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4" Apochromatic Hyper Shootout

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#201 Refractor6

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Posted 14 March 2007 - 10:53 AM

Hello stargazers,

o.k., I answer my question myself:

Deepsky has some very differing objects. Big dim nebulae, but bright small
objects too. A globular cluster can be observed with high magnification,
it is bright enough and the power is needed to resolve many stars,
and there the colour aberration (allthough not visible as colour!)
of a short achromat will hinder it to show the same contrast than
an equally big apochromat.

Reagards,Karsten


Go to a supremely dark site say in the high alpine 6000-7000ft with excellent seeing and do a comparison and see for yourself what the difference if any is on deepsky targets between a perfectly collimated well figured short tube achro and a similar aperture apo at various magnifications and report back the results. Under these conditions a well figured short tube achro can show some pretty amazing detail on deepsky targets when then transparency and seeing are excellent as the quality of the dark skies with not a hint of light pollution.

I'm sure you will notice subtle differences on said targets under similar conditions but it won't be as dramatic as some may think on deepsky objects.

Anyone wanting the answer to this long debated achro/apo question should go out to such a location and view several various deepsky targets at a wide range of magnifications and see for themselves first hand the comparison.


------------------

Stan

Takahashi FS-102 NSV
Antares 152 f/8 prototype
Antares 152 f/6.5
Antares 127 f/6.45 prototype
Orion 9x63 mini giants
Pentax 20x60 PCF WP
 

#202 jrbarnett

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Posted 14 March 2007 - 11:33 AM

Thanks Mike. I totally agree on the common courtesy aspect. I also understand how a vendor/commercial tie-in could be different than an unaffiliated individual submitting such posts.

Also I believe CN has the most active set of forums dedicated to amateur astronomy on the net, so it is the most logical place to publish reviews if widespread attention is of value to the author.

Thanks for the candid response.

All the best,

Jim
 

#203 Tom T

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Posted 14 March 2007 - 11:50 AM



I also think there's some confusion with your statements concerning your emphasis on your seeing. I'm sure you have good seeing, but these are 4" scopes.



What's that supposed to mean? That there are not all that much differences between 4" scopes?


No, as Alan pointed out, simply that 4" scopes are rarely seeing limited, but often aperture limited.

and you're an 80mm fan, in fact I email you when I have questions about them because I rarely use or test refractors that small.


Actually, I'm a "telescope" fan. I like em all. :grin:

It's one thing to rack up experience on different nights with one or two telescopes at a time but it's a different story when you're racking up several scopes at one time?


Huh?

Not exactly sure where you got that. What IS important is to spend lots of time with all the telescopes. IMO, One night is not sufficient.

That's not at all the impression you gave in the apo vs. achro forum. When I stated that a well made achro could have just as much potential on deep sky as an apo, your answer was that you dissagreed with me. The guy was just a beginner.


I guess it depends on what you call potential.

Does a refractor with better correction go deeper?

Yes. It depends on where the specific correction is, but under sufficiently detailed examination this is quite clear - when you're talking about similar focal lengths.

Is it minor?

Yeah, pretty much.

Is the best corrected refractor always the best choice?

No.

What I was trying to do is help beginners understand that every time something says "ED" on it, it doesn't mean they should go jumping for joy.


Well, yes, that's a given.
 

#204 Joad

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Posted 14 March 2007 - 11:53 AM

As Astronomics has said, there aren't any TOS violations in this thread, quite. If there were, the thread would have been moderated. But there are a number of large elephants hanging out in this thread who want to be noticed.

The first elephant has his trunk in the title of the thread, which promises a remarkably sweeping test of what are arguably among the most popular of apochromatic refractors. This alone is going to get a lot of interest, because these are expensive instruments that many people already own, or are thinking of purchasing, and product reviews of this sort, like movie reviews, can have a real influence on consumers. What is more, hobbyists tend to be rather sensitive about any negative things said about their gear. So, in short, a lot of people here are interested in the outcome of these tests.

Which brings in elephant number two. This elephant is sitting on the question of what prompted this large scale test in the first place. Is there a commercial sponsor behind it? If so, will this in any way affect the results? Or are the tests designed to prove a point about achromatic vs. apochromatic performance? If so, will this in any way affect the results?

Then there is the elephant who is standing on the question, "where will this review appear, and when?" Of course it can't appear anywhere until the tests are completed and the results written up, but this brings another elephant into the herd, trumpeting the question, "why announce a series of tests until the tests are completed and the results are ready to release?"

In short, while elephants are not against the TOS, they do take up a lot of room.

:elephdance: :elephdance: :elephdance: :elephdance:
 

#205 Scott Beith

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Posted 14 March 2007 - 11:57 AM

11 pages of room.
 

#206 Tom T

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Posted 14 March 2007 - 12:01 PM

It's for the trunks.
 

#207 Jeff Hudson

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Posted 14 March 2007 - 12:04 PM

Remember the Peter Sellers movie "The Party" where at one point an elephant was brought in? Sparking that memory brought a tear of joy to my eye....
 

#208 rnabholz

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Posted 14 March 2007 - 12:16 PM

I have read with wonder the 200 plus responses to this thread so far, up to and including the Moderator and Site Owner's comments.

So far, Dan has had his methods, sample size, sample list, techniques, experience, motives and who knows what else all called into question before he has even posted his first finding.

A couple of thoughts:

1. Dan Mounsey is a great resource on this site as the owners of the site have recognized with his Star Contributor Award. I think that Dan has established his credibility here.

2. Maybe everyone could take a breath and let the results come in before commenting on all the different aspects of the test.

3. I very much appreciate the service to the community that Cloudy Nights provides. I have always thought that building traffic was the whole idea of sites like this. So I was surprised at the comments from the Mod and owners about all the traffic this was generating without guarantee that it would be posted here. I don't know where it will be posted, but I do believe that if it is posted elsewhere, most of us will return here to discuss it because this is where we come for that kind of discourse. There is certainly enough evidence for that as is witnessed everyday in the forum discussion topics that cite an off site link or reference.

4. Finally, Dan, I hope you are ready to quit your job and devote yourself full time to answer all of the fallout from your results. I am sure you will call them as you see them, but you can be sure that someone's ox will be gored, and you will be called to account for everything from your visual accuity (please provide current optomitrist's report) to your pretest meal.

God help ya ;)
 

#209 spaceydee

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Posted 14 March 2007 - 12:32 PM

Actually, I'd like to ask that we not start the achro vs apo debate here. The thread is clearly about a 4" APO shootout, granted with varying types of glass and design.
 

#210 Scott Beith

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Posted 14 March 2007 - 12:35 PM

I appreciate anyone and everyone who takes the time to give their impressions of scope performance (especially refractors). I am looking forward to reading this report (and I don't care where my scope ends up on the pile) ;)

Hopefully Daniel found a SV to test. :)
 

#211 jrcrilly

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Posted 14 March 2007 - 12:36 PM

11 pages of room.


Yup.

It's possible that the tests will be completed and the promised report written.

It's also possible that the vendor who sponsored the tests will permit the writer to submit them to CN (a competitor's site) for publication.

At that point, it's possible that the report would be accepted for publication here.

I'd like to suggest that there has already been sufficient promotion of this project until one or more of the above steps is achieved. Until then, this is a very long thread about not very much. Let's sit back and wait.
 

#212 jonnyastro

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Posted 14 March 2007 - 12:42 PM

I just hope that Joad doesn"t have to perform his "Lock It" song again! :lol:
 

#213 Steph

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Posted 14 March 2007 - 01:03 PM

Oh Jonny, he'll be devastated if he thinks you didn't like the Lock It song... :(
 

#214 jonnyastro

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Posted 14 March 2007 - 01:05 PM

Oh Jonny, he'll be devastated if he thinks you didn't like the Lock It song... :(


I actually did like it!! :roflmao:
 

#215 Downward Bound

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Posted 14 March 2007 - 01:33 PM

I completely agree with Rod's comments above and appreciate Daniel's time and willingness to conduct this review. I've dealt with him numerous times and will attest to his honesty. While I have purchased scopes and accessories through him and his employer he has also recommended products that were competitive to their lines because he felt they were either better quality or a better value. I seriously doubt he would bring a commercial bias to the test - I've experienced just the contrary.

Let's all keep our egos and loyalties in check and try to patiently wait for the results. And while I love CN, its Mods (you know who you are :flower:) and volunteers, if the management is really concerned about the bandwidth of this thread then there are dozens of larger elephants to hunt first (Last Word First, Word Association.....and my silly haunt, the MSHSP).

Let's kick back, relax and enjoy the review when it hits. Try not to be too surprised when Daniel announces that he actually prefers his new Mewlon to all of these 4"ers. :lol:
 

#216 Scott Beith

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Posted 14 March 2007 - 01:34 PM

Or a nice 8" newt knowing Daniel. :lol:
 

#217 jrbarnett

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Posted 14 March 2007 - 01:41 PM

I had always assumed that at least two types of elephants potentially would be evident in such a review - white ones and pink ones. :lol:

White Elephant: http://en.wikipedia..../White_elephant

Pink Elephant: http://en.wikipedia....i/Pink_elephant

Regards,

Jim
 

#218 KaStern

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Posted 14 March 2007 - 03:54 PM

Hi,

Go to a supremely dark site say in the high alpine 6000-7000ft with excellent seeing ...



what has a high alpine site got to with excellent seeing :question:
In addition:
What has a high alpine site got to with colour aberration in an achromat :question:
O.k., if you are high enough there might not be enough oxygen and that
might affect your vision.

... and do a comparison and see for yourself what the difference if any is on deepsky targets between a perfectly collimated well figured short tube achro and a similar aperture apo ...



I did that several times during very good seeing in a flat region.
Differences were very different depending on the type of target and
the magnification. Globular clusters with high magnification are the
worst case for the achro, dim nebulae with low mags did not show a
difference at all to me.

.. a perfectly collimated well figured short tube achro ...



is the best short tube achro you can get, but it is not better than
the theoretical optical calculation of such a scope.
The calculation displays the contrast disadvantage to an equally sized apo.

Under these conditions a well figured short tube achro can show some pretty amazing detail on deepsky targets when then transparency and seeing are excellent as the quality of the dark skies with not a hint of light pollution.



No doubt. Better than an apo in the backyard of a steel mill...

Anyone wanting the answer to this long debated achro/apo question should go out to such a location and view several various deepsky targets at a wide range of magnifications and see for themselves first hand the comparison.



Agreed. And what did you find when comparing both 6" achro and 6" apo
(same f/ration, or nearly the same) at that location?

O.k. Off topic here, and I will stop here.

I do not understand this thread at all. Why does Joad think that
commercial interests will affect the comparison?
It might, but is that something new in this board :question:

And why is the comparison announced before it is done :question:
Does not make sense to me.

And why does Daniel Mounsey insist that there is no subjective component
in a comparison, when there are subjects doing this comparison?!
There never is something like complete objectivity, even if one
tries to acchieve it.

On the other hand this does not say that he and his companions will not
do their best to come near to an objective comparison.
I have no doubt that Daniel is experienced enough to be aware of these problems.

I counted 26 (twenty-six) post from the CN-"officials" until now
and a statement that there was no violation of the tos until now.

So there might be a major problem I overlooked, due to language barriers.

Maybe I can read RESULTS starting with post number 456 or so :lol:

(did I mention that we got clear skies here? Scope is waiting in the backyard)

Regards, Karsten
 

#219 J_D_Metzger

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Posted 14 March 2007 - 04:03 PM

And why is the comparison announced before it is done :question:
Does not make sense to me.


Karsten, you have hit the proverbial nail on the head...
 

#220 spaceydee

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Posted 14 March 2007 - 04:33 PM

Okay everyone --- Dee the moderator here --

The subject of achromats is really not relevant to a 4" APO shootout. Let's stay on topic!

thanks!
 

#221 Refractor6

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Posted 14 March 2007 - 04:36 PM

Hi,

Go to a supremely dark site say in the high alpine 6000-7000ft with excellent seeing ...



what has a high alpine site got to with excellent seeing :question:
In addition:
What has a high alpine site got to with colour aberration in an achromat :question:
O.k., if you are high enough there might not be enough oxygen and that
might affect your vision.

... and do a comparison and see for yourself what the difference if any is on deepsky targets between a perfectly collimated well figured short tube achro and a similar aperture apo ...



I did that several times during very good seeing in a flat region.
Differences were very different depending on the type of target and
the magnification. Globular clusters with high magnification are the
worst case for the achro, dim nebulae with low mags did not show a
difference at all to me.

.. a perfectly collimated well figured short tube achro ...



is the best short tube achro you can get, but it is not better than
the theoretical optical calculation of such a scope.
The calculation displays the contrast disadvantage to an equally sized apo.

Under these conditions a well figured short tube achro can show some pretty amazing detail on deepsky targets when then transparency and seeing are excellent as the quality of the dark skies with not a hint of light pollution.



No doubt. Better than an apo in the backyard of a steel mill...

Anyone wanting the answer to this long debated achro/apo question should go out to such a location and view several various deepsky targets at a wide range of magnifications and see for themselves first hand the comparison.



Agreed. And what did you find when comparing both 6" achro and 6" apo
(same f/ration, or nearly the same) at that location?

O.k. Off topic here, and I will stop here.

I do not understand this thread at all. Why does Joad think that
commercial interests will affect the comparison?
I might, but is that something new in this board :question:

And why is the comparison announced before it is done :question:
Does not make sense to me.

And why does Daniel Mounsey insist that there is no subjective component
in a comparison, when there are subjects doing this comparison?!
There never is something like complete objectivity, even if one
tries to acchieve it.

On the other hand this does not say that he and his companions will not
do their best to come near to an objective comparison.
I have no doubt that Daniel is experienced enough to be aware of these problems.

I counted 26 (twenty-six) post from the CN-"officials" until now
and a statement that there was no violation of the tos until now.

So there might be a major problem I overlooked, due to language barriers.

Maybe I can read RESULTS starting with post number 456 or so :lol:

(did I mention that we got clear skies here? Scope is waiting in the backyard)

Regards, Karsten



High alpine/no light pollution = excellent seeing and transparency with very dark skies. A major Canadian observatory was considered for the site we use in late Spring and Summer if your interested in knowing Karsten.

Conduct the comparison yourself and post your results. Many seasoned observers over here have for several years in a row at said location. Under these conditions a well figured achromat combined with great seeing can perform very well on deepsky targets including globular clusters at high power with a very good level of image sharpness and contrast. Been there done that. Yes there is a edge to an apo under these conditions but not by much of a margin on DSO targets at least not enough for me to be unhappy to unload my whole bank account on a similar aperture apo in the 6" class of instrument in particular based on what i've seen in my achros so far over many years at this location.

My observations and comparisons and i'm sticking with them and not changing my opinion anytime soon.


-------------------

Stan

Takahashi FS-102 NSV
Antares 152 f/8 prototype
Antares 152 f/6.5
Antares 127 f/6.45 prototype
Orion 9x63 mini giants
Pentax 20x60 PCF WP
 

#222 KaStern

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Posted 14 March 2007 - 05:16 PM

Hello Stan,

High alpine/no light pollution = excellent seeing and transparency with very dark skies.



the absense of light pollution and good transparency is no guarantee for
good seeing (= stable atmosphere).

A major Canadian observatory was considered for the site we use in late Spring and Summer ...



that is more a hint that the site will have good seeing too.

Under these conditions a well figured achromat combined with great seeing can perform very well on deepsky targets including globular clusters at high power with a very good level of image sharpness and contrast.



I never looked through a 6" short achromat wich could keep up to a 6" apo
at globular clusters in terms of contrast and resolution. That was here
in Europe, not in Canada...
The apo allways showed more resolved stars, especially in the center
of the globular. Stars peaked out more clearly. A globular is a very
difficult object for a scope. Faint resolved stars stand in front of
a background of unresolved stars. Light wich is spread into the surrounding
of the airy disc of a star add to the backkground.
Star is fainter, background brighter. This is classical contrast lessening.

Edit:

Yes there is a edge to an apo under these conditions but not by much of a margin on DSO targets at least not enough for me to be unhappy to unload my whole bank account on a similar aperture apo in the 6" class of instrument in particular based on what i've seen in my achros so far over many years at this location.


Ähm, I was referring to something Daniel wrote. I thought I should mention
that "deep sky" is not only dim nebulae but globulars too.
Things are very different there. The two sides of deep sky objects.
That is all I wanted to point out.

No need to be unhappy or go to the bank (I can not afford a 6" apo,
lucky, I don`t need one), but to be fair and admit that there are some
deep sky objects where an apo will be better than an achro.

Regards, Karsten
 

#223 spaceydee

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Posted 14 March 2007 - 05:20 PM

okay folks. I'm locking the thread for now pending review.

This thread is not the place for discussion of the merits and demerits of achros.
 

#224 spaceydee

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Posted 15 March 2007 - 02:01 PM

Okay everyone. I have unlocked this thread.

Let's keep this thread "on track". I gave several warnings here that this thread is clearly not an apo vs achro thread.

Please let's keep this thread on topic. Also, please remember to keep all posts respectful of other CN members.

Thanks!
 

#225 jonnyastro

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Posted 15 March 2007 - 02:11 PM

Round 2!!!! :foreheadslap:
 


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