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Globular cluster occultation timing

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#1 Lucullus

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Posted 15 September 2019 - 05:07 AM

Has it ever been tried to record an asteroid occultation over several stars in a dense globular cluster?

Or a (grazing/total) lunar occultation by a globular cluster?



#2 beggarly

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Posted 15 September 2019 - 06:18 AM

You can download the Zodiacal Catalogue from http://stjarnhimlen.se/zc/zc.zip (http://stjarnhimlen.se/zc/) and take a look at file ZC_DSKY.

Globular cluster are located in the Milky Way's halo, so not many are close enough to the ecliptic to be occulted by the Moon.

 

http://www.asteroidoccultation.com/

http://www.lunar-occ...ota/iotandx.htm

http://www.asteroido...m/observations/

http://www.euraster.net/links.html - there's software to calculate your own predictions.

 

Edit. M80, M4, M19, NGC6293, NGC6304, NGC6316, M9, NGC6356, NGC6355, NGC6624, M28, NGC6638, M22, M75 and M72. 15 globular clusters (of reasonable magnitude) out of 150 so far in the Milky Way.


Edited by beggarly, 15 September 2019 - 12:53 PM.


#3 TOMDEY

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Posted 15 September 2019 - 06:42 AM

I'm not into that kinda stuff... but seems the theory requires timing of the snuff(s)/return(s) to be as (temporally) accurate as possible. That would require stars as bright as possible, so the video can run as fast as possible... meaning fast frame rates/ very short exposures... The only thing that would optimize that is --- very large scopes along the skinny ground trajectory.

 

Imagine trying to definitively record the individual stars in a globular with exposure times in the 1-10 milisec range.

 

Martin Harwit covers this kinda trade-space stuff, in profuse detail, in his book Cosmic Discovery, excerpt here. The limits on observation are fundamental. Even with 100% quantum efficiency, you can go just so fast, and no faster, on the temporal scale of resolution... for a number of reasons that trade against spectral bandwidth, wavelength etc. etc. His book is quite rigorous and profound... a rather difficult read, to fully-grasp. I'm reading it for the 4th time through. Both scientific and philosophical. The context is Information Theory, specifically in the field of observational astronomy.   Tom

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Edited by TOMDEY, 15 September 2019 - 06:43 AM.

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#4 Jim Davis

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Posted 15 September 2019 - 07:57 AM

 

Globular cluster are located in the Milky Way's halo, so not many are close enough to the ecliptic to be occulted by the Moon.

 

Yes, they are in the halo, but the Milky Way is nearly perpendicular to the ecliptic. The Moon passes close to many globular clusters. The are many of them in Scorpius, Sagittarius and Ophiuchus. On September 7th, the Moon passed just to the north of M-22.


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#5 Inkswitch

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Posted 15 September 2019 - 09:22 AM

I'm reading it for the 4th time through.

 

I will soon be reading it for the first time.  It seems a great recommendation based solely on the excerpt.  Thanks much!



#6 TOMDEY

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Posted 15 September 2019 - 11:37 AM

I will soon be reading it for the first time.  It seems a great recommendation based solely on the excerpt.  Thanks much!

You're welcome, Lawen! It is availble (used) on AbeBooks... hardcover, for just a few dollars... shipped!

 

https://www.abebooks...overy&kn=&isbn=

 

    Tom


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#7 llanitedave

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Posted 15 September 2019 - 12:29 PM

You can download the Zodiacal Catalogue from http://stjarnhimlen.se/zc/zc.zip (http://stjarnhimlen.se/zc/) and take a look at file ZC_DSKY.

Globular cluster are located in the Milky Way's halo, so not many are close enough to the ecliptic to be occulted by the Moon.

 

http://www.asteroidoccultation.com/

http://www.lunar-occ...ota/iotandx.htm

http://www.asteroido...m/observations/

http://www.euraster.net/links.html - there's software to calculate your own predictions.

Some are, though.  M-4 and M-22 come to mind.




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