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Vesta seen as disc

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#1 HSp

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Posted 07 March 2021 - 06:48 PM

I am a schoolboy at a gym and on astro holidays at my uncle’s farm in a small village. It is my start in astronomy in the 1970s. Just in front of the house, the sky is black. Only 2 bulbs are on the street in the village. Tavern guests use lanterns to find their way home.

I use a little tripod put on a desk with a pair of 6x30 Leitz binoculars to look at Vesta as she travels her way through Virgo. Her changes of position are easily detected after a few nights of marking the stars on a paper. And one of them is moving between the others!

One night, I try Vesta with the unaided eye – and there she is!

 

 

 

Decades have passed as Martin presents Vesta in his 28 cm refractor (refer to “Modern and direct visual observations of Sirius B”). We do a few different star hopping approaches and aim each time at the same star. The star is strikingly yellow, reflected sunlight. And with a Barlow and correctly adjusted ADC, the disc of Vesta is clearly seen! We are at 500x magnification. We compare with a star that has the same magnitude and is in a short distance in right ascension: The star shows 2 diffraction rings. Its central disc is half the diameter than the disc of Vesta. We go back to Vesta: again it shows the disc with the double diameter than the central disc of the star. The disc has no diffraction rings. The disc of Vesta is computed to be 0.51 arc seconds diameter. As Martin later in the house, skilled in mental arithmetic, calculates in a split of a second, states, this is the theoretical resolution of his objective. I believe, he actually lives in these equations.

Euphoric of the visibility of the disc of Vesta, we aim the telescope at Omega Leonis: the components are easily and clearly separated. Each shows 2 diffraction rings, their central discs are separated by darkness! The pair has 0.8 arc seconds.

Earlier that night, there were cirrus and altostratus clouds in the south and southwest that prevented to look at Procyon. As you might remember, I had promised you to look at Procyon (refer to “Modern and direct visual observations of Sirius B”). Now, we made a second approach, but found it flickering, because in the meantime, Sirius and Procyon were above the chimneys of houses of the village. When there were the clouds, we did deep sky objects in the zenith and more to the north. M3 was spectacular, M53 quite an open cluster and NGC 5053 revealed many stars!

At the end of our observing session, I put the cover on the objective lens. Beside the name of the Russian company, the serial number “01” is engraved.


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#2 PirateMike

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Posted 07 March 2021 - 07:02 PM

Life is sweet. waytogo.gif

 

 

Miguel   8-)

 

.


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#3 HSp

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Posted 08 March 2021 - 05:26 AM

indeed!

 

And Soul exists because of God's love for It.


Edited by HSp, 08 March 2021 - 06:31 AM.

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#4 Mirzam

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Posted 10 March 2021 - 08:21 PM

A very nice observing report!  I’m not surprised that Vesta displays an observable disk in a high quality telescope. I’ve seen the disk of Ceres in a 20 cm refractor at a favorable opposition. The appearance was almost identical to your description of Vesta.  Ceres has an apparent diameter similar to Jupiter’s moon, Europa.

 

JimC


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#5 Special Ed

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Posted 14 March 2021 - 03:20 PM

Take a look at Aquarellia's Vesta observation.  cool.gif


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#6 Asbytec

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Posted 25 March 2021 - 05:32 PM

"The star shows 2 diffraction rings. Its central disc is half the diameter than the disc of Vesta. We go back to Vesta: again it shows the disc with the double diameter than the central disc of the star. The disc has no diffraction rings. The disc of Vesta is computed to be 0.51 arc seconds diameter. As Martin later in the house, skilled in mental arithmetic, calculates in a split of a second, states, this is the theoretical resolution of his objective."

That makes sense and is an exciting observation. A true point source is figured to be about 1/4 the Airy diameter. Anything larger increasingly begins to present as an extended object. Your description of the missing diffraction rings appears to be consistent with seeing more of an actual disc than a diffraction artifact. The same thing happens with the Galilean moons in smaller apertures.

(Google Amateur Telescope Optics chapter on resolution).

The interesting thing is, once a tiny object begins to resolve into a disc, the potential to see very small and very high contrast detail exists. If vista has any such feature, but probably not. Still, beginning to resolve it's disc is cool enough.

Edited by Asbytec, 25 March 2021 - 05:35 PM.



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