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Tak FSQ-85: Will it work well with binoviewer?

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#26 trias702

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Posted 22 May 2020 - 09:50 AM

Hi there,

I may pass you my experience with a Sky90-II; not the same OTA, but same issue.

Once I upgraded the 2.5" original focuser to the FSQ-85 3", basically giving birth to a novel Sky90-III, I was also faced with a short backfocus concern, despite having a SV version. This because, obviously, the FSQ-85 focuser is larger/longer than the original Sky-90 one (see pix).

No problem, of course, with mono-view, or with a bino using the Ext-Q 1.6x or any OCS. But, using the bare (no-OCS) Mark-V, with the short Baader/Zeiss T-2 prism, for lowest possible magnification, I was just a tiny hair short of focus (we are talking less than a millimiter... but no focus is no focus...).  Since this is the SV version, I didn't want to cut the OTA, which is perfectly tailored for the 95mm Tak clamshell (again see pix) and, after having tried the shortest adaptors on the market, decided to simply contact a machinist and have a tailor-made adapter ring which, after the removal of the original TKP37001 coupling, would screw into the focuser drawtube and, on the other side, has a mere T2 male so as to screw into the Baader/Zeiss prism. This gave plenty of focus to use, without any focus issue whatsoever and w/o OCS, TV Plossls 40, Zeiss Abbe 34, TV Panoptic 19, etc.  Given that the FSQ-85 OTA is already obviously sized for its focuser size, such a tailor-made adapter should address any of your concern. You may see it in a separated slot in the middle left of the carrying case.

Hi Max, this is very helpful, thank you. Finally some concrete data points on this scope working with bino viewing. I'm a bit confused though about some of the parts involved in your process. If you remove the original Coupling (TKP37001), then does your custom part screw directly into the drawtube, and then your diagonal goes into the custom part? If so, then this sounds nearly identical to what Gavster posted earlier above, in post #6, only instead of a custom part, he used a Baader Ultra Short Clamp, although I am not sure if he removed the Coupling too. What exactly does the Coupling accomplish?

 

 

 

This being said -- and given that we are talking *your* telescope, with *your* money and, therefore, you are of course master of doing whatever you like --, and with all due respect to the excellent FSQ-85 optics, if your aim is planetary and lunar high mag observation AND you are not a frequent flyer with your equipment (...and you do not want to dismantle your equipment into parts/components...), ANY of the FC100 series (just to remain in the Takahashi realm) would give you *visibly* higher performances and satisfaction. Mainly the DZ, of course, but even simply the DF.

 

A "Flatfield Petzval Quadruplet" is clearly designed with astrophotopgraphy in mind. Telescopes tailored to your interests are usually called "superplanetary".

Hope this helps.

 

Cheers,
-- Max

So I just had an FC100-DZ at my house for consideration. I ordered a TV-85 and an FC100-DZ together, to compare the two. While the FC100 did have amazing optics, it was just too long and big for my needs, so the TV-85 won. While I don't travel often, I just don't like big scopes very much, no matter how great their optics. 85 and 92mm scopes are my sweet spot, and it is the only aperature class I am interested in. I'm also looking for a "forever scope" in this class, and so my only two considerations right now are the TV-85 and the FSQ-85. Between these two scopes, I just need to know which one is the best, and then I can keep one, sell the other, and live in peace without every having to worry about telescopes again. I'm not like most other astronomers, I don't have the telescope bug, I'm happy to have just one scope and use it regularly and spend more money on accessories. I've had only one scope, a SV NHNG for 14 years, and it's finally time to replace it, with a scope which I will keep until I die.

 

All I need is a higher power to tell me definitively if that's the TV-85 or the FSQ-85. Sadly, there does not appear to be such a higher power, so am just going to order an FSQ-85 shortly and compare it with the TV-85 in person.

 

That being said, from what you have posted, it seems that an FSQ-85 should be able to come to focus with a bino viewer both with and without an OCS? If true, that's a great advantage over the TV-85, as it would allow bino viewing planets at high mag with OCS, but also enjoying the flat, wide starfields in bino without the extra magnification from the OCS. The TV-85 can only come to focus with an OCS in bino viewing.

 

One question though about your bino viewing with the FSQ-85 focuser: I know the FSQ-85 focuser only has 50mm of focus travel, as in, the drawtube only extends out a maximum of 50mm. This is really short by visual standards, as the TV-85 extends out 70mm. Did you find this was a problem in reaching focus with a binoviewer ever?


Edited by trias702, 22 May 2020 - 10:03 AM.


#27 Max Lattanzi

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Posted 22 May 2020 - 12:23 PM

Hi Max, this is very helpful, thank you. Finally some concrete data points on this scope working with bino viewing. I'm a bit confused though about some of the parts involved in your process. If you remove the original Coupling (TKP37001), then does your custom part screw directly into the drawtube, and then your diagonal goes into the custom part? If so, then this sounds nearly identical to what Gavster posted earlier above, in post #6, only instead of a custom part, he used a Baader Ultra Short Clamp, although I am not sure if he removed the Coupling too. What exactly does the Coupling accomplish?

Hi,

What Gavster suggested you is correct, but follows a different philosophical (so to speak) approach with different mechanical outcomes. He suggested you an add-on of an off-the-shelf adapter to be screwed on top of the TKP37001. This is obvioulsy very svelte (you go to the shop and you buy it) but had the disadvantage of "adding" the mechanical length of such addition.

My suggestion was to make a new, say, MAX37001 that would take the place of the TKP37001 and therefore adding nothing to the total length of the very minimum mechanical train: focuser drawtube/MAX37001/Baader-Zeiss prism. Nothing else. And less than this you cannot. I should take some measurement to be precise, but possibly Gavster can do it better than me: I tend to believe that, using the so-called MAX37001 you gain something between 12 and 20mm of backfocus.

When I want to use the telescope at its very minimum power, I simply unscrew the TKP37001 and put my custom adapter ring.
If I use OCS or Ext-Q or barlows there is simply no need for it: I unscrew the MAX and put back the TKP and use either a simple eyepiece holder (no need for a short one) and even add the CAA. You see all this in my pix.

 

 

So I just had an FC100-DZ at my house for consideration. I ordered a TV-85 and an FC100-DZ together, to compare the two. While the FC100 did have amazing optics, it was just too long and big for my needs, so the TV-85 won. While I don't travel often, I just don't like big scopes very much, no matter how great their optics. 85 and 92mm scopes are my sweet spot, and it is the only aperature class I am interested in. I'm also looking for a "forever scope" in this class, and so my only two considerations right now are the TV-85 and the FSQ-85. Between these two scopes, I just need to know which one is the best, and then I can keep one, sell the other, and live in peace without every having to worry about telescopes again. I'm not like most other astronomers, I don't have the telescope bug, I'm happy to have just one scope and use it regularly and spend more money on accessories. I've had only one scope, a SV NHNG for 14 years, and it's finally time to replace it, with a scope which I will keep until I die.

 

All I need is a higher power to tell me definitively if that's the TV-85 or the FSQ-85. Sadly, there does not appear to be such a higher power, so am just going to order an FSQ-85 shortly and compare it with the TV-85 in person.

 

That being said, from what you have posted, it seems that an FSQ-85 should be able to come to focus with a bino viewer both with and without an OCS? If true, that's a great advantage over the TV-85, as it would allow bino viewing planets at high mag with OCS, but also enjoying the flat, wide starfields in bino without the extra magnification from the OCS. The TV-85 can only come to focus with an OCS in bino viewing.

 

One question though about your bino viewing with the FSQ-85 focuser: I know the FSQ-85 focuser only has 50mm of focus travel, as in, the drawtube only extends out a maximum of 50mm. This is really short by visual standards, as the TV-85 extends out 70mm. Did you find this was a problem in reaching focus with a binoviewer ever?

OK, so if you already tried the DZ, my advice was off. What about the shorter DF...?!  Just a suggestion.  I keep insisting simply because the difference between an 85 and 100 on Moon and Planets is more significant than the mere penny pinch 15% addition in resolution may suggest.

In any event, I personally share your approach: in doubt I would get both and chose according to my own eyes, tastes, logistics, etc.

I never tried the TV-85 against the FSQ-85, so I should just shut up. Still, if personally had to choose, I would go with the Tak as a more flexible and globally superior optical and mechanical instrument. But, again, is a choice that totally belongs to you.

-- Max

PS/ Do not be concerned about the short focus travel: if needed, you may fix that in many ways (e.g. extention tubes, CAA). That is certainly not a criterion to choose on a telescope.
PS2/ Just warning you in advance: there is nothing in Astronomy as a "forever scope". You may have more chances of getting invited for dinner by the Arabian Phoenyx, than to find one of those wink.gif
 



#28 contrailmaker

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Posted 22 May 2020 - 02:18 PM

The other concern with binoviewing with this F/5.3 setup is aperture loss due to the steep light cone. I had a 120mm F/5 refractor that I liked very much for it’s wide angle views. When I tried my binoviewer it operated at the equivalent of 100mm as verified by the flashlight test. I had a special OCS made for it by Seibert optics but it still produced too much vignetting. At these focal ratios you are much better off getting binoculars, which is what I did. With binoculars you get all the advantages of binocular summation and a brighter image than with binoviewing a single scope.
 

CM
 


Edited by contrailmaker, 22 May 2020 - 02:18 PM.


#29 trias702

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Posted 22 May 2020 - 02:38 PM

OK, so if you already tried the DZ, my advice was off. What about the shorter DF...?!  Just a suggestion.  I keep insisting simply because the difference between an 85 and 100 on Moon and Planets is more significant than the mere penny pinch 15% addition in resolution may suggest.

In any event, I personally share your approach: in doubt I would get both and chose according to my own eyes, tastes, logistics, etc.

I never tried the TV-85 against the FSQ-85, so I should just shut up. Still, if personally had to choose, I would go with the Tak as a more flexible and globally superior optical and mechanical instrument. But, again, is a choice that totally belongs to you.

-- Max

PS/ Do not be concerned about the short focus travel: if needed, you may fix that in many ways (e.g. extention tubes, CAA). That is certainly not a criterion to choose on a telescope.
PS2/ Just warning you in advance: there is nothing in Astronomy as a "forever scope". You may have more chances of getting invited for dinner by the Arabian Phoenyx, than to find one of those wink.gif
 

The DF is actually longer than the DZ, because the DZ has a collapsible dew shield while the DF does not.

 

The only alternative I could potentially consider to the FSQ-85 is the Borg 107FL, which is a 107mm fluorite doublet on an 80mm tube body, and as short as the TV-85. This was actually my original idea for a forever scope, as you basically get the portability of the TV-85, but the 107mm fluorite doublet of the FC100 series. Best of both worlds right?

 

However, a lot of people on CN have mixed experiences with Borg for pure visual use, they claim their super fast doublets have bad CA and FC. Plus the helpfulness and support I found from Hutech was immensely unprofessional, so I gave up on the Borg. Although thinking about the Borg now, I am tempted to just buy one anyway to test it for myself, as I have said, you can't rely on others.

 

Trust me, for my personality, there is definitely a forever scope. For 14 years I owned only a single telescope and was happy enough with it. I don't do well when I have to split my attention and focus, I'm the kind of person who can only concentrate and commit to a single device, be it laptop, firearm, telescope, car, phone, etc.


Edited by trias702, 22 May 2020 - 02:41 PM.


#30 trias702

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Posted 22 May 2020 - 02:39 PM

The other concern with binoviewing with this F/5.3 setup is aperture loss due to the steep light cone. I had a 120mm F/5 refractor that I liked very much for it’s wide angle views. When I tried my binoviewer it operated at the equivalent of 100mm as verified by the flashlight test. I had a special OCS made for it by Seibert optics but it still produced too much vignetting. At these focal ratios you are much better off getting binoculars, which is what I did. With binoculars you get all the advantages of binocular summation and a brighter image than with binoviewing a single scope.
 

CM
 

 

Is this a problem with bino-viewing on any telescope or just with fast telescopes? Meaning, with an 85mm aperture F/5.3, will I be losing more aperature to binoviewing than I would be with an 85mm aperture F/7?


Edited by trias702, 22 May 2020 - 02:39 PM.


#31 The Ardent

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Posted 22 May 2020 - 03:22 PM

There is another reason I don’t do low-power BV on small scopes. For low power I want the widest practical  true field. A BV with 1.25” eyepieces simply cannot compete with a 2” well corrected eyepiece like the 31 Nagler in true field.  ( A short fast scope is at best efficiency with a well corrected eyepiece. ) 



#32 Gavster

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Posted 22 May 2020 - 03:57 PM

I decided to try my mark v binoviewers with my Tak fsq85 this evening. With a Baader t2 prism (and no gpc) it did come to focus (just!). You can see how close it was from the photo (about 2mm)

 

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#33 contrailmaker

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Posted 22 May 2020 - 04:19 PM

Is this a problem with bino-viewing on any telescope or just with fast telescopes? Meaning, with an 85mm aperture F/5.3, will I be losing more aperature to binoviewing than I would be with an 85mm aperture F/7?

It varies with telescope type but, in general, the faster the telescope the worse the problem becomes. With my C8 SCT there was considerable effective aperture reduction and it was an f/10. With refractors the problem starts showing below f/7 or so.
 

CM 



#34 trias702

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Posted 22 May 2020 - 04:54 PM

I decided to try my mark v binoviewers with my Tak fsq85 this evening. With a Baader t2 prism (and no gpc) it did come to focus (just!). You can see how close it was from the photo (about 2mm)

Thanks for checking! Does it also come to focus with the GPC/OCS as well?

 

Quick aside, are those 2" inch eyepieces in the Baader Mark V? It can take 2" eyepieces?


Edited by trias702, 22 May 2020 - 04:55 PM.


#35 Gavster

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Posted 22 May 2020 - 05:24 PM

Thanks for checking! Does it also come to focus with the GPC/OCS as well?

 

Quick aside, are those 2" inch eyepieces in the Baader Mark V? It can take 2" eyepieces?

Using any of the gpc’s pushes the focus point out so all will come to focus.

The eyepieces are 24mm panoptics, 1.25 inches.



#36 trias702

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Posted 22 May 2020 - 05:37 PM

Using any of the gpc’s pushes the focus point out so all will come to focus.

The eyepieces are 24mm panoptics, 1.25 inches.

That's so cool, I've never heard of a telescope which allows a bino viewer to work both with and without an OCS, without having to remove a section of the tube. That's really pretty incredible technology that it can do both with the same OTA package.

 

Given all the positive things I have read about the FSQ-85 here, and reading Olly's gushing praise over on SGL, I've just now ordered a brand new FSQ-85. It should arrive by end of next week.

 

Oh, and I ordered yet another TV-85 to replace the first one I refunded due to scratches in the paint. And this second, brand new TV-85 had even worse scratches and chips in the paint. I even started a separate thread about it. Looks like I'm done with Tele Vue and the FSQ-85 wins by default.

 

I may still order a Borg 107FL once they're back in stock in the USA, and have a proper showdown between it and the FSQ-85, but so far, the FSQ-85 has grown a lot on me in terms of reading and photos, and I'm very much hoping that the two of us get along like a house on fire and it is a keeper. I've also always wanted a Petzval, my dream scope was originally an NP101, but it's too big and heavy for me, so a baby NP101 sounds like just the ticket.


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#37 Gavster

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Posted 22 May 2020 - 05:47 PM

That's so cool, I've never heard of a telescope which allows a bino viewer to work both with and without an OCS, without having to remove a section of the tube. That's really pretty incredible technology that it can do both with the same OTA package.

 

Given all the positive things I have read about the FSQ-85 here, and reading Olly's gushing praise over on SGL, I've just now ordered a brand new FSQ-85. It should arrive by end of next week.

 

Oh, and I ordered yet another TV-85 to replace the first one I refunded due to scratches in the paint. And this second, brand new TV-85 had even worse scratches and chips in the paint. I even started a separate thread about it. Looks like I'm done with Tele Vue and the FSQ-85 wins by default.

 

I may still order a Borg 107FL once they're back in stock in the USA, and have a proper showdown between it and the FSQ-85, but so far, the FSQ-85 has grown a lot on me in terms of reading and photos, and I'm very much hoping that the two of us get along like a house on fire and it is a keeper. I've also always wanted a Petzval, my dream scope was originally an NP101, but it's too big and heavy for me, so a baby NP101 sounds like just the ticket.

I also have a lovely tv85 which doesn’t have any chips. But imo the fsq85 beats it comfortably. I’ll be interested to hear what you think.



#38 trias702

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Posted 22 May 2020 - 05:54 PM

I also have a lovely tv85 which doesn’t have any chips. But imo the fsq85 beats it comfortably. I’ll be interested to hear what you think.

 

Will definitely post a review once I get it.

 

I was very impressed with the TV-85 when I had it before I sent it back. If it didn't have any paint damage, I would've kept it as my forever scope. I'm still gutted that Fate seems hell-bent on ensuring I don't get a TV-85 in my life, but perhaps it's also Fate ensuring I end up with a better quality 85mm scope instead? We shall find out!

 

Are you still planning on selling your own TV-85?


Edited by trias702, 22 May 2020 - 06:00 PM.


#39 Gavster

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Posted 22 May 2020 - 06:00 PM

Will definitely post a review once I get it.

I was very impressed with the TV-85 when I had it before I sent it back. If it didn't have any paint damage, I would've kept it as my forever scope. I'm still gutted that Fate seems hell-bent on ensuring I don't get a TV-85 in my life, but perhaps it's also Fate ensuring I end up with a better quality 85mm scope instead? We shall find out!

 

Are you still planning on selling your own TV-85?

The tv85 is staying for now. It’s a robust scope for travelling with.

I like my fsq85 so much for visual use. I’ve just purchased the last new fsq130 available. Looking forward to testing this out next week.

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#40 trias702

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Posted 22 May 2020 - 06:35 PM

The tv85 is staying for now. It’s a robust scope for travelling with.

I like my fsq85 so much for visual use. I’ve just purchased the last new fsq130 available. Looking forward to testing this out next week.

I'm so happy to hear you say that about your FSQ-85, it helps fight a lot of my own stress/anxiety on whether or not I made the right choice in ordering the FSQ85 as well. But given all of the small refractors you have, if you're saying the FSQ-85 is your favourite visual scope, then that's a pretty massive endorsement not to be taken lightly.

 

Your FSQ-106 looks beautiful! Am definitely keen to hear how it compares to the FSQ-85!



#41 Gavster

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Posted 22 May 2020 - 06:40 PM

I'm so happy to hear you say that about your FSQ-85, it helps fight a lot of my own stress/anxiety on whether or not I made the right choice in ordering the FSQ85 as well. But given all of the small refractors you have, if you're saying the FSQ-85 is your favourite visual scope, then that's a pretty massive endorsement not to be taken lightly.

 

Your FSQ-106 looks beautiful! Am definitely keen to hear how it compares to the FSQ-85!

Not an fsq-106, it’s an fsq-130! :)



#42 trias702

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Posted 22 May 2020 - 06:47 PM

Not an fsq-106, it’s an fsq-130! smile.gif

Sorry, my bad! I wasn't actually even aware there was an FSQ-130, have only ever heard about the 85 and 106 on these forums. Checking the price of the 130....standby....wait what? It's not even a product on Takahashi America's website.

 

When you said "last new one" I guess you really meant it. Given how much the FSQ-106 costs, can only imagine the 130 shocked.gif



#43 Max Lattanzi

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Posted 23 May 2020 - 02:52 AM

The other concern with binoviewing with this F/5.3 setup is aperture loss due to the steep light cone. I had a 120mm F/5 refractor that I liked very much for it’s wide angle views. When I tried my binoviewer it operated at the equivalent of 100mm as verified by the flashlight test. I had a special OCS made for it by Seibert optics but it still produced too much vignetting. At these focal ratios you are much better off getting binoculars, which is what I did. With binoculars you get all the advantages of binocular summation and a brighter image than with binoviewing a single scope.
 

CM
 

It is not the steep light cone. SImply the drawtube of your telescope is too narrow. When you use the BV you rack it in more than usual and, if the drawtube was calculated without keeping in mind the use of a binoviewer and its requirements, it intercepts the light cone. Switch to a larger focuser and you and your BV will see the full aperture.

 

-- Max



#44 25585

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Posted 23 May 2020 - 04:12 AM

I imagine bino viewing with a TV-76 or Pronto would need similar accessories. A shame the Bizarro 85 is no longer made perhaps.



#45 contrailmaker

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Posted 23 May 2020 - 04:18 AM

It is not the steep light cone. SImply the drawtube of your telescope is too narrow. When you use the BV you rack it in more than usual and, if the drawtube was calculated without keeping in mind the use of a binoviewer and its requirements, it intercepts the light cone. Switch to a larger focuser and you and your BV will see the full aperture.

 

-- Max

The draw tube part is correct but, the steeper light cone is part of the problem. You don’t ever see this issue on an f/9 refractor. A bigger focuser may or may not fully solve the problem depending on the scope. Like I said, I went through this exercise with the help of Harry Siebert and still could not get my f/5 telescope to work at full aperture.

 

 

CM
 


Edited by contrailmaker, 23 May 2020 - 04:47 AM.


#46 Max Lattanzi

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Posted 23 May 2020 - 07:38 AM

The draw tube part is correct but, the steeper light cone is part of the problem. You don’t ever see this issue on an f/9 refractor. A bigger focuser may or may not fully solve the problem depending on the scope. Like I said, I went through this exercise with the help of Harry Siebert and still could not get my f/5 telescope to work at full aperture.

 

 

CM
 

How do you know is correct?  Have you switched to a larger one?
I have 4 binos and have used and use all of them on some 40 different telescopes down to f/4.8 
But with proper focusers. Large ones.

There are no optical reasons why you bino is vignetting while your same-entry-pupil eyepiece is fully illuminated, other than the improper draw tube racked in, which cuts the light cone (and that is mechanical, not optical).
Again, enlarge the draw tube and you will have no aperture cut. It's as simple as that.

-- Max

PS/ Of course you do not see if with the f/9 telescope, the lens, at equal diameter, being at almost double distance from the drawtube, which can be more loosely designed.
OTOH, I have seen unproperly designed drawtubes vignetting even at f/15. The two variables are independent.



#47 Gavster

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Posted 23 May 2020 - 09:58 AM

How do you know is correct?  Have you switched to a larger one?
I have 4 binos and have used and use all of them on some 40 different telescopes down to f/4.8 
But with proper focusers. Large ones.

There are no optical reasons why you bino is vignetting while your same-entry-pupil eyepiece is fully illuminated, other than the improper draw tube racked in, which cuts the light cone (and that is mechanical, not optical).
Again, enlarge the draw tube and you will have no aperture cut. It's as simple as that.

-- Max

PS/ Of course you do not see if with the f/9 telescope, the lens, at equal diameter, being at almost double distance from the drawtube, which can be more loosely designed.
OTOH, I have seen unproperly designed drawtubes vignetting even at f/15. The two variables are independent.

This is interesting Max. So given my fsq85 is similar f ratio to your Tak sky 90mm and it has a big focuser then it should work well with the binoviewers once you get it short enough to reach focus?



#48 contrailmaker

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Posted 23 May 2020 - 11:59 AM

How do you know is correct?  Have you switched to a larger one?
I have 4 binos and have used and use all of them on some 40 different telescopes down to f/4.8 
But with proper focusers. Large ones.

There are no optical reasons why you bino is vignetting while your same-entry-pupil eyepiece is fully illuminated, other than the improper draw tube racked in, which cuts the light cone (and that is mechanical, not optical).
Again, enlarge the draw tube and you will have no aperture cut. It's as simple as that.

-- Max

PS/ Of course you do not see if with the f/9 telescope, the lens, at equal diameter, being at almost double distance from the drawtube, which can be more loosely designed.
OTOH, I have seen unproperly designed drawtubes vignetting even at f/15. The two variables are independent.

Yup, tried different focusers. That trick didn’t work in that particular telescope. After that it was not worth spending more money on the project as big binoculars do a better job for low power wide angle in my opinion. I have to ask, Did you do a laser/flashlight test to check if your scopes were operating at full aperture? There are several long threads on this subject from a few years ago in the binoviewer forum so I’d like to know what works. I’m curious how it turns out with the OP’s Tak. A simple flashlight test can tell.

 

 

CM


Edited by contrailmaker, 23 May 2020 - 01:07 PM.


#49 trias702

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Posted 23 May 2020 - 04:32 PM

I would be very curious to learn more about this truncated binoviewing phenomenon on short FL refractors and how I can check to see if my scope is operating at max aperture with a binoviewer. If you could please post a link to a thread which teaches how to do this, I would appreciate it greatly and will post my findings here.

 

I'll do the test on my new FSQ once it arrives.



#50 Max Lattanzi

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Posted 24 May 2020 - 09:42 AM

Yup, tried different focusers. That trick didn’t work in that particular telescope. After that it was not worth spending more money on the project as big binoculars do a better job for low power wide angle in my opinion. I have to ask, Did you do a laser/flashlight test to check if your scopes were operating at full aperture? There are several long threads on this subject from a few years ago in the binoviewer forum so I’d like to know what works. I’m curious how it turns out with the OP’s Tak. A simple flashlight test can tell.

 

 

CM

OK for "different", but I meant "larger" -- with 3-4in. wide drawtube.
Yes, of course checked with flashlight. But you can also do it with your eyes: once you see the full objective border from the eyepiece side, you're done.

As per bino, you are talking to someone with a custom 6" binoscope. So, trust me, I am totally with you. But alas it does not fit into a 5" x 5" x 16" handbag wink.gif
 

-- Max




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