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Equipment Discussions >> Refractors

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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Triplet APO or Doublet APO? new [Re: olivdeso]
      #5867378 - 05/17/13 03:33 PM

Quote:

Quote:


I am curious if you have spent much time observing Venus at higher magnifications? Certainly there are situations when Venus shows a significant amount of atmospheric dispersion but this is not a given, the maximum elongation of Venus is about 45 degrees so it's can be free from the effects of atmospheric effects.

Jon




Hi Jon,

Until now I never had a chance to see Venus free of atmospheric dispertion here in France.
Even last year when it was well positioned, the color dispersion was obvious with the TEC160ED for instance.

The paradox with high end large APO like the TEC160ED is that they show a very high contrast and excelent color correction that result also in high sensitivity to atmospheric dispersion.
Even on Mars, the dispersion is enoying as soon as Mars is more than 1h away from the meridian.

So I invested in an ADC at the end.

That said I will try again, following your advice, but I a not optimistic at all. The analysis will not be easy anyway...migh be it could be easier in a drier place...

Olivier




Olivier:

My experience suggests that the fact that the atmospheric dispersion is so apparent is a sign of the superior color correction of your scope. Were chromatic aberration of the objective an issue, you would not see the atmospheric dispersion.

Jon


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REC
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Reged: 10/20/10

Loc: NC
Re: Triplet APO or Doublet APO? new [Re: JoseBorrero]
      #5867399 - 05/17/13 03:39 PM

Wow, they are amazing images, thanks for the link!

Bob


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audioaficionado
professor emeritus


Reged: 05/24/12

Loc: Medford, Orygun, USA
Re: Triplet APO or Doublet APO? new [Re: SteveG]
      #5867459 - 05/17/13 03:55 PM

Quote:

Quote:

At it's brightest, Venus is about 2.3 magnitudes brighter than the moon at it's brightest, that's 8 times brighter than the moon at it's brightest. This is what makes Venus such a challenge for a refractor.


Jon




Perhaps I'm misunderstanding you here? Isn't the moon at about magnitude -13 always brighter than Venus at about magnitude -4?



The moon is gray. About the shade of asphalt pavement after it's aged a year or two. Venus is more white and a brighter surface even though the moon reflects much more light in total.


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JoeM101
scholastic sledgehammer


Reged: 04/09/12

Loc: 45.66086, -73.54702
Re: Triplet APO or Doublet APO? new [Re: CounterWeight]
      #5867574 - 05/17/13 04:19 PM

Quote:

What about a Hatori-Honso triplet?




Wow, wasn't aware he made scopes.. bet he made one for Bill though nice one Jim


I just got another opportunity to pick up a TMB130ss (triplet APO) at a great price but was looking at the SW120ProED (doublet APO).. 1400 cheaper.. wish i had 5k to blow right about now, would pick em both up and really give this forum a review...

hmm.. .anyone care to donate to the "Let's help get Joe the scopes so he can give us a review fund"... i accept Paypal

But in all seriousness, great images!

Edited by JoeM101 (05/17/13 04:20 PM)


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FaronD
sage


Reged: 03/25/10

Loc: Richmond Hill, Ontario
Re: Triplet APO or Doublet APO? new [Re: hfjacinto]
      #5867950 - 05/17/13 07:08 PM Attachment (10 downloads)

Quote:



My friend had a TAK 130 and an FSQ 106. The FSQ106 is color free, but the TAK 130 was as color free as was the 120MM. After looking through my 120, he sold the TAK 130 and brought a mount and a 9.25 as we all know aperture rules on DSO

I know some people are sensitive to CA but for some of us, its not that big deal and we don't see it.

I also have expeirenced the "I paid a lot for my NP101, AP, TEC, etc so of course its better than your 18" reflector".





Helder, you are saying that a Synta doublet ED120 and my TOA130 with "two" FPL53 elements have equal optics?
Also, you say that your friend took one look through your Eon 120 and immediately sold the TOA130 to purchase a 9.25 SCT and mount?? This doesn't make sense to me? Shouldn't he have purchased an EON120 or a Skywatcher ED120mm perhaps?

Your comment "I also have expeirenced the "I paid a lot for my NP101, AP, TEC, etc so of course its better than your 18" reflector".
Sorry but the TEC, AP, Taks are better than most Chinese 120mm doublets, not better than an 18" reflector of course, well, sometimes they are. Nothing really blows away the other anymore however, there is an improvement as you go up. Is it worth the extra thousands of dollars? Depends on who you ask. Do you truly believe it's only conspicuous consumption to purchase a top shelf refractor?
I'm not trying to be arrogant here, honestly, but an EON120 is not an Astro-Physics GT130, sorry. However, they are great scopes. Actually, I've viewed through the EON120, Skywatcher 80mm Equinox, and the Skywatcher ED120, Skywatcher 80ED, they are nice scopes.

Everyone try this for fun. Type "ST80 moon" in google then select images. Actually, I'll post a random shot here. We all know a ST80 is correct?
I used to love that little short tube 80mm and yes it has lots of ca.
My point is, don't judge optics by a photo alone, there are too many variables.

Faron


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hfjacinto
I think he's got it!
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Reged: 01/12/09

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Re: Triplet APO or Doublet APO? new [Re: FaronD]
      #5867966 - 05/17/13 07:23 PM

"Helder, you are saying that a Synta doublet ED120 and my TOA130 with "two" FPL53 elements have equal optics? "

The objects we looked at, the view was comparable between the 120 and the 130MM. He also looked through my 9.25 and that was the scope he ended up buying. I never said he wanted an EON, he looked through the 120MM, looked through the 9.25 and now owns a 9,25 and an FSQ for imaging but no longer owns a 130. Mechanically the TOA is a superb scope, I had the option of buying it and I could have, I had the cash on hand, but the difference wasn't enough for me to spend that much money. I ended up getting a Lunt Solar scope and I am pretty happy with that. This isn't to say that a TEC, TAK or AP are not nice scopes they are, I just don't see the reason to pay so much, I mean I can get a C14 which will show me more of deep space objects, I don't do double stars and I am happy with my imaging rig.

" Your comment "I also have experienced the "I paid a lot for my NP101, AP, TEC, etc so of course its better than your 18" reflector".
Sorry but the TEC, AP, Taks are better than most Chinese 120mm doublets, not better than an 18" reflector of course, well, sometimes they are."

Looking through an NP101, an AP178, Tec 140 and an 18" Dob at M42, there was no comparison, the 18" DOB showed more nebulosity and had a brighter image.

No comparison to a 120MM, the 18" DOB was so far ahead that I didn't even try to compare my scope. A few weeks ago, we looked through a C14 EDGE and that scope had one of the best views ever, better than anything else I've looked through. I was so impressed with the C14 EDGE that I would rather spend the money on that set-up.

But that's not the question, the question was can a doublet also be color free and I say yes it can. Or at least color free to me and many others.

Edited by hfjacinto (05/17/13 07:33 PM)


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FaronD
sage


Reged: 03/25/10

Loc: Richmond Hill, Ontario
Re: Triplet APO or Doublet APO? new [Re: hfjacinto]
      #5867986 - 05/17/13 07:34 PM

Quote:

"Helder, you are saying that a Synta doublet ED120 and my TOA130 with "two" FPL53 elements have equal optics? "

The objects we looked at, the view was comparable. I am not the one that owned the TOA130 and the owner no longer owns it, so I am assuming he somewhat agreed.

" Your comment "I also have experienced the "I paid a lot for my NP101, AP, TEC, etc so of course its better than your 18" reflector".
Sorry but the TEC, AP, Taks are better than most Chinese 120mm doublets, not better than an 18" reflector of course, well, sometimes they are."

Looking through an NP101, an AP178, Tec 140 and an 18" Dob at M42, there was no comparison, the 18" DOB showed more nebulosity and had a brighter image.

Actually a few weeks ago, we looked through a C14 EDGE and that scope had one of the best views ever, better than anything else I've looked through.

But that's not the question, the question was can a doublet also be color free and I say yes it can. Or at least color free to me and many others.




Helder, that is the question but it's not your only answer. You are also suggesting that it's as good as any top tier scope out there, correct?
Hopefully, I'm not sounding combative, I certainly don't mean to be. I'm just chiming in.

Faron


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hfjacinto
I think he's got it!
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Reged: 01/12/09

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Re: Triplet APO or Doublet APO? new [Re: FaronD]
      #5868016 - 05/17/13 07:46 PM

Faron,

I am in no way saying that the mass produced Chinese scopes are as good as the premium brands. They are clearly better on certain things, like for example Venus shows some color on my EON, but on the TAK it didn't show any. We split Sirius with both but on the TAK it was much easier.

Looking at M45, fainter stars appeared in the TAK, the focuser is WOW on the TAK. The heft and weight are nice and the scope is beautiful.

But thats when looking for items, so let me tell you a story, we once compared the 30MM ES 82* to the 31MM Nagler T5, I own the T5 and there were certain things that I could tell in the T5 (like a red star was really red in the Nagler but not in the ES and the extreme outer edge of the Nagler was better, no comatic stars), but I needed to look for these items, in the end, if I didn't own the T5, I doubt I would have spent the money to get it. I am not an intense observer, I like to look, spend a few minutes go to the next object. I don't need a $5000 scope to do that. The doublet I own is nice and has enough contrast to keep me happy and CA is very well controlled.


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timps
sage


Reged: 02/24/13

Re: Triplet APO or Doublet APO? new [Re: hfjacinto]
      #5868191 - 05/17/13 09:37 PM

I don't think the TOA130 has two FPL53 elements.

As far as I am aware it has one FPL53 element between two crown & flint elements.


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FaronD
sage


Reged: 03/25/10

Loc: Richmond Hill, Ontario
Re: Triplet APO or Doublet APO? new [Re: hfjacinto]
      #5868193 - 05/17/13 09:38 PM

Helder, to be honest, I'm exactly like you. I'm quite happy looking through any scope. I'm not bothered by CA either, I certainly will notice it when it's there, but I can look pass it.
I've been fortunate enough to be able to purchase a few nice toys. If that were to turn around, I would still be quite content with an EQ6 and my old Orion 80ED for imaging. Would I notice the difference, absolutely.

Faron


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FaronD
sage


Reged: 03/25/10

Loc: Richmond Hill, Ontario
Re: Triplet APO or Doublet APO? new [Re: timps]
      #5868287 - 05/17/13 10:15 PM

Timps, you could be right. I've read it both ways. I remember reading it here and a few other places http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3473595/Main...
That certainly doesn't make it fact. It might be a fpl53 between two ED elements. Whatever the configuration is, it's certainly one of the best corrected designs out there.

Faron


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JimP
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Reged: 04/22/03

Loc: South Carolina
Re: Triplet APO or Doublet APO? new [Re: FaronD]
      #5868346 - 05/17/13 10:43 PM Attachment (16 downloads)

To each his own. I just came up on the list to order an AP 130 GT. Would I rather buy an EON 120 and save money? No. I just ordered the AP 130. I have been observing since 1965. I would never question your decision if you would rather purchase the EON 120 and save the money. As I said, to each his own. Some have the money to buy high end scopes and some do not. Others have the money but choose not to spend it on high end telescopes. Fine with me. I own a quite fine 20" Dob but would never choose it if I could only keep one of my scopes.
The TAK FS series Fluorite doublets are excellent visual telescopes. I agree that the degree of CA seen in a doublet varies from individual to individual and the mind will compensate for the CA after a while and appear far less obtrusive than initially noted. That was certainly the case with an RE Brandt 8" F/13 doublet I once owned.
Buy what you can or want to spend the money for and use it. You will be happy as long as you use the scope. My opinion.


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FaronD
sage


Reged: 03/25/10

Loc: Richmond Hill, Ontario
Re: Triplet APO or Doublet APO? new [Re: JimP]
      #5868375 - 05/17/13 10:59 PM

Jim I don't want to purchase an Orion EON120, I want an AP130 like you

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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Triplet APO or Doublet APO? new [Re: hfjacinto]
      #5868558 - 05/18/13 12:31 AM

Quote:

The doublet I own is nice and has enough contrast to keep me happy and CA is very well controlled.






That seems like a very reasonable assessment of the 120mm F/7.5 Synta ED/APO scopes. Maybe not perfection but pretty darn good.

Thinking back, it's been nearly 10 years since the ED-80 arrived and transformed the refractor marketplace. At the time, many were skeptical that the ED-80 was the real thing but for many of us, it was our first taste of owning a very good quality refractor.. $500 for an 80mm FPL-53 apo sounds quite reasonable today, it's a sign times have changed.

Now you can buy a Sky Watcher 120mm Pro for about $1600 including rings, a 2 inch dielectric diagonal, two speed focuser, a case, a RACI finder.. That's a heck of a deal and a pretty good scope too.

Jon


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JoeM101
scholastic sledgehammer


Reged: 04/09/12

Loc: 45.66086, -73.54702
Re: Triplet APO or Doublet APO? new [Re: Jon Isaacs]
      #5869292 - 05/18/13 01:06 PM

there you have it...

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JoseBorrero
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Re: Triplet APO or Doublet APO? new [Re: JoeM101]
      #5869502 - 05/18/13 02:51 PM

here's a video with 10" TMB Apo and as you can see, still have
CA. Or I guess is the video camera. http://www.youtube.com/watch?v=5p_Wx-0HYNs


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JoseBorrero
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Re: Triplet APO or Doublet APO? new [Re: JoseBorrero]
      #5869593 - 05/18/13 03:36 PM

Don't get tricked if narrowband is on the question because a good achromatic might trick you! look here: http://www.astrobin.com/users/FrancescoTallarico/

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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Triplet APO or Doublet APO? [Re: JoeM101]
      #5869605 - 05/18/13 03:45 PM

Quote:

there you have it...




It's kind of a question whether you are satisfied with "pretty darn good" or not.

In general, I am OK with "pretty darn good" or even just "pretty good" and indeed, even "not half-bad" and "so-so" can be entirely satisfying.

But there is also no doubt that the difference between "pretty darn good" and something like the NP-101 is noticeable ... a thread like this one will hopefully allow one to get a feel for that difference.

Jon


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JimP
Pooh-Bah


Reged: 04/22/03

Loc: South Carolina
Re: Triplet APO or Doublet APO? [Re: JoseBorrero]
      #5869686 - 05/18/13 04:32 PM

That is my TMB 10" and that is NOT chromatic aberration! It is atmospheric dispersion. The images through my TOM 10" are absolutely color free.

Jim Phillips


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hfjacinto
I think he's got it!
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Reged: 01/12/09

Loc: Land of clouds and LP
Re: Triplet APO or Doublet APO? [Re: JimP]
      #5869762 - 05/18/13 05:20 PM

Again this is such a stupid argument, some people like triplets some like doublets. If you can't afford an AP, then a doublet is a really nice scope. Period end of conversation.

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