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

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

On this page, I present some information about my "planet" telescope (Maksutov-Cassegrain), a Sky-Watcher Skymax-102 OTA - 102 mm /1300 mm Maksutov-Cassegrain optical tube assembly (ordered on May 23, 2016, received on May 28 after collimation at the dealers'), which I also wanted to use at my Virtuoso base (in addition to the Heritage 114P Dobsonian tube that was delivered with the Virtuoso base). However, I returned the Virtuoso due to technical problems and got a refund. In spring 2017, I acquired a Sky-Watcher Star Discovery AZ GoTo telescope mount and now use the tube on this mount as well as on the Heritage 100P base.

The basic data was collected from the Teleskop-Spezialisten Website (in German), where I purchased the telescope.

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



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 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 tembles 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 is slightly too big, but 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, which 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...


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

Sky-Watcher Skymax/Heritage/Explorer
8" 10" 12" ETX 90EC 102 76 100P 114P P130 150PDS GSD 680
Optical Design Newton
Maksutov-Cassegrain Maksutov-Cassegrain Newton (Spherical) Newton (Parabolic) Newton
Newton (Parabolic) Newton (Parabolic) Newton (Parabolic)
Primary Mirror Diameter 203 mm 254 mm 305 mm 96 mm (90 mm) 102 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
1524 mm
1250 mm
1300 mm
300 mm
400 mm
500 mm
650 mm
750 mm
1200 mm
Resolving Power (arc secs) 0.56" 0.45" 0.38" 1.3" 1.15" 1.51" 1.15" 1.01" 0.9" 0.77" 0.58"
Limiting Visual Stellar Magnitude ca. 14 mag ca. 14.5 mag ca. 15 mag 11.7 mag 12.7 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 1898.5 165.3 212.3 117.9 204.1 265.2 344.9 459.2 816.3
Maximum Practical Visual Power ca. 550 x ca. 600 x ca. 700 x 325 x 204 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 40 cm x 144 cm 10.4 cm x 27.9 cm 10.4 cm x 27 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 15 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 21.3 kg n.a. 1.9 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


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


Visited Sky Objects

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


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. It may only happen that one day I will replace it with the slightly more powerful model with an aperture of 127 mm...


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.




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