Getting rid reflected light in C11 CAK imaging

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yltansg
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Getting rid reflected light in C11 CAK imaging

Post by yltansg »

Hi all,

To recap, the best C11 CAK image was obtained using a TV x2.5 powermate + CAK PST yellow filter. Unfortunately it has a reflected light:
Image

Following up on the suggestions from friends I have tested several ways of placing the powermate and tilt adjusters. Unfortunately they all didn't work.

The last configuration that I will be testing is to place the TV PM nearest to the output of the C11:
Image

Unfortunately I found out that my TV x2.5 PM was the older version. The newer version TV x2.5 powermate has arrived:

Image

Unfortunately the weather is not cooperating. While waiting for good weather I am thinking of removing both the 2 ERFs in the nosepiece of the LUNT CAK module. I am assuming that the 2 glass pieces are the 2 ERFs. So far I have removed the one furthest away from the diagonal.

Image

The purpose of removing both ERFs in the LUNT CAK Module is to have more light reaching the camera, assuming that the D-ERF has provided sufficient protection. With this mod, I should be able to set the exposure to less than 5msec to freeze the seeing.

My question is: Should I remove both ERFs in the nosepiece?

Alfred
Last edited by yltansg on Sat Jun 20, 2020 2:00 pm, edited 2 times in total.


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MalVeauX
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Re: Getting rid reflected in C11 CAK imaging

Post by MalVeauX »

Alfred,

Is your primary D-ERF tilted at all? If not, I would add a small 1 degree tilt to it via rubber gasket under 1/2 of the filter inside the holding cell. It should handle your reflection.

I too am curious about the innards of a Lunt module in terms of what is in front of the actual narrowband filter in case I disassemble mine to add a 2nd filter for a double-stack.

Very best,


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Re: Getting rid reflected in C11 CAK imaging

Post by yltansg »

MalVeauX wrote: Sat Jun 20, 2020 1:32 pm Alfred,

Is your primary D-ERF tilted at all? If not, I would add a small 1 degree tilt to it via rubber gasket under 1/2 of the filter inside the holding cell. It should handle your reflection.

I too am curious about the innards of a Lunt module in terms of what is in front of the actual narrowband filter in case I disassemble mine to add a 2nd filter for a double-stack.

Very best,
Hi Marty,

I will try tilting the D-ERF as suggested to see its effect.

This is how the 2 filters look like:

Image

Image

Are these 2 filters the 2 ERFs and I can remove them totally since I have an ARIES D-ERF?

Or is one of them a CAK filter that I need to retain? One of them looks "yellowish" under white light.

Alfred


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Re: Getting rid reflected in C11 CAK imaging

Post by Valery »

yltansg wrote: Sat Jun 20, 2020 10:50 pm
MalVeauX wrote: Sat Jun 20, 2020 1:32 pm Alfred,

Is your primary D-ERF tilted at all? If not, I would add a small 1 degree tilt to it via rubber gasket under 1/2 of the filter inside the holding cell. It should handle your reflection.

I too am curious about the innards of a Lunt module in terms of what is in front of the actual narrowband filter in case I disassemble mine to add a 2nd filter for a double-stack.

Very best,
Hi Marty,

I will try tilting the D-ERF as suggested to see its effect.

This is how the 2 filters look like:

Image

Image

Are these 2 filters the 2 ERFs and I can remove them totally since I have an ARIES D-ERF?

Or is one of them a CAK filter that I need to retain? One of them looks "yellowish" under white light.

Alfred
Alfred,

I believe that these two filters work also as wide CaK filter(s).


Valery.


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Re: Getting rid reflected in C11 CAK imaging

Post by yltansg »

Valery wrote: Sun Jun 21, 2020 1:52 am
Alfred,

I believe that these two filters work also as wide CaK filter(s).

Valery.
Thanks for your feedback. One of them has a yellowish tint:

Image

While the other doesn't:

Image

As I am doing purely imaging and have the ARIES D-ERF, I will try imaging with the LUNT CAK diagonal (minus these 2 filters) and a yellow PST CAK filter and see its performance. Later I will put in the filter with yellowish tint and find out how it perform with the PST CAK filter.

Alfred


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Re: Getting rid reflected light in C11 CAK imaging

Post by marktownley »

You will need one of them Alfred, the goldish one, it's that colour to reflect the blue light. The all important CaK filter is the 12mm one in the nosepeice. It may well be that you need both of the larger filters in depending how wide the passband is of Valerys DERF.

The front two filters are just sub aperture ERFs. There will be 2 to increase the out of band blocking.

You would do well to have a good search in the mods section, myself and Swisswalter did all this years ago, so the information already is out there. Walter scanned the transmission of the filters etc.


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Re: Getting rid reflected light in C11 CAK imaging

Post by Montana »

The reflection is not from the front ERF (Aries), I still get the reflection in white light when using Baader Solar film!

Alexandra


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Re: Getting rid reflected light in C11 CAK imaging

Post by yltansg »

Montana wrote: Sun Jun 21, 2020 11:47 am The reflection is not from the front ERF (Aries), I still get the reflection in white light when using Baader Solar film!

Alexandra
Thanks Alexandra for that piece of information. It rained for extended period this weekend. Hope to test this configuration:

Image

Even if this fails, I still can use the 2" TV x2 PM :)

Waiting for clear skies.

Alfred


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Re: Getting rid reflected light in C11 CAK imaging

Post by yltansg »

marktownley wrote: Sun Jun 21, 2020 9:15 am You will need one of them Alfred, the goldish one, it's that colour to reflect the blue light. The all important CaK filter is the 12mm one in the nosepeice. It may well be that you need both of the larger filters in depending how wide the passband is of Valerys DERF.

The front two filters are just sub aperture ERFs. There will be 2 to increase the out of band blocking.

You would do well to have a good search in the mods section, myself and Swisswalter did all this years ago, so the information already is out there. Walter scanned the transmission of the filters etc.
Thanks Mark for the very useful information in the Mods section. I will look it up.

Alfred


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Re: Getting rid reflected light in C11 CAK imaging

Post by JochenM »

Very interesting information. Good luck with the tests, Alfred (will keep an eye out for the results).


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