jmiele
Patron Saint?
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Re: Using refractors for Deep Space Observing
[Re: Napersky]
#5264619 - 06/10/12 11:54 AM
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A better quality with less abberations Refractor will outperform a much more abberated larger aperature Reflector.
Perhaps, however you can't just assume the larger reflector isn't of high quality. My Mewlon 300 beats the TEC 180 hands down.... Quality refractor, quality reflector. Visualy, if the Mewlon is cooled properly and the seeing permits, you can push the magnification endlessly. That's a 2011 TEC 180FL and a 2012 Mewlon CRS, down stairs next to each other.
This is of course my subjective opinion, however owning both I'm not more vested in one or the other. Similar costs as well. The assessments were made on the same nights with the same EP's on doubles and planetary observations.
All that said however, the TEC will perform at a higher level more often than the Mewlon as the Mewlon is IME, more affected by seeing. I will add that to date - my best planetary views ever were with my 16" Dob.. That includes trumping the Mewlon 300.
Best, Joe
Edited by jmiele (06/10/12 03:49 PM)
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Astrojensen
Post Laureate
Reged: 10/05/08
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Re: Using refractors for Deep Space Observing
[Re: hfjacinto]
#5264721 - 06/10/12 01:15 PM
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And I while repeat this again, for DSOs aperture rules.
And I will repeat again: It depends.
Let's take M33, for example. It takes quite a wide field TFOV to frame it nicely in the eyepiece. At the same time, you may want a the magnification to be in the middle range, around 2-3mm exit pupil, to make the sky black and nice, depending on your observing site. At the 2010 MAF star party, I had the opportunity to observe M33 with both a 30" f/5 dob and a TEC 140.
In the 31N5 on the 30", M33 filled the field from edge to edge. The arms were evident, but the view was quite a bit more bland that I would have suspected. The TEC 140 had a 13mm Ethos in the focuser. At 75x, it had a field of view over twice as large as the 30" and framed the galaxy perfectly. The 1.87mm exit pupil made the sky background jet black. The galaxy was fainter, of course, but the image was much more contrasty and the view of the arms has forever been etched into my mind. It was fantastically beautiful. In absolutely no way could I say the view in the 30" was better. Oh, it was bigger, it was brighter, but... It was just lacking something the image in the TEC 140 had in spades. It looked flat and dull, while the TEC had immense depth and "reality" to it, for lack of a better word.
I can hear all of you already: "Ah, but you've got to match exit pupils, use higher power on the big scope, yada yada". Yes, I know. Yes, the 30" showed much detail in the arms at higher powers, but in no way did it ever show M33 as beautiful as the TEC 140. That is the one view I remember perfectly vividly from that night. All I remember of M33 in the 30" is that I was somewhat underwhelmed. It was my first time with such a huge scope and I honestly expected a lot more.
Oh sure, the images are brighter, but brightness is not everything. For a visual observer, aesthetics can be a very important thing. That night, the TEC 140 certainly delivered a very aesthetic image of M33 - and many other, large objects as well. My own 150mm achromat does the same on many nights, where the C8 fails.
Aperture can rule - and often does - but so can a smaller, high-quality telescope. It all depends on what we want. Aperture does not always rule, nor does a small high-end scope.
*Puts soap box back in corner*
Clear skies!
Thomas, Denmark
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Refractor6
Post Laureate
Reged: 10/20/04
Loc: Vancouver B.C. , Canada
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Re: Using refractors for Deep Space Observing
[Re: jmiele]
#5264734 - 06/10/12 01:24 PM
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I know this has been touched on but it's worth mentioning again.......
One thing I learned many years ago was the advantage that the refractor has over scopes of other designs on deep sky is the ability to achieve low power WIDE FIELDS of view. This with excellent contrast for the visual observer even under light polluted skies I discovered early on. Combine this with sharp, pinpoint image quality across the whole field of view and you have a winning combo. Take this same winning combo to a truly dark site and you'll truly really "see" more.
This advantage really comes into play if you want to view objects that are best framed with a larger true FOV and brought further out at the ep when combined with the use of a OIII filter and such in the mix. Well the larger scope of another design can see MORE for sure on DSO's but with its longer focal length in most cases in truth it will only see LESS compared to a shorter f/ratio refractor in the 6"+ class of instrument combined with high quality 2" low power eps on the same set of targets. Anyone who has seen whole sections of the Veil in the same FOV, Orion Nebula, M33, M27, North American Nebula, Andromeda Galaxy+companions, both M81+M82, all the goodies in the south in Summer, etc...etc...etc... at the ep knows what I speak with this type of refractor.
Know your tools well and use them accordingly....
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galaxyman
Vendor - Have a Stellar Birthday
Reged: 04/04/05
Loc: Limerick, Pa
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Re: Using refractors for Deep Space Observing
[Re: hfjacinto]
#5264745 - 06/10/12 01:29 PM
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Can we stop with the quality point. Lets gets this out of the way, most mass produced scopes have good quality. I've looked through lots of scopes and seen very few dogs. The premium dobs as a rule have very nice mirrors. The chances of getting a bad telescope is the same no matter the brand ( friend onwed a Tec 140, that came uncolllimated). And I while repeat this again, for DSOs aperture rules.
Mike,
Have you actually looked through the 10" refractor? It was hand made and is over 40 years old. Optically its very good, so my opinion still holds. A 14" SCT or 14" Dob shows more.
Now as this is the refractor forum, I am supposed to state refractors do all perfect, thats simply not true, for deep sky aperture rules and refractors are limited in that regard.
Again yes and no
Depends on the type of DSO observing your doing or into. Yes, most massed produced optics are okay, and they'll do okay for general DSO observing. The same can be said for planetary observing.
The high quality optics will benefit pushing DSO observing to the edge (like I have). No different then someone doing the same for planetary.
I've owned 10" newts of fair optical quality, and they could not be pushed like my current 8" refractor. Not saying a very good 10" could not, but even still I'll take the refractor views in this aperture range.
Karl
E.O.H.
Chesmont Astronomical Society - www.chesmontastro.org
Deep Space with Refractors - http://tech.groups.yahoo.com/group/deepspacewithrefractors
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB/APM 8" f/9 Refractor”The Beast”. One great DEEP SKY achro
ES 6" f/6.5 achro. Good one
Celestron Omni XLT 102 refractor.
Celestron 10x60mm Binos
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Javier
Carpal Tunnel
Reged: 05/03/09
Loc: 15 Minutes west of the Manhatt...
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Re: Using refractors for Deep Space Observing
[Re: hfjacinto]
#5264809 - 06/10/12 02:11 PM
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I'm not sure if I blindly subscribe or accept the "aperture rules" blanket statement. Here's why. Yes in theory all things being equal "aperture rules". However, nothing is ever equal and this blanket statement that is casually tossed around like a flower girl tosses flowers down the aisle should be re-examined.
Indeed, given the same observer with the physical capacity to lift a 60mm refactor and a 24" reflector the aperture will indeed benefit this individual. Yet, when making this blanket statements we tend to forget that many observers suffer from physical issues that prevent them from moving large and heavy telescopes and equipment. Thus the aperture that would rule for these observers is an aperture that provides mobility, comfort and quality observing time. Having a big heavy telescope of massive aperture and weight is of no advantage if it is beyond the physical, time and comfort limitations of the observer.
Secondly, these blanket statements may make folks with certain physical limitations feel as if they are missing out on some mystical part of amateur astronomy and that is simply unfair and unrealistic. Our hobby is about observing objects that are within the physical limits of our bodies and finances.
There was a time when for me nothing but a 12" or bigger Dob ruled, then somewhere along the line I realized that the amount of work I had to do to get the 12" setup wasn't worth it. Now I observe with either a C6R or a 8" EdgeHD and I'm more comfortable and my observing sessions which are limited to perhaps 40 to 60 minutes per session are more enjoyable and productive.
When tossing around these blanket statements stop and think about those folks that either physically or financially can't afford these big scopes and how these statements may make them feel.
Aperture doesn't rule, looking up and observing does.....
Soap box back in corner. Those that feel like they need to flame me go ahead but someone had to say something.
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Astrojensen
Post Laureate
Reged: 10/05/08
Loc: Bornholm, Denmark
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Re: Using refractors for Deep Space Observing
[Re: Javier]
#5264847 - 06/10/12 02:37 PM
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Aperture doesn't rule, looking up and observing does.....
Bravo!
Clear skies!
Thomas, Denmark
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7331Peg
Sirius Observer
Reged: 09/01/08
Loc: North coast of Oregon
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Re: Using refractors for Deep Space Observing
[Re: Astrojensen]
#5264904 - 06/10/12 03:21 PM
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A second Bravo!
That statement pretty well puts this whole discussion into the proper perspective.
John 
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jmiele
Patron Saint?
Reged: 12/04/10
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Re: Using refractors for Deep Space Observing
[Re: Refractor6]
#5264939 - 06/10/12 03:47 PM
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Wayne,
I was addressing a specific statement the previous poster made. That comment was quoted in my response. I was not attempting to dispute or defend the use of refractors for DSO.
Regards, Joe
Edited by jmiele (06/10/12 04:03 PM)
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cheapersleeper
Carpal Tunnel
Reged: 01/22/10
Loc: Sachse TX
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Re: Using refractors for Deep Space Observing
[Re: JoeR]
#5264961 - 06/10/12 04:03 PM
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It would be an amusing exercise to pull out and compile all the subjective words being used to describe the image of refractors as opposed to other types of scopes. I think if we did that maybe we could get to the truth of this topic: Many people who own high end refractors prefer the views through high end refractors. Put in this way, it's pretty obviously a group sorted for a love of refractors...
Edited by cheapersleeper (06/10/12 04:04 PM)
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JimP
Pooh-Bah
Reged: 04/22/03
Loc: South Carolina
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Re: Using refractors for Deep Space Observing
[Re: hfjacinto]
#5264979 - 06/10/12 04:16 PM
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Now as this is the refractor forum, I am supposed to state refractors do all perfect, thats simply not true, for deep sky aperture rules and refractors are limited in that regard.
No, you're not "supposed" to say anything. That's just a cheap shot. IF the 10" refractor you mentioned is collimated and of good optical quality I am shocked that you would prefer a C14 over it for Anything. I can assure you that I would NOT.
JimP
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mikey cee
Postmaster
Reged: 01/18/07
Loc: bellevue ne.
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Re: Using refractors for Deep Space Observing
[Re: JimP]
#5265215 - 06/10/12 07:11 PM
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Now as this is the refractor forum, I am supposed to state refractors do all perfect, thats simply not true, for deep sky aperture rules and refractors are limited in that regard.
No, you're not "supposed" to say anything. That's just a cheap shot. IF the 10" refractor you mentioned is collimated and of good optical quality I am shocked that you would prefer a C14 over it for Anything. I can assure you that I would NOT.
JimP
Yeah and that's the name of that tune! OK mods lock'er up!  Mike
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Javier
Carpal Tunnel
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Re: Using refractors for Deep Space Observing
[Re: mikey cee]
#5265247 - 06/10/12 07:45 PM
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I don't see much of a reason to lock the thread yet. I'm on my mobile phone but I would like to be able to respond to the original poster's question.
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Javier
Carpal Tunnel
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Loc: 15 Minutes west of the Manhatt...
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Re: Using refractors for Deep Space Observing
[Re: aa6ww]
#5265390 - 06/10/12 10:01 PM
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Hi Ralph,
I've also gone the smaller refactor route and let my 12" Dobsonian go to another home. My reasons are many, first yes, I do love the pin-point stars the refractors produce. In the past two years my observing taste has gone from the typical Messier Objects and Open or Globular Clusters to double stars. It's a rare night when I take out my C6R to observe any DSO's. These day's DSO's are objects I may observe if I have time after a double star observing session. This does not have much to do with the light polluted are I live in, rather it has to do with the objects I like to observe.
With that said, when I do observe DSO's such as M3, M13, M31, M42 and open clusters, I find the view through my C6R more aesthetically pleasing than a larger aperture 12" Newt. Also with a refactor, it seems that I notice more subtle structure in many of the DSO's mentioned above. While the DSO(s) many not be as bright as they were in the 12" Dob, I began to notice that while using my refactor I did not use averted vision as much as I did with the Dobsonian.
One other factor that has influenced my choice in gear is time. As the father of a six year old there are many instances where there is not enough time to get home after a school function, trip or whatever and setup a 12" Dob allow it to acclimate (especially during the cold winter). Yet there have been many instances during the winter where we will arrive after say a Parent's Night meeting or an evening school play and I can setup my C6R and within 30-40 minutes I can be observing.
These days I am not finding much of an urge to use a telescope with an aperture larger than 8". In fact I have come to realize that the sweet spot for my taste in gear is either the six or eight inch aperture arena with a preference for my C6R. As a side note, I do own a 8" EdgeHD and while I also find the views through the 8" Edge very pleasing when pressed for acclimation time I also reach for the C6R.
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hfjacinto
I think he's got it!
Reged: 01/12/09
Loc: Land of clouds and LP
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Re: Using refractors for Deep Space Observing
[Re: Javier]
#5265426 - 06/10/12 10:28 PM
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If you want to view DSO's with a refractor that is great (and many times that is what I do) but for most DSO's a larger aperture scope is better, it shows a brighter image with more details. That is a fact. Whether you want to take out a 6" F8 refractor which is a large scope or a 14" SCT that is up to you. But there is no way a small refractor will show as much as a much larger reflector, no matter what you paid for the premium APO. The endless arguments over how much better refractors over all other scopes are stupid.
Edited by hfjacinto (06/10/12 10:29 PM)
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Daniel Mounsey
Post Laureate
Reged: 06/12/02
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Re: Using refractors for Deep Space Observing
[Re: hfjacinto]
#5265495 - 06/10/12 11:05 PM
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Instead of debating over what scope the observer should be using, why are we not addressing what objects are being observed? Ultimately it's the "object" which determines what kind of telescope the observer should be using. Beginners are not being educated enough on how to observe.
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JimP
Pooh-Bah
Reged: 04/22/03
Loc: South Carolina
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Re: Using refractors for Deep Space Observing
[Re: hfjacinto]
#5265587 - 06/11/12 12:11 AM
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If you want to view DSO's with a refractor that is great (and many times that is what I do) but for most DSO's a larger aperture scope is better, it shows a brighter image with more details. That is a fact. Whether you want to take out a 6" F8 refractor which is a large scope or a 14" SCT that is up to you. But there is no way a small refractor will show as much as a much larger reflector, no matter what you paid for the premium APO. The endless arguments over how much better refractors over all other scopes are stupid.
No, I will take out my TMB 10" F/9 apo and you can use your C14! We will Both be happy (At least I know I will be).
And you should consider discussing a topic without resorting to calling people names as it just shows your lack of vocabulary.
JimP
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Refractor6
Post Laureate
Reged: 10/20/04
Loc: Vancouver B.C. , Canada
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Re: Using refractors for Deep Space Observing
[Re: Daniel Mounsey]
#5265715 - 06/11/12 03:07 AM
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Instead of debating over what scope the observer should be using, why are we not addressing what objects are being observed? Ultimately it's the "object" which determines what kind of telescope the observer should be using. Beginners are not being educated enough on how to observe.
Couldn't agree more and a few of us have taken the time in this thread to cover that very POV. Certain countless deep sky objects can really shine when the target in question is combined with right scope {tool for the job} for the task at hand.
Do you want to see ALL of the North American Neb with room to spare with a OIII in place at the ep with excellent contrast and pinpoint stars across the entire FOV to boot or only a small portion of it with a larger and much longer F/ratio larger aperture scope that can show you only a small fraction of it at a time?
The visual observer who's knows what's required for the job will choose the best scope from experience for that type of large scale deep sky object which is not always the exclusive arena of the bigger scope with a much narrower field of view in many cases for this type of object viewing experience.
Like Daniel said... know the object and know THE SCOPE for best seeing the entire deep sky object you want to observe when it comes to certain beautiful targets in our wonderful night sky. One size {or focal length} does not fit all....
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JJK
scholastic sledgehammer
Reged: 04/28/08
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Re: Using refractors for Deep Space Observing
[Re: Eddgie]
#5265845 - 06/11/12 08:13 AM
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First, I keep reading that refractors have better contrast.
This is simply untrue in most cases. If a reflector has more clear aperture (primary diameter minus secondary diameter) it will have as good or better contrast than a smaller unobstructed scope with less clear aperture.
SNIP
Eddgie, there's no doubt that a much larger reflector (Newt, SCT) will collect more light than a smaller refractor, and thus will be more useful for detecting fainter DSOs. However, if a refractor and compound reflector have the same clear aperture, the refractor will exhibit better contrast on extended objects (especially assuming we're comparing a top-notch refractor against a fast food SCT). The SCT's modulation transfer function is compromised because its secondary transfers some of the light energy from the central portion of the Airy disk to the outer rings. The only thing that artifact aids is the separation of double stars of nearly the same magnitude. It cannot enhance the contrast of extended objects or the visual separation of double stars of much different magnitude.
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JJK
scholastic sledgehammer
Reged: 04/28/08
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Re: Using refractors for Deep Space Observing
[Re: maknewtnut]
#5265851 - 06/11/12 08:18 AM
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Jim,
I echo your opinon. The fact is an almost perfect refractor will outperform a larger "Abberation-Limited" Dob or SCT every-time. The optical flaws of mass produced mirror scopes create the "mushy", cotton balls, and fuzies. Often a superior quality handmade refractor like an AP or Stellarvue will show DS0 detail those larger mirror scopes cannot.
Also it is much harder to test properly especially in the figuring process large uncoated mirrors with interferometry.
Mark
The term you might have been trying to refer to is diffraction limited.
To refer to an A-P as a handmade telescope can be argued as accurate. Stellarvue telescopes (at least most, and certainly most all in recent years) use optics made in China, which are also used by several other makers. They are most definitely not hand crafted in any manner that might be considered akin to A-P and TEC.
Your comment about testing uncoated reflective surfaces might be construed as misleading as many superior quality mirrors are effectively tested both during and after figuring.
He may well have meant aberration limited. While fast food SCTs have their place in an amateur astronomer's arsenal (I'll eventually get a C-14 to "complete" my collection), their optics are compromised compared to those in a high-end apo.
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Jon Isaacs
Postmaster
Reged: 06/16/04
Loc: San Diego and Boulevard, CA
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Re: Using refractors for Deep Space Observing
[Re: Daniel Mounsey]
#5265852 - 06/11/12 08:20 AM
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Instead of debating over what scope the observer should be using, why are we not addressing what objects are being observed? Ultimately it's the "object" which determines what kind of telescope the observer should be using. Beginners are not being educated enough on how to observe.
Exactly... And to take that a step further, it depends on what details in an object one is interested in. Viewing the entire Veil in a 4 inch refractor is quite wonderful but if one wants to see details in the various parts a larger scope is more effective.
A simple Target like m7 seems perfect for a smaller scope but comes alive and takes on new dimensions when viewed in a 16 inch... There are aspects of M7 that are just not apparent in a 4 or 6 inch scope.
When the skies are dark and clear, I always setup two scopes. One small and one large... It's really the only way... It's like asking a photographer. "Which is the better lens, a 28mm f/2 or a 400mm f/4?" The answer depends on the object being photographed. There will be one of each in the camera bag.
As far as optical quality and DSOs... It is rare that one is pushing the resolving capabilties of a larger scope when viewing deep sky. It is generally a question of enough light and enough magnification for the eye to see it. A small scope with a camera will show the same detail as a much larger scope used visually. This is not because the smaller scope is of better quality, it would show less if used visually, rather it is because to the resolving power of the eye is the limitation, not the resolving power of the telescope.
The key to seeing more is looking more. Having good quality equipment is important but the message to beginners that it is their equipment that most important is the wrong message. What is important is to get out there with whatever it is you have and spend as much time as possible developing your skills...
Refractors are good for deep space, reflectors are good for deep space. Clear skies, dark skies and time at the eyepiece, that's what its all about...
Jon Isaacs
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