Daystar T-Scanner disassembling

[Bastelhannes]

Hi folks,

I found on a long forgotten shelf an old Daystar T-scanner.

01-01.jpg (128.63 KiB) Viewed 5366 times

I want to use it for double stacking. But unfortunately it only produces foggy pictures (not to confuse with unfocused).

Therefore I just disassembled it.

01-02.jpg (85.91 KiB) Viewed 5366 times

(forbidden Oreo cookie)

01-03.jpg (104.77 KiB) Viewed 5366 times

Some things were interesting:
- inch screws..
- there is a lot of oil around the optical parts
- I thought the ITF could be rusted. Is there a ITF? Which part could create fog?

[Bastelhannes]

I found some drawings:

02-01.jpg (122.47 KiB) Viewed 5365 times

Source: https://www.researchgate.net/publicatio ... XAMINATION


White color shows the FP etalon with dielecrtric mirrors on both sides — the heart of DayStar filters. Yellow — antireflection protective glasses that prevent the stack from external influences.
Pink shows IF with 10 Å passband that blocks the mica etalon adjacent or- ders of interference.
Red — a color glass that, in turn, blocks the wings of the IF transmittance profile thus isolating the required spectrum region.
Green — circular polarizers that have two functions. First, they damp off-band reflections in the stack when those occur be- tween etalon and other filters. Second, since mica has birefringence, which is manifested in occurrence of ad- ditional spectrum maxima, the polarizer damps one of two rays — ordinary or extraordinary.
Purple shows a heat-reflecting filter. This can be a MDM filter (met- al/dielectric/metal), which blocks IR radiation to 4000 nm, transmitting Нα or another wavelength selected.

Looks like something I should not disassemble further...

[marktownley]

Always nice to see an disassembly thread like this

[Bastelhannes]

Yes.. but still no clue where the fog is coming from...

[Bastelhannes]

Okay...

Threw away the collimation lens of the daystar and replaced it by a 3x telecentric barlow from Explorer Scientific (MEADE). Now the image is crystal clear, but very very dim...

Sigh.. long way to go

[vkx86]

Nothing is like taking things apart...
That oil is index fluid - maybe it changed it's properties with time, thus causing fog.
Or it simply leaked outside the stack leaving optical surfaces without it.

[Bastelhannes]

Thank you vkx86!

What do you think? Disassemble the optical parts? I have a screwdriver and hammer at hand...

[vkx86]

Thank you vkx86!

What do you think? Disassemble the optical parts? I have a screwdriver and hammer at hand...

Me thinks - absolutely not, do not touch the stack!!!
I think you reached the edge, I would send the filter to DayStar at that stage - the most precious part in that stack is the mica sheet, it maybe a very good one with some overhaul (such as oil replacement) done on it

BTW, I like your sig

[christian viladrich]

Okay...

Threw away the collimation lens of the daystar and replaced it by a 3x telecentric barlow from Explorer Scientific (MEADE). Now the image is crystal clear, but very very dim...

Sigh.. long way to go

Hello,
Thanks for sharing these pictures.
What do you mean by "collimation lens" ? There is no such thing in a DayStar filter.

[Bastelhannes]

Hi Christian,

there ist one collimation lens in front of it. FL approximately 200 mm.

[christian viladrich]

Hi Christian,

there ist one collimation lens in front of it. FL approximately 200 mm.

Maybe we are not talking about the same thing.
In the photo of the stack you have attached, there are 7 optical elements (without the two polarizers). All the elements are stuck together with optical grease. Do you mean one of these elements is a collimating lens ?

[Bastelhannes]

You are correct Christian,

in the Oreo cookie stack there is no collimator.

I am going to send this fine piece to Daystar to geht teh right pressure on the Mica plate...

[Bob Yoesle]

The pink filter in the diagram is the order selection blocking filter, it generally has a gold reflective coating. The red filter is an RG630 or thereabouts, it also has the same characteristics of the Coronado ITF with sliver layers to block the longer IR wavelengths. Either or both of them can deteriorate over time. See here for what you might be in for.

[Bastelhannes]

After some testing in the sun (unfortunately it is very cloudy today) I discovered the image is crisp sharp now, but very dim. It looks like, the CWL has shifted. Daystar states on their website:

"The Fabry- Perot Etalon is an excruciatingly fragile element. Housed deep inside your filter, it must remain undisturbed or it could experience damage. Damage occurs when elements are separated, twisted, pulled or slid against one another; or even the release of tension in opening the filter assembly. That motion causes sections of the coating to slide, clump or vein in effects as light as crackling or severe as complete coating failure. The etalon is the most delicate, fragile and expensive part of the DayStar Filter. Simply releasing tension from your housing puts your etalon at risk of permanent damage. A damaged etalon crystal will deliver off-band and/or uneven width or wavelength light throughout the image. It is not possible to repair a damaged etalon crystal. It must be replaced."

Looks like mine is offband now. I will try to increase the tension....

[christian viladrich]

There is no relation at all between the pressure of the optical oil and the CWL of the etalon. Indeed, there is no pressure applied to the optical oil.
The elements of the stack are stuck together by the action of superficiel tension. Nothing more.
The CWL of the etalon is tuned by tilting the stack. This is how T-scanner are tuned. Have you tried this ?
Do not try to apply any pressure on the stack. This is the best way to destroy the etalon.
Remember that the "etalon" is just a very thin sheet of mica coated on both side. It is very fragile. It is protected by the other optical elements of the stack: RG630, BF10A, etc.

[mdwmark]

Hi Group,
from the ser# it was sent out 11/1993.
It would be a good idea to put it back in the cell with the pressure of the o-rings. What can happen is that taking the pressure a way you can get a grease separation . This separation can happen anywhere in the filter stack. It can also happen with the etalon windows. All the other places are easy to regrease. But when you pull the windows off the etalon . You will be holding your breath hoping it comes off clean. If it doesn't and you have to peel it off the other window. You risk cracking the etalon.
The T-Scanner were etalon that came out to long for a heated oven. So the peak can be on Ha anywhere from 30C to 5C. depending where it was going to be sent. But most were +1 Ang in the red. I see your saids 24C, that is a good place for most of the time of the year.
The optical grease does not run, The only grease you will find on the outside of the filter stack would have been from the compression of the o- rings.
Mark W.

[astroshot]

Interesting that your T-Scanner states an operating temp.
For temp, mine just says 'Amb'.
My Serial number is TS1-600
IIRC, this references the year of production in some way??

[mdwmark]

The ser#on the originals were month/year, as for the temperature ,I liked to put a real # so you knew were it would work best ,Del like to put Amb,The new Daystar probably changed it
Mark W

[Bastelhannes]

Mark,

Thank you for the email you have send me. But unfortunately I never got an answer to my response or my private message here. I wanted to send the Quark stack to you; but unfortunately I am in hospital for the next 6-8 weeks.

Would it be possible to discuss this afterwards?

Karsten

[Ljungmann]

I had a 0.7Å T-scanner years ago just to have some fun and see how it did work compared to my old ATM.
Your story reminds me about a dealer in my country who thought it was a piece of cake to repair an ATM filter, and it is now an expensive door stopper.
Let Mark have a look when you are back.
Good luck with it all!!