Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Which brands produce "true" Apochromatic Refractors?

  • Please log in to reply
95 replies to this topic

#1 Barologuy

Barologuy

    Explorer 1

  • -----
  • topic starter
  • Posts: 67
  • Joined: 28 Jul 2020

Posted 11 October 2020 - 12:31 PM

By true I mean they contain FPL-53 glass or better, and show little to no color dispersion on bright objects. I edited these requirements because I realize now that this is entirely based on other factors of the telescope, not just glass type or number of lenses.

Budget really isn't a factor, I'm just wondering what people have to say from their own research or experiences, whether it's your dream scope, a scope you own, or a scope you once owned, tell me who you went with, or will go with, for your beautiful, unadulterated raw data!

Edited by Barologuy, 11 October 2020 - 01:46 PM.

  • Rince likes this

#2 Ken Sturrock

Ken Sturrock

    Cardinal Ximenez

  • *****
  • Administrators
  • Posts: 9,376
  • Joined: 26 Sep 2009
  • Loc: Denver, CO

Posted 11 October 2020 - 12:44 PM

I suspect that most mainstream (as well as the bespoke) manufacturers & resellers produce such instruments. You do have to learn to read between the lines and keep more than a single number in your head.

 

As an example, there are slightly different definitions of "apochromatic". You can also certainly build excellent refractors with lower Abbe-value glass or in a doublet format if you are flexible about the focal length. Imaging usage (as well as which camera) versus visual usage also factors in here. Moreover, some people are just pickier. I'm also unsure of what you mean by "50x" as a high magnification, is that per inch or something?

 

From my own experience, I'd say that my (no longer made) Stellarvue SV-80 and SV-102t, which used Russian OK4 glass in a triplet format, meet your criteria. I'd say that my current TEC-140FL meets that criteria, too. Although it may be too soon to tell based on my lack of time with it. For all practical purposes, my TV-76 doublet does fine for its intended use. While we're at it, my flint & crown 50mm f/14 Swift achromat is no slouch due to small aperture and long focal length. My instruments are usually better than my skies and eyesight.

 

I'll certainly defer to my betters on this.


  • Wildetelescope and BruceNewEngland like this

#3 sg6

sg6

    Cosmos

  • *****
  • Posts: 9,071
  • Joined: 14 Feb 2010
  • Loc: Norfolk, UK.

Posted 11 October 2020 - 12:49 PM

My "dream" would be a LZOS, but they are basically unavailable and they are close to hand made. One amusing incident of a LZOS on CN around 5 or 6 years ago.

 

In general I have settled on William Optics. They seem to have their act together now. Initial problems at first and a couple of designs that didn't turn out ideal, have however seemed to overcome those. Maybe an amount of common sense was applied. An amazingly uncommon thing.

 

One I may get myself is the WO 132mm APO. Oddly the 152mm has never appealed.


  • BinoGuy likes this

#4 junomike

junomike

    Hubble

  • *****
  • Moderators
  • Posts: 19,872
  • Joined: 07 Sep 2009
  • Loc: Ontario

Posted 11 October 2020 - 12:53 PM

The answer differs depending on size and F/L.  What range are you looking at?


  • Jon Isaacs likes this

#5 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 87,438
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 11 October 2020 - 01:13 PM

By true I mean they contain FPL-53 glass or better, are a minimum of a triplet, and show little to no color dispersion on bright objects at high zoom such as 50x. Budget really isn't a factor, I'm just wondering what people have to say from their own research or experiences, whether it's your dream scope, a scope you own, or a scope you once owned, tell me who you went with, or will go with, for your beautiful, unadulterated raw data!

When you say "high zoom", do you mean 50x/in or just 50x?

 

As Mike says, color correction depends on aperture and focal length.  A 4 inch F/9 FPL-53 doublet can have excellent color correction.  

 

Jon


  • 25585 likes this

#6 bobzeq25

bobzeq25

    ISS

  • *****
  • Posts: 21,469
  • Joined: 27 Oct 2014

Posted 11 October 2020 - 01:14 PM

Lots.  Of significantly varying quality.  Triplet and FPL-53 don't correct for mediocre design.  It's possible to omit one of those, and come up with a lens that's better than another lens with both.  And there are better alternatives.

 

There is _no_ shortcut to looking at scopes carefully.  Price is actually another good indicator of quality, this market works well.  Expensive mediocre stuff doesn't last long.  User reviews are excellent.

 

So my dream refractors (note that only the cheap one is a conventional FPL-53 triplet, air spaced) are:

 

Widefield.  Takahashi FSQ-106EDX4 (which is a quad).   $6000.

 

Galaxies.  CFF 140 F6.5.  6500 Euro.  Maybe the best FPL-53 triplet, although it is oil spaced.

 

or maybe a TEC 140FL, F7.  Fluoride, not FPL-53.  $7400. 

 

Cheap (<grin> ) alternative to the two above.  Stellarvue SVX140T.  F6.7.  $6500.

 

Bigger would mean a new mount to replace the CEM60, maybe a 10Micron GM1000 HPS.  $9200.

 

You said "no budget", correct?  <smile>


Edited by bobzeq25, 11 October 2020 - 01:25 PM.

  • Barologuy likes this

#7 Barologuy

Barologuy

    Explorer 1

  • -----
  • topic starter
  • Posts: 67
  • Joined: 28 Jul 2020

Posted 11 October 2020 - 01:18 PM

Myself I was looking at the WO 132mm APO, it's probably going to be a matter of years before that happens, but who knows! I already own a 61mm, and I'm building a 152mm doublet from a lens I found online, so I'm just looking for something that fills part of that gap.

#8 junomike

junomike

    Hubble

  • *****
  • Moderators
  • Posts: 19,872
  • Joined: 07 Sep 2009
  • Loc: Ontario

Posted 11 October 2020 - 01:21 PM

Myself I was looking at the WO 132mm APO, it's probably going to be a matter of years before that happens, but who knows! I already own a 61mm, and I'm building a 152mm doublet from a lens I found online, so I'm just looking for something that fills part of that gap.

That's a fine TMB Designed  FPL-53 Triplet IMO.  Can't see you being unhappy with it.



#9 barbarosa

barbarosa

    Mercury-Atlas

  • *****
  • Posts: 2,658
  • Joined: 11 Apr 2010
  • Loc: 139 miles W of the Awahnee Hotel

Posted 11 October 2020 - 01:39 PM

Did you mean actual "manufacturers" or the larger category of brand names? Jiaxing Ruixing Optical Instrument Co., Ltd. makes SharpStar and seems to make at least some scopes sold under the  AstroTech and Williams Optics and other brand names.

 

Takahashi, Televue  and lately Stellarue and a few others manufacture/assemble their own products.

 

I have a very nice Skywatcher Esprit, FPL-53 ED triplet, but I have no idea what company made it or whether any apparent clone under a different name is of the same quality.

 

For those reasons I think we can discuss particular models that meet your criteria but not manufacturers, because for all we know any of them might buy some of their lines from other companies.



#10 Barologuy

Barologuy

    Explorer 1

  • -----
  • topic starter
  • Posts: 67
  • Joined: 28 Jul 2020

Posted 11 October 2020 - 01:41 PM

Lots. Of significantly varying quality. Triplet and FPL-53 don't correct for mediocre design. It's possible to omit one of those, and come up with a lens that's better than another lens with both. And there are better alternatives.

There is _no_ shortcut to looking at scopes carefully. Price is actually another good indicator of quality, this market works well. Expensive mediocre stuff doesn't last long. User reviews are excellent.

So my dream refractors (note that only the cheap one is a conventional FPL-53 triplet, air spaced) are:

Widefield. Takahashi FSQ-106EDX4 (which is a quad). $6000.

Galaxies. CFF 140 F6.5. 6500 Euro. Maybe the best FPL-53 triplet, although it is oil spaced.

or maybe a TEC 140FL, F7. Fluoride, not FPL-53. $7400.

Cheap (<grin> ) alternative to the two above. Stellarvue SVX140T. F6.7. $6500.

Bigger would mean a new mount to replace the CEM60, maybe a 10Micron GM1000 HPS. $9200.

You said "no budget", correct? <smile>


This post makes me happy. I did say no budget! What are the advantages/disadvantages of being oil spaced?

#11 Barologuy

Barologuy

    Explorer 1

  • -----
  • topic starter
  • Posts: 67
  • Joined: 28 Jul 2020

Posted 11 October 2020 - 01:43 PM

Did you mean actual "manufacturers" or the larger category of brand names? Jiaxing Ruixing Optical Instrument Co., Ltd. makes SharpStar and seems to make at least some scopes sold under the AstroTech and Williams Optics and other brand names.

Takahashi, Televue and lately Stellarue and a few others manufacture/assemble their own products.

I have a very nice Skywatcher Esprit, FPL-53 ED triplet, but I have no idea what company made it or whether any apparent clone under a different name is of the same quality.

For those reasons I think we can discuss particular models that meet your criteria but not manufacturers, because for all we know any of them might buy some of their lines from other companies.


I agree, sorry when I say manufacturer, I definitely mean to refer to brands.

#12 bobzeq25

bobzeq25

    ISS

  • *****
  • Posts: 21,469
  • Joined: 27 Oct 2014

Posted 11 October 2020 - 01:49 PM

Myself I was looking at the WO 132mm APO, it's probably going to be a matter of years before that happens, but who knows! I already own a 61mm, and I'm building a 152mm doublet from a lens I found online, so I'm just looking for something that fills part of that gap.

So you _do_ have a budget.  <smile>

 

I have this scope (exactly, but with the better focuser, to avoid being tempted to get a Featherlite).  Works well.  M13 below.  FPL-53 from Ohara (there are different manufacturers of FPL-53).

 

https://www.teleskop...-Refractor.html

 

Bought mine from Karl Kloss.  He puts them on an optical bench, will give you the report on your specific scope, there may be a small fee.  Good "lemon" insurance.

 

https://www.teleskop...ed5f831c6ea8b76

 

M13V19.jpg


Edited by bobzeq25, 11 October 2020 - 01:59 PM.

  • doctordub, BKBrown, niteskystargazer and 7 others like this

#13 bobzeq25

bobzeq25

    ISS

  • *****
  • Posts: 21,469
  • Joined: 27 Oct 2014

Posted 11 October 2020 - 02:01 PM

This post makes me happy. I did say no budget! What are the advantages/disadvantages of being oil spaced?

More opinions than just mine.  It is a high end feature.

 

https://www.cloudyni...ced-refractors/


Edited by bobzeq25, 11 October 2020 - 02:02 PM.


#14 Suavi

Suavi

    Viking 1

  • -----
  • Posts: 563
  • Joined: 05 May 2017
  • Loc: 20.25 deg South of the Equator

Posted 11 October 2020 - 03:36 PM

This post makes me happy. I did say no budget! What are the advantages/disadvantages of being oil spaced?

And this is what people at Baader write about such design.


  • Jeff Bennett, eros312 and Echolight like this

#15 sunnyday

sunnyday

    Voyager 1

  • *****
  • Posts: 11,125
  • Joined: 23 Sep 2019
  • Loc: the Canadian nebula .

Posted 12 October 2020 - 08:55 AM

By true I mean they contain FPL-53 glass or better, and show little to no color dispersion on bright objects. I edited these requirements because I realize now that this is entirely based on other factors of the telescope, not just glass type or number of lenses.

Budget really isn't a factor, I'm just wondering what people have to say from their own research or experiences, whether it's your dream scope, a scope you own, or a scope you once owned, tell me who you went with, or will go with, for your beautiful, unadulterated raw data!

takahashi fc-100 dz , -  sw 120 ed , - es 127 mm are apo's .



#16 noisejammer

noisejammer

    Fish Slapper

  • *****
  • Posts: 3,937
  • Joined: 16 Sep 2007
  • Loc: The Uncanny Valley

Posted 12 October 2020 - 09:28 AM

My TOA150 uses 2 slices of FPL-53, so is it twice as good as you need? it's certainly colour free at every magnification that makes sense for a 6". The TOA130 and TSA102 are similar. I can't speak to other Tak refractors.

 

A friend's blue-tube AP 152 (f/9) has visible colour If you stress the optics by pointing it at extremely high contrast objects. It's oil spaced but it's very usable for visual but it's not up to modern instruments.

 

My APM 115/805 (a Tom Back design made by LZOS) is colour free past 50x/in. Another friend's APM 152 (also LZOS) had very slight colour but it could have just been cool down effects.

 

My (now gone) FLT110 (FPL-51, Tom Back design) and Borg 60ED (FPL-53 doublet) have very slight oof color but it's invisible at focus.

 

So there are lots of makers who make excellent scopes. In fact, it's probable most are excellent.


  • doctordub, payner and Auburn80 like this

#17 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 87,438
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 12 October 2020 - 10:26 AM

A friend's blue-tube AP 152 (f/9) has visible colour If you stress the optics by pointing it at extremely high contrast objects. It's oil spaced but it's very usable for visual but it's not up to modern instruments.

 

 

Bruce:

 

What vintage A-P is that?  Is in the FPL-52/53 era or early?

 

Jon



#18 csauer52

csauer52

    Messenger

  • *****
  • Posts: 434
  • Joined: 05 Jan 2011
  • Loc: Raleigh, NC

Posted 12 October 2020 - 10:59 AM

I'm surprised the TOA-130 hasn't been brought up in this thread. Lots of good options have already been discussed but I would also consider the TOA-130. Admittedly, I've not used other APO scope primarily because the TOA is as close to perfection as one can get IMHO. I've owned mine since 2005 and have not felt the need to play around with other brands.

 

I don't think you can go wrong with AP, Tak, TEC, LZOS, TV etc....  It just depends on what you like as they're all great scopes. One word of caution on the Taks - while the optics are among the best out there, the stock focusers aren't known to be that great mechanically and you'll likely spend additional money upgrading the focuser. Just food for thought......


  • Tyson M and 25585 like this

#19 alan.dang

alan.dang

    Mariner 2

  • *****
  • Posts: 278
  • Joined: 15 Dec 2011

Posted 12 October 2020 - 11:04 AM

Bruce:

What vintage A-P is that? Is in the FPL-52/53 era or early?

Jon


Predates ED and SD glass. In the early days, Astro Physics used a special batch of glass made for NASA, and when that glass ran out, KzFSN-4. They switched to FPL-5x with the Starfire line.

#20 rgsalinger

rgsalinger

    Fly Me to the Moon

  • *****
  • Moderators
  • Posts: 7,186
  • Joined: 19 Feb 2007
  • Loc: Carlsbad Ca

Posted 12 October 2020 - 11:08 AM

I've been curious for years about why a lot of people go on and on about "glass". Is it really a documented case that you can't produce a good refractor without using specific glasses? I have no idea what glasses are in my refractor trio, I only care about the views and the images that I get from them. I would expect that there are lots of ways to eliminate CA without using one particular "glass". Comments please.

Rgrds-Ross


  • BruceNewEngland likes this

#21 BoldAxis1967

BoldAxis1967

    Viking 1

  • *****
  • Posts: 950
  • Joined: 11 Oct 2012
  • Loc: Kentucky

Posted 12 October 2020 - 11:12 AM

I do not have any high-end refractors (AP, Tec, Tak) but I have looked through AP and especially Tec-140 and Tec 160 a number of times.  And, I have compared the Tec and APs to my own ES127ED and SV125 enough times  to draw some personal conclusions.  I have compared on a couple of occasions the TEC 140 with the ES and SV directly (side by side).

 

Visual Impressions only (no AstroPhoto and not a formal comparison) :

 

1) CA: The color differences are small.  I have seen CA in every refractor I have looked through.  Granted, I tested on some tough objects (Venus, Sirus etc).  The Tec and APs have better color control, but it was not by much.

2)  Sharpness:  The Tec and AP were sharper.  Stars were tighter.  It is not by much, very little, but the differences were present. 

3)  Contrast:  This was the biggest difference and very noticeable. The background sky was blacker and the stars (star-fields or star clusters) brighter and just seem to pop-out more. 

 

Another thing that one has to keep in mind:  Quality control is greater with high-end and there will be more variation with mass produced.

 

You get what you pay for and that is the way it should be. 

 

If one has a good, mass produced scope and does not enjoy the view, well I do not know what to say.

 

I appreciate the mass produced scopes I have but if I could afford a TEC-140 and a rock solid mount and tripod to go with it I would get one.

 

L.

 

P.S. I find the ES and SV are optically indistinguishable.


Edited by BoldAxis1967, 12 October 2020 - 11:50 AM.

  • Alan S likes this

#22 noisejammer

noisejammer

    Fish Slapper

  • *****
  • Posts: 3,937
  • Joined: 16 Sep 2007
  • Loc: The Uncanny Valley

Posted 12 October 2020 - 04:36 PM

Bruce:

 

What vintage A-P is that?  Is in the FPL-52/53 era or early?

 

Jon

Jon, I think it's from about the mid- to late 90's. It's focuser is pretty basic but it does have a field flattener that looks big enough for a 6x6.

 

I'm surprised the TOA-130 hasn't been brought up in this thread. Lots of good options have already been discussed but I would also consider the TOA-130. Admittedly, I've not used other APO scope primarily because the TOA is as close to perfection as one can get IMHO. I've owned mine since 2005 and have not felt the need to play around with other brands.

 

I don't think you can go wrong with AP, Tak, TEC, LZOS, TV etc....  It just depends on what you like as they're all great scopes. One word of caution on the Taks - while the optics are among the best out there, the stock focusers aren't known to be that great mechanically and you'll likely spend additional money upgrading the focuser. Just food for thought......

Umm ... I mentioned the TOA130 two posts above yours. :lol:

 

I've used one from the very first batch - iirc 2004. The dew shield is signed by the team that put it together. Until I bought my TOA150, this was the best telescope I'd encountered.

 

Newer TOA130 models have switched to a double FPL-53 design like the TOA150 - possibly because one of the matching glasses was unavailable.
 


  • payner, csauer52 and Tyson M like this

#23 csauer52

csauer52

    Messenger

  • *****
  • Posts: 434
  • Joined: 05 Jan 2011
  • Loc: Raleigh, NC

Posted 12 October 2020 - 04:58 PM

Jon, I think it's from about the mid- to late 90's. It's focuser is pretty basic but it does have a field flattener that looks big enough for a 6x6.

 

Umm ... I mentioned the TOA130 two posts above yours. lol.gif

 

I've used one from the very first batch - iirc 2004. The dew shield is signed by the team that put it together. Until I bought my TOA150, this was the best telescope I'd encountered.

 

Newer TOA130 models have switched to a double FPL-53 design like the TOA150 - possibly because one of the matching glasses was unavailable.
 

Whoops - I definitely missed that. Apologies.....

 

At one point I owned FRC-300, serial #1 which was also signed on the dew shield by the team. I miss that scope but where I live now just isn't conducive to that caliber OTA. The seeing is **** poor (usually 2" - 3") and the LP is terrible. 


Edited by csauer52, 12 October 2020 - 05:01 PM.


#24 Phil Cowell

Phil Cowell

    Fly Me to the Moon

  • *****
  • Posts: 6,092
  • Joined: 24 May 2007
  • Loc: Southern Tier NY

Posted 12 October 2020 - 06:09 PM

Agree and prescription is also very important.

 

When you say "high zoom", do you mean 50x/in or just 50x?

 

As Mike says, color correction depends on aperture and focal length.  A 4 inch F/9 FPL-53 doublet can have excellent color correction.  

 

Jon



#25 John Huntley

John Huntley

    Mercury-Atlas

  • ***--
  • Posts: 2,729
  • Joined: 16 Jul 2006
  • Loc: SW England

Posted 12 October 2020 - 06:48 PM

I've seen some refractors described as super-achromats or even super-apos which are apparently a step up again in terms of colour control. I believe this has been defined as an objective that achieves 4 color crossings.

 

It does sound rather like a marketing term though hmm.gif




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics