ERF questions

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Pablito
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ERF questions

Post by Pablito »

Hi Guys,

I am going to organise a couple of large ERFs. I will buy Schott RG630 glass and will give it for polishing. It will have at least 1/4 lambda surface accuracy.
The questions are:
1. How important is to coat AR coatings, what hapens if I don't have it on ERF?
2. Is IR-cut coating needed if I will use 2" Baader UV/IR-cut filter in diagonal?
3. Will BelOptic UV/IR-cut be better than Baader in viewing and imaging? Oliver's filter has lower transmission ir h-alpha (75%) than Baader (over 90%). In the other hand IR is cut very far (to 5000nm)


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marktownley
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Re: ERF questions

Post by marktownley »

Hi there.

Without an AR coating you will get reflections / ghosts. To answer questions 2 & 3 what aperture are you planning to work at here?


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Re: ERF questions

Post by swisswalter »

Hi Pawel

my dream is a 8" triband like filter ;)


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: ERF questions

Post by pedro »

There is one for sale in UK B&S (85mm)

http://www.astrobuysell.com/uk/propview.php?view=80336

- Diameter 85mm (82mm free aperture)
- Thickness 8.25mm
- Schott N-BK7
- Triple bandpass coating (transmission in Ca, Continuum and Ha)
- Substrate precise polished
- New and unused without cell
- Made in Germany


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Pablito
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Re: ERF questions

Post by Pablito »

Hello,

Mark, I plan to buy 165x165mm glass and cut it to maximal diameter - probably 150-160mm. ERF will work with 100-150mm refractors.

Walter, no chance at this time, sorry...

Thanks Pedro, but I am buying more than 5pcs of glass to make ERFs for me and my friends. If anybody wants to join me with the project, please let me know ;)


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Re: ERF questions

Post by swisswalter »

Hi Pedro

thank you very much. I have an 85 mm, I wish a 200 mm ;)


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: ERF questions

Post by Valery »

swisswalter wrote:Hi Pedro

thank you very much. I have an 85 mm, I wish a 200 mm ;)
Walter, what is the telescope you will use such 200mm filter with?

We can make such filters, but better to have 5 or more persons who want one.

Valery.


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Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.
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Re: ERF questions

Post by swisswalter »

Hi Valery

the filter should work with my TMB203/1800 ;)


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: ERF questions

Post by Pablito »

Can anyone help with question 2 and 3?


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Re: ERF questions

Post by marktownley »

Regards question 2&3 I guess you just got to try it an see!

The Beloptik UV/IR cut is on a KG3 substrate so this will offer IR protection to OD2.5 all the way up to 2500nm, I think this is the one I would go for. However KG3 blocks by absorption and my only concern is a 6" lens, even with RG630 infront may pass too much IR and may thermally overload the KG3 causing it to crack / shatter - but like I said before, this is just a 'maybe' - all uncharted territory!


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Re: ERF questions

Post by Valery »

swisswalter wrote:Hi Valery

the filter should work with my TMB203/1800 ;)
Heh heh! When have you bought such a beast?


"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.
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Re: ERF questions

Post by Pablito »

Mark, looking at Lunt LS152 and internal ERF size (ca.50-70mm) it should be ok if placed as near to the objective as possible to make more effective aperture work/absorb.
What do you think?


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Re: ERF questions

Post by swisswalter »

Valery wrote:
swisswalter wrote:Hi Valery

the filter should work with my TMB203/1800 ;)
Heh heh! When have you bought such a beast?
Hi Valery

a long time ago. It is very seldom used


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: ERF questions

Post by Valery »

Pablito wrote:Mark, looking at Lunt LS152 and internal ERF size (ca.50-70mm) it should be ok if placed as near to the objective as possible to make more effective aperture work/absorb.
What do you think?
Internal filters must be properly installed. Mark know well this problem with his CaK complicated rig.

Shortly, an internal flat glass filter should have some inclination to escape the reflections. However each such inclination will introduce an astigmatism in the final image.


"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.
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Re: ERF questions

Post by Valery »

swisswalter wrote: It is very seldom used
How this is possible? To have such a great refractor and keep it in it's box???? I can't understand this.
I can only imagine a high resolution photos you can make with such a telescope, especially in CaK!!!

Walter, give it a full use!


"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.
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Re: ERF questions

Post by swisswalter »

Valery wrote:
swisswalter wrote: It is very seldom used
How this is possible? To have such a great refractor and keep it in it's box???? I can't understand this.
I can only imagine a high resolution photos you can make with such a telescope, especially in CaK!!!

Walter, give it a full use!

Hi Valery

time, sunshine and a good seeing are required. Not very often all 3 fall together


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: ERF questions

Post by Valery »

swisswalter wrote:
Valery wrote:
swisswalter wrote: It is very seldom used
How this is possible? To have such a great refractor and keep it in it's box???? I can't understand this.
I can only imagine a high resolution photos you can make with such a telescope, especially in CaK!!!

Walter, give it a full use!

Hi Valery

time, sunshine and a good seeing are required. Not very often all 3 fall together
Hi Walter,

In the case of permanent installation (dome, roof-off) you will have enough time, sunshine and starry sky at nights. This is a key - the possibility to use the instrument any time you wish/can.


"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.
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Re: ERF questions

Post by Pablito »

Hi Valery,

As far as I remember, you use LS50 in your 150mm system without additional ERF, right? If so, 2" IR on KG3 used in conjuction with front RG630, should be enough.
Can you please comment?


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Re: ERF questions

Post by Valery »

Pablito wrote:Hi Valery,

As far as I remember, you use LS50 in your 150mm system without additional ERF, right? If so, 2" IR on KG3 used in conjuction with front RG630, should be enough.
Can you please comment?
The ERF in my system is on the first lens component. First (front) surface is visible spectrum filter (allows CaK and Ha) and the back surface is IR cut filter. No front mounted ERF as I said.


Valery.


"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.
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