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Messages posted by: wildcard
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One of the more powerful features of Argo Navis is its in-built Telescope Pointing Analysis System (TPAS).

Most users will never need it.

However, there are some that do.

The definitive reference to using TPAS is the User Manual in the section on SETUP MNT ERRORS.
See http://www.wildcard-innovations.com.au/documentation.html

However, sometimes user's ask whether a tutorial is available and I have emailed them this response which appears below.


There is a reasonable amount to absorb initially but based on working hands-on with many customers, I assure you after a few runs it will become intuitive.

Firstly, I encourage you to spend some time browsing the submenus beneath SETUP MNT ERRORS.

These sub-menus are as follows -

ACQUIRE DATA - switch SAMPLE MODE=ON to enable pointing test sampling
COMPUTE ERRORS - will attempt to fit the pointing model defined in DEFINE MODEL
DEFINE MODEL - used to define which error terms will be fitted by COMPUTE ERRORS
REVIEW DATA - used to examine raw and fitted pointing data residuals along with total raw and fitted RMS. Also allows for deletion of samples.
SET ERROR VALUES - two submenus beneath this -
IN USE NOW - allows one to examine and manually modify mount error terms currently in use by the pointing kernel
SAVED IN NVRAM - allows one to examine and manually modify mount error terms saved in non-volatile memory for later sessions

In a nutshell, you will want to enter your various SETUP parameters as before.
Set DATE/TIME LOCATION as horizon and pole checking is performed.
Highly recommend that you set REFRACTION=ON

If you have an Argo Navis serial port free, have it startup with the navis command before
you begin the pointing test. You will then be able to dump the data for analysis by Wildcard.

As you will see later, when SAMPLE MODE=ON, a new submenu is enabled when you press ENTER in GUIDE mode.
This new submenu has a selection of DESCRIPTION or SAMPLE MNT ERROR.
When DESCRIPTION appears, if ENTER is pressed, scrolling object description appears as in previous firmware.
When SAMPLE MNT ERROR appears, if ENTER is pressed, object position is sampled.

To preform pointing test, Ideally install reticle or reasonable power eyepiece.
Always center stars as accurately as possible to reduce error.

Perform FIX ALT REF (AUTO ADJUST ON is OK to use) and two-star alignment as before.

Only sample (bright - 6th mag or brighter) stars (ideally those that appear in bright star catalog) or planets.

Use MODE IDENTIFY or MODE TOUR to select a bright star. Suggest start with last alignment star.
When GUIDE appears, press ENTER. When DESCRIPTION appears,
spin DIAL until SAMPLE MNT ERROR appears. Center star/planet in reticle. Press ENTER.
Argo Navis will report pointing residual.

Then suggest sample first alignment star as above.

Sample two more stars. Thus you have so far sampled 4 stars in all.
This is sufficient for you to perform an initial fit.

Press ENTER. Argo Navis will report Root Mean Square (RMS) and Population Standard
Deviation (PSD) of fit. Don't expect any improvement yet. All values are in arc minutes.
Argo Navis will also report IE=XXX where XX.X is the computed value for the fit of the index error in elevation (Alt)
Press ENTER to USE TERM and return to pointing test.

Sample one or two more stars.

Press ENTER and set NPAE=COMPUTE. Press EXIT twice.

Argo Navis will now also attempt to fit for Az to Alt axes not being orthogonal (NPAE).
Take note if RMS and PSD have reduced from before. Take note of standard
deviation of NPAE term (the number after the +/-). Only accept (i.e. USE NOW) if value of term
is at least two or three times larger than its standard deviation.
Acceptance of all terms can also be aborted by pressing EXIT.
Assuming NPAE looks real, press ENTER a few times to accept IE and NPAE as USE NOW.

You can review your pointing test data at any time.
To review pointing data, select REVIEW DATA.
Last sampled point appears as default. Spin DIAL anti-clockwise to view earlier samples.
Large DELTA (triangle) means raw pointing residual.
Spin DIAL fully clockwise until END OF DATA and examine RAW RMS.
Press ENTER and change to DELTAS=FITTED. Press ENTER or EXIT.
Display now shows FIT RMS. Small delta symbol (d) means fitted residual.
Spin DIAL anti-clockwise to examine residuals of samples for the current model in use now.
To delete an item, press ENTER. To delete all items, go to START OF DATA and press ENTER.

Now sample some more stars. Try and take samples with good spread in Alt and Az (i.e. whole sky).
System will not allow to sample star unless 10 degrees above horizon. System will
not allow star to be sampled too close to zenith. Probably best to avoid sampling greater than 85 degrees in Alt.

Use DEFINE MODEL to experiment with other error terms, such as left-right collimation
error (CA) and the two eccentric terms (ECEC and ECES). ECES also accounts for truss tube flexure.
As rule of thumb, probably need about 15 stars with good distribution in Alt to
first characterize CA as it is hard to distinguish from NPAE. Probably need 20 to 100 stars
to more reliably determine NPAE, CA, IE, ECES and ECEC. Suggest always accept IE even if standard
deviation appears larger than value itself.

Think of DEFINE MODE and COMPUTE as a work-bench where you can experiment with
different terms and see if they improve your pointing.
Basically you want to add or remove combinations of terms from within DEFINE MODEL
and then go back and COMPUTE. If the RMS and in particular the PSD does not drop, just press EXIT
and go back to DEFINE MODEL and try again. Normally you will always want to use IE and possibly NPAE.
Sometimes you will also want CA or maybe CA in place of NPAE and maybe ECEC and/or ECES.

If you want to save terms for the next session, never save IE. NPAE, ECEC and ECES are generally
persistent on many mounts and OK to save. CA can vary from session to session with collimation,
eyepieces, etc, so it may not be worth saving. To save terms, when the system gets to the point where
it says USE NOW after pressing ENTER in COMPUTE, you can change USE NOW to USE NOW & SAVE.
During a subsequent observing session you can fix terms line NPAE, ECEC and ECES in
DEFINE MODEL as a constant value. Just spin the DIAL from COMPUTE to the constant value.
By fixing terms, on a subsequent observing run, you can perform a much shorter pointing
run, maybe (4 to 5 stars, which) allows you to nail IE and CA as well as some index error
and tilt terms that are internal to the system but not reported.

As a rule of thumb, if you have 10000 step encoders, that is equivalent to about 2.1' per encoder step.
We have used some mounts where we can get RMS results around 2.1'. In other words, that value
gives you some feel for about as good as you can get when the system becomes encoder resolution
limited. However, we have seen some mounts where the RMS value can be higher, particular if there
are other unmodeled phenomena occurring or non-systematic (i.e. random) behaviour such as the top-end
suddenly moving on the truss poles if it were not tightened properly.

I will also provide here some additional information on the information that is reported to
you whenever you sample a star in GUIDE mode.

Whenever you sample a star, the system will show for 2 seconds how many
stars you have sampled (ITEM= and what the pointing residual was in degrees, arc minutes or arc seconds
for that sample. Like ALIGN mode, you can re-sample if your eye-finger co-ordination was out.

Currently we only allow a star to appear once in the sample data. If you come back
and re-sample, you replace the original datum point.

When you sample a star in GUIDE mode, the delta it reports is always for the current pointing model you have in place.
It you have no pointing model in place, a big DELTA (Greek Triangle=) will be reported.
If you have a pointing model in place, a little delta (Greek d=) will be reported.
The current pointing model is defined by your alignment and whatever values appear in the

The nice thing is that when you start the pointing test, before you have fitted a model,
the DELTA reported is your raw pointing. Once you fit a model, the deltas are now those for
when the model is applied. In other words, you start to get some feedback about how your pointing
might be improving (or getting worse) as you sample each new part of the sky. An increasing pointing residual
on a star in some new part of the sky is often a good prompt to go back and COMPUTE again
and update the pointing model.

You can also always use REVIEW DATA to examine the pointing data as both RAW and FITTED.
If when examining FITTED data you notice one sample that sticks out with a very large residual
that you suspect was mis-identified, consider deleting it. Just press ENTER and the ENTER again.
However, don't get "trigger happy" when deleting an item. Sometimes the star might really
have some large pointing residual at it is a glimpse of it telling you that possibly some additional pointing terms
need to be added or something has possibly physically changed.

An introduction to standard deviation and a case study.

The following additional information may be helpful. It was written
in response to a question from a customer who asked about the
significance of the standard deviations Argo Navis reports on each of
the error terms.

It also includes a case study of a pointing test done on a 20" f5 truss pole Dob.


The standard deviation gives some measure of the distribution or 'spread'
of data about the mean. Therefore, when a data item has a small standard
deviation, one would expect most of the values to be grouped around the mean.

Thus, we want the standard deviations to be as small as possible.

Suppose your data follows the classic bell shaped curve pattern.
One conceptual way to think about the standard deviation is that it is a measures of how spread out the bell is.
Shown below is a bell shaped curve with a standard deviation of 1.
Notice how tightly concentrated the distribution is.


Shown below is a different bell shaped curve, one with a standard deviation of 2.
Notice that the curve is wider, which implies that the data are less concentrated and more spread out.


Finally, a bell shaped curve with a standard deviation of 3 appears below.
This curve shows the most spread.


Now let me provide some results from a real telescope, in this case a home-built 20" f5 truss pole Dob.

A pointing test was performed on 30 stars, distributed across the sky.
Though ideally a reticle should be used, in this particular case, no reticle was used, the stars were simply centered in a medium powered eyepiece.

With no terms fitted, the RMS and PSD were as follows -
RMS = 7.5'
PSD = 7.5'
Furthermore, examining the data in REVIEW DATA, the largest raw error on any star
was 16.4'.

When IE and NPAE were fitted the results were as follows -
IE = -0.0' +/- 0.1'
NPAE = +18.5' +/- 1.1'
RMS = 2.2'
PSD = 2.4'

Even though the standard deviation of IE was 0.1, which was larger than its value of 0.0,
we always keep IE.

The value of NPAE looks plausible or 'real' because its value of +18.5' is nearly 17 times
larger than its standard deviation of +/-1.1'
One analogy is to think of a signal (perhaps a radio signal) and then think of noise (perhaps
radio interference or static). Here the +18.5' is the signal and the +/-1.1' is the noise.
We want a large 'signal-to-noise' ratio, which is what we have got.

Now let us attempt to add the term ECES, which can account for a non-centered
Alt axis encoder as well as any tube flexure. The results were as follows -
ECES = +4.4' +/- 1.9'
IE = -3.2' +/- 1.4'
NPAE = 19' +/- 1.0'
RMS = 2.0'
PSD = 2.2'

Notice that the value of ECES is about 2.3 times the value of its standard deviation.
Therefore it looks plausible, but since its signal-to-noise-ratio is low, we would keep
an eye on it. Note how the signal-to-noise on NPAE improved slightly, now 19-to-1.
Also we note that the RMS decreased and most importantly the PSD also decreased.
If the PSD had increased, then the ECES term would probably not be worth keeping.
Notice, by the way, that this mount now has an RMS value that can be considered
close to encoder resolution limited. An excellent result. A quick examination of
the fitted error value residuals in REVIEW DATA also showed that the largest
error on any star had dropped to 3.7'. In fact, further examination showed that
the star that originally showed the largest raw pointing error of 16.4' dropped
down to 20" once fitted!

To continue with this case study, could the overall RMS/PSD be improved further
by adding another term? Let us try adding ECEC. The results we get are -
ECEC = +5.4' +/- 5.3'
ECES = +9.4' +/- 6.1'
IE = -10.1' +/- 8.1'
NPAE = 18.9' +/- 1.0'
RMS = 2.0'
PSD = 2.3'

Note how the signal-to-noise ratio of the new term, ECEC, is very low, nearly 1:1.
This tells us that ECEC doesn't look plausible. Other clues include the fact that the standard
deviations of some of the other terms increased and the PSD also increased.
Therefore, we would reject ECEC.

Finally, let us try and use CA. The results we get are -
CA = 7.7' +/- 8.1'
ECES = 4.4' +/- 1.9'
IE = -3.2' +/- 1.4'
NPAE = +13.3' +/- 6.1'
RMS = 2.0'
PSD = 2.2'

Note how the standard deviation of the CA term is greater than CA itself. It looks like
it is all noise. Notice also how the signal-to-noise ratio of NPAE also worsened to 2.2'.
The RMS and PSD values also did not improve. Adding CA therefore looks as if it
doesn't help and in fact possibly worsens the statistical integrity of the model.
If the pointing test had been extended to include more stars, particularly some additional
stars with altitudes in the range 60 to 80 degrees, it might then have been worth
trying to fit a model using CA again as it may come out of the 'noise'.

Another experiment with the above data is to remove NPAE and just use CA.
The results were as follows -
CA = 25.3' +/- 1.5'
ECES = 4.2' +/- 1.5'
IE = 3.1' +/- 1.5'
RMS = 2.1'
PSD = 2.4'

This model also looks plausible. However, notice that the RMS and PSD values increased
compared to just using NPAE instead of CA. The reason CA could be substituted for NPAE
in this manner to still get a reasonable fit is that the characteristic 'signature' of CA and NPAE
are very similar. Statisticians would say that CA and NPAE are 'highly correlated'.
In fact, we know from additional analysis of this particular data that these two terms have nearly
a 99% correlation in this instance. Therefore, it is probably best to use either NPAE or CA but not both
inthis particular case.

So how does one determine whether the mount's error is NPAE or CA? As mentioned above,
the number of pointing test samples would need to be increased, in particular selecting stars
over a greater range of altitudes, particularly more stars at higher altitudes, in order to 'unravel' the
NPAE and CA terms.

Based on further tests of this particular telescope, it looks as if the NPAE term of
around +19.0' is real and reasonably persistent. That and the ECES value of 4.4' were
saved and used in subsequent observing sessions. On these subsequent runs, the user
performed a short pointing run of typically 4 to 5 stars. In DEFINE MODEL they had -
ECES = +4.4'
NPAE = 19.0'

After performing a COMPUTE and then accepting the model, they were able to
achieve close to encoder resolution limited whole-sky pointing for the rest of the night.

Hopefully the above is helpful to you, the reader.

Think of the DEFINE MODEL and COMPUTE ERRORS menus as a laboratory workbench
where you can hypothesize what the error terms might be in DEFINE MODEL and
then determine their fit in COMPUTE ERRORS. Remember when you can hit EXIT at
any time in COMPUTER ERRORS which will cancel accepting the terms. Typically
a user will go back and forth between DEFINE MODEL and COMPUTE ERRORS in
this fashion, experimenting with various terms.

When performing a pointing test, we recommend to recompute the model often and then
accept it, as it can assist in locating further stars during the pointing test run.

After a while, you will begin to become familiar with the types of values your particular mount produces.
This Excel Spreadsheet was created by "cozens3" and contains a list of all NGC & IC objects that appear in Hartungs. They have been ranked in order of magnitude.
This list originally appeared on the Argo Navis Users' Group.
David Moorhouse in New Zealand kindly produced these lists of Hartung objects in Excel and CSV formats which was published on the Argo Navis Users' Group.

Professor E. J. Hartung first produced a comprehensive and highly respected guide for southern observers in 1968.

This book was then revised in 1995 by David Malin, who was previously the astrophotographer at the Anglo Australian Telescope, and by David Frew, an astronomer at Macquarie University here in Sydney.

This book is cherished by many southern observers and Peter Marples produced an Argo Navis user catalog from the list of objects described in the book.

For anyone new to southern skies, this book and catalog make for a wonderful starting point.
Book details here :-
In a 30 October 2019 press release from the University of California San Diego :-

UCSD wrote:
Exploring the influence of galactic winds from a distant galaxy called Makani, UC San Diego’s Alison Coil, Rhodes College’s David Rupke and a group of collaborators from around the world made a novel discovery. Published in Nature, their study’s findings provide direct evidence for the first time of the role of galactic winds—ejections of gas from galaxies—in creating the circumgalactic medium (CGM). It exists in the regions around galaxies, and it plays an active role in their cosmic evolution. The unique composition of Makani—meaning wind in Hawaiian—uniquely lent itself to the breakthrough findings.

“Makani is not a typical galaxy,” noted Coil, a physics professor at UC San Diego. “It’s what’s known as a late-stage major merger—two recently combined similarly massive galaxies, which came together because of the gravitational pull each felt from the other as they drew nearer. Galaxy mergers often lead to starburst events, when a substantial amount of gas present in the merging galaxies is compressed, resulting in a burst of new star births. Those new stars, in the case of Makani, likely caused the huge outflows—either in stellar winds or at the end of their lives when they exploded as supernovae.”

Coil explained that most of the gas in the universe inexplicably appears in the regions surrounding galaxies—not in the galaxies. Typically, when astronomers observe a galaxy, they are not witnessing it undergoing dramatic events—big mergers, the rearrangement of stars, the creation of multiple stars or driving huge, fast winds.

“While these events may occur at some point in a galaxy’s life, they’d be relatively brief,” noted Coil. “Here, we’re actually catching it all right as it’s happening through these huge outflows of gas and dust.”

Coil and Rupke, the paper’s first author, used data collected from the W. M. Keck Observatory’s new Keck Cosmic Web Imager (KCWI) instrument, combined with images from the Hubble Space Telescope and the Atacama Large Millimeter Array (ALMA), to draw their conclusions. The KCWI data provided what the researchers call the “stunning detection” of the ionized oxygen gas to extremely large scales, well beyond the stars in the galaxy. It allowed them to distinguish a fast gaseous outflow launched from the galaxy a few million year ago, from a gas outflow launched hundreds of millions of years earlier that has since slowed significantly.

“The earlier outflow has flowed to large distances from the galaxy, while the fast, recent outflow has not had time to do so,” summarized Rupke, associate professor of physics at Rhodes College.

From the Hubble, the researchers procured images of Makani’s stars, showing it to be a massive, compact galaxy that resulted from a merger of two once separate galaxies. From ALMA, they could see that the outflow contains molecules as well as atoms. The data sets indicated that with a mixed population of old, middle-age and young stars, the galaxy might also contain a dust-obscured accreting supermassive black hole. This suggests to the scientists that Makani’s properties and timescales are consistent with theoretical models of galactic winds.

“In terms of both their size and speed of travel, the two outflows are consistent with their creation by these past starburst events; they’re also consistent with theoretical models of how large and fast winds should be if created by starbursts. So observations and theory are agreeing well here,” noted Coil.

Rupke noticed that the hourglass shape of Makani’s nebula is strongly reminiscent of similar galactic winds in other galaxies, but that Makani’s wind is much larger than in other observed galaxies.

“This means that we can confirm it’s actually moving gas from the galaxy into the circumgalactic regions around it, as well as sweeping up more gas from its surroundings as it moves out,” Rupke explained. “And it’s moving a lot of it—at least one to 10 percent of the visible mass of the entire galaxy—at very high speeds, thousands of kilometers per second.”

Rupke also noted that while astronomers are converging on the idea that galactic winds are important for feeding the CGM, most of the evidence has come from theoretical models or observations that don’t encompass the entire galaxy.

“Here we have the whole spatial picture for one galaxy, which is a remarkable illustration of what people expected,” he said. “Makani’s existence provides one of the first direct windows into how a galaxy contributes to the ongoing formation and chemical enrichment of its CGM.”

Full press release, pictures, video here :-
Kevin Gill, a software engineer at NASA’s Jet Propulsion Laboratory working on data visualization and analysis projects, has assembled this remarkable short video :-

moebius9 wrote:Hi Gary,

2500m, 2 hours from Nice, the best sky in France !!

The best of both worlds! Close to the sea and to the mountains.
Impressive image! smilie Thanks for posting it as it shows what is possible.
Astromaniac wrote:Hi Gary,
Thanks for replying so promptly. The settings on my AN are correct. So just to clarify: when you say LX200 GOTO you mean (in settings Sky Safari) Telescope Type LX200 Classic and Mount Type Equatorial GoTo (Fork). Is that correct?


Stella Observatory,
Macedon, Victoria,

Hi John,

That is correct.

The Alt-Az. GoTo setting will also do exactly the same but the important thing is the GoTo.

Also on the Sky Safari side, do not check the box that says "Set Time & Location" otherwise if it transmits these parameters, Argo Navis will reset its time and location which will invalidate any alignment you may have made.
Hi John,

Thanks for the question.

On the Argo Navis side, ensure for the serial port number you are interfaced to that in the MODE SETUP, SETUP SERIAL menu that the STARTUP command protocol is set to 'meade' and the BAUD rate is set to 9600.

Whenever changing the STARTUP setting, be sure to press EXIT or ENTER to escape the menu and save the setting to non-volatile memory.
Then power OFF the unit and power it back ON so the new STARTUP command starts.

On the SkySafari side, use a setting of Meade LX200 GOTO, not the PUSHTO setting. This is true even if you are using a non-GOTO mount.
In a 30 October 2019 press release from the Giant Magellan Telescope Observatory (GMTO), it has been announced :-

GMTO wrote:
Largest contract ever signed by GMTO for final design and construction of massive telescope structure

October 30, 2019 – PASADENA, Calif. – GMTO Corporation, the organization managing the development of the Giant Magellan Telescope (GMT) on behalf of its U.S. and international founders, has signed a contract with MT Mechatronics and Ingersoll Machine Tools to design, build and install the telescope’s precision steel structure. The GMT is a 24.5-meter (80-ft) diameter next-generation giant optical-infrared observatory that will explore the frontiers of astronomy, including seeking to answer one of humanity’s most pressing questions: “Are we alone?” The GMT will study the atmospheres of planets orbiting stars far from our solar system to search for signs of biochemistry.

MT Mechatronics of Mainz, Germany, and Rockford, Illinois-based Ingersoll Machine Tools, part of the Italian Camozzi Group, will design and manufacture the 1,800-ton precision mechanism, known as the “telescope structure” that will hold the GMT’s optics and smoothly track celestial targets as they move across the sky. The telescope structure will be designed by MT Mechatronics and manufactured, assembled and tested by Ingersoll before being shipped to, and installed at, the GMT observatory site high in the remote Chilean Andes.

The total value of the telescope structure contract is $135 million and will require nine years of effort by a large workforce of engineers, designers, metal workers and machinists. The contract was signed by MT Mechatronics Senior Vice President, Thomas Zimmerer, Ingersoll Machine Tools CEO, Chip Storie, and by GMTO president, Dr. Robert N. Shelton, and project manager, Dr. James Fanson.

“Manufacturing the telescope structure is one of the biggest steps we will take on our journey to building the Giant Magellan Telescope,” said Dr. Shelton, GMTO President.

“We selected MT Mechatronics and Ingersoll Machine Tools for their commitment to quality, extensive experience with astronomical telescopes and abilities to manufacture complex precision structures, following a two-year global competition,” added Dr. James Fanson, GMTO Project Manager.

The telescope structure will hold the GMT’s seven giant mirrors in place as they bring light from distant stars and galaxies to a focus so it can be analyzed by scientific instruments mounted deep inside the telescope. The mirrors, the largest in the world, are made at the University of Arizona’s Richard F. Caris Mirror Lab. When in operation, the telescope structure, complete with mirrors and instruments, will weigh 2,100 tons but will float on a film of oil just 50 microns (2 one-thousandths of an inch) thick – allowing it to move essentially without friction as it compensates for Earth’s rotation, tracking celestial bodies in their arc across the sky. With its unique design, the GMT will produce images that are 10 times sharper than those from the Hubble Space Telescope in the infrared region of the spectrum.

“Being a part of an endeavor with objectives as distinguished as the Giant Magellan Telescope’s is compelling for MT Mechatronics and we’re eager to support the GMT on its quest to answer the deepest questions in astronomy,” said Thomas Zimmerer, Senior Vice President, Business Development Sales & Marketing, Product Development, MT Mechatronics. “We look forward to collaborating with GMTO over the next decade to bring the telescope’s massive structure to fruition.”

“We are happy to work with GMTO and MTM to create this unique tool for the study of new worlds. The project honors and motivates all of us at Ingersoll,” said Lodovico Camozzi, CEO of Camozzi Group. “It will be a special day when the GMT’s telescope structure is completed and placed in service in Chile,” said Chip Storie, CEO of Ingersoll Machine Tools.

MT Mechatronics has over 50 years’ experience with telescopes, beginning with the Parkes Radio Telescope in Australia. It was part of a European consortium constructing the European Atacama Large Millimeter/submillimeter Array (ALMA) telescope antennas and was the mount designer for the Daniel K. Inouye Solar Telescope (DKIST) in Hawaii.

Since its inception in 1891, Ingersoll Machine Tools Inc. has been an iconic name in the milling machines sector, successfully serving the defense sector and then the newborn aeronautics and aerospace industry. Ingersoll has many decades of experience with manufacturing precision steel structures, including recently partnering with MT Mechatronics on the construction of the DKIST telescope mount.

The contract between GMTO, MT Mechatronics and Ingersoll Machine Tools will involve nine years of work and 1,300 tons of structural steel, and the structure is expected to be delivered to Chile at the end of 2025 and be ready to accept mirrors in 2028.

The mount contract completes another significant milestone for GMTO in 2019. In March, the excavations for the foundations of the telescope’s pier and enclosure were finished, and in July the second of GMT’s seven primary mirror segments was completed and shipped to temporary storage. Casting of the sixth primary mirror segment at the University of Arizona is expected to begin in mid-2020.


Press release here :-
Deep sky enthusiast, Barbara Wilson, who sadly passed away recently, described the visually challenging, 16th magnitude globular cluster Terzan 9, in Sagittarius, as follows :-

Originally Posted by Barbara Wilson wrote:
It is really there. The 11 mm Nagler did not quite pull it out of the background sky but the 9 mm did. Extremely weak object just at the plotted position. The cluster is very close (3') to a very elongated right triangle of 3 stars about 9-10th magnitude. Two of the three stars point to a faint star not plotted on MegaStar, of about 16th magnitude. The globular is just to the west of the faint star. The cluster itself appears visually larger that on the POSS print. The glow is maybe 1' in size. The cluster is just on the edge of a dark dust lane in the Milky Way as the CCD image shows.

Now astronomers using the Multi Unit Spectroscopic Explorer (MUSE) have been able to make observations of Terzan 9 to better understand its chemical composition.

Tomasz Nowakowski at Phys.org reports today :-

Originally Posted by Tomasz Nowakowski , Phys.org wrote:
Located only 2,280 light-years away from the galactic center, Terzan 9 is a very compact and moderately metal-poor globular cluster. Observations show that the cluster remains confined within about 3,260 light-years of the galactic center with an orbit co-rotating with the Milky Way's bar.

However, although many studies of Terzan 9 have been conducted to determine its fundamental properties, its chemical composition still remains poorly understood. In order to change this, a group of astronomers led by Heitor Ernandes of the University of São Paulo, Brazil, employed the MUSE instrument at ESO's Very Large Telescope (VLT) in Chile to conduct detailed observations of this cluster.

"Given its compactness, Terzan 9 was observed using the Multi Unit Spectroscopic Explorer at the Very Large Telescope. The extraction of spectra from several hundreds of individual stars allowed us to derive their radial velocities, metallicities, and [Mg/Fe]," the astronomers wrote in the paper.

In general, MUSE observations allowed the team to obtain spectra of over 600 stars. This sample was then reduced to 67 member stars of Terzan 9. As noted in the paper, the study resulted in measuring such properties of member stars as radial velocities, metallicities and magnesium-to-iron abundance ratio, which also gave mean values for the cluster.

When it comes to the chemical composition of Terzan 9, the observations found that it has a metallicity of approximately -1.1 and a magnesium-to-iron abundance ratio at a level of about 0.27. The metallicity is consistent with previous studies pointing out to a value between -2.0 and -0.99.

The mean heliocentric radial velocity of Terzan 9 was calculated to be 58.1 km/s, which is lower than the value from derived by a previous study based on six stars. However, the astronomers noted that both results are in agreement within uncertainties.

The researchers concluded that the results make Terzan 9 a moderately metal-poor blue horizontal branch cluster like HP 1, NGC 6558, and NGC 6522. Moreover, the magnesium-to-iron abundance ratio suggest that the stars in this cluster were formed from gas resulting from an early fast chemical enrichment by core-collapse supernovae.

Full story here :-

Paper published at arXiv 22 Oct 2019, "A MUSE study of the inner bulge globular cluster Terzan 9: a fossil record in the Galaxy" by H. Ernandes et. al. PDF (free) :-
Nick20LUN wrote:Thanks Gary looking forward to taking part

Thanks Nick!

Welcome to the Group and we look forward to your participation. smilie
This Argo Navis User Catalog of all planetary nebulae with Abell designations was originally kindly
compiled and posted by Owen Brazell.

A highly experienced observer with many decades of experience, Owen is the author of the book "Planetary Nebulae: An In-Depth Guide to their Physics and Observation"
This list of 111 objects suitable for observing under light-polluted skies originally appeared in Sky & Telescope
and was originally uploaded to the Argo Navis Yahoo Group by user jpr1608
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