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How do I know what I can resolve

blinky

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blinky

blinky

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Not sure how to word this, I have managed to resolve a double star before (Cannot remember what one) and I wanted to try beatleguise. I could see it was a double star but I could not resolve it into 2 distinct stars. Should an 8" Newt be able to resolve this? I see from Starry Night Pro that the seperation is 10" what should I resonably be able to resolve in my scope?

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Greg

Greg

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Found this little ditty....Reminds me of the start of the Twilight Zone!

http://physics.kenyon.edu/coolphys/FranklinMiller/protected/Power.html

Or..

The resolution of the telescope is a measure of how sharply defined the details of the image can be. The laws of diffraction make a certain amount of blurring unavoidable, because of the wave nature of light. If two stars are very close, a given telescope may not be able to separate them into two distinct points. The smallest angular separation that can be unambiguously distinguished is called the resolving power of the telescope and is proportional to the ratio of the wavelength of light being observed to the diameter of the telescope. Thus, the larger the diameter, the smaller the minimum angular separation and the higher the resolving power.

The magnification, or power, of the telescope is relevant only when an eyepiece, or ocular, is used to magnify the image for visual inspection. The angular size of the virtual image seen by the observer will be larger than the actual angular size of the object. The ratio of these two sizes is the magnifying power and is equal to the ratio of the focal lengths of the objective and ocular. Any desired magnification can be obtained with a given telescope by the use of an appropriate ocular, but beyond a point determined by the resolving power, higher magnification will reveal no further details.

In addition to diffraction, other defects limit the performance of real optical systems. The most serious of these for lenses is chromatic aberration. Other defects include coma, astigmatism, distortion, and curvature of field. In general, it is easier to eliminate these faults in the reflector than in the refractor.

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blinky

blinky

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Hmmm..... I though I did the collimmmy thingy last week. Will need to have another go at it. Would you say that Beatleguise is a hard star to resolve into 2 stars or is it quite an easy one? I ask as the EP's that I have are quite cheap (Paid £30 odd quid for the 5 of them brand new) and I am wondering if it is these that are at fault and not the scope?

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The Warthog

The Warthog

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I was a little surprised to hear that Betelgeuse was a double, and checked three online references with no mention of this fact. Of course, if it is not a double, that would make it hard to split. I'll check again when I get home, of course.

Thre is a nice wide double on the right side of Orion's belt (your right). It is a little hard to realize you are looking at it, because the spread is wide and the other star is fairly dim.

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FLO

FLO

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Have been Googling:

Betelgeuse is not a binary, it is a semi-regular variable star. Through normal observation, there is nothing remarkable other than its enormous size (15 times more massive than the Sun) and colour.

If Betelgeuse were placed at the centre of our solar system, its diameter would extend to the orbit of Jupiter. Being so large, Betelgeuse was the first star to have 'starspots' on its disk resolved in optical images by a telescope.

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Kain

Kain

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Isn't Rigel a triple star?

I don't know of you can separate it's partners, but every time I have looked at Rigel I have only ever seen 1 star.

I'm probably wrong though.

Regarding Betelgeuse, according to the book I have here, it's a double star, though I have just looked on the net, and can't find anything that says it is. The book is probably wrong.

Kain

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John

John

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Isn't Rigel a triple star?

I don't know of you can separate it's partners, but every time I have looked at Rigel I have only ever seen 1 star.

I'm probably wrong though.

Regarding Betelgeuse, according to the book I have here, it's a double star, though I have just looked on the net, and can't find anything that says it is. The book is probably wrong.

Kain

I was able to resolve Rigel with my ED100 scope a few weeks ago. It's not so much the closeness of the pair but their unequal brightness that is the challenge - the dimmer companion tends to get a bit lost in the glare of the brigter star. Longer focal length refractors help here because star images tend to be "tighter".

Gamma in Leo (Algeiba) is a nice double of more or less equal brightness which makes a nice sight. When I 1st looked at this 25 years ago I could resolve it relatively easily with a 60mm Tasco refractor - I think the pair is closer now and I reckon 60mm would not be enough.

John.

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FLO

FLO

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Starry Nihght PRO describes it as a variable star.

A variable star is where one star closely orbits another.

It cannot be 'split' like a binary but the combined magnitude can be seen to rise and fall as they orbit each other.... I think.

No doubt the more experienced cosmologists will put some flesh on that definition :D

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GazOC

GazOC

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Starry Nihght PRO describes it as a variable star.

A variable star is where one star closely orbits another.

It cannot be 'split' like a binary but the combined magnitude can be seen to rise and fall as they orbit each other.... I think.

No doubt the more experienced cosmologists will put some flesh on that definition :)

A variable star is one that changes magnitude, they come in several flavours. Some stars are intrinsically variable (Betelgeuse is one of these), others appear to be variable because a companion star passes in front of them as viewed from our line of sight (ie. Algol).

http://hoa.aavso.org/varstar.html

The link also lists Betelgeuse as having a mag 14 companion, I'll have to admit that I've never seen it. Maybe the primary is too bright? One for Lunator me thinks..... :D

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blinky

blinky

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You are correct Steve I do have an Orion Optics (UK) 8" Newt. I thought the scope was good and did manage to split a double before. I dont have many books etc with targets in it (Other than the excellent turn left at Orion) so just looked at Starry Night Pro picked a star I knew and looked at the data. I assumed (Wrongly now!) that it was a double. Guess I will need to invest in another book (Asking Santa for some) or have a good google for some targets.

As always thanks to everyone for the advice/info :D

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Astroman

Astroman

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Betegeuse is a Mira variable AND a multiple star system, as are most stars. The star is of the type that actually grows larger and smaller over a period of about 450 days. They types of variables are many, with the most interesting being Cataclysmic Variables, (CV's), that are acutally two stars trading material. (I'm giving a talk on these again in May.) I think the reason most people don't know about Betelgeuse's companions are the difference in contrast. Betelgeuse is so bright, it's extremely difficult to see the companions, or even know it when you do. Rigel and Sirius are the same. So you split it, so what? It's very hard, but something like Algeiba in Leo, I split for the public all the time because it's easy to do, they're very close together and very nice in color. The variables Gaz refers to are eclipsing binaries and are also quite interesting. They give us a look at the masses and compositions of the stars in question, and that helps verify other types of measurements done by other means.

Isn't this great? :D

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lunator

lunator

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This is the information from the WDS for Betelgeuse.

5h55m10.20s +07°24'25.0" D* H 6 39 Aa m: 0.90/ 1940: 0.1"/ 92° 1983: 0.1"/273° Sp: n:N

5h55m10.20s +07°24'25.0" D* KAR 1 Ab m: 0.50/14.50 1982: 0.5"/265° 1983: 0.5"/278° Sp:M n:Np DM:+07 1055

5h55m10.20s +07°24'25.0" D* H 6 39 AB m: 0.50/14.50 1891: 39.8"/110° 1891: 39.8"/110° Sp: n:

5h55m10.20s +07°24'25.0" D* H 6 39 AC m: 0.50/14.20 1891: 62.0"/290° 1891: 62.0"/290° Sp:M n:

5h55m10.20s +07°24'25.0" D* H 6 39 AD m: 0.90/13.50 1877: 77.6"/348° 1912: 76.0"/347° Sp: n:

5h55m10.20s +07°24'25.0" D* H 6 39 AE m: 0.90/11.00 1786:161.8"/152° 1917:174.4"/153° Sp: n:

5h55m10.30s +07°24'25.0" * HR 2061 HD 39801 Fl: 58 Ba:Alp const:Ori mV: 0.50 b-v: 1.85 sp: M1-2Ia-Iab pm: 0.026 0.009 ;BETELGEUSE; Betelguex; Betelgeuze; Beteiguex; Al Mankib

Ass you can see it is a very tight Binary that amateur scopes are not going to split. With an 8" scope you may be able to spot the D&E components. But at this distance they are most likely background field stars and just line of sight (optical).

Cheers

ian

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