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Southern Cross - Sep 2003

• COTM: Corona Australis By Ross Gould.
• MARS ON 27 AUGUST 2003 – WERE YOU THERE? BY Karen Brown
• The new Meade LX200 12inch GPS Part 1 By Mike Sidonio
• AQUILA Jenni Kay FRAS

COTM: Corona Australis

Ross Gould

Corona Australis is tucked into a little corner of the sky beside Scorpius, with Sagittarius adjacent. The little circlet of its brighter stars is readily noticed. The Milky Way runs through it, so objects for observing are those from our galaxy, with other galaxies greatly obscured.

It contains a fine globular Cluster, NGC 6541, the interesting nebular region NGC 6726-7-9, and a number of good double stars. Descriptions below are with a 7” refractor except when otherwise indicated.

Clusters

NGC 6541 (18 08.1, -43 43). A beautiful field that includes the fine bright partly resolved globular cluster NGC 6541. My old 6-inch Newtonian showed some resolution into stars, and the 7” refractor shows more. The double star HJ5014 is NW of the cluster, and can be included in the same low power field.

NGC 6496 is a small globular, rather faint and without resolution in the 7”. It is on the border with Scorpius. Those who like globulars will prefer 6541; those who like faint fuzzies will enjoy finding this one.

Nebulae

NGC 6726-7-9 (1901.7,-3653). The position is for the double nebula 6726-7. On the northern border of CrA is this region of several nebulous spots. A bonus in the field, as the DSS image shows, is the globular cluster NGC 6723 nearby (across the Sagittarius border).

NGC 6729 is a variable, comet-like nebula, similar to Hubble’s nebula NGC 2261 in Monoceros. Each has an embedded variable star. This is an interesting field both visually and for imaging.

IC 1297 (1917.4, -3937). I haven’t seen this small but moderately bright planetary nebula, which Hartung says is visible with 15cm.

Double Stars

Despite being in the Milky Way, CrA isn’t over-supplied with bright pairs. However some of these are fine objects. The best of them is probably Gamma CrA (19064-3704). This is a 120 year binary, which has been in the closer part of its orbit in recent years. At present it is fairly tight at 1.3” in PA 042 (NE). The PA has been changing rapidly in recent years – ten years ago it was 090. It was wider and easier when Hartung observed it, at nearly twice the current separation. I also found it a fairly easy pair in the 1960s, visible in a 6” Newtonian at 100x. More recently higher magnification is needed, and the 7” refractor needed 180x for a clean separation, though the star was obviously not single at 100x. The pair is pale yellow and of even brightness. A fine object.

HJ 5014 (18068-4325). The pair of m5.7 stars at 1.7” (1999) is just split at 100x; at 180x it’s a beautiful even yellow pair nicely apart. This has long been a favourite of mine, helped by the presence of NGC 6541 in the field.

Kappa CrA (18334-3844). At 100x: wide easy bright white pair in a field lacking other bright stars. In an 8x50 finder a tiny pair, just split.

HJ 5028 (1812.1-3920) An easy attractive pair, with the brighter star a fairly close double (BU 759). The effect is better at 135x, which makes the closer pair easy. It is at one corner of a triangle (the other stars m8 and 10), in a pleasantly starry field. The main star is mag. 8.8: the closer companion m9.2 at 2.0”, the wider companion mag. 9.4 at 14.8” (1991 measures).

COO 227 (18438-3819) 1981 214 29.2 5.13 9.7 A2Vn. This is Lambda CrA: a bright cream-white star has an obvious wide companion, of dull yellow tone; the field is fairly starry.

BSO 14 (19011-3704) is a bright (mags 6.3, 6,6) well separated (12.8”) even pair, both white; a good object in a not very starry field. The globular cluster NGC 6723 is NW in a large field; and the nebulae NGC 6726-7-9.

Galaxies?

Not many here, and most of them very, very faint. Try NGC 6768 (1916.5, -4013), an elliptical galaxy with a smaller fainter companion.

MARS ON 27 AUGUST 2003 – WERE YOU THERE?

Karen Brown

It was arranged by the Planetary Sciences Institute, with participants from the Institute, the Research Schools of Earth Sciences, and Astronomy and Astrophysics, and from CAS. The CAS astronomers arrived and set up their telescopes, and the MSO astronomers, Vince Ford and Heath Jones, and the other scientists, positioned themselves in the lecture theatre. Outside, there were 18 scopes ranging in size from Joe Hattley’s lovely 3” refractor to the wonderful Bobroff 20”, and they were joined by John Morland’s tripod-mounted binoculars. The 19 brave men and women, and their band of hardy assistants prepared to face the hordes. And the hordes came, not in a clean frontal assault, but from all directions, recklessly forming cues wherever they encountered a telescope. The Morland binoculars, strategically positioned between two fairly long queues, effectively alleviated the frustration of some horde members waiting in line.

It is estimated that around 4000 members of the public cycled through the lecture theatre and our small patch of floodlit space in the grounds of the ANU. Unfortunately, due to security requirements, all of the lights in Union Square were blazing on that fateful night, including the ground-level ones, which only added to the challenge. A couple of our members managed to wrap the closest lights in some red cellophane, which lessened the glare a little. Fortunately, Mars was pretty bright, and the sky was clear. Of course, as the evening progressed, and Mars climbed higher above the trees, buildings and light haze, it became easier to see.

There were so many people that the MSO talk was presented three times, each for an audience of around 850 – there was no rest for the volunteers, and some didn’t have dinner until they got home and unpacked after midnight. Those of you who heard it on the ABC will know that the crowds coming to the Mars event that night grid-locked Civic for around twenty minutes.

So, what did we see? In every scope I looked through (all but the Bobroff, which had a queue of around 200 all night) the polar cap was clearly visible and, in some, I thought could vaguely see other features. The visitors were all looking for the polar caps, having heard about it from others, and were excited to see it. The quality of image was fairly consistent among the scopes, and of high quality, light pollution notwithstanding. However, the viewing public had it firmly in their minds that the 20” must offer the best view, and it was taking around two hours to move from the end to the top of that queue. Many were persuaded to try other scopes, but a couple of people refused to be turned aside and only ended up seeing one view of Mars all night! For some reason they had trouble believing that the view through a 3” (Hattley) or 6” (Kennedy) refractor would reveal pretty well as satisfying a sight. I can only conjecture about this – I had a wonderful view through both refractors and most of the reflectors – the Rawlings C8, Higgins 10” Meade with filters, Nelmes 4”, being notable inclusions, to name only a few – but did not make it to the Bobroff ladder. Peter and Judy didn’t get away until well after midnight, and must have needed about three days sleep to recover.

It was a marathon effort from all who came along to help. Neither telescope operators nor scientists had a break, but the public loved it. It was a great opportunity to promote astronomy, the Floriade nights, the Society, and to recruit new members. In fact, all of the membership applications were handed out, as they were at our last public night in Weston Park, where we had around 150 visitors. Mars is such a drawcard, so close, and yet so far; so mysterious yet so like Earth – the stuff of dreams and fantasies. It was tiring and relentless, but I wouldn’t have missed it and I’m glad I didn’t.

The new Meade LX200 12inch GPS w UHTC coatings
Shear astronomical brilliance or an unnecessary luxury?
Part 1

Mike Sidonio

At this years Canberra Astronomical Society (CAS) Annual Dinner I was approached by Celestron and Starfire disciple and double star extraordinaire Mr Ross Gould who asked me to do a review of my now one-year-old telescope, the mysterious Meade LX200 12”GPS. Unfortunately I sense that, at least locally, there seems to be somewhat of a contemptuous anti-Meade sentiment. I suspect that this contempt shown for Meade and in fact computerised GOTO technology in general, is based on tired age-old views held from the past that are simply not relevant today. I can remember not really taking CCD imaging seriously a few short years ago because I was a staunch film astrophotographer. A few weeks ago I bought my first CCD camera ?

The following, while perhaps colourful at times, is basically an informal and hopefully an attempt at an unbiased and accurate assessment of this scope after a highly successful and amazing year of operation – see, can’t sense any bias can ya? ?

The LX200GPS range of telescopes is Meade’s latest production of their flagship Schmidt-Cassegrain line of fully automatic computerised “GOTO” telescopes. The current line went on sale, albeit somewhat delayed, in January 2002 to answer the new Celestron 11-inch GPS Schmidt-Cassegrain that was successfully released the previous year by Celestron Int. The new Meade line has also upgraded its highly successful predecessor the LX200 “classic” line of telescopes that was first released more than 10 years ago.
My new LX200GPS arrived undamaged from Adelaide Optical Centre on 27 June 2002.

I took the afternoon off work when I got the courier’s phone call to meet him at my home in Ngunnawal ACT. I was understandably excited at the prospect of taking possession of such a telescope. Having read widely about the various options available to me in my quest to once again own a telescope and having hopefully dealt with my jealous eagerness to own a telescope that was at least as good as Michael Nelmes’ wonderful new C14, I was well and truly ready to lay eyes on this new technological marvel. Although I had worked extensively with the C14 and 16” IK6 at the Canberra Observatory, I had not actually owned a telescope since 1987 when I sold my 8” F7 Newtonian on a Samson German Equatorial mount circa 1982 to fund the construction of a still-to-be-completed dream telescope with my still good friend and astro-buddy Attila Horvath.

Now for the telescope review:
The LX200 12”GPS scope is a Schmidt-Cassegrain Telescope (SCT) or more precisely a Catadioptric reflector telescope of the Schmidt-Cassegrain optical design, meaning there is a combination of a lens or corrector plate as well as mirrors in the optical train. The front corrector plate has a clear aperture of 305 mm or 12 inches, and as the subject of many back and forth tit-for-tat advertising wars between Meade and Celestron has told us over the years, and for reasons I won’t go into here, the main mirror is slightly bigger than this. The effective focal length is 3050 mm giving a focal ratio of F/10. Notable accessories that come with the scope as standard are a superbly stable Giant Field Tripod, a useful electronic Crayford-style micro-focuser, a mirror locking knob and 26 mm Plossl eyepiece. The mirror locking system allows the notorious SCT mirror flop, or tendency of the mirror to move when the scope changes positions, to be effectively eliminated – a must for CCD imagers and really accurate pointing.

[I would like to take this opportunity to thank Attila Horvath for, among other things, kindly lending me his excellent range of late-80’s Televue plusses and complete range of Meade Super Plusses to use with this scope ?]

The first thing that was evident to me when I unpacked and assembled the new scope was the size of this beast. Listed as 73 lbs by Meade, this is the raw weight of the optical tube assembly (OTA) plus fork arms, which are all one piece. However once you add some tube balance weights, permanently attach a Kendrick dew remover control box and heater strips and perhaps a piggyback camera adapter, you are looking at about 80 lbs or 36 kg, and given its overall size and bulk, your average pencil-neck astronomer would not consider this scope very portable. Although, when mounting the scope in the Altitude/Azimuth (Alt/Az) operational configuration and utilising the integrated carry handles on the fork arms, it is not too bad, and most able -bodied men and many women should be capable of setting this beauty up without too much effort.

The same cannot be said, however, when mounting the scope onto the optional equatorial Superwedge (available from Meade) when mounted on the standard issue Giant Field Tripod. In this case the user is required to lift the scope up high enough and then to hold on to its 80 lb bulk while guiding a bolt into a slot on top of the Superwedge. Given my background in truck pulling, stone lifting and car rolling as a competitive strongman, I of course don’t have much trouble, but in equatorial mode this telescope is likely to be beyond the realistic set-up capabilities of the average person.

Hmm?..Tired of looking at the same old objects over and over again or frustratingly searching for those elusive faint galaxies? Then join the GOTO revolution and start observing!

Probably the most significant difference between this scope and other more traditional amateur telescopes is its incredibly powerful ability to automatically slew to any object in the sky with remarkable accuracy no matter how faint or obscure that object may be. This practice is normally referred to as doing a “GOTO.”
A GOTO can be done by simply selecting one of the thousands of objects already in the telescopes database or by entering the appropriate RA & Dec via the hand control box, it’s that simple! This attribute is in my opinion the most amazing ability imaginable in the world of amateur observing and truly makes observing a pleasure. I still have to pinch myself sometimes to see if it is real ?

Autostar II
Autostar II is the name given to the latest version of the command and control software centre or brains of the LX200GPS range of telescopes. Unlike its predecessor, the LX200 Classic, the main control CPU’s of the GPS model are located in the telescope drive base rather than in the handbox, making the new, easy to use and small lightweight hand box simply a keyboard to access the scope’s powerful features. Autostar II contains a plethora of telescope databases, functions and utilities to improve or alter the performance parameters of the scope. Some of these features include: the ability to compensate for gear backlash and worm gear periodic error on both axes, change the guide rate, set mount upper and lower slew limits and custom tracking rates as well as fully automatic guided tours of everything from Messier objects, planetary nebulas and galaxy clusters, or even the best objects to view for that evening. There is even a park facility, which when activated at the end of the evening of viewing, slews the scope to the “home” position so the next time the scope is fired up and gets a GPS fix, bingo! it is already aligned and ready to start pointing to whatever you like. Autostar also contains huge databases of stars, galaxies, nebulas, constellations, galaxy clusters, comets, asteroids and even man-made satellites, all of which are only a button press or two away from viewing! There are many other functions available but they are too numerous to mention them all here.

What does the GPS bit stand for?

The main difference between this scope and past GOTO scopes is the inclusion of the GPS receiver. Essentially the GPS facility simply allows the scope to find its position on Earth along with the current time, all by itself, by listening in to and then locking onto the GPS system of satellites. Using this information and along with limited user input, the scope is able to align itself with remarkable accuracy.

Getting it all aligned and pointing accurately

The accuracy of a computerised telescope’s pointing is an attractive and important quality, and as a result has been at the heart of competitive advertising between the major manufacturers. Meade claims that their LX200GPS range of scopes has “…..a pointing precision of 2 arcmin” while in “High Precision” mode Meade claims the pointing precision is improved to 1 arcmin or better. Exactly what “….a pointing precision of 2 arcmin” actually means seems to me to be a little unclear however.

[I have noticed that in recent times Meade has started to add the suffix “(approx)” after referring to the LX200GPS pointing accuracy but strangely not always…?]

In order to be able to point to anything in the first place, with any kind of accuracy, the scope must first be properly aligned. For this, Autostar II provides the user with several scope alignment modes to choose from including “Automatic” “Easy” “One Star” and “Two Star” alignment modes. Only available when the telescope is set up in Alt/Az mode, the Automatic alignment sequence is intended for those users who might not have the required knowledge of the sky necessary for initial alignment, and it is therefore fully automatic, meaning the scope does it all by itself. It is also the automatic mode in which the GPS feature is most useful.

The Meade GPS alignment dance (“….amazing what technology can do these days huh darlin’ ?” – Mr & Mrs Average).

After setting up the tripod eyeball level, mounting the scope and switching it on, the scope via commands from Autostar gets a GPS fix, and then in an amazing mechanical 60’s disco dance style, proceeds to find the slew limits of the mount, magnetic north, then true north and points to three compass positions where it slews up and down in Dec each time. By doing this last dance step, Autostar, by using a ball-bearing level switch in one of the fork arms, is able to establish the tip and tilt of the mount, to determine how level the scope base is in order to establish a horizontal frame of reference. Amazingly, after doing all this, Autostar II now knows – where it is on Earth, the GPS time, where true north is and how level the scope is! So armed with all this self-collected data the scope proceeds to point towards the first alignment star for final centring! Once the user has centred this star and pressed enter, Autostar slews the scope to a second alignment star and asks you to centre this too. Abracadabra! The scope is now aligned well enough to have every object it is commanded to point at, finish within the field of almost any eyepiece, all night! Simply incredible when you think it pretty much did all this by itself!

Apart from inherent mechanical and optical misalign-ments, the accuracy of the resulting pointing is somewhat dependant on how accurately you centred the alignment stars, and indeed can even be affected by the particular pair of alignment stars chosen by Autostar. So because of this the two star alignment mode is the one I have found myself using most frequently because during automatic alignment Autostar can sometimes pick less than optimal alignment stars that can result in less than perfect GOTO’s or stars that might be behind a tree or something. Although the GPS fix is still initiated, “two star” align-ment however requires the user to first manually position and level the scope and then choose the two alignment stars from Autostars extensive data base of alignment stars. The more accurately you level the scope and the closer you put the scope to the true “home” position initially, the closer Autostar will point to the alignment stars. Of course, if you know which star it is that Autostar wants you to centre, it doesn’t really matter if it was a bit off, as long as you centre it, then no problem.

In polar mode the alignment routines are a bit different. In this mode, pointing to Sigma Octantis and making wedge adjustments, followed by the centring of an alignment star chosen by Autostar, is required. Although Autostar II does an adequate job, in polar mode I have found that the only way to get really accurate GOTO’s is to take the time to accurately polar-align the scope. Once accurately polar-aligned it has been my experience that the pointing accuracy is more consistent than in Alt/Az mode.

Pointing accuracy

In a nutshell and by my calculations, in polar mode the GOTO pointing precision of my scope is good enough to land about 2/3 of all objects within about 3 arcmin of field centre!
Well, so what? What exactly does this mean? OK, lets see. If you insert a standard 10 mm Plossl eyepiece in the scope to give an effective magnification of over 300X and an actual field of view of 10 arcmin, then approximately 66% of all objects you ask the telescope to point to will land within the middle 2/3 of the eyepiece field of view! Not too bad huh? Due mostly to residual optical and mechanical misalignments, the remaining 1/3 of all-sky GOTO’s will still land the object at least somewhere within the field of view of the 10 mm Plossl or to within about 5 arcmin of field centre.

However, if 3 arcmin RMS pointing accuracy is still not good enough for you, then there is also a “High Precision Pointing” mode that further improves the pointing accuracy. When this mode is enabled and you initiate a GOTO, Autostar II automatically first slews the scope to a relatively bright star near the object you wish to point at and prompts you to centre it. You centre this star and press enter and the scope now immediately slews the couple of degrees or so to the target object, usually landing it within 1 arcmin of field centre or better! I have found this feature is particularly useful when I am looking for very faint objects like galaxies or faint globular clusters, because I know that after requesting the telescope to point at the desired object it will be right in the middle of the eyepiece! – a good starting point in the visual detection process. High Precision Pointing also allows for the imaging of faint objects beyond visual limits because you know the object will be right there smack in the middle of your CCD chip or film frame when you can’t see it visually, even if the scope has come from pointing at something on the other side of the sky!

It perhaps puts things in perspective when you think that the level of pointing accuracy currently available to amateur astronomers in a moderately-priced production line telescope today was only possible with custom-built multi-million dollar professional telescopes as little as a generation ago!

[At the time of writing, Meade will be launching its new range of LX200GPS scopes with a Smart Mount Technology or “SMT” package. This package will include, among other things, a T-Point type software application to allow Autostar II to further improve scope pointing! ]

Wired to the WWW

One of the major attractions this scope has is the ability to be able to update the telescope firmware, add new software features or manipulate the scopes internal databases, all via the Internet. By simply connecting the scope to a computer via an interface cable and accessing Meade’s web site, software updates can be downloaded into the scope, as can updated comet, asteroid and satellite orbital elements, as well as new guided tours.

AQUILA