Aperture Fever - best avoided.

I blame star-parties for this affliction. TheBaker Street IrregularAstronomers meet each month in Regent’s Park to stare up at low cloud cover or light-polluted skies. No, that’s not fair comment; clear skies do present themselves in which a surprising amount of celestial objects are observable, bringing delight to all who attend the star-party.

I first attended the Hub, the BSIA’s meeting spot in the park, in the Autumn of 2010 soon after the group was established. Without a telescope, just a remembered boyhood love of astronomy instilled by Patrick Moore’s commentaries on the Apollo missions, I pitched up to an early meeting. Soon I was fascinated with the various telescope types members had brought along and the varied views each ‘scope provided. I remember particularly being shown by one of the founders of BSIA my first view of the double star, Albireo, now my favourite binary (thanks Ralph). As a gemmologist who looks at gem colour for a living, I observed a beautiful image of turquoise blue and topaz yellow through the eyepiece. The eyepiece was at the end of a William Optics GT-81. I succumbed to the first symptom of fever: I HAD to buy this telescope!

William Optics GT-81

This refractor was manufactured by William Optics, for some reason, as a limited run of 100: a ‘limited edition’.  I managed to secure number 35 (as attested on the base plate of the focuser) when spending time in the Canaries. On the island I mount it on an HEQ5Pro to enjoy the exceptional skies above the cloud level. 

During first set-up on the HEQ5Pro before ascent to 2300m

Easily transportable in its well designed back-pack, the OTA makes regular appearances at the Hub and the Cwmdu AstroCamp aboard a light, manual alt-az mount, a Sky-Watcher AZ4. This combination of scope and tripod is perfect for quick grab’n’go observing in central London: at the Hub I can set-up in minutes and be observing and showing observing targets to others while other star-gazers are still star aligning and perhaps cursing at their GOTO computers.

Set up  on the AZ4 at the Hub before night falls.

But that aperture fever takes hold of a weak soul. Soon or later one yearns for a something better, bigger and more expensive. There is no antidote: one simply MUST buy something else. Being in close contact at star-parties with other ‘scopes is, of course, the reason why this fever spreads indiscriminately, affecting young and old, the tyro and the ‘old hand’. At one Hub meeting when we were enjoyed exceptional skies a fellow Irregular showed me the double cluster  through his APM refractor (thanks Mathew). It reminded me of two groups of diamond melee scattered on a black gem cloth! So beautiful and all from light polluted Central London skies. I HAD to buy an APM refractor!

After my disappointment with the performance of the Crawford focuser on the GT-81 forcing me to replace it with a WO rack & pinion I vowed my next ‘scope shall have the well respected Feather Touch focuser. I love the optics of the GT-81 but its original focuser did let the scope down and I notice the latest WO scopes have R&P focusers as standard. APM provides the option for a Feather Touch focuser. And now I have learnt about the Russian glass used for the optics in many APM scopes.  This glass is considered by many users to be better than the Japanese glass found in most apo-refractors.

APM Apo-refractor

So the decision has been made: not by my cool head but by the aperture fever burning within. I shall order an APM 100mm apo-refractor. The WO GT-81 will be my UK scope and the APM my Canaries scope. And damn the expense!

A New Addition to the Eyepiece Stable

When I purchased the GT-81 refractor in 2011 the retailer suggested and provided two Vixen NLV eyepieces; a 20mm and 6mm. A Celestron 2x Barlow lens was thrown also into deal. Being short sighted I wear spectacles so eye relief is an important consideration when selecting eyepieces.  The 20mm of eye relief the Vixens provide is sufficient for me to observe comfortably wearing glasses.

Normally I use the 20mm eyepiece, having the lower ( x24) magnification for observing those deep sky objects (DSO) I'm interested in, particularly star clusters. For binary star observations I start at low magnification then swap to the 6mm (x80) for splitting multiples with small separations.

Whenever I wish to engage in planetary work I make use the 6mm and the Barlow to observe and recently have enjoyed seeing Jupiter's Galilean moons displayed through Central London's skies and during occasional brief periods of good seeing observing transits and the GRS on Jove.

For lunar viewing I screw in a variable polarising filter into the thread of the 6mm and pop it into the x2 Barlow for excellent views of the Moon - I have a current fondness for the various features of Mare Imbrium.

This month (2013 Feb) I've decided to plug a gap in my eyepiece range and add one with a wider field of view than the 45 deg of the 6mm and the 50 deg of the 20mm Vixens. Researching suitable eyepieces with sufficient eye-relief I was attracted to the TeleVue range and in particular the 17 mm ER offered by the Nagler4 12mm.

I took one on trial from my local supplier, Widescreen Centre, to put it through its paces. It’s a bit of a beast: approx three times as heavy as my little Vixens and stands much taller on the GT-81. Initial concerns whether my 'scope or my grab'n'go mount I use in Central London, the light but sturdy Skywatcher AZ4, couldn't take the EP's weight were allayed quickly. Viewing the waning gibbous Moon on the first trial night provided the best lunar experience I've ever had. Tiny craters and rilles, slightly difficult to discern with the Vixen, shot out at me with pin-sharp clarity. The field of view of course is immense with no apparent fall off at the edge in sharpness of the star field surrounding the Moon.

I will be keeping the Nagler and look forward to using it on a regular basis.

Asteroid 2012 DA14

I suggested the Baker Street Irregular Astronomers do something about the asteroid. That is have a bash at seeing it at a meeting. Our normal meeting spot at the Hub in Regent's Park wasn't playing ball so it was arranged the group shall meet in a school playground in Northolt to await the rock's appearence.

News was still abuzzing about the Russian event earlier in the day as I loaded the GT-81 into the ZipCar and joined the delightful traffic crawl along the A40. Earlier I had invested twenty odd pounds on the upgrade to SkySafari 3, my iPhone app. The upgrade has the asteroid data so I could track the Alt and Az co-ordinates of the speeding rock. Dialing this info on my setting circles of my AZ4 mount would be crucial for me to spot the aseroid with my GT-81.

Arriving at the school I was greeted by clouds - lots of them which hardly parted all evening. No 2012 DA14 sighting for me. The closest I came to seeing it was when the clouds parted for a brief moment so I could see a few stars in the field of view. I'd like to think one of those points of light was the asteroid but the clouds closed in too quickly so no tracking was possible. Did I really see it? I doubt it.

Photo by Guy Wells

In this photo my GT-81 points to the position where the asteroid is hiding behind London cloud. On the right I'm being interviewed by two chaps from the press interested in our merry band of amateurs.

During the evening there was lots of chatting to old and new members of BSIA and much forlorn viewing of the cloud cover. We did get to see a little of the Moon and Jupiter htrough the cloud gaps but conditions were so unfavourable to observing we cheered when a star, any star, made a fleeting appearence! All-in-all a rather a disappointing evening.

My thanks go to Paul Hill of BSIA for organising the evening at the school.