Fpl51 vs fpl53

[quimby44]

Hi I was wondering is there a significant difference between fpl51 and fpl53 i am thinking about getting a rvo horizon 60ed many thanks Stephen 

[Clarkey]

I'm not an expert in glass, but I think in a doublet you would certainly see the benefit of FPL53 over 51. At F6 you will still probably get a small amount of CA, but it should be minimal. I cannot comment of this specific scope as I have no experience. However, for a small wide field scope, it should be OK. I assume this would be for imaging?

[quimby44]

20 hours ago, Clarkey said:

I'm not an expert in glass, but I think in a doublet you would certainly see the benefit of FPL53 over 51. At F6 you will still probably get a small amount of CA, but it should be minimal. I cannot comment of this specific scope as I have no experience. However, for a small wide field scope, it should be OK. I assume this would be for imaging?

 

[quimby44]

Yes just starting out can get a scoope and guide scope on a deal from rvo 

[StevieDvd]

The specs on the RVO say "The tube features superior FPL-53 specifically chosen by us to give the sharpest and most widefield images possible. "

[vlaiv]

23 hours ago, quimby44 said:

Hi I was wondering is there a significant difference between fpl51 and fpl53 i am thinking about getting a rvo horizon 60ed many thanks Stephen 

It is hard to tell.

Both FPL-51 and FPL-53 have potential to behave in a certain way - but will they, depends on what is the mating element and how well the glass is figured.

If we assume that both are reasonably well executed, then there are two parameters that we need to consider - one is F/ratio of the scope and other is aperture.

For slow enough scopes - there won't be significant difference.

For small enough aperture - there won't be significant difference.

I know that there is difference between the two at 4" F/7.

I think there might be difference at 80mm F/7

At 60mm F/6 I simply don't know if there will be significant difference. Even if there is some difference - use of special UV/IR cut filter like Astronomik L3 (which is advised for fast doublet anyway) - should even the playing field.

[ollypenrice]

Of all the things that will affect the quality of your results, the glass type will appear nowhere near the top of the list.* You would do better to look into focuser quality, standard of collimation and risk of cold weather pinching. Don't fret about the name of the glass: have a look, here and elsewhere, at what a certain telescope produces in terms of images. Pay more attention to broadband because that is a far harsher test of optics than narrowband.

I'm not saying glass type is irrelevant. I'm just saying that it is not the primary determinant of image quality.

Olly

*Edit: I mean it won't make the top ten. And it really won't.

Edited January 30, 2023 by ollypenrice

[gorann]

As said many other things are important, but I had two triplet Explore Scientific refractors (80 and 127 mm) with the cheaper FPL51 glass (or rather equivalent Hoya) and they did produce blue halos around bright stars, which is not a problem with the Esprits (FPL53) I now have. A clear difference but it costs a bit more.

[Adam J]

On 29/01/2023 at 18:44, quimby44 said:

Hi I was wondering is there a significant difference between fpl51 and fpl53 i am thinking about getting a rvo horizon 60ed many thanks Stephen

 

Just recomended that in a different thread:

In short yes you are better off with FPL53 and sometimes by a significant margin. If you want to know what an average FPL51 equiverlent looks like at F6.5 then look at the Evolux 62 and the discussion in this thread.

The long winded version is that the ED glass type is not everything and there are some excerlent FLP51 scopes out and about (though mostly triplets), but in the end on balance you are better off with premium glass or people would not be paying for it.

But all this discussion about the importance of glass type in this instance is unimportant, the important thing is that you are thinking about the RVO Horizon 60ED and that it is a great choice in my opinion and a proven good performer across the verious copies from RVO or WO or TS or Altair Astro I have seen very very few complaints so go press the buy now button and dont overthink it.

Dont underestimate the importance of that Zygo interferometre report either, as that kind of in house testing by RVO is going to mean that any really duff copies are going to be weeded out. I done belieive the other clones of the scope are offering that.

Adam

Edited January 31, 2023 by Adam J

[alacant]

On 29/01/2023 at 19:44, quimby44 said:

difference between fpl51 and fpl53

Hi

We find that by far the biggest influence upon image quality is the seeing, followed by the quality of your guiding, then... etc.

I guess you'd need exceptional conditions and a top of the range mount to be able to differentiate between types of glass. But hey, I'd love to see a side by side and be proved wrong.

Cheers 

Edited February 1, 2023 by alacant

[Elp]

If you've ever used a variety of dslr lenses to image in ap, quality of glass and the optical makeup makes all the difference.

[gorann]

3 hours ago, Elp said:

If you've ever used a variety of dslr lenses to image in ap, quality of glass and the optical makeup makes all the difference.

Yes, I do not think we should underestimate the quality of glass. If within the range of the wallet I think it is a good advice to also aim at a scope that will not soon be a disappointment, but could be a keeper for a long time. My suggestion would be something like an Esprit 80 or similar.

[Elp]

I came from an acro to my fpl53 synthetic fluorite z61, difference was clear. Even when planetary viewing although the targets are small they're very sharp with no colour fringing, that is what the glass does. Even at f3.9 there's little to no issue when imaging.

[quimby44]

On 30/01/2023 at 18:33, StevieDvd said:

The specs on the RVO say "The tube features superior FPL-53 specifically chosen by us to give the sharpest and most widefield images possible. "

 

[quimby44]

Thank you 

[JonHigh]

I have been looking into buying a new refractor. A 102 at f7 with FPL53 or the 115 at f7 with FPL51. I will be using it for imaging  with my astro camera  although I’m still unsure which one to get but leaning towards the 115 due to FL. Hopefully my HEQ5 Pro can take the payload so any suggestions would be welcome. Imaging Galaxies and nebula  

Together with the reducer and possible use of filters (mainly light pollution or narrow band) would the advantage of FPL53 glass be a bit negated once light hits the sensor? 

Edited June 15, 2023 by JonHigh

[vlaiv]

2 minutes ago, JonHigh said:

I have been looking into buying a new refractor. A 102 at f7 with FPL53 or the 115 at f7 with FPL51. I will be using it for imaging  with my astro camera  although I’m still unsure which one to get but leaning towards the 115 due to FL. Hopefully my HEQ5 Pro can take the payload so any suggestions would welcome. Imaging Galaxies and nebula  

Together with the reducer and possible use of filters (mainly light pollution or narrow band) would the advantage of FPL53 glass be a bit negated once light hits the sensor? 

115 F/7 with FPL51 is triplet lens and will perform better than doublet FPL-53 glass because of that.

I'd personally choose 115mm over 102mm for both visual and imaging. Only drawback is somewhat slower cool down due to amount of glass involved.

[JonHigh]

Hi Vlaiv. 
I absolutely agree with you however the 102 is a triplet as well, That’s why I’m in a predicament over them. 🤪

[vlaiv]

3 minutes ago, JonHigh said:

Hi Vlaiv. 
I absolutely agree with you however the 102 is a triplet as well, That’s why I’m in a predicament over them. 🤪

Oh I see. I was under the impression that 102 in question was a doublet.

In that case - choose based on other criteria. I think that both scopes will have level of correction that you need for astrophotography, so that won't be an issue.

[JonHigh]

Thanks, so it really comes down to focal length then? Other than that, they seem identical scopes. In that case I will probably go for the 115 due to what I want to image. 👍🏻

[vlaiv]

1 minute ago, JonHigh said:

Thanks, so it really comes down to focal length then? Other than that, they seem identical scopes. In that case I will probably go for the 115 due to what I want to image. 👍🏻

That would be my choice. I can't really say why, it's just something about that scope that is appealing to me.

[JonHigh]

All that said the quality of other glass between the scope and the sensor must play a part? You can have an awesome lens but the light still has to travel through the reducer. So I hope it is made of equally good quality too! Lol

[Clarkey]

FWIW I have the 115mm triplet with FPL-51 and use it for imaging. Personally, I have found the colour correction to be very good and I am glad I did not pay the extra 50% price hike for the FPL-53 version. This was taken with the scope. (There is a small bit of tilt giving the slight red / blue tinge to some of the stars). It is also a very good visual scope.

[GalaxyGael]

Also agree on the 115 FPL 51 triplet.

I had the tecnosky version. Only issue I found was slightly spikey/pinched stars in the +2 --3 C temperature range that was easily fixed with 1.8th turn of the centering screws, but color correction was excellent. In my skies, using a big m68 0.79x reducer, gave 632 nm fl at f/5.5, which is a good field of view with APS-C, decent resolution that I cannot beat in my skies with 3.76 um pixels. Would happily use 4.5 and 6um pixel sensors with that scope. And it is not as heavy as the length (with all imaging kit and dew shield extended) looks, easily to mount up each night. And, it is really good value for money at ~1300-1400 EUR, probably an excellent visual scope too as it is that much more than 100, with similar 800 mm focal lengths, but not unwieldy as much as a 130 mm for instance.

[Elp]

My Z61 is a doublet, doesn't have a colour fringing issue, not one that I've noticed. I've used an acro so know what it looks like. I've done visual and AP with it for planetary, lunar, solar and DSO.

To add to the mix, TS also offer FPL55.

Edited June 15, 2023 by Elp