Wednesday, 28 March 2012

What to do for observing Sirius



 This diagram shows the 50-year-long orbit of Sirius B around Sirius (called Sirius A). The scale is in "arc seconds". One arc second is equal to 1/1800 the diameter of the full moon. Credit: FrancesoA
 What to do for observing Sirius
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Wayne Mitchell (Star Gazer's Deep Space Atlas )

Someone there hopefully a 12 or larger scope? The one I use is a 12 Dobsonian FL=1500 F4.9. So focus is very sensitive. I think a 12 Cassegrain would probably be better because of a longer FL and more play with focus.

Wait until just has just set. Sirius must be the first star visible. DO NOT wait until dark, you will not see Sirius B when dark because glare of parent star too bright (well I haven't been able to). 

At present, Sirius is overhead at this time of year which is important because you look through less atmosphere.

IMPORTANT; there must be some thin cloud, favorably uniformly spread. This acts as a good glare filter for the parent star, but is not enough to dim the light from Sirius B too much. In saying this I wonder if you will have any this cloud there at all?

Then, at least 200X magnification will work. I only use 200X because do not have eyepiece for higher power, but it works.

Advance the scope slightly ahead of the star so that when you view the star the telescope is steady and allow the star to drift through the field of view of your eyepiece. Slight vibration will inhibit your view of Sirius B.
With these conditions, you still need stable air. While looking into the eyepiece, stare slightly into the glare of the parent star. Sirius B may momentarily pop out of the glare and disappear again. It is extremely tiny!
It is still a challenge, but these conditions aid significantly.

Try this for a few minutes, dont give up too quickly.

If you still do not see Sirius B, rotate the base of your telescope by 45 degrees. By doing this, you may be moving Sirius B out of the bright diffraction spike caused by the parent star. If Sirius B is aligned with a diffraction spike you wont see it.
Try again.

Hope this helps

Regards
Wayne

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