Re: Star Eccentricity Help

Mike Shade

The value of .5 is stated as round, I am curious if .05 is what people mean.  According the Maxim's help, a value of .1 means that the star is longer in one axis by 10%, so a value of .5 would be 50%.  That would be horribly out of round.  Want to make sure that I am following.  With my system, PW 17/AP1600 (non AE)/STL6303E camera/Optec Gemini rotating focuser/.63" pixel/5' subs I generally get roundness values from .01 to .05, depending on where the system is pointed/seeing.


Mike J. Shade

Mike J. Shade Photography:


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Already, in the gathering dusk, a few of the stars are turning on their lights.

Vega, the brightest one, is now dropping towards the west.  Can it be half

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From: [] On Behalf Of Brian Valente
Sent: Sunday, August 09, 2020 9:23 AM
Subject: Re: [ap-gto] Star Eccentricity Help


>>>  Is the solution a Planewave?? J


  either that, or I hear AP has a 17" reflector they are working on :)


>>What should I expect for good eccentricity - .35ish??


generally eccentricity of 0.5 or lower is considered 'perceptibly round'


I'm not sure i would 'expect' that, but i would certainly aim for that




On Sun, Aug 9, 2020 at 9:10 AM Tony Benjamin <tonybenjamin@...> wrote:

Thanks Brian. I’m sure mirror flop is a definite possibility, even with the Edge mirror being “locked down”. Is the solution a Planewave?? J


What should I expect for good eccentricity - .35ish??


From: [] On Behalf Of Brian Valente
Sent: August 9, 2020 9:04 AM
Subject: Re: [ap-gto] Star Eccentricity Help


Okay thanks


I'm poking around in your logs some, and I'm waiting to hear back from someone else I asked a Q about, but I can see your RA corrections are primarily one-sided at higher altitudes (and a corresponding increase in RA and therefore your eccentricity goes up), and as you get lower in the sky, RA corrections become more even on both sides, and your RA RMS and eccentricity both go down


My suspicion is mirror flop or something shifting in your equipment


On Sun, Aug 9, 2020 at 8:54 AM Tony Benjamin <tonybenjamin@...> wrote:

No, no seperate guide scope. I'm using an Ultrastar guide camera on a QHYOAG.







Brian Valente







Brian Valente

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