Other Bands to View the Sun?

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Valery
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Re: Other Bands to View the Sun?

Post by Valery »

pbsastro wrote:Now I would welcome opinions about what is best for visual. Na or HeD3. I will go only with one of those. Na and HeD3 are so close, only 2nm (20A) apart (587.5 and 589.5) that we could think it could be possible that just one filter could reach both with extra tuning, but I think the blockers would need to be different.
From the sample I see Na and He are similar, mixing WL view with plages and faculae. My thing is that I love CaK views, but I am reducing it to near zero, due to possible eye damage, so I am considering that Na could give me the same faculae and plages in a WL background. It may may not look so good as in CaK, but the Na light is much more visible to the eye, so that could be an advantage for visual. And it would give two in one (WL and CaK). But I guess if it were good enough it would be more used.
Looking at some graphics, the HeD3 line seems to be too weak relative to close neighbor lines, so I fear it may require some image processing and be not so adequate for visual.

Another issue is that both Na and He lines are narrow, below 0.4A, so that Mark suggests double stack may work better, so it will not be no easy to get equivalent samples to help decision.

Pedro

If I will be you, I'd never spend money for any of these yellow filters. Too insignificant difference vs, for example, green light.
May be G line at near 430nm? At least much higher granulation contrast.

I may be well wrong in my reasoning, but I really never saw any impressive image of the sun through these yellow filters.


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Re: Other Bands to View the Sun?

Post by Valery »

Here one can see sun photos (not that of high quality) He and Sidium Na .

He D3 looks more interesting.

http://www.company7.com/daystar/products.html


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Re: Other Bands to View the Sun?

Post by Merlin66 »

OK under better control conditions ( and using the proper Baader D-ERF - Doh!)
I've obtained some calibrated spectra in the region around the Na lines with 20/25/and 30 degree tilt. I've also check the bandpass at Ha with the 30 deg tilt.
This definitely shows the D-ERF can be set to a 30 degree tilt (and probably slightly more) and pass both the Na and Ha lines.
Any questions let me know.
DERF tilt Na.JPG
DERF tilt Na.JPG (111.23 KiB) Viewed 3485 times
DERF tilt Ha.JPG
DERF tilt Ha.JPG (112.45 KiB) Viewed 3489 times
Last edited by Merlin66 on Fri Jan 23, 2015 3:28 am, edited 1 time in total.
Reason: rescaled Na profile


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Re: Other Bands to View the Sun?

Post by Valery »

The only question remains: is it worth of money and efforts and what special to look at? I mean in Na or He D3 lines.


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Re: Other Bands to View the Sun?

Post by swisswalter »

Hi Ken

great presentation of the interesting results


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Re: Other Bands to View the Sun?

Post by marktownley »

Good graphs Ken, good question Valery!


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Re: Other Bands to View the Sun?

Post by pbsastro »

Thanks a lot Ken. Great results, not only the shift lets Na and He in but also keeps Ha at near full transmission.
It also proves the minimum tilt is 30 degrees, a little more if we want full Na/He transmission.

Meanwhile I tried my D-ERF (hold by hand) against some street lights, which I think are mostly sodium emitting, and the results match this exactly:
0-20 deg: dark red
30 deg: yellow, medium brightness
45 deg: pure yellow, maximum brightness
60-90 deg: full green
So this quick test suggested 30 deg as minimum and 45 deg for ideal transmission, but it was not conclusive because I don't have the isolated Na line. The spectrometer is the proof and tell us the whole trend of the curve.

So, D-ERF tilt It is a very cheap way (no glass to buy, just a tilting adaptor) to get a multi-ERF, and a very god one, because being D-ERF, it fully blocks UV and IR.
Thanks a lot Ken!


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Re: Other Bands to View the Sun?

Post by pbsastro »

Valery wrote:The only question remains: is it worth of money and efforts and what special to look at? I mean in Na or He D3 lines.
Valery, is WL worth the money, effort and risks?
I am not sure but it it seems Na (or He) is at least as good as WL, with added benefits.
I don't like heat getting inside my scopes (accidents, heat waves, etc). So I decided not to waist money on a WL wedge, so I started saving there. Now I don't have to buy a new ERF, saving again.
Now I am wondering if it would not be possible to use the same etalon/oven/controller for Ha/Na/He, switching only the blocker. Is the blocker required to be inside the filter housing? MarkW can you help here?
Even a double stack could be shared by just switching the blocker?

The main problem I see with Na (or any other filter) is that the Euro lost 23% to the USD and narrowband filters (all USA made) are looking worse each day.

Now Valery, I am very interested on comparing images of Na and HeD3, but there seems to not be many around, specially high resolution.

Pedro


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Re: Other Bands to View the Sun?

Post by marktownley »

The biggest problem I see with tilting an ERF so much is the astigmatism it will introduce....


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Re: Other Bands to View the Sun?

Post by Valery »

pbsastro wrote:
Valery wrote:The only question remains: is it worth of money and efforts and what special to look at? I mean in Na or He D3 lines.
Valery, is WL worth the money, effort and risks?
I am not sure but it it seems Na (or He) is at least as good as WL, with added benefits.
I don't like heat getting inside my scopes (accidents, heat waves, etc). So I decided not to waist money on a WL wedge, so I started saving there. Now I don't have to buy a new ERF, saving again.
Now I am wondering if it would not be possible to use the same etalon/oven/controller for Ha/Na/He, switching only the blocker. Is the blocker required to be inside the filter housing? MarkW can you help here?
Even a double stack could be shared by just switching the blocker?

The main problem I see with Na (or any other filter) is that the Euro lost 23% to the USD and narrowband filters (all USA made) are looking worse each day.

Now Valery, I am very interested on comparing images of Na and HeD3, but there seems to not be many around, specially high resolution.

Pedro
Pedro,

You didn't take my point. Na or He D3 _narrow_ band etalons are NOT worth their price cause their minor new features are not enough to justify the
major additionsl cost. I'd better spend these money as follow (one of them):

1. Large aperture WL imaging - larger SCT + Baader Solar film or Baader Herschel prism
2. Double stack of H-a or buy significantly narrower filter or increase aperture as well
3. Double stack CaK with aperture rise

Any of these way to go will benefit more than a Na or He D3 etalon. These etalons are necessary for solar scientists, not for amateurs who just spend
the time and money on the hobby and are hunting for impressive pictures and not for extracting of the scientific data.

Valery.


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Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.
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Re: Other Bands to View the Sun?

Post by Valery »

marktownley wrote:The biggest problem I see with tilting an ERF so much is the astigmatism it will introduce....
To escape of astigmatism, you need to place another flat transparent plate of the same thickness as the BF and tilted versa.

Like this ========== /== \ =====>| F'

Where / - Block filter \ - counter flat plate.

Valery.


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Re: Other Bands to View the Sun?

Post by marktownley »

This is the arrangement I have done with filters in my CaK stack Valery ;)

To be honest, if I was looking to observe / image down in 500nm region I would probably just use a UV/IR cut on the nosepiece of the telecentric at apertures less than 100mm. Above 100mm aperture the Baader UV/IR cut is available in larger sizes and would just mount a larger version sub aperture in the tube.


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