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Yuri at TEC recent comment regarding APO vs. Mak

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#51 azure1961p

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Posted 20 November 2013 - 01:21 AM

I would say then, that salt-on-black-paper stars in a reflector is reality, and stars getting all 'vibrant' and 'pulsing with energy', you have bigger issues than optical quality ;)

Honestly, how do you qualify 'pulsing with energy' and 'vibrant'?


Stars are sources of energy. They are vibrant. They shine, they are not dots. That's reality. I see this more clearly in refractors. They look brighter and colors of stars look deeper. If you think they are dots, you have your own issues you need to deal with ;) .


The only energy pulsing a diffraction pattern is poor seeing. The best seeing flatlines it into a stationary (or near) pattern.

Pete

#52 mark8888

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Posted 20 November 2013 - 03:36 AM

The only energy pulsing a diffraction pattern is poor seeing. The best seeing flatlines it into a stationary (or near) pattern.
Pete


Whatever. I said, "The double cluster, to me, in a refractor, is pulsing with energy. It's vibrant." OK, I hereby modify it to "pulsing with energy, and emitting energy when the best seeing flatlines it into a stationary (or near) pattern".

I don't always have "the best seeing" at my location. I was talking about my experience, not yours. It goes to the point that "in my experience" and "at my location" and "to me" should be added to these comments, rather than telling other people what they see (even if they've been seeing the same thing for 50 years) and calling it untrue when it disagrees with our own experience.

#53 Muffin Research

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Posted 20 November 2013 - 03:47 AM

I don't think the pulsating vibrant should be taken literally?? I mean it's a way to describe an aesthetic not actually seeing a pulsing vibrant cluster.

There is a difference looking at a photograph versus looking at it real life, just as there is a difference looking at something for real or looking at it via the reflection of a mirror.
Most refractor viewers suffer one mirror reflection (very high polish flat surface), with a newton it's two reflections, with a SCT you're up to three reflection + 1 refraction. It's easy to assume that some charm is being lost somewhere along that path and this charm is just as hard to put into words as when you are talking about warm & mojo in audio, it's there but how to grasp it or define it.

#54 mark8888

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Posted 20 November 2013 - 03:52 AM

I don't think the pulsating vibrant should be taken literally?? I mean it's a way to describe an aesthetic not actually seeing a pulsing vibrant cluster.


+10 that's exactly how I meant it. Something active and vibrant in the view as opposed to a bit clinical, flat. More variation in how the stars look in a refractor... shining and very rich colors as opposed to inactive and kind of uniform. To me. I certainly wouldn't presume to tell someone else that they are wrong if they see it differently.

#55 Sasa

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Posted 20 November 2013 - 05:27 AM

Yes, I would be glad to. Since the Veil was mentioned by someone else I will use that as an example. In my C11 only the eastern section is visible without using a filter at my moderately light polluted backyard site. In the 175EDF both sections are visible without any filtration. In addition to being more visible, I am able to see structure in the Veil with the 175. With the C11, the Veil is bright but not as tenuous as in the 175.

I can name other examples, this spring I was able to detect fainter galaxies in the 175 that could not be coaxed out of the C11. And galaxies that were visible in both had more detail in the 175. One that comes to mind is NGC 4565. In the C11 it is a silver streak against the sky. In the 175 it was the same silver streak but I could detect a "fattening" in the middle.

I understand that this is fantasy according to another poster but it's a fantasy that occurs in my backyard on a regular basis. Maybe my backyard is the Nexus of the Universe and the laws of physics don't apply here.

The C11 is f/10 and 2800mm, the 175 is f/8 and 1400mm. I have a nice selection of eyepieces and can match exit pupils pretty close and magnifications even closer.

Couple of points here. The C11 can out resolve the 175 on doubles by a substantial margin. Fainter stars are visible in the C11. For point sources, the C11 beats the 175. It (the C11) also shows a tremendous amount of detail on Jupiter, however I have stayed away from making any comments regarding planetary performance between the two because I haven't done that kind of comparison yet. Lunar performance is close enough between the two that I would almost call it a draw.

My experience is that on DSOs from a moderately light polluted area, my C11 cannot compete with a 7 inch APO. I attribute that difference to the APO's contrast that Yuri mentioned in his comments.


Hi Mark,

I have similar experience from my light polluted backyard. I had very good 250mm f/6.4 Newton, and I bought Sky Watcher ED100 to complement it. Somehow I'm still using the refractor, while the large Dobson is gone. In general, 10" dobson was showing fainter objects - but not that much as would a difference in aperture suggest (10"should reach 2 magnitudes deeper than 4"). I can reach stars fainter than magnitude 14 with ED100, while with Newton, I was able to go only down to 14.7 from my backyard (and 14.9 in darker side).

I think there were 2 reasons. One has to do with the fact, that I could not observe effectively with Newton at high powers (I mean 300x and more) and simultaneously guard my eyes from side-light. This is probably not your case as your SCT was mounted on driven mount.

The second reason is the different ways how the side-light is treated by various designs. While refractors could be baffled almost perfectly, this was not the case of my Newton. Even though it had solid tube, fully flocked, I could still see some effects of side-light when looking into the eyepiece. The weak point was the focuser, but I sold the telescope before I forced myself to experiment with baffling the focuser tube. As a result, I glimpsed in ED100 few objects that I could not find in 250mm - these were typically large DSO's with low surface brightness (for example NGC5053 comes to my mind). And opposite, there were objects that I saw in 10" Newton but not in ED100.

I have never owned SCT or large Mak and I never studied how these desigens handle side-light. But may be, this could be an answer to your observation.

Cheers,
Alexander

#56 azure1961p

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Posted 20 November 2013 - 09:01 AM


The only energy pulsing a diffraction pattern is poor seeing. The best seeing flatlines it into a stationary (or near) pattern.
Pete


Whatever. I said, "The double cluster, to me, in a refractor, is pulsing with energy. It's vibrant." OK, I hereby modify it to "pulsing with energy, and emitting energy when the best seeing flatlines it into a stationary (or near) pattern".

.


Sounds like your scope runs on batteries.

;)

Pete

#57 Cotts

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Posted 20 November 2013 - 09:15 AM

Bang for the buck is a factor that needs to be kept in mind. Consider:

My 8" f/15.5 TEC MakCass = $4k + $6k for a mount = $10k

What APO refractor and mount combination could I buy for $10k that will equal the contrast, resolution and light grasp of the above system? How about none. Zero. Nada.

This is a much overlooked consideration.

Dave

#58 mark8888

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Posted 20 November 2013 - 09:32 AM


Sounds like your scope runs on batteries.

;)

Pete


:lol: no... not the scope, but the stars.

#59 FirstSight

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Posted 20 November 2013 - 09:34 AM

Bang for the buck is a factor that needs to be kept in mind. Consider:

My 8" f/15.5 TEC MakCass = $4k + $6k for a mount = $10k

What APO refractor and mount combination could I buy for $10k that will equal the contrast, resolution and light grasp of the above system? How about none. Zero. Nada.

This is a much overlooked consideration.

Dave


What this "overlooked consideration" overlooks is yet another overlooked consideration...(ain't recursion wonderful?) :grin:

Refractors excel in "best bang for the aperture". The views in my four-inch NP-101 at f/5.4 simply cannot be beat for the contrast, sharpness, and detail available in four inches. If, OTOH, we're talking "best bang for the buck", that 10k should go toward a big Dob with premium mirrors (and as many extra features e.g. DSCs) that can be had for the price. You also have the consideration that the Mak in question is f/15, and while some folks like the optical benefits of the forgivingly wide zone of focus and minimization of aberrations this gives, for others of us the narrow TFOV is a deal-killer; give us the wide open spaces of f/5.

#60 t.r.

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Posted 20 November 2013 - 09:34 AM

Bang for the buck is a factor that needs to be kept in mind. Consider:

My 8" f/15.5 TEC MakCass = $4k + $6k for a mount = $10k

What APO refractor and mount combination could I buy for $10k that will equal the contrast, resolution and light grasp of the above system? How about none. Zero. Nada.

This is a much overlooked consideration.

Dave


Until you enter a Questar into the equation! :p
Take the base model 3.5" @ $4250 for instance...a 4" apo or even an ED is gonna give it a run for its money! :grin:
I know what you meant though Dave and Value means something to me too...and most of us I presume. ;)

#61 crow

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Posted 20 November 2013 - 09:45 AM

Surely if you're operating out of a light polluted environment contrast will be effected. All that diffuse light spilling down the C11. Most skies in light polluted areas I've been seem washed out to the naked eye, the apo will naturally do better in such conditions. You are talking about an AP175, right? Any moisture in the air in combination with the light pollution?

Combine that with the idea that maybe you haven't got a great C11....?

My Edge 1100 has great contrast and goes very deep, nice stellar image. It cost me 3.1 grand. If seeing is bad I take my 4 inch apo. Ill take the 16 grand price difference and buy a new car.

#62 ken svp120

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Posted 20 November 2013 - 09:51 AM

Ed, just wanted to take a second to say thanks for your detailed posts. Its nice to see concepts explained clearly even when it takes some effort (length of post, explanation of ideas) in order to do so. Much appreciated. As to books, I've been trying for years to wean myself off of that garbage - I've found it helpful to watch a lot of TV, play video games, and drink in quantity. Give it a shot and PM if you need some friendly support! :lol:

#63 mgwhittle

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Posted 20 November 2013 - 10:01 AM

I'll do you an even better example using me. Instead of spending $20,000 on a Astro Physics 175mm APO, I could have bought a Takahashi TOA150 AND a 20 inch Teeter Telescopes dob for the same amount of money. Two premium high performance optics including 6 inch APO. I will admit that my thought process did not follow best performance for dollar spent. While my wallet might not appreciate it, my eyes have been ecstatic with my decision.

However, the purpose I had when I stated this thread was to discuss how a smaller APO could be outperformed by an larger obstructed system, particularly on DSOs which are often cited as being effected most by aperture. Yuri's recent comment had me thinking about this again and my personal experience which is why I posted my comments.

But you are right, if we put money into the equation it really changes the playing field.

#64 vahe

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Posted 20 November 2013 - 10:11 AM

He stated that up till 2001 they were focused on Maks until the WSP that year. He said they had a 200mm Mak set up next to a Astro Physics 155mm APO and although the Mak was "optically perfect" as he put it, it was easily beat by the APO on contrast.



Did you by any chance read my response to Yuri’s comment in that thread?

Here is the problem with Yuri’s conclusions, he has produced three different 200mm Maks, F/11 with 30% co, F/15.5 with 26% co. and a super planetary F/20 with 22% co.
On that night he had his F/15.5 and compared it to AP 155 F/7, why did he compared the F/15.5 and not the F/20 which is optimized for planets?

As I stated in my reply to Yuri, I compared my AP 155 F/9 with refigured optics to 200/20 TEC Mak viewing Jupiter and the Mak wins hands down including contrast, no iffs and no butts.

Before we close the book on this issue it does help to compare the apo to a Mak that is optimized for planets, are my expectations out of line?

With all due respect Yuri’s conclusions did not tell me much, or shall I say understandable considering the model used for that shootout.

Vahe

#65 t.r.

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Posted 20 November 2013 - 10:22 AM

Before we close the book on this issue it does help to compare the apo to a Mak that is optimized for planets, are my expectations out of line


There are VERY few maks/scts optimized for planets...they are in the hands of just a lucky few. The more common 30% CO is what the majority are stuck comparing to.

#66 Asbytec

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Posted 20 November 2013 - 10:23 AM

If the best scope we own is the one we use, my MCT is a huge bang for few bucks. All issues, such as obstruction, scatter, multiple surfaces, and anything else one can come up with, either anectdotal, documented, or theoretical, that scope gets used a lot. Its been a pleasure peeking through the narrow FOV, batteling cooling and susceptability to seeing trying to spot the Pup and sketching the planets. Its clean and well corrected and is pleasing when it resolves BU1030.

Few scopes I've owned rekindle a love to fight off mosquitoes, wait out the clouds, and to inspire a prayer of thanks when Jove burns into the retina. Thats exactly why it gets used. So, point being there is nothing wrong with a good MCT in my experience. It does what I want it to do nicely. Nothing wrong with a good refractor either, but to read this thread it seems I should never have gotten a MCT, strong mount included, on closeout sale. I feel the same about a good MCT as others feel about their favorite design.

Sometimes I crave a good 4" refractor, but I suspect I pretty much have one, save for the pinpoint stars and wide field. As for DSO contrast, first light with M42 was amazing. MCTs are indeed refractor-like in that many owners love them, too.

#67 PeterR280

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Posted 20 November 2013 - 10:24 AM

When CO drops to around 20% contrast improves but you need the high focal ratios.

#68 crow

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Posted 20 November 2013 - 10:30 AM

I don't doubt what you are seeing. However I've used my C11 only once under light polluted skies and it wasn't quite as good, I just put it down to all the diffuse light, they are by definition light buckets and they'll take it all in whatever quality it comes, cross referenced with the info Eddgie provides, is it really that much of a surprise?

However you've got a cracking telescope there, no doubt. Apo's in the AP/TEC league are pretty cool.

#69 mgwhittle

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Posted 20 November 2013 - 10:45 AM

He stated that up till 2001 they were focused on Maks until the WSP that year. He said they had a 200mm Mak set up next to a Astro Physics 155mm APO and although the Mak was "optically perfect" as he put it, it was easily beat by the APO on contrast.



Did you by any chance read my response to Yuri’s comment in that thread?

Here is the problem with Yuri’s conclusions, he has produced three different 200mm Maks, F/11 with 30% co, F/15.5 with 26% co. and a super planetary F/20 with 22% co.
On that night he had his F/15.5 and compared it to AP 155 F/7, why did he compared the F/15.5 and not the F/20 which is optimized for planets?

As I stated in my reply to Yuri, I compared my AP 155 F/9 with refigured optics to 200/20 TEC Mak viewing Jupiter and the Mak wins hands down including contrast, no iffs and no butts.

Before we close the book on this issue it does help to compare the apo to a Mak that is optimized for planets, are my expectations out of line?

With all due respect Yuri’s conclusions did not tell me much, or shall I say understandable considering the model used for that shootout.

Vahe


Yes, I read it but doesn't that give more evidence to my conclusion regarding contrast? You had to go to a specialized planetary design (f/20) in order to create the contrast necessary to outperform a smaller APO with a faster f ratio. That is what I took from your comments, if I have missed your point I apologize.

I agree that specialized designs will outperform more moderate designs, in the areas the specialized designs are made to a higher performance, regardless of the type of design we are talking about.

Which reminds me to mention, again, that I am not talking about planetary performance. What I am experiencing, and trying to understand why, is being able to see fainter DSOs and more detail in those DSOs in my 7 inch APO verus my 11 inch SCT under moderate light polluted skies.

#70 mgwhittle

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Posted 20 November 2013 - 10:59 AM

Surely if you're operating out of a light polluted environment contrast will be effected. All that diffuse light spilling down the C11. Most skies in light polluted areas I've been seem washed out to the naked eye, the apo will naturally do better in such conditions. You are talking about an AP175, right? Any moisture in the air in combination with the light pollution?

Combine that with the idea that maybe you haven't got a great C11....?

My Edge 1100 has great contrast and goes very deep, nice stellar image. It cost me 3.1 grand. If seeing is bad I take my 4 inch apo. Ill take the 16 grand price difference and buy a new car.


When you say stellar image I assume you mean stars. My C11 sees fainter stars than the 175 so no issue there. Globulars in the C11 are also significantly more resolved with more stars visible. What I am experiencing has to do with extended objects.

Others in this thread have questioned whether my C11 is any good. It was purchased last year so it is a new sample. I regularly exceed 50x per inch when splitting close doubles. Jupiter is a wealth of details. The GRS is textured and has different hues of red and brown inside it. To me those two performance observations alone lead me to believe that I have a good C11. It is a valid point to inquire about but let's put that one to rest.

#71 Astrojensen

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Posted 20 November 2013 - 11:07 AM

What I am experiencing, and trying to understand why, is being able to see fainter DSOs and more detail in those DSOs in my 7 inch APO verus my 11 inch SCT under moderate light polluted skies.


I would like more details, before I dare to come with any explanations, though I do have some clear ideas of what's going on. First, does this happen on all diffuse deep-sky objects? Only large ones or only small ones? What magnifications were used on both telescopes during the comparison? Seeing conditions? Details, details, details.


Clear skies!
Thomas, Denmark

#72 crow

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Posted 20 November 2013 - 11:13 AM

Yeah, sorry, stars, discussions around these parts tend to extend your decorative grammar. :)

Since its extended objects then I think that strengthens the case against light pollution, diffuse objects competing with that. Seems like common sense to me. I have to say that I operate under dark skies, maybe in a different environment the C11 wouldn't be my first choice of scope. I've no axe to grind, I'm near the top of the wait list for a Tec 140.

#73 Paul Morow

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Posted 20 November 2013 - 11:47 AM

This is a very good discussion!

Rob Moore, author of the Nikon 20x120 III Binocular review (2003) here on Cloudy Nights, also at one time owned a fine specimen of a Takahashi FS152 along with a C11 in the mid to late 1990s. I personally viewed through Rob’s FS152 at a couple star parties and it was indeed a sweet refractor. I considered Rob a true connoisseur of fine optics and he had an experienced eye for planetary observing. Rob told me that his C11 was capable of outperforming the 6” refractor only about once or twice a year due to the seeing conditions. When the seeing was at its best (a rare event for the Midwest I’m afraid) the C11 would show some absolutely stunning details on Jupiter, but on a typical night the 6” refractor was the optical instrument of choice for the planets. I also remember Rob mentioning that these wonderful C11 images tended to happen after Midnight due to cooling issues of the OTA.

I own an old C8 from 1990 that has pretty sweet optics when the conditions are favorable. Many years ago when I had it out at an astronomy club outing some fellow observers actually asked why I purchase the AP 155EDT refractor when I already owned such a fine C8. The C8 rarely performs at its peak and the refractor cuts through the typical poor seeing of the Midwest like a laser. One night a few years ago the seeing was so bad that my C8 was practically useless for planetary observing at only 100 power. My 155EDT the same night was delivering good planetary images at about 150 power. If I didn’t own the refractor I would have gotten a lot more sleep over the years.

#74 Cotts

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Posted 20 November 2013 - 11:57 AM


Until you enter a Questar into the equation!
Take the base model 3.5" @ $4250 for instance...a 4" apo or even an ED is gonna give it a run for its money!


Do you really mean to say a 3.5" or a 4" telescope (no matter how perfect it is) will give a very high quality 8" telescope a "run for its money"?

Shirley, you can't be Sirius....

Dave

#75 Cotts

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Posted 20 November 2013 - 12:11 PM

........aaaaaand here are the reasons why this debate, while instructive, will continue to appear in various guises until the heat-death of the universe.

Because all of the concepts below affect our views at the eyepiece:

Aperture
Central Obstruction
Design - Newt - MakCass - MakNewt - SCT - Refractor
Quality of the optic - smoothness and figure -strehl - CA
Quality of the coatings - smoothness - reflectivity - transmission
Seeing at your location
Cooldown of optics and tube currents
Experience of the observer
Eye-lens quality - astig, floaters, yellowing of lens, cataracts etc.



Any attempt to talk definitively about only two or three or even four of these concepts leaves out too many important factors and leads us to say, mostly, "It depends...."

But I still enjoy the give-and-take of these discussions.....

Dave






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