Experimenting with double stacking Daystar filter with ...

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Experimenting with double stacking Daystar filter with ...

Post by christian viladrich »

I don't know if this is the correct place to put this post. If not, please don't hesitate to move it where it should belong ...

So, here is a web page where I put the result of some tests with double stacking Daystar filters :

http://www.astrosurf.com/viladrich/astr ... rast-2.htm

You will find the comparison between : Daystar PE 0.6 alone, Ion 0.3 A alone, PE 0.6 stacked withThousand Oaks 0.9A, PE 0.6 stacked with Ion 0.3A.

Here is for example the comparison between Ion 0.3 (left image) and "PE 0.6 stacked withThousand Oaks 0.9A" :
Image

And a comparison between "Ion 0.3 stacked on PE 0.6" (left image) and Ion 0.3A alone :
Image

More on the web page ...

Best regards


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Re: Experimenting with double stacking Daystar filter with ...

Post by cshahar »

Christian, I find your experiments fascinating. I myself was wondering what I can double stack my 0.4 PE with, and perhaps get to 0.2. I find the stacked versions provide better contrast and dynamic range, but there is more nuanced details with the native 0.3 Ion. Aesthetically the stacked versions are more pleasing.

-Charles


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Re: Experimenting with double stacking Daystar filter with ...

Post by marktownley »

Very interesting Christian!

OK, next chapter in your experiment. Instead of the TO 0.9a filter try a naked PST etalon ;)


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Re: Experimenting with double stacking Daystar filter with ...

Post by Montana »

These are fantastic!! :bow
Definitely the double stack every time :)

Alexandra


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Re: Experimenting with double stacking Daystar filter with ...

Post by Derek Klepp »

Thanks for that.


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Re: Experimenting with double stacking Daystar filter with ...

Post by christian viladrich »

This is an old post ;-)

Meanwhile, I've done some testing with various mica-spaced etalons (from 0.6 to 0.3 A) and a 1.5 A hardcoated filter.

Now, my favorite combination in the DayStar PE 0.6 + fused silica 0.5 A etalon + 2 A hardcoated filter.

I'll probably go for a more recent 2 A or 1.5 A hardcoated filter when I have my Sol'ex spectro ready.


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Re: Experimenting with double stacking Daystar filter with ...

Post by christian viladrich »

Interesting ...
Depending what you mean by "blocker"you will still need a 10 A blocking filter somewhere, unless you use this "tuned" DayStar double stack on another etalon having its own BF.
Share some pictures. This would be great.


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Re: Experimenting with double stacking Daystar filter with ...

Post by Bob Yoesle »

unless you use this "tuned" DayStar double stack on another etalon having its own BF.
I agree Christian; this would be the "highest and best use" for this filter. I regret the day I sold my Del Woods 1976 0.7 Å ATM filter. These filters generally had sources of mica which are of better quality and transparency than are currently available, and no mica filter I have looked through since has been better or brighter.

DayStar T-Scanner.jpg
DayStar T-Scanner.jpg (206.88 KiB) Viewed 434 times

Apollo: I'm assuming the blocker and trim filters are deteriorated?

I too don't see how 350 Å and 35 Å nighttime H alpha filters, combined with a 70 Å on KG3 can replace a 10 Å (0.1 nm) trim filter and blocking filter combination. The multiple side band etalon harmonics transmitted by these filters will most certainly overwhelm the H alpha emission with continuum.

Therefore I fail to see how this will "supercharge" the filter system. Moreover, you risk not only damaging the delicate mica etalon, you also risk damaging the filters integrated polaroid's, which are just as essential to the filters functioning. However, replacing the blocker and trim filters with new filters would make it equivalent to a Lunt or Coronado etalon.

DayStar component stack.jpg
DayStar component stack.jpg (202.88 KiB) Viewed 434 times

I sincerely urge you to return the filter to DayStar to remove the blocker and trim filters if they are deteriorated, and check the integrity of the etalon and its polaroid filters, and then reassemble it sans the blocker and trimmer filters. You then will have a unique and excellent filter for double stacking another intact H alpha mica etalon filter system. You would likely be able to recoup your purchase and removal costs by selling it to another solar aficionado, as it is otherwise difficult to double stack primary mica filter system.

Or you could sell it to someone else who would wish to do the above refurbishment.

Good luck with whatever you decide...


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Re: Experimenting with double stacking Daystar filter with ...

Post by mdwmark »

Hi Apollo,
There are a couple thing you going to need to worry about before taking the TS-1 apart. It may be a little different then Bob Image.
The filter stack is under pressure. Depending how much pressure can cause a grease separation. It could occur at the windows or just as easy at the windows the etalon are between. Or it will come out as a stack. You never know till it is to late. If you have a problem at the etalon , then that get scary. You would have to pull the windows off and use the same grease to put it back together. The problem here is that the etalon will be stuck to one of the windows. Now you have to be able to remove it without breaking it.
I'm not sure what you expect to gain. The Kg glass will be transmitting 60% at Ha. The same as a ITF. You still need a order sorter filter (10-15Ang). If you just want the etalon for trying a tandem design , and you get it out without an problem . Keep it under some light pressure (o-ring compressed about .005"). This will keep it together.
Mark W.


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Re: Experimenting with double stacking Daystar filter with ...

Post by christian viladrich »

Hello Mark,
Thanks for these information. Mica-spaced etalon is a bit of an art !
BTW, just to be sure, the polarizers are linear or circular ?


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Re: Experimenting with double stacking Daystar filter with ...

Post by Bob Yoesle »

Hi Christian, I don't know if the following will help, but until Mark responds I assume that they are linear polarizers:

The Dobrowolski patent is silent on the type of polarizer.

However, the references I have seen for both the mica and the magneto optical filter used for solar astronomy state they utilize linear polarizers:

"As mica is a bi-axil crystal, two sets of interference fringes are formed by the etalon. Both sets of fringes are orthogonally polarized and a linear polarizer is required to eliminate one set if the spacers optical thickness is not an exact half-wave multiple of the wavelength of interest."

MOC solar filter layout.jpg
MOC solar filter layout.jpg (124.09 KiB) Viewed 374 times

Fundamentals of Solar Astronomy, A. Bhalnagar, W. Livingston


For Lyot filters:

"The underlying principle of the Lyot filter is that light originating in a single polarization state can be made to interfere with itself. The first element is a polarizer and forces unpolarized light into two orthogonal polarization components. If the polaroid is oriented at 45◦ to the fast and slow axes of a birefringent crystal, one component can be delayed with respect to the other. An exit polaroid, aligned with the entrance polaroid, recombines the orthogonal components to effect interference."

A Tunable Lyot Filter at Prime Focus… J. Bland-Hawthorn, W. van Breugel, et.al.

This seems to imply two linear polarizers are similarly used for mica etalons. Additionally, you would have to make sure the polarizer orientations are correct with respect to the mica birefringent crystal to achieve correct functioning.


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Re: Experimenting with double stacking Daystar filter with ...

Post by christian viladrich »

Yes, this makes sense Bob. Thanks !


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Re: Experimenting with double stacking Daystar filter with ...

Post by Bob Yoesle »

Looks good Apollo.

You might also want to consider getting a hold of Mark at Solar Spectrum, especially since you're dealing with the T-scanner needing to be operated at an "ambient" temperature.

Mark will be able to set it up on his spectroscope and tell exactly what temperature is on-band. Given it is near on-band at "ambient," the use of cooling as well as heating via his TEC system would seem to be advantageous, as opposed to the DayStar system, which still uses a rather simple strip heater and is not able to go below ambient, which could prove problematic on a hot day.

The TEC system would be "the cats meow" if it were my filter.

Good luck, and hopefully this filter provides outstanding performance.
Last edited by Bob Yoesle on Sat Mar 20, 2021 5:06 pm, edited 1 time in total.


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Re: Experimenting with double stacking Daystar filter with ...

Post by mdwmark »

Hi ,
The filters uses circular polaroids . The polaroids are arranged to cancel the internal reflection caused by the bandpass mirror and the etalon mirror. In the image Bob posted. The second polaroid cancels the internal reflection between the ITF and the back side of the etalon. The mica etalon is birefringent , which means it will have two peaks, one in the X axis one in the Y axis. The linear part of the circular polaroid is used to remove the peak you don't want.
If they are not a lined correctly then both peaks will be transmitting light and the filter will have low contrast.
You really need a spectrometer to do this.
The Loyt filter is different then a mica filter. I did used an mica etalon as a order sorter and 1/4 wave plate in a hybrid calcite filter I built years ago.
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Re: Experimenting with double stacking Daystar filter with ...

Post by Bob Yoesle »

Thanks for the correction and clarification Mark!


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Re: Experimenting with double stacking Daystar filter with ...

Post by christian viladrich »

Thanks a lot Mark for this interesting information !!

I was wondering of something else : when we look at these mica-spaced filters, there is a "shiny" or "metalic" side, and a red side.
I understand the "red" side is the side where the RG630 is.
Is the "shiny" side the surface of the blocking filter or the coated surface of the mica plate ?

Just for the fun, here is a picture of the Coronado SMN-35 fused silica etalon :
http://astrosurf.com/viladrich/astro/in ... MN35-b.JPG
I can't figure out which reflections are those of the etalon itself.


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Re: Experimenting with double stacking Daystar filter with ...

Post by AndiesHandyHandies »

Hi

Whats the source of the 1.5 and 2.0 A filters please.

Are they suitable as blockers for PSTs and Quarks?

Cheers. Andrew.


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Re: Experimenting with double stacking Daystar filter with ...

Post by christian viladrich »

Hi Andrew,
The 1.5 A was a Barr Associates filter. It was of top quality and relatively afordable years ago. Unfortunately, Materion (new name of Barr) has a different commercial policy and current prices are astronomical. This filter was not mine :-(

The 2 A was made years ago by Coronado/David Lunt. I guess there is only a very small number of them available. This is the filter seen on the right of this picture (inside a tilt mount) :
http://astrosurf.com/viladrich/astro/i ... MN35-a.JPG


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Re: Experimenting with double stacking Daystar filter with ...

Post by AndiesHandyHandies »

Ah

Un-obtanium.

Thanks


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Re: Experimenting with double stacking Daystar filter with ...

Post by AndiesHandyHandies »

Hi

Came too late in the game to luck on any good stuff, apart from one Quark Chrom.

Cheers. Andrew.


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