A Magical Evening with Plotina.

Plotina; the author’s 130mm f/5 Newtonian still strutting her stuff.

It’s hard to believe that four long years have gone by since I first discovered the considerable virtues of a modest 130mm f/5 flextube Newonian reflector. Like the larger 8-inch f/6 Newtonian I switched to in 2015, this 5.1 inch instrument has proven to be an excellent all-round performer, doubling up as a high performance spotting ‘scope by day and a fantastic grab ‘n’ go telescope at night, where its very decent aperture, fine optics, light-weight portabiity and quick cool down time has yielded excellent views of the Moon, bright planets, deep sky fuzzies and a whole raft of double stars.

Shortly after testing the basic SkyWatcher unit, I invested in some modest-costing upgrades to further enhance the performance of this telescope. The secondary mirror was upgraded to one of higher quality and slightly smaller size (26.9 per cent linear obstruction). In addition, I had both the original SkyWatcher primary and upgraded secondary re-aluminised with Orion Optics UK’s proprietary HiLux coatings with 97 per cent reflectivity, giving an overall transmission of 90 per cent at the eyepiece once the area of the central obstruction is also factored in. The original flextube was replaced by a solid aluminium tube from a SkyWatcher 130P, providing a more stable arrangement for the secondary mirror housing. The tube was lined with cork and overlaid with flocking material to minimise stray light and increase image contrast. Finally, both the primary and secondary mirrors were equipped with Bob’s knobs to facilitate easy and quick collimation of the optical train. The resulting instrument sits pretty on a light weight alt-azimuth mount – a Vixen Porta II – which can be used both terrestrially and for astronomical observations.

The Vixen erector lens system used to obtain correctly oriented views with Newtonian reflectors.

In previous blogs I investigated ways to use this small reflector as a terrestrial spotting ‘scope, discovering methods to enjoy correctly oriented terrestrial views using a Vixen erecting adapter.The device allows the use of any eyepiece, thereby creating a spotting ‘scope with a much larger range of magnifications than those offered by conventional spotting ‘scopes. Its much greater light grasp allows me to enjoy crisp and bright high-power images well into twilight.

The 130mm f/5 Newtonian in terrestrial spotting ‘scope mode using the Vixen erector lens.

My 130mm f/5(aka ‘Plotina’) has travelled all over the British Isles with me, safely packed away in its foam-lined aluminium carry case, where it has sampled great skies in southern Ireland, northern England, Scotland and south Wales. These observations strengthened my conviction that there are many places where conditions are good enough to push the resolving power of this Newtonian telescope. Indeed, I have been able to split sub arc second pairs(0.9″) at ultra-high powers (up to 405x) in many of these locations. During summer heat, cool autumn and spring nights and freezing winter evenings, the telescope has never disappointed. Indeed, it has greatly exceeded all my expectations for it!

Portable powerhouse.

Best of all, it has saved me an absolute fortune, allowing me to completely break free from using small, expensive refractors, which became somewhat of an obsession with me for the best part of a decade. And quite frankly, to go back there again would be bonkers!

February 25 2020 Observations

Time: 21:20 to 23:15

Conditions; Cold (1-2 C), mostly clear and transparent skies with no Moon and with intermittent blustery west or northwesterly gusts. Seeing very good (Ant II).

Although the telescope optics takes a good 30 to 40 minutes to obtain the best high power images when taken from a warm indoor environment, it most certainly can be used with immediate effect if you start with low power wide field targets. I’ve recorded quite a few instances in which antagonists claim that the same telescope takes too long to acclimate to be a real grab ‘n’ go contender, but this is based largely on ignorance, laziness or just plain old lack of resourcefulness. In addition, it’s important to stress that I do not employ cooling fans on this or any of my other telescopes.

Accordingly, I initiated the session with low power (26x), larger deep sky objects, beginning with some showpiece open clusters such as the Double Cluster in Perseus, which was beautifully rendered in the wide, 2.3 degree true field served up by my Celestron X-Cel LX 25mm ocular.  From there, I ventured over to the large and bright open cluster M34 (also Perseus) enjoying several dozen stellar members, many of which are arranged in neat double or triples(mostly telescopic in nature), and then ventured southward into Gemini now sinking into the western sky, where I enjoyed a stunning view of the expansive M35, the excellent light grasp of the reflector showing up many fainter members that are either invisible or very faintly rendered in smaller (4-inch and under) refractors. The 130mm F/5 is a particularly good telescope for observing this sprawling Messier open cluster, combining the near-ideal combination of aperture, magnification and field of view to fully immerse myself in the view.

Camelopardalis was well situated high in the sky and so I sought out an opportunity to track down Kemble’s Cascade, so named after the late Canadian observer, and Franciscan friar, Father Lucian Kemble(1922-1999), who first called the amateur community’s attention to this remarkable, linear array of  15 or so stars tumbling down to the small open cluster NGC 1502 across the border in Cassiopeia. Spanning a full 2.5 angular degrees, Plotina was not quite able to encompass the cascade in its entirety. That said, the telescope served up a wonderful sight of stars ranging in brightness from the fifth to the 9th magnitude of glory. It is all the more remarkable that Kemble actually chanced upon this visually striking asterism using diminutive 7 x 35 wide-angle binoculars!

After spending a few minutes drinking up the view of the mangnificent Beehive Cluster M44 in Cancer, the telescope was now sufficiently well cooled to crank up the power to get some close-up views of the three Messier open clusters in Auriga. For these, I employed a power of 118x(Meade Series 5000  5.5mm UWA) in a generous 0.7 degree true field. All three clusters are visually striking in the 130mm f/5 at this moderate power, but by far the most fetching in my opinion is M36, which transforms from a small foggy patch about one third of the size of the full Moon in 8 x 42 binoculars(also accompanying me at the telescope) into a granular mound of faint stars some 5 dozen strong. Increasing the magnification to 135x using my 4.8mm T1 Nagler improved the view still further by helping to pull the faintest members of this cluster out of the background sky.

I was now ready to visit a suite of my favourite seasonal doubles well placed for observation on late February evenings. I began in Auriga, centring the bright white star Theta Aurigae. Cranking up the power 236x(Meade UWA 5.5mm and 2x Orion Shorty Barlow) and carefully focusing, I was delighted to obtain a near perfect image of the bright primary and the spark of the much fainter secondary tucked up close to it. This is quite a tricky system to image well though, and is thus a good test of seeing conditions at my backyard observing site, but tonight presented good conditions(as they often do here and elsewhere), so I knew that visiting a few other tricky systems would be a worthwhile pursuit on this fine evening.

Off I sped to enjoy an easy system first; Castor A & B, which was beautifully rendered at 236x in the 130mm, the two bright components presenting as pure white Airy disks, with the much fainter C companion easily seen wide away. From there I moved the telescope a little way ‘down’ the western sky until I centred  creamy Wasat (Delta Geminorum). The challenge here is to bag the exceedingly faint and close-in companion shining nearly five stellar mangnitudes fainter. I have found, through experience, that the Meade UWA 5.5mm yielding 118x provides the most compelling view of this optically delicate companion. The older 4.8mm T1 Nagler is not as good as the newer Meade ocular in showing this system at its best. I attribute this to slightly better coatings applied to the newer eyepiece. Attempting to push my luck, I panned the telescope a little to the northwest to the lovely marmalde orange star, Eta Geminorum(Propus) but even after crankning up the power to 270x and 354x, I was unable to resolve its very close-in companion. That said, this system was by now well past meridian passage and sinking lower into more turbulent air in the western sky.

As the evening progressed, Leo was now beginning to assert itself still somewhat east of the meridian. After a few minutes enjoying the rich aureal tints of Algieba(Gamma Leonis) and its companion, I panned the instrument southeastward until I centred Iota Leonis in the 6 x 30 finder accompanying the main telescope. This is quite a challenging system to resolve, consisting as it does of a 4th magnitude yellow-white primary and 7th magnitude secondary in a close-in orbit. Starting with 238x, I was able to discern the secondary as a tiny pimple like projection off the primary, but when I cranked up the power to 354x (3x Meade achromatic Barlow and 5.5mm Meade eyepiece),  and watching the system move rapidly across the field from east to west, I was finally able to see the secondary intermittently detached from the primary.  That said, I could have done with another hour and a half of waiting until it reached its maximum altitude in the south, but I was just happy to be able to resolve the system reasonably well at this earlier time of about 11pm local time.

Re-visiting Cassiopeia, still well placed high in the northern sky, I was able to enjoy a wonderful view of the lovely triple system, Iota Cassiopeia, which was easily resolved into its three components at 236x with the 130mm Newtonian. Nearby Eta Cassiopeia, with its comely red and yellow components widely spaced at 236x was also a worthwhile system to visit on this cold February night. Images remained sharp, crisp and contrasty even at these high telescopic powers.

Taking a quick break with my 8 x 42, I ventured to the front of the house, where I noted a rather lobsided Plough high in the northeast and lower down, the main stars of Bootes had by now cleared the murky air above the Fintry Hills to the east of the house. I then decided to move the telescope on its Vixen Porta II mount(which I can easily manoeuvre with one hand). Aiming my 6 x 30 finder at the two Alulas in Ursa Major, I centred each system in turn in the 130mm reflector. Alula Australis was truly a sight for sore eyes at 236x, the two stars presenting with beautiful, round yellow Airy disks separated by a sizeable sliver of dark sky. This is a fascinating system to watch with a small backyard telescope, where both 4th magnitude components complete one orbit of their barycentre in just 60 years! Ruddy Alula Borealis presented a different kind of challenge though, rather like Delta Geminorum observed earlier in the vigil. Using the very high contrast views of the Meade UWA 5.5mm, I was able to just make out the tiny and very faint spark of light of its close-in secondary at 118x.

I ended this late February observation session by trying my hand at Epsilon Bootis(Izar), a favourite Spring binary system. still quite low in the east at or shortly after 11.15pm local time. Deciding on a moderately high power of 238x, Plotina managed a decent split of this gorgeous colour-contrast pair(yellow and blue), but its low altitude was, of course, attended by increased atmospheric turbulence.

The title of this blog included the word, ‘magical,’ with the implication that there was something out-of-the ordinary about what the 130mm Newtonian can show. The truth is that these targets, especially the high-resolution systems discussed, can be enjoyed fairly routinely with this telescope from many locations(you just have to test them) and it is my fondest hope that others will take up the same challenges with their small Newtonian relectors.


Neil English has created a considerable volume of literature highlighting the many attributes of the 130mm f/5 Newtonian. He is seriously considering writing a full length manuscript of his experiences with this transformative instrument at some time in the future.


De Fideli.



2 thoughts on “A Magical Evening with Plotina.

  1. Hi Neil,
    Very interesting report on the merits of the 130mm Skywatcher newtonian.
    Out of interest, can you give a rough idea of the costs of the upgrades that you have made to this optical tube. Those mentioned in the 2nd paragraph of your report ?

    Many thanks,


  2. Hi John,

    Thanks for your message.

    Although I had to travel a rather circuitous route to arrive at the telescope I now have and use, it only cost me a couple of hundred pounds all-in. If I had started with the SkyWatcher 130PDS, I might have saved even more money.
    I have disclosed the price cost of all the upgrades on a string of earlier blogs on the 130mm.

    All in, it was a very cost-effective and fun project.

    Best wishes,


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