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12.5 inch classical cass from Adler Planetarium

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#51 CHASLX200

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Posted 03 November 2018 - 04:57 PM

You mean you never picked up the wrong eyepiece or Barlow?  I can't believe anyone is that awake.  Explain what is "empty magnification," in high tech terms and simple for a simple guy.  Yeah, Parker can't hear you.

He can't get it thru his head that we in FL can use insane powers on super nites.  That Cave he though was so so  was a 550x killer in my skies. Seeing makes all the diff in the world.


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#52 Jeff B1

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Posted 03 November 2018 - 05:10 PM

He can't get it thru his head that we in FL can use insane powers on super nites.  That Cave he though was so so  was a 550x killer in my skies. Seeing makes all the diff in the world.

Chas, I gave up long ago explaining Florida seeing.  They will not believe it until the Winter Star Party; then they are experts for life smile.gif

 

When it is good then push it to the limit of your eyepiece collection runs out.


Edited by Jeff B1, 03 November 2018 - 05:11 PM.

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#53 CHASLX200

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Posted 03 November 2018 - 05:17 PM

Chas, I gave up long ago explaining Florida seeing.  They will not believe it until the Winter Star Party; then they are experts for life smile.gif

 

When it is good then push it to the limit of your eyepiece collection runs out.

I do it all the time. Had a 14.5" Zambuto maxed out at 1150x on a nite there was no seeing and gave it all i got with my barlow and 2.5mm Vixen LV eyepiece. Nothing moved even at them powers. That was a once in a lifetime nite.


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#54 Jeff B1

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Posted 03 November 2018 - 05:24 PM

I do it all the time. Had a 14.5" Zambuto maxed out at 1150x on a nite there was no seeing and gave it all i got with my barlow and 2.5mm Vixen LV eyepiece. Nothing moved even at them powers. That was a once in a lifetime nite.

In 1994 when Steve O'Meara (Eagle Eye) was visiting we observed Ganymede at 1,125x and a double blind drawing it was almost alike. Even for the usual great seeing there, that was a keeper.


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#55 starman876

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Posted 03 November 2018 - 06:19 PM

You mean you never picked up the wrong eyepiece or Barlow?  I can't believe anyone is that awake.  Explain what is "empty magnification," in high tech terms and simple for a simple guy.  Yeah, Parker can't hear you.

Oh, I have been there, pushing the limits of magnification.  I cannot imagine who has not tried it. However, you learn very quickly how futile it is.  



#56 starman876

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Posted 03 November 2018 - 06:23 PM

He can't get it thru his head that we in FL can use insane powers on super nites.  That Cave he though was so so  was a 550x killer in my skies. Seeing makes all the diff in the world.

you just cannot get over that Cave can you.  All I ever said that it was not any better than any other scope I had at the time. I never said it was so so.  You made all this up in your head to suit your empty posts.   The Cave was a fine scope. However, it was too much trouble to take out each time I wanted to use it and my other scopes performed just as well or better.  You begged me to sell it to you so I did. 



#57 CHASLX200

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Posted 03 November 2018 - 06:32 PM

In 1994 when Steve O'Meara (Eagle Eye) was visiting we observed Ganymede at 1,125x and a double blind drawing it was almost alike. Even for the usual great seeing there, that was a keeper.

We have better seeing than any other state. You can't make these horses drink the water when they are used to sub 200x power views of mushy planets. I wished i could invite them all over  on a super warm Feb nite and let them get a taste of what really steady seeing is at powers above 800x in 12.5" and bigger scopes.  That 8" F/8.5 Cave i had did 550x and asked for more.  The 5" D&G is just getting warmed up at 400x.


Edited by CHASLX200, 03 November 2018 - 06:33 PM.


#58 tim53

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Posted 03 November 2018 - 11:54 PM

Chas, I gave up long ago explaining Florida seeing.  They will not believe it until the Winter Star Party; then they are experts for life smile.gif

 

When it is good then push it to the limit of your eyepiece collection runs out.

I became a believer when I used Don's 6" f/8 to view Mars in the Keys with you guys in 2000.  Folks, it was a gusty windy night.  The winds on the ground were going one way, and the clouds  were zinging across the sky at about a 90 degree angle.  Mars was razor sharp, though it wiggled around a bit.  

 

Chas, for more than a year I didn't have a finder on my 12.5" f/23 Cassegrain.  I sighted along the flat sides of the tube until the reflection of a planet would merge with the planet in the sky.  I used a 28mm RKE to center, then I'd switch to a 2x barlow and a Pt Grey flea2 camera for imaging.  I had so little trouble finding planets that I resisted putting a finder on.  I didn't want to drill holes in that Teak plywood tube.  a 1/4" thick 4x8 sheet cost me $50 in the late 80s.  I'd hate to think what it would cost now, if you could find it.  


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#59 tim53

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Posted 03 November 2018 - 11:57 PM

We have better seeing than any other state. You can't make these horses drink the water when they are used to sub 200x power views of mushy planets. I wished i could invite them all over  on a super warm Feb nite and let them get a taste of what really steady seeing is at powers above 800x in 12.5" and bigger scopes.  That 8" F/8.5 Cave i had did 550x and asked for more.  The 5" D&G is just getting warmed up at 400x.

Like I think I said in 2000, Florida has laminar air flow because it's a laminar state.  lol.gif   (It's also water soluble, but that's a different issue).

 

-Tim.


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#60 Jeff B1

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Posted 04 November 2018 - 06:03 AM

Somewhere on CN I recently posted a photo of Don and the 6" f/8 we used in the Keys June 2001.  The Edom flash thingy.  Here is a CN post of the 2003 Moon-Mars graze images with his 6" f/8.  https://www.cloudyni...e/?p=6703018   

 

It’s hard not to go off on a tangent about seeing, maybe a bit OT, but here is an account of Florida Seeing done the science way:  http://www.alpo-astr...ida_Seeing.html

 

Can't find all my Classical Cass photos.


Edited by Jeff B1, 04 November 2018 - 06:11 AM.


#61 CHASLX200

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Posted 04 November 2018 - 06:46 AM

I became a believer when I used Don's 6" f/8 to view Mars in the Keys with you guys in 2000.  Folks, it was a gusty windy night.  The winds on the ground were going one way, and the clouds  were zinging across the sky at about a 90 degree angle.  Mars was razor sharp, though it wiggled around a bit.  

 

Chas, for more than a year I didn't have a finder on my 12.5" f/23 Cassegrain.  I sighted along the flat sides of the tube until the reflection of a planet would merge with the planet in the sky.  I used a 28mm RKE to center, then I'd switch to a 2x barlow and a Pt Grey flea2 camera for imaging.  I had so little trouble finding planets that I resisted putting a finder on.  I didn't want to drill holes in that Teak plywood tube.  a 1/4" thick 4x8 sheet cost me $50 in the late 80s.  I'd hate to think what it would cost now, if you could find it.  

Some scopes are just easy to point and find stuff and some others not so easy.  MY D&G i just line up that screw head from the cell on a object and there it is in the FOV.  So for seeing, it is not like every nite is dead still. Summers seem to the worst for steady seeing, winters are super bad just after a front with dropping temps. But Feb on super warm nites and no temps drops always is my number one month for steady seeing.



#62 CHASLX200

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Posted 04 November 2018 - 06:47 AM

Like I think I said in 2000, Florida has laminar air flow because it's a laminar state.  lol.gif   (It's also water soluble, but that's a different issue).

 

-Tim.

Seeing is even better in south FL vs my area.



#63 starman876

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Posted 04 November 2018 - 09:01 AM

Somewhere on CN I recently posted a photo of Don and the 6" f/8 we used in the Keys June 2001.  The Edom flash thingy.  Here is a CN post of the 2003 Moon-Mars graze images with his 6" f/8.  https://www.cloudyni...e/?p=6703018   

 

It’s hard not to go off on a tangent about seeing, maybe a bit OT, but here is an account of Florida Seeing done the science way:  http://www.alpo-astr...ida_Seeing.html

 

Can't find all my Classical Cass photos.

very interesting paper.  What has seeing been like in FL since the paper was written? With all the Hurricane activity this year it would seem that would have a great effect on seeing.  I know the jet stream in my area is always affecting the seeing. 



#64 Jeff B1

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Posted 04 November 2018 - 09:45 AM

Well, since I moved away in 1996 I’m not sure except a few times observing with Parker; last time in 2014 at his home and the “seeing” was quite good as usual.  The only weather related thing we ever noticed was seeing really got bad after a cold front or when dust came in from Africa.  Some volcano eruptions messed up seeing a few times.  It is not all that difference from where I live now, 135 miles north of Miami in the center of Florida.  At times it is even better here, but hat is just antidotal.



#65 starman876

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Posted 04 November 2018 - 10:00 AM

Well, since I moved away in 1996 I’m not sure except a few times observing with Parker; last time in 2014 at his home and the “seeing” was quite good as usual.  The only weather related thing we ever noticed was seeing really got bad after a cold front or when dust came in from Africa.  Some volcano eruptions messed up seeing a few times.  It is not all that difference from where I live now, 135 miles north of Miami in the center of Florida.  At times it is even better here, but hat is just antidotal.

A shame FL gets hit by so many storms.  I am a firm believer that the last thing I want to be doing in retirement is learning how to survive the weather.   I was going to buy a home in Naples, but decided against it.    However, I would love to check out the seeing.  


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#66 Jeff B1

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Posted 04 November 2018 - 11:23 AM

Starman,We used to get close calls in Dade County, and then Andrew in 1992 made up for all of the misses.  Highlands County saw Charley, Frances and Jeanne in 2004; we missed much of Charley, but glad; it was a bad one.  Close missed Wilma in 2005 with a few TS after that, until 2017 with Irma.  Only minor damages here.   Naples has had some close calls but the only direct one I remember was Andrew in 1992.  You can see them all here: http://vortex.plymou...u/tropical.html

 

I would rather do hurricanes than those tornadoes or floods or blizzards any day.  I remember trying to leave Binghamton, NY in late 1969 when we had to delay a week due to a blizzard.   Hum, snow snakes!


Edited by Jeff B1, 04 November 2018 - 11:24 AM.


#67 CHASLX200

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Posted 04 November 2018 - 11:44 AM

Starman,We used to get close calls in Dade County, and then Andrew in 1992 made up for all of the misses.  Highlands County saw Charley, Frances and Jeanne in 2004; we missed much of Charley, but glad; it was a bad one.  Close missed Wilma in 2005 with a few TS after that, until 2017 with Irma.  Only minor damages here.   Naples has had some close calls but the only direct one I remember was Andrew in 1992.  You can see them all here: http://vortex.plymou...u/tropical.html

 

I would rather do hurricanes than those tornadoes or floods or blizzards any day.  I remember trying to leave Binghamton, NY in late 1969 when we had to delay a week due to a blizzard.   Hum, snow snakes!

My part of FL has not been hit since 1921.  We never get a real storm, while south FL and the Panhandle gets much more action. Homes in South FL avg 500k while homes on the water in may area under 120k.  You can buy a 6 bedroom on the water where i am for under 250k, if you can get it insured.  I paid cash and don't have flood or HOI INS on my house. I have saved enough in 14 years to buy two more homes since Ins cost so much in my area.  These homes were under 20k back after the big crash in 2010 and the Ins was over 8k a year to insure a house worth under 40k west of US19.


Edited by CHASLX200, 04 November 2018 - 11:49 AM.

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#68 starman876

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Posted 04 November 2018 - 12:00 PM

Starman,We used to get close calls in Dade County, and then Andrew in 1992 made up for all of the misses.  Highlands County saw Charley, Frances and Jeanne in 2004; we missed much of Charley, but glad; it was a bad one.  Close missed Wilma in 2005 with a few TS after that, until 2017 with Irma.  Only minor damages here.   Naples has had some close calls but the only direct one I remember was Andrew in 1992.  You can see them all here: http://vortex.plymou...u/tropical.html

 

I would rather do hurricanes than those tornadoes or floods or blizzards any day.  I remember trying to leave Binghamton, NY in late 1969 when we had to delay a week due to a blizzard.   Hum, snow snakes!

Sounds like the odds of a big one hitting are overdue in FL.  well, a big one just hit the panhandle.  My heart goes out to those people.  VA gets very few bad storms.  One of the reasons we decided to stay in this area.  Founders fathers knew washington DC was a safe place to live.  



#69 Jeff B1

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Posted 04 November 2018 - 12:14 PM

Sounds like the odds of a big one hitting are overdue in FL.  well, a big one just hit the panhandle.  My heart goes out to those people.  VA gets very few bad storms.  One of the reasons we decided to stay in this area.  Founders fathers knew washington DC was a safe place to live.  

Hum, Jim Jones must have left some of his witches brew there lol.gif


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#70 Darren Drake

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Posted 04 November 2018 - 09:41 PM

Mark and I tested out the optics tonight.  Not to bad with maybe some overcorrection.  Question.   Can the spacing between the primary and secondary be slightly changed to add undercorrected in a classical cass?  Mirrors will be sent to be recoated soon..

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#71 starman876

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Posted 04 November 2018 - 10:31 PM

I think if you set up a DPAC rig you can see how the spacing affects the over or undercorrection.


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#72 Jeff B1

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Posted 05 November 2018 - 05:33 AM

Darren, The separation between primary and secondary mirrors in a Classical Cassegrain reflector is critical. However, a small difference can be tolerated and is computed from:   (B) = 0.00248FR^4   (if in centimeters then (B) = 0.063 FR^4 ), where FR is the focal ratio of the primary and the separation can be of 45% closer (-B) together or 55% further apart (+B) is tolerated  [Cox, Robert and R.W. Sinnott, "On Focusing a Cassegrain," (REF: Roger N. Clark, Applied Optics, 1,266, May 1976), Sky and Telescope , Vol. 54, No. 4, pp. 293, October 1976.].


Edited by Jeff B1, 05 November 2018 - 05:36 AM.


#73 Napersky

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Posted 05 November 2018 - 08:59 AM

Darren isn't the Dan Joyce George Lucas scope at Skywalker Observatory a 10" Classical Cassegrain?

 

If so who did the secondary?

 

Mark



#74 Darren Drake

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Posted 05 November 2018 - 09:05 AM

No it's a Newt.  Dan's outreach scope today is the original mirror from that scope.  


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#75 CHASLX200

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Posted 05 November 2018 - 07:13 PM

Why is someone looking into another scope with a scope?




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