Sky-Watcher Skymax-127 OTA Information (5" 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 second "planetary" telescope Sky-Watcher Skymax-127 OTA (BKM127OTA) (bought used on November 18, 2017; originally bought in August 2012). It is a 127 mm/1500 mm Maksutov-Cassegrain tube, which I want to use on my Sky-Watcher Star Discovery AZ GoTo telescope mount as well as possibly on the Heritage 100P base.


The Skymax-127 OTA is sold with the following accessories:

I purchased the tube used and without red dot finder and eyepieces, but with a better Lacerta diagonal mirror (99% transmission instead of 91%). In additions, I got the original diagonal mirror that was used to build an angle finder.



The Tube and more...

Skymax-127 in its package made by the previous owner plus a self-made angle finder

Tube taken out of the package


Diagonal mirror used by...

...the previous owner ... build an angle finder

Better diagonal mirror (Lacerta) bought by the previous owner


The previous owner removed the diagonal mirror and used it to build an angle finder. He replaced it with a better Lacerta diagonal mirror with better transmission (99% instead of 91%).

Lacerta diagonal mirror attached


Original Sky-Watcher diagonal mirror shown at Skymax-102


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


The main mirror of the Sky-Watcher Skymax-127 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

Actually, the 100P base is too small for the Skymax-127 tube. This is just a preliminary "quick-and-dirty" solution, until I get something that is better suited to the tube (the Heritage P130 base or the one from the Orion N 114/450 StarBlast 4.5 are probably suitable, but can regrettably not be purchased without tube).

Skymax-127 on Heritage 100P base


Ditto, rear view (see the collimation screws)

Skymax-102 on Heritage 100P base, front view


View into the telescope

The tube is mounted against the "official" viewing direction so that the finder is usable (I discussed this issue for the Skymax-102 at length...)

Telescope Tube on Star Discovery AZ GoTo Mount

Primarily, I 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 the GoTo mount


View from above - you can see the label indicating that Schott glass is used

Front view - you can clearly see the impractical position of the finder

Side view (overall view)

Seen from the back (overall view)

Skymax-102 tube on GoTo mount (overall view)



I will, as for the Skymax-102, 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-127 OTA can also be used on photo tripods, but it is bulky and already a bit heavy (> 3.4 kg with accessories). 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).

Here with red dot finder


Look of Skymax-127 OTA Compared with Skymax-102 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


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-127:


First Photo Attempts

Photos Through the Eyepiece (Projection Method)

First Moon Photo with the Camera Held to the Eyepiece

The following moon photo was taken on 22.2.2017 (one day before Half Moon). It was taken using the 1:50 method, that is, with the camera held to the eyepiece - in this case it was a Ricoh GR (28 mm equivalent). I used ISO 1600 and underexposed to prevent that bright areas are washed out.

I used a 32 mm Plössl eyepiece because otherwise I was not able to "catch" the whole moon.


Mit 32 mm-Okular (ca. 47 x) - 2000-Pixel-Version


Ausschnitt - 1400-Pixel-Version

Gleiches Bild größer, mit 32 mm-Okular (ca. 47 x) - 2000-Pixel-Version

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. My conclusion was that I only get really sharp photos with this combination under lucky circumstances, even exposure time did not matter too much provided that is was not too long (contrary to using this equipment on the Skymax-102...) - but the potential is there!

Conclusion: Only under fortunate circumstances I will get really sharp photos with this combination - but the potential is there! . 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 1/750 sec - 2700 pixels


Post-processed, exposure time 1/750 sec - 2700 pixels


Post-processed, exposure time 1/1500 sec, somewhat underexposed - 2700 pixels


Post-processed, exposure time 1/1000 sec, nevertheless blurry - 2700 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 above that has twice the exposure time...


Ditto; despite of only 1/1000 sec exposure time blurred...

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. Here are some sharper samples:


Sharp, but noisy because underexposed; such a sharp image was rare - 2400 pixels


Sharp - 2700 Pixel


The sharpest photo in this group - 2700 pixels


Northern section from photo above




Northern section from the photo above




Southern section from the photo above


Southern section from the photo above

Photos with Atik Infinity

Photos taken with Skymax-127 and 2 x focal reducer plus extension tube (results in about 3 x reduction) on Star Discovery AZ GoTo mount (Jan 14, 2018):


M 45 (Taurus), center, unprocessed


M 45 (Taurus), center, post-processed


M 31 and M 32 (top left, Andromeda), unprocessed


M 31 and M 32 (top left, Andromeda), post-processed

The following photos were created later from recordings:


M 45 (Taurus), center, from recording, unprocessed


M 45 (Taurus), center, from recording, processed


M 31 and M 32 (top left, Andromeda), from recording, processed


M 31 and M 32 (top left, Andromeda), from recording, processed, darker variant


M 31 and M 32 (top left, Andromeda), from further recording, processed


M 31 and M 32 (top left, Andromeda), from yet another recording, processed

Note that these photos show the complete image and that the large versions are in original size. This is due to the fact that the sky objects are extended - even beyond the field of view.


Preliminary Conclusions


First attempts by day and at the moon as well as comparisons with the Sky-Watcher Skymax-102 showed a similar performance for both tubes, with the Sky-Watcher Skymax-127 image appearing slightly brighter and more contrasty. My Astro dealer told me that the Skymax-102 shows the nicer image, but I was not yet able to confirm this.

It should also be noted that, in these comparisons, I cannot use identical magnifications or identical eyepieces. Also, the diagonal mirror of the Skymax-127 is of better quality (a Lacerta model with 99% reflectivity instead of 91%) because the previous owner added a better one. He built an angle finder from the Sky-Watcher diagonal mirror, which I have not used it so far.

I also compared both tubes using M 42, the Orion Nebula, on January 14, 2018. Both tubes showed the nebula nicely and dissolved the trapezium well, but I think that I was able to see the "wings" (see the photo below) a little bit better in the Skymax-127.

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

On February 6, 2018 I repeated this test because my astro-dealer wrote me that you could see differences between the two tubes using the Trapezium in M 42. I had not found any noticeable differences in that respect, and so I wanted to investigate this once more. Again, I was not able to find any noticlable differences in the visual impression of the Trapezium, but in the Skymax-127 the nebula itself seemed to be a little more differentiated than in the Skymax-102. Then I visited the open star cluster M 35 for another comparison and found that it seemed to be more contrasty in the Skymax-127 than in the Skymax-102. But the longer I looked at the object, the less I was able to see differences between the two tubes. All in all, however, I had the impression that the image was somewhat more contrasty and the stars were a little brighter in the Skymax-127 than in the Skymax-102. I also managed focusing better with the Skymax-127 than with the Skymax-102.

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.

All in all, I think that the Skymax-127 has a slight advantage over the Skymax-102 for deep sky objects. I do not know whether that is really reason enough to exchange the Skymax-102 for a Skymax-127, as many and I have done... In any case, the Skymax-102 iseasier to handle thanks to its smaller size and lighter weight. But both tubes still fit in the Sky-Watcher bag, which belongs to the 102-tubus and which I bought for my used 127 tube later. With accessories, the tubes weigh 4.3 kg and 2.8 kg each (but our balance is not accurate...).

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 will use the Skymax-127 OTA provisionally on the Heritage 100P base, though that's a bit wobbly (and shaky). The Heritage P130 base or the one from the Orion N 114/450 StarBlast 4.5 are probably suitable, but can regrettably not be purchased without a tube. Perhaps it may be possible to purchase a used base...

I will, however, use the Skymax-127 OTA mainly on the Star Discovery AZ GoTo mount, and maybe on a tripod for day (terrestrial) observations. Using this tube on a tripod is somewhat risky, I think, because of the fairly high tube weight.




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