Skywatcher ED Vs TS Optics Photoline.

[Greymouser]

I am considering a new, small refractor, to replace the 102 Star Travel that I have. Considering it needs to be portable, have considered the ED72 or 80, but find myself unsure which to go for. So is the TS Optics version better than the Skywatcher version, is the extra expense justified? I read that the TS is a better engineered option, as well as being easier to to transport, but what about the optics? I will be only using it for visual, at least for now.

The Skywatcher scopes are easy to find, so I will not link them, but here are the two TS options:

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p8637_TS-Optics-PHOTOLINE-80-mm-f-7-FPL53-Apo---2-5--Focuser.html
https://www.teleskop-express.de/shop/product_info.php/language/en/info/p8866_TS-Optics-Photoline-72mm-f-6-FPL53-Apo---2-5--Zahntrieb-Okularauszug.html

All opinions appreciated, thanks.

[Stu]

I do think the TS scopes are very well engineered. The focusers are very nice and the sliding dew shield helps with portability. TS specify fpl-53 glass whereas I don't think Skywatcher do on the 72mm. I've not seen direct comparisons between the 72mm scopes so can't comment on the differences. I know the SW ED80 is optically excellent though and haven't heard any negatives about the 72ED.

Personally I chose the TS72 because of its mechanics and the known glass in the optics .

[Ben the Ignorant]

Everything I've read about the Sky-Watcher 72 is good but to make things less subjective here is a Ronchi and defocus test (made by Teleskop Spezialisten):

 

The sharp lines in the Ronchi pattern mean the lenses have an excellent polish, and the fact they are straight means there are no aberrations due to their shape. The large defocus patterns have the same white color so no chromatic aberration to speak of. There is a very small zone in the middle of the small defocus patterns but it's negligible, and the very faint violet and green outer rings are the extremely low level of residual chromatism that all apos have to some degree. Overall an excellent lab test for the 72. Best of all, the rings inside the patterns have very nearly the same brightness, sharpness and color on both sides so none of that spherical aberration gremlin, the number one enemy of contrast.

I wish I could test all the telescopes myself but that's not possible 🙄. The TS scopes have a 2.5" rack-and pinion focuser that should slip less than the Crayford on the Sky-Watcher scope, and the larger drawtube will make for better illumination if you do imaging.

One last thing, if you go from a 102mm scope to a 72mm scope, the reduced brightness and resolution might disappoint you, so if I were you i'd take the largest smaller scope. The gain in tightness of focus will make for some of the loss in sheer amount of light.

[Greymouser]

Thanks for that. I am aware about the drop down in brightness and reach with the loss of aperture, but think I will cope with it. I also have a C5 and a C9.25 and to be honest prefer using the C5 as the contrast appears to be better. I have even considered even smaller options, ( 60mm? ) having a certain nostalgia towards the memory of my first scope, that I still have, but have not used in ages. I am also aware that the Skywatcher 80ED is a KG heavier than the TS one. Of course there are plenty of other options too, which is not that much of a help really. The Altair 80 ED-R is even lighter for instance.

The urge to get a decent refractor, will not stop here either, my intention was to get a 100mm refractor, but considered that came too close to my C5 in performance. Now my plan is to get a smaller one and in the future, perhaps far distant, get a 120mm one, or around that. Then maybe I will have a group of instruments to cover all bases and stop looking for that perfect scope.

Then again, does the search ever stop?

[fozzybear]

18 minutes ago, Greymouser said:

I also have a C5 and a C9.25 and to be honest prefer using the C5 as the contrast appears to be better

I also have an old C5 and love it and can agree contrast is good for a scope of this age if it was good enough for NASA then good enough for me

Edited November 3, 2019 by fozzybear

[Ben the Ignorant]

I also have a C5 😁. Had to recenter the secondary and the plate but now it's very sharp.

[Louis D]

If you plan to use heavy eyepieces or a binoviewer, get a rack & pinion focuser.  The Crayford-style focuser on my AT72ED slips under heavy loads as I point it close to zenith no matter how much I tighten the tension screw.  The Skywatcher focuser is generally considered worse yet.  Otherwise, it's a great wide field scope good to 100x without false color.  Above that, there is some fringing on bright objects thanks to its FPL-51 glass.  I've thought about trading up to the AT72ED II with FPL-53 glass and the R&P focuser.

Remember, extended object brightness is a function of exit pupil.  At the same exit pupil, an extended object will have the same brightness regardless of aperture, just different sizes.  Resolution will suffer with smaller apertures, but not extended object brightness as it relates to exit pupil.  It is true that point sources will appear brighter in larger aperture scopes than in smaller ones at equal exit pupils.  Smaller scopes actually work better for larger extended objects like the North America Nebula because it compresses the object down to a recognizable scale.  This also works for star clusters like Collinder 70 in Orion's belt.  It is unrecognizable as a cluster in larger scopes, but it really jumps out at you in smaller scopes.

[Greymouser]

10 hours ago, Ben the Ignorant said:

Had to recenter the secondary and the plate but now it's very sharp

I bet that was fun...

I have considered the 6" IOptron Photron Ritchey-Chrétien, to replace the C5, but think I might well regret it as my C5 is very good. I would probably find a replacement for the C9.25 first. 

Also the Altair 80ED-R has a rack and pinion, so that is decent. 

[R26 oldtimer]

I used to have an ST102 as my grab n go, which I sold when gold ED80 came up on the classifieds at a good price. Never regretted it and the fact that it was used but with great optics, made me feel easier on carrying it everywhere without the fear of scratching it.

I think there is a good priced ED80 on the sale section.

[Fedele]

The TS 80 has more backfocus

[paul mc c]

On 04/11/2019 at 20:15, R26 oldtimer said:

I think there is a good priced ED80 on the sale section.

😉

[scotty38]

1 hour ago, paul mc c said:

😉

He must have been psychic 🙂

[Louis D]

On 04/11/2019 at 13:08, Louis D said:

I've thought about trading up to the AT72ED II with FPL-53 glass and the R&P focuser.

Just a follow-up to myself.  I ended up getting a good deal on a used TS-Optics Photoline 90mm f6.6 Triplet FPL-53 APO for Christmas 2019.  It basically has no false color in focus, but out of focus images are tinged red and green on either side of best focus, so it's no reflector when it comes to color correction.  It is quite sharp at all powers, and the 2.5" R&P focuser has no slip issues at zenith even with heavy BV or 2" eyepiece and diagonal loads.  The fine focus is a bit spongy, so it's no Moonlight or FT focuser, but it's fine for visual observing.  I really like the camera angle adjuster at the end of the drawtube, so I can safely change the angle of the diagonal without changing the focuser knob orientation in the process.  Overall, it's a fun little scope to use once in a while.  I still prefer my 8" Dob for most observing, though.