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

Visual and AP Difference between these two SV scopes

astrophotography dslr imaging optics refractor
  • Please log in to reply
23 replies to this topic

#1 marinaldi

marinaldi

    Vostok 1

  • -----
  • topic starter
  • Posts: 136
  • Joined: 29 Sep 2015
  • Loc: San Francisco, CA

Posted 16 May 2019 - 08:18 PM

Hi,   This is probably a dumb question but can all you AP refractor sages opine on what the likely difference is between

the two Stellarvue refractors below.

 

1. SVX130T Premier Apochromatic Triplet

2. SVX125D Premier Apochromatic Doublet

 

First the obvious, 

 

a. Slightly different objective size, 125mm vs 130mm

b. APO doublet versus APO Triplet 

c. Both SVX, therefore

c. both have superb strehl numbers (0.98-0.996)

d. $2595 vs $4995   !!!!!! Whew

 

From reading the descriptions it seems like the main difference in cost comes from the extra Lanthanum optics element that purports to deliver "color free, high contrast performance".   

 

I realize that the 125D is mainly meant for visual observations while the 130 is an AP instrument.

 

But, my question is If I added a field flattener reducer to the 125D and the same to the 130T what would the difference be in the resulting AP images?  I know this is a rather subjective and ambiguous question but I'm trying to figure out why anyone would pay 2x the price.  Would AP images be that much better?

 

Thanks, Mike


Edited by marinaldi, 16 May 2019 - 08:35 PM.


#2 ngc7319_20

ngc7319_20

    Viking 1

  • *****
  • Posts: 685
  • Joined: 25 Oct 2015
  • Loc: MD

Posted 16 May 2019 - 09:29 PM

The triplet should have less chromatic aberration for both visual (think double stars and planetary viewing) and for AP (less red and blue halos on stars).  Images wont be *twice* better.  Just depends how much you are willing to pay for an extra measure of performance.



#3 HydrogenAlpha

HydrogenAlpha

    Mariner 2

  • -----
  • Posts: 200
  • Joined: 02 Oct 2014
  • Loc: Singapore

Posted 17 May 2019 - 02:37 AM

The doublet is likely to have some noticeable level of chromatic aberration, no matter what sort of exotic glass is used. A doublet is workable for AP, but if you decide to add a reducer, or want to boost colour saturation, CA will be more significant consideration. 

 

Also, strehl numbers (especially monochromatic) doesn't mean much, and it doesn't give an indication of how good the colour correction is. 

 

Ultimately, both scopes can be used for AP. It is just how well you tolerate the CA, and you can get a rough indication of the difference in performance of both scopes by looking for samples on astrobin. 


  • marinaldi likes this

#4 junomike

junomike

    Hubble

  • *****
  • Moderators
  • Posts: 16296
  • Joined: 07 Sep 2009
  • Loc: Ontario

Posted 17 May 2019 - 06:42 AM

For more visual use the Doublet will be fine (but not perfect) for CA control and will acclimate faster, however the color correction and overall image (contrast, detail, etc) will be better in the Triplet that

will take longer to acclimate.


  • marinaldi likes this

#5 Erik Bakker

Erik Bakker

    Cosmos

  • *****
  • Moderators
  • Posts: 7761
  • Joined: 10 Aug 2006
  • Loc: Netherlands, Europe

Posted 17 May 2019 - 07:07 AM

The only way to really answer your question is to side-by-side them under the star over a few nights.

 

Perhaps we can assume beforehand that sample-sample variation is low if these high Strehl numbers are guaranteed.

 

Generally, there are few free lunches on this planet, especially in a commercial environment.


  • marinaldi likes this

#6 rustynpp

rustynpp

    Apollo

  • *****
  • Posts: 1490
  • Joined: 27 Aug 2004
  • Loc: NYC

Posted 17 May 2019 - 07:15 AM

The doublet is likely to have some noticeable level of chromatic aberration, no matter what sort of exotic glass is used.

 

If I paid $2600 for a Stellarvue 5" f/7.8 doublet with FCD100 glass, I would be very upset to find any in-focus color at all, on any subject. My Z103 shows no in-focus color, at least to my eyes. I don't see why the SV would be any different.


  • marinaldi likes this

#7 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 76441
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 17 May 2019 - 07:41 AM

If I paid $2600 for a Stellarvue 5" f/7.8 doublet with FCD100 glass, I would be very upset to find any in-focus color at all, on any subject. My Z103 shows no in-focus color, at least to my eyes. I don't see why the SV would be any different.

 

For a given design, color correction scales with focal ratio/aperture.  I am sure someone can see in focus chomatic aberration in a Z103 and I am sure someone can see in focus chromatic aberration in the SV 125 Access.  It's not a question of how much one pays, it's a question of what is possible optically.  

 

There are reasons why there are triplets, particularly in the larger apertures.  

 

Jon


  • marinaldi likes this

#8 HydrogenAlpha

HydrogenAlpha

    Mariner 2

  • -----
  • Posts: 200
  • Joined: 02 Oct 2014
  • Loc: Singapore

Posted 17 May 2019 - 10:20 AM

If I paid $2600 for a Stellarvue 5" f/7.8 doublet with FCD100 glass, I would be very upset to find any in-focus color at all, on any subject. My Z103 shows no in-focus color, at least to my eyes. I don't see why the SV would be any different.


Just to clarify, I'm referring to it as an imaging platform. I don't doubt that you'd be hard pressed to find colour for visual in-focus
  • Jon Isaacs and rustynpp like this

#9 marinaldi

marinaldi

    Vostok 1

  • -----
  • topic starter
  • Posts: 136
  • Joined: 29 Sep 2015
  • Loc: San Francisco, CA

Posted 17 May 2019 - 10:27 AM

Thanks to all of you for your input!  I sort of figured it was a matter 'slight' (hopefully) differences in CA.  Now whether this would bother me is not yet known.  I'll try to find some 125D images on astrobin and see what is possible.



#10 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 76441
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 17 May 2019 - 10:32 AM

Thanks to all of you for your input!  I sort of figured it was a matter 'slight' (hopefully) differences in CA.  Now whether this would bother me is not yet known.  I'll try to find some 125D images on astrobin and see what is possible.

 

It's likely they will have been processed to reduce the false color.   You might look at the 120 mm F/7.5 Eon thread . Helder has some nice photos.   

 

Will this be your first attempt at astrophotography ?

 

Jon


  • HydrogenAlpha likes this

#11 marinaldi

marinaldi

    Vostok 1

  • -----
  • topic starter
  • Posts: 136
  • Joined: 29 Sep 2015
  • Loc: San Francisco, CA

Posted 17 May 2019 - 10:45 AM

It's likely they will have been processed to reduce the false color.   You might look at the 120 mm F/7.5 Eon thread . Helder has some nice photos.   

 

Will this be your first attempt at astrophotography ?

 

Jon

Thanks Jon,  I'll take a look Helder.  No it will not be my first attempt.  I'm currently using a SV 70mm scope for imaging, which I love.  I just bought an Orion mini guider to improve tracking so I'm still trying to learn some more details.  I'm finding that I like to photograph galaxies so I thought I'd get more interesting images with a larger objective.   At this point the 125D SVX is more of a wish-for scope.  I'd be stretching my budget enough with spending $2500 on it but may do it later this year. 

 

Mike 



#12 HydrogenAlpha

HydrogenAlpha

    Mariner 2

  • -----
  • Posts: 200
  • Joined: 02 Oct 2014
  • Loc: Singapore

Posted 17 May 2019 - 10:48 AM

It's likely they will have been processed to reduce the false color.   You might look at the 120 mm F/7.5 Eon thread . Helder has some nice photos.   

 

Will this be your first attempt at astrophotography ?

 

Jon

Oh yes, I think this point needs to be stressed as well. The sample images I suggested are only a rough guide, because indeed false colour can be reduced in processing. On the flipside, this also means that with proper processing technique, the most obvious effects of CA can be reduced in the final image (which is probably what matters at the end of the day)


  • marinaldi likes this

#13 HydrogenAlpha

HydrogenAlpha

    Mariner 2

  • -----
  • Posts: 200
  • Joined: 02 Oct 2014
  • Loc: Singapore

Posted 17 May 2019 - 10:56 AM

Thanks Jon,  I'll take a look Helder.  No it will not be my first attempt.  I'm currently using a SV 70mm scope for imaging, which I love.  I just bought an Orion mini guider to improve tracking so I'm still trying to learn some more details.  I'm finding that I like to photograph galaxies so I thought I'd get more interesting images with a larger objective.   At this point the 125D SVX is more of a wish-for scope.  I'd be stretching my budget enough with spending $2500 on it but may do it later this year. 

 

Mike 

I feel that stars in galaxy images tend to be easier to handle, because most galaxies can only be seen outside of the plane of the Milky Way where the starfield is less dense. Also, if you're shooting galaxies, I would assume that you wouldn't be putting a reducer on it since you want to maximise resolution. In which case, the CA is more likely to be manageable, especially since the 125D is a rather slow f/7.8. 

 

However, imaging at ~1000mm of FL is going to be considerably more difficult in terms of tracking accuracy compared to the SV70, so whether your mount is capable of handling it well is another important consideration.  


  • marinaldi likes this

#14 johnsoda

johnsoda

    Viking 1

  • *****
  • Posts: 790
  • Joined: 30 May 2014
  • Loc: SW Ohio, USA

Posted 17 May 2019 - 11:02 AM

I own a SVX130T. I haven’t seen a SVX125D, but I don’t think anyone not working for Stellarvue has. I’m very happy with the 130. I was lucky to buy it before the $1000 price increase. I would guess that CA would be practically nil for visual with the doublet. I write “practically” because you could probably see some if you really want to under conditions you won’t care about much anyway. For imaging, there would probably be more of an issue, but I think you could deal with it. For narrowband, there’s virtually no issue.

I would strongly disagree with the statement that Strehl doesn’t matter. No one number tells the whole optical story, but Strehl does give a good general idea of optical quality.

There are a couple of real advantages to a doublet, other than price. When you pick up my triplet OTA, it’s a little bit of a shock how unbalanced it feels. This is easily dealt with, but there’s a lot of glass up front. Also, the thermal stabilization should be quicker with the doublet, perhaps much quicker.

Whatever you buy, I’m sure you’ll have many hours of enjoyment with it. Stellarvue puts out fine products and has exemplary customer service.
  • marinaldi likes this

#15 HydrogenAlpha

HydrogenAlpha

    Mariner 2

  • -----
  • Posts: 200
  • Joined: 02 Oct 2014
  • Loc: Singapore

Posted 17 May 2019 - 11:42 AM

I would strongly disagree with the statement that Strehl doesn’t matter. No one number tells the whole optical story, but Strehl does give a good general idea of optical quality.

Just to qualify my statement and avoid any confusion, I was mainly alluding to CA, in which case Strehl doesn't give a particularly useful indication. In terms of other forms of optical aberrations, it is indeed a useful number. 


Edited by HydrogenAlpha, 17 May 2019 - 11:47 AM.

  • marinaldi likes this

#16 marinaldi

marinaldi

    Vostok 1

  • -----
  • topic starter
  • Posts: 136
  • Joined: 29 Sep 2015
  • Loc: San Francisco, CA

Posted 17 May 2019 - 11:48 AM

I own a SVX130T. I haven’t seen a SVX125D, but I don’t think anyone not working for Stellarvue has. I’m very happy with the 130. I was lucky to buy it before the $1000 price increase. I would guess that CA would be practically nil for visual with the doublet. I write “practically” because you could probably see some if you really want to under conditions you won’t care about much anyway. For imaging, there would probably be more of an issue, but I think you could deal with it. For narrowband, there’s virtually no issue.

I would strongly disagree with the statement that Strehl doesn’t matter. No one number tells the whole optical story, but Strehl does give a good general idea of optical quality.

There are a couple of real advantages to a doublet, other than price. When you pick up my triplet OTA, it’s a little bit of a shock how unbalanced it feels. This is easily dealt with, but there’s a lot of glass up front. Also, the thermal stabilization should be quicker with the doublet, perhaps much quicker.

Whatever you buy, I’m sure you’ll have many hours of enjoyment with it. Stellarvue puts out fine products and has exemplary customer service.

Thanks for the POV!  I'm a big Stellarvue fan as well and wanted to stick with the brand.  Besides SV is a 2 hour drive from the Bay Area so I can run up there if need be.  On a thread by Helder that was pointed out to me the author mentioned that his next scope would be a TS Photoline 130.  Including shipping VAT tax this looks to be about $400 cheaper than the 125D SVX.  Also it is a APO Triplet with FPL53 glass rather than a Doublet.  Have you heard of this scope and/or have any opinions about it?  I read about it from the this thread


Edited by marinaldi, 17 May 2019 - 11:51 AM.


#17 RadioAstronomer

RadioAstronomer

    Vostok 1

  • *****
  • Posts: 159
  • Joined: 13 Jun 2018
  • Loc: Ft. Lauderdale, FL

Posted 17 May 2019 - 11:52 AM

I'm looking forward to reading reviews and reports on the SVX 125D. I'm really interested in this scope. Has anybody gotten one yet? I also noticed that the coating on the objective has a purple hue vs the regular SV 125 access has the classic China green coatings. Perhaps SV applies their own coatings to these premier objectives?


Edited by RadioAstronomer, 17 May 2019 - 11:52 AM.


#18 HydrogenAlpha

HydrogenAlpha

    Mariner 2

  • -----
  • Posts: 200
  • Joined: 02 Oct 2014
  • Loc: Singapore

Posted 17 May 2019 - 11:53 AM

Thanks for the POV!  I'm a big Stellarvue fan as well and wanted to stick with the brand.  Besides SV is a 2 hour drive from the Bay Area so I can run up there if need be.  On a thread by Helder that was pointed out to me the author mentioned that his next scope would be a TS Photoline 130.  Including shipping VAT tax this looks to be about $400 cheaper than the 125D SVX.  Also it is a APO Triplet rather than a Doublet.  Have you heard of this scope and/or have any opinions about it?  I read about it from the this thread

It should be mostly identical to the SVX130T, as both are produced by the same OEM (Kunming United Optics). However, the TS version claims to use FPL-53 (or equivalent), which has stirred some controversy in the forums. 

 

You'd be paying quite a fair bit of premium on the SV for what is essentially the same scope, but in SV's case I believe that they guarantee Strehl values and as such has a higher rejection rate compared to other UO rebranders like TS. However, I trust TS's product lines, and given the price difference between the two, I'd pick the TS anyday (but this is a personal choice). 

 

Other UO rebranders include Astro-Tech (AT130EDT), Altair Astro (Wave Series 130 F7), and Orion (EON 130mm ED triplet). But note that all of these advertise the scope as using FPL-51 (or equiv.) glass. 


Edited by HydrogenAlpha, 17 May 2019 - 12:04 PM.

  • marinaldi likes this

#19 johnsoda

johnsoda

    Viking 1

  • *****
  • Posts: 790
  • Joined: 30 May 2014
  • Loc: SW Ohio, USA

Posted 17 May 2019 - 12:00 PM

If I lived two hours from Stellarvue, I’d definitely get their scope, even at the higher price. However, that’s strictly a personal opinion. Another thing about the SVX130T: the focuser is outstanding. That’s not just my opinion. It’s the opinion of Jeff Dickerman from Optec, who knows focusers. I assume the 125D has a similar, albeit smaller, focuser. Whatever you buy, have fun with it!
  • marinaldi likes this

#20 marinaldi

marinaldi

    Vostok 1

  • -----
  • topic starter
  • Posts: 136
  • Joined: 29 Sep 2015
  • Loc: San Francisco, CA

Posted 17 May 2019 - 12:50 PM

If I lived two hours from Stellarvue, I’d definitely get their scope, even at the higher price. However, that’s strictly a personal opinion. Another thing about the SVX130T: the focuser is outstanding. That’s not just my opinion. It’s the opinion of Jeff Dickerman from Optec, who knows focusers. I assume the 125D has a similar, albeit smaller, focuser. Whatever you buy, have fun with it!

Thanks,  I'll look into it the focuser.  



#21 marinaldi

marinaldi

    Vostok 1

  • -----
  • topic starter
  • Posts: 136
  • Joined: 29 Sep 2015
  • Loc: San Francisco, CA

Posted 17 May 2019 - 12:54 PM

It should be mostly identical to the SVX130T, as both are produced by the same OEM (Kunming United Optics). However, the TS version claims to use FPL-53 (or equivalent), which has stirred some controversy in the forums. 

 

You'd be paying quite a fair bit of premium on the SV for what is essentially the same scope, but in SV's case I believe that they guarantee Strehl values and as such has a higher rejection rate compared to other UO rebranders like TS. However, I trust TS's product lines, and given the price difference between the two, I'd pick the TS anyday (but this is a personal choice). 

 

Other UO rebranders include Astro-Tech (AT130EDT), Altair Astro (Wave Series 130 F7), and Orion (EON 130mm ED triplet). But note that all of these advertise the scope as using FPL-51 (or equiv.) glass. 

Thanks again for the POV.  Stellarvue grind their own lenses so by KUO do you mean the glass blanks?  



#22 HydrogenAlpha

HydrogenAlpha

    Mariner 2

  • -----
  • Posts: 200
  • Joined: 02 Oct 2014
  • Loc: Singapore

Posted 17 May 2019 - 12:59 PM

Thanks again for the POV.  Stellarvue grind their own lenses so by KUO do you mean the glass blanks?  

Frankly, I'm not exactly sure, so in this regard I'll probably let somebody else chime in or correct me on this. 



#23 photoracer18

photoracer18

    Vanguard

  • *****
  • Posts: 2481
  • Joined: 02 Sep 2013
  • Loc: Martinsburg, WV

Posted 17 May 2019 - 04:38 PM

If I paid $2600 for a Stellarvue 5" f/7.8 doublet with FCD100 glass, I would be very upset to find any in-focus color at all, on any subject. My Z103 shows no in-focus color, at least to my eyes. I don't see why the SV would be any different.


Cameras are different than eyes. Everyone's eyes have different color perception without being color blind. Some people see CA and PF and some don't. Does not mean your scope has zero color if you don't see any it just means your eyes can't perceive it or notice it. As for the doublet being color free or an APO that is a slight misconception. Almost all current doublets use a Lanthanum flint element. Lanthanum elements have a slight yellow tint to them caused by the Lanthanum in the glass. What this does is filter out some of the blue light, and therefore eliminate some or most of the blue fringing. This optical configuration goes back to the Stellarvue SV102ABV, built by LOMO 15 years or more ago on their own. Does not mean you could not image with one of these, just remember the camera will not be getting as much blue light as a triplet (they don't need to use a Lanthanum element in a triplet). Everyone who puts out a doublet over 100mm is using this formula today. Only the companies that don't put out doublets are not. Does not matter what the LD element is, OK-4, FPL-51/53/55, or FCD1/100.
And you will notice I actually own an SV102ABV (#0086) and an older non-current SVA130T (#0002 in fact).

Edited by photoracer18, 17 May 2019 - 04:44 PM.

  • Erik Bakker, Live_Steam_Mad and marinaldi like this

#24 dscarpa

dscarpa

    Soyuz

  • *****
  • Posts: 3652
  • Joined: 15 Mar 2008
  • Loc: San Diego Ca.

Posted 17 May 2019 - 06:01 PM

Before the big price increase  SV told me the SVX 130DT could be ordered with the smaller focuser to save weight and money given AP isn't within my skill set. I'd imagine the SVX 125D could be ordered with the bigger one. At the time on the SVX 102T scopes it was a $300 option. The price of the SVX 125D has already gone up $100. I wouldn't be shocked if it increases again at some point in the not too distant future.  David  


Edited by dscarpa, 17 May 2019 - 06:04 PM.



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





Also tagged with one or more of these keywords: astrophotography, dslr, imaging, optics, refractor



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics