ED vs APO Refractor Telescopes!? FPL-51 vs FPL-53 vs FCD-100!?
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- Опубликовано: 3 дек 2024
- Are you getting confused by the different types of glass used in refractor telescopes that are available today? Well, I was too so I did some research. The biggest challenge when building refractor telescopes is to reduce or completely eliminate chromatic aberration which creates 'false' colors when observing or photographing the night sky. In order to do so, good quality refractors use extra low (ED; FPL-51/FK61) or super-low dispersion (SD; FPL-53/FPL-55?FCD-100) glass types. Low-dispersion glass is paired with two or more other glass elements to reduce or eliminate chromatic aberration. The number of glass elements, as well as the type of spacing used, and the build quality of a refractor telescope, ultimately determine whether the telescope is truly free of false color (apochromatic).
Read my somewhat more serious blog about this topic here:
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I just got a Skywatcher 120mm APO.
Watching this I’m imagining the amount of work you put into producing it. You are a patient man Wido. Nicely done.
Thanks, Bruce!
Cool, I've just bought FCD-100 and no regrets. Perfect correction
Super fun video. Just sold my Stellarvue sv70t to a good friend. Vic makes amazing scopes.
Great video...!!! Many doubts resolved... and with some sense of humor... Well done...!!!
I have a TS Photoline 115 triplet APO with FPL51/Lanthanum glass, it’s doing a pretty good job despite not having FPL53 glass.
It's an F/7 and a triplet, so you're probably fine. It will be free of chromatic aberration.
Also my experience @@AstroForumSpace
You really make this hobby fun! 😂😂
So i have a cgance to buy a Skywatcher ED80 pro F/5 super APO TRIPLET FPL 53 glass. It comes with case + other things too. I really want to start Astrophotography. The Price is £500 and its secondhand. Do you think would be a good scope to start me off with. He said its in Fantastic condition.
Regards Roy
That's an excellent scope, if in good condition, to start astrophotography Roy. I've created list of top refractor telescopes used by most astrophotographers, perhaps useful: astroforumspace.com/top-10-most-popular-refractor-telescopes-for-astrophotography-in-2023/ its bigger brother (the 100mm Esprit) is in the top 3.
@AstroForumSpace Thanks I do appreciate and value your reply. Thank you 👍
Friken hilarious Wido. I'm considering the red cat 51. Any thoughts
Thanks.
It's the most popular refractor telescope, and I'm sure it'll get you great pictures of the night sky. I did consider buying one myself, but the biggest drawback for me is the limited focal length. You'll be getting wider field images with a couple of degrees fov . If you already have longer focal length telescopes, it'll be a nice addition. If not, I think you'll want to buy a longer FL telescope pretty soon after using the redcat.
Interesting video. A 80 mm APO costs just as much as a Bresser 127/1200 f9.4 achromat (450€). But which one is better? I guess that because of the much bigger aperture the 127/1200 mm should be better. I don’t know which one to buy. I would really appreciate your opinion :). Unfortunately there are practically no comparison videos on RUclips between an achromat and APO at similar prices. Thank you!
It depends on the objects you want to capture. Achromats are ok when looking at the moon, but as soon as you're going to capture deepsky objects you'll see some nasty color fringing. If you're into deep sky, I'd strongly recommend good quality Optics, meaning extra low dispersion glass. If you're only observing and not imaging, achromats are fine.
@@AstroForumSpace Thank you for your answer. I am only interested in observing, not in astrophotography. Even if the achromat is an f9.4 or f10 the color aberrations are still intense ?
Missed hearing your voice, Wido! Saw the Carl Sagan Cosmos series while recouping from recent bad hangover.... I suspect i may have seen the series on TV a long time ago...maybe 32 years ago! But i have to say, when i saw the Huygens episode of Carl Sagan's Cosmos, i thought of you, wido!
Where does the FCD1 fall in the spectrum? I've got an ES ED102. Is that acceptable for astrophotography or will I just be frustrated with the results?
FCD1 is frustrating enough, that people change it to FCD100
It's comparable to FPL-51 in terms of Abbe number. Check: refractiveindex.info/?shelf=glass&book=HOYA-FCD&page=FCD1
das war wunderschön 😂👍
😆 lol
well done Wido
Lol, tx. Maybe a little over the top 😆
At first I thought you were going to show some some examples and practical comparative (some photos shoot with every glass tipe). I know a lot of people who would love to see a comparison like that because of the price difference. Thanks.
That's always a tricky comparison because mount, astronomical seeing, position of DSO and camera used all influence the images making these comparisons a mixed bag...
Nico Carver - Nebula Photos Channel - did a great video with actual test data "4 Telescopes Tested: Doublet vs. Triplet vs. Quadruplet vs Quintuplet" and his results showed that glass quality was more important than design. A WO doublet clearly beat a Sharpstar Triplet because it has better glass.
Hi Paul. Sounds interesting. I think both the design and the glass matter. If the design quality is equal, then the difference is going to be the glass type used. I would not put all your faith in "actual test data" outside the lab in real life, as there are a lot of factors that influence the outcome beyond the telescope (camera, astronomical seeing, position of DSO, tracking accuracy of the mount, etc.). Or to put it in simple terms: I've made terrible and great astronomy pictures using the same setup and pointing at the same DSO across different nights and even the same night depending on the weather conditions...but I'm sure Nico would recognize that and great that he goes through all the trouble showing us his results.
Actually WIdo, joking aside I have the Altair Starwave Triplet 115 APO with FK61 triplet lens. I cannot tell the difference when imaging from my Esprit 120 which had FPL53 glass but I had to sell it as it suffered from pinched optics at anything below 0 C So its not just the glass type but the design and you also forgot to mention that the focal ratio is important in colour correction, ie you can have great color correction at F7 with FPL51/FK61 glass that will outperform a doublet design with superior glass at F6 for example.
I did mention the design issue. Vic clearly mentioned build quality 👌, lol.
@@AstroForumSpace lol its the accent lol
I’ll stand by my little giant killer - TeleVue TV76🔭👍
Glastype heeft volgens Lichtenknecker (Designer van Evolux) geen waarde. Ik qoute hem "Refractoren worden ontworpen met de glazen die beschikbaar zijn, rekening houdend met de wensen van de moderne gebruiker (snelle openingsverhouding).
Er is een grote mythe die in stand gehouden wordt op het net, dat enkel FPL53 de beste kleurcorrectie biedt, waarbij ik zeg dat dit niet zo is, enkel de combinatie van verschillende glassoorten is relevant. Er zijn Takahashi topmodellen waar geen FPL53 in te vinden is (of z'n equivalent van Hoya enz). Het is dus een van de kunsten van het vak om die combinaties te vinden. Vandaar dat Skywatcher hierover niet communiceert.".
Dit heeft Lichtenknecker mij gezegd, omdat er van die andere fanboys die negatieve kritiek probeerden te weerleggen op de Evolux serie. En ik heb mijn scope laten testen. FPL51 met FCD1000.
Het is denk ik niet zo dat het geen waarde heeft, verschillende typen glas hebben verschillende spreidingswaarden. Maar inderdaad, de combinatie van glas en kwaliteit van de refractor hebben waarschijnlijk een grote impact op het resultaat. Stellarvue en Takahashi staan erom bekend dat ze hun telescopen handmatig produceren, wat vaak een hogere kwaliteit oplevert. Groeten!
This is hilarious!
You crack me up.
i like your German language ;-)
Hahaha!! Fun video 👏😆
Nice 😜🔭🌚👍🌕🌘🛸👽🪐🚀🌖🔭
I was ńot ready lol
Sorry Marco, 😆
😂😂😂😂😂❤❤❤❤❤😂😂😂😂😂
😎🤣
I think Wido's been on the "Special Cakes" 😜🤪🥮
🎂🍰
Love his humor