Wild Experiments with the Acuter Maksy 60

The massive 2-inch Tele Vue 55mm Plossl eyepiece weighed more and was almost bigger than the entire Acuter 60mm Maksutov telescope!

FROM F/12.5 TO F/6.25
Wild Experiments with the Acuter Maksy 60
I put a 2" barrel diameter Televue 55mm Plossl with a 50 degree FOV on the minuscule maksutov telescope making it f/6.25 instead of f/12.5. You can only guess what happened next!

The 55m 2" ocular from Televue is massive. It's heavier than the entire telescope and tried to topple the scope when using the small table top tripod. The tripod had to be cinched very tight with both adjustment screws and I had to be vigilant to keep it from tipping over.

Above: Holding the telescope and holding the camera pressed to the eyepiece and then touching the screen to take the photo was a challenge. Without spending any time on focusing, the hand held mobile phone captured this view at 14.75x and F/6.25 instead of F/12.5.

Left: to compare to the 55mm focal length eyepiece, a gold line 23mm 62 FOV aspheric was used from Svbony. Visually the EP provided an exceptional view. Through the camera, the round circle containing the image was small.

To set up this massive EP, a 2-inch to 1.25" adapter was used which easily fit into the 1.25" 90-degree diagonal. The EP view was fantastic, smaller, brighter but had one odd anomaly - the camera could not get close enough and mainly showed a small round circle with the object of interest inside. Note - weather conditions were increasingly terrible, with fog and haze moving in. Photos are low contrast due to fog, haze and heavy air pollution.

At this time, I never had the chance to try the camera's zoom which might have filled the FOV. I was, however, able to place my eye properly to see the objects correctly with the full FOV. Eye relief is not very much with this ocular and telescope combination. At the lower left and right edges, the prism cut off a small section of view. However, things changed with the 23mm ocular and the camera was zoomed in a small amount. See photo at left.

Acuter Mak 60mm Star Test

Acuter Mak 60mm Star Test

Star Test - when sweeping the sky to locate the planets, many stars passed through the FOV. This was surprising as usually the fog, mist, upper atmospheric haze, light and air pollution severely limit any number of stars seen. It was decided to do the star test, to look at the optical figure of the new Acuter 60mm Maksutov (Maksy) telescope. I was not expecting too much but the test was a real surprise, looking like the perfect depiction from a book showing symmetrical perfect concentric rings. How is that possible?

The telescope is definitely a keeper! If a telescope's collimation is perfect and the atmosphere is transparent and still enough, the focused image of a star will be very much like a circular dot of light. The star test was picture perfect! It's a good thing too - there are no adjustment calibration points visible on the telescope. The existing calibration at this level of precision will enable the Acuter Mak 60 telescope to have the potential to become an instrument of high resolution. On days and nights of steady seeing conditions, it will be interesting to run such tests of resolution on images of the Sun and Moon. In the future, the connection of a CMOS camera will show images of the optical alignment.

Basic Star Testing

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

Celestron FirstScope Test Accessories

FirstScope Project: Test Accessories

Finally this is what we are all waiting for! Project Test, More Eyepieces, Focal Reducer, Barlow Lens, Focus Test, RFT Results

First, for our main tests we used the 10mm 62 degree Aspheric eyepiece from Svbony, which is the best performer in the Celestron FirstScope. The Celestron is an RFT with a focal length of only 12-inches and a defective secondary mirror. Nevertheless, the small Moon appears extremely bright.

In keeping right on budget, none of the accessories exceeded $14 in cost.

The big problem encountered was the handheld iphone could not adjust for all the light coming through the eyepiece. A Moon filter could not reduce the light in any significant amount and was set aside. Next I tried a polarizing filter. Still the moonlight was far too intense. Finally the tests were shot with the overexposed Moon. The first image shows the Moon image scale through the 10mm 62 degree Aspheric eyepiece.

The next image shows the Moon with the same eyepiece and an attached Svbony .5x focal reducer screwed to the bottom of the eyepiece.

In the third image, the eyepiece and a 2x Svbony Barlow were used. The Barlow screws to the bottom of the eyepiece. The change in image size is apparent.

Next, a 32mm and 40mm focus Plossls were test and they did not do well with the scope. The Moon had the image of the mirror and eyepiece superimposed over it. These fast eyepieces just don't work in this telescope. The final photo shows another type of obstruction defect that occurs, blocking out most of the Moon.

In all tests, the full uncropped size of the iPhone camera is retained.

Finally a really big problem surfaced. Due to the fast f3.9 focal ratio of the mirror, and perhaps inclusive of the subpar optical system, the focus could not be achieved over the entire region of the Moon. Thus focus had to be interpolated and approximated. Even a Bahtinov mask could not help this probem.

In conclusion, aside from the inherent problems with the Celestron FirstScope:

* Aspheric eyepieces with medium focal lengths do well with the f3.9 system
* Images are small and bright
* The focal reducer is working well
* The 2x Barlow is working well
* The telescope produces Moon images that are too bright for iPhone imaging
* The scope may have its place with deep sky objects

All experimental project Moon images were shot on the night of Friday, September 4th, 2020.

Celestron FirstScope - Index
https://otisastro.blogspot.com/2020/08/celestron-firstscope-index.html