Sampling the Skies in Ireland with a 5.1 inch Newtonian.

Plotina: the author’s 130mm f/5 travel Newtonian enjoying the skies over Cork Habour, Cobh, County Cork, Ireland.

 

July 9 through 21, 2018

It could have been altogether very different.

Having access to a suite of small, portable instruments, like a fine 90mm ED refractor, a first-rate 80mm f/11 achromat, an ETX 90 and a 90mm f/10 achromat, I’m so glad I threw tradition to the wayside and brought along my 130mm f/5 Newtonian telescope on my recent trip to Ireland. As described exhaustively in several previous blogs, the latter instrument is a superior grab ‘n’ go telescope to all of the above instruments on all targets; whether in the Solar System or far beyond. Its mirrors efficiently bring light to a sharp focus and with a relatively small central obstruction (27 per cent), it behaves more like a 5 inch refractor than anything else. Yet it is very lightweight, easy to collimate accurately and, as demonstrated previously, delivers excellent images of planets, the Moon and very tight double stars down to 0.94 seconds of arc: the absolute limit imposed by its 130mm aperture. And, as will be described shortly, it’s not too shabby as a rich field/deep sky instrument either.

These findings were all  previously established in many parts of the Scottish mainland and even on some of the Western Isles, but I was especially keen to see how the telescope would fare at no less than five locations in Munster, the southern-most province of the Irish Republic. I have very fond memories from youth using much smaller instruments, but the 130mm Newtonian promised to reveal much more.

The Journey

The telescope was carried in a sturdy aluminium case in the boot of my car from my home in central Scotland down to southern Scotand, and then by ferry across to Northern Ireland, and from there, southwards to the Republic; a day’s trip.

Upon arrival, the telescope was found to be very slightly out of collimation but a laser collimator made light work of tweaking the optics in a matter of seconds.

Locations tested:

Limerick City: Ballinacurra in the southwest of the city & Caherdavin, a few miles away on the other side of the great River Shannon, in the northwest of the city.

Cobh, County Cork.

Sixmilebridge, County Clare.

Newport, County Tipperary.

 

Conditions: Over ten days, only two nights turned out cloudy, the rest being either fully clear or partially clear. At all locations, true darkness occurred around local midnight, remaining so for about two hours. In general, all observations were conducted on grass, as this was established to be the best surface upon which astronomical observations should be made.

Eyepieces used: Just two oculars were chosen for the trip; a Celestron X-Cel 25mm, delivering a power of 26x in a 2.3 degree true field, and a Meade Series 5000 5.5mm ultra wide angle, serving up a power of 118x in a 0.7 degree true field. Additional powers of 59x and 266x could be pressed into service by attaching a Baader 2.25x Baader shorty Barlow to the 25mm and 5.5mm eyepieces, respectively.

Telescope mounting: The 130mm f/5 is a perfect match for the Vixen Porta II Alt-azimuth mount, which travelled with me along with the telescope. High magnification targets were tracked with ease using the in-built slow motion controls.

Results on the Planets: Planetary views of Jupiter and Venus were conducted earlier in the evening. Mars was not viewed owing to its very late culmination well into the wee small hours of the morning.  The extra 4 degrees of elevation in the sky owing to the sites’ lower northerly latitude (centred around 52 degrees north), proved significant; Jupiter showed a wealth of detail using the 5.5mm Meade ultrawide angle ocular delivering 118x. Much dark banding and subtle colour differences within the bright zones could be discerned. The North Equatorial Belt (NEB) was very prominent throughout all the vigils, being noticeably darker and more disturbed morphologically than its southern counterpart. On one evening, I was able to accurately establish the CM II longitude of the Great Red Spot and the finest images of Jupiter were afforded at Newport, County Tipperary, with the telescope set up on tarmac owing to a lack of a suitable grassy surface, but the relatively high elevation of the shorttube 130mm reflector astride the Viven Porta II above the surface proved an effective dampener of thermals, even though the same day and evening were hot and sunny.

Venus showed its pretty, early gibbous phase at 118x in the telescope, despite its very low altitude at the times of observation. Some atmospheric refraction yielded some false colour but this was expected and largely unavoidable.

The Moon:

On Thursday, July 19, I shared some magical moments with my elder brother, who lives in Newport, County Tipperary. Around sunset, I set the instrument on the tarmac ouside his house and aimed it at a late crescent Moon. The view in the 5.5mm Meade delivering 118x was amazing; my brother being deeply impressed at seeing the entire lunar regolith  in razor-sharp detail, floating through the huge portal hole. At first he couldn’t help but hold the eyepiece (a natural newbie reaction), but as soon as I taught him to let go, he just relaxed and let the telescope do the work. I could tell that he was quite taken aback with this strange little telescope, where you peer through its side rather than directly along the tube. With a few minutes training, he learned how to use the slow motion controls to bring Luna back into the centre of the field.

 Double Stars:

Test double stars examined included:

Epsilon Bootis ( Izar)

Delta Cygni

Epsilon 1 & 2 Lyrae

Pi Aquilae

Such systems were chosen for their sensitivity to ambient seeing conditions and ease of location, even from an urban/suburban setting.

Results: At every location examined, the results proved very much the same: all systems were beautifully resolved at 266x, the companions being perfectly picked off from their respective primaries. One location proved to be windy (overlooking Cork Harbour in Cobh), but this turned out to be largely inconsequential to the observations made. Once the wind died down, the companions yielded easily.

 

Deep Sky Observations:

General appearance of the sky after sunset, as witnessed on a few evenings during the vacation. Such cloud formations augur good, stable summer air.

 

Naked Eye: I immediately noticed the lower elevation of the Pole Star than at home.

I recorded three bright fireball-like meteors streaking across the sky (2 on one evening, the other on a subsequent evening)  from the direction of Cassiopeia/Perseus. These were possibly early Perseid meteors, which will culminate around the middle of August.

Even from a suburban location (Caherdavin), the sky got dark enough to easily see magnitude +4.6, Iota Cassiopeiae, low in the northeast, which was not possible from my Scottish vantage owing to the encroach of twilight. From the same location, I was able to trace out the more prominent parts of the Northern Milky Way streaming through Cygnus and Cassiopeia.

The darkest skies were experienced at Cobh, which is not too surprising, but there was still a significant amount of light pollution from the adjacent harbour to the southwest of my viewing location. Still, magnitude +5.8 Messier 13 could not be seen owing to this light pollution despite its high elevation in the southwest at the times of observation.

Telescopic Impressions:

The 5.1 inch reflector set up for an observing session at Sixmilebridge, County Clare.

The 25mm Celestron X-Cel LX eyepiece proved very satisfactory with the 130mm f/5 reflector, delivering sharp, high-contrast images of star fields nearly all the way to the edge of its 2.3 degree field. I enjoyed studying the stellar hinterlands of bright stars within Cygnus, particularly Sadr and Deneb, the truly dark skies pulling out a wealth of fainter stars frankly invisible in the twilight of Scotland.

M39 in northern Cygnus was pariticularly captivating in the 25mm wide field eyepiece at Caherdavin; a rich smattering of approximately three dozen suns of the 7th magnitude of glory and fainter, arranged in a neat triangular space approximately 30′ in size. The Barlowed view with the same eyepiece at 59X was much more immersive though. M29 was dull in comparison; small wonder my guide book has nothing to say about it lol!

The 5.5mm Meade ocular was by far my most used ocular during the trip. Having become somewhat disillusioned by high-quality, small field of view oculars, such as the Vixen HR series, with their measly 40 degree fields, I very much appreciated the vastly more expansive (yet very well corrected) fields afforded by this 82 degree ocular. Such short focal length, wide-angle eyepieces are a godsend to those who enjoy manually tracking tight doubles. They are visible for longer, allowing the observer much more time to examine their morphology before having to nudge the telescope along.

The 5.5mm served up excellent, immersive views of showpiece summer deep sky objects such as M13, M92 and M57, the 118x power really helping to darken the sky. The view of M13, in particular, was most impressive, even from suburban locations, comparing very nicely with my 5″ f/12 refractor from my recollections. The outer part of the globular was well resolved with dozens of stars seen directly or by using averted vision.

The same eyepiece is especially good at observing wide ‘binocular’ doubles such as Albireo, 61 Cygni, Gamma Delphini, Beta Lyrae and the incomparable 31 (Omicron) Cygni, all of which were enjoyed with the telescope at most of the sites visited.

At 23:30 UT on the evening of July 16, I aimed the telescope from suburban Limerick (Caherdavin) at Iota Cassiopeiae, then located just above the tree line of the garden. To my sheer delight, I was able to clearly see the three components of this trple system using the Meade ocular at 118x. This was a particularly impressive observation, owing to the fairly low power employed but also because of its low elevation at this site. This is a powerful testimony to the excellent stability of Irish suburban skies.

I enjoyed some special time exploring the rich treasures of the far northern constellation of Cepheus on the evening of July 16, which is drowned out by twilight in Scotland. Delta Cephei was very captivating at 118x. The primary is an old, yellow pulsating Cepheid variable( the prototype of this stellar class) with a gorgeous blue companion; a near twin of the more famous Albireo. Xi Cephei  presented beautifuly also; its blue white and yellow suns well resolved at 118x. Omicron Cephei was also briefly visited; easily resolved at 118x but better seen at 266x; its magnitude +4.9 ochre primary and much fainter (magnitude +7.3) steely grey companion being readily observed. Then, there is the incomparable Mu Cephei, an enormous red giant star, its deep sanguine hue standing out like a sore thumb against a good, dark sky was a sight for sore eyes. Mu is comely at low or high power in the 130mm reflector.

Don’t forget Saturn!

Almost forgot!

Though it was past their bedtime, I showed my boys the planet Saturn for the very first time, located well east of Jupiter and only becoming visible to the naked eye very late in the evening. Being even lower in the sky than brilliant Jove, the telescope still did a mighty good job at 118x showing them the mottled globe of the planet, with its beautiful, icy-white ring system, the Cassini Division being easily dicsernible at a glance. The view at 266x was not so good though; a simple consequence of the blurring effect of the Earth’s atmosphere at this low altitude. Still, I showed off Saturn to friends and family where ever possible. Of all the celestial objects studied, it was the Ringed Planet that received the most oohs and aaws!

Concluding Thoughts

The experience of a truly dark sky in mid-July was a joyous event for me; accustomed as I am to ferreting out things to see in twilight at home in Scotland. The small Newtonian proved to be the perfect travelling companion, its generous aperture, light weight and easy set-up all helped to make the trip memorable and worthwhile. In many ways, Ireland is a transformed nation now (it would be naive not to think so); sadly, it has sleepwalked its way into the pernicious mire of secularism, with all its attendant depravities. But at least the skies overhead are still good to go, a comforting reminder of God’s incomparable glory and omniprescence. Though I would like to have visited a site completely devoid of light pollution it was not to be on this occasion, yet conditions were near ideal during these eight days of observations (especially for high-resolution, double star work), but surely many more such evenings occur on the Emerald Isle?

And I’d do it all again in a heartbeat!

 

Neil English is author of a large and ambitious work; Chronicling the Golden Age of Astronomy, due out later in 2018.

 

 

De Fideli.

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