PST etalon (or similar) in a telecentric beam

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Re: PST etalon (or similar) in a telecentric beam

Post by swisswalter »

Hi Mark

dead on. At least not for the moment ;-)


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Re: PST etalon (or similar) in a telecentric beam

Post by Merlin66 »

Mark, et al,
I'm really having difficulty here....why would the "sweet spot etc." be better at f40 (or so) compared with say, the fully collimated beam directly from the Sun (i.e. an external etalon).
The field angle is minimal, equivalent to around f 230. (1/tan 0.25 deg)
Why is this so......


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Re: PST etalon (or similar) in a telecentric beam

Post by swisswalter »

Hi Ken

I have to wait for Mark to have an answer to your question :oops:


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Re: PST etalon (or similar) in a telecentric beam

Post by marktownley »

Merlin66 wrote:Mark, et al,
I'm really having difficulty here....why would the "sweet spot etc." be better at f40 (or so) compared with say, the fully collimated beam directly from the Sun (i.e. an external etalon).
The field angle is minimal, equivalent to around f 230. (1/tan 0.25 deg)
Why is this so......
With an external etalon the field angle is indeed 'minimal', however with the telecentric design the field rays appear to come from infinity (not 150,000,000km as with an external etalon) and so are perpendicular to the image plane and parallel to the optical axis, as a result there is no sweet spotting with a telecentric. There are no field angles with a telecentric.

Also, you wouldn't have much aperture with a PST etalon mounted externally ;)


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Re: PST etalon (or similar) in a telecentric beam

Post by Merlin66 »

""the off axis beam arrive at the image plane with the same angular geometry as
the axial rays"" -Baader TZ webpage
OK I think we are saying the same but different...
The angular geometry of the solar disk will still give a "field angle" - around +/- 0.25 deg., but there will be no additional "instrument" angle(??)....
I'm sure a similar result (re Marcon's positive lens collimator) would be achieved if we could find an aberration free collimating system.
In the meantime the TZ system looks the most promising......


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Re: PST etalon (or similar) in a telecentric beam

Post by Merlin66 »

http://www.edmundoptics.com/technical-r ... entricity/

In the mark up #1 is the prime image of the solar disk, #2 is the etalon in position behind the telecentric lens assembly and #3 shows the angles into the etalon....
Attachments
Edmund_telecentric_mark-up.JPG
Edmund_telecentric_mark-up.JPG (26.65 KiB) Viewed 6933 times


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Re: PST etalon (or similar) in a telecentric beam

Post by marktownley »

Edmunds has some useful stuff. The video is interesting, just wish it didn't have the annoying music in the background. Will be ordering the TZ4 next week, so that should herald weeks of cloud and rain, but as soon as the weather gods have forgotten something astronomical I will report back on how I get on with it. :)


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Re: PST etalon (or similar) in a telecentric beam

Post by swisswalter »

Hi Mark

good luck on the TZ4. I had yesterday some first try. It works fine, but I had not enough time to add the blocking filter. Just ended the try with WL.


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Re: PST etalon (or similar) in a telecentric beam

Post by Valery »

marktownley wrote:Edmunds has some useful stuff. The video is interesting, just wish it didn't have the annoying music in the background. Will be ordering the TZ4 next week, so that should herald weeks of cloud and rain, but as soon as the weather gods have forgotten something astronomical I will report back on how I get on with it. :)

TZ is not the best possible solution. It is just the most universal solution.
Last edited by Valery on Tue Feb 06, 2018 3:02 am, edited 1 time in total.


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Re: PST etalon (or similar) in a telecentric beam

Post by marktownley »

I think you should send me a prototype to test Valery :D :bow2

I also rediscovered this article on telecentrics and etalons, and also on it a design for a telecentric for a 100mm f10 frac... Interesting... http://www.sonnen-filter.de/TZS/index-tzs.html


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Re: PST etalon (or similar) in a telecentric beam

Post by Merlin66 »

Good "re find" Mark!
I also had that saved but had "lost" it.


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Re: PST etalon (or similar) in a telecentric beam

Post by swisswalter »

Hi Mark

very interesting read. I can't wait to use the TZ4/LUNTLS50 combo


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Re: PST etalon (or similar) in a telecentric beam

Post by Valery »

Looking for results with the LS50F in a telecentric TZ4!
Last edited by Valery on Tue Feb 06, 2018 3:04 am, edited 1 time in total.


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Re: PST etalon (or similar) in a telecentric beam

Post by swisswalter »

Hi Valery

I guess you are spot on judging on my first experience with the TZ4/LuntLS50F Combo. What has to be done to get it narrower ?


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Re: PST etalon (or similar) in a telecentric beam

Post by marktownley »

Valery wrote:In such telecentric system the band wide will be about 0.85 - 0,9A which is significantly wider than in a native scheme with F/109 beam (in front of an objective).
The benefit is that it works with a much larger telescope = higher resolution. PST mod is much better.
The sweet spot effect of the PST mod just frustrates me now though Valery, for me it's a case of improving the matter, while hopefully retaining the pst etalon, even if the collimating optics are not kept. How would you improve the sweet spot issue?


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Re: PST etalon (or similar) in a telecentric beam

Post by Valery »

marktownley wrote:
Valery wrote:In such telecentric system the band wide will be about 0.85 - 0,9A which is significantly wider than in a native scheme with F/109 beam (in front of an objective).
The benefit is that it works with a much larger telescope = higher resolution. PST mod is much better.
The sweet spot effect of the PST mod just frustrates me now though Valery, for me it's a case of improving the matter, while hopefully retaining the pst etalon, even if the collimating optics are not kept. How would you improve the sweet spot issue?
Mark,

We all know well the rule: there is no free lunch. Right? In the PST mod for higher resolution we should pay. And we pay - losing the useful field size.
The only method to solve the sweet spot problem is to pay money - buying a larger etalon (and blocker). As lower the ratio Dob/Det - as more even the field of view is.
Without additional money investment and without band wide increasing, the only method to get rid of a sweet spot is to use a larger scale - so the camera chip will be fully within a sweet spot. Getting rid of a sweet spot in the case of no money investment still has it's price - band wide increasing with all these contrast losing.



Walter,

The only method to get the narrowest possible band wide with a front air-spaced etalon ( Lunt LS35F, LS50F and LS60F) is to mount it in a collimated beam.
To narrow the band wide in a tele centric scheme you need to add another etalon and you will back to it's native 0,7A, but will have problems with reflections (ghosts) and banding. The useful FOV within sweet band will be significantly smaller.
Last edited by Valery on Mon Apr 21, 2014 7:38 am, edited 1 time in total.


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Re: PST etalon (or similar) in a telecentric beam

Post by swisswalter »

Hi Valery


thank you very much for your explanation. That sounds frustrating


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Re: PST etalon (or similar) in a telecentric beam

Post by Merlin66 »

http://articles.adsabs.harvard.edu/cgi- ... etype=.pdf
also
http://adsabs.harvard.edu/full/2006ASPC..358..155F
The above makes very interesting reading - collimated v's telecentric....

For completeness in this thread I copy a recent message from Valery re the D/d ratio...
""
1. Acceptance angle for a front mounted etalon is about 1 degree or two solar disk diameter. In the telescopes with collimated beam we have increased angle of incoming light. The magification is D/d where "D" is the objective diameter and "d" is collimator diameter. So, for a telescope with D/d=2 we have 2x smaller acceptance angle on the sky. About 1/2 degree or one solar diameter. With the D/d ratio increasing the acceptance angle on the sky will proportionally decreased. For wider band pass the acceptance angle is larger, for narrower band pass the acceptance angle is smaller.
For D/d=3 the acceptance angle is somewhat smaller than a solar disk, but because we tolerate some bandpass increasing and shifting, it will work despite that D/d is more than 2. But 3 is the limit and works only if you have etalon 0.7 - 0.8A and which does not require a tilt for a given conditions (barometric pressure and temperature).
""
The search for the Holy Grail continues....


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Re: PST etalon (or similar) in a telecentric beam

Post by swisswalter »

Hi Ken

thank you very much. That gives a good sunday reading in the rain


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Re: PST etalon (or similar) in a telecentric beam

Post by marktownley »

A couple of very interesting papers there Ken, thanks for posting. Each method (telecentric & collimated) both have their pros and cons - no best of both worlds scenario. A good learning experience though.

The telecentric option could be good for mounting a PST or other external etalon in a setup with a front mounted etalon to double stack... Would tighten up the bandpass of the front mounted etalon a bit, but still keep the even field - problem is working at at least 3x the native focal length of the scope (without using a reducer).


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Re: PST etalon (or similar) in a telecentric beam

Post by fjabet »

I use this set up with the HaT telescope with very good results.
The HaT delivers F/10 flat correctged field, then our telecentric amplifier bring the F/D at 27,59 (more or less 1° marginal angle) with less than 10e-2° field angle at 0,25".
I used the following etalon with very good results :

- Daystar Ion 0,5A
- Daystar Quantum PE 0,6A
- PST single (single good etalon without its collimating lenses of course) +BF15
- PST DS + BF15 (very nice, but rather dim and with an uneven illumation, for visual only)
- Lunt LS50Fha + BF30 (very good, best bang for the bucks, that is my new reference design)

In all the cases the bandwidth was as expected without ANY soft spot, except some vignetting and banding in the PST DS due to less than perfect second PST. So to me the F/D >27 image side telecentric design is just the best solution when compared with the soft spot plagued collimated PST mod, unless using the right elalon size.
But you need a real telecentric, I'm not sure that the Tevevue falls in this category.
And remember that a telecentric lens design depends on the aperture, the FL AND the design (a 200/2000 SCT has more field angle than a 200/2000 doublet for example).

Frédéric.


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Re: PST etalon (or similar) in a telecentric beam

Post by Valery »

fjabet wrote:
a 200/2000 SCT has more field angle than a 200/2000 doublet for example).
Can you prove this statement with math?

Thanks.

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Re: PST etalon (or similar) in a telecentric beam

Post by Valery »

fjabet wrote:I use this set up with the HaT telescope with very good results.
The HaT delivers F/10 flat correctged field, then our telecentric amplifier bring the F/D at 27,59 (more or less 1° marginal angle) with less than 10e-2° field angle at 0,25".
I used the following etalon with very good results :

- Daystar Ion 0,5A
- Daystar Quantum PE 0,6A
- PST single (single good etalon without its collimating lenses of course) +BF15
- PST DS + BF15 (very nice, but rather dim and with an uneven illumation, for visual only)
- Lunt LS50Fha + BF30 (very good, best bang for the bucks, that is my new reference design)

In all the cases the bandwidth was as expected
OK, can you be more specific with your expectations in each of these cases - #3 and #5? And how have you measured them?


Thanks,

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Re: PST etalon (or similar) in a telecentric beam

Post by fjabet »

Valery wrote:
fjabet wrote:
a 200/2000 SCT has more field angle than a 200/2000 doublet for example).
Can you prove this statement with math?

Thanks.

Valery.
200/2000 doublet : 2,4° at 25', half sun field angle
203mm edgeHD : 2,8°.

Calculated with Zemax MF RAID.


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Re: PST etalon (or similar) in a telecentric beam

Post by fjabet »

Valery wrote:OK, can you be more specific with your expectations in each of these cases - #3 and #5? And how have you measured them?


Thanks,

Valery.
I don't have a HR spectrophotometer. Nevertheless the PST etalon behaves like in its nominal full PST outfit, and by the way this one is very good, it is close to a single stack Coronado SM front filter. I use it also for imaging with the HaT and it is better than my Quantum for this application.

In the case of the Lunt it was Oliver's set up and the result was pretty much the same as my Quantum.

I have seen in a lot of Ha intruments over thge years and I can judge quite well the filter quality.


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Re: PST etalon (or similar) in a telecentric beam

Post by marktownley »

What sort of usable field of view can you get out of the SCT system Frederic?


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Re: PST etalon (or similar) in a telecentric beam

Post by Valery »

fjabet wrote:
Valery wrote:OK, can you be more specific with your expectations in each of these cases - #3 and #5? And how have you measured them?


Thanks,

Valery.
I don't have a HR spectrophotometer. Nevertheless the PST etalon behaves like in its nominal full PST outfit, and by the way this one is very good, it is close to a single stack Coronado SM front filter. I use it also for imaging with the HaT and it is better than my Quantum for this application.

In the case of the Lunt it was Oliver's set up and the result was pretty much the same as my Quantum.
If there any chances you show us the photos you take with this PST etalon in it's normal configuration (say with refractor F/10) and with SCT Ha?
Also the pictures through LS50F Ha + SCT Ha ?

Thanks,

Valery.


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Re: PST etalon (or similar) in a telecentric beam

Post by mdwmark »

Hi Guys,
You missing why they don't use a telecentric beam on a air spaced etalon.
If you started out with a .5Ang air spaced etalon and put it in a F/30 telecentric the etalon would broaden out to about 1.2 Ang.
It will be uniform but much broader.
Like stated earlier, It,s the same bandwidth just the wavelength shifts from the center blue from all sides, and you get your sweet spot.
When designing the collimated lens. You should get one of those free lens programs to play with for your spacing. If you just put a -300mm lens in front of prime focus you will find that you need the thickness of the lens. And the back lens spacing is important too. And the direction the lens are facing makes a big difference. It can take you from 1/4 wave to over 1 wave just by the direction the lens are facing.
Unless you are going to be around F/70 with an air spaced etalon your are going to have to live with a sweet spot.
Remember the broader the filter the smaller the sweet spot.
Mark W.


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Re: PST etalon (or similar) in a telecentric beam

Post by fjabet »

marktownley wrote:What sort of usable field of view can you get out of the SCT system Frederic?
That depends on your etalon size.
With a 50mm etalon and without the SCT thread that limits to 44mm clear aperture, the system delivers the full sun. But you would need a focal reducer + a long FL eyepiece. It's possible, but I don't see the point. But you could use a full frame sensor.
With a Quantum (32mm diameter), I see 1/5 of the solar surface with a 35mm Eudiascopic or a XW30. I use this configuration with a CMOSIS CMV4000 (11,2mm square sensor) and with a Meade 6.3 reducer when the seeing is very bad.
With a 20mm PST + BF15, the field just fill up the 35mm Eudiscopique. But with the binovue the AFOV limitation isn't an issue.


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Re: PST etalon (or similar) in a telecentric beam

Post by Valery »

mdwmark wrote:Hi Guys,
You missing why they don't use a telecentric beam on a air spaced etalon.
If you started out with a .5Ang air spaced etalon and put it in a F/30 telecentric the etalon would broaden out to about 1.2 Ang.
It will be uniform but much broader.
Like stated earlier, It,s the same bandwidth just the wavelength shifts from the center blue from all sides, and you get your sweet spot.
When designing the collimated lens. You should get one of those free lens programs to play with for your spacing. If you just put a -300mm lens in front of prime focus you will find that you need the thickness of the lens. And the back lens spacing is important too. And the direction the lens are facing makes a big difference. It can take you from 1/4 wave to over 1 wave just by the direction the lens are facing.
Unless you are going to be around F/70 with an air spaced etalon your are going to have to live with a sweet spot.
Remember the broader the filter the smaller the sweet spot.
Mark W.
Hi Mark,

I believe that the narrower the filter, the smaller the sweet spot.

I also don't believe that any of these air spaced etalons mentioned (PST and LS50) work fine because all air spaced etalons
are MUCH more sensitive to converging of the beam that the solid spaced etalons. Where the solid spaced etalons will work fine
with about F/30, all air spaced etalons will fail.
Walter Koch already tried the telecentric baader (TZ4) with his LS50F Ha with fail.

This is the reason why Lunt Engineering use a collimation - refocusing system in their telescopes with internal etalons.


Valery.


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Re: PST etalon (or similar) in a telecentric beam

Post by fjabet »

Valery wrote:
If there any chances you show us the photos you take with this PST etalon in it's normal configuration (say with refractor F/10) and with SCT Ha?
Also the pictures through LS50F Ha + SCT Ha ?

Thanks,

Valery.
On this link, the first one is PST DS, the second a single PST. The seeing was very poor and there are some fringes.
http://www.astrosurf.com/ubb/Forum3/HTML/041024.html
I didn't take any image with the PST in its standard configuration.

The LS50F + HaT test has been done in Serbannes with Oliver's filter, I didn't have the time to take any image. But we had a very nice view in it with Oliver and Christian Viladrich. If Oliver passes by, he would comment.
I ordered a LS50FHa and I will test that has soon as I receive it and I have the adaptation rings done.
If the Lunt is good (i.e. if I'm lucky), there will be a Quantum 0.6 PE in the classified soon...


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Re: PST etalon (or similar) in a telecentric beam

Post by fjabet »

Valery wrote:
Hi Mark,

I believe that the narrower the filter, the smaller the sweet spot.

I also don't believe that any of these air spaced etalons mentioned (PST and LS50) work fine because all air spaced etalons
are MUCH more sensitive to converging of the beam that the solid spaced etalons. Where the solid spaced etalons will work fine
with about F/30, all air spaced etalons will fail.
Walter Koch already tried the telecentric baader (TZ4) with his LS50F Ha with fail.

This is the reason why Lunt Engineering use a collimation - refocusing system in their telescopes with internal etalons.


Valery.
In theory you're right, but if the telecentricity is very good it just works. The bandwidth may be a bit broadened, but I just can't tell the difference.
Jean Pierre also used his LS35 etalon with his 230mm in a telecentric configuration with success.

And the great advantage on the collimated solution is that there is no soft spot as there is just the marginal angle and no field angle.


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Re: PST etalon (or similar) in a telecentric beam

Post by fjabet »

Here is a better one with the PST single stack.
Image


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Re: PST etalon (or similar) in a telecentric beam

Post by marktownley »

Thanks for the info guys! :)


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Re: PST etalon (or similar) in a telecentric beam

Post by swisswalter »

fjabet wrote:Here is a better one with the PST single stack.
Image
hi Frédéric

what a teriffic shot


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Re: PST etalon (or similar) in a telecentric beam

Post by marktownley »

mdwmark wrote:It,s the same bandwidth just the wavelength shifts from the center blue from all sides, and you get your sweet spot.
Hi Mark, Frederic et al,

I don't know if anyone can answer this, but as the wavelength shifts from the centre to blue at the edges does it do it in a linear way, or does it do it non linearly? i.e. the further you get from the centre the more progressively blue it becomes - kind of like with the inverse square law and how gravity falls away with distance...


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Re: PST etalon (or similar) in a telecentric beam

Post by fjabet »

Intuivively, I would say a sine law ?


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Re: PST etalon (or similar) in a telecentric beam

Post by Valery »

fjabet wrote:
Valery wrote:

And the great advantage on the collimated solution is that there is no soft spot as there is just the marginal angle and no field angle.
Frederic,

All depends. Have you seen my photos here? They all were made with the telescope equipped with a specifically designed collimation system.
Also, look at photos taken with Lunt dedicated solar telescopes (with internal collimated system)?

Have you seen soft spot on them?


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Re: PST etalon (or similar) in a telecentric beam

Post by fjabet »

I agree, there is no soft spot if the etalon is large enough to keep the field angle below 0.5°. But with a FL long enough to aim at high resolution, the telecentric seems to me the best way to go : I prefer to have only some controlable marginal angle than field angle and a non homogeneous bandpass over the FOV. I'm using quite large sensors for imaging (CMOSIS CMV4000, and the IMX174 pretty soon), sometimes with a focal reducer, so I'm very concerned with the field consistancy.
BTW I've seen in a quite large number of Lunt with internal etalon, and I've not been thrilled by the result. I've found the quality very inconstant, including a pair of LS152 with the field not being on band completly.

I think that Lunt and Coronado have chosen the collimated path to preserve a short FL and the capability to see the full disk and not because it's better than the telecentric solution.


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Re: PST etalon (or similar) in a telecentric beam

Post by fjabet »

Just another advantage of the telecentric solution : you can use a mirror telescope. With the internal collimated etalon I'm not sure it's possible (unless having a huge baffle to place the etalon in). And over 200mm aperture a refractor is clumsy and more expensive.
Now for smaller intruments you may be right, the collimated option has advantages starting with the shorter FL.
I thought all this in a >200mm perspective. Actually my next project is a 350mm aperture Ha+CaK telescope (not a C14, that's a completly different design from the HaT and a SCT couldn't cope with UV bandwidth).


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Re: PST etalon (or similar) in a telecentric beam

Post by marktownley »

fjabet wrote:I think that Lunt and Coronado have chosen the collimated path to preserve a short FL and the capability to see the full disk and not because it's better than the telecentric solution.
I completely agree Frederic


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Re: PST etalon (or similar) in a telecentric beam

Post by marktownley »

fjabet wrote:I agree, there is no soft spot if the etalon is large enough to keep the field angle below 0.5°.
How do we do this with a PST mod and a collimating lens system, or is it just not possible with the small size of the PST etalon?


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Re: PST etalon (or similar) in a telecentric beam

Post by fjabet »

Hello Mark,

as a rule of the thumb, the chief ray field angle for a 0,25° field (full sun) is -0,25*F/f in degrees where F is the refractor FL, and f the negative lens FL.
For example for the PST : -0,25*400/-200 = 0,5° => we are within the etalon tolerance (that is less than 0,5° in the case of a collimated beam, the telecentric solution is 2x more tolerant regarding the angles as mentionned in a paper I've seen some times ago).
If you want this for a 100/1000 refractor, then you must increase the negative lens to -500mm. In that case, to keep the F/10 ratio, the negative element aperture must be (-)500/10 = 50mm. Thus you need a 50mm etalon as well. And the etalon should be quite deeply installed in the refractor.
In fact the real issue with this is to find the negative lens, they are scarcer than converging lenses in manufacturer portfolio.
But with a 100/1000 refractor and a 50mm non obstructed etalon, you have a home brewed Lunt 100 :)


Frédéric.


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Re: PST etalon (or similar) in a telecentric beam

Post by Valery »

fjabet wrote: If you want this for a 100/1000 refractor, then you must increase the negative lens to -500mm. In that case, to keep the F/10 ratio, the negative element aperture must be (-)500/10 = 50mm. Thus you need a 50mm etalon as well. And the etalon should be quite deeply installed in the refractor.
He don't need to go with 100mm F/10 refractor. He can go with 100mm F/5.


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Re: PST etalon (or similar) in a telecentric beam

Post by Valery »

fjabet wrote:
I think that Lunt and Coronado have chosen the collimated path to preserve a short FL and the capability to see the full disk and not because it's better than the telecentric solution.
It is indeed better than telecentric solution if an etalon is air spaced. Lunt did his job nicely with no mistakes. In the same time I know two cases when Lunt airspaced etalons were used in a telecentric configuration. Both failed due to lowering of the contrast (bandpass broadeing).

Valery.
Last edited by Valery on Sat Aug 16, 2014 1:08 pm, edited 2 times in total.


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Re: PST etalon (or similar) in a telecentric beam

Post by marktownley »

Valery wrote:He don't need to go with 100mm F/10 refractor. He can go with 100mm F/5.
Yes, that's another way of doing it...


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Re: PST etalon (or similar) in a telecentric beam

Post by fjabet »

I wonder if the field angles increasing as the FL shortens ?

Anyhow as I said the collimated beam preserves the FL and maybe the way to go for aperture <180mm. But for larger telescope, you don't really have a choice and you don't want to make full sun but rather high resolution.

As for Lunt performances, we are several observers who don't share you enthousiasm but maybe we have been unlucky :)

Do you have any specs and picture of your commercial system ?


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Re: PST etalon (or similar) in a telecentric beam

Post by Valery »

fjabet wrote:I

As for Lunt performances, we are several observers who don't share you enthousiasm but maybe we have been unlucky :)

Do you have any specs and picture of your commercial system ?
Yes, definitely, you, guys, were extremely unlucky because all of you own bad Lunt scopes(???). First - why not ask Lunt to replace the telescopes of fix the problems? They seems to have excellent customer service. Secondly, what are real problems with all your, guys, Lunt telescopes with collimated internal etalons?
What the telescopes you were unhappy with?

BTW. I wan't share any details about my commercial products. Hope this understandable.


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Re: PST etalon (or similar) in a telecentric beam

Post by fjabet »

Let us say that a lot of the Lunt I've seen on the field were below expectations in term of contrast and/or uniformity. I know very well a LS152 that just can't show more than 40% of the field on band.
Now it seems that there was (is?) an issue with the Lunt BF as replacing it with a Coronado would increase the contrast.

Anyway we will have to use Lunt now as Coronado is gone, at least for a while...

I was not asking for your design, but just the commercial product presentation...


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Re: PST etalon (or similar) in a telecentric beam

Post by Valery »

fjabet wrote:Let us say that a lot of the Lunt I've seen on the field were below expectations in term of contrast and/or uniformity. I know very well a LS152 that just can't show more than 40% of the field on band.
Now it seems that there was (is?) an issue with the Lunt BF as replacing it with a Coronado would increase the contrast.

Anyway we will have to use Lunt now as Coronado is gone, at least for a while...

I was not asking for your design, but just the commercial product presentation...

Andy Lunt himself has said that his LS152T is purposed for high resolution views and imaging.
Such a telescope is not for full disk viewing - there are a lot of alternatives in smaller sizes - 50mm, 60mm, 80mm and 100mm size - with front mounted and with internally mounted etalons. However even with LS152T our friend Pedro easily imaging the Sun in full disk size. Same with several other owners of LS152T.
If correctly adjusted, LS152 shows full sun disk in Ha, may be with some contrast loss near the edge of the sun disk. I saw enough photos where all is OK with sun disk in band. More so, I can tell you, that my solar kit has been designed for using in 100mm F/5, 120mm F/5 and 150mm F/5 telescopes.

More developments will follow soon.


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