Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by MalVeauX »

MAURITS wrote: Sun Sep 29, 2019 1:05 pm What a great review Marty.
In the first place you need for sure the knowledge to make such a pst etalon, looks on the first sight difficult.
The results are awesome.
Thankfully fine folk here on S.C. lend their wisdom, as this stuff isn't really intuitive unless you know what each component is and is doing and that's not really published by the manufacturer.

Next I want to mod the new 10mm blocking filter to also be straight through to eliminate that mirror being in the imaging train.

Very best,


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by george9 »

For the 10mm blocking filter, will you skip whatever the mirror is accomplishing? I am guessing it is redundant with your red CCD filter. E.g., in current Lunts, it passes IR out the system instead of reflecting it up into the eyepiece. Not sure about pre-Meade Coronado, but it is the same team. Not sure exactly what my early pre-Meade blocking filter (Prom15T) mirror does.

George


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 »

I tested the Coronado BF15 mirror with the spectrograph some time ago and found as you say it's a IR reject mirror.


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by MalVeauX »

Merlin66 wrote: Wed Oct 02, 2019 1:22 am I tested the Coronado BF15 mirror with the spectrograph some time ago and found as you say it's a IR reject mirror.
george9 wrote: Wed Oct 02, 2019 1:07 am
For the 10mm blocking filter, will you skip whatever the mirror is accomplishing? I am guessing it is redundant with your red CCD filter. E.g., in current Lunts, it passes IR out the system instead of reflecting it up into the eyepiece. Not sure about pre-Meade Coronado, but it is the same team. Not sure exactly what my early pre-Meade blocking filter (Prom15T) mirror does.

George
Good points, so if I already have a filter that is rejecting long IR wavelength, it accomplishes the same thing then?

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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by george9 »

For imaging I expect it is fine. The red-CCD should cover what the camera should be sensitive to.

For visual, I am just not that well versed in near-, intermediate, and far-IR. The Lunts are very redundant for safety I know (so that, for example, forgetting the blocking filter doesn't blind you). What I understand is:

KG3 covers intermediate and far IR
UV/IR coated KG3 covers all IR
Baader red-CCD covers near and intermediate IR to 1200 but not longer
Baader 35nm H-alpha covers near and intermediate IR to 1200 but not longer

(By the way, I noticed Baader has a disclaimer never to use their 35nm as an internal ERF, not that they say it will fail.)

George


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by MalVeauX »

george9 wrote: Thu Oct 03, 2019 7:24 pm
(By the way, I noticed Baader has a disclaimer never to use their 35nm as an internal ERF, not that they say it will fail.)
I think, with 99.9% certainty, this is to prevent someone from pointing this filter, at focus, at the sun as a stand alone "Ha" filter thinking it's meant for that and not just a night-time filter. Many use this filter in the light beam, but not at focus, as an ERF and it's the ideal one actually.

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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 »

Yes,
I saw that .....
As we keep saying solar mods are non standard and should be treated with extreme caution.
We are stretching the envelope.....always opt for the safest option.
I personally think all ERF and sub ERF for H alpha should be Baader D-ERF filters.


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Rusted »

Marty,

Thanks for your interesting post on the mechanics of PST modification.
If only it were that easy! Then we would all be able to match your exquisite results with the same "kit of parts." ;)

I see you use an aperture stop on your 6" f/8 to provide a true 120mm @ f/10.
My [rather limited] understanding is that a faster [f/8] telescope is self-limiting to f/10 by means of geometry alone.
This being due to the f/10 correction optics of the PST etalon lens group.
They won't allow an angle of incidence larger than an f/10 light cone to pass.

Do you consider is there is any particular advantage to stopping down the objective?
Reduced internal heating perhaps? Stray light reduction?

An internal D-ERF can/should only be placed where the F/8 light cone falls within its clear aperture.
Too near the objective and the light cone will heat the D-ERF supporting baffle and cause vignetting due to annular overlap.

Perhaps the 120mm aperture stop will allow a more forward placing of the D-ERF?
Less intensely focused heat, nearer the objective, due to the larger illuminated area?

Thanks
Chris


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by MalVeauX »

Rusted wrote: Wed Oct 09, 2019 2:05 pm Do you consider is there is any particular advantage to stopping down the objective?
Reduced internal heating perhaps? Stray light reduction?

An internal D-ERF can/should only be placed where the F/8 light cone falls within its clear aperture.
Too near the objective and the light cone will heat the D-ERF supporting baffle and cause vignetting due to annular overlap.

Perhaps the 120mm aperture stop will allow a more forward placing of the D-ERF?
Less intensely focused heat, nearer the objective, due to the larger illuminated area?

Thanks
Chris
Hey Chris,

The thermal load alone is a consideration. If I left it 150mm F8 and just reduced to F10 at the collimating lens, the thermal load is that of a 150mm still in the tube at least (not the same at focus of course). I think it also matters for focus, but only by a little bit, and the collimating lens is rather specific, my understanding is that the angle of the rays of light are different at F8 than at F10 in the same -200mm position, but I'm not well versed enough to really speak to it beyond that, or I think everyone would avoid cutting their OTA tubes and just let the collimating lens do the F10 thing, but I don't think its that simple.

Very best,


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by marktownley »

Rusted wrote: Wed Oct 09, 2019 2:05 pm
Do you consider is there is any particular advantage to stopping down the objective?
Stopping down an objective also reduces spherical aberration. There will be less Spherical Aberration with a 150/8 stopped down to 120, than with a 120/10 operating full aperture.


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Rusted »

Thank you both for your responses. I shall try stopping down my 150/8 H-a 'scope.

Though an umbrella might be a better mod given our present run of wet weather. :roll:


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by bart1805 »

MalVeauX wrote: Mon Sep 30, 2019 10:47 am Next I want to mod the new 10mm blocking filter to also be straight through to eliminate that mirror being in the imaging train.
With the Coronado BF's, the part with the valuable BF is not threaded, it is just glued to the bottom of the eyepiece holder. First remove the BF itself. Then use heat to loosen the glue and you will be able to pop the piece out of the holder.
With Lunt BF's it works basically the same. But the Lunt piece has a T2 thread you can use.


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by MalVeauX »

bart1805 wrote: Sun Oct 13, 2019 8:15 pm
MalVeauX wrote: Mon Sep 30, 2019 10:47 am Next I want to mod the new 10mm blocking filter to also be straight through to eliminate that mirror being in the imaging train.
With the Coronado BF's, the part with the valuable BF is not threaded, it is just glued to the bottom of the eyepiece holder. First remove the BF itself. Then use heat to loosen the glue and you will be able to pop the piece out of the holder.
With Lunt BF's it works basically the same. But the Lunt piece has a T2 thread you can use.
Thanks!

Prior to this I had attempted to gently unthread it, but it didn't budge so I didn't force it until I found more information. I will have to try this soon.

Very best,


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by daslolo »

Would a 2" 2x barlow at the focuser of a f/5 refractor effectively turn it in a f/10
Then slide in the PST mod

Like this one https://www.amazon.com/dp/B07BRLT4LB/re ... tEb17Y1QZQ


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 »

Daslolo,
Probably not. The standard PST mod needs the etalon to be at -200mm inside the focus. Don't think you'll achieve that spacing with a normal Barlow.
You could replace the front lens of the PST assembly with a shorter negative focal length lens....


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by daslolo »

Merlin66 wrote: Thu Feb 20, 2020 12:40 pm Daslolo,
Probably not. The standard PST mod needs the etalon to be at -200mm inside the focus. Don't think you'll achieve that spacing with a normal Barlow.
You could replace the front lens of the PST assembly with a shorter negative focal length lens....
So a negative focal length lens would also turn the convergent rays parallel to go inside the etalon like a plano-concave lense?
And where do I find such thing.
Also where do we find adapters between various M? M32 to M42 female female is my current quest :)


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 »

AOK Swiss supply a 2" to M50 male nosepiece which fits the PST etalon assembly and a rear adaptor M50 female to 2"
http://www.aokswiss.ch/index_sonne.html
Edmund Optics probably have a suitable negative lens...you're looking for a 25mm diameter, negative focal length = 20 x focal ratio i.e. for an f5 scope use a -100mm fl at -100mm inside focus.
https://www.edmundoptics.com.au/p/250mm ... lens/5538/


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by daslolo »

Merlin66 wrote: Sat Feb 22, 2020 4:17 am AOK Swiss supply a 2" to M50 male nosepiece which fits the PST etalon assembly and a rear adaptor M50 female to 2"
http://www.aokswiss.ch/index_sonne.html
Edmund Optics probably have a suitable negative lens...you're looking for a 25mm diameter, negative focal length = 20 x focal ratio i.e. for an f5 scope use a -100mm fl at -100mm inside focus.
https://www.edmundoptics.com.au/p/250mm ... lens/5538/
Thanks Ken, where is the adapter that houses the lenses on a 2" tube? (M50 i guess)

You have a spectroscope, what's the reading on the costing of the pentaprism in the PST?

And this double layer filter cube lodged before the eyepiece?
Double layer filter
Double layer filter
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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 »

Daslolo,
The PST etalon assembly with the M50 thread front and back is used with the AOK swiss adaptors. The 2" nosepiece mounts to the telescope and the 2" rear female is used to add spacers and final blocking filter.
The pentaprism seems to be AR coated.
The small red filter you show is the final narrowband sort filter. There should be a highly reflective filter element (ITF) at the inner end of the eyepiece holder - this acts as an erf. The combo of the ITF and final sort filter makes up the "blocking filter" assembly.


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 »



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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by daslolo »

Thanks Ken.

I'm only modding the black box out, for now.

The pentaprism offers added protection, so be mindful of that when modding. I know it because I could feel something in my eyeballs in the mod, then nothing when I put back the stock PST. Through binos so I'm halving per eye exposure which means the penta must reduce exposure by a LOT.
In this context Diane's blog is important.
This Diane blog got me reading some science yesterday night! Our tolerance to IR isn't bad, decay seems slow and can be felt. Diane's numbers are missing the /cm2 so they're not useful out of the context of her blog, they only provide a ratio of blocking with and without the BK filter. This filter I'm not seeing in any of the mods, why is that? Have you guys measured the actual output after mod?

What's a narrowband "sort" filter? Couldn't find anything on sorting light.
Why is it made of two layers: one golden reflective and one red block?
Is the gold the ITF (metal deposit)? ref: https://luntsolarsystems.com/equipment-care/
Is the ITF a blocking filter, is ITF = BF?
It's tiny, about 4mm across, does it mean the PST is rocking a B400, is that what B stand for in the lunt and coronado diagonal (Blocking)?
And why is the ITF in the diagonal and not in front of the etalon to protect it from heat and UV, from decay.
What is the other filter that's about 17mm in diameter which is in the tube that's holding this eyepiece holder? Is it the ERF like those expensive Baader everyone talks about?

Pedro's youtubes are only slideshows, I didn't find any value in it. Value is in understanding why things are where, or for those who can't be bothered with that, where to get the parts.


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 »

Daslolo,
""What's a narrowband "sort" filter? Couldn't find anything on sorting light.""
The etalon produces a "comb" of light across the whole spectrum....each "tooth/ peak" section about 0.7A wide and separated from it's neighbour by 10A. One of these "tooth/ peaks" is very close to H alpha, and to suppress all the others while just letting the H alpha go through is the job of the final sort filter. It has a bandwidth less than the separation.

"" What is the other filter that's about 17mm in diameter""
This is the ITF filter ( induced transmission filter) which was introduced by Coronado when they changed design away from the original ERF coated objective. It acts as an ERF, protecting the final sort filter.

On PST mods, to reduce the incoming energy before the etalon, an effective ERF should be fitted to ensure adequate safety.


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by daslolo »

Thanks again Ken, I am starting to understand how it all works now.

It seems that adding another sort filter could narrow the total bandpass of the scope even more if, by gambling on manufacturing tolerance, its band is slightly offset from the other sort filter.
Is it the red part of the cube or the golden? why is the cube made of two layers?
Is it also called a blocking filter or BF or B400?

I'll get an ERF. Which ones have you spectrum analyzed which provides acceptable protection and does't cost 300$ for a 2"?

I'm doing the rock bottom pricing here, while being fully aware that I have only 2 eyeballs, because, from the parts I've gathered, a Mod black box is not sensible when compared to the price of a lunt50/B400 (only for the fun of making it and learning), a full mod where the PST turns into an eyepiece is where it starts to make sense.
But in that last scenario, as Marty said in another thread, a Quark is cheaper and narrower (more contrasty?)


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 »

The blocking filter designations (BF 10/ BF15/ B600 etc refer to the whole blocking filter assembly i.e. including the ITF or pre-filter (in the Lunt Schott BG38)
The number is generally the clear aperture of the final sort filter - BF10 = 10mm. B600 = 6mm etc.
To achieve the required sort filter bandwidth (around 8A) requires a sophisticated filter design...
Narrowing the bandpass is usually done by doubling up on the etalon, two 0.7A etalons will get the bandwidth down to around 0.4A -0.5A.
I'm not a fervent supporter of using sub-diameter ERF's.
The Baader H alpha 35nm CCD filter has the same coating as the Baader D-ERF.


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by daslolo »

Merlin66 wrote: Sun Feb 23, 2020 11:14 pm The blocking filter designations (BF 10/ BF15/ B600 etc refer to the whole blocking filter assembly i.e. including the ITF or pre-filter (in the Lunt Schott BG38)
The number is generally the clear aperture of the final sort filter - BF10 = 10mm. B600 = 6mm etc.
To achieve the required sort filter bandwidth (around 8A) requires a sophisticated filter design...
Narrowing the bandpass is usually done by doubling up on the etalon, two 0.7A etalons will get the bandwidth down to around 0.4A -0.5A.
I'm not a fervent supporter of using sub-diameter ERF's.
The Baader H alpha 35nm CCD filter has the same coating as the Baader D-ERF.
So one more zero in the BF nomenclature = one less zero of diameter :? BF30 is 30mm?

I see Baader is the reference, ever tested cheaper filters?
I think that's the one. So I'd put that or the 1.25" version in front of the 20mm colimator lens in a full mod setup.
baader.png
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What about that one?
https://www.firstlightoptics.com/uv-ir- ... ilter.html

Re: combing the spectrum, now it matches what I've seen, I took out the blocking filter assembly to find the focal point and saw a blue green sun on the piece of cardboard. Those green and blue spikes are the harmonics uh.


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 »

BF30 = 30mm
My preference would be the larger Baader, blocks UV, most of the visible and the NIR.


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by AndiesHandyHandies »

Hi,

Large front mounted DERFs let 40%-60% of the spectrum through from a review in Cloudy Nights I saw. Cannot find again and lost a file with a link in. The Baader DERF is the same technology as the 1.25" and 2" 35nm Baader filters. From Astrographs experience a 1.25" will work up to 4" and a 2" up to 6" diameter as an ERF, I use ERF to denote an internal DERF.

Using a laser pointed IR thermometer the optics behind a 1.25" on a Vixen VMC 110mm F10 are not discernable temperature over ambient. The back of the secondary, taken the cover off, is not hot.

The filters need to be at a position where they are fully illuminated and care taken where the reflected focus is.

In the VMC I put the 1.25" Baader after the moved forward PST -200mm collimator lens so the light is reflected out as it came in so no hot spot at all. I put extra aluminium baffles on the secondary and on top of the baffle tube. To mask the un-blackened corrector lenses in the secondary and limit the cone going down the baffle tube to minimise reflections off the inside.

My image is limited by external seeing in practice it appears to me.

Andrew.


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Rusted »

I have built a new 6" H-alpha telescope after permanently damaging my ZWO ASI120MC.

Despite the internal 90mm D-ERF I was able to burn my hand in the focused beam at the empty focuser. The heat must have damaged my camera even after passing through the etalon, ITF and BF. During video capture my 120MC shows a persistent, translucent mask, identical to solar surface features at the same scale I see on the monitor. I count myself lucky I did not do much visual observing once I caught the imaging bug!

The new OTA has an iStar 150/10 objective. A full aperture 160mm Baader D-ERF is fixed up front. Following helpful advice, given here, I am now protecting my PST etalon [and my ASI174 camera!] with 2" Beloptik KG3 and Baader CCD filters in front of the etalon.

If we ever get any sunshine I shall try to measure the temperature at the focal plane. First with only the D-ERF and objective fitted to the OTA.
Then again, with the two, blocking filters fitted into the empty focuser.


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H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by daslolo »

Rusted wrote: Mon Feb 24, 2020 9:56 am Despite the internal 90mm D-ERF I was able to burn my hand in the focused beam at the empty focuser. The heat must have damaged my camera even after passing through the etalon, ITF and BF. During video capture my 120MC shows a persistent, translucent mask, identical to solar surface features at the same scale I see on the monitor. I count myself lucky I did not do much visual observing once I caught the imaging bug!

protecting my PST etalon [and my ASI174 camera!] with 2" Beloptik KG3 and Baader CCD filters in front of the etalon.

If we ever get any sunshine I shall try to measure the temperature at the focal plane. First with only the D-ERF and objective fitted to the OTA.
Then again, with the two, blocking filters fitted into the empty focuser.
You're lucky! I would have burnt my eyeballs because I'm observation only. Do you know how that happened?

Your test will be very useful, and you can get a cheap uv measuring thing on amazon.
If someone can hold a camera while you test that, this'll add to this excellent video: https://www.youtube.com/watch?v=pJ1uqKaisFE


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 »

The subject of "burning lenses" was raised previously....
Based on the known data I prepared a spreadsheet shows the various effects of a ERF/ etalon/ITF/ blocking filter on the energy transmission.

[The extension zip has been deactivated and can no longer be displayed.]

I regularly use my ASI 174 and ASI 1600 on both my PST mod; full D-ERF, PST etalon, BF15 (102/1100) and the SM60/ED 80/ BF15 instruments and have not seen any adverse effect on the cameras......


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 »

daslolo,
I see you mention 60% transmission for the Baader D-ERF - where did this come from?
From my measurements based on the Baader data I get around 26% .......


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by daslolo »

Merlin66 wrote: Mon Feb 24, 2020 9:51 pm Based on the known data I prepared a spreadsheet shows the various effects of a ERF/ etalon/ITF/ blocking filter on the energy transmission.
Solar ignition.zip
Love that spreadsheet, I put it on google sheet for my private use and I'm thinking that the data on that stuff is scatterred far and wide, I could collect it and put it in a google doc for everyone to use and comment on, what do you say?
Merlin66 wrote: Mon Feb 24, 2020 11:31 pm I see you mention 60% transmission for the Baader D-ERF - where did this come from?
From my measurements based on the Baader data I get around 26% .......
Found it in one of the many posts I read here. Can you explain your 26% what it means and how you measured?


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 »

The D-ERF transmission curve shows the detail....
The UV (30% of the total solar energy) is suppressed, between 400 and 700nm (another 30% of the total solar energy) it only passes 35nm in Ha, this reduces the energy by >90% ( by >27% of the total, and the low transmission in the NIR brings it down to the 27% I quote.
I’m not at my computer, but can give more detailed calculation.....


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by daslolo »

Merlin66 wrote: Mon Feb 24, 2020 9:51 pm Based on the known data I prepared a spreadsheet shows the various effects of a ERF/ etalon/ITF/ blocking filter on the energy transmission.
Solar ignition.zip
I read through this, put it here for easier viewing than having to unzip a file. https://bit.ly/2vYUIP8
What is it about? No filter vs filter viewing through the same f/ scope?


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Merlin66 »

No, it shows the transmission of the incoming solar energy through scopes...
With an Herschel wedge, with various filters and the PST mod.
You can enter your own data and show the difference between any scope, f ratio and focal length.
The final solar energy intensity is related to aperture, focal ratio and attenuation due to filters.
The example was based on the intensity required to ignite paper....


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Rusted »

The camera problems I have experienced may well be due to the extensive duration of my imaging sessions.
Back in the summer I would often be out in the observatory by 9am.
Then track the sun all day long until it finally disappeared behind the trees at 4pm or even later.
Always using my 6" f/8 internal 90mm D-ERF with no more than PST standard etalon/filtration.

This is pretty extreme by any normal standards of amateur solar imaging and observing.
My assumption that the camera was heat damaged is wide open to conjecture.
The persistent, translucent mask looks just like the solar surface features I see on every imaging session.
I am just being very cautious now. To avoid a repeat with a far more expensive camera.

Here is a live video I captured at the time.
Where I deliberately moved the telescope, with the drives, to show the sun is behind the mask.

https://youtu.be/hHIlU7H2RA0


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by AndiesHandyHandies »

Hi

You can put in a 2" Baader 35nm as an internal ERF behind the moved PST Collimator lens, you will not be able to thread it on the front.

The advantage is the reflected energy from the Baader goes back out as an expanding cone the way it came in so no dangerous reflected focus.

It worked for me and only a 1.25" Baader 35nm up to 180mm telescope. I measure 57C on the Collimator/Baader combination. A bit less on the black side of the holder so correct reading.

My Quark is heated to 49C.

Andrew.


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Rusted »

Hi Andrew,

I am using a 2" Baader 35nm H-a in front of a Beloptik KG3 about 100mm in front of the standard PST etalon group.
Extra insurance for the etalon, filter optics and camera.
A full aperture, 160mm Baader D-ERF sits in front of the iStar 150mm F/10 H-a objective.


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Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by AndiesHandyHandies »

Hi

Plenty of protection there then!

Sometimes it tricky to get filters in a unit you slide up into the focusser.

I am trying to use my New Quark in a even bigger scope (dont tell on me) as it image is dim compared to the PST.

I have added a red dichoric filter after the 'standard' UV/IR which it came with for extra etalon protection. Not as dark red as the Baader.

Unfortunately Daystar, as many others (My TMB diagonal nose has no 48mm thread a real nuisance when my identical manufactured 40mm eyepiece does) did not think to thread the 2" nose piece so I cannot add extenders to put a 2" Baader up before the whole show and in a place where the heat will exit the telescope out of the light path.

I am getting to the thermal limit for a 1.25" blocker I think and thats in haze.

My idea to have the ERF after the PST Collimator does reduce reflection safety issues, eyes and hot spots inside the scope.
You could use a larger diameter collimator of same focal length further up the OTA as well to spread out the heat load.

Cheers. Andrew.


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Re: Easy PST Module with ERF (non-destructive, no cutting of OTA, & no-black-box rebuild)

Post by Rusted »

There is a 2" filter thread inside my 2" Baader Click-lock fitting where my protective filters sit.
I have the Click-lock fitted into my DIY turned tailpiece/back plate.
The AOC Swiss etalon nosepiece fits into the Click-lock fitting.
BTW Watch out for the tiny, grub screws working loose on the Baader clamp.
My whole filter stack was rocking up and down until I discovered the cause.
Easily fixed with a tiny hex key.

P1410517 rsz 600 txt.jpg
P1410517 rsz 600 txt.jpg (82.82 KiB) Viewed 8257 times


http://fullerscopes.blogspot.dk/

H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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