NGC 6791 in Lyra - A galactic survivor

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Date: 17 May 2007 19:38:21
From: Anthony Ayiomamitis
Subject: NGC 6791 in Lyra - A galactic survivor

Dear friends,

Perhaps the oldest open cluster in our galaxy is NGC 6791 in Lyra which
has been estimated by Salaris (2004) to be 10.2 billion years old (ie.
about 80% the age of the universe). For an image of this galactic
survivor taken early this morning and under volatile seeing, please see
http://www.perseus.gr/Astro-DSO-NGC-6791.htm .

Clear skies!

Anthony.

Date: 19 May 2007 04:09:17
From: oriel36
Subject: Re: NGC 6791 in Lyra - A galactic survivor

On May 19, 11:36 am, Anthony Ayiomamitis <anth...@perseus.no2spam.gr >
wrote:
> oriel36 wrote:
> > On May 17, 10:29 pm, Anthony Ayiomamitis <anth...@perseus.no2spam.gr>
> > wrote:
>
> >>William R. Mattil wrote:
>
> >>>Anthony Ayiomamitis wrote:
>
> >>>>Dear friends,
>
> >>>>Perhaps the oldest open cluster in our galaxy is NGC 6791 in Lyra
> >>>>which has been estimated by Salaris (2004) to be 10.2 billion years
> >>>>old (ie. about 80% the age of the universe). For an image of this
> >>>>galactic survivor taken early this morning and under volatile seeing,
> >>>>please seehttp://www.perseus.gr/Astro-DSO-NGC-6791.htm.
>
> >>>Anthony,
>
> >>Hi Bill,
>
> >>>Refractors don't have diffraction spikes :)
>
> >>They were added with the help of a pair of strings for the purposes of
> >>this imaging project and purely for aesthetic purposes. ;-) :-)
>
> >>Anthony.
>
> >>>Bill- Hide quoted text -
>
> >>- Show quoted text -
>
> > O.K. sunshine,now you are front and center and can openly admit to
> > adding aesthetic flourishes to your images.
>
> Did I ever deny or avoid such a "confession"? In fact, if you check the
> archives here on s.a.a. you will find many questions (and answers!)
> surrounding my open star cluster images and the spikes for the brighter
> member stars.
>
>
>
> > As the only expert here on the astronomical principles behind the
> > creation of the 24 hour day and its application to terrestrial
> > longitudes I would like to see the procedure you used in creating the
> > analemma even though I know it is a late 17th century hoax.
>
> Enjoy:http://www.perseus.gr/Astro-Tips-Analemma.htm.... my procedure
> is described in the latter half of the page.
>

The Equation of Time has no hemispherical components and is truly a
global correction reflecting the difference between the Total,do you
hear,total length of the natural noon cycle and the 24 hour cycle.The
treatise of Huygens involves centering observations to natural noon or
natural midnight in order to apply the neccessary Equation of Time
correction to check the accuracy of clocks or to determine longitudes
using accurate clocks.

The centering technique of Huygens are exquisite and you will hear
nothing of that late 17th century 'analemmas' hoax -

'How by Observing the Rising and Setting of the Sun, and the Time by
the Watches, the Longitude at Sea may be found. '

"You may also, instead of observing the Suns Rising and Setting,
observe the Setting first, and then next morning the Rising; marking
at both times the Time show'd by the Watches; and find thence, after
the same manner as before, the Longitude of the place where the Ship
was at Midnight."

http://www.xs4all.nl/~adcs/Huygens/06/kort-E.html

"By studying the sun's azimuth on a second-by-second basis, it was
established that the vertical analemma corresponded to an exposure
schedule for precisely 12:28:16 UT+2, for it is at this time that
azimuth for the summer and winter solstice line-up perfectly. The
ephemeris of the sun at this time was also used to examine the range
in altitude from January 1st to December 31st in order to arrive at an
imaging schedule for the analemma. "

What you are doing is allowing a 24 hour day to determine the position
of the Sun whereas the correct principles use natural noon when the
Sun crosses the meridian to determine the 24 hour day -

"Draw a Meridian line upon a floor (the manner of doing which is
sufficiently known; and note, that the utmost exactness herein is not
necessary:) and then hang two plummets, each by a small thred or wire,
directly over the said Meridian, at the distance of some 2. feet or
more one from the other, as the smalness of the thred will admit. When
the middle of the Sun (the Eye being placed so, as to bring both the
threds into one line) appears to be in the same line exactly .....are
then immediately to set the Watch, not precisely to the hour of 12.
but by so much less, as is the Aequation of the day by the Table"

There is or never was a figure 8 involved in creating the 24 hour day
via the Equation of Time correction,the techniques of Huygens involve
various ways to center the positions of the Sun to natural noon or
true midnight.

>
>
> > If you are more comfortable explaining the procedure using the values
> > supplied by Huygens in the Equation tables provided below (as
> > opposed to 'analemmatic' tables) then be my guest -
>
> >http://www.xs4all.nl/~adcs/Huygens/06/kort-E.html
>
> The title for the above link reads "Instructions Concerning the Use of
> Pendulum-Watches for finding the Longitude at Sea". What does this have
> to with my photographing the sun at precisely the same time over the
> course of a year?
>

If you are using the Equation of Time as an excuse for that late 17th
century 'analemma' hoax then be sure you know what you are actually
doing.It does highlight exactly what went wrong centuries ago as
Flamsteed tried to justify the Earth's motions by using the return of
a star to a meridian,the first time anyone tried to use a clock to
justify the Earth's axial and orbital motions around the Sun in
conjunction with an astrological framework.

If you cannot grasp the actual details of Huygen's centering
techniques then let me state it with brevity. There is no figure 8
involved in the Equation of Time.

> Anthony.- Hide quoted text -
>
> - Show quoted text -

Date: 19 May 2007 03:10:58
From: oriel36
Subject: Re: NGC 6791 in Lyra - A galactic survivor

On May 17, 10:29 pm, Anthony Ayiomamitis <anth...@perseus.no2spam.gr >
wrote:
> William R. Mattil wrote:
> > Anthony Ayiomamitis wrote:
>
> >> Dear friends,
>
> >> Perhaps the oldest open cluster in our galaxy is NGC 6791 in Lyra
> >> which has been estimated by Salaris (2004) to be 10.2 billion years
> >> old (ie. about 80% the age of the universe). For an image of this
> >> galactic survivor taken early this morning and under volatile seeing,
> >> please seehttp://www.perseus.gr/Astro-DSO-NGC-6791.htm.
>
> > Anthony,
>
> Hi Bill,
>
>
>
> > Refractors don't have diffraction spikes :)
>
> They were added with the help of a pair of strings for the purposes of
> this imaging project and purely for aesthetic purposes. ;-) :-)
>
> Anthony.
>
>
>
>
>
> > Bill- Hide quoted text -
>
> - Show quoted text -

O.K. sunshine,now you are front and center and can openly admit to
adding aesthetic flourishes to your images.

As the only expert here on the astronomical principles behind the
creation of the 24 hour day and its application to terrestrial
longitudes I would like to see the procedure you used in creating the
analemma even though I know it is a late 17th century hoax.

If you are more comfortable explaining the procedure using the values
supplied by Huygens in the Equation tables provided below (as
opposed to 'analemmatic' tables) then be my guest -

http://www.xs4all.nl/~adcs/Huygens/06/kort-E.html

Date: 19 May 2007 13:36:18
From: Anthony Ayiomamitis
Subject: Re: NGC 6791 in Lyra - A galactic survivor

oriel36 wrote:
> On May 17, 10:29 pm, Anthony Ayiomamitis <anth...@perseus.no2spam.gr>
> wrote:
>
>>William R. Mattil wrote:
>>
>>>Anthony Ayiomamitis wrote:
>>
>>>>Dear friends,
>>
>>>>Perhaps the oldest open cluster in our galaxy is NGC 6791 in Lyra
>>>>which has been estimated by Salaris (2004) to be 10.2 billion years
>>>>old (ie. about 80% the age of the universe). For an image of this
>>>>galactic survivor taken early this morning and under volatile seeing,
>>>>please seehttp://www.perseus.gr/Astro-DSO-NGC-6791.htm.
>>
>>>Anthony,
>>
>>Hi Bill,
>>
>>
>>
>>
>>>Refractors don't have diffraction spikes :)
>>
>>They were added with the help of a pair of strings for the purposes of
>>this imaging project and purely for aesthetic purposes. ;-) :-)
>>
>>Anthony.
>>
>>
>>
>>
>>
>>
>>>Bill- Hide quoted text -
>>
>>- Show quoted text -
>
>
> O.K. sunshine,now you are front and center and can openly admit to
> adding aesthetic flourishes to your images.

Did I ever deny or avoid such a "confession"? In fact, if you check the
archives here on s.a.a. you will find many questions (and answers!)
surrounding my open star cluster images and the spikes for the brighter
member stars.

>
> As the only expert here on the astronomical principles behind the
> creation of the 24 hour day and its application to terrestrial
> longitudes I would like to see the procedure you used in creating the
> analemma even though I know it is a late 17th century hoax.

Enjoy: http://www.perseus.gr/Astro-Tips-Analemma.htm .... my procedure
is described in the latter half of the page.

>
> If you are more comfortable explaining the procedure using the values
> supplied by Huygens in the Equation tables provided below (as
> opposed to 'analemmatic' tables) then be my guest -
>
> http://www.xs4all.nl/~adcs/Huygens/06/kort-E.html
>

The title for the above link reads "Instructions Concerning the Use of
Pendulum-Watches for finding the Longitude at Sea". What does this have
to with my photographing the sun at precisely the same time over the
course of a year?

Anthony.

Date: 17 May 2007 17:26:55
From: Ben
Subject: Re: NGC 6791 in Lyra - A galactic survivor

<snip snip snip >
> In fact I had a slightly different problem with M92 (also from last
> night) and which I purposely did not post. Anyway, since the cat is now
> out of the bag, here you go:http://www.perseus.gr/Astro-DSO-NGC-6341.htm... this one will also
> require a repeat visit.
>
> Anthony.

That's really interesting. Is it a problem on the blue channel
or are you picking up on authentic spectral information?

One used to expect a certain homogenous distribution of
spectral classes in the globulars but this has proven to
be not necessarily the case. I doubt those are "blue
stragglers". Why then the blue tint in those particular
stars? Requires repeated visits....

Ben

Date: 18 May 2007 11:00:41
From: Anthony Ayiomamitis
Subject: Re: NGC 6791 in Lyra - A galactic survivor

Ben wrote:
> <snip snip snip>
>
>>In fact I had a slightly different problem with M92 (also from last
>>night) and which I purposely did not post. Anyway, since the cat is now
>>out of the bag, here you go:http://www.perseus.gr/Astro-DSO-NGC-6341.htm... this one will also
>>require a repeat visit.
>>
>>Anthony.
>
>
> That's really interesting. Is it a problem on the blue channel
> or are you picking up on authentic spectral information?

What is very odd is that the histograms are perfectly matched and, as
such, I cannot explain the blue tint. I also corrected for the
differential QE of the camera between R, G and B as well as atmospheric
extinction.

>
> One used to expect a certain homogenous distribution of
> spectral classes in the globulars but this has proven to
> be not necessarily the case. I doubt those are "blue
> stragglers". Why then the blue tint in those particular
> stars? Requires repeated visits....

I have a second CCD camera coming (SBIG ST-10XME) and I am interested to
see if it also behaves the same.

Anthony.

>
> Ben
>

Date: 17 May 2007 17:08:05
From: Ben
Subject: Re: NGC 6791 in Lyra - A galactic survivor

Date: 17 May 2007 16:02:51
From: Ben
Subject: Re: NGC 6791 in Lyra - A galactic survivor

On May 17, 4:29 pm, Anthony Ayiomamitis <anth...@perseus.no2spam.gr >
wrote:
> William R. Mattil wrote:
> > Anthony Ayiomamitis wrote:
>
> >> Dear friends,
>
> >> Perhaps the oldest open cluster in our galaxy is NGC 6791 in Lyra
> >> which has been estimated by Salaris (2004) to be 10.2 billion years
> >> old (ie. about 80% the age of the universe). For an image of this
> >> galactic survivor taken early this morning and under volatile seeing,
> >> please seehttp://www.perseus.gr/Astro-DSO-NGC-6791.htm.
>
> > Anthony,
>
> Hi Bill,
>
>
>
> > Refractors don't have diffraction spikes :)
>
> They were added with the help of a pair of strings for the purposes of
> this imaging project and purely for aesthetic purposes. ;-) :-)
>
> Anthony.
>
>
>
>
>
> > Bill- Hide quoted text -
>
> - Show quoted text -

Antoni,

Excellent capture of my old nemesis. To date I have only resolved
one star here and that is U Lyrae and I am completely confident
that it is not part of the cluster.

I noticed on your high resolution image the foreground stars seem
to take on a light green color. You can get the same sort of effect
playing around with ALADIN images by manipulating the color
channels. This could be a potentially useful device for eliminating
the background / foreground contamination which is a problem
in many open clusters. (compare NGC 7789).

What do you think?

Ben

Date: 18 May 2007 02:15:42
From: Anthony Ayiomamitis
Subject: Re: NGC 6791 in Lyra - A galactic survivor

Ben wrote:
> On May 17, 4:29 pm, Anthony Ayiomamitis <anth...@perseus.no2spam.gr>
> wrote:
>
>>William R. Mattil wrote:
>>
>>>Anthony Ayiomamitis wrote:
>>
>>>>Dear friends,
>>

<snip >

>>
>>
>
> Antoni,

Hi Ben,

>
> Excellent capture of my old nemesis. To date I have only resolved
> one star here and that is U Lyrae and I am completely confident
> that it is not part of the cluster.
>

This DSO has been on my list of targets for some time and it is now
getting into position. I must revisit it, for the result could be better.

> I noticed on your high resolution image the foreground stars seem
> to take on a light green color. You can get the same sort of effect
> playing around with ALADIN images by manipulating the color
> channels. This could be a potentially useful device for eliminating
> the background / foreground contamination which is a problem
> in many open clusters. (compare NGC 7789).
>
> What do you think?

My seeing last night was volatile with differing FWHM between sets of
images. The night started out well when capturing the luminance portion
but things degraded thereafter with the blue being impacted the most.

I was debating about posting the result since it is not exactly where I
want it to be. However, it is a baseline image and which I will build
upon shortly with a follow-up image at the first opportunity.

In fact I had a slightly different problem with M92 (also from last
night) and which I purposely did not post. Anyway, since the cat is now
out of the bag, here you go:
http://www.perseus.gr/Astro-DSO-NGC-6341.htm ... this one will also
require a repeat visit.

Anthony.

>
> Ben
>
>

Date: 17 May 2007 21:13:35
From: William R. Mattil
Subject: Re: NGC 6791 in Lyra - A galactic survivor

Anthony Ayiomamitis wrote:
> Dear friends,
>
> Perhaps the oldest open cluster in our galaxy is NGC 6791 in Lyra which
> has been estimated by Salaris (2004) to be 10.2 billion years old (ie.
> about 80% the age of the universe). For an image of this galactic
> survivor taken early this morning and under volatile seeing, please see
> http://www.perseus.gr/Astro-DSO-NGC-6791.htm .
>

Anthony,

Refractors don't have diffraction spikes :)

Bill

Date: 18 May 2007 00:29:38
From: Anthony Ayiomamitis
Subject: Re: NGC 6791 in Lyra - A galactic survivor

William R. Mattil wrote:
> Anthony Ayiomamitis wrote:
>
>> Dear friends,
>>
>> Perhaps the oldest open cluster in our galaxy is NGC 6791 in Lyra
>> which has been estimated by Salaris (2004) to be 10.2 billion years
>> old (ie. about 80% the age of the universe). For an image of this
>> galactic survivor taken early this morning and under volatile seeing,
>> please see http://www.perseus.gr/Astro-DSO-NGC-6791.htm .
>>
>
> Anthony,

Hi Bill,

>
> Refractors don't have diffraction spikes :)

They were added with the help of a pair of strings for the purposes of
this imaging project and purely for aesthetic purposes. ;-) :-)

Anthony.

>
> Bill

Date: 17 May 2007 16:53:05
From: Sam Wormley
Subject: Re: NGC 6791 in Lyra - A galactic survivor