Sky-Watcher Skymax-102 OTA Information (4" Maksutov-Cassegrain)

Look | Look on Different Bases | Basic Data | Visited Sky Objects | First Photo Attempts | Preliminary Conclusions | Links

On this page, I present some information about my "planetary" telescope, a Sky-Watcher Skymax-102 OTA (ordered on May 23, 2016, received on May 28 after collimation at the dealers'). This is a compact, fairly light-weight 102 mm /1300 mm Maksutov-Cassegrain tube, and I intended to use it on my Virtuoso base, in addition to the Heritage 114P Dobsonian tube that was delivered with the Virtuoso base. Due to technical problems, however, I returned the Virtuoso. In spring 2017, I acquired a Sky-Watcher Star Discovery AZ GoTo telescope mount and now use the Skymax-102 tube on this mount as well as on the Heritage 100P base.

Note: On a further page, I describe how I use the Skymax-102 on both mounts.

Note: In November 2017, I bought a used sample of the "bigger brother" of this telescope tube, Sky-Watcher Skymax-127 OTA (127 mm / 1500 mm), to get a little more "power" on the Star Discovery mount. I will therefore most probably sell this tube in due course. I might, however, also use it as a spotting scope on a photo tripod and bought a 45° Amici prism for terrestrial observations (which can, of course, also be used together with the Skymax-127...).



Unpacking, Bag

Outer package


Package dimensions :
Outer package: 57 cm x 25.5 cm x 24.5 cm
Innermost package: 53 cm x 21.5 cm x 21 cm

Gross weight : 4 kg, net weight: 3 kg (gross weight 4,5 kg according to DHL)



Outer package comparison with Sky-Watcher 114P Virtuoso


In-between package


Another box appears...

All packages on one photo!


Opening the inner-most box reveals a bag...

Bag taken out of the box

Small box with accessories unpacked

Accessories unpacked

Telescope tube taken auf of the bag

Ditto, the screwdriver points to the diagonal mirror...

Ditto with Heritage 100P base

Bag opened, you can see the cover for the content

Bag and cover for the content opened

Bag with tube, which is wrapped in protective plastic

Accessories: 10mm and 25mm eyepieces, red dot finder, diagonal mirror, and more


The 6 Allen screws for collimation at the rear end of the tube


The main mirror of the Sky-Watcher-102 OTA can be adjusted using 6 Allen screws, which are located at the rear end of the telescope. The small Allen screws are used for locking, the large ones for adjustment.

Instructions from Teleskop-Express (translated, original in German):

The collimation should be done directly at a star. Make it out of focus at a magnification of about 100 x. A dark shadow (the secondary mirror) should be exactly at the center. If it is not, you should adjust the telescope. Please proceed as follows:

  • First, loosen the (small) locking screws. The adjustment is not yet affected.
  • Then carefully adjust the primary mirror using the adjustment screws. Note that ¼ turn already has a clearly visible effect. Please adjust the mirror until the dark spot of the secondary mirror is exactly at the center.
  • Then fix the locking screws again.

The telescope is now collimated and will give you the best possible performance.

Look of Skymax-102 OTA Compared with Skymax-127 OTA

Das Skymax-102 is used on a Omegon Mini Dobsonian mount, which actually is too shaley for the tube...

Skymax-127 (left) and Skymax-102 (right), front view

Ditto, side view

Ditto, seen from the other side

Ditto, rear view

Ditto, oblique side view

Ditto, oblique view from side

Ditto, other view from the side

Ditto, rear view

Ditto, seen from the other side

Ditto, seen from the rear

The OTAs only

Ditto, front view

Skymax Tubes in Sky-Watcher Bag

Skymax-127 in bag

Ditto, bag open

Ditto, accessories visible

Skymax-102 in bag

Ditto, bag open, accessories in boxes can lie on the tube

Ditto, accessories removed

Ditto, the accessories can also be placed this way

Skymax-127 in bag, accessories next to or on tube

Both tubes with their accessories in their bags


Look on Different Bases

Telescope Tube on Heritage 100P Base

Skymax-102 on Heritage 100P base

Ditto, front view

Ditto, front view, closer

Skymax-102 on Heritage 100P base, other side

Skymax-102 on Heritage 100P base, seen more from the back

Ditto, details (focuser, diagonal mirror)

The tube is mounted against the "official" view direction. The locking knob for the tube was orientened so that the knob hit one of the three holes in the prism rail.

Telescope Tube on Omegon Mini Dobson Basis

As an alternative to the Heritage 100P base, I also use the tube on a simple Omegon Mini Dobson base.

Skymax-102 on Omegon Mini Dobson Base

Ditto, front view

Ditto other side


Ditto, rear view


The diagonal mirror hits the ground plate. You cannot rotate the tube complete - not a real prroblem...

Ditto, detail

Ditto, detail

The locking knob for the tube was orientened so that the knob hit one of the three holes in the prism rail. However, I found out that, when using the Omegon base, it is better to orient the locking knob towards the side of the prism rain that does not have holes.

Teleskop-Tubus on Heritage P130 Base

Since the tube tembled too much for may taste on the two small bases, I also tried the base of the Heritage P130 for the Skymax-102 OTA. This base appears slightly too big for the tube, but is somewhat more stable than the two other bases and thus, trembles a little less. For home use, this base seems to be a good solution, but for travel purposes, it is too big and unwieldy.

Skymax-102 on Heritage P130 base, side view

Ditto, other side

Dtito, rear view, detail

Ditto, rear view

Ditto, rear view, tube vertical

Ditto, rear view, tube horizontal

Ditto, front view

Ditto, front view, tube vertical

Ditto, front view, tube horizontal

The tube is mounted against the "official" view direction. The locking knob for the tube was orientened so that the knob hit one of the three holes in the prism rail.

Note: I gave the Heritage P130 away in mid-April 2017, so that I can no longer use this base for the Skymax-102 OTA.

Telescope Tube on Star Discovery AZ GoTo Mount

Last, but not least, I also use the tube on my Star Discovery AZ GoTo mount, and this regrettably results in an unusable position of the red dot finder*.

Skymax-102 tube on mount (overall view)

Ditto (Detail)

Front view - you can easily see the unusable position of the red dot finder

Skymax-102 tube on mount, turned around (overall view)

Ditto (detail) - you can easily see the unusable position of the red dot finder

Rear view


Ditto (detail) - you can easily see the unusable position of the red dot finder


I will have to find a solution for the finder positioning problem. What about a magnetic foot that still does not turn???

*) The OTA versions are meant to be used on an EQ mount and therefore do not fit optimally AZ mounts and Dobsonian bases.

Telescope Tube on Photo Tripods

The Skymax-102 OTA can also be used on photo tripods because it is compact and not too heavy. This is also recommended for daytime use, when you use the tube as a "spotting scope" (the image is upright, but reversed; an Amici prism would provide a "normal", that is, upright and correct, view).

Detail views of the tube on my old Revue tripod


Telescope Tube as A Spotting Scope

The Skymax-102 can be used as a spotting scope for terrestrial observations, although it is a bit large and heavy for such usage. For achieving an upright and correct image, an Amici prism can be used. I bought a Baader Amici prism with an angle of 45°, because this is more comfortable for terrestrial observations than 90° (Baader BA2956150 1.25"/45° Amici prism). With my 32 mm eyepiece, I get a magnification of about 40 x, with my 24 mm eyepiece, one of 54 x (my 24 mm eyepiece has a larger field of view, though, so that I get nearly the same true field of view...).The spotting scope is mounted to an old Revue photo tripod.

Photos: The Baader Amici prism

First Photo Attempts

Here are a few not very sharp first photo attempts with the Skymax-102 as a spotting scope, where I held the Sony RX100 M4 to the eyepiece (32 mm):

Photo data: November 28, 2017, ISO 1600, focal length 24 mm (equiv.)

Another Attempt...

Here, I mounted the Sony RX100 M4 fix to the eypiece (32 mm) using the Lensmate filter adapter and some more adapters:


Photo data: March 2, 2018, ISO 1600, focal length 50 mm (equiv.)

Note: In original size the photos do not look very sharp...

Third Attempt: At the Binshof Lakes Near Speyer


Photo data: March 4, 2018, ISO 800, focal length 52 mm (equiv.)

Note: In original size the photos do not look very sharp. Overall, the sharpness results are disappointing. The only somewhat sharper photo is the one that shows the heron.


Basic Data for Sky-Watcher Skymax-102 OTA (in Comparison)

Sky-Watcher Skymax/Heritage/Explorer
8" 10" ETX 90EC 102 127 76 100P 114P P130 150PDS GSD 680
Optical Design Newton
Maksutov-Cassegrain Maksutov-Cassegrain Maksutov-Cassegrain Newton (Spherical) Newton (Parabolic) Newton
Newton (Parabolic) Newton (Parabolic) Newton (Parabolic)
Primary Mirror Diameter 203 mm 254 mm 96 mm (90 mm) 102 mm 127 mm 76 mm (3") 100 mm (4") 114 mm (4.5") 130 mm (5") 150 mm (6") 200 mm (8")
Focal Length, Focal Ratio 1219 mm
1270 mm
1250 mm
1300 mm
1500 mm
300 mm
400 mm
500 mm
650 mm
750 mm
1200 mm
Resolving Power (arc secs) 0.56" 0.45" 1.3" 1.15" 0.91" 1.51" 1.15" 1.01" 0.9" 0.77" 0.58"
Limiting Visual Stellar Magnitude ca. 14 mag ca. 14.5 mag 11.7 mag 12.7 mag 13.2 mag 11.2 mag 11.8 mag 12.1 mag 13.3 mag 12.7 mag 14.5 mag
Light Gathering Power 841 1316.7 165.3 212.3 329.2 117.9 204.1 265.2 344.9 459.2 816.3
Maximum Practical Visual Power ca. 550 x ca. 600 x 325 x 204 x 254 x ca. 100 x (152 x) 150 x (200 x) 170 x (228 x) ca. 195/220 x (260 x) ca. 225 x (300 x) ca. 300 x (400 x)
Optical Tube Dimensions (diam. x length) 28 cm x 115 cm 35 cm x 119 cm 10.4 cm x 27.9 cm 11.6 cm x 27 cm 14.4 x 33 cm n.a. 11.5 cm x 37 cm* n.a. Tube collapsed < 37 cm
(14.5") long
18.2 cm x 69 cm
18 cm x 68 cm*
23 cm x 115 cm
Net Weight Basis 9 kg 12.2 kg n.a. --- --- n.a. 1.3 kg* 1.6 kg 3.1 kg* -- 11.2 kg
Net Weight Optical Tube 10.9 kg 17.2 kg n.a. 1.9 kg 3.4 kg n.a. 1.2 kg* 3.7 kg 3.25 kg* 5.0/6.0 kg
5.5 kg*
9.5 kg
Net Weight Complete 3.5 kg 1.75 kg 2.5*/2.8 kg 5.3 kg < 6.5 kg or 14 lbs. appr. 21 kg

Dark Blue: Telescopes that I still own; italic and dark red: telescopes that I owned; black: for comparison; *) own measurement


Visited Sky Objects

So far, I have visited (and documented...) the following sky objects with the Sky-Watcher Skymax-102:


First Photo Attempts

First Photos of the Venus Crescent with the Camera Held to the Eyepiece

On February 13, 2017, I tried to take some photos of Venus crescent with my Sky-Watcher Skymax-102 Maksutov-Cassegrain telescope. I used my Leica X Vario (1:50 method) for the photo and the following camera settings: manual mode, 1600 ASA, distance fixed to infinity.

100% crops; the photo to the right was taken with a longer focal length of the camera; Leica X Vario

First Photos of the Moon with the Camera Held to the Eyepiece

The following photos of the moon were taken at the beginning of April 2017 (April 2 and 4 just after its beginning; on April 3, it was half moon). They were taken using the 1:50 method, that is, with the camera held to the eyepiece. In this case, I used my Ricoh GR (28 mm equivalent) at ISO 1600 and underexposed to avoid flare.

I used a 16 mm UWA and a 32 mm Plössl eyepiece. With the former, I was able to see the full moon, but not to "catch" it.

Regrettably, the photos are not as sharp as the ones that I took using the Sky-Watcher Explorer 150PDS at the same time.

April 2, 2017


32 mm eyepiece (approx. 40 x) - 1600 pixels version


32 mm eyepiece (approx. 40 x) - 1600 pixels version

16 mm eyepiece (approx. 81 x) - 3200 pixels version

April 4, 2017 (Just after its Beginning, Half Moon on April, 4)

16 mm eyepiece (approx. 81 x) - 3200 pixels version

April 4, 2017


32 mm eyepiece (approx. 40 x) - 1600 pixels version B&W


32 mm eyepiece (approx. 40 x) - 1600 pixels version B&W

Comparison of the Days


April 2, 2017


April 4, 2017 (just started, half moon)

  April 4, 2017

Photos of the Moon with Camera Screwed to the Eyepiece

On February 27, 2018, I took a series of moon photos with my Leica M (Type 240) and a Minolta 28 mm lens attached to the eyepiece. Most of the resulting photos were, however, blurred. In order to investigate the conditions for the camera shake more closely, I varied the exposure times. In contrast to the Skymax-127, I got the relatively clear result that shots under 1/1000 sec exposure time are mostly blurred. For 1/1000 sec and shorter, I am often lucky that they are sharp. Even shorter exposure times lead to underexposure and would have to be compensated by a higher ISO number (I already used ISO 3200). Neither underexposure nor a higher ISO number increase the quality of the photos...

Conclusion: Only with very short exposure times do I get really sharp photos with this combination, and typically, that is rarely the case. The potential is there, but the results with the Skymax-127 seem to be slightly better than those with the Skymax-102. This may, however, also be due to the selected images or just coincidence... Here are some selected sample photos:


Post-processed, exposure time 1/1000 - 2400 pixels


Post-processed, exposure time 1/1000 - 2400 pixels


Post-processed, exposure time 1/1500, somewhat underexposed - 2400 pixels


Post-processed, exposure time 1/500, blurred - 2400 pixels


Section from the southern hemisphere, my sharpest sample


Ditto; same exposure time, but less sharp


Ditto; more noise due to underexposure and less sharp than the photo abov...


Ditto; blurred, because of 1/500 sec exposure time ...

Photos Using a T-Mount Adapter

On February 23, 2018, I attempted to take photos of the moon covering Aldebaran, using my Skymax-127 OTA and my Leica M (Typ 240) connected by a T-mount adapter. The telescope is used as a camera lens (1500 mm, f/11.8) for this type of mounting. The results are described elsewhere and are overall disappointing, because almost all images are blurred despite using a cable release.

I took only a few photos of the moon with the Skymax-102, because it quickly became clear that these were not satisfying, even though it looked like this in the viewfinder at first, i. e. as if the photos were sharp. But despite or because of using a cable release, the photos are not sharp. However, unlike with the Skymax-127, it seems to be a problem of focusing rather than shake (although double contours appear on a few photos). Why the photos are so blurred, although they looked sharp in the viewfinder during quick review, is beyond my knowledge....


Original view


Original view


Section of the photo above


Section of the photo above


Preliminary Conclusions


The Skymax-102 OTA is a Maksutov-Cassegrain tube and thus, plays in a somewhat "different league" than my Dobson telescopes (or Newton tubes). It is small and handy and weighs about 2 kg, which makes it feel surprisingly heavy. While I can not find that its optical performance is better than that of Newtons or Dobsons, as is often claimed and will certainly be true, I see its main advantage in the combination of high magnification with compact dimensions and a reasonable weight. It is therefore a typical "moon, sun, and planet" telescope, and I bought it, following a dealer's recommendation, exactly for this purpose. In contrast to the, in this respect, disappointing Meade ETX 90/EC, I was also also to observe some brighter deep-sky objects. All in all, this tube fills a gap in my telescope collection and fulfills a special task that cannot be performed by Newton tubes equally well. I was, however, thinking about replacing it one day I with the slightly more powerful model with an aperture of 127 mm, als my astronomy suggested as a possible way to "optimize" my telescope collection (but later he withdrew this...). And exactly this happended in November 2017, when I bought a used Skymax-127 OTA!

Compared with the Skymax-127 OTA, it proved difficult to me to find differences between the two tubes, especially since the conditions were never exactly comparable. With the Orion Nebula M 42, however, the Skymax-127 seemed, in my impression, to have a slight advantage: the nebula cloud seemed to be somewhat more differentiated and the "wings" (see the foto below) could be seen more clearly:

Photo: Photo of M 42/43 with Atik Infinity (B&W version) with Explorer 150PDS

I did a further comparison using the open star cluster M 35. In the Skymax-127, the star cluster seemed to me more vivid and more contrasty at first, but when I looked longer through the eyepieces, the visual impression became very similar in both tubes.

At the end of February 2018, I photographed the moon with both Skymax tubes in different configurations. Apart from the problems of camera shake when the Leica M (type 240) was fixed to the telescope or eyepiece, the few sharp results were fine and comparable, although I got the impression that the Skymax-127 has a slight edge, particularly, since it produces a somewhat larger image due to the longer focal length. The latter was fine for my 32 mm eyepiece, to which I can attach a camera with a T-mount adapter.

Overall, I think that, for deep sky objects, the Skymax-127 has a slight advantage over the Skymax-102. The latter is, however, much easier to handle thanks to ist smaller size and lower weight. Both (the 127 just so ...) fit the Sky-Watcher bag, which is delivered with the 102 and which I bought for my used 127 tube afterwards. With tubes and accessories, the bags weight 2.8 kg or 4.3 kg (but our balance is not exact...).

Note: I discuss this on the Skymax-127 page in more detail.

Skymax-127 in bag, accessories in front compartment

Skymax-102 in bag, accessories can lie on tube

Both tubes in their bags with accessories


I tried the Skymax-102 OTA on four different bases and came to somewhat different results than I had initially assumed. Since the Skymax-102 tube is significantly heavier than the Heritage 100P tube and also magnifies more than three times more with the same focal length of the eyepiece, the trembling of the small bases is more noticeable with this tube. Therefore, whenever I want to do without GoTo, I would always use the more stable P130 base at home (even if it is still not free of trembling). But since I gave the P130 away in mid-April 2017, this option no longer does exist and I have to stick to the 100P base...

On holidays, on the other hand, I would choose the 100P basis anyway because of the lack of space. The Omegon base is more or less superfluous, unless I also take the Heritage 100P tube with me. If I want to use the tube with GoTo, the Star Discovery AZ GoTo mount comes into play. This will, however, only be the case at home.

Use on Tripods and as A Spotting Scope

The Skymax-102 OTA can also be used on photo tripods because it is compact and not too heavy. This is also recommended for daytime use, when you use the tube as a "spotting scope" (the image is upright, but reversed). An Amici prism provides a "normal" view, and therefore I bought one for terrestrial observations.




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