Testing Svbony Optics on the First Scope Telescope

Testing Svbony Optics on the First Scope Telescope
Tests included the 2x Barlow, .5x focal reducer, full focal length set of Svbony eyepieces (both Plössl and Aspheric) on the Celestron 3" f/4 Dobsonian First Scope Telescope. The results are surprising!

I UPGRADED my Celestron Signature Series FirstScope telescope using optical components from Svbony, including finderscope, focal reducer, barlow and new eyepieces. The results were exciting and surprising to say the least. Let's take a look at what was learned in the testing process.

First let's talk about the setup. I set the telescope on a small round table indoors and imaged through the closed clean patio window. The single pane of clear (white) parallel float glass is relatively optically pure and works well for quick tests and good focus inside the convenient environment of a bug free and perfect temperature telescope control room.

I selected a set of two types of eyepieces from Svbony, a reliable supplier of telescopes and accessories. The first set are Plössl and the second set are Aspheric. Note: different EPs are known to have different performances given short or long focal length mirrors. 

Svbony Set One

40mm Plössl

32mm Plössl

Svbony Set Two

23mm Aspheric

10mm Aspheric

4mm Aspheric

Focal Reducer

.5x

Barlow

2x

The results are surprising. The set of Aspheric oculars, with a more simple glass design, was vastly superior, giving sharp focus bright images across the FOV. The views were dazzling and exciting!  Colors were exceptional, images formed clearly without distortions or aberrations, and the low cost of each eyepiece fit well with First Scope Telescope (a set of all three eyepieces currently costs $26.18, just a little over $8 each!). These EPs have outperformed other brands costing several hundred dollars each.

Another positive and greatly welcomed factor is the light weight of each ocular - weighing almost nothing - it does not upset the predetermined non-adjustable balance of the OTA. Aspherics won out over numerous other brands, for example, a 4mm Celestron ocular known for producing dim images has extremely tiny lenses that don't admit much light at all and it was very difficult for visual observing with an almost non-existent exit pupil. However, the Svbony Aspherical 4mm eyepiece was a pleasant surprise with its large diameter lenses, a comfortable exit pupil for visual observing, and exceptionally bright clear images especially for a short focus EP at high power.

However, given the fast focal length f/4, the Plössls, both 32mm and 40mm were a different story. Visual observing produced a black round spot in the middle of the fov, i.e. a shadow of the secondary, which can happen when the exit pupil is wider than 7mm. Clearly, the long focal lengths of these Plössls do not match the short focal length of the mirror. Therefore in conclusion, the Svbony Aspheric eyepiece set is the real winner and highly recommended for use with the F/3.95 Celestron First Scope Telescope.

Focal Reducer & Barlow Testing

Bonus Tip: Those thinking about trying a focal reducer ($9.45) with any of the tested eyepieces will soon realize the telescope does not have focus in range. However, the 2x Svbony Barlow ($7.90) is another big winner and works exceptionally well, even at the highest power when changing the 4mm into a 2mm. With the telescopes 76mm (2.99") aperture and 300mm (11.81") focal length at f/3.95, this gives 150x with tac sharp clear images. The Svbony 2x Barlow worked well with all three aspheric eyepieces (including the 23mm and 10mm) and is highly recommended for the Celestron First Scope.

Top left - Svbony .5x focal reducer attaches to the eyepiece. Left below - Svbony 2x Barlow also threads into a 1.25" eyepiece. The finderscope will be reviewed at a later date.

Celestron Firstscope Telescope Specs

Design - Newtonian Reflector

Style - FirstScope Signature Series

Manufacturer - Celestron

Mount - Dobsonian

Drive - None

Diameter - 2.99 inches (76mm)

Focal Ratio - f/3.95

Focal Length - 11.8" (300.2mm)

Prime Focus - 12x

Eyepieces - Original Celestron eyepieces melted

Resolution Rayleigh - 1.83 arc seconds

Resolution Dawes - 1.53 arc seconds

Limit Stellar Magnitude - 11.9

Light gather power compared to human eye - 118x

Adjustments - None

Highest Useful Magnification - 150x

Lowest Useful Magnification - 12x

Owner Added Accessories

* Svbony Aspheric Eyepiece One - 62 Deg., 23mm (.9") = 13x

   with 2x Barlow = 26x

* Svbony Aspheric Eyepiece Two - 62 Deg., 10mm (.4") = 30x

   with 2x Barlow = 60x

* Svbony Aspheric Eyepiece Three - 62 Deg., 4mm (.16) = 75x

   with 2x Barlow = 150x

* Svbony/Celestron Finderscope - 5x24, Plastic, Crosshairs, Focus

* Celestron iPhone Software - Sky Portal

* Computers - Apple Mac

* Image Processing Software - Apple System Photos, Mooii Tech PhotoScape X,

   GIMP, Soggy Waffles Paintbrush

* Apple Camera - iPhone

* Zwo ASI224MC Camera

* Svbony Focal Reducer - NA

* Svbony Barlow - 2x

* Svbony - Filters

Aspheric Eyepieces by Svbony

Calibrating the scale and weighing the 10mm EP gives .97oz., exactly as specified by Svbony

Compare 23mm to 23mm, the fat Celestron Luminos
EP setting on the scale is an irregular shaped massive
overweight boat anchor that was not usable on smaller
telescopes. On larger scopes it upset the counter-
balancing significantly. Seen here, the Luminos EP
overloaded the 10,000 gram scale. The aspheric
23mm eyepiece is seen at top left.

Introducing Fantastic Aspheric Eyepieces by Svbony Optics
These aspherics are the Cat's Pajamas!

Different lens designs have different performances with various telescope mirrors. Some oculars will set you back $600 to $1200 and yet perform poorly on half of the telescopes you may own. Others, like the aspheric design, may cost $9.50 and give phenomenal performance!

Nice Big Lenses
The aspheric design has large diameter lenses
ideal for both visual eyepiece projection and
astrophotography. At left, the lens is .87 inch
in diameter and at right .39". Their EP lengths
are 2.36" and 1.69" and adapt well to projection
with the Apple iPhone camera. The exit pupil is
generous and considered just right. The barrel
construction is from very light weight materials
trimmed in gold, chromed on the lower half,
engraved with a flat black interior.

As an optician, experimenter and inventor, I like to try new lens combinations and see how they perform. Thus far, the aspheric oculars were tested on the f/3.9  2.99-inch diameter Celestron FirstScope and perform as real winners. The light weight of these EPs are idea for small telescopes that have no means to tube balance. Aspherics are somewhere in between complicated lens designs with many lens elements and a simple one lens. However, it works to correct aberrations such as spherical and astigmatism, and maximizes light transmission.

— if the single aspheric lens is ground and polished to 1/4th wave, then having an eyepiece with 6 or 7 lenses all at 1/4th wave adding their defects together is absolutely not preferred —

The asphere's more complex surface profile can reduce or eliminate spherical aberration and also reduce other optical aberrations such as astigmatism, compared to a simple lens. A single aspheric lens can often replace a much more complex multi-lens system. Wiki

My set of aspherics range in cost from free to about $14. I have dedicated a 10mm 62 degree and 23mm 62 degree to the FirstScope as the best oculars for this telescope. In the future, I will definitely expand on my collection of this eyepiece type. Getting complete sets of aspherics can save thousands of dollars over other eyepieces. The images are bright and sharp with a compatible exit pupil due to a welcomed large lens diameter. No squinting necessary. The rubber top insulated eye stop protects the eye from bad weather that's to hot or too cold. The simplicity of performance is outstanding and ideal for EP projection and astrophotography or visual observing. They have a wider FOV compared to popular Plossls and these are the lightest weight EPs in my collection. The 10mm is 428 grams (15oz) and the 23mm is 666 grams (23oz). By comparison, the massive 23mm Celestron Luminos overloaded the 10,000 gram scale! According to Celestron, it weighs 1lb 13.3oz or 29.3oz. That's 30 times heavier than the aspheric eyepiece! Comparing both 23mm EPs, aspheric to Luminos, the aspheric has a much larger lens. The aspherics have a set of 4mm, 10mm, and 23mm as offered by Svbony for about $9.90 each. The weight is listed as 1.48oz, .97oz and 1.69oz respectively. Svbony has provided fast outstanding service.

In summary, the 1.25" aspherics are the bargain of the century, come fully packed in their own bags and boxes, are attractive with gold and chrome, low cost, high on performance, give bright images, have a wide FOV, perfect exit pupil (10 and 20), light weight, fully coated, have a rubber top eye stop/protector, are engraved, threaded for filters, and include full lens caps, plus they are sold online by Svbony, an excellent provider of astronomical telescopes and supplies.