59 replies to this topic

[Scott in NC]

Hey folks, I haven't done any DPAC testing for a while, but today I'm going to present the results of my recently acquired Takahashi TSA-120N.  For a variety of reasons I haven't yet been able to take this outdoors to test it under the stars, but this morning I had some free time to DPAC test it.  This is a 120mm f/7.5 apochromatic triplet, with the middle element composed of FPL-53.  In 2019 Takahashi produced 40 of the "N" version, with a fixed dew shield, and I have sample #27.

 

Here's the scope set up on my testing table:

 

 

 

[Scott in NC]

Green inside / outside focus:

 

 

Red inside / outside focus:

 

 

Blue inside / outside focus:

 

 

White inside / at / outside focus:

 

 

[rolo]

To me, it looks about as good as it gets but you can always split gnat hairs though.

[Scott in NC]

I'm pretty pleased with these results.  Green is so extremely slightly over corrected and red is so extremely slightly under corrected that for all practical purposes I'd consider those colors to be near perfect.  Blue has a slightly greater degree of over correction, but still quite good IMO.  The white light images, which are a very harsh test for chromatic aberration, show extremely minimal blue fringing near the edges.  I've yet to see a refractor (no matter how good) that didn't show at least a tiny amount of color fringing, although I've yet to test a Takahashi TOA-130 or -150, both of which have two ED elements and wide air gaps. If any refractor could possibly show no false color on DPAC testing, then those would be potential candidates.  I suspect that with the right settings I could provoke slight false color while testing those scopes, but I can't say that with 100% certainty. Maybe one day I'll be able to test a TOA, but will have to borrow one to do so, as those scopes aren't in this year's budget.

[Daniel Mounsey]

Nice work Scott. looks good.

[wrvond]

Very impressive!

Also, I want to acknowledge your generosity allowing your wife to occasionally use your test bench.

[SandyHouTex]

Green inside / outside focus:

 

IMG_8915 green inside.JPG

IMG_8919 green outside.JPG

 

Red inside / outside focus:

 

IMG_8915 red inside.JPG

IMG_8919 red outside.JPG

 

Blue inside / outside focus:

 

IMG_8915 blue inside.JPG

IMG_8919 blue outside.JPG

 

White inside / at / outside focus:

 

IMG_8915.JPG

IMG_8918.JPG

IMG_8919.JPG

 

I don't think you can get any better than that.  I have the same TSA-120N.  It's a great scope.

[Jethro7]

Hello Scott,

Congrats on the TSA 120 N, I've never had my TSA 120 tested but mine puts up outstanding views.

 

HAPPY SKIES AND KEEP LOOKING UP Jethro

[Scott in NC]

Hello Scott,

Congrats on the TSA 120 N, I've never had my TSA 120 tested but mine puts up outstanding views.

 

HAPPY SKIES AND KEEP LOOKING UP Jethro

I imagine they're pretty consistent in quality.  It looks like mine is going to be a keeper, for a while at least. It will make another scope of mine redundant, so I may end up having something for sale before too long, but right now I don't have the energy for any more buying or selling.  Maybe one day this coming fall or winter.

[Jeff B]

I'm pretty pleased with these results.  Green is so extremely slightly over corrected and red is so extremely slightly under corrected that for all practical purposes I'd consider those colors to be near perfect.  Blue has a slightly greater degree of over correction, but still quite good IMO.  The white light images, which are a very harsh test for chromatic aberration, show extremely minimal blue fringing near the edges.  I've yet to see a refractor (no matter how good) that didn't show at least a tiny amount of color fringing, although I've yet to test a Takahashi TOA-130 or -150, both of which have two ED elements and wide air gaps. If any refractor could possibly show no false color on DPAC testing, then those would be potential candidates.  I suspect that with the right settings I could provoke slight false color while testing those scopes, but I can't say that with 100% certainty. Maybe one day I'll be able to test a TOA, but will have to borrow one to do so, as those scopes aren't in this year's budget.

Well done Scott and remember, what very little you see here is actually twice the reality.  

 

On to the visual assessment!  Can't wait sir.

 

Jeff

[Stellar1]

You can't ask for better than that, that's great! +1 for Tak QC i wish I could do the same with my 102, just for the heck of it.

Edited by Stellar1, 12 August 2023 - 11:22 AM.

[Scott in NC]

 

On to the visual assessment!  Can't wait sir.

 

 

Thanks, Jeff!  Now I just need the right combination of weather and free time.

[AstroApe]

Excellent test results!! Definitely showing that Takahashi optical quality.

 

BTW, those silver rings look pretty slick on that scope! Me like

[Bill Barlow]

The optics look like typical Takahashi quality.  Let us know when you get a chance to actually observe with it and give your impressions.  I think if I were interested in a larger high quality refractor not to exceed 5” this Tak 120 would probably be at the top of the list.  

 

Bill

Edited by Bill Barlow, 12 August 2023 - 11:39 AM.

[Scott in NC]

 

BTW, those silver rings look pretty slick on that scope! Me like

They’re from K-Astec, and appear to be very lightweight yet sturdy.

[dweller25]

The FS128 and AT125 have a tough act to beat Scott - looking forward to your visual assessment 

[CHASLX200]

Good enough to do 100x per inch.

[TEK]

I have had a TSA-120 since February and have thoroughly enjoyed every moment I have had to observe with it.  It's encouraging to see the test results you were able to report.  Thanks for taking the time to perform the tests and post the results - look forward to seeing more.

[sdedalus83]

I'm pretty pleased with these results.  Green is so extremely slightly over corrected and red is so extremely slightly under corrected that for all practical purposes I'd consider those colors to be near perfect.  Blue has a slightly greater degree of over correction, but still quite good IMO.  The white light images, which are a very harsh test for chromatic aberration, show extremely minimal blue fringing near the edges.  I've yet to see a refractor (no matter how good) that didn't show at least a tiny amount of color fringing, although I've yet to test a Takahashi TOA-130 or -150, both of which have two ED elements and wide air gaps. If any refractor could possibly show no false color on DPAC testing, then those would be potential candidates.  I suspect that with the right settings I could provoke slight false color while testing those scopes, but I can't say that with 100% certainty. Maybe one day I'll be able to test a TOA, but will have to borrow one to do so, as those scopes aren't in this year's budget.

There’s also the Goto F15 dual ED super apochromats, 

[Scott in NC]

There’s also the Goto F15 dual ED super apochromats, 

Wow--now those might actually be color free on DPAC testing, assuming the design is well executed.  I've never seen one, and suspect I'd need a longer dining room table to test one. If I ever come across one, I'll have to ask my wife where we put the extra leaf for the table!

[sdedalus83]

Wow--now those might actually be color free on DPAC testing, assuming the design is well executed.  I've never seen one, and suspect I'd need a longer dining room table to test one. If I ever come across one, I'll have to ask my wife where we put the extra leaf for the table!

https://koji-matsumo... APO/index.html

 

They were made in up to 250mm aperture. PawPaw has some information on what they actually produced, the big ones were in the low single digits.

[Jeff B]

Thanks, Jeff!  Now I just need the right combination of weather and free time.

And good luck with both of those.....

[stevew]

Wow! Essentially perfect...

Congratulations...

[Scott in NC]

https://koji-matsumo... APO/index.html

 

They were made in up to 250mm aperture. PawPaw has some information on what they actually produced, the big ones were in the low single digits.

Thanks for the link, as I don't believe that I had ever heard of these before.  Now if I ever come across an 80mm version, I could easily fit that on my dining room table.  I doubt I could even lift the 250mm version, so that's another story!

[bobhen]

When I bought my TSA 120 or most of my other scopes for that matter, no one was doing DPAC tests. It's nice to see that with some experience, using the star test and studying Jupiter in good seeing that my evaluations have been extremely close to these tests. 

 

Visually, I've never seen color with the TSA 120, not even in the star test.

 

Bob