Alcor is a double star

[ajtribick]

Two independent studies detected an M-dwarf orbiting Alcor:

Mamajek et al.: Discovery of a Faint Companion to Alcor Using MMT/AO 5 µm Imaging
Zimmerman et al.: Parallactic Motion for Companion Discovery: An M-Dwarf Orbiting Alcor

The first study gives evidence that the Alcor binary is likely to be gravitationally bound to the Mizar quadruple.

Article on ScienceDaily

[t00fri]

Two independent studies detected an M-dwarf orbiting Alcor:

Mamajek et al.: Discovery of a Faint Companion to Alcor Using MMT/AO 5 µm Imaging
Zimmerman et al.: Parallactic Motion for Companion Discovery: An M-Dwarf Orbiting Alcor

The first study gives evidence that the Alcor binary is likely to be gravitationally bound to the Mizar quadruple.

Article on ScienceDaily

Neat!





That's precisely the same way I managed to see Sirius B for the first time through my 8 inch telescope as an adolescent... Except that I used a hexagonal objective mask in addition that could be rotated to deviate the glare streaks from Sirius A.


Fridger

[Hungry4info]

I've got a 14 cm reflector, t00fri, you think I could perhaps see Sirius B? D:
(I'm guessing probably not, but it's worth a shot at asking)

[t00fri]

I've got a 14 cm reflector, t00fri, you think I could perhaps see Sirius B? D:
(I'm guessing probably not, but it's worth a shot at asking)

Well

I am sure you know that Sirius A = -1.47 mag while Sirius B = 8.4 mag, i.e A is almost 10 000 times brighter than B!! On the other hand, in 2009 the A-B distance (~8.6") is much wider than when I observed B a long time ago!

That's good. Apparently the issue is entirely about fighting the glare from A. The distance of 8.6" poses NO resolution problem at all for a 14cm reflector. Also 8.4 mag is no problem for a 14 cm scope. BUT the background sky will be BRIGHT at 8.6" distance due to the glare of A. Hence the background of B needs to be made darker with appropriate tricks and a high-contrast scope is required..

So ONLY if you got an EXCELLENT 14 cm telescope, it's worth a try: both your mirror must be very good and the tube interior should be properly baffled. Cheap supermarket scopes will certainly be inappropriate!

With a reflector you got to watch out the (3-4) spike locations around A from your secondary mirror vanes.
Most importantly, you need to fabricate a rotatable hexagonal cardboard mask for your entrance aperture. According to the laws of diffraction, it has the effect of turning the round star disk of A into a "hexagonal star" shape with 6 radiation spikes. The trick is that in-between two neighboring spikes of A, its glare is strongly reduced. Therefore you must rotate the mask such that B is located just in such a radiation valley between two spikes... It's as "simple" as that

At the time, I additionally built a device to hide A in the eyepiece field like in the Alcor B discovering photo above. But this is said not to be absolutely necessary in case of Sirius B

Good luck,
Fridger

[Hungry4info]

Thanks. Unfortunately, my telescope is actually a "cheap supermarket telescope". Do you think I could just fashion a device to block out Sirius A as you describe?

[t00fri]

Thanks. Unfortunately, my telescope is actually a "cheap supermarket telescope". Do you think I could just fashion a device to block out Sirius A as you describe?

That is the much harder part, and in my case required a lathe with centering facilities to make the tiny steel cone for the eyepiece and the metal mounting and adjustment for an additional lens that properly maps the cone... Fortunately I had such tools available throughout my youth (and still today as well ). Moreover, for the cone being effective, you need a pretty accurate motor drive , otherwise Sirius A will immediately move away from the cone ...

Well if you think your optics "luckily" provides a relatively crisp image of the moon at high magnification, you might just try, nevertheless.

But without the rotatable hexagonal cardboard mask you have no chance. Since making the mask is less than 30 mins of work, I would simply try it. You will learn something, also if not "successful" You need to use the biggest eyepiece magnification (shortest available focus).

If you are interested in the physics behind such diffractive masks, have a look in the net under the keyword: apodization. That's what the mask is about! You will be surprised and see Fourier transforms at work and some very interesting basic physics (optics).

With Celestia, you first locate the position of B relative to North. You need to know rather precisely beforehand, WHERE to look for B in your telescope! Then start rotating the mask slowly and watch your hexagonal A component carefully between it's rotating 6 spikes.

Fridger

PS: The "black hiding spot" of course only makes sense, if your optics is able to exquisitely map very bright point sources into a close to "theoretical" diffraction disc in the focal plane. Cheap telescopes will generate plenty of noise and spikes for such bright objects, which will protrude from the black disk, thus turning it useless...