4901Re: [tmboptical] Re: Questions On APO Strehl Ratio
- Sep 9 3:20 AMRoland comparation is a bit missleading for apos from Takahashi, Zeiss and TMB , maybe not for his.
His 95% strehl lens was spherical much worser than his 99% strehl lens, which is not such big diffrence in above 3 other company lenses
I can show you a 99% strehl lens with wavefront p.t.v. 1/6 and 1/10 but also with 1/9 and 1/10 wavefront.
so comparing the strehls without seen the topology and knowing something about the wavefront p.t.v. is not very much helpfull
In a Zeiss or a TMB you will have an hard time to see a diffrence between inside and outside focuse if you compare a 95% and a 99% strehl lens, because in both lenses the wavefront p.t.v. is extremly good and does nearly not allow to see such a described diffrence
----- Original Message -----
Sent: Monday, September 02, 2002 3:57 AM
Subject: [tmboptical] Re: Questions On APO Strehl Ratio
Your answer was very educational. Thanks so much for responding to my
inquiry. I was over on the AP Users Group and Rolland had presented a
photo taken through a .95 and a .99 strehl scope. I believe the star
images were twice as bad as normal due to a double pass auto-
collimator (or something like that). The difference was noticable but
I can see your point. I just love to learn all I can about what makes
a quality optic. Thanks again...
--- In tmboptical@y..., "W. Gondella" <gondella@s...> wrote:
> IMO, the difference between a strehl intensity of .95 and .99 is
> A). The seeing is near perfect (sub-second resolution),
> B). You are observing at very high power,
> C). You have very high visual acuity,
> D). You are well schooled in star testing,
> E). And you are using the very best oculars, diagonals down-stream
> In focus or out of focus slightly, you will see the ever so
> energy in the first ring, the barest improvement imaginable in
> detail. Thats about it. Maybe an ever so slight improvement in
> slightly out of focus and tolerance for substandard seeing.
> This is the Shangri-La for:
> 1). The very few who have phenomenal visual acuity and will accept
> less than absolute perfect,
> 2). The number chasers who are either so insecure or vain that
> that scope just so they can tell others they got a .999 scope,
> that they can tell the difference.
> ----- Original Message -----
> From: "garyjmo" <garyjm@v...>
> To: <tmboptical@y...>
> Sent: Sunday, September 01, 2002 3:39 PM
> Subject: [tmboptical] Questions On APO Strehl Ratio
> > Hello all,
> > I understand that strehl ratio takes into account all aberations
> > refractive system. I have also heard that .95 is the cut off for a
> > really great optic. Okay, so when comparing a .95 with say a .99
> > strehl APO, what are the visual differences? Is there any
> > in focus or just out of focus? How would the difference manifest
> > itself? On what objects would this difference be most apparent?
> > Thanks for helping me to gain a better understanding of optics...
> > Gary
> > To unsubscribe from this group, send an email to:
> > tmboptical-unsubscribe@e...
> > Your use of Yahoo! Groups is subject to
Yahoo! Groups Sponsor
To unsubscribe from this group, send an email to:
Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
[Non-text portions of this message have been removed]
- << Previous post in topic Next post in topic >>