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What do people see in Schmidt-Cassegrains?

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#51 John J

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Posted 03 October 2014 - 02:30 PM

SCT....Dosen't that stand for Seriously Compromised Telescope? Corrector plate is a Dew / Frost magnet. Mirror shift. Wrapping paper tube views. Long cool down times. "Schmidt Ghosts" on bright objects when imaging. Difficult to clean when dirty ( on the inside). They still have optical anomolies unless you pay for the ACF or Edge options then they get way expensive. The cost to fix the above mentioned stuff? The only thing I see is they are compact up to about 10" after that it's like toting a Keg of beer around (not as much fun as the beer though). I've never owned one (and never will) as I watched enough of my friends deal with theirs and their problems.

 

JJ



#52 Atjous

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Posted 03 October 2014 - 03:39 PM

SCT....Dosen't that stand for Seriously Compromised Telescope?

No, it does not. To me, it stands for hours and hours and hours of astro-fun. Fun, like enjoyment. A great hobby. Watching the Great Deep, with your own equipment. Is it all perfect? Hell no. I do not aim for that. I aim for serious FUN.

 

Yes, at times, those hours can be reduced to minutes. True, dew can be a problem. Ah well, in that case I had great minutes of FUN. I deal with that. It is what it is.


Edited by Atjous, 03 October 2014 - 03:43 PM.


#53 dpippel

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Posted 03 October 2014 - 05:05 PM

SCT....Dosen't that stand for Seriously Compromised Telescope? Corrector plate is a Dew / Frost magnet. Mirror shift. Wrapping paper tube views. Long cool down times. "Schmidt Ghosts" on bright objects when imaging. Difficult to clean when dirty ( on the inside). They still have optical anomolies unless you pay for the ACF or Edge options then they get way expensive. The cost to fix the above mentioned stuff? The only thing I see is they are compact up to about 10" after that it's like toting a Keg of beer around (not as much fun as the beer though). I've never owned one (and never will) as I watched enough of my friends deal with theirs and their problems.

 

JJ

 

You've never owned one, yet you feel qualified to write them off because of what you've seen others "deal with"? OK.

 

I've owned SCTs, Newts, and refractors. They ALL have issues and optical anomalies and they're ALL great designs in the their own way. You want perfection? You're gonna pay out the nose for getting as close as you can no matter which type of scope you buy.



#54 rmollise

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Posted 03 October 2014 - 05:06 PM

SCT....Dosen't that stand for Seriously Compromised Telescope? Corrector plate is a Dew / Frost magnet. Mirror shift. Wrapping paper tube views. Long cool down times. "Schmidt Ghosts" on bright objects when imaging. Difficult to clean when dirty ( on the inside). They still have optical anomolies unless you pay for the ACF or Edge options then they get way expensive. The cost to fix the above mentioned stuff? The only thing I see is they are compact up to about 10" after that it's like toting a Keg of beer around (not as much fun as the beer though). I've never owned one (and never will) as I watched enough of my friends deal with theirs and their problems.

 

JJ

 

Let's see...

 

Nobody told you about dew heaters and dew shields? Like on REFRACTORS? ;)

 

A ghost is a supernatural entity with no basis in reality. :eyecrazy:  

 

My 1973 C8 still doesn't need that dreaded INSIDE CLEANING. But the last time I needed to clean a student SCT, it took all of ten minutes from starting to remove the corrector to buttoning it up. :yay:

 

All telescopes have optical anomalies. An SCT has a slightly curved field an coma equivalent to an f/6 Newtonian. An inexpensive reducer corrector will clean it up a lot without the need for a fancier design. :whee:

 

That about cover it? :lol: :jedi:



#55 jgraham

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Posted 03 October 2014 - 05:26 PM

Wow, it really makes me wonder if some of the contributors to this thread have ever used an SCT. It is awful to read such half-truths, hearsay, and outright fabrications as gospel truth.

 

The first thing I do with a new SCT is to make a dew shield. (Yes, I wish that they were standard equipment, but they are easy to make.)

 

I have never had to clean the inside of an SCT, though I have had some major spider webs in my Newtonians until I started bagging them.

 

Cool down time is rarely a problem, I just set my scope out early. If I'm in a hurry I use a small camp fan or Lymax cooler for my big Cats. My big Newtonians need a fan as well.

 

I've never seen a ghost visually or in an image taken with my SCTs. I have seen them on images taken of very bright stars in my SNs.

 

Mirror shift can be significant in my older Cats, but easily managed. For precision work I use an external Crawford focuser.

 

In 52 years I've never had to have an SCT 'fixed'.

 

It is wondeful that people find gear that they enjoy. Please consider extending that courtesy to others.



#56 ur7x

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Posted 03 October 2014 - 05:52 PM

I own one of each of the common telescope formats: My SCT, for a whole raft of reasons, is by far my favorite and gets the most use...

 

This thread is now encroaching on Poe's Law.  I can no longer tell if people are posting facts, opinions, humor or sarcasm.



#57 Bomber Bob

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Posted 03 October 2014 - 08:28 PM

Scope purchases / use equate to preferences, capabilities, and costs.  Please note that those are variables, not fixed constants, made even more so as manufacturers offer more types and models.  Not a complaint, just an observation.  I approach this hobby the same way I do music:  I'm less concerned about the genre than I am the artistry.  I'm a die-hard Refractor Dude, but if I could get a C-14 for $500, it'd be in my Man Cave ASAP.



#58 David Pavlich

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Posted 03 October 2014 - 09:45 PM

You know, I'm really happy that none of us are forced to buy an SC.  I'd hate to see members jumping off bridges because they were forced to buy a lousy telescope. :ohmy:

 

David



#59 Bruce FitzGerald

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Posted 03 October 2014 - 09:48 PM

Something that I have wondered about for quite a while - why are Schmidt-Cassegrains so popular?

 

 

So what gives?

Try taking a photo of this Caldwell object with your Dob or any dob for that matter! Not so easy for a Dob or a newt but very very easy for my C14.

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  • Rosette.jpg

Edited by Bruce FitzGerald, 03 October 2014 - 09:49 PM.


#60 Dakota1

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Posted 03 October 2014 - 09:55 PM

+1 David well stated

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

Bill



#61 A6Q6

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Posted 03 October 2014 - 10:08 PM

The only thing I see is they are compact up to about 10" after that it's like toting a Keg of beer around (not as much fun as the beer though). I've never owned one (and never will) as I watched enough of my friends deal with theirs and their problems.
 
JJ

Never say never, I spent over 35yrs not thinking much about SCTs because of my limited experience with them and then I found a Classic Orange tube C5 at a pawn shop. Here is a 5" f/10 scope, smaller than an Astroscan. It has a fork mount with clock drive, Manual Control knobs for right ascension and declination, setting circles and the optics in a coffee can size tube. It has very good optics and no Mirror shift! For grab and go I couldn't be happier. There are some realy good ones out there. I can take it out in one trip. My little C5 is the kind of scope that makes me think I would like the beer keg size C11 or C14.

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Edited by A6Q6, 04 October 2014 - 09:26 AM.


#62 Asbytec

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Posted 03 October 2014 - 10:16 PM

Upper:  DOB

Lower:  SCT

 

Contest over.

:lol:

 

 

...John

 

Okay, that was humorous and the point made nicely. :)

 

I am not sure however, how portable in set up and tear down the imaging equipment, focal reducers, cables, power, a table, and maybe a lap top is. Then there is polar alignment, maybe drift alignment, slewing, calibrating, maybe auto guiding, and just about everything else required to get that shot.

 

If I'm dating myself on imaging in the late 90's, I should be ridiculed for not having kept up. But, back then, it was quite a chore...the scope could easily cold down during set up time alone. Add to that winding all those cords, especially the long power cord, around your elbow took a lot of time to tear down and pack up in the wee hours.

 

These says, I don't even bother with GOTO. Keep it simple with a GEM mounted CAT. Plop and drop. It's amazing how quickly it's ready to go. A half hour under an ice pack and the scope is cooled to initial ambient. Soooo much easier, almost grab and go.



#63 dotnet

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Posted 04 October 2014 - 04:27 AM

This thread is now encroaching on Poe's Law.  I can no longer tell if people are posting facts, opinions, humor or sarcasm.

 

I don't know about others, but I try to cover all four of these categories in each and every one of my posts  :grin:

 

Cheers

Steffen.



#64 George Methvin

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Posted 04 October 2014 - 06:22 AM

How funny that over the years folks fall for the same old thing which scope is better we can not stay away from it like a moth to a light. Come on folks I have never owned a bad scope even the one or two that the optic were not so good. Refractor, reflectors and SCT have all given me lots of enjoyment lol I am so spoiled and have come such a long ways from my first 60mm Tasco refractor. I have been up all night to night viewing through all my scope out in my drive way it looks like a star party lol I guess it is. The views through all the scopes tonight large or small no matter what make or model are giving me great views, tonight no one scope was better then the other just each  view was a little diffract but all the views were good views. So I am on my 6th cup of coffee and Jupture is high enough for viewing so I am heading back outside to take a look.  My oh my which scope will I use so many choices lol like I said I am so spoiled and have come such a long ways from those early years viewing through that little 60mm refractor which bye the way give me many hours of enjoyment. Clear skies my friends.

 

Zhumell 12 dob

Meade 10 SCT

AWB 130mm reflector

Orion EON 120mm ed refactor

 




Edited by George Methvin, 04 October 2014 - 06:53 AM.


#65 ur7x

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Posted 04 October 2014 - 09:08 AM

 

 

If I'm dating myself on imaging in the late 90's, I should be ridiculed for not having kept up. But, back then, it was quite a chore...the scope could easily cold down during set up time alone. Add to that winding all those cords, especially the long power cord, around your elbow took a lot of time to tear down and pack up in the wee hours.

 

These says, I don't even bother with GOTO. Keep it simple with a GEM mounted CAT. Plop and drop. It's amazing how quickly it's ready to go. A half hour under an ice pack and the scope is cooled to initial ambient. Soooo much easier, almost grab and go.

 

 

I'm not going to point out that you aren't keeping up.  But during the summer I can literally have my imaging system, set up and up and running in 3 minutes. And about 2 of those are the time it takes the old XP laptop to boot.  Flip the power switch, wake the mount up from hibernation, attach the Canon Camera to the T-ring, focus on a bright star a mouse click (or three) on TheSkyX and I'm good too go.

 

In the winter (when I don't leave the scope on the pier), it take about 5 minutes, but most of that is doing the ASPA and the 2+4 alignment to the stars.  Which I like to do at dusk so as to let the twilight highlight the brightest stars.  I go in, eat dinner and when it is nice and dark the scope is ready to go

 

Not that it is a race, but I almost always have my GEM and SCT up and running faster than most DOBs at star parties I attend. Tripod, head, OTA, HC, power, one cord. Easy.  If I create images at a star party they are short 60-90 second unguided efforts with an IR remote for the camera. Simple, fast, no extra wires.

 

For me, every time I look at (or though) a big DOB I'm left with the feeling, what a nice scope, if there was only some way to put it on an equatorial mount. so we could capture some of those awesome views :undecided:

 

As someone who has been apart of (on and off and on ) this hobby since the early 70's.  It took me years of pain, expense and frustration to discover the best telescope tends to be not the largest aperture, but tends to be the one on the best mount.  That is where the compact size of the SCT really shines. It helps the mount work better, since it is easier to balance, puts lower torque loads on the mount and is less of a wind sail.



#66 Sarkikos

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Posted 04 October 2014 - 09:16 AM

For me, every time I look at (or though) a big DOB I'm left with the feeling, what a nice scope, if there was only some way to put it on an equatorial mount. so we could capture some of those awesome views :undecided:

 

That's funny ... I've always looked for ways to get all my scopes OFF the equatorial mounts!  Anybody want to buy a GEM?

 

But then I'm strictly visual.  Mark Twain said, "Golf is a good walk ruined."  I agree with that.  But I'll do Twain one better.  "AP is a good view ruined."

 

:grin:

Mike


Edited by Sarkikos, 04 October 2014 - 09:18 AM.


#67 George Methvin

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Posted 04 October 2014 - 10:33 AM

LOL now its on to AP, like I have said before I really like my sct its really a fine scope.  But I don,t do AP and I don't need goto and most times don't use a drive. With that said I still like the views through my sct and I still use it just not as much as my 12 dob. Makes sense why use the sct if you are not doing AP or using goto or the drive so what you have left when you take that all away is a 10 sct dob lol.

If that's the case then may as well use the 12 dob it show a little more then the 10 sct. Now on there other hand if I do want to use a drive or goto then I pull out the sct, different tools for different jobs. Like when I want those nice wide field view that the SCT or Dob can't always give I pull out my 120 ed refactor. Plus a big factor in choosing a SCT and maybe the most imported is that they just look so dam cool, so high tech and all that glass and glossy painted tube and all the lights and switch's lol what's not to like.  I know that when I stand next to mine it makes me look smarter plus better looking to lol.


Edited by George Methvin, 04 October 2014 - 10:46 AM.


#68 dpippel

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Posted 04 October 2014 - 10:35 AM

Nothing wrong with a good GEM for visual. I use one all the time and love it. In fact I fail to see what all of the complaints are about. It breaks down into easy-to-handle pieces for storage and transport. From unpacking it to having it aligned and ready to observe literally takes me 10-15 minutes. Personally I find it more convenient to use than most fork mounts, but maybe that's just me. ;)



#69 tim53

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Posted 04 October 2014 - 11:28 AM

Reflectors are good but they lack the quality tracking that a SCT, or a refractor has on a equatorial mount.

 

 

I gotta tell you, I cringe every time I hear someone equate "reflector" with "Dobsonian" as if they're one in the same.  A Dobsonian is a reflector, but reflectors can be many things, including real Cassegrains without adjective modifiers.

 

So, the statement is completely incorrect, since you can mount a reflector on an equatorial mount with accurate tracking.

 

My 10" f/6 Newtonian is easier to set up, polar align and take down than a 10" SCT (or my Nexstar 925 GPS on the fork mount), by quite a bit, even on the very heavy Tak EM-500 mount I use it on.  I keep the mount on a dolly and roll it in and out of my shop.  But even for use in the field, It comes apart into manageable (but still heavy  ;) ) components.  The tube, I carry with one hand by one of the spreader bars.  I don't own a dob, but I have more reflectors than I know how to count (and none of them are on altazimuth mounts).

 

post-6788-14073816558076_thumb.jpg



#70 dpippel

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Posted 04 October 2014 - 11:48 AM

That is a SWEET scope!



#71 tim53

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Posted 04 October 2014 - 12:32 PM

Thank you!  I made the primary at the Delmarva mirror class in 2010.  Was still figuring up until about an hour before the weekend ended, so Dave Groski (my "instructor"), helped finalize the figure on it.  It's an amazing performer!

 

-Tim.



#72 Glen A W

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Posted 04 October 2014 - 12:38 PM

What is lost as to the popularity of these things is what a design triumph the original Celestron fork-mounted scopes were.  Well into the 80s, this must have been the main selling point - you had a scope with good or great optics, which would fit into a steamer trunk, complete with its mount, and with all the accessories needed for anything you could do at that time.  You could have a long focal length, or short with the reducer.  This scope was, as a said, a triumph of design.

 

Now, the tube has been let go from that original fork mount, for better or for worse.  The Chinese Celestron scopes I have used on the modern alt-az fork were pretty cheap, with very coarse focusers.  SCTs do great on German mounts but then it is not so portable as that original design.

 

I hope sometime to find one of the old ones again (my last was a 1987 plain fork mounted one) because I could carry that 8" scope outside in one piece and be observing instantly (temps allowing) and that is no small advantage.  The old ones were all-metal and had a real quality about them.

 

Properly collimated, the scope is sharp and it's basically color free so if you get a really good one you are into a fine instrument.

 

Glen


Edited by Glen A W, 04 October 2014 - 12:43 PM.


#73 rmollise

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Posted 04 October 2014 - 12:51 PM

I'd say the original poster's purpose has been fulfilled. :lol:

 

Why people are so emotionally bound to convert people to their case for and against I will never understand.

 

If you like SCTs, continue using them happily.

 

If you don't like 'em, don't use 'em.

 

:lol:



#74 Gil V

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Posted 04 October 2014 - 01:03 PM

I think this question was provocative, but what the heck.

The observing experience with a SCT is second to none in terms of comfort. Star hopping is a breeze, and the views (especially at high power) can only be surpassed by a refractor, which are prohibitively expensive at the same aperture.

A good Newtonian on a GEM with rotating tube rings might provide larger aperture with similar comfort, but setup and breakdown have to be considered more difficult for that scope.

Adaptability to DSC's provides strong upgrade ability to any SCT.

Finally, the exit pupil makes good viewing with average eyepieces a reality, lowering the overall cost of ownership.

No-brainer from my perspective.

PS - my .98 poster board and shoelace dew shield is in it's third year of use.

Edited by Gil V, 04 October 2014 - 01:05 PM.


#75 tim53

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Posted 04 October 2014 - 01:03 PM

Or do like most of us ol' fahrt's do:  By 'em when you find 'em.  Keep the garage full of options!

 

-Tim.




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