Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

1 inch APO vs 12 inch SCT

  • Please log in to reply
461 replies to this topic

#76 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 85,789
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 02 January 2018 - 07:30 PM

I would like to see Zambuto or Mike Lockwood work on one of these run of the mill SCT's.  I am sure it would cost much more.

 

 

Yellobeard lives in the Netherlands.  For whatever reason, it seems that the Netherlands is home to talented optical folks, some of whom have spent time making some very nice SCTs.  I imagine Yellobeard knows Rik ter Horst, Rik's has also built some very nice SCTs along with a variety of other scopes.   

 

This is a Rik's 8inch F/25 SCT with a 20% CO.  I have to think it provides some amazing planetary views:

 

158978001.hTCMVDeD.jpg

 

http://www.pbase.com...scopes&page=all

 

Since the topic is 1 inch apos, here's Rik's 30mm (1.18") SCT:

 

https://www.cloudyni...idt-cassegrain/

 

156298833.4KDHpuR8.Solidstateinhand.jpg

 

Jon


  • Daniel Mounsey, Erik Bakker, Phil Cowell and 7 others like this

#77 mikona

mikona

    Ranger 4

  • *****
  • Posts: 372
  • Joined: 04 Jun 2016

Posted 02 January 2018 - 08:26 PM

 

I would like to see Zambuto or Mike Lockwood work on one of these run of the mill SCT's.  I am sure it would cost much more.

 

 

Yellobeard lives in the Netherlands.  For whatever reason, it seems that the Netherlands is home to talented optical folks, some of whom have spent time making some very nice SCTs.  I imagine Yellobeard knows Rik ter Horst, Rik's has also built some very nice SCTs along with a variety of other scopes.   

 

This is a Rik's 8inch F/25 SCT with a 20% CO.  I have to think it provides some amazing planetary views:

 

158978001.hTCMVDeD.jpg

 

http://www.pbase.com...scopes&page=all

 

Since the topic is 1 inch apos, here's Rik's 30mm (1.18") SCT:

 

https://www.cloudyni...idt-cassegrain/

 

156298833.4KDHpuR8.Solidstateinhand.jpg

 

Jon

 

I want one of these 



#78 CHASLX200

CHASLX200

    ISS

  • *****
  • Posts: 20,038
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 02 January 2018 - 09:01 PM

 

 

I would like to see Zambuto or Mike Lockwood work on one of these run of the mill SCT's.  I am sure it would cost much more.

 

 

Yellobeard lives in the Netherlands.  For whatever reason, it seems that the Netherlands is home to talented optical folks, some of whom have spent time making some very nice SCTs.  I imagine Yellobeard knows Rik ter Horst, Rik's has also built some very nice SCTs along with a variety of other scopes.   

 

This is a Rik's 8inch F/25 SCT with a 20% CO.  I have to think it provides some amazing planetary views:

 

158978001.hTCMVDeD.jpg

 

http://www.pbase.com...scopes&page=all

 

Since the topic is 1 inch apos, here's Rik's 30mm (1.18") SCT:

 

https://www.cloudyni...idt-cassegrain/

 

156298833.4KDHpuR8.Solidstateinhand.jpg

 

Jon

 

I want one of these 

 

Me 2...



#79 555aaa

555aaa

    Vendor (Xerxes Scientific)

  • *****
  • Vendors
  • Posts: 1,777
  • Joined: 09 Aug 2016
  • Loc: Lynnwood, WA, USA

Posted 02 January 2018 - 11:11 PM

I'll see your 36mm cass (totally cute btw)  and raise you a reverse cassegrain microscope objective. It's 5mm focal length, about f/1.

 

https://www.newport....cope-objectives


  • treadmarks likes this

#80 Erik Bakker

Erik Bakker

    Cosmos

  • *****
  • Moderators
  • Posts: 8,830
  • Joined: 10 Aug 2006
  • Loc: Netherlands, Europe

Posted 03 January 2018 - 03:47 AM

To put it into perspective: Rik joined me for a long observing session with my Tak FS102NSV. He was amazed at it's views and started to get serious about high-end apo doublets for high power visual use. Mirror man as he is.

 

SCT's, Mak's or Newt's that are made to perfection are fantastic performers. From 2"-7", per aperture, they will never beat a high-end apo. But they are limited in aperture due to size, weight and cost,  more so with a stable driven mount. Then at about 8", we enter a turning point. Refractors now enter a territory where their well known advantages start to become less pronounced, disadvantages become more apparent and gradually the mirror scopes come into play. In the 10" size, I prefer a high-end Mak, in the 16" size a top quality Newt. But in 2"-6" the image quality at any power of a high-end refractor rules. And each shows a different sky to the observer.


  • Jon Isaacs, turtle86, Astrojensen and 2 others like this

#81 CHASLX200

CHASLX200

    ISS

  • *****
  • Posts: 20,038
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 03 January 2018 - 06:14 AM

To put it into perspective: Rik joined me for a long observing session with my Tak FS102NSV. He was amazed at it's views and started to get serious about high-end apo doublets for high power visual use. Mirror man as he is.

 

SCT's, Mak's or Newt's that are made to perfection are fantastic performers. From 2"-7", per aperture, they will never beat a high-end apo. But they are limited in aperture due to size, weight and cost,  more so with a stable driven mount. Then at about 8", we enter a turning point. Refractors now enter a territory where their well known advantages start to become less pronounced, disadvantages become more apparent and gradually the mirror scopes come into play. In the 10" size, I prefer a high-end Mak, in the 16" size a top quality Newt. But in 2"-6" the image quality at any power of a high-end refractor rules. And each shows a different sky to the observer.

I will take my FS78 over any other small scope. Easy 100x per inch scope. Had two of them.



#82 Daniel Mounsey

Daniel Mounsey

    Vendor (Woodland Hills)

  • *****
  • Vendors
  • Posts: 7,830
  • Joined: 12 Jun 2002

Posted 03 January 2018 - 09:16 AM

 

It’s actually a psychological issue.  When someone buys something that costs a lot of money, say a 5 inch APO for $7000, they then develop a “cognitive bias” where they need to justify to themselves that it was worth it.  Here’s an explanation from Wikipedia:

 

“In cognitive science, choice-supportive bias or post-purchase rationalization is the tendency to retroactively ascribe positive attributes to an option one has selected. It is a cognitive bias. For example, if a person chooses option A instead of option B, they are likely to ignore or downplay the faults of option A while amplifying those of option B. Conversely, they are also likely to notice and amplify the advantages of option A and not notice or de-emphasize those of option B.l

I respectfully disagree with you on this one.  Since my 5" apo was acquired for $0.00 dollars due to the generosity of the wonderful folks at Astronomics, I don't have to justify the performance based on $$$ layed out on the purchase.  Scopes do what scopes do - meaning that the characteristics and attributes of each individual design (and implementation of that design) when combined with seeing conditions determine the performance of that particular set of optics at that particular time.  I tend to believe that people drawn to high end apochromatic scopes are a rather picky bunch of folks.  If you watch the discussions on CN's they debate endlessly on .997 strehl vs. .998 strehl, color correction at 100X/inch of aperture, and contrast levels capable of discerning minute low contrast details on planets.

 

That being said - if they are picky about (and truthful about) minute differences between refractive optics, I tend to believe they can tell the performance differences between mirrored scopes and refractors.  If you are looking for the highest quality optics available, you tend to be picky about the views presented in the EP - no matter what the design.

 

I think the majority of the folks here on CN's who choose high end optics, whether they prefer big achromats (like D&G), tiny apochromats, or  a Takahashi Mewlon have a full realization of the performance benefits and limitations of these scopes.  

 

Setting scopes side by side on a particular evening usually gives "the expected" results related to resolution and sharpness, but depending on the conditions, you might find the results don't always match theory...   wink.gif

 

 

I cant speak for everyone, but I use all my scopes for specific reasons. I have zero regrets on their cost and I understand why I have them. For me, Sandy's post wouldn't apply. That's like telling me I don't understand or appreciate what these smaller fracs do for me when in fact I already explained what they do well. Perhaps in Sandy's case there are some people who have fancy scopes who are just down right equipment junkies and don't even understand the attributes each scope brings to the Sky. I appreciate what they all do for observation. I remember a night my friends and I had at Derek Wong's place. There were two scopes set up, an 8" TEC ED refractor and a 65mm ED Nikon refractor. When I saw the figure and quality of the 65mm Nikon ED I couldn't stop looking at double stars through it, so all my friends were crowded around this little scope captivated as to why I was looking through this instead of the 8" ED. Derek walked over and says, I got an 8" apo over here and all you guys are standing around this little scope!.... what gives? I looked at Derek and said, you will never see an image of Mizar this beautiful through any other scope including that TEC. Then I started looking at other doubles with it and used the scope the entire night.

 

Yes the 8" TEC has greater light gathering and greater resolving power, but not everything you look at requires that. If you are comparing M13 and stating that the 65mm is not as good then it's your own fault or not using the scopes correctly, hello. Part of knowing the night sky and knowing telescopes is understanding what they can and can not do. The problem is that people just don't have enough familiarity with the night sky. More often than not, they just buy these fancy goto scopes and think all the sudden that solves their problem. You still need to learn what's out there after tour mode. That's something goto doesn't teach. Would you like to buy an inexpensive observing guide? No, I got the goto. I've never seen such a bunch of disconnected equipment junkies in my life.  Telescopes don't need hundreds of thousands of objects. All they need is a hand controller that has GPS with M13, M42, and M31 on the handset. I have sold thousands of telescopes. When these people come to my star parties, they're all just looking at the same thing over and over every month. They don't grow and they don't realize there's other wonderful objects outside the Messier catalog that look amazing in all sorts of apertures, even small ones. The Messier catalog is like a crutch for these people. I'd like to remove the Messier objects from the night sky for a few days and see how long they last. They'd be closing shop and heading home for good. I'd say.... Hey! but what about that all those hundreds of thousands of objects in the database you wanted? Don't you want to see those? Naaahhhh I just want to see bright showpieces all night. 

 

Look at the knowledge and experiences these guys bring to the table using just modest telescopes. These guys are experts!

 

https://bestdoubles....ueger-60-kr-60/


Edited by Daniel Mounsey, 03 January 2018 - 03:46 PM.

  • Joe Bergeron, Scott Beith, Phil Cowell and 2 others like this

#83 Arizona-Ken

Arizona-Ken

    Surveyor 1

  • *****
  • Posts: 1,875
  • Joined: 31 Aug 2008
  • Loc: Scottsdale, Arizona

Posted 03 January 2018 - 10:20 AM

.... Telescopes don't need hundreds of thousands of objects. All they need is a hand controller that has GPS with M13, M42, and M31 on the handset. I have sold thousands of telescopes. When these people come to my star parties, they're all just looking at the same thing over and over every month. They don't grow and they don't realize there's other wonderful objects outside the Messier catalog that look amazing in all sorts of apertures, even small ones. The Messier catalog is like a crutch for these people. I'd like to remove the Messier objects from the night sky for a few days and see how long they last. They'd be closing shop and heading home for good. I'd say.... Hey! but what about that all those hundreds of thousands of objects in the database you wanted? Don't you want to see those? Naaahhhh I just want to see bright showpieces all night. 

 

As a comment upon this part of Daniel's post, I, too often wonder about people looking at the same objects over and over. In my case, I have some observing goals, initially the Messiers, then the Herschel 400, now an amalgam of objects culled from various deep sky lists I have acquired. I am just getting started on double stars (only have observed a couple of hundred or so) and the challenge of splitting doubles is really fun. I like goals. It keeps things fresh for me and is always sharpening my observing skills, which include getting to know the limitations of my equipment.

 

I always check a few of my favorite M-objects, as they are my friends, and have observed them enough to use them to rather easily get a read on the observing conditions for the night. I also use the M-objects to check out a new eyepiece, filter, or new scope.

 

Lots of objects up there. Thankfully, I'll never get them all.

 

Arizona Ken


  • Jon Isaacs, Phil Cowell and Astrojensen like this

#84 SandyHouTex

SandyHouTex

    Aurora

  • *****
  • Posts: 4,776
  • Joined: 02 Jun 2009
  • Loc: Houston, Texas, USA

Posted 03 January 2018 - 10:29 AM

 

It’s actually a psychological issue.  When someone buys something that costs a lot of money, say a 5 inch APO for $7000, they then develop a “cognitive bias” where they need to justify to themselves that it was worth it.  Here’s an explanation from Wikipedia:

 

“In cognitive science, choice-supportive bias or post-purchase rationalization is the tendency to retroactively ascribe positive attributes to an option one has selected. It is a cognitive bias. For example, if a person chooses option A instead of option B, they are likely to ignore or downplay the faults of option A while amplifying those of option B. Conversely, they are also likely to notice and amplify the advantages of option A and not notice or de-emphasize those of option B.l

I respectfully disagree with you on this one.  Since my 5" apo was acquired for $0.00 dollars due to the generosity of the wonderful folks at Astronomics, I don't have to justify the performance based on $$$ layed out on the purchase.  Scopes do what scopes do - meaning that the characteristics and attributes of each individual design (and implementation of that design) when combined with seeing conditions determine the performance of that particular set of optics at that particular time.  I tend to believe that people drawn to high end apochromatic scopes are a rather picky bunch of folks.  If you watch the discussions on CN's they debate endlessly on .997 strehl vs. .998 strehl, color correction at 100X/inch of aperture, and contrast levels capable of discerning minute low contrast details on planets.

 

That being said - if they are picky about (and truthful about) minute differences between refractive optics, I tend to believe they can tell the performance differences between mirrored scopes and refractors.  If you are looking for the highest quality optics available, you tend to be picky about the views presented in the EP - no matter what the design.

 

I think the majority of the folks here on CN's who choose high end optics, whether they prefer big achromats (like D&G), tiny apochromats, or  a Takahashi Mewlon have a full realization of the performance benefits and limitations of these scopes.  

 

Setting scopes side by side on a particular evening usually gives "the expected" results related to resolution and sharpness, but depending on the conditions, you might find the results don't always match theory...   wink.gif

 

The "particular" does not negate the "general".



#85 OleCuss

OleCuss

    Mercury-Atlas

  • *****
  • Posts: 2,655
  • Joined: 22 Nov 2010

Posted 03 January 2018 - 10:32 AM

I'm very thankful that the Messier catalog is out there and used.

 

There are people who are just not going to delve into the other stuff.  They don't get double stars.  They aren't going to struggle to find something relatively dim no matter how amazing.

 

My wife is sort of one of those - let her get some brief looks through the eyepiece at some of the brighter stuff in the sky and she is happy.  Doing some of the stuff I like to do bores or frustrates her to no end.

 

That's the wonderful thing about astronomy:

  • Every eye is different.  This means that all else being equal we still don't see the same thing.
  • Every night is a little different.  This means even if your equipment and eye are the same - you won't see quite the same thing in the same way.
  • Different scopes will show you the same thing in different ways.  One way is not necessarily better than another, but they are different and I like that.
  • Different targets teach us different things about ourselves, our universe, and our equipment.
  • All forms of enjoying amateur astronomy are valid.  If people just want to do the book/internet learning that is great.  If you want to do naked eye observing that is excellent.  If you want to use optics to enhance your viewing, well that is awesome as well.  If you want to do imaging, that is also superb.  You find another way or want to mix them all up - that may be perfect for you.
  • Astronomy may teach you non-astronomical things as well.  People learn some construction, optics, engineering, mechanical, landscaping, relationship, philosophical, financial, and maybe spiritual things in the course of their amateur astronomy experience.  Sometimes out of necessity and sometimes out of pleasure.

Astronomy is a wondrous thing and it is too bad that many never explore it to see what it holds for them in particular.


  • Jon Isaacs likes this

#86 SandyHouTex

SandyHouTex

    Aurora

  • *****
  • Posts: 4,776
  • Joined: 02 Jun 2009
  • Loc: Houston, Texas, USA

Posted 03 January 2018 - 10:35 AM

To put it into perspective: Rik joined me for a long observing session with my Tak FS102NSV. He was amazed at it's views and started to get serious about high-end apo doublets for high power visual use. Mirror man as he is.

 

SCT's, Mak's or Newt's that are made to perfection are fantastic performers. From 2"-7", per aperture, they will never beat a high-end apo. But they are limited in aperture due to size, weight and cost,  more so with a stable driven mount. Then at about 8", we enter a turning point. Refractors now enter a territory where their well known advantages start to become less pronounced, disadvantages become more apparent and gradually the mirror scopes come into play. In the 10" size, I prefer a high-end Mak, in the 16" size a top quality Newt. But in 2"-6" the image quality at any power of a high-end refractor rules. And each shows a different sky to the observer.

The is no such thing as "never".  If properly made with high quality optics, and then properly collimated, an 8 inch SCT will beat a 6 inch APO all the time in similar atmospheric conditions.

 

Unless of course you believe the physics of optics are incorrect.



#87 SandyHouTex

SandyHouTex

    Aurora

  • *****
  • Posts: 4,776
  • Joined: 02 Jun 2009
  • Loc: Houston, Texas, USA

Posted 03 January 2018 - 10:48 AM

What I always laugh about, because it is ridiculous, is the "my refractor has pinpoint stars while SCTs give bloated star images".  I hear it all of the time, but of course it's not true.  Here's the equation valid for all telescopes for angular resolution:

 

Angular resolution = 116/D, where the wavelength is 550 nm and the (D)iameter of the scope's primary is in mm.

 

Note that the resolution is inversely proportional to D.  Meaning that you can resolve smaller things with larger scopes.  There is no dependency in this equation for the type of telescope.  Nor is there an different equation for APOs versus SCTs.

 

I think many times the SCTs with "bloated" images are just not in equilibrium with the environment.  I have seen this happen with APO triplets that are airspaced.  It takes awhile for them to cool down as well.


  • eklf and sonny.barile like this

#88 treadmarks

treadmarks

    Apollo

  • -----
  • Posts: 1,059
  • Joined: 27 Jan 2016
  • Loc: Boston MA

Posted 03 January 2018 - 11:14 AM

 

.... Telescopes don't need hundreds of thousands of objects. All they need is a hand controller that has GPS with M13, M42, and M31 on the handset. I have sold thousands of telescopes. When these people come to my star parties, they're all just looking at the same thing over and over every month. They don't grow and they don't realize there's other wonderful objects outside the Messier catalog that look amazing in all sorts of apertures, even small ones. The Messier catalog is like a crutch for these people. I'd like to remove the Messier objects from the night sky for a few days and see how long they last. They'd be closing shop and heading home for good. I'd say.... Hey! but what about that all those hundreds of thousands of objects in the database you wanted? Don't you want to see those? Naaahhhh I just want to see bright showpieces all night. 

 

As a comment upon this part of Daniel's post, I, too often wonder about people looking at the same objects over and over. In my case, I have some observing goals, initially the Messiers, then the Herschel 400, now an amalgam of objects culled from various deep sky lists I have acquired. I am just getting started on double stars (only have observed a couple of hundred or so) and the challenge of splitting doubles is really fun. I like goals. It keeps things fresh for me and is always sharpening my observing skills, which include getting to know the limitations of my equipment.

 

I always check a few of my favorite M-objects, as they are my friends, and have observed them enough to use them to rather easily get a read on the observing conditions for the night. I also use the M-objects to check out a new eyepiece, filter, or new scope.

 

Lots of objects up there. Thankfully, I'll never get them all.

 

Arizona Ken

 

This is something I've been thinking about with respect to my own observing strategy. There was an awfully judgmental tone towards people who gravitate towards "showpiece" objects. Maybe some people prefer quality over quantity? Oftentimes when I look at some sparse, dim open cluster or whatever, I get the feeling I'm just looking at a weak, discount M45.

 

That's not to say I don't try to find new objects every night. But I'm looking for a winner. Just as some people don't understand why you'd look at the same objects over and over, I don't understand why you'd get excited about some gray blob that's so dim it could be mistaken for dew on the eyepiece.

 

There are lots of things to see up there, and lots of winners to find. But they can't all be winners.


  • eklf likes this

#89 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 85,789
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 03 January 2018 - 11:20 AM

As a comment upon this part of Daniel's post, I, too often wonder about people looking at the same objects over and over. In my case, I have some observing goals, initially the Messiers, then the Herschel 400, now an amalgam of objects culled from various deep sky lists I have acquired. I am just getting started on double stars (only have observed a couple of hundred or so) and the challenge of splitting doubles is really fun. I like goals. It keeps things fresh for me and is always sharpening my observing skills, which include getting to know the limitations of my equipment.

 

I always check a few of my favorite M-objects, as they are my friends, and have observed them enough to use them to rather easily get a read on the observing conditions for the night. I also use the M-objects to check out a new eyepiece, filter, or new scope.

 

Lots of objects up there. Thankfully, I'll never get them all.

 

 

I think a balance between old friends and new objects is important. 

 

I find that no matter how many times I look at an object,  it's always fresh.  And,  there's always something more to see.  One of my favorite examples is M7.. Many think of it as a bright cluster well suited for a small scope and it is that.  But with a large scope,  it takes on new dimensions,  associated faint clusters, a 10the magnitude globular.. 

 

Another favorite is Hickson 68. Not quite a Messier  but it's a nice galaxy cluster with 11th magnitude galaxies, a double pointing at a magnitude 14.6 galaxy and interesting galaxies nearby. 

 

In terms of Daniels comment about people looking at only a few objects,  I am sure he has more experience with that,  I am pretty much a lone wolf..  Some nights I'll spend mostly looking at familiar objects,  there's a lot to see in M33 or the galaxy's near Phecda.  Other nights I'll mostly be searching out new objects. 

 

I am very much in agreement with Daniel about the right telescope for the job,  the right telescope for the moment.  A photographer has several lens and chooses them accordingly.  The lens used for baby pictures is not a good choice to capture that Hawk on a telephone pole. 

 

But I also believe that what ever you're doing,  as long as you're having fun,  that's all that counts. 

 

Jon


  • Daniel Mounsey, Erik Bakker, Phil Cowell and 2 others like this

#90 Erik Bakker

Erik Bakker

    Cosmos

  • *****
  • Moderators
  • Posts: 8,830
  • Joined: 10 Aug 2006
  • Loc: Netherlands, Europe

Posted 03 January 2018 - 11:23 AM

 

The is no such thing as "never".  If properly made with high quality optics, and then properly collimated, an 8 inch SCT will beat a 6 inch APO all the time in similar atmospheric conditions.

 

Unless of course you believe the physics of optics are incorrect.

 

 

Please note, I said: per aperture. So 6" APO vs 6" SCT.  Not 6" vs 8".

 

Careful observing helps when comparing. So I am curious how you compare the performance of your Celestron NexStar 6SE vs your Tak FS152.

 

I know my 4" FS102 beats my 5" C5 on any object at any magnification and both have good optics from their manufacturers. Only on bulk/portability the C5 beats the FS102.

 

For sure, you will have a LOT more trouble finding an 8 " SCT wit high quality optics of the same quality as a high end 6" APO.

It's mass produced vs limited hand crafted runs.

 

I've never seen a better 8" SCT than an 6" APO so far. They are just different animals. Horses for courses if you like.

 

For reference I will say that I have and like many types of scopes and love them all for what they can do.


  • Daniel Mounsey likes this

#91 Astrojensen

Astrojensen

    Voyager 1

  • *****
  • Posts: 13,185
  • Joined: 05 Oct 2008
  • Loc: Bornholm, Denmark

Posted 03 January 2018 - 11:46 AM

The is no such thing as "never".  If properly made with high quality optics, and then properly collimated, an 8 inch SCT will beat a 6 inch APO all the time in similar atmospheric conditions.

 

 

 

Unless of course you believe the physics of optics are incorrect.

 

In my experience (visual observing), this is simply not true, if we are talking about bog standard, run-of-the-mill 8" SCT's, no matter how excellent their optics are. The 6" refractor (it doesn't have to be an apochromat) will be FAR less sensitive to thermal issues than the 8" SCT and so under many observing conditions, especially in rapidly falling temperatures, which we often see where I live, the refractor will easily outperform the SCT, simply because it can track the temperature better. On a few nights each year, the SCT will be able to show its superior resolution, but generally the refractor will show better planetary images. On deep-sky, the results will be more mixed and depend on the object type. On large galaxies and nebulae, the refractor could be better, while the SCT would have the upper hand on small galaxies. 

 

When we are discussion the merits of different designs, we simply can't use the theoretical performance to much at all, as it is how the scope performs under real world conditions that counts. People, and especially commercial telescope designers, tend to forget that. 

 

 

Clear skies!
Thomas, Denmark


  • Erik Bakker likes this

#92 Mitrovarr

Mitrovarr

    Mercury-Atlas

  • -----
  • Posts: 2,873
  • Joined: 12 Sep 2004
  • Loc: Boise, Idaho

Posted 03 January 2018 - 11:46 AM

Does it even make sense to compare like apertures across SCTs and refractors? A 6" SCT is a little bitty telescope easily held in one hand and which can be solidly mounted on a CG-4 or similar. A 6" apo, even a doublet, is a big hulking telescope that requires a mount at least one, probably two classes heavier. The closest SCT in actual weight and bulk would probably be a C11. And the C11 is cheaper, too.
  • sonny.barile, Cpk133 and treadmarks like this

#93 andycknight

andycknight

    Viking 1

  • -----
  • Posts: 692
  • Joined: 13 Aug 2010
  • Loc: UK

Posted 03 January 2018 - 11:48 AM

treadmarks, on 03 Jan 2018 - 4:14 PM, said:

Just as some people don't understand why you'd look at the same objects over and over, I don't understand why you'd get excited about some gray blob that's so dim it could be mistaken for dew on the eyepiece.

I can only answer this for myself and obviously other opinions will differ... and that's a good thing otherwise life would be pretty dull! smile.gif :-

 

One of the most amazing things I have looked at in the night sky, was glimpsing nothing more than a 11th magnitude dot of light under really poor skies. What was amazing to me was not the quality of the image, but rather the understanding that this object was nearly 8 billion light years away.

 

Using nothing more than a tiny 90mm Mak, I was able to glimpse a jet outburst from a black hole that was 'eating' tremendous amounts of matter. I was looking back in time long before the solar system had even formed.

 

I find that exciting... far more than a showpiece object like M42.

 

Regards

 

Andy


  • bbqediguana likes this

#94 Arizona-Ken

Arizona-Ken

    Surveyor 1

  • *****
  • Posts: 1,875
  • Joined: 31 Aug 2008
  • Loc: Scottsdale, Arizona

Posted 03 January 2018 - 11:51 AM

 

 

.... Telescopes don't need hundreds of thousands of objects. All they need is a hand controller that has GPS with M13, M42, and M31 on the handset. I have sold thousands of telescopes. When these people come to my star parties, they're all just looking at the same thing over and over every month. They don't grow and they don't realize there's other wonderful objects outside the Messier catalog that look amazing in all sorts of apertures, even small ones. The Messier catalog is like a crutch for these people. I'd like to remove the Messier objects from the night sky for a few days and see how long they last. They'd be closing shop and heading home for good. I'd say.... Hey! but what about that all those hundreds of thousands of objects in the database you wanted? Don't you want to see those? Naaahhhh I just want to see bright showpieces all night. 

 

As a comment upon this part of Daniel's post, I, too often wonder about people looking at the same objects over and over. In my case, I have some observing goals, initially the Messiers, then the Herschel 400, now an amalgam of objects culled from various deep sky lists I have acquired. I am just getting started on double stars (only have observed a couple of hundred or so) and the challenge of splitting doubles is really fun. I like goals. It keeps things fresh for me and is always sharpening my observing skills, which include getting to know the limitations of my equipment.

 

I always check a few of my favorite M-objects, as they are my friends, and have observed them enough to use them to rather easily get a read on the observing conditions for the night. I also use the M-objects to check out a new eyepiece, filter, or new scope.

 

Lots of objects up there. Thankfully, I'll never get them all.

 

Arizona Ken

 

This is something I've been thinking about with respect to my own observing strategy. There was an awfully judgmental tone towards people who gravitate towards "showpiece" objects. Maybe some people prefer quality over quantity? Oftentimes when I look at some sparse, dim open cluster or whatever, I get the feeling I'm just looking at a weak, discount M45.

 

That's not to say I don't try to find new objects every night. But I'm looking for a winner. Just as some people don't understand why you'd look at the same objects over and over, I don't understand why you'd get excited about some gray blob that's so dim it could be mistaken for dew on the eyepiece.

 

There are lots of things to see up there, and lots of winners to find. But they can't all be winners.

 

Pssst: Those dim gray blobs are trying to hide from me, but with my superior observing skills and highly fine-tuned equipment, I can find them in their gray blobness! I also keep some tissues handy in case it turns out to just be dew!  lol.gif

 

Actually, I often find myself saying, "Aha, there you are!" It's sorta a game, and I have fun with it. Fun is good.

 

I also enjoy the "winners," some great cluster or galaxy that didn't make the usual popular lists. It is all good to me.

 

Arizona Ken


  • Jon Isaacs, Asbytec, Astrojensen and 1 other like this

#95 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 85,789
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 03 January 2018 - 12:10 PM

That's not to say I don't try to find new objects every night. But I'm looking for a winner. Just as some people don't understand why you'd look at the same objects over and over, I don't understand why you'd get excited about some gray blob that's so dim it could be mistaken for dew on the eyepiece.

 

There are lots of things to see up there, and lots of winners to find. But they can't all be winners.

 

 

It's really a question of attitude.. John Wooden:

 

"Things turn out the best for people who make the best out of how things turn out."

 

In my mind, they're all winners, or maybe I should say, I'm a winner. Faint fuzzies and big and bright.   Both can be exciting and rewarding.  That's the basis of my Class I Amazing Object and Class II Amazing Object categories.  A Class 1 is just amazing to look at, a Class II is amazing that you can see it...

 

There's way more Class II objects than Class I objects but with time, a Class II object reveals itself...

 

jon


  • turtle86, Arizona-Ken, Astrojensen and 1 other like this

#96 Erik Bakker

Erik Bakker

    Cosmos

  • *****
  • Moderators
  • Posts: 8,830
  • Joined: 10 Aug 2006
  • Loc: Netherlands, Europe

Posted 03 January 2018 - 12:19 PM

I think we can define a few helpful performance parameters when comparing scopes:

 

Commonly used:

 

Performance per inch of aperture

Performance per dollar invested

Performance per type of preferred observing

Performance per kilo or lbs

Performance per bulk

 

Also used:

Performance per time required to set up

Performance per time required to reach the scope's full potential

Performance per availability new

Performance per lifespan

Performance per ergonomics 

Performance per consistency of quality

 

And their are many more. All have a different ,meaning and importance to different observers and contribute to user satisfaction, both short term and long term.

 

That's why I encourage people to get to know scopes, their differences and their strong points and choose accordingly for a good personal fit.


  • Jon Isaacs, Astrojensen and sonny.barile like this

#97 Gofr

Gofr

    Viking 1

  • -----
  • Posts: 531
  • Joined: 01 Aug 2016
  • Loc: Canada

Posted 03 January 2018 - 12:25 PM

I feel like my C9 gives pretty solid pin point stars much of the time. First thing I did when I got it was collimate the heck out of it. (I bought it off the used market; a mid to late 2000's final production run of USA made C9s before production moved to China.)

While I'm not sure the collimation is perfect, it's as dead on as I can possibly get it via star test. I am trying to get more into the world of double stars and my recent discovery, carbon stars. There really are things beyond the messiers ( which I've yet to really do also since most are not visible from my location).

My other big thing is planets. I really love the planets. I will admit my C9's experience with them has been mushier than my 90mm achro, but there's also no denying the greater detail and brighter image the C9 gives of the planets despite being softer. I saw my very first jovian transit across Jupiter in my C9 not long after I got it. It was amazing!!

My overall point really is, while I agree that my C9 is soft at the higher mags, at lower and mid range mags, I have found it just about as sharp as my 90mm refractor, meaning that when I'm looking at those doubles and carbon stars, my C9 is putting on a wonderful show. Maybe because I took the time to really dial in the collimation as best I could, I don't know. All I know is, I don't feel like I'm getting less from it than what another comparable scope would give.

Of course I have never looked through an apo of any kind, so could just be ignorance on my part. As I said, I concede that my 90mm achro can at times be more pleasing to look through and also be easier to focus (snap in focus vs. mushy focus of the C9), but I bought the C9 to maximize my aperture so I can have greater light grasp, greater resolution, and greater exit pupils while still keeping it on my Exos 2 mount, and by golly does it ever deliver in all 3 of those departments. The improved ergonomics was also an extra unforeseen bonus that I apprecited so much that that was part of the reason I later picked up my 5 inch mak. The trade off is some mushiness in the view (at much higher mags only) and focus. I can live with that.

I just only wish I can get a chance to see how my 5 inch mak fits into all this. Despite having it since August, I have not really had any opportunities to get out with it yet and probably won't until this crazy cold snap goes away.

Edited by Gofr, 03 January 2018 - 12:52 PM.

  • sonny.barile likes this

#98 Erik Bakker

Erik Bakker

    Cosmos

  • *****
  • Moderators
  • Posts: 8,830
  • Joined: 10 Aug 2006
  • Loc: Netherlands, Europe

Posted 03 January 2018 - 01:10 PM

Hope you'll get some cooperative weather soon that will allow you to enjoy your new 5" Mak. 


  • Jon Isaacs and Asbytec like this

#99 yellobeard

yellobeard

    Ranger 4

  • *****
  • Posts: 307
  • Joined: 11 Sep 2013
  • Loc: Netherlands

Posted 03 January 2018 - 01:38 PM


The is no such thing as "never". If properly made with high quality optics, and then properly collimated, an 8 inch SCT will beat a 6 inch APO all the time in similar atmospheric conditions.



Unless of course you believe the physics of optics are incorrect.

In my experience (visual observing), this is simply not true, if we are talking about bog standard, run-of-the-mill 8" SCT's, no matter how excellent their optics are. The 6" refractor (it doesn't have to be an apochromat) will be FAR less sensitive to thermal issues than the 8" SCT and so under many observing

Thomas, Denmark
Uhh ... And that is the most important thing where you're totally wrong!!

New insights on managing the temperature problems in 'thermally difficult' telescopes gave us methods to insulate the telescopes in such way, that even a 16" SCT performes at its best only some 10 minutes after put outside from a much higher room temperature!

So thermal issues are no reason anymore to place an APO refractor above a super high quality SCT.

It is possible that the new insights did not yet reach everybody here. In my country however, lots of people already know that those insights have greatly improved the stability feeling working with reflectors, especially SCT's!

Edited by yellobeard, 03 January 2018 - 01:41 PM.

  • sonny.barile likes this

#100 Mitrovarr

Mitrovarr

    Mercury-Atlas

  • -----
  • Posts: 2,873
  • Joined: 12 Sep 2004
  • Loc: Boise, Idaho

Posted 03 January 2018 - 01:41 PM

Maybe that's true in theory (or with highly optimized scopes unavailable to the general public) but reflectors/SCTs that normal people can actually get do have more thermal problems than refractors.
  • Joe Bergeron and Astrojensen like this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics