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Tak Fc 100 series question

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#1 SRZ

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Posted 03 June 2020 - 10:38 PM

Hello all,

I am considering a 4 incher Tak for high power lunar and planetary in a compact package with quick cool down time purposes. However, I am concerned about the exit pupil such a small aperture would allow. At what point in magnification does it start to get bothersome? I tried lunar on my 80mm triplet and it seemed like an exit pupil of 0.41 (192x) would be the tolerance limit for me.
Can a superior quality scope increase this tolerance level? Or can the fluorite do something magical that it is not that bothersome at high powers?

Thanks

#2 nicknacknock

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Posted 03 June 2020 - 10:40 PM

Floaters are not related to the scope quality. It’s a function of exit pupil and the condition of our eyes. Easy workaround: binoviewers!
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#3 db2005

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Posted 04 June 2020 - 12:19 AM

At around 0.5 mm exit pupil or less I find the views less comfortable, and I normally prefer exit pupils larger than that. One advantage of a small exit pupil, however, is that eye astigmatism becomes much less of a problem.

 

There is nothing magical per se in Tak's scopes or in the use of fluorite. However, an instrument of world-class optical quality (like those of Tak and a few others) will show you text-book perfect diffraction discs and text-book perfect splits of challenge double stars, and visual contrast will be noticeably better than optics of inferior quality. As a point in case, many of the artifacts that I have previously frequently attributed to seeing issues (unclear splits of double stars, low-contrast views of planets, rough or spiked diffraction discs, spherical aberration, etc.) began to "magically" disappear as soon as I began using high quality instruments. Optical quality is a Real Thing and the eyes will notice the difference more and more as you increase the magnification.


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#4 Hesiod

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Posted 04 June 2020 - 12:38 AM

As already noted, the exit pupil treshold will not ne affected; however, going to a 100mm aperture would make for a substantial increase in magnification and detail from the 80mm while being still a very "quick" telescope to handle.
Having nice optics can not "heal" the stargazer' eyes issue but, at least, will not add further ones...
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#5 SRZ

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Posted 04 June 2020 - 08:44 AM

Thanks all!

 

Floaters are not related to the scope quality. It’s a function of exit pupil and the condition of our eyes. Easy workaround: binoviewers!

I am trying to keep the setup as light as possible, is there a way to workaround other than binoviewers, like a powermate?


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#6 rerun

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Posted 04 June 2020 - 09:22 AM

With my TAK FC100DF I use Nagler eyepieces. The Nagler 3,5mm @ 210x gives an exit pupil 0,39 ~ 0,4 . This gaves me very good views for moon and planets.  For double stars no problem too. 

I don' t have the nagler zoom 3-6mm you own ,but I think it will work too with an 100mm scope.

 

Clear skies Markus 


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#7 sunnyday

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Posted 04 June 2020 - 09:29 AM

Floaters are not related to the scope quality. It’s a function of exit pupil and the condition of our eyes. Easy workaround: binoviewers!

I have this problem too.
and with a bino it goes away?

How do you explain to me?
thank you.


Edited by sunnyday, 04 June 2020 - 09:30 AM.

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#8 nicknacknock

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Posted 04 June 2020 - 09:32 AM

Your brain can compensate somewhat due to feedback from both eyes. I can go from about 0.45mm exit pupil cyclops mode to 0.3mm and slightly less Exit pupil with Binoviewers
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#9 sunnyday

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Posted 04 June 2020 - 09:38 AM

Your brain can compensate somewhat due to feedback from both eyes. I can go from about 0.45mm exit pupil cyclops mode to 0.3mm and slightly less Exit pupil with Binoviewers

thanks Nick



#10 nicknacknock

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Posted 04 June 2020 - 09:49 AM

With my TAK FC100DF I use Nagler eyepieces. The Nagler 3,5mm @ 210x gives an exit pupil 0,39 ~ 0,4 . This gaves me very good views for moon and planets. For double stars no problem too.
I don' t have the nagler zoom 3-6mm you own ,but I think it will work too with an 100mm scope.

Clear skies Markus


Markus,

I was at 240x with the FS-102 on the moon with binoviewers and I shifted to 318x. Binoviewers rock!

#11 nicknacknock

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Posted 04 June 2020 - 10:02 AM

Thanks all!

I am trying to keep the setup as light as possible, is there a way to workaround other than binoviewers, like a powermate?


Exit pupil will decrease as it is a function of magnification and scope diameter. So, either a larger telescope or binoviewers...
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#12 rerun

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Posted 04 June 2020 - 10:14 AM

Markus,

I was at 240x with the FS-102 on the moon with binoviewers and I shifted to 318x. Binoviewers rock!

Nick,

 

318x is very high , but sometimes the seeing is so great , you need to find eyepieces and barlows to reach these high magnifications.

 

Yes I like binoviewing ,too .The new Baader Maxbright II Binoviewer  is great ,the views with the FC 100 were amazing and very relaxing. Something everyone should try on his scope.

 

Clear Skies

 

Markus


Edited by rerun, 04 June 2020 - 10:14 AM.

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#13 coopman

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Posted 04 June 2020 - 06:43 PM

If you want more magnification but no floaters, aperture is your friend. Double the aperture in mm to determine the mag. for a 0.5mm exit pupil, which is when many of us start to have floater problems.
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#14 Lookitup

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Posted 04 June 2020 - 09:48 PM

+1. The ED120 I had let me use x240 comfortably if conditions allowed. The Tak FC100 DF exit pupil get's to small for me above x200 unless viewing doubles. Use binoviewer only and still have floaters above x170 and astigmatism under x100. Had to choose between the two, I happily picked the Tak due to "crisper" optics, much lighter weight and faster cooling. Cheers



#15 nicknacknock

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Posted 05 June 2020 - 12:40 AM

Nick,

 

318x is very high , but sometimes the seeing is so great , you need to find eyepieces and barlows to reach these high magnifications.

 

Yes I like binoviewing ,too .The new Baader Maxbright II Binoviewer  is great ,the views with the FC 100 were amazing and very relaxing. Something everyone should try on his scope.

 

Clear Skies

 

Markus

 

Markus, I use the ES 6.7mm and Baader 2.6x GPC to get to that level of magnification. My seeing conditions regularly support up to that (it is really the upper limit on most occasions).

 

I will also note for the benefit of all who read this. The scope and eyepieces are one part of the equation. The other key part, is a solid tripod and mount combo, otherwise you are sort of shooting yourself on the foot.


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#16 fate187

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Posted 05 June 2020 - 12:51 AM

I also use a bino with 7mm delites and 1.7GPC with my Tak 100. This is not the limit I think, but I only have one 5mm Delite ;).

In mono I barlow my Vixen HR 3.4 2x or even 3x on doubles... 


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#17 rerun

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Posted 05 June 2020 - 09:54 AM

I use the bino with 1,7x GPC too and with 20mm ,15mm and 11mm eyepieces. I own a ES 6,7mm too and like it very much , buying another is an option for me. For mono views I have the following ep's 27mm Panoptic and 11, 7 , 5 and 3,5mm Nagler. I  am surprised how often I can use this 3,5mm eyepiece. I don ' t expect that this will happens when I bought it. For most of my observation I use the 7mm Nagler .

 

Clear skies Markus 



#18 nicknacknock

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Posted 05 June 2020 - 10:57 AM

I think you are just above the level where floaters begin to interfere. Certainly the 3.5mm is eminently usable with your Tak. But you can squeeze a lot more from that scope!

 

i noticed that the only 2” eyepiece you use is the 27mm Panoptic. If I may ask, why that and not a 24mm Panoptic to keep all 1.25” (easier to balance, lighter setup) since the magnification / exit pupil don’t change that much?



#19 rerun

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Posted 05 June 2020 - 12:56 PM

I got it for a good price and I had the Panoptic 27mm eyepiece first ,before I bought all the other Tele Vue eyepieces and I used it with different scopes. And it is really not a problem balancing it on the AYO II mount or on the Vixen GPD. 

 

A good barlow or a Vixen HR 2,4 mm or Takahashi TOE 2,5mm eyepiece were something to look at for the future.

 

Clear skies

 

Markus


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#20 RAKing

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Posted 05 June 2020 - 01:55 PM

i noticed that the only 2” eyepiece you use is the 27mm Panoptic. If I may ask, why that and not a 24mm Panoptic to keep all 1.25” (easier to balance, lighter setup) since the magnification / exit pupil don’t change that much?

 

I also carry the 2" 27 Pan instead of the 24 Pan and the reason is eye relief.  The Panoptics scale eye relief as the focal length increases.  Unfortunately, the 24 Pan only has 15mm eye relief, which is a little tight for me now.  The 27 Pan is much more comfortable with 19mm eye relief.

 

Back to the main topic - I regularly use a 3.5mm eyepiece with my FC-100 and I use a Zeiss Barlow with a 6mm Delos when sky conditions allow.  In my f/8 Tak, that puts me at 267x, which is 67x the aperture.  The exit pupil is small at 0.38mm, but the view is still great when I do it.  And yes, I have quite a few floaters in my viewing eye -- but I have learned to work around them over the years.

 

The main thing to remember is the better your optics, the more options you have to get a decent view.  It doesn't matter if you are running mono or bino.  A good quality 4-inch refractor can show a lot of stuff.

 

Cheers,

 

Ron


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#21 gwlee

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Posted 05 June 2020 - 02:29 PM

Hello all,

I am considering a 4 incher Tak for high power lunar and planetary in a compact package with quick cool down time purposes. However, I am concerned about the exit pupil such a small aperture would allow. At what point in magnification does it start to get bothersome? I tried lunar on my 80mm triplet and it seemed like an exit pupil of 0.41 (192x) would be the tolerance limit for me.
Can a superior quality scope increase this tolerance level? Or can the fluorite do something magical that it is not that bothersome at high powers?

Thanks

I find that my eyes prefer looking through scopes with exit pupils larger than 1mm, so I try to avoid using exit pupils smaller than about 1mm with any scope regardless of its pedigree. 


Edited by gwlee, 05 June 2020 - 07:02 PM.


#22 Spikey131

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Posted 05 June 2020 - 06:57 PM

Hello all,

I am considering a 4 incher Tak for high power lunar and planetary in a compact package with quick cool down time purposes. However, I am concerned about the exit pupil such a small aperture would allow. At what point in magnification does it start to get bothersome? I tried lunar on my 80mm triplet and it seemed like an exit pupil of 0.41 (192x) would be the tolerance limit for me.
Can a superior quality scope increase this tolerance level? Or can the fluorite do something magical that it is not that bothersome at high powers?

Thanks

The Tak FC100 series are fine doublet 4” telescopes, but there is nothing magical:  4 inches is 4 inches.  This size telescope is limited by physics for “high power lunar and planetary” observing.

 

Your 12” dob should perform much better at higher magnifications with more resolution and larger exit pupils.  So will an 8” SCT.


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#23 gwlee

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Posted 05 June 2020 - 07:44 PM

Thanks all!

 

I am trying to keep the setup as light as possible, is there a way to workaround other than binoviewers, like a powermate?

Nope. 200x in that scope gives about 1/2mm exit pupil whether you get there with a prime EP, or a prime EP+Barlow.

 

A bino viewer will compensate for floaters to some extent, but will cost you about $1000 for a good one, introduce weight and balance problems, and you will need twice as many EPs in addition. That’s not what I consider a simple solution. BTW, more vision problems than floaters are effected by exit pupil size, astigmatism for example.
 

To double magnification without decreasing exit pupil size, I must double my aperture size,  so I swap OTAs rather than EPs when I hit my exit pupil limit with a 4” scope. The good news is an 8”f6 reflector sells for less than $400, and gathers 4x as much light and offers twice the resolution of a 4” scope. 

 

 

 

 



#24 BillP

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Posted 05 June 2020 - 08:07 PM

Hello all,

I am considering a 4 incher Tak for high power lunar and planetary in a compact package with quick cool down time purposes. However, I am concerned about the exit pupil such a small aperture would allow. At what point in magnification does it start to get bothersome? I tried lunar on my 80mm triplet and it seemed like an exit pupil of 0.41 (192x) would be the tolerance limit for me.
Can a superior quality scope increase this tolerance level? Or can the fluorite do something magical that it is not that bothersome at high powers?

Around a 0.4mm exit for the Moon is generally what I like also, although with my 4" Apo.  However, what works on the Moon does not work on the planets, at least not all of them.  Jupiter in particular where more like a 0.65mm is the lowest I like to go as anything lower generally means I will be losing low contrast details as just too dim for that planet.  Saturn can take more easily but not much of an subtle details on Saturn, at least not with a 4".  Mars is an exception as it is very bright being so much closer to the Sun and feel that it can also handle a 0.4mm exit easily with a 4" scope...I've actually had some very successful observations of Mars in my 4" even at a 0.32mm exit pupil -- yest the low contrast fringe details of many of the Mare will be lost, but for that planet I felt worth it to get some good image scale.


Edited by BillP, 05 June 2020 - 08:08 PM.

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#25 Spikey131

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Posted 05 June 2020 - 08:23 PM

A Willam Optics binoviewer kit with 2 eyepieces and a Barlow is less than $300.  

 

I think most of us would agree that it is a good one, even if is not the best one made.


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