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6-inch f/8 seating position troubles...a realization

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#26 vahe

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Posted 14 June 2021 - 01:51 PM

Be aware, be very aware, that a Mewlon is NOT a refractor and will not give as stable images as your refractor. It will require far more attention to cooldown, insulating the tube, etc., in order to actually perform as well as your 6" A-P. 

 

 

 

Mewlon is an open tube reflector, insulating the tube has no effect on its cooling properties.

.

Vahe


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#27 25585

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Posted 14 June 2021 - 03:18 PM

If the problem is getting yourself up & down, I can sympathise. Perhaps a height adjusting chair could be the answer, either electric or other assisted means.  


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#28 Astrojensen

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Posted 14 June 2021 - 03:35 PM

Mewlon is an open tube reflector, insulating the tube has no effect on its cooling properties.

.

Vahe

That is NOT my experience! Now, I don't have a Mewlon, but I do have a Vixen VMC260L, which is somewhat similar in design, in that it's an open tube Cassegrain with a metal tube. I can, at least on windless nights, see a VERY obvious and IMMEDIATE calming of the image, when I insulate the tube by wrapping it with the truss shroud from my 12" Meade dob. This is simply because it prevents the upper half of the tube getting colder than the lower half, which otherwise create very noticeable tube currents. 

 

 

Clear skies!

Thomas, Denmark


Edited by Astrojensen, 14 June 2021 - 03:39 PM.


#29 Reid W

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Posted 14 June 2021 - 05:12 PM

Thomas-does the 260 secondary mirror also support the corrector elements?  Might be more of a heat retention as compared to single mirror secondary of 210.



#30 John Fitzgerald

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Posted 14 June 2021 - 05:31 PM

Too late...Scope is on Amart for sale.

Looks like sale is already pending there.



#31 Spikey131

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Posted 14 June 2021 - 05:39 PM

Yeah, the AP is sold.  He can get himself a nice Mewlon and enough Reflectix to line has scope, observatory, and his housesmile.gif.

 

Good luck with your new CAT, Cotts!


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#32 Tyson M

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Posted 14 June 2021 - 05:55 PM

Finding the right scope for a task is a tougher situation than many think.

 

I found the only solution is many telescopes.  I only have two large ones and realized quickly I need smaller, easier to deploy telescopes for the backyard (still dont have yet until Stellarvue finishes there new doublets).  Ergonomics, backyard GnG viewing, observatory dimensions, travel to and from dark site or the observatory, what targets you wish to look at, how long you observe for typically....ect ect.  All these things and more come into play for owner.

 

Good luck on your quest Cotts! 



#33 Cotts

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Posted 14 June 2021 - 05:59 PM

AP sold within 2 hours of posting to a guy i know in Toronto.... So fast that my CN advert hasn't even been approved yet.!

 

So, anybody got a Mewlon 210 lying around?  I'll even settle for a TEC 200 Mak Cass.....

 

Just goofing around.  Not a real offer to purchase...

 

Dave



#34 CHASLX200

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Posted 14 June 2021 - 06:13 PM

Big scopes do present some logistical challenges, and you do need to plan appropriately. I set mine up on a 56 inch pier. The saddle midpoint of the mount is at about 6’8”. Got the pier in anticipation of eventually getting the 152 mm f9, which I got several years later. Can sit comfortably in a chair and view at zenith, same for my 5inch. Can stand and view with my c11. Some day I will put a dome around it.

Jmd
 

I used a 5lb weight for a older 6" F/9 AP years ago. With my AP800 and SW150 ED i had a super tall pier that was like almost 7ft tall where the rings mounted up to the dovetail.



#35 CHASLX200

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Posted 14 June 2021 - 06:16 PM

Be aware, be very aware, that a Mewlon is NOT a refractor and will not give as stable images as your refractor. It will require far more attention to cooldown, insulating the tube, etc., in order to actually perform as well as your 6" A-P. 

 

 

Clear skies!

Thomas, Denmark

I used one once in my seeing it was pure eye candy at crazy high powers on the planets.  Makes SCT's look like mush buckets.  But i don't have cold weather almost never so maybe that helps. But 600x was easy.
 



#36 sanbai

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Posted 14 June 2021 - 06:21 PM

So, did you also sell the 8" MakNewt? Didn't you like it?

I won't propose anything, I guess you know your needs better.

In any case, I guess and celebrate that you got some fun with so much telescope trafficking smile.gif


Edited by sanbai, 14 June 2021 - 10:20 PM.


#37 payner

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Posted 14 June 2021 - 07:32 PM

I believe with no corrector, cooling fans will be your best advantage for thermal stability with the Mewlon. If with a corrector/meniscus, the insulation would be my priority. One of the niceties of the two largest Mewlon is Takahashi has the thermal management designed into the system. 

No, it's not a refractor, but, for example, solar system, double stars and GC observation, the D-K is designed to excel in such endeavors. The Mewlon will deliver high-contrast views. 

 

Randy



#38 The Ardent

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Posted 14 June 2021 - 08:10 PM

https://www.cloudyni...lockwood-glass/

#39 Cotts

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Posted 14 June 2021 - 10:16 PM

Here's why the flurry of activity....

 

I have had a bunch of scopes from 140mm to 300mm in the past dozen years.   Achros, APOs, Newts, MakNewts, Mak Cass, SCT's.  All top flight gear... The last one was the TEC 160.   It seemed, however, I was repeating myself, more or less... A change was in the wind.

 

I got the itch for a BIG dob last year to break the pattern.  20-inch, top notch glass, bells and whistles.  To pay for it I had to sell the TEC 160.  So I did this spring.  I got part in cash and the rest in the form of the Wirth 8-inch MakNewt, a scope which was never a part of my plan.  I kept the Wirth foe a while, just to see how it was (superb!!).  Then I sold it for the rest of the $ to pay for the 20-inch.

 

So, at this point I had only a 65mm AstroTech APO.  The 20-inch won't be here until fall. Can you imagine a summer without a scope of general functionality? ... Even when the 20 arrives I will need a 'medium' scope for outreach and general use. Everyone with a big dob also has a smaller scope.   So I began nosing around for something..

 

I was talking a bit more than a month ago after our monthly zoom meeting to the fellow club member  to whom i had sold the AP 6-incher years ago.  I asked him how it was going with the scope and his astonishing answer - "I haven't got it out yet..Wanna buy it back?"  So I said, half seriously, "Same price?" and he said, "Yes" and I said "OK, then"....  there was very little planning or forethought other than  I knew it was a quality instrument and, size-wise, might fill the gap between the 65mm and the 20-inch...

 

A few nights with the refractor in my observatory led to the revolt of my old bones and the rest of the story lies before you in the world of CN.

 

What a hobby, eh?

 

Dave


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#40 firemachine69

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Posted 14 June 2021 - 11:22 PM

There's a reason when I came back to the hobby, I was set on a Cassegrain design...

#41 Mirzam

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Posted 15 June 2021 - 07:36 AM

AP sold within 2 hours of posting to a guy i know in Toronto.... So fast that my CN advert hasn't even been approved yet.!

 

So, anybody got a Mewlon 210 lying around?  I'll even settle for a TEC 200 Mak Cass.....

 

Just goofing around.  Not a real offer to purchase...

 

Dave

I had a poor experience with a used Mewlon 210.  There was sufficient mirror flop such that the thing would not stay in collimation when moved to different targets.  I’m too old to mess around with collimation all the time instead of observing.  My advice would be to buy new or purchase a classical Cassegrain instead. (No moving mirror to focus).

 

JimC


Edited by Mirzam, 15 June 2021 - 07:37 AM.


#42 t.r.

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Posted 15 June 2021 - 08:07 AM

I’m too old to mess around with collimation all the time instead of observing. My advice would be to buy new or purchase a classical Cassegrain instead. (No moving mirror to focus).

JimC


My advice would be to buy a refractor!! 🤣

#43 Jon Isaacs

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Posted 15 June 2021 - 08:19 AM

One thing Dave didn't mention.?

 

He's 6 ft 6 in  = 2 meters tall.. scrunching down is not so easy..  tall is good for larger Dobs.

 

Jon


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#44 John Fitzgerald

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Posted 15 June 2021 - 08:25 AM

With a normally mounted 6 inch f/8 or longer refractor, being only about 3 feet tall might help....just saying. cool.gif


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#45 Wildetelescope

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Posted 15 June 2021 - 11:18 AM

One thing Dave didn't mention.?

 

He's 6 ft 6 in  = 2 meters tall.. scrunching down is not so easy..  tall is good for larger Dobs.

 

Jon

I am 6'3", so I can appreciate!   Fortunately I can still hoist 35-40 lbs 6 ft in the air with little problem, but I can see the day when that might be a challenge:-).   Got to start a training regimen to keep my self fit for the hobby:-). 

 

JMD



#46 John Fitzgerald

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Posted 15 June 2021 - 11:55 AM

I am 6'3", so I can appreciate!   Fortunately I can still hoist 35-40 lbs 6 ft in the air with little problem, but I can see the day when that might be a challenge:-).   Got to start a training regimen to keep my self fit for the hobby:-). 

 

JMD

I have been grinding some stumps down with axe and cutter mattock....sort of helps with strength.



#47 Cotts

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Posted 15 June 2021 - 12:52 PM

I had a poor experience with a used Mewlon 210.  There was sufficient mirror flop such that the thing would not stay in collimation when moved to different targets.  I’m too old to mess around with collimation all the time instead of observing.  My advice would be to buy new or purchase a classical Cassegrain instead. (No moving mirror to focus).

 

JimC

The Mewlon IS a Classical DK Cassegrain.  I will probably get a Feathertouch after-market focuser for it anyway.... Set the mirror in one spot and leave it..

 

Dave
 



#48 Mirzam

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Posted 15 June 2021 - 01:24 PM

The Mewlon IS a Classical DK Cassegrain.  I will probably get a Feathertouch after-market focuser for it anyway.... Set the mirror in one spot and leave it..

 

Dave
 

The problem is the mirror support.  I also tried to use a Moonlite focuser to avoid the moving mirror.  It didn’t solve the problem.  I’m familiar with all the various optical designs included under the Cassegrain terminology.  Classical Cassegrain generally refers to a telescope with a parabolic primary coupled with a convex hyperbolic secondary.  I’ve never heard of one being manufactured  that focuses by using a moving mirror. Perhaps the reason is that changing the mirror separation affects the optical correction and the baffling.

 

JimC



#49 Astrojensen

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Posted 15 June 2021 - 03:26 PM

 

Perhaps the reason is that changing the mirror separation affects the optical correction and the baffling.

This happens in any Cassegrain design that focuses by moving the mirrors relative to one another. Changing the mirror spacing changes the spherical correction. 

 

 

Clear skies!

Thomas, Denmark



#50 Spikey131

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Posted 15 June 2021 - 03:36 PM

Get a C8 (or 9.25) install a Feathertouch focuser and be done with it.




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