Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
Get a Cloudy Nights T-Shirt Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green GuÖ uh, User

Equipment Discussions >> Cats & Casses

Pages: 1 | 2 | 3 | 4 | 5 | 6 | (show all)
Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: My First SCT new [Re: t.r.]
      #5667005 - 02/07/13 12:28 PM

t.r.,

Quote:

I haven't binoviewed with mine yet, and EdZ points out there may be some issues.




Yes, I've read many posts by EdZ warning about induced SA and reduction of clear aperture caused by binoviewing Cats, specifically the C6. It makes sense to me, but EdZ is somewhat of a spoiler.

I was thinking about binoviewing with the C6, but at this point I've accepted the idea that it is more trouble than it's worth. There may be solutions that can allow BVing the C6 with minimal increase in SA and decrease in CA. On the other hand, those solutions would cost beaucoup d'argent. Not very cost effective for a $400 telescope.

I'm resigned to allowing the C6 to do what it does best. It is a great grab-n-go Cat for Moon, planets, doubles, and bright DSO. Having to bring along a binoviewer and multiple pairs of eyepieces acts against the idea of minimalist grab-n-go and apparently also diminishes the optical performance of the C6. Not too good. A lose-lose situation.

Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
t.r.
Post Laureate
*****

Reged: 02/14/08

Loc: Upstate NY
Re: My First SCT new [Re: Sarkikos]
      #5667221 - 02/07/13 02:45 PM

I agree...plop in the Baader zoom and your set for the night.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: My First SCT new [Re: t.r.]
      #5667478 - 02/07/13 04:58 PM

Yes, the Baader Zoom 8-24mm with the Ultrascopic 35mm for low power.

Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
rguasto
scholastic sledgehammer
*****

Reged: 11/18/10

Loc: Long Island, NY
Re: My First SCT new [Re: Sarkikos]
      #5668685 - 02/08/13 10:45 AM

I binoview with my C6 every time I use it. You're all out of your minds with this loss of aperture stuff. It still works and gives great views. Do what you want, but not using a binoviewer because someone figured on paper that you lose aperture with a long accessory optical path is just plain foolish. No offense - I do appreciate the technical objective here, but in practical terms I don't find it significant. So a C6 is really only roughly a C5.5 with a visual back, 1.25 diagonal and a Denk binoviewer. Yeah? I don't get it. Huge placebo effect here.
-Rob

Edited by rguasto (02/08/13 01:41 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: My First SCT new [Re: rguasto]
      #5668753 - 02/08/13 11:15 AM

For deep sky objects, I only monoview. I'm used to looking for objects toward the LM of my 10" Dob at dark sites. I don't want to do anything that might dim the image. So I've never made a big effort to bring out the binoviewer and eyepiece pairs for anything but the planets and the Moon.

However, for the Moon and planets I'm trying to see as much detail as possible in whatever telescope I'm using at the time. A reduction in aperture will reduce resolution, and that will in turn reduce the level of detail and perceived contrast in the image. A C6 binoviewed will be running at a reduced aperture.

From what I've gathered reading threads here on CN, my current setup that I have available for 2" visual back, 2" diagonal and Burgess Binoviewer will probably reduce the effective aperture of the C6 to 5". (I want to avoid a 1.25" VB and diagonal for fear that it would not be able to securely support a binoviewer.) That will not only decrease the aperture by an appreciable amount but also increase the effective central obstruction, not a good thing - especially when observing planets - for a scope that already has 37% CO.

And all this is not even touching on the spherical aberration induced by an accessory train that is much longer than that originally engineered for the C6.

Besides, I intended my C6 as a grab-n-go scope. Bringing out and setting up a binoviewer would lessen ease-of-use and light-weight that I look for in a grab-n-go setup.

If anyone else wants to binoview a C6, they're more than welcome to do it. But for me now, it's not on my top list of things to try.

Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
KerryR
Carpal Tunnel
*****

Reged: 12/05/07

Loc: SW Michigan
Re: My First SCT new [Re: rguasto]
      #5668825 - 02/08/13 11:50 AM

Quote:

...Do what you want, but not using a binoviewer because someone figured on paper that you lose aperture with a long accessory optical path is just plain stupid. No offense - I do appreciate the technical objective here...




The words "stupid" and "no offense" are not a very effective combination.

Tracing the rays of an optical path, finding vignetting therein and choosing to avoid it are the actions of the un-intelligent? I appreciate the hyperbole, but the statement suggests that those of us who appreciate factual information and choose to act on it are less intelligent than those who ignore it.

Facts aside, there's no reason not to do whatever one wants-- this is, after all, an aesthetic pursuit.


Post Extras: Print Post   Remind Me!   Notify Moderator  
aa6ww
scholastic sledgehammer
*****

Reged: 10/23/11

Loc: Sacramento, Calif.
Re: My First SCT new [Re: rguasto]
      #5668871 - 02/08/13 12:13 PM

Quote:

I binoview with my C6 every time I use it. You're all out of your minds with this loss of aperture stuff. It still works and gives great views. Do what you want, but not using a binoviewer because someone figured on paper that you lose aperture with a long accessory optical path is just plain stupid. No offense - I do appreciate the technical objective here, but in practical terms I don't find it significant. So a C6 is really only roughly a C5.5 with a visual back, 1.25 diagonal and a Denk binoviewer. Yeah? I don't get it. Huge placebo effect here.
-Rob





Aren't these forms funny! You can tell who doesn't have a clue what they are talking about by reading in these forums. I find it best to just let them say what they want and just die laughing at how stupid it can snowball out here. The worse absolute worse ones are the ones who try to use mathematics to justify something, once I see that, its a dead ringer that person is completely clueless as to what hes not only saying, but doing. Its like that everywhere though, just chalk it up to entertainment and wait for night time. Show me an astronomer whos had the same scope for half a dozzen years and thats the guy who knows what hes talking about, then its just experience talking, not bs. Usually he owns a big old newt or a beat up cassagrain no one would be seen dead with, and almost always without electronics guiding his scope, and thats the one worth listening to and talking to, about whats in the sky, not what hes looking through. Back on the binoviewer, the real value with them is how much more contras they add to what your looking at. Two cheap orion plossls in a quality binoviewer will give you much more contras on whatever your looking at, than a whole room full of single eyepiece Ethos, every time, on any object. Amazing how much more you can see with two eyes vs one.

.... Ralph


Post Extras: Print Post   Remind Me!   Notify Moderator  
Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: My First SCT new [Re: aa6ww]
      #5668943 - 02/08/13 12:43 PM

I often binoview with my 8" and 10" Dobs. My Burgess Binoviewer model 125C has about a 20mm clear aperture. As long as I do not binoview with eyepieces which have field stops wider than about 23mm, I shouldn't have to be concerned about vignetting. These are facts.

The C6 has a clear aperture of 27mm. If I introduce a long accessory train behind the C6, there will not only be vignetting, reducing the effective aperture of the telescope, but also induced spherical aberration. These are facts.

Now whether or not vignetting, reduced aperture or spherical aberration matter or not to the observer - or whether or not the observer will even notice them - is something else entirely. But that has nothing to do with the fact that there is vignetting, reduced aperture or spherical aberration.

Personally, I don't have a great love of mathematics. I will avoid it whenever possible. But I know that a combination of mathematics and hands-on experience will get you closer to the truth than anything else.


Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
KerryR
Carpal Tunnel
*****

Reged: 12/05/07

Loc: SW Michigan
Re: My First SCT new [Re: Sarkikos]
      #5668951 - 02/08/13 12:46 PM

Quote:

...But I know that I combination of mathematics and hands-on experience will get you closer to the truth than anything else.


Mike




Well said.


Post Extras: Print Post   Remind Me!   Notify Moderator  
KerryR
Carpal Tunnel
*****

Reged: 12/05/07

Loc: SW Michigan
Re: My First SCT new [Re: aa6ww]
      #5668992 - 02/08/13 01:09 PM

Quote:

...
The worse absolute worse ones are the ones who try to use mathematics to justify something, once I see that, its a dead ringer that person is completely clueless as to what hes not only saying, but doing.
...

.... Ralph




Folks who use and understand physics are essentially full of doo-doo?

This relegates most of the ATM forum, not to mention the folks who design the systems we all use, to the trash heap-- opticians, amateur or otherwise, find math and raytracing extraordinarily useful. Most have looked through a scope or 2, as well. Not saying the opticians bat 1000, the HST being an example that comes to mind readily, but, more often than not, the math works pretty darn well, even if I don't understand it, or my eye-brain doesn't want to agree.


Post Extras: Print Post   Remind Me!   Notify Moderator  
BigC
Carpal Tunnel
*****

Reged: 09/29/10

Loc: SE Indiana
Re: My First SCT new [Re: aa6ww]
      #5669060 - 02/08/13 01:36 PM

Ralph,

Your post is a real eye-opener.

Just remember that opinion doesn't always equal fact.

And what works best for you may not be best for someone else.

Binoviwers are one of my options every time I observe.


Post Extras: Print Post   Remind Me!   Notify Moderator  
rguasto
scholastic sledgehammer
*****

Reged: 11/18/10

Loc: Long Island, NY
Re: My First SCT new [Re: KerryR]
      #5669078 - 02/08/13 01:40 PM

oh... didn't mean to ruin this thread. Maybe shouldn't have used the word "stupid" and it wasn't meant in a derogatory manner. I couldn't find a more appropriate term. I cannot detect any increase in SA and the images are full of detail as are typical of a binoviewer in any telescope. I only binoview planets (and the moon, but not a big fan of lunar) I can say that the images in the C6 compare very favorably to my 8" F8 newt with an 18% CO. The newt is obviously brighter and produces a much sharper/detailed image. IMO binoviewed planetary images are more detailed than in mono with a C6. Try it, you'll like it.
-Rob


Post Extras: Print Post   Remind Me!   Notify Moderator  
aa6ww
scholastic sledgehammer
*****

Reged: 10/23/11

Loc: Sacramento, Calif.
Re: My First SCT new [Re: BigC]
      #5669128 - 02/08/13 01:59 PM

Quote:

Ralph,

Your post is a real eye-opener.

Just remember that opinion doesn't always equal fact.

And what works best for you may not be best for someone else.

Binoviwers are one of my options every time I observe.





I use them on 5/5 seeing conditions when I want to get the absolute best views possible when using my C14 when watching solar system events or during solar observing. The contras advantage with my solarmax 90 during this solar maximus is scary. Filiments you cant even see with one eye, looks like snakes crawling along the solar surface with a binoviewer. Then again, thats for a whole different forum to discuss.
This C6 subject has sparked my interest in my little C6 again. Here in Calif we are showing clear all weekend. Im planning to "pimp out" my little orange tube C6 tonight with my 2" accessories and see how many NGC objects I can bag with it. I hope more out here are having clear skies also this weekend, since its a new moon weekend. Good luck to those getting out with their gear tonight.
Once Im set up later, I think I'll take some photos of my C6 and start a new photo thread on the C6. These are great little.scopes optically the deserve way more.respect than they get.

.....Ralph


Post Extras: Print Post   Remind Me!   Notify Moderator  
BigC
Carpal Tunnel
*****

Reged: 09/29/10

Loc: SE Indiana
Re: My First SCT new [Re: aa6ww]
      #5669289 - 02/08/13 03:37 PM

Unless using binoviewers lower the image brightness "over the cliff" I would expect a signicant improvement in detail seen.In everday life my binocular vision allows depth perception and detail is lessened if I close even my weaker eye!The more raw information we can give the brain evidently the better picture it will present.

Denkmeiers are not in my budget;Williams Optics binos have to suffice.

Remember,it IS all in your head!

Should another Z12 OTA find its way here, I fully intend building a JMI clone variant.Guess I could build a smaller version first using a couple smaller tubes.Won't be all the fancy motors ,just adjustable with threaded rods or screws or something.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Stephen Strum
member


Reged: 04/18/09

Loc: Tulsa, OK
Re: My First SCT new [Re: Sarkikos]
      #5669400 - 02/08/13 04:48 PM

Per one of these loss of aperture threads I decided to try and improve my binoviewer setup for use with my C5. I've ordered an adapter from Precise Parts: http://www.preciseparts.com/ppmain/adapter.html
that will allow me to screw my denk IIs (with power switch) directly to the body of a 1.25" astro-tech diagonal (what I normally use on the C5). They didn't have that diagonal in their database, so I sent them the eyepiece holder portion of the diagonal so they could add it to their database and I could place my order. This alone will save about 30 mm of light path. Additionally, I cut off another 5+ mm off the 1.25" visual back using a rotary tool. I cut off part of the threaded portion on the end of the visual back which I didn't need. So, the combination of the two modifications will now result in only a very minor aperture reduction using the power switch when in the straight through mode (no reducer or barlow lens slid in), and should give just about full aperture if I don't use the power switch based on my understanding of loss of aperture beginning once the light path past the back of the scope exceeds 200 mm. The total cost, with shipping of the adapter was $94. The adapter won't allow me to rotate the binoviewers, but since I use my SCTs on alt-az amounts, that isn't a concern for me.

While using the 1.25" diagonal with the denk IIs and power switch might look a bit scary, I've never had a problem. On the other hand, I've had the body of my 2" SCT diagonal spin upside down with my binoviewers in them (it decided to partially unthread itself). Luckily my binoviewers didnít fall out and crash to the patio.

Steve


Post Extras: Print Post   Remind Me!   Notify Moderator  
aa6ww
scholastic sledgehammer
*****

Reged: 10/23/11

Loc: Sacramento, Calif.
Re: My First SCT new [Re: Sarkikos]
      #5669485 - 02/08/13 05:40 PM

Quote:

I often binoview with my 8" and 10" Dobs. My Burgess Binoviewer model 125C has about a 20mm clear aperture. As long as I do not binoview with eyepieces which have field stops wider than about 23mm, I shouldn't have to be concerned about vignetting. These are facts.

The C6 has a clear aperture of 27mm. If I introduce a long accessory train behind the C6, there will not only be vignetting, reducing the effective aperture of the telescope, but also induced spherical aberration. These are facts.

Now whether or not vignetting, reduced aperture or spherical aberration matter or not to the observer - or whether or not the observer will even notice them - is something else entirely. But that has nothing to do with the fact that there is vignetting, reduced aperture or spherical aberration.

Personally, I don't have a great love of mathematics. I will avoid it whenever possible. But I know that a combination of mathematics and hands-on experience will get you closer to the truth than anything else.


Mike




Sometimes you just gotta be an outlaw and live on the edge, and push those fields of views over the edge and vignette a little to see what its like. Its an exhilarating experience knowing your breaking the laws of physics and mathematics, just to see whats over that barrier.
Kinda like star hoping to an object you cant see with your naked eye, but you know its there, even with a street light shining in your face. It still works, and the experience can leave you breathless. These ARE facts also!!!

....Ralph


Post Extras: Print Post   Remind Me!   Notify Moderator  
Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: My First SCT new [Re: aa6ww]
      #5669504 - 02/08/13 05:51 PM

Maybe you just didn't notice it.

In any case, SA would be introduced by the extended length of the accessory train in a Cat. It has nothing to do with the clear aperture of the binoviewer.

Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: My First SCT new [Re: Sarkikos]
      #5669743 - 02/08/13 08:45 PM

I can appreciate not letting the numbers and so on create unfounded biases and such but all the same it's good to that've the facts regardless.
What's truly testament here us the success of the bino view on contrast despite the apparent aperture reduction.

Pete


Post Extras: Print Post   Remind Me!   Notify Moderator  
Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: My First SCT new [Re: azure1961p]
      #5673622 - 02/11/13 08:33 AM

It makes sense to me that an SCT has only a finite range for length of the accessory train before spherical aberration is introduced into the system. The primary mirror has a spherical figure and must have native spherical aberration. The corrector plate is designed to correct the spherical aberration from the primary. There must be an optimum focal setting for this correction. If the eyepiece is set too far back from that optimum setting, spherical aberration will be induced. Spherical aberration prevents sharp focus of the image. Lack of sharp focus will prevent the observer from seeing finer detail.

True, binoviewing can increase perceived contrast for images. That's why I binoview planets and the Moon through my Dobs. But extending the accessory train in Dobs will not induce spherical aberration. I need an OCA to come to focus, but there is no induced SA.

Depending on how much the length of the accessory train is increased in an SCT through binoviewing, the improvement in perceived contrast could be overwhelmed by the increase in spherical aberration. For planet and lunar observation, where discernment of fine detail is all important - at least in my view - I would want to avoid spherical aberration. I think I'd rather improve contrast through other means, such as filters, baffling, closer collimation or better eyepieces.

The tradeoff for deep sky observation through SCTs might be in favor of binoviewing - at least for the brighter DSO - because an increase in perceived contrast would be helpful, while sharpness of image is often not as important as in planet/lunar observation. But I don't binoview deep sky, only planet/lunar, so I don't see that binoviewing my C6 would be beneficial for me. I don't want to do anything that would diminish image sharpness when I observe planets or the Moon.

And all this doesn't even touch on the decrease in clear aperture and increase in central obstruction ratio due to extending the length of the accessory train through binoviewing. These factors will also rob the optical system of much needed contrast and resolving power when viewing planets and the Moon.

Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
aa6ww
scholastic sledgehammer
*****

Reged: 10/23/11

Loc: Sacramento, Calif.
Re: My First SCT new [Re: Sarkikos]
      #5680531 - 02/15/13 01:15 AM

You should probably read up on what a corrector plate does, which all SCT's have. You'd probably stop talking about spherical aberration regarding SCT's which your newts have, which SCT's design out of with their front correctors.

..kinda funny!!

...Ralph


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | 5 | 6 | (show all)


Extra information
13 registered and 19 anonymous users are browsing this forum.

Moderator:  Starman27, kkokkolis 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 4438

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics