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80mm ED f/10 FPL-53 & Lanthanum

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#1 vilchez

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Posted 31 January 2020 - 01:47 PM

I just saw it, manufactured by LongPerng.

 

 

https://www.firstlig...-telescope.html

stellamira_80mm_f10_classic_ed_telescope


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#2 Nakedgun

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Posted 31 January 2020 - 02:48 PM

At f/10 it has the potential to be a fine performer.

 

I prefer doublets, and if I had not a Fluorite doublet in that aperture range already, I might consider it.



#3 F.Meiresonne

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Posted 31 January 2020 - 03:16 PM

strange scope. At F/10 this is real slow one. Wonder why. My FPL53 102 mm does just fine, no color....

 

Looks very good though, but a bit of a long tube.


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#4 Jond105

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Posted 31 January 2020 - 04:48 PM

strange scope. At F/10 this is real slow one. Wonder why. My FPL53 102 mm does just fine, no color....

 

Looks very good though, but a bit of a long tube.

I think it’s because the ED80 with FPL-53 at f/7.5  will eventually show a little fringe, you add that same glass to f/10, and I bet it’s virtually color free. 
 

At $900 though I’d still choose the Skywatcher 100ED. Just my thoughts about the price. Otherwise it be nice to try since I prefer longer focal length refractors. 


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#5 MalVeauX

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Posted 31 January 2020 - 04:53 PM

An 80mm F10 achromat is already considered minimal to no CA by Sidgwick standard (CA ratio is 3.18). Throw in FPL53 glass, and it should literally be truly APO, minus the 3rd element (not that all triplet are truly APO either though, they're not!).

 

Very best,


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#6 eros312

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Posted 31 January 2020 - 05:16 PM

I think it’s because the ED80 with FPL-53 at f/7.5  will eventually show a little fringe, you add that same glass to f/10, and I bet it’s virtually color free. 
 

At $900 though I’d still choose the Skywatcher 100ED. Just my thoughts about the price. Otherwise it be nice to try since I prefer longer focal length refractors. 

My calculations indicate about $990 plus shipping. Export price would be about £750


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#7 Tyson M

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Posted 31 January 2020 - 07:35 PM

An 80mm F10 achromat is already considered minimal to no CA by Sidgwick standard (CA ratio is 3.18). Throw in FPL53 glass, and it should literally be truly APO, minus the 3rd element (not that all triplet are truly APO either though, they're not!).

Very best,

Skywatcher 100ed still has some color if you know where to look. Not obtrusive or a dealbreaker at all. If you like smaller mounts to get outside more often then a long focal length 80mm is an ideal choice for visual.
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#8 HARRISON SCOPES

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Posted 31 January 2020 - 07:44 PM

I'd guess the 80 long pern weighs more than the SW100 ED, like for like.

Edited by HARRISON SCOPES, 31 January 2020 - 07:52 PM.


#9 Jond105

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Posted 31 January 2020 - 07:50 PM

I'd bet the 80 long pern weighs more than the SW100 ED, like for like.


Curiosity, because of the focuser, rings, and says 15” dovetail?

#10 YAOG

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Posted 31 January 2020 - 08:23 PM

strange scope. At F/10 this is real slow one. Wonder why. My FPL53 102 mm does just fine, no color....

 

Looks very good though, but a bit of a long tube.

If your 102mm f/7 FPL-53 scope is a doublet it has some color, even the Vixen ED100S f/9 has some color. 



#11 25585

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Posted 01 February 2020 - 03:16 AM

No colour = Tak DL in 100mm. Though my 100 Equinox is only beaten at higher magnifIcations.


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#12 F.Meiresonne

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Posted 01 February 2020 - 03:43 AM

If your 102mm f/7 FPL-53 scope is a doublet it has some color, even the Vixen ED100S f/9 has some color. 

Could not see it so far although technically it should be there, and i expected to see some.

 

But so far no...visually i see no rim either yellow or blue on the moon at 178x, still find it hard to believe.

 

Also on pictures the stars have not the slightest blue halo.

 

I am not the only one. A German imager bought thesame scope as mine and the 80 mm counterpart. Could not see it either.

 

 

the scope is advertised as 'virtualy without color'..., my opinion we could stick to that claim....

 

I like the scope a lot for me it is more then good enough, got more then i bargained for.

 

This said my FPL51 70 mm F/6 is quite different, fine for daylight but there you can see clearly still CA, not bothersome and reduced, but it is  there. For AP this is getting worser, blue halo around every star...imo not suited . But for visual a fine thing though.


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#13 Astrojensen

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Posted 01 February 2020 - 05:48 AM

Everyone talks about color correction, as if it's the only thing in a refractor, but there are other reasons to go with a long focal length, other than achieving a bit better color correction:

 

- spherical aberration gets much easier to control

- spherochromatism becomes MUCH easier to control

- curves get gentler, making manufacturing easier, making it much more likely that the lens is of high quality

- collimation becomes much less critical

- an objective with gentler curves suffer less from aberrations during cooldown, because a difference in temperature between the front and rear lens(es) introduces less spherical aberration and spherochromatism in an objective with gently curved lenses, than one with strong curves. 

 

 

Clear skies!
Thomas, Denmark


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#14 YAOG

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Posted 01 February 2020 - 01:15 PM

Everyone talks about color correction, as if it's the only thing in a refractor, but there are other reasons to go with a long focal length, other than achieving a bit better color correction:

 

- spherical aberration gets much easier to control

- spherochromatism becomes MUCH easier to control

- curves get gentler, making manufacturing easier, making it much more likely that the lens is of high quality

- collimation becomes much less critical

- an objective with gentler curves suffer less from aberrations during cooldown, because a difference in temperature between the front and rear lens(es) introduces less spherical aberration and spherochromatism in an objective with gently curved lenses, than one with strong curves. 

 

 

Clear skies!
Thomas, Denmark

Thomas,

 

The problem IMO is that once you understand what you are seeing and can identify the type of aberration you are seeing you can't un-see them and start to notice and look for aberrations everywhere, yours and other people's scopes. Most people cannot see anything amiss because they don't know what to look for. But once you have seen and understand how to break down the different types of aberrations that you are seeing it becomes like a mental disorder and you can't stop looking at them. It makes you nuts. 

 

Don't type on your phone! 


Edited by YAOG, 01 February 2020 - 03:37 PM.

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#15 Astrojensen

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Posted 01 February 2020 - 02:13 PM

Thomas,

 

The problem IMO is that once you understand what you are seeing and can identify the type of abberation you are seeing you can't un-see it and start to notice and then look for abberations everywhere. Most people cannot see it because they don't know what to look for. But once you have seen and understand it how to break down what you are seeing it becomes like a mental disorder and you can't stop looking.

This is true, but the aberrations don't go away, just because you don't know what to look for. 

 

 

Clear skies!
Thomas, Denmark


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#16 YAOG

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Posted 01 February 2020 - 03:38 PM

This is true, but the aberrations don't go away, just because you don't know what to look for. 

 

 

Clear skies!
Thomas, Denmark

Yes, that's the problem! They are there doing their damages even if you are not aware of the aberrations. 



#17 Scott Beith

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Posted 01 February 2020 - 07:46 PM

That should be a fine little scope for the Moon and double stars.  waytogo.gif


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#18 AndresEsteban

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Posted 02 February 2020 - 12:50 AM

Everyone talks about color correction, as if it's the only thing in a refractor, but there are other reasons to go with a long focal length, other than achieving a bit better color correction:

 

- spherical aberration gets much easier to control

- spherochromatism becomes MUCH easier to control

- curves get gentler, making manufacturing easier, making it much more likely that the lens is of high quality

- collimation becomes much less critical

- an objective with gentler curves suffer less from aberrations during cooldown, because a difference in temperature between the front and rear lens(es) introduces less spherical aberration and spherochromatism in an objective with gently curved lenses, than one with strong curves. 

 

 

Clear skies!
Thomas, Denmark

Right on the spot Thomas! Unfortunately, our colleagues easily forget the benefits of long focus refractors! But, as we go thorugh an era of ultrashort focus refractors, basically oriented to astrophoto and big budgets... nobody wants to hear of all the other characteristics that get  dramatically improved as you increase focal ratio!
That's why I say: Long live to long focus refractors!!!

Regards and clear skies for us all!
Andy


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#19 Gregory Gross

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Posted 02 February 2020 - 01:33 PM

Thanks for staring this thread, vilchez! FLO's image is the first decent view I've had of this scope.
 
There are a few related discussion threads I've been keeping my eye on:

On the Long Perng website, there are two variations of this scope:

Along with FLO in Britain, our friends at Ontario Telescope and Accessories in Canada are also retailing the Starfield-branded version of this scope with rack and pinion focuser. I wonder how long it'll take a US-based reseller to pick up this model, if ever.

 

I'm excited about the emergence of this model. I'm finding that the number of sub-100mm long-focus refractor models with premium glass on the market is small. Surely I'm not the only one who is looking for a well-made long-focus refractor to use on a lightweight mount, right? This may be my ticket especially for first-rate full-disk views of the Moon and, with proper filtering, the Sun.

 

If anyone has an idea of the weight of this scope, I'd appreciate learning it. Nowhere do any of the spec listings that I've seen for this scope indicate weight. I assume that it's comparable to, say, a SW 100ED. I would also imagine that the shorter tube will help with stability on a lighter mount.



#20 Tyson M

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Posted 02 February 2020 - 01:40 PM

Thanks for staring this thread, vilchez! FLO's image is the first decent view I've had of this scope.
 
There are a few related discussion threads I've been keeping my eye on:

On the Long Perng website, there are two variations of this scope:

Along with FLO in Britain, our friends at Ontario Telescope and Accessories in Canada are also retailing the Starfield-branded version of this scope with rack and pinion focuser. I wonder how long it'll take a US-based reseller to pick up this model, if ever.

 

I'm excited about the emergence of this model. I'm finding that the number of sub-100mm long-focus refractor models with premium glass on the market is small. Surely I'm not the only one who is looking for a well-made long-focus refractor to use on a lightweight mount, right? This may be my ticket especially for first-rate full-disk views of the Moon and, with proper filtering, the Sun.

 

If anyone has an idea of the weight of this scope, I'd appreciate learning it. Nowhere do any of the spec listings that I've seen for this scope indicate weight. I assume that it's comparable to, say, a SW 100ED. I would also imagine that the shorter tube will help with stability on a lighter mount.

I was always curious about Long Perng website depictions regarding these models.  The crayford focuser shows the DPAC in blue light with this scope and it appears very good with jailbar straight lines.  The rack and pinion focuser model does not have the DPAC image.

 

I assume both scopes have the same quality of optics and the rack and pinion model would be more expensive, but it could be interpreted as the crayford model might have better optics.



#21 Gregory Gross

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Posted 02 February 2020 - 01:47 PM

The only other difference I could see between the two versions of this scope on the Long Perng website is that the verbiage for the Crayford version specifically lists lanthanum whereas that for the R&P version does not. I imagine that this is maybe an inadvertent omission in the case of the latter.

 

I also assume the optics to be identical between the two. Why would Long Perng go for lesser optics on the model with the better focuser?


Edited by Gregory Gross, 02 February 2020 - 01:49 PM.

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#22 Tyson M

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Posted 02 February 2020 - 01:56 PM

The only other difference I could see between the two versions of this scope on the Long Perng website is that the verbiage for the Crayford version specifically lists lanthanum whereas that for the R&P version does not. I imagine that this is maybe an inadvertent omission in the case of the latter.

 

I also assume the optics to be identical between the two. Why would Long Perng go for lesser optics on the model with the better focuser?

I asked what version of this Long Perng scope is this to Starfield and Ontario telescope but they ignored it.  So I chose not to buy it at this time. 

 

I gather it is the A model.

 

Your reasoning makes completely sense and I still might pull the trigger sometime on this one because I really like the concept.



#23 johninderby-uk

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Posted 02 February 2020 - 08:04 PM

I have one of the StellaMira 80mm f/10 ED arriving in a couple of days time. It is intended for visual use. They have 85mm and 104mm triplets better suited for AP. I bought it as a lunar / planetary scope as part of a grab’n’go setup. Should also be good for splitting doubles although that’s not my main interest.

 

One thing I really like about FLOs approach to their new line of scopes is that every single one will be tested and tuned up if needed by Es Reid who is one of the top optical people in the UK.

 

Quote

”He checks the telescope's optics are well figured and properly aligned. I.e. he checks for star-shape, colour, spherical aberrations and astigmatism. In short, he ensures the telescope is a good example and performs as it should. If he finds it is not then he will correct the alignment/aberration on the bench. If this is not possible the telescope is rejected.”

 

The StellaMira version is the hybrid R&P and the FPL53 & Lanthanum glass. Also comes with a carry handle as pictured on other scopes in the line. The photo on FLOs website will be updated to show the handle.

 

Now just need the weather to co-operate.

 

       John


Edited by johninderby-uk, 02 February 2020 - 08:38 PM.

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#24 Bennevis

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Posted 03 February 2020 - 04:27 AM

strange scope. At F/10 this is real slow one. Wonder why. My FPL53 102 mm does just fine, no color....

 

Looks very good though, but a bit of a long tube.

 

This is just it really. The Stella Mira 80mm F10 is more or less the same size as an Altair or Teleskop Service 102mm F7 FPL53 Doublet, with excellent colour correction, but it's 80mm so you lose a lot of light and resolution. 

 

Plus the price is very high compared to the very well thought of refractors from Skywatcher, Stellarvue, Altair Astro and so-on.

 

I don't really get it to be honest. If it was a 4" then that would be a contender which is the point at which the aperture justifies that tube size for what is essentially a lunar/planetary long focal length enthusiast scope.

 

So I'd choose a well corrected 102mm F7 ED anytime, because there just so much more you can see with 4".


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#25 Bennevis

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Posted 03 February 2020 - 04:35 AM

The only other difference I could see between the two versions of this scope on the Long Perng website is that the verbiage for the Crayford version specifically lists lanthanum whereas that for the R&P version does not. I imagine that this is maybe an inadvertent omission in the case of the latter.

 

I also assume the optics to be identical between the two. Why would Long Perng go for lesser optics on the model with the better focuser?

For this scope, From an optical design standpoint, I'm wondering what an LAK Lanthanum would add, if the dispersion of one element is already at FPL53 levels?

 

Why would one want to increase the dispersion of that mating element?

 

You could achieve very effective colour correction with FPL61 or another substitute with less expense at F10.

 

Also it's interesting to see claims of a dual ED triplet lens design on the other models like the Stellamira 104mm F6 (link here https://www.firstlig...-telescope.html )

 

I've never seen a triplet with an extra ED element before, and I wonder what that brings when it's possible to get apochromatic performance with a triplet lens with just one extra high dispersion element.

 

So we'd have two ED elements and one non-ED element.

 

I'd ask for a colour crossing diagram to check if there is benefit in the extra cost. 


Edited by Bennevis, 03 February 2020 - 05:02 AM.



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