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RASA 11 - center lens array (rotates)?

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14 replies to this topic

#1 Ron in Michigan

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Posted 15 August 2019 - 04:38 PM

I have a RASA 11 and have not been able to get a flat in focus field from edge to edge. After much tweaking of spacing and adding Baader UFC I now get center and left side in focus and the right side of the full frame sensor has donuts (out of focus),
When I change cameras or spacing and I rotate things on (extensions etc) the enter unit rotates.  IS this something they aligned carefully at the factory?  Or does it not matter how much it rotates?
I don't feel I should have this much problem with a 3500. scope that is designed for imaging. 

I just read a early review and the reviewer said his center lens array rotated and Celestron said to swap the scope for a new one.  Is that necessary? 

 



#2 DuncanM

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Posted 15 August 2019 - 05:14 PM

Contact Celestron.  I don't think the lens should rotate.


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#3 Benni123456

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Posted 17 August 2019 - 09:55 AM

my god 3500 dollar and then completely lousy build.

What is Celestron thinking. Just cost saving at any price.

 

I wonder who builds these scopes together. Foxcon is known to use schoolchildren who are told they do  not get their degree when they do not work. Do they have similar practices at Celestron?



#4 kingjamez

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Posted 17 August 2019 - 03:07 PM

my god 3500 dollar and then completely lousy build.
What is Celestron thinking. Just cost saving at any price.

I wonder who builds these scopes together. Foxcon is known to use schoolchildren who are told they do not get their degree when they do not work. Do they have similar practices at Celestron?


Blow things out of proportion much?

#5 Astrojedi

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Posted 19 August 2019 - 08:34 AM

I have a RASA 11 and have not been able to get a flat in focus field from edge to edge. After much tweaking of spacing and adding Baader UFC I now get center and left side in focus and the right side of the full frame sensor has donuts (out of focus),
When I change cameras or spacing and I rotate things on (extensions etc) the enter unit rotates.  IS this something they aligned carefully at the factory?  Or does it not matter how much it rotates?
I don't feel I should have this much problem with a 3500. scope that is designed for imaging. 

I just read a early review and the reviewer said his center lens array rotated and Celestron said to swap the scope for a new one.  Is that necessary? 

No the secondary assembly is not supposed to rotate. Sometimes the gasket comes lose. A rotating secondary assembly makes it almost impossible for the scope to hold optical alignment. You need to contact Celestron.



#6 Ron in Michigan

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Posted 23 August 2019 - 11:09 AM

I removed the camera train and the large ring.  I tried to rotate the corrector assembly with the camera and ring off and I could not?   
Oddly the camera train and lock down ring rotate when installed? 

Celestron finally responsed to me plea for help and is talking about returning it for repair. I bought it in Nov of 2018 and not had a flat frame yet.
But I'm close?  (Do I send it in?) Or....

Am I to picky? After almost a year of trying to tweak out a flat star field. I got my best to date... but Still not good enough for me? 

please advise that this is great or send it in.  Or try this or that? 

I pick one sub from last night. My flattest yet.  About 2mb download compressed to a jpg.  My biggest problem is on the right and lower right. 
Often upper left and lower right.

 

https://www.dropbox....GB_VNG.jpg?dl=0


Edited by Ron in Michigan, 23 August 2019 - 11:10 AM.


#7 th3r3ds0x

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Posted 23 August 2019 - 06:29 PM

I too have a rasa 11 and it’s solid.  It’s it possible you were just rotating the celestron camera adapter that is held by the knurled ring?  Sounds to me like this could be all that was rotating and if that’s the case you just need to snug it up better. Don’t go crazy though because you can loosen the assembly my mistake if you over-tighten the ring.  I hope that helps.

 

Sean



#8 f430

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Posted 24 August 2019 - 10:45 AM

There's poor stars in all the corners, and if that image is the Best you can get, I'd send the scope in for repairs!

 

You shouldn't have to fight to get round stars!

 

If you bought the scope new from a local dealer, ask/push/coerce them to ship the scope for you, or if there is a replacement warrentee. 



#9 th3r3ds0x

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Posted 24 August 2019 - 11:07 AM

Under warranty I think Celestron would provide a shipping label. Hopefully it doesn't need it but I’ve heard they have turned other RASAs around pretty quick.

#10 drone1_de

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Posted 27 August 2019 - 11:38 AM

as far as I can see I would say your scope is simply not collimated well enough, sth that you can fix on your own

Checked it?

Regards,

Lars



#11 Ron in Michigan

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Posted 09 October 2019 - 11:13 AM

I FEARED I'd have to pay to ship it to CA.  But NO - they were excellent. I boxed it and they paid to ship it there and back - turn around with ship time was about 3 weeks.  This let me go back to my 6"APO and doing sold finally SEALED THE DEAL on the RASA.  I had it up to sale for 8 months turning down all parties as I was still testing.
Well you can't go back.

IT is now back (about a week) only a couple nights use and it is MUCH better.  But if not in perfect focus (difficult with the huge focus steps (1800-2000) wow it's very fine.
I do still occasionally see one corner a bit soft. But I'm also not locking the mirror as I'm remote. (I need it nearly locked but it will still auto focus.
I think I can live with it.

test... 
 

Attached Thumbnails

  • fulltestsm.jpg

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#12 Ron in Michigan

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Posted 11 October 2019 - 01:18 PM

It's not consistent. Which makes me think it's mirror flop.  Sometimes all is good like above. Other times not so much. I'll see if I can attach a couple examples. 
The issue moves and comes and goes.  I am not local to the scope so I can't use the mirror locks!   I have found it is better now that I locked them then loosened them 1/4 turn.
It will still autofocus and doesn't seem to flop as far?  not sure how it works.  Also when I see bad edges I should go there and lock the mirror and shoot another comparison. 

Over all concensous (from me) is I might have a little to much spacing. Sometimes it's fine other times I see stars on the edges bending in a circular fashion. Maybe I'll 
move the camera in 1-2mm closer still. 
 

Attached Thumbnails

  • not perfect.JPG
  • spacing.JPG


#13 Ron in Michigan

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Posted 11 October 2019 - 01:20 PM

We've started a RASA fb group and I'm seeing A LOT OF THIS SAME ISSUE even with 8".



#14 Monsy

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Posted 11 October 2019 - 10:35 PM

Hey! Had the same issue with my RASA 8 from the image point of view but I had no problem with rotating lens assembly (see my other thread here). After lot of discussion with a seller who had no experience with the RASA Celestron said to change it out. I was completely unhappy with my RASA due to the lack of flat field, cause a flat field is what we pay for and what it’s all about (f.e. I would like to do mosaics)! I did change it (new one not here yet) and would recommend doing so! A 3500 RASA without a flat field? No way - I would say!
Best regards!

#15 Monsy

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Posted 11 October 2019 - 10:43 PM

Oh and one more thing: my RASA was from the end of 2018 /beginning of 2019 as well! I have the impression that there were issues with some of the first batches! The other RASA my seller had in stock has the same issue I heared from Celestron.


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