudes.Cooled and well collimated scope ,though probably no more than 12" due to the affects of seeing on large obstructed scopes.

4: POWER - The use of it is necessary - Helps darken sky background, and with limiting magnitude ; 200x + may be needed.

5: USE A MASK - Hex , may be necessary.

6: ORIENTATION - Is your diagonal/scope displaying an UPRIGHT , EAST/WEST VIEW? ; If not adjust accordingly ; this is critical so you know what direction the secondary is.

7: PRACTISE:

8: DRIFTING - For a faint secondary.Is it preceding East or following West when your facing North?

9: WARM CLOTHING , and stool if necessary.

10: PATIENCE - and lots of it - It could take many attempts!

11: LESS GLASS - Use of EP with fewer elements 4/5 max to increase contrast and detection, may be of help.

12:AVERTED AND DIRECT VISION - Go back and forth between direct and averted vision, until the companion is held in direct view.

13: ZOOM EP - Use of a good marked zoom EP, to find the optimum power for the seeing and filters if necessary.*

14:HIGHLY ACCURATE FOCUS - TOGETHER WITH A NICE FLAT FIELD, FREE OF CURVATURE - this is a must also , and you may have to re-focus often.

15:VERY STABLE MOUNT - Absolutely no wobbles!*

16:VIEWING AT TWILIGHT - Can reduce the glare of a bright primary EG : Sirius A - and this goes for other bright primary doubles as well!

17:KNOW YOUR FIELD-Know what say 10" arc looks like in your go to eyepieces for example as in Sirius.
Formula for working this is OCULAR FIELD IN MM X 57.3 DIVIDED BY FOCAL LENGTH OF SCOPE IN MM.
EG: EP Has field stop of 3 mm and scope 1719 mm focal length

Then that is simply ( 3 x 57.3 )÷ 1719 = 1/10 degree true field of view or 6 mins arc or 360" -So if a double has a separation of 36" it will be one tenth of the field width so you'll get an idea were the secondary will be!

18: Position angle is taken as I've said from an imaginary line on the celestial sphere due North , increasing North to East in a clockwise direction - East following (will be on the right if you face North) -an example is in Sirius B being roughly around 90 degrees or more position angle theta East at this moment in time, and simply let Sirius b drift into the field of view if you let A go past your left West field stop so its glare is mitigated and its worth a crack every good night now!!

19: HOOD or COWL; this WILL help if streetlights or other bright light sources are a nuisance -- I rarely observe without one in any case.
Hope this helps.
PS: If anyone knows of more tips that have not come to our attention please lets us know!