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#26 BYoesle

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Posted 17 October 2020 - 11:09 PM

Can a front mounted etalon be added to a non-solar refractor as a single stack configuration? Yes. What's the difference between a stack and the blocking filter, e.g., B1200. Are both (a stack and a blocker) required for Sun Yes; can Sun be observed with either one? No. If not, what is the minimum requirement to observe sun, a blocker or a stack? ERF, etalon, blocking filter.

 

Sorry, this is all quite confusing for a start up; but why hesitate to ask. Most of all, why Solar has such confusing terms, as etalon, blocker, filter, etc. I don't need an assay on etalon, just a simple one line answers as to the difference between an etalon and a blocker and do they have to together or not? Yes - together.

 

While I am at it, why the term double stack? Does it really mean two etalons in the imaging train? Yes. Word 'stack' has connotation of one next to the other, but then they can be used quite apart from each other. Not quite.

So much for the simple one-word answers - and simple phrases... which doesn't explain much. For a more in-depth understanding, you will actually have to want to learn more. If so, you will find answers here. You will discover H alpha filters are really a system of multiple filters that accomplish different tasks in order to make the Sun safe to view and accomplish something no nighttime filter can.

 

As far as what double stacking accomplishes, it is there too. Here's what it actually achieves:

 

double stacking non-normalized.jpg

click for larger


Edited by BYoesle, 17 October 2020 - 11:12 PM.

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#27 Lost in Space

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Posted 17 October 2020 - 11:11 PM

Can a front mounted etalon be added to a non-solar refractor as a single stack configuration? What's the difference between a stack and the blocking filter, e.g., B1200. Are both (a stack and a blocker) required for Sun; can Sun be observed with either one? If not, what is the minimum requirement to observe sun, a blocker or a stack?

 

 

Sorry, this is all quite confusing for a start up; but why hesitate to ask. Most of all, why Solar has such confusing terms, as etalon, blocker, filter, etc. I don't need an assay on etalon, just a simple one line answers as to the difference between an etalon and a blocker and do they have to together or not?

 

 

While I am at it, why the term double stack? Does it really mean two etalons in the imaging train? Word 'stack' has connotation of one next to the other, but then they can be used quite apart from each other. Thanks in advance. Regards

 

mmalik, you can use a regular refractor for Hydrogen Alpha solar viewing ONLY if you have the proper filtering attached...

At a minimum, for Hydrogen Alpha solar viewing with a regular refractor you must have BOTH of these: 

 

1)  A single (stack) etalon mounted over (in front of) the objective lens AND

2)  A Blocking Filter (BF) assembly which has a two filter assembly permanently mounted in a special diagonal designed to go with your etalon, or a straight-through BF assembly (not in a diagonal) which makes it easier for photography.   Your eyepiece or camera is the last piece added after the BF assembly.

 

*** IMPORTANT *** You absolutely must use BOTH the etalon and the BF at the same time or you risk severe eye damage or blindness. ***

 

Dedicated solar scopes can vary as to where the etalon, or etalons if double-stacking (two etalons) are in use.  Essentially, two etalons can be installed within the OTA after the objective lens, or one can be externally mounted in front of the objective, and the second can be internal.  Double stacking etalons can also be stacked one directly over the other in front of the objective lens.  Lots of variation here, but regardless of etalon configuration on a dedicated solar scope, a BF is still required for the same reasons I mentioned before.

 

I have a Tele Vue 76 refractor which is not a dedicated solar scope.  I purchased a Coronado SM60 etalon and BF15, along with an adapter plate so the etalon can be directly screwed to the scope in front of the objective lens.  For me I felt it was a safer bet to attach it that way.  Etalons don't bounce if they fall of the scope, they break, or are rendered useless until they are repaired - assuming it is even possible at that point - PLUS eye damage could result if someone was viewing through the eyepiece at the time the etalon fell off.

 

I won't go into how etalons work as that has been covered before in many threads.  Plus I don't fully understand it myself, so why screw things up.  ;)


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#28 chemman

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Posted 18 October 2020 - 12:04 AM

Can a front mounted etalon be added to a non-solar refractor as a single stack configuration? What's the difference between a stack and the blocking filter, e.g., B1200. Are both (a stack and a blocker) required for Sun; can Sun be observed with either one? If not, what is the minimum requirement to observe sun, a blocker or a stack?

 

 

Sorry, this is all quite confusing for a start up; but why hesitate to ask. Most of all, why Solar has such confusing terms, as etalon, blocker, filter, etc. I don't need an assay on etalon, just a simple one line answers as to the difference between an etalon and a blocker and do they have to together or not?

 

 

While I am at it, why the term double stack? Does it really mean two etalons in the imaging train? Word 'stack' has connotation of one next to the other, but then they can be used quite apart from each other. Thanks in advance. Regards

The main problem with adding a etalon in front of the scope is the price for that large etalon.  I have a 100mm triplet FPL-53 and it images good night and day.   For Solar this bit is in the image train about 2/3rds focal length:    Front is a Energy Rejection FilterFirst and second etalon, then the blocking filter.  

 

So here is the 8 pound baby,  ERF-Etalon1-Etalon2-BF

 

I love 3 screws off, and on with the 2" night-terrestrial focuser.

 

Chuck 


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#29 D.T.

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Posted 18 October 2020 - 12:24 AM

A couple of questions:

 

1) My LS60THa/B1200FT must be tuned.  I found the pressure tuning mechanism to be a bit tricky.  Now if I added a front mounted Etalon to get double stacked, doesn't that need to be tuned also?  It would seem that could be very tricky to get them both set correctly to Ha.  Is the Double Stack significantly harder to use?

2) When I bought my 60mm telescope from Lunt, they offered a double stack option which the front mount Etalon was 50mm.  It would seem that this would stop down the entire telescope such that one might have just bought a 50mm telescope for the same results.  Don't I need a 60mm Front Etalon for my LS60THa?  Or is there some logic here that I don't understand?



#30 mmalik

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Posted 18 October 2020 - 01:33 AM

Thanks for all the great answer, quite enlightening. How do objective mounted Solar films work; I mean do they also require a blocker at the back end? I understand films are white light; how would a blocker behave with a film? Are all Solar films white light devices? I presume all etalons are h-alpha? Are all Solar wedges white light only? Do Solar wedges require a film? I presume Solar wedges and Solar films are NOT compatible with Etalon+Bocker designs? Would it be correct to say that we basically have three Solar designs 1) Etalon+Blocker, 2) Wedges (w or wo film) and 3) Films? Which designs are visual and/or imaging friendly? Sorry, lot of questions. Regards


Edited by mmalik, 18 October 2020 - 01:36 AM.


#31 rigel123

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Posted 18 October 2020 - 05:20 AM



I'm impressed with the contrast in the spicules. I haven't seen that yet on my telescope and I didn't think that detail was possible with a single stack.

Actually the “seeing”, which is how steady the atmosphere is when I took this shot, was not great at the time so those spicules can be even better defined such as in the animation that I did posted here.  In the animation you can see the individual spicules shooting up all around the large prom.  If you haven’t been able to see them in your 60mm scope then your seeing just hasn’t been steady enough.  The animation was with the same scope with a 2X Barlow attached and seeing was excellent.  It also takes practice when viewing, similar to planetary viewing of watching for those brief periods when the atmosphere settles down and the image basically snaps into sharp focus for you.  It’s a bit difficult to explain, but the more you view, the more your eye will see with practice.  

 

 

get.jpg?insecure


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#32 rigel123

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Posted 18 October 2020 - 05:35 AM

A couple of questions:

 

1) My LS60THa/B1200FT must be tuned.  I found the pressure tuning mechanism to be a bit tricky.  Now if I added a front mounted Etalon to get double stacked, doesn't that need to be tuned also?  It would seem that could be very tricky to get them both set correctly to Ha.  Is the Double Stack significantly harder to use?

2) When I bought my 60mm telescope from Lunt, they offered a double stack option which the front mount Etalon was 50mm.  It would seem that this would stop down the entire telescope such that one might have just bought a 50mm telescope for the same results.  Don't I need a 60mm Front Etalon for my LS60THa?  Or is there some logic here that I don't understand?

Yes, you must tune both etalons but it is not difficult.  You first set up without the second etalon attached and tune that to the best contrast you can get.  Then you attach the second, front mounted etalon and you will then typically see the sun as well as a “ghost” image of the sun that may be overlapping the real image of the sun or may be nearby.  Then you use the tilt tuner on the front etalon to simply move that ghost image off the real image, or out of the field of view entirely if it bothers you to see it.  Sometimes the best contrast is achieved with that ghost image moved just enough so it doesn’t overlap at all but still may be visible in the FOV with a particular eyepiece.  

 

And yes, to your second question, the 50mm would stop down your 60mm scope, which is why I went with the 60mm on my Lunt, but it is a lot more expensive, which is why they offer the 50mm as an option to achieve a double stack.


Edited by rigel123, 18 October 2020 - 05:45 AM.


#33 hopskipson

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Posted 18 October 2020 - 08:11 AM

 

 

And yes, to your second question, the 50mm would stop down your 60mm scope, which is why I went with the 60mm on my Lunt, but it is a lot more expensive, which is why they offer the 50mm as an option to achieve a double stack.

As a less expensive option that no one seems to mention is using a Coronado DS etalon on your Lunt 60.  You may be able to find them as old stock at some retailers but you have to search them out.  The used market is another option.  You will need to have an adapter made to mate the Coronado to the Lunt which can be done at Precise Parts.  This option could save you hundreds of $$.


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#34 Arcamigo

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Posted 18 October 2020 - 09:46 AM

It also takes practice when viewing, similar to planetary viewing of watching for those brief periods when the atmosphere settles down and the image basically snaps into sharp focus for you.  It’s a bit difficult to explain, but the more you view, the more your eye will see with practice.

Thank you. You explained it well. I know exactly what you mean. I've been doing this a lot recently with Mars. Yet another reason to be out there viewing regularly and why solar viewing won't get boring for me.


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#35 chemman

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Posted 18 October 2020 - 12:08 PM

Thanks for all the great answer, quite enlightening. How do objective mounted Solar films work; I mean do they also require a blocker at the back end? I understand films are white light; how would a blocker behave with a film? Are all Solar films white light devices? I presume all etalons are h-alpha? Are all Solar wedges white light only? Do Solar wedges require a film? I presume Solar wedges and Solar films are NOT compatible with Etalon+Bocker designs? Would it be correct to say that we basically have three Solar designs 1) Etalon+Blocker, 2) Wedges (w or wo film) and 3) Films? Which designs are visual and/or imaging friendly? Sorry, lot of questions. Regards

This podcast could answer a lot of your questions.  I found at 20:00 to be particularly interesting.  

 

Space Junk Podcast



#36 BYoesle

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Posted 18 October 2020 - 02:02 PM

Etalons are very narrow band filters used with multiple ancillary filters for viewing the chromosphere. The most common etalons for the Sun are used for the emissions of H alpha at 656 nm and CaK at 394 nm. They can be mounted ahead of the objective, internal to the OTA in a collimator/refocusing lens system, or near they eyepiece at f30 +. The CaK line is  broader and can be used with a more standard design filter at lower f ratios, so they are not always etalon designs.

 

A film filter (and similar glass filters) is a continuum filter placed before the objective for viewing the photosphere and generally does not require additional filtering. It reflects 99.9999% of the incident sunlight, and the remainder 1/100,000 of the incident light passes through. Sometimes an additional ND filter and/or a Baader Continuum filter can be added to adjust the brightness and improve contrast - especially with achromatic refractors.

 

The Herschel wedge is also a continuum filter used with few exceptions with refractors only. The unsilvered face of the prism reflects ~ 5% of the incident sunlight, and it must be used with a minimum of a ND 3 filter following the prism. Usually additional filters per the above for the film filter are needed as well. A single polarizing filter can also be used to have a variable level of brightness adjustment due to the polarized reflection off the prism face.


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#37 chemman

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Posted 19 October 2020 - 11:53 AM

Etalons are very narrow band filters used with multiple ancillary filters for viewing the chromosphere. The most common etalons for the Sun are used for the emissions of H alpha at 656 nm and CaK at 394 nm. They can be mounted ahead of the objective, internal to the OTA in a collimator/refocusing lens system, or near they eyepiece at f30 +. The CaK line is  broader and can be used with a more standard design filter at lower f ratios, so they are not always etalon designs.

 

A film filter (and similar glass filters) is a continuum filter placed before the objective for viewing the photosphere and generally does not require additional filtering. It reflects 99.9999% of the incident sunlight, and the remainder 1/100,000 of the incident light passes through. Sometimes an additional ND filter and/or a Baader Continuum filter can be added to adjust the brightness and improve contrast - especially with achromatic refractors.

 

The Herschel wedge is also a continuum filter used with few exceptions with refractors only. The unsilvered face of the prism reflects ~ 5% of the incident sunlight, and it must be used with a minimum of a ND 3 filter following the prism. Usually additional filters per the above for the film filter are needed as well. A single polarizing filter can also be used to have a variable level of brightness adjustment due to the polarized reflection off the prism face.

Bob, I was surprised to learn from the discussion by Brian Stephens in the recent podcast, that the pressure tuned etalon changes pressure within the entire etalon cavity. Brian went into a bit of Solar imaging explanation in a Youtube for the NASA EDGE megacast for the 2017 Solar eclipse.  There Brian was operating a Heliostat that directed a light beam to 3 telescopes imaging in Hα-CaK-White light now using 8K Red DSMCII camera  backs, I win the lottery I will have one of those Red.  But I had somehow assumed the space between the two mirrored surfaces was where the pressure was  changing during tuning, still true but the  entire cavity is changing pressure.  I should receive from Lunt this week a couple connector kits to adapt external pressure control which I will make remote.  It seems I have a  bit of an issue at times with  areas in the etalon that tune better than other areas which  results in a lot of knob twisting. In addition I have wanted since the beginning  of  this solar endeavor to incorporate a binocular with two cameras, one with a wide field of view and one with a magnified FOV.  An X-Y-Z control on the magnified camera to select points of interest would be nice.  Maybe in 5 years when I retire I will have  more  time to work on that  project.    lol

 

If the OP or mmalik would like a  bit of elaboration on your nice but brief overview Bob, Here is a website I ran across  doing just that:  Luxorion


Edited by chemman, 19 October 2020 - 12:34 PM.

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#38 Great Attractor

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Posted 20 October 2020 - 03:13 AM

But, for solar, there is just one sun.  So, what is it that makes a hobby of this?  Can you really go out to observe, or photograph, the sun every day and always find something new, different, and interesting?


Maybe not every day, but each prominence, sunspot group (...once the activity picks up in the coming years), filament — is different, and when you do time lapses, each may do something interesting at any moment (prominence/filament liftoff, solar flare or surge). As for equipment, one may start small, my most spectacular surge was taken with Lunt 35 mm Hα telescope.


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#39 briansalomon1

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Posted 20 October 2020 - 08:59 PM

I'm considering getting involved with Solar Astronomy.  Before I spend more money on astronomy, I would like to determine if solar is right for me.  I would like to get a better understanding of what holds people's interest?  Night astronomy provides countless galaxy's, nebula's, the milky way, narrow band imaging, double stars, planets, occasional comets.  But, for solar, there is just one sun.  So, what is it that makes a hobby of this?  Can you really go out to observe, or photograph, the sun every day and always find something new, different, and interesting?

Yes. The Sun (in H-alpha) is quite a lot more interesting than other objects. The features change constantly and I get what I'd consider good seeing almost any clear morning.

 

I use an NP101 for night as well as H-alpha. It takes just a few minutes to attach the etalon/blocking filter and I think the very best thing about H-alpha is that there is almost never a time when I can't get a view of something really interesting day or night.



#40 briansalomon1

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Posted 21 October 2020 - 11:58 AM

Can a front mounted etalon be added to a non-solar refractor as a single stack configuration? What's the difference between a stack and the blocking filter, e.g., B1200. Are both (a stack and a blocker) required for Sun; can Sun be observed with either one? If not, what is the minimum requirement to observe sun, a blocker or a stack?

 

 

Sorry, this is all quite confusing for a start up; but why hesitate to ask. Most of all, why Solar has such confusing terms, as etalon, blocker, filter, etc. I don't need an assay on etalon, just a simple one line answers as to the difference between an etalon and a blocker and do they have to together or not?

 

 

While I am at it, why the term double stack? Does it really mean two etalons in the imaging train? Word 'stack' has connotation of one next to the other, but then they can be used quite apart from each other. Thanks in advance. Regards

H-alpha systems use a single or double etalon (single stack/double stack) together with a blocking filter.

 

The "stack" (etalon) is like a coarse filter but it still needs the blocking (fine) filter in order to work. Etalons can be placed in front of the objective, in the middle of the optical train or even at the eyepiece end as long as they are in front of the blocking filter.

 

The difference between an etalon and blocking filter is the etalon is an interference (coarse) filter.  They are safe to use only when used together.

 

I've been using a single Lunt 60mm etalon with the Lunt BF1800 on my TeleVue NP101 fo some time now. My experience is similar to what Rigel123 reports.


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