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

4” f/6 vs 4” f/7 ED FPL-51 option

  • Please log in to reply
14 replies to this topic

#1 vkhastro1

vkhastro1

    Apollo

  • *****
  • topic starter
  • Posts: 1,253
  • Joined: 21 Aug 2005
  • Loc: Vankleek Hill, Ontario, Canada

Posted 07 February 2020 - 11:21 AM

Kson clone 4” f/6 ED (used) vs Astro Tech 102ED (used or new) 

 

A little background info.

I currently have two different 4” APOs - Starwave 102ED f/11 and Vixen 102F f/8.8.

Both are excellent but have longer tubes.

 

Looking for a light weight shorter focal length (smaller momentum arm) 4” ED with Vixen style mounting plate to use on one side on a dual setup with a William Optics EZ Touch mount (Deepsky use only - max 100X to 125X)

 

Very little info on the Kson 4” f/6 with 2” Crayford focuser/sliding dewshield (discontinued ~ 2013)

Reviews say some CA but more noticeable over 100X. 

The current Astro Tech with sliding dewshield + 2” excellent rack and pinion focuser - excellent optical and mechanical reviews.

Cost wise the Kson would be about half the cost of a new AT 102 ED.

 

Which would you choose ?



#2 Phillip Creed

Phillip Creed

    Idiot Seeking Village

  • *****
  • Posts: 3,314
  • Joined: 25 Jul 2006
  • Loc: Canal Fulton, OH

Posted 07 February 2020 - 11:29 AM

Get the AT102ED.  Better mechanics, less CA and visible field curvature at f/7 vs. f/6.  Also, f/7 is a bit more forgiving of eyepiece selection than f/6.

Clear Skies,

Phil


  • stevew and eros312 like this

#3 gene 4181

gene 4181

    Aurora

  • *****
  • Posts: 4,877
  • Joined: 12 Nov 2013
  • Loc: n.e. ohio

Posted 07 February 2020 - 11:40 AM

  Currently theres also a 108-110  F 6 available with FPL 51  .  IF your going for FOV  / keeping it short on the mount /  getting as much available light ,    I thought I should mention it , Ioptron Versa ED 108 and Orion  Eon 108  .   I have the AT 102   non sliding dewshield  F7 ,   check out the  classifieds  ,  a few AT 's were available used at very decent prices .....  I even considered a Orion 120 f 5  for "just " DSO hunting , largest open clusters etc.     There is a guy around here that  has a Kson f6 ,  I think it was Kon dealer  but i'm not sure   , he might have it listed in his arsenal , you could PM him .  IF your going for price the AT or used  Kson way too go



#4 Phillip Creed

Phillip Creed

    Idiot Seeking Village

  • *****
  • Posts: 3,314
  • Joined: 25 Jul 2006
  • Loc: Canal Fulton, OH

Posted 07 February 2020 - 11:42 AM

I should point out that neither scope will be as "apo" as your current pair of 4" scopes.  We're not talking screaming fast achro, but distinctly more color error than what you have.  The 4" f/6 KSON I suspect would have color correction on par with the older Stellarvue 110mm f/7, so if you can reviews on that, it should be comparable.

I've heard good things, though, about the 102mm f/7 FPL-53+Lanthanum doublets.  They were marketed as the Stellarvue 102 Access.  TS Optics has one as well as Altair (Starwave 102ED-R).  Roughly on par with a Genesis-SDF / TV-101 or TV-102 in terms of color correction from what I've heard from two very experienced CN'ers.  As in, not quiiiiite perfect, but VERY close for visual purposes and, having browsed Astrobin, I know people will image with them.

Cost-wise, you're looking at ~$1,000 U.S. or less, especially used.  A real step up from a 4" f/7 FPL-51 ED doublet.

Clear Skies,

Phil


  • stevew likes this

#5 vkhastro1

vkhastro1

    Apollo

  • *****
  • topic starter
  • Posts: 1,253
  • Joined: 21 Aug 2005
  • Loc: Vankleek Hill, Ontario, Canada

Posted 07 February 2020 - 12:22 PM

Thanks for the replies.

I had a SV 110 f/7 Ed (FPl-51) several years ago - for Deepsky observing the CA was never a problem.

If the CA is similar with the Kson clone then that will not be an issue.

I don’t think there is a distinct advantage of FPL-53 over FPL-51 for Deepsky observing in the 4” ~ f/7 refractor.



#6 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 81,676
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 07 February 2020 - 06:27 PM

Hi:

 

CN member Michael Kothe has a Kson 102 F/6.  I have actually looked through it a time or two but I wasn't doing critical evaluations. 

 

I sent him a PM so hopefully he will show up and comment.

 

Jon



#7 mkothe

mkothe

    Messenger

  • *****
  • Posts: 493
  • Joined: 08 Mar 2007
  • Loc: Boston, MA

Posted 07 February 2020 - 07:05 PM

Yes, I have the KSON 102 f6 ED and like it. I mostly got it for travel and wide field complement to my 12.5” dob. It fits nicely into a (barely) carry-on-size bag with Az-GTi diagonal and eyepieces (see link in my signature and scroll down for pictures of the scope in the bag). It’s 20.5” long (without diagonal) and weighs 8lbs 6oz with rings and diagonal. I have not used it all that much, but when I do, I don’t notice objectionable color. I’m sure it’s there, but I have not looked closely for it, and mostly use it for wide field. Too bad that Jon cannot comment on the color compared to other scopes, since he has so much more experience. Search for posts by Kon Dealer on the KSON. He has one and has comparisons to other scopes. He moved on to something better, but kept the KSON. Michael
  • Jon Isaacs, nirvanix, eros312 and 1 other like this

#8 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 81,676
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 07 February 2020 - 07:59 PM

Michael:

 

I don't think we ever really looked at anything that challenged the color correction, we never looked at Venus or the planets.  But my recollection is that it did a good job for the Deep Sky viewing we did do.  If he can get the scope for half the price of an AT-102ED, it seems like a no brainer to me, If I saw one at $300 around here, I would very likely buy it.  It's like an 80mm ED with 25% more aperture but not quite the color correction. 

 

Jon



#9 punk35

punk35

    Apollo

  • *****
  • Posts: 1,264
  • Joined: 26 Jan 2005
  • Loc: Adrian Michigan

Posted 07 February 2020 - 08:35 PM

I don’t know about the Kson, but my At102ED performs very well. It has a tiny bit of ca at higher powers, but according to your usage description, you probably won’t notice it. Crisp and clean views, and an excellent build quality. While I don’t have the skills to interpret a star test or do DPAC on my lens, I believe the AT lenses to be very well figured. Since you are used to fpl53/fluorite, and have looked through a 110f/7 fpl51,  you probably know that the 102 will have less ca than the 110 at the same fl, and more than your fpl53/fluorite scopes. 
 

I think the AT102ED is a great multi purpose scope. If you decide to point it at Jupiter or M42, the view is very nice. 
 


  • eros312 and Jond105 like this

#10 SeattleScott

SeattleScott

    Fly Me to the Moon

  • *****
  • Posts: 6,841
  • Joined: 14 Oct 2011

Posted 07 February 2020 - 09:50 PM

For DSO only up to 100-125x, the F6 will be fine from a CA perspective. You may not like the field curvature though. Kind of a personal thing.

Scott

#11 chris charen

chris charen

    Surveyor 1

  • *****
  • Posts: 1,788
  • Joined: 10 Mar 2014
  • Loc: Auckland. New Zealand

Posted 08 February 2020 - 02:44 AM

I had the Kson 102 F/6. Kept it for 6 months but on sold it as even at moderate powers [80x+] the CA was overly distracting. There was moderate field curvature too. [As to be expected.] Good build qualities but the CA proved too much. I also had the blue tube Kson 80 mm triplet [FPL-51] for several months, even that showed moderate CA above 100x. The Synta 80 ED doublets displayed less CA. I now have a 72 mm SW ED Evostar for quick looks, CA in that is well controlled.

Attached Thumbnails

  • DSC00669.jpg 2 kson.jpg

  • eros312 and SeattleScott like this

#12 Kon Dealer

Kon Dealer

    Viking 1

  • -----
  • Posts: 991
  • Joined: 05 Jan 2011
  • Loc: Cambridge UK

Posted 09 February 2020 - 04:46 AM

Still got my Kson 102/f6. Also got a TS 90mm f/6.7 triplet. 
Yes the Kson does show CA, but I do not find it distracting.

Cannot see anything in the triplet that I can’t see in the Kson.

Plus Kson is lighter and cools down quicker.

Use the Kson as  my travel/grab and go scope.

The TS for home use.


  • Jon Isaacs likes this

#13 chris charen

chris charen

    Surveyor 1

  • *****
  • Posts: 1,788
  • Joined: 10 Mar 2014
  • Loc: Auckland. New Zealand

Posted 09 February 2020 - 05:17 PM

I should have added the caveat that my eyes are sensitive to CA.The Kson 102 ED may suit others who are not so sensitive.

 

Chris



#14 Kon Dealer

Kon Dealer

    Viking 1

  • -----
  • Posts: 991
  • Joined: 05 Jan 2011
  • Loc: Cambridge UK

Posted 11 February 2020 - 06:41 PM

Agreed.

I should have added the caveat that my eyes are sensitive to CA.The Kson 102 ED may suit others who are not so sensitive.

 

Chris



#15 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 81,676
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 11 February 2020 - 07:25 PM

I should have added the caveat that my eyes are sensitive to CA.The Kson 102 ED may suit others who are not so sensitive.

 

Chris

 

Agreed.

 

As I recall, Michael and I did agree that his Kson 102 mm F/6 was not the TV NP-101 when it came to color correction but that for an affordable airline portable scope primarily used for deep sky,mit was plenty decent. 

 

 

Jon




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