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ZWO Filters
#11
Sam at Zwo is known to be very good with support for his products and will often Teamview with a customers computer to resolve problems, so you should have no problems obtaining filter data from him.   

Greg could you briefly explain the digitising process.

                   Cheers Russ
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#12
(2019-01-07, 10:34 PM)russj Wrote: Sam at Zwo is known to be very good with support for his products and will often Teamview with a customers computer to resolve problems, so you should have no problems obtaining filter data from him.   

Greg could you briefly explain the digitising process.

                   Cheers Russ

Hello Russ,

It's just a matter of entering pairs of numbers into a file that is read from the graph for each filter. The first number is the wavelength in nm, the second the transmission at that wavelength. The first and last pairs must have a transmission of zero. You read the data from the file via the dialog that appears after clicking "New" under Available Filters when assigning filters to your imaging system.

But I have an easier way. It is a stand alone app that reads the filter graph and allows you to digitize it directly. Unfortunately it needs work to make it usable for people other than me. I am going to include it as part of ST4 when I get the chance.
Clear skies,
Greg

SkyTools Developer
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#13
Hi Greg,

It's very cool that the R & G passbands don't include the Na D lines. Nice way to reduce low pressure Na vapor lamp light pollution.

Do the transmission values need to be evenly spaced as stated in the 'Help' or can you select some points on the edges of the pass bands where the transmission is changing rapidly? How critical are the ripples on the tops of the passbands?

Phil S.
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#14
Thx Greg,  I'll to use the Baader filters for now see how they work out.

                     cheers Russ
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#15
Hello,

Yeah I noticed that too about the NA and D lines.

The points do need to be evenly spaced in nm. For LRGB filters I typically use a spacing of 5 nm. Here is the Astronimik Green filter:

410.000 0.000
415.000 0.500
420.000 3.667
425.000 50.000
430.000 95.667
435.000 95.000
440.000 96.167
445.000 96.500
450.000 96.333
455.000 96.333
460.000 96.500
465.000 96.500
470.000 96.667
475.000 96.500
480.000 96.333
485.000 96.333
490.000 95.833
495.000 95.333
500.000 94.667
505.000 93.167
510.000 80.167
515.000 4.500
520.000 0.500
525.000 0.00

The ripples aren't a big deal. They likely aren't the same from one filter to another anyhow... just get the main curve.
Clear skies,
Greg

SkyTools Developer
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#16
Hello,
         I've made up data set for the "New" ZWO  LRGB filters,  I extracted the data using a grid on an A3 printout of the filter set and inputted the numbers by eye, not sure how accurate they have to be to be of use , but they should be reasonably close.

If anyone would like the data set, contact me and I will send them in txt format.


           Regards Russ
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