Sonntag, Juli 31, 2022
StartSpaceThe sunshine-bucket with a contact of sophistication – Astronomy Now

The sunshine-bucket with a contact of sophistication – Astronomy Now


First Gentle Optics’ StellaLyra 250mm, f/5 Dobsonian, in its attractive black end, suggestions the scales at 29 kilograms. Picture: FLO.

Based in Exeter, First Gentle Optics (FLO) sells a formidable vary of reflecting telescopes beneath its personal StellaLyra model. Encompassing Newtonian, classical Cassegrain and Ritchey–Chrétien optical configurations, these devices are designed and manufactured for FLO by Guan Sheng Optical (GSO) in Taiwan –an organization with a long-standing status for high-quality workmanship and revolutionary design.

For essentially the most half, FLO’s StellaLyra telescopes are offered as optical tubes and equipment however with out mounts. The exception is their suite of 150 to 400mm (6- to 16-inch) Dobsonians, which include the whole lot that it is advisable observe straight out of the field. For the needs of this analysis we selected the mannequin that sits squarely in the course of the vary, the ever-popular 250mm (10-inch), f/5.

Except for the biggest StellaLyra Dobsonian, which is a 400mm truss-tube design, the vary possesses one-piece rolled metal tubes.

Whereas this does imply that they might be a bit heavier and extra cumbersome than competing flex-tube or truss-type implementations, many individuals choose the optical safety and rigidity afforded by a strong optical tube meeting that reduces the buildup of mud on the mirrors (for the reason that tube is sealed when not in use), improves distinction in closely light-polluted environments, and helps preserve dew at bay.

All StellaLyra Dobsonians of 200mm aperture and bigger include two totally multi-coated eyepieces and a large-aperture, right-angled, correct-image finderscope to avoid wasting you from getting a cricked neck. Moreover, the mounts of all however the 150mm aperture mannequin possess deluxe altitudeaxis bearings with rigidity and stability adjusters, plus a roller-bearing azimuth system, additionally with rigidity adjustment. These superior options put the StellaLyra devices squarely in premiumclass Dobsonian territory.

Supply and meeting

The StellaLyra 250mm mannequin is couriered to your door in not one, however two containers. The most important, containing the optical tube and equipment, is 49 × 50 × 141 centimetres in measurement, grossing 20 kilograms. The smaller field containing the Dobsonian mount in flatpack type is 64 × 64 × 14 centimetres and suggestions the scales at 15 kilograms. So it pays to have an additional pair of palms that can assist you unpack and assemble the telescope. That stated, the one a part of the instrument requiring a modicum of DIY is the Dobsonian altazimuth base; the optical tube is pre-assembled aside from the altitude bearings, which I’ll return to presently.

A more in-depth take a look at the Crayford focuser. Picture: FLO.

The evaluation unit didn’t include any meeting directions, however a fast examine of the related web page of First Gentle Optics’ web site revealed a downloadable PDF. If you happen to’re not ready to seek the advice of the five-page PDF in your smartphone, it could be a good suggestion to ask FLO to make sure a paper copy is included. Thankfully, the meeting directions are clear and straightforward to grasp. A lot of the mount itself is pretty commonplace Dobsonian fare when it comes to development supplies, specifically plasticcoated particleboard.

Owing to Mrs A’s penchant for Scandinavian flat-pack furnishings, I contemplate myself one thing of a wizard with an Allen key (equipped, although you’ll want a cross-head screwdriver too). In accordance to the stopwatch, I constructed the altazimuth base in 17 minutes and accomplished meeting in 25 minutes general. Having constructed quite a few Dobsonian bases over time, I’ll have a little bit of a bonus, so I’d clear a big house in the lounge and put aside a minimum of 45 minutes to finish the duty.

The superb 8 × 50, right-angled, right-way-up finderscope. Picture: FLO.

The StellaLyra suite of 150 to 400mm (6- to 16-inch) Dobsonians accommodates the whole lot that it is advisable observe straight out of the field

Mount refinements

As talked about earlier, there are some refined options of the mount worthy of word. In contrast to most price range Dobsonians, the azimuth bearing is just not merely a base board with a central bolt and three items of slippery Teflon gliding towards the underside of the mount. Quite, the 200mmaperture-and-larger StellaLyra Dobsonians use a needle roller-bearing sandwiched between two 32-centimetre-diameter metal-bearing plates.

A tensioning knob (with its personal small thrust bearing) threaded by means of a centre bushing joins the highest baseplate, azimuth roller-bearing and floor baseplate. Therefore, relatively like a clutch, the tensioning knob can regulate the stiffness and freedom of movement left to proper, which is an efficient factor as with out it the azimuth axis is nearly too clean and the telescope revolves on the slightest contact!

On both aspect of the optical tube lie two lozenge-shaped face plates, every with graduated scales and milled channels containing captive bolts designed to simply accept the left and proper altitudebearing assemblies. Every bearing has a beefy clutch knob to regulate the liberty of movement and two bolts that, when unlocked with the equipped Allen key, allow the bearings to maneuver in the direction of or away from the first mirror over a 63.5mm vary.

Wanting down the tube of the 250mm StellaLyra Dobsonian, on the main mirror and the four-vane assist of the secondary mirror. Picture: FLO.

The StellaLyra 250mm, f/5 Dobsonian is clearly an instrument that lives as much as GSO’s status for high-quality optical efficiency, bundled with good high quality eyepieces and a superior 8 × 50 rightangled correct-image finderscope

By shifting the altitude bearings fore or aft you’ll be able to exactly stability the tube in response to the load of the eyepiece and equipment in use, the graduated scales on both aspect guaranteeing that the altitude axis is perpendicular to the tube. That is actually necessary if you happen to want to use digital setting circles at a later date (see the top of this evaluation for extra about this). Every bearing meeting has a U-shaped alloy casting that merely slots into the highest of the mount’s aspect panels for fast deployment.

Regardless of the commendable altitude- and azimuth-axis enhancements, there are minor niggles. Because the measurement of the azimuth needle roller-bearing is 32 centimetres in diameter, why make the mount’s baseplate 56 centimetres in diameter, which is tougher to manoeuvre between door frames? Granted, the mount’s aspect panels should be braced and 36 centimetres aside to accommodate the tube and aspect bearings, however slimmer profile aspect panels would end in a extra compact mount.

With out the azimuth-axis tensioning knob locked down firmly to stop the tube spinning away from the article you’re viewing on the slightest contact, there’s some flexure right here. That stated, vibrations from a pointy rap to the tube dampened in two seconds with the mount standing on patio slabs. And whereas it’s potential to stability the tube completely when horizontal, the tube pitches again when viewing at excessive altitudes owing to the comparatively heavy finderscope; splitting the distinction within the stability level and clamping the clutches alleviates this, however on the expense of some smoothness in altitude movement.

Impressions

If there’s any reality to his “any color – as long as it’s black” quote, then American industrialist Henry Ford would’ve liked this telescope. Its 30.3-centimetre diameter, 1.21-metre lengthy metal tube has an unobtrusive seam beneath and a beautiful gloss powder coat end (albeit one thing of a fingerprint magnet), with charcoal gray, Hammerite-finish, rounded end-rings each prime and backside. The plastic coating of the mount’s particleboard panels has a textured satin end, with a carrying deal with on the entrance brace and a metallic holder for one 2-inch and three 1.25-inch eyepieces on the aspect.

The assembled telescope suggestions the scales at near 29 kilograms, 16 kilograms of that being the tube meeting alone. Its size implies that it could possibly comfortably lie throughout the again seat of most automobiles, although the mount could show to be essentially the most awkward element when transporting it to a dark-sky website. Fortunately, the Dobsonian may be very tolerant of being moved. In actual fact, the instrument was virtually completely collimated straight out of the field, which speaks volumes for GSO’s high quality management and high-quality mirror-cell design.

The first mirror consists of a BK7 glass mirror clean, 250mm in diameter with a transparent aperture of 246mm, permitting for the chamfered edge. The first is completely centre-marked and sits on cork shims within the cell, with rubber grommets stopping any lateral or front-to-back flop. Across the circumference of the first cell you discover three spring-loaded, black hand-knobs for collimation, and three white hand-knobs to lock down the mirror after alignment is achieved. A mirror cooling fan operates from the 12V battery pack offered (AA cells further).

On the different finish of the tube, the 4 metallic vanes of the secondary assist are properly tensioned and really skinny (roughly 0.7mm) to minimise diffraction results. The elliptical secondary mirror can also be cemented to its holder to keep away from any diffraction-inducing clips round its periphery.

The StellaLyra’s left altitude axis clutch and adjusters. By shifting the altitude bearings fore or aft you’ll be able to exactly stability the telescope. Picture: Ade Ashford.
On both aspect of the tube are lozenge-shaped face plates, every with graduated scales and milled channels containing captive bolts designed to simply accept the left and proper altitude bearing assemblies. Every bearing has a beefy clutch knob to regulate the liberty of movement. Picture: FLO.

Nevertheless, GSO selected to not offset the secondary mirror to accommodate the comparatively steep f/5 gentle cone from the first mirror – not that it actually makes any noticeable distinction in a visible instrument equivalent to this. Secondary collimation requires a Phillips screwdriver.

Clean, exact and totally adjustable, the dualspeed CNC-machined Crayford focuser’s drawtube has 42mm of journey and an etched millimetre scale for reproducing approximate concentrate on altering eyepieces. The two-inch and 1.25-inch eyepiece adaptors have brass compression rings to securely maintain your eyepieces with out marring their barrels. Neither of the equipped oculars required the equipped 35mm extension tube to succeed in focus, though it will likely be helpful for third-party eyepiece and Barlow mixtures.

The bundled 1.25-inch format, 9mm Tremendous-Plössl and 2-inch, 30mm Superview eyepieces are of surprisingly good high quality. Each are multi-coated, threaded for filters and geared up with rubber eyecups; the 9mm delivers 139× magnification over a one-third of a level discipline, whereas the 30mm gives a 1.6-degree discipline of view at 42×. Because the latter delivers a 5.9mm exit pupil, middle-aged and older observers may not see the complete good thing about the aperture due to restricted pupil measurement, however the views might be as shiny as they will probably be. A clever future funding is a 2-inch, 2× Barlow lens to double-up the magnification of each eyepieces.

The size of the StellaLyra 250mm Dobsonian imply that it’s nicely suited to seated remark. With the tube horizontal, the eyepiece lies some 80 centimetres from the bottom in an ergonomic 45-degree viewing orientation, rising to an eyepiece peak of 1.23 metres when the telescope is pointed on the zenith. By turning the eyepiece of the 8 × 50 right-angled correct-image finderscope (which, by the way, is of excellent high quality, delivering extensive, sharp and contrasty views) such that it’s parallel to the telescope’s focuser, implies that it’s very handy to maneuver one’s head the 20 centimetres between them.

The equipped 30mm SuperView eyepiece didn’t require the bundled 35mm extension tube to come back to focus, however third-party oculars would possibly. Each of the equipped eyepieces and equipment are of surprisingly good high quality.

Optical efficiency

I examined the StellaLyra 250mm Dobsonian on the Moon and Jupiter, plus various double stars and deep-sky objects from a suburban again backyard the place gentle air pollution permits views of the Milky Approach’s brighter parts on moonless nights of excellent transparency. The telescope cooled down fairly shortly, although gentle night-time temperatures didn’t warrant utilizing the first cooling fan. I discovered that I may get respectable photos 40 minutes after taking the instrument out of the home.

Jupiter, regardless of its present low altitude from the UK, revealed appreciable element when seeing circumstances permitted. On 21 October 2021 at 10:50pm BST, I watched the shut appulse of Jovian moons Ganymede and Callisto, whereas the Nice Crimson Spot approached the planet’s central meridian. Later that very same evening, the Moon was in the future previous full and offered a wealth of crisp, high-quality element alongside the waning terminator. I famous a string of mountain peaks within the coronary heart of 177-kilometre-wide crater Gauss catching the final rays of daylight. They regarded like a string of beads on the restrict of the instrument’s decision, one thing I had not seen on this area earlier than throughout four-and-a-half many years of observing.

The instrument star-tested very nicely too. There was a excessive diploma of symmetry, each intra- and extra-focally, with the merest trace of spherical under-correction. Equally necessary, the optical surfaces exhibited a clean polish with none troublesome zones. Vega was a blinding steely blue within the equipped 139× eyepiece, with delicate diffraction spikes from the skinny secondary-holder vanes, whereas epsilon Lyrae, the unmissable Double- Double, clearly revealed each pairs of stars at such a modest magnification.

he 9mm Plössl eyepiece affixed to the Dobsonian’s Crayford focuser, the drawtube of which has 42mm of journey and an etched millimetre scale. Picture: Ade Ashford.

Last ideas

The StellaLyra 250mm, f/5 Dobsonian is clearly an instrument that lives as much as GSO’s status for high-quality optical efficiency, bundled with good high quality eyepieces and a superior 8 × 50 right-angled, correct-image finderscope, however it’s nonetheless a push-to alt-azimuth telescope that requires you to starhop throughout the sky when searching for objects. Whereas I’d at all times encourage new customers to be taught the sky this manner, FLO gives a few add-ons for customers wishing to get essentially the most out of their funding.

Priced at £259, the Asterion Push-To Package for GSO Deluxe Dobsonians accommodates easy-to-attach {hardware} within the type of optical encoders to each the StellaLyra’s altitude and azimuth axes. After a easy alignment process, the unit transmits the telescope’s place wirelessly to Simulation Curriculum’s Sky Safari or Orion’s Star Search apps (Android or iOS). Thereafter, the system can information you across the sky to find planets, asteroids, nebulae and galaxies, double/variable stars and extra, by way of an interactive digital star chart in your smartphone or pill.

If regularly nudging your telescope to comply with objects turns into a chore, FLO can improve it to robotically observe objects too. Priced at £269, the Asterion Ecliptica Gentle Monitoring Platform sits beneath the instrument’s mount, carrying your complete telescope for as much as one hour of uninterrupted monitoring time earlier than needing to be reset. Therefore the StellaLyra 250mm Dobsonian could be thought to be a modular system to develop as funds and/or altering pursuits allow.

At a look

Mannequin: StellaLyra 250mm, f/5 Dobsonian

Optical design: Newtonian reflector

Clear aperture: 246mm (measured)

Focal size: 1,250mm

Focal ratio: f/5

Focuser: 2-inch dual-speed Crayford, 42mm journey

Mount: Dobsonian with dual-axis rigidity clutch management

Finderscope: Proper-angled, erect picture 8 × 50

Eyepiece 1: 9mm, 1.25-inch 52-degree Tremendous-Plössl, 6mm eye-relief

Eyepiece 2: 30mm, 2-inch 68-degree Superview, 22mm eye-relief

Equipment: 35mm, 2-inch extension tube; 2-inch to 1.25-inch eyepiece adaptor; 12V battery holder for the first mirror’s cooling fan

Tube dimensions: 303mm by 1,210mm (measured)

Mount dimensions: 640mm by 560mm (measured)

Tube weight: 16kg Base weight: 13kg Value: £649

Particulars: firstlightoptics.com/stellalyratelescopes/

Ade Ashford has travelled the globe writing about astronomy and telescopes, serving on the workers of astronomy magazines on either side of the Atlantic. His first Astronomy Now evaluation appeared over 1 / 4 of a century in the past.



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