An knowledgeable Dobsonian nice for newcomers
A brand new sequence of Dobsonians at the moment are accessible from Omegon. Steve Ringwood took the 152mm-aperture mannequin for a spin, and located that as an all-rounder, it dealt with expertly.
It may possibly seem typically that the majority up to date astronomy is worried with an unseemly rush to picture as a lot of the Universe as doable, with only a single wide-field seize. Certainly, there are rich-field refractors on the market with such brief ’all-sky vista’ focal lengths that the sphere lens of the eyepiece is sort of in touch with the rear factor of the target lens. However right here I welcome a telescope with a firmer footing in observational astronomy – and one which overtly seeks to offer a facility for detailed planetary and stellar viewing, whereas nonetheless providing a light-pulling capability for having fun with nebulae and galaxies. Underlying all of it is a said intention to offer a easy intuitive system with speedy deployment. I used to be eager to find how properly Omegon have succeeded.
Within the field
The package arrives in two packing containers: the optical tube meeting is within the first, whereas the Dobsonian mount comes flat-packed within the second. Don’t let the time period ‘flat-pack’ panic you, for that is no inscrutable jigsaw puzzle with designed-in misinterpretations. There are solely 5 main components, with only a few add-on fixings. The (downloaded) meeting directions are totally comprehendible, and I had the Dobsonian mount prepared to make use of in a leisurely 30–40 minutes – and that included a espresso break. The tube comes connected to its trunnions, so it solely remained for the telescope to be lowered into place.
As a way to present extra stress between the rocker-box’s Teflon pads and the operating floor of the tube trunnions, the design features a pair of reasonably fierce springs that pull the tube towards the rocker field through protrusions in every. This provides commendable stability to the telescope’s altitude movement, compensating for the doable imbalance of the various payloads that is likely to be utilized on the focuser finish. Nonetheless, I can personally attest that care have to be taken throughout the connection of those springs, and to carry them solely by their terminating loops, for in any other case the contracting coils can chunk.
As soon as totally assembled, these springs keep connected to the telescope’s trunnions, the place they type of waggle about and get in the best way throughout storage. It makes extra sense to me for them to stay connected to the rocker field. However then, maybe the designers had different concerns.
I encountered just one oddity throughout meeting, that of the 6 × 30mm finderscope. Focus is achieved by adjusting the target lens. I discovered that I might hardly attain focus, and solely then with the lens meeting unscrewed and actually hanging by a single thread, proper on the finish of its journey. My right-eye dioptre worth is about +2.0, however the finder ought to provide extra correction that that. I made do, however precariously. Maybe the finderscope’s tube size could possibly be just a little longer, or its goal lens’ adjusting thread just a little deeper.
When all is completed, the picket base and rocker field collectively weigh just a little over eight kilograms, making it eminently snug to move one-handed to your observing place utilizing the carry deal with offered. As soon as in place, it takes only a second journey to fetch and match the 9 kilogram tube meeting and you’re up and operating. Really, a ‘quick’ system for on the point of observe the sky.
Earlier than commencing an observing run, I did after all test the collimation of the optics. It was the merest trice out (seemingly precipitated in transit), however the positive changes accessible on the centre-spotted main and secondary mirrors and the help of a pleasant laser collimator made brief work of the deviation. I’d add that not less than a short tuition on collimation could possibly be added to the directions, since this facility is, in spite of everything, a part of the telescope’s development – and newcomers are a goal marketplace for this telescope.
In check
Only a day after a clouded out partial lunar eclipse, a waning gibbous Moon made amends by making itself accessible, low down in a south-eastern sky, for commentary. As an extra deal with, the telescope and I have been ourselves noticed, for the reason that Worldwide Area Station made a superb move simply as I used to be establishing.
I started by utilizing the provided 25mm eyepiece, delivering 48×. The Crayford-style focuser was very easy, and the Moon snapped into focus inside a subject just a little over twice the lunar diameter. Element was wonderful with good distinction. Lunar gentle completed on the Moon’s limb, disturbed solely often by some annoying wispy cloud. What creased my brow just a little was that attending to focus consumed nearly the whole lot of the again focus (said as 50mm). This margin is just a little tight for my liking, since many prefer to experiment with interposing equipment between the eyepiece and telescope. It gave me no downside throughout the assessment however does lead on to my subsequent remark.
Of this new sequence of Omegon’s superior reflectors, the 152mm is the one one fitted and not using a two-inch focuser. It may possibly after all be argued that due to the smaller secondary mirror of this mannequin’s optical system, use of bigger eyepieces could end in vignetting (peripheral fall-off of illumination). But many eyepieces and equipment which may in any other case be confined inside a 1.25-inch becoming are generally contained inside a two-inch commonplace jacket. Because it occurs, the rackmount presents a T2 thread, to which (when wanted) I fitted a T2 two-inch-fitting adaptor. You’ll learn additional on that, on this method I loved wonderful views by way of numerous two-inch becoming eyepieces.
It’s far simpler to step down a two-inch focuser to a 1.25-inch becoming, reasonably than vice-versa – and my view can be to ask why begin somebody off with a limitation that on the manufacturing stage could possibly be corrected for only a few kilos additional, to what’s already a really keenly priced instrument. The extra weight of my two-inch eyepieces didn’t overpower the strain exerted by the trunnion springs, and even when that they had, creative customers can at all times add some mass on the different finish.
As testomony to the usefulness of two-inch eyepieces on this telescope, I swapped out the provided eyepiece and (after retro-fitting my adaptor) deployed a 9mm Lunt, boasting an obvious subject of 100 levels. Even on the ensuing magnification of 133×, the whole lot of the Moon’s disc was nonetheless in view, with room to spare in a subject 45 arcminutes large. On the japanese limb sundown was starting to interrupt out, with the ‘limbward’ terraces of Mare Crisium solely simply beginning to present reduction. It was a fantastic view. Admittedly, a newbie could not initially aspire to the possession of the costlier two-inch eyepieces, however the entire level of a telescope aimed toward newcomers is to develop their ambitions, so I counsel that this focuser be upgraded to the identical degree as its siblings.
Planetary challenges
Already low, the Moon sank out of view behind some homes, however (staying with the 9mm) Saturn supplied itself in its place. Saturn had none of its common splendour, however this was no fault of the telescope. Only a few months wanting the Earth passing by way of the airplane of Saturn’s rings, the planet regarded like a washed-out Jupiter with a skinny pencil pushed by way of it. Titan floated close by. The telescope was delivering nice readability and actually starting to point out its mettle as a planetary instrument. As a result of the rings have been at such an acute angle, extra of the very tender pastel shading of the equatorial banding was coming into view.
Rain had earlier settled the environment and stability was superb, so I swapped out the two-inch configuration and put in an previous diehard, my 1.25-inch, 4.8mm (82 levels) Nagler. Now at a magnification of 250×, Saturn and Titan have been nonetheless captured in a single look, however there was no lack of high quality. Certainly, if something, the pastel bands of Saturn’s disc have been bolder and the rings have been now not stick-like, with their extremely slim elliptical profile changing into seen. I might even make out the knife-like slash of the shadow of the rings projected onto the globe. The darker backdrop of the upper energy additionally lifted the magnitude +9.8 moon Rhea and +10.3 Tethys from the gloom, making a warming household scene.
The declare for this sequence of telescopes is of utilizing very good optics, underpinned by way of a superior parabolic main mirror (you typically discover using spherical at this focal ratio). I can attest this declare is legitimate, for the reason that extra I demanded, the extra it gave.
Not only for the devilment, I moved to the next energy Nagler, that of two.5mm. At a magnification of 480× (I hear the purists scream!) that is past what you’ll usually apply to a telescope of this aperture. Nonetheless, this was not a check of what I might see, though Saturn nonetheless introduced a creditable look within the 10-arcminute subject. This was a trial of how I might transfer.
The alt-az mount of a Dobsonian could be very intuitive, however its efficiency depends very closely on how easily it may be manhandled to a goal and stored there. On this instance, the altitude movement is managed by the Teflon pads tensioned (albeit with out adjustment) by trunnion springs, with azimuth movement managed by friction altered by a hand knob connecting the bottom plates. With just a bit tinkering with the azimuth adjustment, I had little bother protecting a swift-footed Saturn inside its 10-arcsecond subject. This was nice proof that the mount was totally able to permitting the telescope to succeed in its full potential.
I’d add just one factor to the rocker field. It comes fitted with a deal with for its personal transport and this works properly. Nonetheless, when mated to its telescope cargo, I had the occasional want to maneuver the entire meeting just a few yards with a purpose to make observations from a barely completely different place. The present deal with does probably not help on this case, and I discovered myself reaching for non-existing handholds on the prime of every facet of the rocker field.
Star checks
After all, this telescope isn’t just about planets. I wanted an in depth examination of a star picture and with a excessive energy settled on magnitude +1.8 Mirfak (alpha Persei), excessive within the north-eastern sky. It yielded a superb diffraction sample, indicating good definition for stellar in addition to planetary commentary. In what appeared a useless affirmation, I stayed with this magnification for a have a look at epsilon Lyrae (the ‘Double-Double’). This quartet of stars may be separated by a telescope of smaller aperture, however the readability of that separation stays a great check of even reasonable devices. I’m glad to report that every of the paired elements had a satisfying wash of clear water between them.
As soon as the Moon had moved on in its orbit and left the sky to fainter prey, I returned to Lyra for examination of M57 (the Ring Nebula). It’s a favoured little beast, however it appears at all times surprisingly smaller than you count on, no matter magnification. Distinction was superb, a distant smoke ring puffed from the darkness.
Being late September, two different deep-sky favourites introduced themselves, the Double Cluster in Perseus and (nearly overhead) the galaxy M31 in Andromeda.
I dropped just a little beneath the provided eyepiece and used a 40mm Plössl, acquiring a magnification of 30× and yielding a really helpful large subject of practically two levels. The Double Cluster by no means fails to impress. I used to be handled to a twin explosion of stars, good to the sting of the sphere. Once more, very good optics at work. I didn’t rush away – I merely drank within the scene. I then moved to M31. At an influence of 30× its nucleus is sort of star-like, and impressively I might make out the ansae of the galaxy’s ellipse disappearing by way of either side of the eyepiece’s subject cease. The 40mm eyepiece delivered an excellent stand-off view, however because the seeing circumstances have been good I made a decision it was time to carry again one of many two-inch-eyepiece squad – a 13mm at 92× having an obvious subject of 100 levels. The true subject it delivered was nonetheless just a bit below a level of sky, subsequently capturing only a third of the galaxy, however it distended the star-like nucleus right into a diffuse ball of sunshine, like a distant headlight within the fog.
With the identical eyepiece I returned to the Double Cluster. Though the smaller subject didn’t seize each components as earlier than, the upper magnification deepened the background to a velvety black, enriching the brilliance of each star in view – and what a view it was! Like sizzling coals burning in a cellar. A newbie unused to such visions goes to be more than happy with this degree of supply.
Extensive obvious fields
Any telescope claiming a planetary capability has to have its mettle examined towards the king of planets, Jupiter – and luckily, simply as morning twilight was seeping into the night time sky, it grew to become accessible within the east. I started with a 10mm at 120×, offering a delightful scene of a clean-shaven belted disc accompanied by all of its Galilean moons. Io and Europa have been in shut attendance, with Ganymede and Callisto flung to the farthest reaches of their orbits.
I shortly scaled as much as a 6mm, delivering 200× with no lack of high quality. The equatorial bands have been in stark reduction, bracketed prime and backside by the polar hoods. At 300×, the extra delicate traceries of intervening belts could possibly be seen. The planet was wealthy in grey-browns and amber and the moons stood proud as diminutive discs.
By dint of its look, Jupiter offered a chance to play with most usable powers. Whereas my 2.5mm Nagler didn’t current a usable magnification to work with, dropping right down to a 3.5mm (100-degrees) Lunt did give moments of nice element. Since this delivered an influence of 343×, this accords properly with Omegon’s prompt most of 300×. I do advocate use of eyepieces of large obvious fields, equivalent to these between 82 and 110 levels, particularly for reasonable to increased powers. This makes it simpler to maintain an object in view with fewer nudges of the alt-az mount.
The eyepiece top from the bottom, viewing from horizon to the zenith, approximates 75cm to 120cm. All of this vary is accessible from the seat of a median cozy chair, though you might have to raise your self onto your toes often to get beneath the eyepiece of the straight-through finder.
That is an impressive telescope for speedy set-up, on the outset of a brand new observer or the onset of a transparent night. It has nice potential, belied by a really eager value level.
Steve Ringwood is a daily contributor to Astronomy Now.
