July 2 Proms

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p_zetner
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July 2 Proms

Post by p_zetner » Tue Jul 03, 2018 11:20 pm

Greetings Everyone.

My contribution to the inspiring collection of proms on display here!

Cheers, Peter.
Sun_1018064244_bkg-sub_ImPPG_shrp_proc0.png
Sun_1018064244_bkg-sub_ImPPG_shrp_proc0.png (1.07 MiB) Viewed 263 times

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ffellah
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Re: July 2 Proms

Post by ffellah » Wed Jul 04, 2018 12:17 am

Nicely done, beautiful detail !

Franco

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Re: July 2 Proms

Post by DJD » Wed Jul 04, 2018 7:18 am

Peter,
Lots of detail in the image. Having seen your rig on another thread, can I ask if the telecentric magnification is optimal
for the Daystar or could it be reduced for a less magnified view ( without resorting to a reducer ) ?
Best wishes,
David
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p_zetner
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Re: July 2 Proms

Post by p_zetner » Wed Jul 04, 2018 1:47 pm

Thanks Franco and David.

David: My motivation for using a high magnification telecentric comes from the calculations of Christian Vladrich (http://www.astrosurf.com/viladrich/astr ... lar/FP.htm), in partricular this figure: http://www.astrosurf.com/viladrich/astr ... FWHM-N.JPG. Here, Christian has plotted the bandpass fwhm as a function of focal ratio (f#) for a mica-spaced F-P etalon like the Daystar. Daystar recommends f#>30 for their etalons but you can see from the graph that there is room for improvement by pushing to ~f#=50. I wanted to be sure to maximize the performance of my filter and also had in mind to try stacking the Daystar with a Lunt LS50 etalon. The Lunt is even more sensitive to focal ratio, again according to Christian's calculations. I was even contemplating telecentric designs as high as f#=80 but found it too difficult to reduce to reasonable focal ratios (~ 25 to 35) without severe vignetting. As it is, there is pretty significant vignetting (at the Daystar filter) when I use my 4.6x telecentric design and reduce to ~f#=25 but it can be successfully flat-fielded out.

Cheers, Peter.

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p_zetner
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Re: July 2 Proms

Post by p_zetner » Wed Jul 04, 2018 2:27 pm

Here's an example of vignetting with f46 at the Daystar filter and focal reduction to about f25.
Stacked, deconvoluted, sharpened image on the left, contrast enhancement on the right.
(No flat fielding!)

Cheers, Peter.
Sun_120252_vignette_example.png
Sun_120252_vignette_example.png (1.24 MiB) Viewed 225 times

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Re: July 2 Proms

Post by eroel » Wed Jul 04, 2018 2:49 pm

Peter:
Beautiful proms.
Best regards,
Eric.

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Re: July 2 Proms

Post by Montana » Fri Jul 06, 2018 8:59 am

Superb prom, beautiful! :bow
Alexandra

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Valery
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Re: July 2 Proms

Post by Valery » Fri Jul 06, 2018 9:27 am

p_zetner wrote:
Wed Jul 04, 2018 1:47 pm
As it is, there is pretty significant vignetting (at the Daystar filter) when I use my 4.6x telecentric design and reduce to ~f#=25 but it can be successfully flat-fielded out.

Cheers, Peter.
Hi Peter,

I believe this vignetting is due the Celestron telescope and the reducer, not the filter. Filter is just a several plates.

Flat fielding, of course, will make your images excellet in evenness.

Prominences do not require FF at all.

And you prominences image is quite good for the start with a new setup.


Valery
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