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Tak FC100DL on Jupiter?

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#51 Scott99

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Posted 22 June 2016 - 10:29 AM

going beyond f/9 is tough - it's going to eliminate a lot more buyers.  I would love to see f/9 FC125 and 150's.  AP and TEC and others have used f/9 apos for lens designs with less than perfect color correction.  Still fits in a normal car but cleans things up better than f/7 or f/8.



#52 mgwhittle

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Posted 25 June 2016 - 05:20 AM

 

 

 

 

Then I will be waiting for the next limited edition of an hypothetical FC 120 DL  :grin:

The hypothetical bigger bother is actuall an FC125DL at F9.4.  .......

 


In order to maintain the same degree of color correction as the FC100/900 the hypothetical FC125 would have to be designed f/11.25! The corrsponding f.l. of 1400mm would be quite monstreous, wouldn't it?

It seems the 100/900 is a real sweet-spotter and substantially larger FCs will have to be either very long or then of lesser color-correction (because relatively shorter such as 125/1200) or alternatively (most probable!) not FC-design but 3-lensers again...

Chris

 

 

Well....Goto got close to this with a 1200mm fl 125mm scope.  They sold out very quickly.  I'd like to see Tak do a 1400mm length FC125.

 

http://gototelesco.c...25_1200apo.html

 

 

Hi Mark,

 

The GTL125/1200 APO is still available.  The one quickly sold out was GTM 100/1000APO.

 

Tammy

 

 

 

Thanks for pointing that out Tammy, I did have those two confused. Do you have any idea if it's possible to purchase the 125 for those of us here in the US?  



#53 Erik Bakker

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Posted 25 June 2016 - 06:51 AM

It's should be available to US buyers from APM Marcus Ludes in Germany. Last time I looked he had 1 in stock.



#54 junomike

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Posted 25 June 2016 - 07:25 AM

 

 

 

 

Then I will be waiting for the next limited edition of an hypothetical FC 120 DL  :grin:

The hypothetical bigger bother is actuall an FC125DL at F9.4.  .......

 


In order to maintain the same degree of color correction as the FC100/900 the hypothetical FC125 would have to be designed f/11.25! The corrsponding f.l. of 1400mm would be quite monstreous, wouldn't it?

It seems the 100/900 is a real sweet-spotter and substantially larger FCs will have to be either very long or then of lesser color-correction (because relatively shorter such as 125/1200) or alternatively (most probable!) not FC-design but 3-lensers again...

Chris

 

 

Well....Goto got close to this with a 1200mm fl 125mm scope.  They sold out very quickly.  I'd like to see Tak do a 1400mm length FC125.

 

http://gototelesco.c...25_1200apo.html

 

 

Hi Mark,

 

The GTL125/1200 APO is still available.  The one quickly sold out was GTM 100/1000APO.

 

Tammy

 

At almost $6000 USD it places it in a market with some very nice competition.

 

Mike



#55 Tamiji Homma

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Posted 25 June 2016 - 07:41 AM

 

Thanks for pointing that out Tammy, I did have those two confused. Do you have any idea if it's possible to purchase the 125 for those of us here in the US?

 

I think you can buy it directly from Goto like Markus did his.  After Brexit, yen gets stronger.  So Japanese goods are more expensive...

 

In case you missed this, here is Markus'GTL125/1200 APO test.

 

http://r2.astro-fore...achtung-perfekt

 

Tammy



#56 Erik Bakker

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Posted 25 June 2016 - 08:27 AM

From what I see, color correction in the GOTO 125mm is not up to the best fluorite doublets and the startest would cause me to return the specific instrument tested. For that money I want the best, period.



#57 mgwhittle

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Posted 25 June 2016 - 12:28 PM

From what I see, color correction in the GOTO 125mm is not up to the best fluorite doublets and the startest would cause me to return the specific instrument tested. For that money I want the best, period.

 

I'm seriously looking at this, although I'm not sure it's worth the price for me.  Could you be more specific about your concerns?



#58 Scott99

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Posted 25 June 2016 - 02:38 PM

I think it's fairly tank-like in construction, I remember the weight was high when I checked the specs.



#59 Erik Bakker

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Posted 25 June 2016 - 03:11 PM

Mark, let me explain what I meant:

 

For me, on the plus side, the OTA, lenscell and focuser look really nice.

 

However, if you look at the high power star images that includes red light, they are mush. If you look at the intra- and extra-focal star images, they are quite dissimilar. Only in a small portion of the spectrum, in green light, Strehl is high (0.98).

 

And mr. Rohr chooses his words very carefully when he describes it as a "sehr guter ED_APO führ visuelle beobachtung in der Nacht".

 

That one sentences has a few signal words in it:

1. ED_APO

2. visuelle

3. Nacht

 

Meaning: not so good color correction, but acceptable at night at low light-intensity levels where the out of focus colors dissipate into the blackness of the night sky. During the day it would make it's CA much more visible.

 

For comparison, have a look at the Tak FS128 test . And look at the FS102 test to see what a smaller aperture with the same f/8 speed can do. You'll see how they perform differently from the GOTO125.

 

All said, it still looks like a very nice scope, just as long as you have the right expectations.

 

For now, let's get back on track to the FC 100 DL. 



#60 mgwhittle

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Posted 25 June 2016 - 04:02 PM

Thanks Erik, I appreciate that detailed analysis.

#61 Disciplus55

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Posted 23 August 2016 - 03:41 AM

I've been fortunate enough to get a DL recently and last night, I did a side by side 2h30 comparison between my TSA 102N and the DL on Saturn, Izar, Arcturus, M11, M13, Rasalgethi, Mars a bit, Albireo, Gamma Del and Algedi... close doubles, colored ones, or planetary... All these with a prism Tak diagonal and Fujiyama orthos : 6 mm for the DL and 5 mm for the TSA, giving me both 150 or 156x magnification...

The DL with its original clamshell is 1.1kg lighter than the TSA 102N and takes between 10 and 15 minutes less to be on temperature.

But visually, except maybe a bit on Saturn, I couldn't not see any major difference... Maybe a tad more contrast on the TSA (background, sky, appeared darker), but I still wonder if it was not just my own perception/feeling rather than a real fact. Colors on Saturn seemed to be a tad whiter on the DL, but again, I could not detect any less/more details than on the TSA. Contrasted colors on colored double stars appeared to be easier to notice on the DL... All in all a massive headache to actually know which one is better/worse. I will try tonight on Venus maybe to see some color correction difference, and maybe Jupiter if possible... but so far, it's extremely close, and very subjective I think. Since I only do visual, I guess the weight difference and cooling time is what makes the DL more attractive to me.


Edited by Disciplus55, 23 August 2016 - 04:01 AM.


#62 Disciplus55

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Posted 23 August 2016 - 04:28 PM

Second evening of test, tried Venus and Jupiter, but both were way too low to see anything else than a poor seeing and atmospheric CA... Then back to Mars and Saturn, seeing was not as good as yesterday, so still a draw...



#63 John Huntley

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Posted 23 August 2016 - 05:57 PM

I'm pleased that you managed to find a DL Sylvain :)

 

I don't have another Tak to compare mine with - just my Vixen ED102SS. The Vixen is a nice refractor but the 100DL shows absoloutely no CA on anything at all and handles high magnifications a lot more effortlessly.

 

I really like it's light weight and virtually zero cool down time as well.

 

I imagine that a TSA would be very close in performance to the 100DL. Both superb 4 inch scopes just with some slightly different characteristics.



#64 RobM

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Posted 31 August 2016 - 01:55 PM

If using a Tak 1-1/4" prism diagonal and 1-1/4 EPs, could the Tak FC100DF be mounted on an AltAz like the Voyager or would a more robust mount be needed?  With the reduced tube diameter, I assume my 95mm machined rings and 10" vixen dovetail would be more than adequate?




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