Sky-Watcher Skymax-127 OTA Information (5" Maksutov-Cassegrain)

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

In progress

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.

Notes

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.

 

Look

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

Ditto

Diagonal mirror used by...

...the previous owner ...

...to build an angle finder

Better diagonal mirror (Lacerta) bought by the previous owner

Ditto

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

Ditto

Original Sky-Watcher diagonal mirror shown at Skymax-102

Collimation

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...

Skymax-127 on Heritage 100P base

Ditto

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

Ditto

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)

Ditto

 

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

Ditto

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

 

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

Telescope
Meade
Sky-Watcher Skymax/Heritage/Explorer
GSO
8" 10" ETX 90EC 102 127 76 100P 114P P130 150PDS GSD 680
Optical Design Newton
(Parabolic)
Newton
(Parabolic)
Maksutov-Cassegrain Maksutov-Cassegrain Maksutov-Cassegrain Newton (Spherical) Newton (Parabolic) Newton
(Parabolic)
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
f/6
1270 mm
f/5
1250 mm
f/13.8
1300 mm
f/12.7
1500 mm
f/11.8
300 mm
f/3.95
400 mm
f/4
500 mm
f/4.38
650 mm
f/5
750 mm
f/5
1200 mm
f/6
Resolving Power (arc secs) 0.56" 0.45" 1.3" 1.15" 0.95" 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

 

First Photo Attempts

In preparation

 

Visited Sky Objects

So far, I have visited (and documented...) the following sky objects with the Sky-Watcher Skymax-127:

 

Preliminary Conclusions

In progress

OTA

First attemots 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.

Bases

I will use the Skymax-127 OTA provisionally on the Heritage 100P base, though that's a bit wobbly (and shaky). I will, however, use it mainlyon the Star Discovery AZ GoTo mount, and maybe on a tripod for day (terrestrial) observations.

 

Links

 

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gerd (at) waloszek (dot) de

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10.12.2017