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A beautiful Italian evening. Zeiss AS150 F/15, vs Tecnosky 150 F/6, vs 150 F/8

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#26 francesco italy

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Posted 04 April 2019 - 04:21 PM

There was recently a raging debate about this concept in the ATM forum based on a conversation in this forum. Apparently, there is no relationship between long focal ratio and steadiness of seeing/depth of field. Contrary to mine and many other observers reports. 

 

 

 

 

Dear Tyson,

 

This Is very interesting, In Italy we are in the same boat:

 

 

It look like that some amateur astronomers in the "Bel Paese" often are looking forward to dismantle the ability of long focus refractors to detect more details In bad seeing conditions, they are seeking "proofs" and "scientific evidence" to endorse their theory. Actually there are so many experienced observers that say the opposite and a lot of observing reports attesting the fact that Long focus refractors are de facto capable of better performances during worst seeing conditions.

 

 

http://www.massimili...HRO-vs-APOs.pdf

 

 

 

A while ago I did a comparison between an 80mm f/20 or so optic to an 80mm f/6 optic, specifically looking for behavior differences during less than best seeing.  I saw exactly what you explain.  So like you, the underlying details blurred some but overall remained more defined in the longer focal length scope.

 

It's a pleasure sharing all this things with you guys, a real pleasure applause.gif


Edited by francesco italy, 04 April 2019 - 04:37 PM.

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#27 vahe

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Posted 04 April 2019 - 04:30 PM

 I felt it was actually amazing how much depth of focus there was in the f/20 instrument as I could move the fine focus knob quite a bit and the image just stayed locked in focus and sharp.  As I continued my testing, I felt that these depth-of-focus advantages start coming into play at around f/13-15, and being very noticeable at f/20 and more.  

In any instrument there is only one exact focus point regardless to F ratio, if an instrument is used for imaging using CCD detectors one needs to fine focus to get a sharp image, there is no give and take when it comes to CCD detectors, depth of focus will not carry the day.

.

When doing visual the very long focus instruments with considerable depth of focus offer an advantage since our eyes are able to adjust ever so slightly to minor out of focus images, that kind of flexibility is built-in in our visual system.

.

Vahe


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#28 BillP

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Posted 04 April 2019 - 05:22 PM

There was recently a raging debate about this concept in the ATM forum based on a conversation in this forum. Apparently, there is no relationship between long focal ratio and steadiness of seeing/depth of field.

 

I am unaware of that "raging debate".  From my standpoint though, as I did my own specific testing over a stretch of time, that "debate" would be moot for me as I have my personal experience which of course will take precedence.  However, I would agree with what you said above...as this is what I saw.  Steadiness of the image was not impacted.  What was different however was the degree of damage to the view.  If the local seeing cause the image to jitter and de-focus 5 times in 5 seconds, as example, in the short focal ratio scope, then it also jittered and de-focused the same rate in the long focal ratio scope.  Where the difference was was in the impact to the image.  So the jittering/defocus of the image was much less severe in the longer focal ratio scope.  It was quite easy to  see when over a stretch of several minutes the seeing was tumultuous how the impact would always be much milder in the long focal ratio instrument.

 

Mind though that these "advantages" in my testing did not really become evident until one got close to f/15 and they did not become blatantly obvious until I reach f/20.  So there are specific bounds/conditions for this to become apparent.  Most folks talk about f/10 and such as "long" and having these mystical advantages.  Well, the advantages are not mystical and they do not happen until one gets significantly longer in focal ratio.  But they are there and was easy to see.  Others can debate all they want.  I decided to go a step further and see for myself empirically, which trumps any debate.  And like I do all the time when I run my personal experiments, I controlled the situation as much as possible and was careful to mitigate as many confounding variables as possible in the process, and never base my conclusions on a single experience but on multiple runs of the experiment to ensure repeatability.  I am satisfied that there is no debate that the behavior is indeed there.  As for the exact cause, I can only posit that may be due to depth-of-focus since I could rack the focuser so much further with the long focal ratio f/20 scope and have the image stay sharp - was quite astounding.  However, I am a visual observer and care little really about driving optical reasons.  More important for me is knowing what behavior will happen when I am using an instrument.  The wherefore and whys are less important for me so I don't get hung up on it if people want to argue the root cause as that is also irrelevant for me.  All I really care about in my observing life is that I know myself, the sky, and my equipment well enough that I can get repeatable results all the time when I choose certain tools, approaches, targets, and conditions.  And of course adding to that cadre based on experience and not debate as time progresses.  Others can believe what they choose based on whatever theory/science they want.  I will believe behaviors that I see and can reliably replicate.  The behavior is there and very real for suitably long focal ratios when a human eye is at the eyepiece (i.e., for the entire "system" as component attributes are again subject to relentless debate by the many whose cup is always full).  End of story. smile.gif

 

And again...excellent report and observation Piergiovanni waytogo.gif waytogo.gif  bow.gif


Edited by BillP, 05 April 2019 - 01:24 PM.

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#29 Tyson M

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Posted 04 April 2019 - 06:59 PM

Dear Tyson,

 

This Is very interesting, In Italy we are in the same boat:

 

 

It look like that some amateur astronomers in the "Bel Paese" often are looking forward to dismantle the ability of long focus refractors to detect more details In bad seeing conditions, they are seeking "proofs" and "scientific evidence" to endorse their theory. Actually there are so many experienced observers that say the opposite and a lot of observing reports attesting the fact that Long focus refractors are de facto capable of better performances during worst seeing conditions.

 

 

http://www.massimili...HRO-vs-APOs.pdf

 

 

 

 

It's a pleasure sharing all this things with you guys, a real pleasure applause.gif

I tried to run that through Microsoft word to translate but it didn't work.  Too bad, that looks like a thorough and good read. frown.gif

 

and BillP, I meant not disrespect. I value your opinion and methodology on these matters.  I too believe my eyes, and believe effects like that can be seen an even lower lower focal length/ratio than you describe in your specific tests, possibly because of observer's age and visual acuity(I am 33).  I will just keep observing and letting my eyes sort out what I like and don't like. 

 

Regardless of the exact reasons, the net positive effect is clearly observed by many besides me, you or franscesco.

 

Regards, and thanks for the report franscesco


Edited by Tyson M, 04 April 2019 - 07:08 PM.

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#30 donadani

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Posted 04 April 2019 - 11:55 PM

10 points to Italy! ;)

 

Great report guys - thanks! Love theses AS lenses too while I just know the little sisters of that 6" lens - but they give some of the sweetest airydiscs I know! especially those with the longer f-ratios… 

 

When seeing your pics I would have loved to join in with my Astro-Optik-Manufaktur 160 f/10 oh that would be too great :) 

 

Could you give us some more details of the tube the AS-150 is in - e.g. is it baffled? how heavy is it? and how Long?

 

clear sky!

Christoph



#31 francesco italy

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Posted 05 April 2019 - 12:31 AM

I tried to run that through Microsoft word to translate but it didn't work.  Too bad, that looks like a thorough and good read. frown.gif

 

 

 

Regards, and thanks for the report franscesco

 

Max Is going to translate It waytogo.gif

 

In the meantime please try here

 

https://www.cloudyni...st-light/page-2


Edited by francesco italy, 05 April 2019 - 01:02 AM.


#32 Binomania.it

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Posted 05 April 2019 - 01:17 AM

Hi guys. I am very, very happy to have started this discussion. Here in Italy, Federico, Francesco and me... feel a little lonely. There is little interest in long-focus refractors. Many tend to diminish their merits, accusing its to be bulky, useless, preferring large mirrors or  refractor open to F/5 or F/6. We are "nostalgic visualists" and we especially love watching the moon and the planets.

Many young amateur astronomers are l interested in sharing astronomical photographs and are not interested in learning  how to observe the planets.

 

Over the years we have often compared various optical configurations but long-range refractors are in our heart.

 

Yesterday i've received from an italian distributor (Tecnosky) a specimen of BARRIDE 150 mm F/15 with a crafted optical tube. I hope to organize another comparison with AS 150 and D&G 150 owned by Federico.

Obviously we will accompany the evening with still red wine and a tasty plate of "lasagne."After all... we are Italianslol.gif lol.gif

During the week-end i will  publish some images.


Edited by Binomania.it, 05 April 2019 - 01:18 AM.

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#33 Binomania.it

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Posted 05 April 2019 - 01:57 AM

 

We spent one night observing Jupiter and the Moon with the "San Giorgio Morais" 190 f 15 CdE refractor 

The last time I observed in the San Giorgio Morais 190 F 15, I used my Docter 12.5mm UWA eyepiece to observe the moon. The telescope was in the garden of an abbey, there was a bit of haze, crows in flight, the quiet  buzz of the participants and the tolling of the bells. The 84° Docter AFOVs gave me a very clear and contrasted panoramic view of our satellite, with dozens of shades of albedo and perceived details. It was a poetic observation, sometimes gothic. Guys, I love that telescope!!! I send you the link of a gallery https://www.binomani...morais-gallery/

 

sangiorgio_morais_opera_18.jpg


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#34 re vega

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Posted 05 April 2019 - 02:20 AM

Could you give us some more details of the tube the AS-150 is in - e.g. is it baffled? how heavy is it? and how Long?

 

 

clear sky!

Christoph

 

https://www.binomani...=4312&mode=view
https://www.binomani...=4311&mode=view
https://www.binomani...=4310&mode=view
https://www.binomani...=4309&mode=view
https://www.binomani...=4308&mode=view
https://www.binomani...=4307&mode=view


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#35 GShaffer

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Posted 05 April 2019 - 05:08 AM

Hi guys. I am very, very happy to have started this discussion. Here in Italy, Federico, Francesco and me... feel a little lonely. There is little interest in long-focus refractors. Many tend to diminish their merits, accusing its to be bulky, useless, preferring large mirrors or  refractor open to F/5 or F/6. We are "nostalgic visualists" and we especially love watching the moon and the planets.

Many young amateur astronomers are l interested in sharing astronomical photographs and are not interested in learning  how to observe the planets.

 

Over the years we have often compared various optical configurations but long-range refractors are in our heart.

 

Yesterday i've received from an italian distributor (Tecnosky) a specimen of BARRIDE 150 mm F/15 with a crafted optical tube. I hope to organize another comparison with AS 150 and D&G 150 owned by Federico.

Obviously we will accompany the evening with still red wine and a tasty plate of "lasagne."After all... we are Italianslol.gif lol.gif

During the week-end i will  publish some images.

 

Enjoyed your topic and rest assured there are plenty of us who like the long refractors. I built my 8" f/16 using a lens I ran across made by a highly respected optician named Verne Muffoletto 35+ years ago. Its been setup next to an 8" f/12 Zeiss and everyone who had the opportunity to view with them said there wasnt a nickels difference in the quality of the view including the owner of the Zeiss. It is by far my favorite scope and I have a fairly large collection.

 

build86small.jpg


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#36 Binomania.it

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Posted 05 April 2019 - 05:13 AM

Enjoyed your topic and rest assured there are plenty of us who like the long refractors. I built my 8" f/16 using a lens I ran across made by a highly respected optician named Verne Muffoletto 35+ years ago. Its been setup next to an 8" f/12 Zeiss and everyone who had the opportunity to view with them said there wasnt a nickels difference in the view including the owner of the Zeiss. It is by far my favorite scope and I have a fairly large collection.

 

attachicon.gif build86small.jpg

Wow.Wonderful realization, compliments!. Here in Italy, occasionally,  we organize the "NLT" (Night of Long Refractors) I dare not imagine how many participants there would be if you organized it in the USA..



#37 CHASLX200

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Posted 05 April 2019 - 05:36 AM

Looks like you need a bigger boat for that OTA.  



#38 Daniel Mounsey

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Posted 05 April 2019 - 06:36 AM

Hi guys. I am very, very happy to have started this discussion. Here in Italy, Federico, Francesco and me... feel a little lonely. There is little interest in long-focus refractors. Many tend to diminish their merits, accusing its to be bulky, useless, preferring large mirrors or  refractor open to F/5 or F/6. We are "nostalgic visualists" and we especially love watching the moon and the planets.

Many young amateur astronomers are l interested in sharing astronomical photographs and are not interested in learning  how to observe the planets.

 

Over the years we have often compared various optical configurations but long-range refractors are in our heart.

 

Yesterday i've received from an italian distributor (Tecnosky) a specimen of BARRIDE 150 mm F/15 with a crafted optical tube. I hope to organize another comparison with AS 150 and D&G 150 owned by Federico.

Obviously we will accompany the evening with still red wine and a tasty plate of "lasagne."After all... we are Italianslol.gif lol.gif

During the week-end i will  publish some images.

You’re not alone. Many of us here love achromats and we encourage you to share your experiences here with us. They are always welcome. I currently own several achromats and have built a few myself. My good observing buddy Luigi is from Italy and I forwarded your post to him. What you guys are doing that admire very much is you are getting out and enjoying yourselves. We have a few fun comparisons just around the corner coming soon. We’ve just been holding off due to unusual weather and planet season is just around the corner. waytogo.gif


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#39 francesco italy

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Posted 05 April 2019 - 07:38 AM


 

You’re not alone. Many of us here love achromats and we encourage you to share your experiences here with us. They are always welcome.

 

 

Uuuh yeah dear Daniel, we'll take you up on that.

 

121.jpg

 

 

D&G 5" f31 custom made lens by ( The legendary ) Barry


Edited by francesco italy, 05 April 2019 - 07:46 AM.

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#40 re vega

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Posted 05 April 2019 - 08:08 AM

What a comet catcher!!



#41 Daniel Mounsey

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Posted 05 April 2019 - 08:18 AM

 

 

 

Uuuh yeah dear Daniel, we'll take you up on that.

 

attachicon.gif 121.jpg

 

 

D&G 5" f31 custom made lens by ( The legendary ) Barry

lol.gif  now that’s an achromat!



#42 francesco italy

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Posted 05 April 2019 - 08:20 AM

yessss It Isgrin.gif


Edited by francesco italy, 05 April 2019 - 08:26 AM.


#43 memento

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Posted 05 April 2019 - 12:15 PM

Yay! So this is how a 5" looks like that has the exact same level of color correction of my small 60mm f/15 :D



#44 donadani

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Posted 06 April 2019 - 12:09 AM

...not f/15 but about the max. length possible to handle around for a quick session on the balcony: AOM 160 f/10 - glas used FPL-51 & N-ZK7 that colorwise brings it close to a LZOS 152 f/8 with 8mm more aperture power and the benefits of the slower f-ratio. 

 

 

 

Would really like to see it next an AS-150... :)


Edited by donadani, 06 April 2019 - 12:36 AM.

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#45 francesco italy

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Posted 06 April 2019 - 12:45 AM

...not f/15 but about the max. length possible to handle around for a quick session on the balcony: AOM 160 f/10 - glas used FPL-51 & N-ZK7 that colorwise brings it close to a LZOS 152 f/8 with 8mm more aperture power and the benefits of the slower f-ratio. 

 

attachicon.gif 0b.jpg

 

 

Would really like to see it next an AS-150... smile.gif

 

Wow !! A long focus....Apo ?

 

May you please let us know something more about It?  In Italy we haven't heard from AOM



#46 donadani

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Posted 06 April 2019 - 01:18 AM

sure! you find many Infos on their HP:  https://www.astro-th...tik-manufaktur/  (maybe google translator is your friend…) - the 130/9 and 160/10 doublets were made in small numbers with a visual observer in mind - all optics are calculated by Dr. Pudenz and handmade by Peter Große... and use the same combination of glas where the big benefit is N-ZK7 and maybe not FPL51 (but who cares…) I guess as you have lots of experience in apos these names are not unknown for you.

 

 

 

 

Their latest release is a 4" APQ successor that is not too bad too wink.gif

 

 

 

clear sky

Christoph


Edited by donadani, 06 April 2019 - 01:19 AM.

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#47 francesco italy

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Posted 06 April 2019 - 02:21 AM

Dear Christoph thank you very much !!

 

If I am not mistaken Dr. Jürgen Pudenz worked for Zeiss at the APQ projectjawdrop.gif

 

*this* Is great, a long focus apochromat refractor, what a trasgressive decision by AOM, applause.gif nowadays the marketing Is pushing towards astro photography and clearly towards very fast scopes..

 

Congratulations on the choice Chris, beautiful refractor !waytogo.gif It would be nice to try your gem and the Zeiss AS the same night side by side.


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#48 donadani

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Posted 06 April 2019 - 02:39 AM

he, he - I´m sitting near Munich - maybe someday we should arrange a visual refractor meeting in the alps half the way to Italy AS150, AOM160 and some other nice apos under a alpine sky - that would be terrific!  :) :) :)


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#49 vahe

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Posted 06 April 2019 - 09:09 AM

Hi from Italy, and..as usual..excuse me for my poor english.blush.gif 
I state that these are  only initial and instinctive impressions. I will write an article on Binomania, in the collaboration with Francesco Toni and Federico Caro, my dear adventure friends.
Some weeks ago, in fact, we spent a wonderful evening with the telescopes mentioned in the object:
• Zeiss AS 150mm F / 15 (optical tube by Francesco Fumagalli)
 

Since you guys appreciate and are well into long focus quality refractors I have a question, are there any Zeiss AS 200/3000 refractors in the hands of Italian amateurs that you know of, and, if you know of any would you by any chance have a link on one of these big AS refractors?

.

Vahe 



#50 re vega

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Posted 06 April 2019 - 10:45 AM

Hi Christoph, by seeing your pictures, what stands out is a killer coating...the lens seems not to be there 


Edited by re vega, 06 April 2019 - 10:49 AM.

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