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80mm F15 Achro Vs 80mm F10 ED ( FPL-53 and Lanthanum )

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#1 Dave1066

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Posted 08 March 2020 - 11:24 AM

Hi everyone,

 

So I'm thinking of selling my current collection of Achromat telescopes. To fund a StellaMira 80mm F10 ED FPL-53 and Lanthanum telescope, which is checked by one of the top telescope opticians in the UK.

 

All things being equal with selection, figuring, and polishing of the glass of the lens. Which would be better from a colour correction point of view? A 80mm F15 Achromat made from crown and flint or a 80mm F10 ED made of FPL-53 and Lanthanum? The main focus being on the F ratio and colour correction?

 

Best Regards

Dave



#2 Astrojensen

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Posted 08 March 2020 - 11:31 AM

The 80mm f/10 ED is going to have vastly superior color correction. 

 

 

Clear skies!
Thomas, Denmark


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#3 Dave1066

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Posted 08 March 2020 - 11:34 AM

Thanks Thomas, I was hoping you'd see this thread and reply.

 

The 80mm f/10 ED is going to have vastly superior color correction. 

 

 

Clear skies!
Thomas, Denmark


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#4 db2005

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Posted 08 March 2020 - 12:32 PM

When comparing my Vixen SD81S f/7.7 and my Vixen A80M f/11.4 achromat the SD81S wins hands down in terms of colour correction. The SD81 is reportedly using FPL53 glass, and some seasoned and knowledgeable CN'ers speculate that it's using Lanthanum glass in the mating element, which makes the comparison particularly interesting in the context of the OP.


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#5 Jon Isaacs

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Posted 08 March 2020 - 12:43 PM

Just to put some numbers on it:

 

The chromatic blurr of an 80mm F/15 is about twice the diameter of the Airy disk.

 

The chromatic blur of an 80mm F/10 with a FPL-53 objective is about 60 percent the diameter of the Airy disk.  

 

Jon


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#6 25585

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Posted 08 March 2020 - 03:35 PM

When comparing my Vixen SD81S f/7.7 and my Vixen A80M f/11.4 achromat the SD81S wins hands down in terms of colour correction. The SD81 is reportedly using FPL53 glass, and some seasoned and knowledgeable CN'ers speculate that it's using Lanthanum glass in the mating element, which makes the comparison particularly interesting in the context of the OP.

Your SD and the Stellar Mira would be an interesting competition.


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#7 aa6ww

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Posted 08 March 2020 - 09:35 PM

have you considered a 102 F11 ED refractor:

 

https://www.altairas...cuser-467-p.asp

 

They seem to have highly rated optics and would be shorter then the F15 80mm which was one of your options, and less expensive then the 80 F10?

 

Just adding a little confusion to your mix.

 

...Ralph


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#8 SeattleScott

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Posted 08 March 2020 - 11:10 PM

Just to put some numbers on it:

The chromatic blurr of an 80mm F/15 is about twice the diameter of the Airy disk.

The chromatic blur of an 80mm F/10 with a FPL-53 objective is about 60 percent the diameter of the Airy disk.

Jon

So about 40% less CA, and a considerably shorter tube.

Scott
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#9 Dave1066

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Posted 09 March 2020 - 05:33 AM

Hi, 

 

Thanks for the responses guys. Yes I had considered the Altair 102mm ED F11. Do they come with a metal transport case? Altair say the telescope tube is 88cm with the binoviewers section removed. If it does come with a case is there a provision to transport the telescope with the binoviewer section removed and stored in the case. Length is important for me from a transportation perspective. 

 

The Stellamira 80mm F10 is 80cm. The Altair is 88cm with the binoviewer section removed.



#10 Dave1066

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Posted 09 March 2020 - 08:40 AM

Update on this, well I tried to speak to Altair Astro today. To ask them my questions directly. They didn't actually answer any of my technical questions. The most detailed response I got was, that they don't have the 102ED F11 in stock and they didn't know when they would be getting it back in. I tried to get into a more detailed conversation with them, which wasn't that successful. They did not seem to respond to messages via the live chat window very quickly, even if I responded within 5 minutes of there response. I did get a response to one of my generic questions, which I now know that it does not come with a aluminium flight case. 

 

To be honest I was not impressed with this level of communication. I've read of other stories of a similar vein, from people that have had bad communication issues when trying to deal with Altair Astro directly. One person in the past having a bad experience when trying to deal with them in person at there premises. I would not advise going direct when dealing with Altair Astro, I'd go through a 2nd party seller like Harrison Telescopes. 

 

The above is one of the reasons why I've always aired on the side of caution when it comes to buying one of there telescopes. I've considered buying both the 125EDF F7.8 APO and 102ED F11. Since both their releases. 

 

First Light Optics on the other hand have very good customer service, and are trusted. Its FLO ( First Light Optics ) are the owners of the Stellamira range of telescope, Stellamira telescopes are tested by a top UK telescope Optician ES Reid. I'm definitely going to get the Stellamira 80mm ED F10 now.


Edited by Dave1066, 09 March 2020 - 08:51 AM.

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#11 Bomber Bob

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Posted 09 March 2020 - 08:44 AM

OP, you can get the same 102ED F11 refractor from T/S, and they're a great vendor.  


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#12 Bomber Bob

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Posted 09 March 2020 - 08:48 AM

My 2 cents:  I've owned quite a few 3" achromatics from F5 to F15.  And, I once owned an outstanding vintage Vixen FL80S fluorite.  I debated here on CN between a TS 102ED F11 and an Astro-Tech 102ED F7.  I went with the AT, and I've been thrilled with it.  In fact, it made my Vixen 80mm fluorite redundant, and I wound up selling it.

 

With the dewshield retracted, the AT102 was shorter than the Vixen 80mm.  It was almost as light.  Fine as the Vixen lens was (it had a better DPAC pattern), the AT102's extra aperture made resolution differences obvious.

 

Just some food for thought before you buy...

 

(Honestly, I think the future of 80mm fracs at F10 & higher isn't as bright, now that there are 100mm EDs at similar prices.)


Edited by Bomber Bob, 09 March 2020 - 08:49 AM.

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#13 db2005

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Posted 09 March 2020 - 09:51 AM


(Honestly, I think the future of 80mm fracs at F10 & higher isn't as bright, now that there are 100mm EDs at similar prices.)

I have been thinking about that too. But I find the 80mm refractors have a distinct yet somewhat unexpected advantage relative to their 100 mm siblings: less glass to acclimatize. When I observe under my skies and prevailing weather conditions I consistently find that my 3" scopes perform superbly after maybe 15-30 minutes while my 100 mm refractors still aren't performing at their best after more than an hour outside, displaying tube currents and noticeable astigmatism. Of course, YMMV, but the relatively smaller mass of 80mm scopes is a significant advantage in my book, at least for quick views.


Edited by db2005, 09 March 2020 - 09:51 AM.

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#14 Dave1066

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Posted 09 March 2020 - 09:57 AM

Hi Bomber Bob,

 

I had forgot about TS doing the exact same telescope. I have sent them an email about the 102mm ED F11. Hopefully it comes with an aluminium case. 

 

I get what you say about the whole 3" Vs 4" in regards to resolution. 4" gathers 63% more light than a 3". I am considering a 4" but for me the 3" is easier to transport. I own a motorcycle and sidecar. When I looked back through my astronomy sketches and records. The most used telescope is the 3", primarily at home. In fact some of the details I have garnered with the 3" has been pretty spectacular on Jupiter. If for example I were to consider the 102mm ED F7. I've have to sell some of my eyepieces, like the Brandon's as Brandon's don't work all that good at F7. I'd have to get some really short focal length eyepieces to achieve high magnification on the planets. Which I want to try and avoid the hassle and extra cost. 

 

Dave


Edited by Dave1066, 09 March 2020 - 10:05 AM.

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#15 aa6ww

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Posted 09 March 2020 - 12:05 PM

There is a padded soft case specifically for the 102mm F/11ED:

https://www.altairas...deluxe-99-p.asp

I prefer the soft cases for transporting and storage since I usually lie my telescope across the back seat of my car.

...Ralph
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#16 daquad

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Posted 17 March 2020 - 10:31 AM

The 80mm f/10 ED is going to have vastly superior color correction. 

 

 

Clear skies!
Thomas, Denmark

And, I'll bet, better mechanics.  That Stellamira is a beautiful looking scope.  If the optics are up to expectations it is a keeper, for sure.

 

Dom Q.


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#17 Astrojensen

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Posted 17 March 2020 - 03:47 PM

And, I'll bet, better mechanics.  That Stellamira is a beautiful looking scope.  If the optics are up to expectations it is a keeper, for sure.

 

Dom Q.

Mechanics are easy to fix or upgrade. 

 

 

Clear skies!
Thomas, Denmark


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#18 daquad

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Posted 20 March 2020 - 09:10 AM

Mechanics are easy to fix or upgrade. 

 

 

Clear skies!
Thomas, Denmark

True, but it's nice not to have to do it.  And upgrades add to the cost.

 

Dom Q.


Edited by daquad, 20 March 2020 - 09:13 AM.

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#19 25585

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Posted 20 March 2020 - 09:24 AM

Main rival against the Stellamira IMO, is the Vixen SD81S. Both near enough in price. 


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#20 Bomber Bob

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Posted 20 March 2020 - 10:18 AM

Hi Bomber Bob,

 

I had forgot about TS doing the exact same telescope. I have sent them an email about the 102mm ED F11. Hopefully it comes with an aluminium case. 

 

I get what you say about the whole 3" Vs 4" in regards to resolution. 4" gathers 63% more light than a 3". I am considering a 4" but for me the 3" is easier to transport. I own a motorcycle and sidecar. When I looked back through my astronomy sketches and records. The most used telescope is the 3", primarily at home. In fact some of the details I have garnered with the 3" has been pretty spectacular on Jupiter. If for example I were to consider the 102mm ED F7. I've have to sell some of my eyepieces, like the Brandon's as Brandon's don't work all that good at F7. I'd have to get some really short focal length eyepieces to achieve high magnification on the planets. Which I want to try and avoid the hassle and extra cost. 

 

Dave

I use a 7mm Nagler with my AT102ED for 100x; then, add a 2.5x APO Barlow for 250x.  This scope stays sharp & bright at 75x / inch, so that magnification is no problem.  You may find that some of your current eyepieces work well with a "short" ED -- it's been trial & error for my collection...

 

I get what you're saying about portability.  My 1940s Tinsley EQ could carry a 10" Newt or 12" Cassegrain, but since my surgery, there's no way I could hoist either up to the cradle!  I have to be careful with my APM 152ED, and it's less than 25 pounds.


Edited by Bomber Bob, 20 March 2020 - 10:23 AM.

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#21 AstroKerr

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Posted 20 March 2020 - 01:56 PM

Got both f/7 & f/11 102EDs mentioned & an f/13.2 achro (none came with cases) - love'em all, all keepers, all have 'realms'. But achro ain't really in the game, other than looking cool. The 102EDs are transportable enough for me and acclimatize quick enough working out of the house, but there are times an 80ED f/10 would hit a sweet spot grab-n-go to the yard or down the road to darker skies.

 

The Stellamira / long Pern 80 f/10 - if you want the portability, quicker acclimitization and don't need the extra aperture (or weight) I do believe you are on the right path. ED & f/10! Jon's numbers say a lot. These days, that's a scope to have in 80mm 'just in case' because they can become 'unavailable' without warning. And they are a very nice build.

 

Anyways, you gotta satisfy your needs and curiosity and looks to me you're thinkin' smart for your needs. Smart enough I feel the need to copy-cat & grab one this year as well.

 

Side note: Thanks also for the thread because:

  • when I went looking, I found the Long Pern site. There I bumped into the S400M-Cs. Nice, because while waiting for AT60EDs to get in, I've acquired an AT66ED from aa5te (due in Monday) and they look to be the same (or mighty close), which is handy if I need a newer one.
  • I'm looking to bracket my 60 achros, classic and contemp, with EDs before downsizing to a 'reference set' with an AT60/66ED on the fast side and maybe a Tak FOA-60Q on the slower side. This discussion on 80s has been a help towards that and a similar plan for my 80s.

As always, Thank You all for sharing - I always learn good things here.

 

Clear Skies, Sharp Eyes, Health & Peace,

 

waytogo.gif


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#22 Dave1066

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Posted 20 March 2020 - 03:29 PM

Thanks for the replies guys,

 

25585, the Vixen is a great call, but its too fast for my liking at F7.7, plus that might be a challenge for some of my eyepieces. I had a Vixen 80mm F15 which I compared to my Circle T 80mm F15. The Circle T performed better on planets. 

 

Bomber Bob, I do have an old barlow somewhere, which came with my Circle T 80mm, never used it. But never say never, having said that I'm more of a minimal glass guy. I'm actually going to be making my own 7.4mm sphere eyepiece, hopefully to use on Mars this October.

 

Astro Kerr, that's some good information. The Stellamira is a heavy little beast, they are high quality heavy duty build, compared to more normal average scopes. I believe the 80mm Stellamira weights the same as the 102ED F11. Which doesn't surprise me, as my Skylight 60mm F16.7 weights the same or more than my Circle T 80mm F15. 

 

Yep I'm not hanging around on the Stellamira, thats why I am selling my 102mm F15 and Circle T 80mm F15. To get the Stellamira 80mm quickly. Don't want it to disappear. In my Planetary Observers Handbook, the author states the ultimate telescope would be an ED glass refractor which has a slow focal ratio.

 

I think the Takahashi FOA-60Q would be a very good choice, I've considered it. Lets us know how you get on if you get one!?

 

Dave


Edited by Dave1066, 20 March 2020 - 06:42 PM.

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#23 barbie

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Posted 20 March 2020 - 05:37 PM

Based on what I've observed thus far with my 76mm F12 Takahashi Fluorite doublet apochromat, I would agree with all of the above and highly suggest the 60mm Tak or the 80mm F10 ED!!


Edited by barbie, 20 March 2020 - 05:38 PM.

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#24 daquad

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Posted 20 March 2020 - 06:45 PM

Thanks for the replies guys,

 

25585, the Vixen is a great call, but its to fast for my liking at 7.7, plus that might be a challenge for some of my eyepieces. I was had a Vixen 80mm F15 which I compared to my Circle T 80mm F15. The Circle T performed better on planets. 

 

Bomber Bob, I do have an old barlow somewhere, which came with my Circle T 80mm, never used it. But never say never, having said that I more of a minimal glass guy. I'm actually going to be making my own 7.4mm sphere eyepiece, hopefully to use on Mars this October.

 

Astro Kerr. That's some good information. The Stellamira is a heavy little beast, they are high quality slightly heavy duty build compared to you more normal average build scopes. I believe the 80mm Stellamira weights the same as the 102ED F11. Which doesn't surprise me, as my Skylight 60mm F16.7 weights the same or more than my Circle T 80mm F15. 

 

Yep I'm not hanging around on the Stellamira, thats why I am selling my 102mm F15 and Circle T 80mm F15. To get the Stellamira 80mm quickly. Don't want it to disappear. In my Planetary Observers Handbook, the author states the ultimate telescope would be an ED glass refractor which has a slow focal ratio.

 

I think the Takahashi FOA-60Q would be a very good choice, I've considered it. Lets us know how you get on if you get one!?

 

Dave

 

Dave

I'd sell my Jaegers 102" f/15.4 achromat and my AT 102 f/7 ED  for a Stellamira 102 f/10 FPL 53, but not for an 80 mm.  I don't think the difference in color correction could make up for the difference in aperture for resolution or deep sky.

 

Dom Q.

 


Edited by daquad, 20 March 2020 - 06:45 PM.

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