Monday, December 19, 2016
As described in a previous blog, I have come to learn the many virtues of the powerful yet relatively inexpensive SkyWatcher Heritage 130P, a 5.1 inch f/5 tabletop Newtonian. I described various modifications I made to the telescope in order to optimise its performance. These included replacing the existing secondary with a smaller unit, giving a secondary obstruction of just 27 per cent. Both the primary and secondary mirrors were also treated with Orion Optics’ HiLux super high reflecting coating, providing brighter, more contrasty views of celestial targets. I also described some modifications which involved tightening up the secondary stalk holding the secondary mirror in place, which helped maintain precise collimation while the telescope was being slewed to different parts of the sky.
I can report that the telescope is still performing excellently, so much so that I now question the wisdom of using a small aperture refractor (or catadioptric) for grab ‘n’ go excursions. As explained in my blog, this telescope is very lightweight, fits on a variety of ergonomic mounts owing to the included Vixen style mounting plate, and cools super quick due to its relatively small, thin primary mirror and open tube configuration. But on the evening of December 19, I learned yet more of its secrets.
The night was cold (near zero Celsius) but the sky remained steadfastly clear from sunset to near sunrise the next day. I felt rather tired that evening, having gone through several hours of maths teaching, but I still wanted to venture out under the wintry sky before the waning gibbous Moon got up. So I turned to the 130P, mounting it on a lightweight Vixen II Porta altazimuth to get some observing in. Seeing conditions were not fantastic but perfectly adequate for most targets. The instrument was precisely collimated using an inexpensive laser collimator, as described previously, and made even easier since I installed some Bob’s Knobs secondary adjustment screws. This operation takes only a couple of minutes to execute accurately and I was then ready to reach for my Baader Hyperion zoom, an eyepiece I have grown very fond of owing to its excellent quality for its modest price. Indeed, it really is only slightly inferior to high quality oculars of fixed focal lengths. Thankfully, this is now being openly acknowledged by many amateurs on the forums. See this interesting link comparing this zoom to a much more expensive Leica zoom covering more or less the same focal length range.
In previous excursions, I reported that the zoom was rather heavy and I was concerned that it might be throwing off the collimation as the telescope was aimed at targets of varying altitude. But I can report that the addition of a single washer to the stalk holding the secondary mirror greatly increased the rigidity of the system and I felt I could chance using this large (and bulky) eyepiece as my only portal on the Universe on this frosty evening. So, how did it perform? In a word; magnificently!
But to elaborate, I discovered that the zoom keeps one’s body a few inches further back, away from the optical train, and more effectively attenuates the thermal heat plumes issuing from my body. An open tube like the Heritage 130P is significantly more sensitive to thermals introduced into the optical train, especially on cold nights like that experienced on the evening of December 19. I was actually quite shocked at how calm the images appeared in the eyepiece, examing as I did, several fairly tricky double and multiple stars, including some of my seasonal favourites, like beta Monocerotis (at a fairly low altitude), and much higher up: theta Aurigae, iota Cassiopeiae and (the less challenging) Castor A & B. All were well resolved. The native zoom provides a very useful range of magnifications from 27 to 81x, and can be further extended to a greater range of powers up to 182x (and thereby further extending the distance from the optical train). The images of all these systems were remarkably calm!
Furthermore, comparing the views through the zoom and a much lower profile 7.5mm Parks Gold ocular and Barlow, I could see that the images remained calmer for longer using the zoom. The images were quite simply less affected by anthropogenic turbulence. This is going to make a very significant difference while conducting high resolution work with this telescope during the many cold nights we experience here in Scotland. Nor did the zoom cause any miscollimation issues throughout the vigil. The stars always focused down to small, tight and round seeing disks.
Moving back to the native zoom, I visited M31, riding high in the winter sky, followed by the beautiful trio of Messier star clusters adorning the heart of Auriga (M36, M37 & M38), and from there I visited to my favourite Messier open cluster, M35, in Northern Gemini. I experienced nothing but pure joy experimenting with the right magnifications to frame these clusters using the zoom and the Barlow. I especially like the way the zoom ‘opens up’ at the lower focal length settings (to a very generous 72 degrees indeed) allowing one to soak up the beautiful hinterland around the Auriga clusters.
From there, I panned the telescope down to M42, the Great Nebula in Orion, which had, by now, all but reached meridian passage, and I ‘dialled in’ the optimum viewing magnification (about 150x as it turned out), drinking up the beautiful, crisp nebulosity surrounding the theta Orionis complex (Trapezium).
My adventure under the winter sky was a wonderful experience and only ended once I saw the vault of light emerging in the eastern sky from a rising Moon. The telescope is well able to handle this extraordinary eyepiece, enabling me to effortlessly cruise from low to high power. As I already reported, it is significantly more powerful than a 90mm apochromatic refractor (tested extensively along side the 130P over several months). It can do things no 127mm Maksutov can do, especially on low power, wide field targets, and its smaller central obstruction ensures crisper lunar and planetary views.
This grab ‘n’ go system will take your short, backyard excursions to new heights, thanks to its very generous aperture. Can I recommend this telescope and zoom eyepiece combination highly enough?
Neil English is the author of several books on amateur telescopes.
Please check out this ongoing thread on a related telescope, The One Sky Newtonian, which is still going from strength to strength.