What can be done with a PST double stack?

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What can be done with a PST double stack?

Post by daslolo »

Any mod with the second etalon ?


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Re: What can be done with a PST double stack?

Post by MalVeauX »

Heya,

You can thread it onto the front of any scope for use, but it's not optimal unless its the primary SM40 II meant for that.

You cannot use it for anything in a rear-mounted configuration, it has a central obstruction; no etalons can be used with central obstructions or multi-obstructions (big etalons have several) in a rear mounted configuration, it would be like putting pennies in front of your sensor.

The rear mounted mods are done with clear aperture etalons (PST, Lunt 50, Daystar, etc).

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Re: What can be done with a PST double stack?

Post by daslolo »

In front of any scope... with a blocking filter in the diagonal?


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Re: What can be done with a PST double stack?

Post by MalVeauX »

daslolo wrote: Wed Mar 11, 2020 7:18 pm In front of any scope... with a blocking filter in the diagonal?
Heya,

With an appropriate holder/adapter/mount you can thread it in front of virtually any scope, as long as the focal length is around 1m or less likely (you'd have to look that up). For visual safety you need an ITF & blocking filter. For imaging, you could just likely use a blocking filter and internal D-ERF of some kind, but really should use a high transmission ITF & blocking filter (diagonal or not). All etalon systems require the etalon (comb filter, it outputs lots of wavelengths, not just one, they're just spikes of harmonics and narrow) followed by a blocking filter of your wanted wavelength (in this case, Ha) that is narrow enough itself to block the harmonic wavelengths that you don't want, the old ones ranged from around 2A bandpass to now around 6A bandpass, as it can be as loose as necessary to the point that it still blocks the next wavelength output from the etalon. But anyhow, all etalons require a blocking filter after it to get a single wavelength output.

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Re: What can be done with a PST double stack?

Post by daslolo »

got it!
have you tried blocking filters that let two spikes through? i'm thinking ha and sodium or whatever other wavelength has details that match


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Re: What can be done with a PST double stack?

Post by MalVeauX »

Heya,

I have not; because if there's two major lines coming through, the one with more transmission will swamp the other and you'll see basically one. This is why even with a single blocking filter in HA, you still can see the parasitic continuum leaking through and you can still see the brighter photosphere (its so much brighter than the chromosphere, many many times more bright) coming through at the limb despite being sub-angstrom and blocking all but one wavelength. Since we're never truly blocking everything, just most of it. If you had a blocking filter loose enough to let two through? You'd just see the photosphere probably (sodium for example, is much brighter, and shows photosphere features; you'd lose HA most likely as its just dimmer).

I just change filters depending on what layer of the star I want to see. For me, it's just Ha, CaK and then I use a few different filters for the photosphere (as others call white light) in the form of 430nm, 540nm, 610nm and 656nm but with loose bandpasses to continue being photosphere.

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Re: What can be done with a PST double stack?

Post by daslolo »

See, I didn't understand how photosphere got through, now I think I get it: it's just so bright that even at 0.1% pass through in the 500nm range it floods the image.
I get double stack, why not double blocking filter instead? they're cheaper.


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Re: What can be done with a PST double stack?

Post by MalVeauX »

daslolo wrote: Sun Mar 15, 2020 2:45 am See, I didn't understand how photosphere got through, now I think I get it: it's just so bright that even at 0.1% pass through in the 500nm range it floods the image.
I get double stack, why not double blocking filter instead? they're cheaper.
We are all waiting on the 1A blocking filter. :) Once its available, large aperture rear-mounted etalon solar scopes will have quite a new weapon for double-limb suppression. And a 1A blocking would work fine to do this job to avoid two etalons. The problem is finding one manufactured as a hard coated filter. They're still cheaper than a singe Quantum PE filter of any kind. So while it maybe $1.5k~2k per 1A filter, it's still cheaper than any potential high quality double-stack made with large apertures, over 120mm~150mm. That's where the value really comes in, avoiding two of those. There's already a 1.5A blocking filter floating around, but most of us are just waiting on the ability to do a bulk-buy 1A hard coated blocking filter. That'll have a bunch of us instant buying.

Very best,


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Re: What can be done with a PST double stack?

Post by MalVeauX »

VitaminSun wrote: Mon Mar 16, 2020 5:04 am
MalVeauX wrote: Sun Mar 15, 2020 5:49 pm
daslolo wrote: Sun Mar 15, 2020 2:45 am See, I didn't understand how photosphere got through, now I think I get it: it's just so bright that even at 0.1% pass through in the 500nm range it floods the image.
I get double stack, why not double blocking filter instead? they're cheaper.
We are all waiting on the 1A blocking filter. :) Once its available, large aperture rear-mounted etalon solar scopes will have quite a new weapon for double-limb suppression. And a 1A blocking would work fine to do this job to avoid two etalons. The problem is finding one manufactured as a hard coated filter. They're still cheaper than a singe Quantum PE filter of any kind. So while it maybe $1.5k~2k per 1A filter, it's still cheaper than any potential high quality double-stack made with large apertures, over 120mm~150mm. That's where the value really comes in, avoiding two of those. There's already a 1.5A blocking filter floating around, but most of us are just waiting on the ability to do a bulk-buy 1A hard coated blocking filter. That'll have a bunch of us instant buying.

Very best,
Hard coated is not a requirement, but; yes these single cavity hydrogen alpha blocking filters certainly do exist and are indeed floating around.

bf1a.jpg
As far as I'm concerned, hard coated is a requirement, I'm not buying a filter that will last 4 years and then disintegrate it's coatings.

Very best,


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Re: What can be done with a PST double stack?

Post by christian viladrich »

I won't go for a soft-coated filter in 1A. This is a lot of money for maybe 3-5 years life duration.

Regarding hard coated filters, the best are from Materion Precision (ex Barr Associates), well ...this is 15 kUSD per filter for an order of three filters. This is for one-cavity filters/ 40% peak transmisison.Years ago, the price was much lower. They probably changed their commercial policy.
They can do two-cavity filters (which is actually better for this purpose), but the cost is much higher...

Then, there is Alluxa, the cost of a 1 A FWHM / 80% peak transmission / single cavity is in the range of 3 to 4 kUSD per filter for an order of four filters.
I have just ordered a Ca K 0.3 nm filter from them (multi-cavity and> 80% peak transmission) .

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Re: What can be done with a PST double stack?

Post by daslolo »

I see that it is an expensive adventure no matter how you slice it.

Now that I know a little more about sun viewing I must say the view from the Quark isn't bad at all for the price! Just not very contrasty when there is anything to look at these days...


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