Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Equipment Discussions >> Reflectors

Pages: 1
gaz-in
scholastic sledgehammer
*****

Reged: 12/17/07

What does "RTA" Tell me about a Primary
      #5691682 - 02/20/13 08:19 PM

Hi All,

I was looking at a primary that had an RTA of 0.23 . What does this tell me about the quality of the mirror?

Thanks In advance for the inputs


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jason D
Postmaster
*****

Reged: 10/21/06

Loc: California
Re: What does "RTA" Tell me about a Primary new [Re: gaz-in]
      #5691693 - 02/20/13 08:24 PM

Quote:

Hi All,

I was looking at a primary that had an RTA of 0.23 . What does this tell me about the quality of the mirror?

Thanks In advance for the inputs




RTA stands for Relative Transverse Aberration. Basically, it means that all focused light rays off your mirror will be confined to a diameter of 23% the length of the airy disc diameter. RTA of 0.23 represents an exceptional mirror.

Jason


Post Extras: Print Post   Remind Me!   Notify Moderator  
gaz-in
scholastic sledgehammer
*****

Reged: 12/17/07

Re: What does "RTA" Tell me about a Primary new [Re: Jason D]
      #5691711 - 02/20/13 08:31 PM

Thanks, It is an Ed Stevens Mirror with a Strehl of .991, RTA of 0.23 and a peek to valey wave of <1/20. Another mirror I am looking at is Strehl 0.993, RTA of 0.73, and a peak to valley wave of <1/20. Is there realistically a difference between the two (assuming you can believe the ratings).

Edited by gaz-in (02/20/13 08:37 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jason D
Postmaster
*****

Reged: 10/21/06

Loc: California
Re: What does "RTA" Tell me about a Primary new [Re: gaz-in]
      #5691723 - 02/20/13 08:38 PM

Quote:

Thanks, It is an Ed Stevens Mirror with a Strehl of .991, RTA of 0.23 and wavefront of <1/20. Another mirror I am looking at is Strehl 0.993, RTA of 0.73, and wavefront of <1/20. Is there realistically a difference between the two (assuming you can believe the ratings).




Mine is also Ed Stevens with 0.992 Strehl and 0.26 RTA. Do not read too much into these numbers. These numbers are based on measurement samples. I sould say all these mirrors are more or less the same in terms of Strehl/RTA (good quality mirrors). Base your decision on other factors.
Jason


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1


Extra information
27 registered and 19 anonymous users are browsing this forum.

Moderator:  ausastronomer, Phillip Creed, JayinUT, okieav8r 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 289

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics