Author Topic: Reducing down my data, the bad and the good.  (Read 392 times)

coachroninil

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Re: Reducing down my data, the bad and the good.
« Reply #15 on: January 26, 2018, 03:43:46 AM »
Quote
Plugging in the data into Figure XP I get:

8" f/3 primary:

PV wavefront 1.42 wave
Transverse error 13.23
Encircled Energy ratio .087
Strehl .016
surface error 82.7
Just checking, you do have the fixed/moving light source correct?

Dave
Edit and what data did you input? Old or have you retested?

Jack Jefferson

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Re: Reducing down my data, the bad and the good.
« Reply #16 on: January 30, 2018, 12:15:30 PM »
Here is the data sheet on the 8" f/3 from XP:
Here's the 10"f/7":
looking at the readings for the different zones, how can the XP program be correct?

So, is the program BS, and I should just ignore it? Or use it as a guide in trying to understand the zone measurements?
Or . . .

Randy Wiggins

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Re: Reducing down my data, the bad and the good.
« Reply #17 on: January 31, 2018, 11:30:49 AM »
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Quote

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I understand that .996 is impossible, but I'm only saying what the program says.
Back then, back about '75, I did take several tests, even rotating the mirror 180. I understand the bias, and taking measurements from scratch each time. I also understand about human error, but it seems it would average out (?).

The star test is very good.
Yeah that's a common issue with Foucault and reduction programs, people often take them as biblical quotations  It would be really nice to try take some star test images with your phone, on the brightest star you can get, at the highest elevation, to minimize seeing. Sirius is good for me, but I think you'd be better off with Capella or such.

If you measured that f/3 by itself, then you need to have the program adjust to find the best conic fit. -1 works only for a perfect parabola, so I'm not surprised the Strehl is off, if there is a significant correction difference at this f/ratio.
But in the Gregorian, it's suppose to have a parabola for the primary, and an ellipse for the secondary.
Yes, is supposed to, but I'm sure its not a perfect corrected parabola. So you should run it with "find best fit conic". OH, and check if all data are fixed or moving light source and make sure the program is set right!

Ronald Saldana

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Re: Reducing down my data, the bad and the good.
« Reply #18 on: February 03, 2018, 05:19:27 AM »
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Quote

Quote
<p class="citation">QuoteI figured and null tested the secondary. Plugging in the data into Figure XP I get:
PV wavefront 1.42 wave
Transverse error 13.23
Encircled Energy ratio .087
Strehl .016
surface error 82.7

What conic are you using for this test?
Mark, that is the primary, not the secondary.

"I figured and null tested the secondary. Plugging in the data into Figure XP I get:8" f/3 primary:
PV wavefront 1.42 wave
Transverse error 13.23
Encircled Energy ratio .087
Strehl .016
surface error 82.7"

Dave
Sorry, I spaced that line - went from "tested the secondary" to the output. 

You're right, it's not very good if those numbers are at all reliable. Actually it wouldn't really work at all, which is why I raised a question.

FWIW the 10" f/7 has a huge tolerance compared to the 8" f/3.

lorndwatassi

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Re: Reducing down my data, the bad and the good.
« Reply #19 on: February 03, 2018, 07:11:13 AM »
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I don't agree that my 10" mirror is perfect. I will accept very good.
I agree the 8" mirror isn't good. I didn't think it would be sobad.

I guess the program puzzled me, I didn't think my average readings were that good, to give such results on the 10".
I felt something may be wrong with the primary on the 8", but I didn't think the data would give such badnumbers.
Then the opposite on the 10", the program gave better results than what I thought they would be. I will try and post a pic of the Figure XP pages.
If you look at the % zonalcorrection for the 10" then it may seem bad but you have to remember it is comparing each zone to the previous zone, not to zone 1. For example zone 3 looks bad but that is because zone 2 has no correction.
If you look at the actual knife readings compared to the ideal knife readings then they are all under with only zone 4 with any significant difference. At f/7 that is why it tests well.

The 8" has quite a deep central hole but a lot of it is hidden by the secondary.

Dave

Edit: Looking again I should say some of it is hidden by the secondary

poithegepur

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Re: Reducing down my data, the bad and the good.
« Reply #20 on: February 09, 2018, 01:17:09 AM »
Quote
<p class="citation">Garyth64, on 11 Feb 2017 - 12:05 AM, said:<a href="https://www.cloudynights.com/index.php?app=forums&amp;module=forums&amp;section=findpost&amp;pid=7698348" rel="citation">[/url]<blockquote class="ipsBlockquote built" data-time="1486764337" data-cid="7698348" data-author="Garyth64">Plugging in the data into Figure XP I get:8" f/3 primary:PV wavefront 1.42 waveTransverse error 13.23Encircled Energy ratio .087Strehl .016surface error 82.7
Just checking, you do have the fixed/moving light source correct?DaveEdit and what data did you input? Old or have you retested?[/quote]I have a fixed light source. In the hand written data, the light source moves (I believe from the readings since they are 1/2)For the 8" primary, that data is old, from '69. For the 10", the data is also old, from '75.

Chuck Klem

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Re: Reducing down my data, the bad and the good.
« Reply #21 on: February 09, 2018, 09:09:39 AM »
Actually zone 2 on the 10" has a reasonable difference as well but it has less affect since it is in the central region.

Dave

Ligon Payton

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Re: Reducing down my data, the bad and the good.
« Reply #22 on: February 09, 2018, 10:33:26 AM »
Quote
Quote
I don't agree that my 10" mirror is perfect. I will accept very good.
I agree the 8" mirror isn't good. I didn't think it would be sobad.

I guess the program puzzled me, I didn't think my average readings were that good, to give such results on the 10".
I felt something may be wrong with the primary on the 8", but I didn't think the data would give such badnumbers.
Then the opposite on the 10", the program gave better results than what I thought they would be. I will try and post a pic of the Figure XP pages.
If you look at the % zonalcorrection for the 10" then it may seem bad but you have to remember it is comparing each zone to the previous zone, not to zone 1. For example zone 3 looks bad but that is because zone 2 has no correction.
If you look at the actual knife readings compared to the ideal knife readings then they are all under with only zone 4 with any significant difference. At f/7 that is why it tests well.

The 8" has quite a deep central hole but a lot of it is hidden by the secondary.

Dave

Edit: Looking again I should say some of it is hidden by the secondary
Yes, it is hidden. And I've read, that the center section could be "subtracted" out, to try and make the other readings fit into the tornado.