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Review & Comparison of Takahashi FS-128 & TEC 140


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Review & Comparison of Takahashi FS-128 & TEC 140

By William Rison

  FS-128 TEC 140
Manufacturer
Takahashi
Telescope Engineering Company
Country
Japan
USA
Year
1996 ?
2005
Serial number
96125
193
Objective diameter
128mm (5.0 inch)
140mm (5.5 inch)
Focal length
1040mm (f/8.1)
980mm (f/7.0)
Objective type
Fluorite Doublet APO
Aplanatic Oiled Triplet APO
Focuser type
Takahashi 2.7" rack & pinion with Starlight Instruments Micro Pinion
Starlight Instruments 3545 3.5" rotatable with TEC collet
OTA weight with tube rings, finder and diagonal
18.5 lbs
21.5 lbs
Tube diameter
145mm (5.7 inches)
150mm (5.9 inches)
Dew shield diameter
180mm (7.1 inches)
178mm (7.0 inches)
OTA length
44 inches (1118mm)
41 inches (1041mm)
34 inches (864mm) with dew shield retracted
Limiting magnitude
13.2
13.4
Resolving power
0.90 arc seconds
0.85 arc seconds

Fit and finish

FS-128 TEC 140
Paint is white enamel on the tube and green wrinkle on the focuser, lens cap, finder bracket and clam shell tube ring. I install a BT Quick Release bracket on the finder base for easy removal, the finder base bolts on normally. The dust cap fits on the inside of the dew shield with a felt liner. It does have a tendency to fall off it the scope is turned upside down and moved around a lot. There is also a 40mm threaded cover that removes from the dust cap for solar work, I put a piece of solar filter material on the back of this hold so I could focus on the sun and do daylight planet viewing. I find the clam shell tube ring easier to use than standard 2 knob tube rings. Like the large knob. White power coated on tube, best paint job I have ever seen on a scope. The latched tube rings are great. They allow quick release and hold of the OTA without having to worry about being too tight or too loose. The tension is adjustable but I found the factory setting is just right. I attached the tube rings to a Vixen dove tail bar that put the OTA lower to the mount. This allowed me to mount the heavier OTA without needing additional counterweights.

Lens cell and coatings

FS-128 TEC 140
Excellent coating dark blue in color in strong light. Lighting was very strong from a window the scope is pointing at. Push/pull lens adjustments. Dew shield unscrews from lens cell, this would help adjusting the lens greatly. This lens has be best coating I have ever seen on any telescope. The glass just seems to disappear. The lens cell is not adjustable. Dew shield retracts even with the lens cell and the dust cap locks in to the lens cell. This stops the dew shield from moving while transporting the scope.

Focuser

FS-128 TEC 140
When I first received this scope the focuser was stiff and had uneven areas of movement. The Starlight Instruments 3545 TEC focuser has the Astro-Physics finder bracket installed but I have not used it since I don't have a dovetail for that type of bracket. The focuser if fully rotatable by looseing the collet located at the OTA end of the focuser. The eyepiece end has a 2" collet for attaching a diagonal for any 2" piece of equipment. This works better than set screws or compression rings because it holds everything the same regardless of whether is has any type of undercut. I have had trouble using under cut and tapered cut diagonals on compression ring focusers.

Viewing

I set the two scopes up on my Astro-Physics 900GTO mount for the viewing comparisons.

Jupiter

FS-128 TEC 140
TMB 9mm Planetary eyepiece
The seeing was only fair for this comparison. Jupiter at 23┬░ above the horizon showed some false color in both scopes, very slight in the TEC 140 and slight in the FS-128. Detail on the planet showed very little difference, they were almost the same. The TEC 140 showed a brighter planet and this helped with seeing a little more detail. Color looked slightly warmer in the TEC 140 than the FS-128. The TEC 140 showed the sky to be a little blacker around the planet. False color around limb of Jupiter was a little more in the FS-128. More detail was seen in the TEC 140 but not much.
Takahashi 7.5mm LE eyepiece
Seeing excellent for this comparison. Jupiter was higher in the sky, 25┬░, than the previous viewing session. Both scopes showed excellent detail. It was hard to tell the difference in any area. Even false color was about the same, almost non existent in the FS-128 and none in the TEC 140. After the FS-128 has a doublet lens and the TEC 140 a triplet lens.
Conclusion
For planetary viewing either scope provides exceptional views. I have had nights when the views through the FS-128 were better than my Meade 12" LX200R. That's a big aperture difference but when seeing is not that good, which is not where I live, the FS-128 can outperform the LX200R. The same can be said for the TEC 140. If I had to give one scope a higher grade it would be the TEC 140 but not by that much.

Moon

FS-128 TEC 140
TeleVue 31mm Nagler, 27mm Panoptic, Vixen LVW 22mm, 17mm, 18mm eyepieces
No color around the moon's limb was visible in either the FS-128 or TEC 140. Depending on how I positioned my eye I could see some green around the limb, this was caused by the eyepiece.
Color, contrast and sky darkness around the moon was the same in both scopes.
Conclusion
I did fine the views of the moon in the FS-128 were a little more pleasing than in the TEC 140 when using low power eyepieces. I think this may be due to the slight increase in magnification when using the same eyepiece in both scopes. When I tried to study this and see what specific area was making me feel this way I could not find one.

Deep Sky

FS-128 TEC 140
Note
The above pictures were taken with different cameras so the scale is not the same.Left picture was with a Canon 20D ISO 400 4 minutes. Right was with Canon 1000D ISO 800 2 minutes. Both were processed using ImagesPlus.
M11 Star Cluster (Vixen 22mm LVW eyepiece)
More stars visible in the TEC 140. Both scopes showed absolute pin point stars across the entire field.
M17 (Swan) Emission Nebula (Vixen 22mm LVW eyepiece)
More nebula was visible in the TEC 140 but the sky background was also brighter.
M57 (Ring) Planetary Nebula (Vixen 13mm LVW eyepiece)
Brighter in TEC 140. Uneven brightness in ring visible in both scopes. Star to side visible in both.
M56 Globular Cluster (Vixen 13mm LVW eyepiece)
Much better in TEC 140.
M27 (Dumbbell) Planetary Nebula (Vixen 13mm LVW eyepiece)
Looked the same in both scopes. I could not tell any difference.
M15 Globular Cluster (TMB 9mm Planetary eyepiece)
Dimmer in the FS-128. Could resolve the same amount of stars in both.
Altair
Star test was perfect in both scopes. The in and out focus patterns were the same.
61 Cyg Double Star Mags. 4 & 9 Sep. 6"
Split easily in both scopes. Color was better in the TEC 140.
NGC6992 (Vail) Supernova reminet (Televue 31mm Nagler eyepiece)
Looked the same in both scopes even though the TEC 140 and more aperture.
Comet C/2006 W3 Christensen Mag. ~8
Slightly better in the TEC 140, not much difference.
Conclusion
The greater aperture of the TEC 140 gave it an advantage when viewing most deep sky objects. There were some tradeoffs however in my light pollutuded area with sky brightness being more in the TEC 140. What surprised me the most was the Vail looked the same in both scopes. For most deep sky objects more aperture is better and I found this to be so using the FS-128 and TEC 140. Open and Globular star clusters were noticeably brighter and more stars visible in the TEC 140. Nebula were about the same, this in part was caused by sky conditions.

  • Scott in NC, siriusarcher, AZStarGuy and 19 others like this


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