My Lunt B600 CaK diagonal anatomy and spectral curves

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My Lunt B600 CaK diagonal anatomy and spectral curves

Post by dvmak »

Hi all,

Here is a small homework done just recently, and the topic is Lunt B600 CaK solar scope.
I have purchased it from a local distributor, being happy enough to get a sale item for a very affordable price. The deal was at the beginning of 2013, and I started to use it only this summer. Unfortunately, image suffered from a serious astigmatism, and the chance to get a substitution from the seller was very small. So I decided to disassemble it and try to locate the reason of this aberration.
This topic is dedicated to the disassembling of the original setup and spectral measurements of every component.
Let's start from the very beginning. Here are the pictures of the general view of the CaK diagonal:
Attachments
03_Assembly03.jpg
03_Assembly03.jpg (164.18 KiB) Viewed 6014 times
02_Assembly02.jpg
02_Assembly02.jpg (118.46 KiB) Viewed 6014 times
01_Assembly01.jpg
01_Assembly01.jpg (140.71 KiB) Viewed 6014 times


With best regards,
Dmitry Makolkin.
_____________________________________________________________________________
Solar continuum imaging with TAL-250K, Baader solar continuum and Barlow 1.4x
CaK with TAL-75R and Lunt calcium K-line B600
Camera: ZWO ASI174MM.
My solar images gallery: http://www.makolkin.ru/Gallery/SolarSys ... llery.html
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by dvmak »

The front tube contains two filters that work as a block filter – their role is to suppress the unwanted transmission of the etalon, remaining only the narrow peak at the needed wavelength of CaK emission.
Attachments
04_Front01.jpg


With best regards,
Dmitry Makolkin.
_____________________________________________________________________________
Solar continuum imaging with TAL-250K, Baader solar continuum and Barlow 1.4x
CaK with TAL-75R and Lunt calcium K-line B600
Camera: ZWO ASI174MM.
My solar images gallery: http://www.makolkin.ru/Gallery/SolarSys ... llery.html
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by dvmak »

The first filter is rather big in diameter and is located quite far from the focal plane. It is tilted in its cell to take ghost reflection away from the sun image. It's interesting to mention that the tilt pf the flat plate adds astigmatism to the slow scopes and coma to fast scopes ( in fact, both of them, but each of them dominate in certain conditions).
Filter cell can be just inserted into the 2" tube and angular position of the tilt direction can be set to any angle.
White color marks are not original, I made them for adjustment purposes.
Attachments
05_BF1-1.jpg
05_BF1-1.jpg (71.44 KiB) Viewed 6014 times
05_BF1-2.jpg
05_BF1-2.jpg (89.14 KiB) Viewed 6014 times


With best regards,
Dmitry Makolkin.
_____________________________________________________________________________
Solar continuum imaging with TAL-250K, Baader solar continuum and Barlow 1.4x
CaK with TAL-75R and Lunt calcium K-line B600
Camera: ZWO ASI174MM.
My solar images gallery: http://www.makolkin.ru/Gallery/SolarSys ... llery.html
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by dvmak »

Here is the transmission curve of the first blocking filter.
Peak transmission is about 50%.
Attachments
Block_1.PNG
Block_1.PNG (25.9 KiB) Viewed 6014 times
Last edited by dvmak on Sun Jul 06, 2014 7:36 pm, edited 1 time in total.


With best regards,
Dmitry Makolkin.
_____________________________________________________________________________
Solar continuum imaging with TAL-250K, Baader solar continuum and Barlow 1.4x
CaK with TAL-75R and Lunt calcium K-line B600
Camera: ZWO ASI174MM.
My solar images gallery: http://www.makolkin.ru/Gallery/SolarSys ... llery.html
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by dvmak »

The second filter is also tilted in the cell and is located just before the diagonal mirror. The cell is screwed into the 2" tube, so it's angular position is determined by the thread. This filer is also tilted in its cell.
One can see that the filter is rather rusted, but it did not degrade it's spectral transmission.
Attachments
06_BF2-1.jpg
06_BF2-1.jpg (83.71 KiB) Viewed 6014 times
07_BF2-2.jpg
07_BF2-2.jpg (78.52 KiB) Viewed 6014 times


With best regards,
Dmitry Makolkin.
_____________________________________________________________________________
Solar continuum imaging with TAL-250K, Baader solar continuum and Barlow 1.4x
CaK with TAL-75R and Lunt calcium K-line B600
Camera: ZWO ASI174MM.
My solar images gallery: http://www.makolkin.ru/Gallery/SolarSys ... llery.html
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by dvmak »

Here is the spectral transmission of the second block filter. Peak transmission is about 18%.
Attachments
Block_2.PNG
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With best regards,
Dmitry Makolkin.
_____________________________________________________________________________
Solar continuum imaging with TAL-250K, Baader solar continuum and Barlow 1.4x
CaK with TAL-75R and Lunt calcium K-line B600
Camera: ZWO ASI174MM.
My solar images gallery: http://www.makolkin.ru/Gallery/SolarSys ... llery.html
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by dvmak »

I have multiplied transmission data for two block filters to get the result of their together work.
Here is the graph for the most interesting spectral area. Peak transmission is about only 7.5%, filter's combination is rather dense.
Attachments
Block_1-2.PNG
Block_1-2.PNG (24.52 KiB) Viewed 6013 times


With best regards,
Dmitry Makolkin.
_____________________________________________________________________________
Solar continuum imaging with TAL-250K, Baader solar continuum and Barlow 1.4x
CaK with TAL-75R and Lunt calcium K-line B600
Camera: ZWO ASI174MM.
My solar images gallery: http://www.makolkin.ru/Gallery/SolarSys ... llery.html
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by dvmak »

Etalon is located behind diagonal mirror, rather close to the focal plane. It is not tilted in the cell.
The cell is screwed into the 1.25" tube.
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08_Ethalon01.jpg
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09_Ethalon02.jpg
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With best regards,
Dmitry Makolkin.
_____________________________________________________________________________
Solar continuum imaging with TAL-250K, Baader solar continuum and Barlow 1.4x
CaK with TAL-75R and Lunt calcium K-line B600
Camera: ZWO ASI174MM.
My solar images gallery: http://www.makolkin.ru/Gallery/SolarSys ... llery.html
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by dvmak »

Spectral transmission of the etalon is not of the resolution suitable for the evaluation of its performance at the CaK wavelength, but we can easily see the side transmission bands. These bands must be eliminated by block filters.

High resolution measurement was lost at my flash drive, so I have to make a new visit to my friend and make another measurement.

To be continued...
Attachments
Ethalon_wide.PNG
Ethalon_wide.PNG (42.79 KiB) Viewed 6013 times


With best regards,
Dmitry Makolkin.
_____________________________________________________________________________
Solar continuum imaging with TAL-250K, Baader solar continuum and Barlow 1.4x
CaK with TAL-75R and Lunt calcium K-line B600
Camera: ZWO ASI174MM.
My solar images gallery: http://www.makolkin.ru/Gallery/SolarSys ... llery.html
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by swisswalter »

Hi Dmitry

that matches what we have seen on my B1200. See old post in here. Very interesting your Analysis. Haven't you freed the Etalon. Mine is a square double stack


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by dvmak »

Hi Walter,

Yes, my etalon is square and double stack. Surprisingly, it is mounted between two metal details, one is fixed and another is rotating in thread - not a good solution for precise optical detail.


With best regards,
Dmitry Makolkin.
_____________________________________________________________________________
Solar continuum imaging with TAL-250K, Baader solar continuum and Barlow 1.4x
CaK with TAL-75R and Lunt calcium K-line B600
Camera: ZWO ASI174MM.
My solar images gallery: http://www.makolkin.ru/Gallery/SolarSys ... llery.html
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by mdwmark »

This is a good example for how the filter is blocked.
They used two ITF for the preblocking. Sorry to tell you the second filter has failed. You can see by the transmission. It is much lower. Worse case is, it will add scattering in the back ground and just get dimmer. Now when you look at the single cavity bandpass scan. Look at the wavelength it turn back on at. The ITF needs to be at OD4 before that wavelength. You can see it is petty close. Sometimes it doesn't get back down and this is the blue/green leak I talked about before on that other post.
If you find any yellow filter glass, that would be to cut down the brightness for visual use.
The most common failure with the bandpass is it will change in wavelength over time. They tend to move towards the shorter wavelength but I have also seen them move farther red. They will also become nonuniform with wavelength. But being that small that would probably not be seen as a big problem.
That was a good post
Mark W.


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by marktownley »

Good post indeed, and interesting observations thanks MarkW.


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by dvmak »

Hi Mark,

Thank you for comments and explanations, it's very interesting and good to know.

Here is a short story about astigmatism in my B600.
First I tried by setup this summer, and the very first images showed severe astigmatism - small sunspots formed thin lines in focals: intra and extrafocal images were lines with 90 degrees between them. I uploaded this video to Youtube, here it is:
http://www.youtube.com/watch?v=wMalS93AkAk

Today I made several tests using my camera and scope.
First, I tested the scope itself to be sure that it is OK. I used a bright reflection of Sun in the porcelain insulator on the roof of the nearly located building. Itra and extrafocal images were round, showing very small asymmetry, and I consider this as acceptable.

The second test was for the whole B600. Previously I removed diagonal mirror and substituted it with a tube of the same length, so there are three filters to be checked.
First block filter and etalon showed very minor distortion of the artificial star image, but the second block filter showed absolutely unacceptable distortions.
Now I have to find a substitution for it.


With best regards,
Dmitry Makolkin.
_____________________________________________________________________________
Solar continuum imaging with TAL-250K, Baader solar continuum and Barlow 1.4x
CaK with TAL-75R and Lunt calcium K-line B600
Camera: ZWO ASI174MM.
My solar images gallery: http://www.makolkin.ru/Gallery/SolarSys ... llery.html
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by dvmak »

Here are the pictures of the second block filter and etalon, I took them from the cells for making photos.
Attachments
10_Filters.jpg


With best regards,
Dmitry Makolkin.
_____________________________________________________________________________
Solar continuum imaging with TAL-250K, Baader solar continuum and Barlow 1.4x
CaK with TAL-75R and Lunt calcium K-line B600
Camera: ZWO ASI174MM.
My solar images gallery: http://www.makolkin.ru/Gallery/SolarSys ... llery.html
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by dvmak »

Here is a small video of refocusing: http://www.youtube.com/watch?v=nTsajRppzJ0


With best regards,
Dmitry Makolkin.
_____________________________________________________________________________
Solar continuum imaging with TAL-250K, Baader solar continuum and Barlow 1.4x
CaK with TAL-75R and Lunt calcium K-line B600
Camera: ZWO ASI174MM.
My solar images gallery: http://www.makolkin.ru/Gallery/SolarSys ... llery.html
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by sullij1 »

Thanks Dimtry, truly interesting stuff. Thanks.


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by sullij1 »

@ Mark Wagner - Mark in the previous posts you mentioed that the wave plates were sealed with a grease. What kind of grease? What is used? Is it commonly available?

Seperate question here:

Also we saw Walters previous pic of the etalon in another post. What is your assumption on the glass used in this sandwitch? SiO2? what is in between? A mica? or is that the grease causing that yellow tint we seein Dimtry's and walters photos? Perhaps a coating of some sort? If you had to assume a stack configuration for that small etalon we see. What do think the stack is?

SiO2>Mica>SiO2? or :
SiO2> some coating>SiO2?

(I assume the front and back of the etalon glass has a MgF2 or some other anti reflective coat.)

Thanks,

Joe


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by marktownley »

That second blocking filter is well and truly mashed Dmitry, didn't realise the condition it was in till seeing the additional picture you posted. You could use a Baader K-line or an Edmunds Optics 394nm bandpass filter in it's place.


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by swisswalter »

Hi Dmitry

thank you for sharing the test results. Omega optics hotmirror can work as a replacement too


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by dvmak »

Hi,

Thank you for comments and substitution advises.
I would like to test this Chinese company, here is a link to their site: http://www.mega-9.com/en/
They have 25.4mm as one of standard sizes, so I suppose that they can deliver the needed one.
It will be very interesting for me to check the actual filter after they deliver it to me.


With best regards,
Dmitry Makolkin.
_____________________________________________________________________________
Solar continuum imaging with TAL-250K, Baader solar continuum and Barlow 1.4x
CaK with TAL-75R and Lunt calcium K-line B600
Camera: ZWO ASI174MM.
My solar images gallery: http://www.makolkin.ru/Gallery/SolarSys ... llery.html
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by marktownley »

I think walter got a 393/4nm filter from them - maybe he can advise on what it was like?


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by swisswalter »

Hi Dmitry

yes a while a go we looked into the 394 nm filters they made. It is not narrow enough for the CaK line but could ma be work as a prefilter. There is a UV/VIS plot in one of the threads in here


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by swisswalter »

Hi Dmitry

here we go with freshly taken plots for comparison


Andover and mega-9 in overview

andover_and_mega_9_overview.jpg
andover_and_mega_9_overview.jpg (68.75 KiB) Viewed 5931 times



Andover and mega-9 close up

korea_andover_CaK_filterscloseup.jpg
korea_andover_CaK_filterscloseup.jpg (102.82 KiB) Viewed 5931 times


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by mdwmark »

To answer sullij question. I use a Dow Corning grease. Greases and oils like Cargille index matching oils work well. You can even use immersion oil that you use with a microscope. But they need to be sealed. You can use optical adhesive like Norland Products. Most of there's are UV cured. But they do make some that are not. They also have epoxy's for optical couplet. The advantage with the grease or oil is that you can take them apart if needed. The adhesive once it is cured that it.

I also want to point out when you are looking at bandpass filters you need to take inconsideration how it is put together.
If you look at the add in Edmund for bandpass filters. It has a hard coated and a standard design. What it doesn't tell you is that a standard design in meant for energy not visual. From the scan of the narrow bandpass you can see that it turn back on before 500nm. So you use a ITF to block it to at least 1000nm. In a standard design the two filters are cemented together. So you have two mirrors facing each other. Unless they are perfectly parallel you are going to create internal reflection that you have no way to get rid of.
Now if the bandpass is made so that all the coating are on one surface and the colored filtered glass is cemented on the back then you just tilt the filter like before.
Bandpass filters that are blocked to 800nm-1000nm maybe of this type. Any that are blocked to the Far IR in a cell are the first type.
This is why the ITF and the bandpass are on separate substrates.

The yellow you see in the bandpass is the color for a bandpass in the blue when you look through it. If you look at the reflected light it will look light magenta . As you move up the spectrum the reflection turn silver. Farther up the refection turn gold( Ha), at 700nm they start to look reddish gold.

So these are a single cavity filters cemented in float glass. If they where an etalon you would seen the other peaks from the scan. They are a soft coated filter. And I might add well done. I know Andover doesn't bother making single cavity at that wavelength. It takes a lot of layers and single cavity filters tend to drift in wavelength over time. The good side is that bandpass filters made in the blue tend to last longer then ones made at Ha.(soft coated)
Also if they where hard coated there would be no reason to have them mounted between glass.
I agree with Mark, look at the Baader K-line and check out Edmund's online filters. I saw that they where on sale for $70 for a 25mm filter.
Mark W.


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by sullij1 »

Thank you Mark for another one of your eloquent answers. That's why I ask ya! :lol:


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by mdwmark »

I said magenta, but I looked at an etalon and it was more light blue.
Mark W.


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by marktownley »

mdwmark wrote:To answer sullij question. I use a Dow Corning grease. Greases and oils like Cargille index matching oils work well. You can even use immersion oil that you use with a microscope. But they need to be sealed. You can use optical adhesive like Norland Products. Most of there's are UV cured. But they do make some that are not. They also have epoxy's for optical couplet. The advantage with the grease or oil is that you can take them apart if needed. The adhesive once it is cured that it.
Hi Mark. Thanks for this. Do you have a link you can give for the optical coupling gels please. I have had a good google around but wasn't really sure what I was looking for.


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by marktownley »

mdwmark wrote:I also want to point out when you are looking at bandpass filters you need to take inconsideration how it is put together.
If you look at the add in Edmund for bandpass filters. It has a hard coated and a standard design. What it doesn't tell you is that a standard design in meant for energy not visual. From the scan of the narrow bandpass you can see that it turn back on before 500nm. So you use a ITF to block it to at least 1000nm. In a standard design the two filters are cemented together. So you have two mirrors facing each other. Unless they are perfectly parallel you are going to create internal reflection that you have no way to get rid of.
Now if the bandpass is made so that all the coating are on one surface and the colored filtered glass is cemented on the back then you just tilt the filter like before.
Bandpass filters that are blocked to 800nm-1000nm maybe of this type. Any that are blocked to the Far IR in a cell are the first type.
This is why the ITF and the bandpass are on separate substrates.
I think this is a key point Mark in the ghosts / reflection issues that we have been observing, certainly food for thought for us all...


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by dvmak »

Hi Mark,

Thank you for input.
Could you please give a link to the sale for 70$ for a 25mm filter?


With best regards,
Dmitry Makolkin.
_____________________________________________________________________________
Solar continuum imaging with TAL-250K, Baader solar continuum and Barlow 1.4x
CaK with TAL-75R and Lunt calcium K-line B600
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My solar images gallery: http://www.makolkin.ru/Gallery/SolarSys ... llery.html
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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by marktownley »

I'm not convinced the sale is on anymore on these, not in the UK anyway...


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by Bob Yoesle »

Could you please give a link to the sale for 70$ for a 25mm filter?
Are these the filters you are referring to as being on sale (Anchor is a division of Edmund Optics)?:

http://www.anchoroptics.com/catalog/product.cfm?id=567

Note on these unmounted 394 nm 10 nm bandpass filters blocking is stated as "OD = 3.0, X-ray to 1.2μm," whereas the more expensive mounted hard-coated 394 nm 10 nm bandpass is "OD4 200-1200 nm."

http://www.edmundoptics.com.tw/optics/o ... ers/65-131

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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by Valery »

Bob Yoesle wrote:
Could you please give a link to the sale for 70$ for a 25mm filter?
Are these the filters you are referring to as being on sale (Anchor is a division of Edmund Optics)?:

http://www.anchoroptics.com/catalog/product.cfm?id=567


Bob
Too bad transmission at the 393nm.

From the site description:

Blocking: OD = 3.0, X-ray to 1.2μm
Min. Peak Transmission: 334-400nm CWL = 25%
405-647nm CWL = 40%
650-1064nm CWL = 50%


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by Bob Yoesle »

Yeah, I noticed that too Valery. But on the other hand, if the scatter is due to over saturation of the CCD sensor, less light and a longer exposure may be what we need to fix it:
Smear Explained

On the interline transfer CCDs used in many Point Grey cameras, each pixel consists of a light sensitive area, called the photosensor, and a light-shielded area, called the vertical transfer register. The vertical transfer register is used to shift the charge out of the photosensor and off of the sensor. Although vertical transfer cells are approximately 100,000 times less sensitive than the light sensitive region, photons may still tunnel into this area, especially when exposed to very bright light. This tunneling, or leaking, is the source of smear.

During image readout, image pixels are shifted vertically downard, row by row, through the vertical transfer cells to the readout register. If there is any leakage of charge into an area of the vertical transfer register, it will be picked up and shifted downward, so that every pixel above and below the area will contain this extra charge. The result is a relatively bright vertical stripe across the entire image.

Effect of Integration Time and Lens Aperture on Smear

Smear is often more noticeable when using very short (microsecond) shutter times. This is because the amount of charge collected in the light-sensitive area of the CCD varies based on exposure time, whereas the amount of charge that collects in the vertical transfer register is based on the sensor readout rate, which is a constant. With short exposures, the ratio of time integrating in the photosensor to time integrating in the vertical transfer is reduced. This reduced ratio may exacerbate smear.

Another factor that affects smear is the angle that light hits the sensor. Many CCDs use on-chip microlenses that cover each pixel in order to increase sensitivity. When light hitting the sensor is not highly collimated (which is often the case with wide angle lenses), light can be refracted by the outer edges of the lens in such a way that it hits the light-shielded portions of the CCD.

Reducing Smear

Smear may be addressed by reducing the source of bright light hitting the sensor, reducing the aperture, and using a lens that more effectively collimates light. Other, more specific, measures for reducing smear include the following:

Increase shutter (integration) time. This will increase the amount of time light is collected in the photosensors relative to the time in the vertical transfer register.
Bob


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by swisswalter »

Bob Yoesle wrote:Yeah, I noticed that too Valery. But on the other hand, if the scatter is due to over saturation of the CCD sensor, less light and a longer exposure may be what we need to fix it:
Bob

Hi Bob

thank you very much. I guess thats it we should look for. I'm down to 0,4 ms exposure time ;). I guess 5 to 15 ms should be o.k.


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by marktownley »

I'm just uploading some videos to youtube... There may be a different explanation...


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by swisswalter »

Hi Mark

thank you very much for your anouncement. Wating for the link ;)


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by marktownley »

oops, sorry, I put it in the cak pst mod thread ;)


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by swisswalter »

Hi Mark

no problem, found it


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by mdwmark »

The blocker that I said was $70 was just on Edmunds catalog online. I went to bandpass filters and it had them on sale.
The grease I use cost to much and it comes in 1# jars. Before Dow came out with there grease we used Cargille Immersion oil type A.
You can find it at Cargille.com. They make small amounts that doesn't cost much. The only problem is it is sticky and to clean it off the glass you need something like paint thinner. We uses Toluene but I don't think that a good idea any more. Xylene is a better choice. Lately I tried just mineral oil, it doesn't smell and it seem to work. Then Acetone , then alcohol to finish.
Norland Products web is www.NorlandProducts.com. and Andover sell an epoxy that they use. I am sure you could find other epoxy's like Andover uses.
Using the wrong designed filter.
Andover had sent me a batch of blockers that they had cemented together. So I couldn't take them apart. So I tried them in the optical stack. Everyone had problems with small secondary reflection. It ranged from only a small extra lim to a half the reflection of the solar image. They all got sent back.
If you are using hard coated filters with out an AR on the back then(like before you don't want to attach anything to the AR surface except air space), make sure you are on the glass side. If you oil/grease/epoxy the coated side you will drop the transmission of the filter.
Just a little more information
Mark W.


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by swisswalter »

Hi Mark W.

thank you very much for the additional information


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Re: My Lunt B600 CaK diagonal anatomy and spectral curves

Post by marktownley »

Yes, thanks for the info Mark. All the filters i'm working with are AR coated, so not sure how I could use the immersion oils...

Here are the trouble some reflections if you have any suggestions as to their origins (and cure!) http://solarchat.natca.net/viewtopic.ph ... 50#p123619


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