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Equipment Discussions >> Cats & Casses

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Vondragonnoggin
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Reged: 02/21/10

Loc: Southern CA, USA
Re: Why do people even buy SCTs??? new [Re: rmollise]
      #6229787 - 12/02/13 05:48 PM

Where's the OP? He threw a ball of catnip into the cats and casses forum and hasn't returned yet. Watching the cats walk around with tape on their feet most likely....



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NHRob
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Reged: 08/27/04

Loc: New Hampshire
Re: Why do people even buy SCTs??? new [Re: Vondragonnoggin]
      #6229804 - 12/02/13 05:53 PM

He's probably scared away.
Likely looking in the reflector and refractor forums now.


Quote:

Where's the OP? He threw a ball of catnip into the cats and casses forum and hasn't returned yet. Watching the cats walk around with tape on their feet most likely....






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kansas skies
sage


Reged: 12/02/12

Loc: Kansas, USA
Re: Why do people even buy SCTs??? new [Re: Eddgie]
      #6229881 - 12/02/13 06:24 PM

Why do people even buy SCTs???

Come on guys, it was the Celestron girls...

Bill


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Doug Culbertson
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Reged: 01/06/05

Re: Why do people even buy SCTs??? new [Re: kansas skies]
      #6229893 - 12/02/13 06:28 PM

Quote:

Why do people even buy SCTs???

Come on guys, it was the Celestron girls...

Bill




That and the Leonard Nimoy ad!


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PowellAstro
scholastic sledgehammer
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Reged: 10/14/09

Loc: Tennessee
Re: Why do people even buy SCTs??? new [Re: Doug Culbertson]
      #6230002 - 12/02/13 07:21 PM

Mirror Flop: I don't know if it's a problem with the retainer ring or they just leave them loose for fear of pinching the optics. I just rebuilt my new C90 and the mirror was so loose, I had the issue with that little thing. I also used masking tape on the baffle slider to take up the slop of the difference in the mirror bore and the size of the slider tube. The alignment is much better as is the image. I did some bumping it around hard and alignment is still dead on.

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TG
Pooh-Bah


Reged: 11/02/06

Loc: Latitude 47
Re: Why do people even buy SCTs??? new [Re: PowellAstro]
      #6230068 - 12/02/13 07:45 PM

Quote:

Mirror Flop: I don't know if it's a problem with the retainer ring or they just leave them loose for fear of pinching the optics. I just rebuilt my new C90 and the mirror was so loose, I had the issue with that little thing.




Somebody at Celestron needs to be told about neoprene gaskets.

Tanveer


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WesC
Carpal Tunnel
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Reged: 02/06/13

Loc: La Crescenta, CA
Re: Why do people even buy SCTs??? new [Re: drago]
      #6230078 - 12/02/13 07:49 PM

Quote:

Quote:



At the speed of light? Really? That's just silly. False logic. It could cross 10,000 times and you would not see any detectable difference. Moving air in a tube is billions of times slower than the speed of light, it will not influence the light more just because its in the tube for a trillionth of a second longer.




hot air speed over a campfire is also lot less speed than a speed of light, but you can see, it changes view throught it very dramatically. turbulence in atmosphere, as so as tube currents also is not faster speed than speed of light, but that also destroy a views. looks like you can have a very big problems with elementar physic understanding...




Nice cheap shot there. You know nothing about me or my level of education. But thanks for taking potshots anyway.

FWIW, you're still incorrect.


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WesC
Carpal Tunnel
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Reged: 02/06/13

Loc: La Crescenta, CA
Re: Why do people even buy SCTs??? new [Re: TG]
      #6230079 - 12/02/13 07:49 PM

Quote:


Somebody at Celestron needs to be told about neoprene gaskets.

Tanveer




And modern lubricants.


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PowellAstro
scholastic sledgehammer
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Reged: 10/14/09

Loc: Tennessee
Re: Why do people even buy SCTs??? new [Re: WesC]
      #6230092 - 12/02/13 07:55 PM

The bad thing is, it's got a 1/32" cardboard washer on the front side and a 1/8" O-ring on the back side under the jam nut. A quarter turn would of been enough to do the job once the nut was touching. The right parts are there, they just didn't use them right...

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rmollise
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Reged: 07/06/07

Re: Why do people even buy SCTs??? new [Re: TG]
      #6230164 - 12/02/13 08:33 PM

Quote:

Quote:

Mirror Flop: I don't know if it's a problem with the retainer ring or they just leave them loose for fear of pinching the optics. I just rebuilt my new C90 and the mirror was so loose, I had the issue with that little thing.




Somebody at Celestron needs to be told about neoprene gaskets.

Tanveer




Mirror flop is not caused by the retainer ring being loose. If it is loose, you will have problems, sure, but that is rare. Mirror flop is the mirror/carrier moving on the baffle.


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PowellAstro
scholastic sledgehammer
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Reged: 10/14/09

Loc: Tennessee
Re: Why do people even buy SCTs??? new [Re: rmollise]
      #6230250 - 12/02/13 09:08 PM

In my C90, it was the ring being loose. The bore in the mirror was about .060" larger than the baffle slider tube. Even with it out in hand, you could turn it and the mirror would go clunk each time. Holding the slider in hand, without it being on the primary baffle, you could just touch the mirror with the other hand and wiggle it back and forth with no effort. Also, in this C90, there was no play between the primary baffle and the slider, even with all the grease washed off and the unit squeaky clean. Proof is, I put the unit back together with only a film of grease from a paper towel. I have no play or flop now. While that may not be the norm, it was the cause 100% in this C90.

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azure1961p
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Reged: 01/17/09

Loc: USA
Re: Why do people even buy SCTs??? new [Re: WesC]
      #6230337 - 12/02/13 09:43 PM

Quote:

Quote:

Quote:



At the speed of light? Really? That's just silly. False logic. It could cross 10,000 times and you would not see any detectable difference. Moving air in a tube is billions of times slower than the speed of light, it will not influence the light more just because its in the tube for a trillionth of a second longer.




hot air speed over a campfire is also lot less speed than a speed of light, but you can see, it changes view throught it very dramatically. turbulence in atmosphere, as so as tube currents also is not faster speed than speed of light, but that also destroy a views. looks like you can have a very big problems with elementar physic understanding...




Nice cheap shot there. You know nothing about me or my level of education. But thanks for taking potshots anyway.

FWIW, you're still incorrect.




I've got to agree with Wesc here it is apparent for the reasons mentioned. It seems infinitesimally minuscule and how after all could such a fine discrepancy be witnessed by and eye/brain but alas light spells it out unmistakably - even exceedingly sensitive at that. I had questions of this sort - and not THAT long ago. At the point of focus (and on either side) its plain as day. I am sympathetic to your questioning it - but once you see how light fleshes out these discrepancies it all makes sense. Even within the extremely short distance of an optical assembly. Doesn't matter. It reveals all.

Pete


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orion61

*****

Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: Why do people even buy SCTs??? new [Re: PowellAstro]
      #6230356 - 12/02/13 09:51 PM

A lot of mirror shift is from the grease being too thick,
Super Lube cut with Synthetic oil, has eliminated mirror shift in about a dozen scopes I have worked on.
ESPECIALLY 7" Meade Maks, & 10" Cats. Meade 12 & up have a Coil Spring that assists focus. Meade scopes seem to suffer more than Celestron
Someone mentioned it but I agree, the belt drive focus of the 127 Maksutov I have is a great example of smooth focus..
I think it is time to say, we like the type of scopes we do for reasons "individual as we are". There isn't a wrong type of scope design (well possibly Jones-Bird)
I stand by my Schmidts because they fit my direction in this hobby, ease of storage, transportation,optical quality and purchase price.,
IF I had about 10k laying around I might think about a Premium APO for Lunar/Planetary work.
But a 9.25-11" Cat with a mid FL eyepiece (ND or polarizer filter to cut down on the overwhelming brightness) can match an APO working hard to reach the same power.
Newtonians, are harder to compete against. I have an old 826
Meade F6 tube that is pretty tough for an average 8" Schmidt to equal, I have seen it done with my Henzl C8 but it has custom optics. But wind loading and the large GEM's
are just too much of a pain for me.
I will stick to my Kitty Cats.


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: Why do people even buy SCTs??? new [Re: PowellAstro]
      #6230360 - 12/02/13 09:53 PM

Quote:

In my C90, it was the ring being loose. The bore in the mirror was about .060" larger than the baffle slider tube. Even with it out in hand, you could turn it and the mirror would go clunk each time. Holding the slider in hand, without it being on the primary baffle, you could just touch the mirror with the other hand and wiggle it back and forth with no effort. Also, in this C90, there was no play between the primary baffle and the slider, even with all the grease washed off and the unit squeaky clean. Proof is, I put the unit back together with only a film of grease from a paper towel. I have no play or flop now. While that may not be the norm, it was the cause 100% in this C90.




I think that the C90 must be different than the larger Celestron SCTs. The 8 inch and above have the primary glued in place. The only primary mirror shift in those OTAs comes from the clearance between the baffle tube the primary mirror carrier. I have never seen a primary loose on the carrier in a larger Celestron SCT.

Meade SCTs on the other hand have the primary sandwitched between a couple of gaskets and held in place by a retaining ring. Those I have seen those loose.


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PowellAstro
scholastic sledgehammer
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Reged: 10/14/09

Loc: Tennessee
Re: Why do people even buy SCTs??? new [Re: EFT]
      #6230388 - 12/02/13 10:03 PM Attachment (19 downloads)

Here's what mine looked like:

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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: Why do people even buy SCTs??? new [Re: PowellAstro]
      #6230456 - 12/02/13 10:31 PM

That looks a lot more like the Meade SCTs I have worked on where the primary is held onto the carrier by being sandwitched between a support and locking ring and can move around on the carrier if the ring or the gaskets are loose. The Celestron method is more stable, but if you ever run into the rare occasion where you want to recoat a primary, the Meade system is a lot easier to take apart. Of course the Meade OTA is more difficult to take apart since it is glued together. Both companies apply glue in different places.

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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Why do people even buy SCTs??? new [Re: WesC]
      #6230515 - 12/02/13 11:05 PM

Quote:

Quote:

Quote:



At the speed of light? Really? That's just silly. False logic. It could cross 10,000 times and you would not see any detectable difference. Moving air in a tube is billions of times slower than the speed of light, it will not influence the light more just because its in the tube for a trillionth of a second longer.




hot air speed over a campfire is also lot less speed than a speed of light, but you can see, it changes view throught it very dramatically. turbulence in atmosphere, as so as tube currents also is not faster speed than speed of light, but that also destroy a views. looks like you can have a very big problems with elementar physic understanding...




Nice cheap shot there. You know nothing about me or my level of education. But thanks for taking potshots anyway.

FWIW, you're still incorrect.





Wes, are you suggesting that the path of a light beam passing through turbulent air (i.e., spatially varying indices of refraction) isn't perturbed?

Edited by JJK (12/02/13 11:10 PM)


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PowellAstro
scholastic sledgehammer
*****

Reged: 10/14/09

Loc: Tennessee
Re: Why do people even buy SCTs??? new [Re: EFT]
      #6230527 - 12/02/13 11:17 PM

My C6 is the same as the C90, no glue. My Meade LX200's, the 8 and 14 also have no glue. People say Meade uses glue but it is not in mine that I can see, which are older units. I have had the 8 and 14 Meade units apart a few times for a good cleaning and found no glue. I did find that Meade press fits the OTA end caps to the tube which I like better as there can be no shift to the end caps and there could be some glue there that can not be seen. However, they are easy enough to pull down if you know the units. The Meade units I have, have better light baffles. But they are the larger units. I have not been into the larger Celestron units though.

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EFT
Vendor - Deep Space Products
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Reged: 05/07/07

Loc: Phoenix, AZ
Re: Why do people even buy SCTs??? new [Re: PowellAstro]
      #6230587 - 12/03/13 12:23 AM

Quote:

My C6 is the same as the C90, no glue. My Meade LX200's, the 8 and 14 also have no glue. People say Meade uses glue but it is not in mine that I can see, which are older units. I have had the 8 and 14 Meade units apart a few times for a good cleaning and found no glue. I did find that Meade press fits the OTA end caps to the tube which I like better as there can be no shift to the end caps and there could be some glue there that can not be seen. However, they are easy enough to pull down if you know the units. The Meade units I have, have better light baffles. But they are the larger units. I have not been into the larger Celestron units though.




It's the glue where the front and rear cells are pressed onto the tube that I was referring to. I haven't had the occasion to take apart a C6 so that could be the same as the C90. The C8 and above has the primary glued onto the carrier.


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WesC
Carpal Tunnel
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Reged: 02/06/13

Loc: La Crescenta, CA
Re: Why do people even buy SCTs??? new [Re: JJK]
      #6230653 - 12/03/13 01:43 AM

Quote:


Wes, are you suggesting that the path of a light beam passing through turbulent air (i.e., spatially varying indices of refraction) isn't perturbed?





Absolutely not!

What I am, and have been saying is that it doesn't become visibly MORE perturbed by the light passing through the disturbed air more than once. Its does it all so fast and to such a small degree that the cumulative effect isn't much different that it would be if it passed though that same air once.

Could it be mathematically measured? Maybe, but I'm doubtful.

Could the human eye detect it? No way.


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