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Alan White

PST, can someone explain simply what it is and what it does?

14 posts in this topic

Having been bitten by white light solar observing late last year and I have a lunt herschel wedge.
I keep reading about PST and other set ups, but not having seen one have not a clue.

Will you avid solar observers please explain please?
(some pictures would help).

I am new to solar and have not really grasped all the options yet.

Also any one single web site or books recommended?

As always your help and patience with me is appreciated.

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I'll have a quick go....

Basically it is an entry level Hydrogen Alpha (Ha) telescope that allows you to observe solar features in Ha such as prominences and filaments. Everything you need to observe safely is built in, you just put an eyepiece in it, and obviously it needs a mount.

It has two main adjustments, firstly focus (obviously) and secondly tuning of the etalon which determines the exact frequency which is being passed through. This helps you tune in to different features such as surface detail or prominences.

I had one for a while and really enjoyed it. The current alternative would be the Lunt LS35 or Lunt LS50 which are worth a look.

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Thanks Stu, I sort of get that.

I take it that the viewing is different to White Light in (Ha) then?

Why are you and others modifying a PST?

 

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Alan when you view the Sun with your Herschel Wedge you are seeing the Photosphere - sunspots, granulation etc. A Hydrogen Alpha scope looks at the Chromosphere and the attached website shows some of the details that are visible with a H.A scope - https://www.astroleague.org/content/hydrogen-alpha-solar-observing-program

I have owned a PST since 2005 and it has been a wonderful instrument. Many people undertake a PST modification to obtain a larger instrument by finding a donor scope - 80mm etc.

H-A scope are expensive and a 60mm Lunt with a larger blocking filter can cost £2000+

 

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OK guys thanks for the information. So my question is can  solar observing in Ha be done safely with say a six in frac   And if so what kit needs to be bought.

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Thanks Mark and again Stu, that also helps.

The Astroleague link was an easy in and read, helpful.

The modification of a PST.
Is that a Coronado PST somehow grafted with a larger scope?

As Garry says above, can a big refractor be modified or is the aperture limited somehow?

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26 minutes ago, Alan White said:

Thanks Mark and again Stu, that also helps.

The Astroleague link was an easy in and read, helpful.

The modification of a PST.
Is that a Coronado PST somehow grafted with a larger scope?

As Garry says above, can a big refractor be modified or is the aperture limited somehow?

Yes, 6" refractors can be modified to view Ha. This is generally done by modifying a PST which means taking the back end of a PST (the etalon and focus mechanism) and grafting it onto the larger scope. You must know what you are doing to do this, it involves replacing the safety filtering provided by the PST front end with a D-ERF which filters out most of the harmful energy from the sun.

@Peter Drew and @Merlin66 are two of the acknowledged experts in this area, and infact Peter made the scope I am using, which is a 4" Vixen f10. There is plenty of info on the forum about these mods.

The simple reason for modding PSTs is to bring additional resolution (and brightness) to the views, and they are very good.

Another way of achieving similar results is to use a Quark. This is a powered unit which fits into the diagonal and accepts an eyepiece. This provides the filtering but it also requires additional energy rejection depending upon the aperture of scope you use it in. They do work very well in the 152mm f5.9 scopes from Altair Astro and Teleskop Service.

The Quarks include a x4.2 Barlow so generally provide lovely high magnification views in larger scopes, although they will show full disk in small, shortbfocal length scopes.

PST Mods can provide full disk views but also high quality high mag views so are perhaps a little more flexible.

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Again thank you Stu, you are helping me grasp this.
Time to start putting more than pennies in the piggy bank I think.
 

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12 hours ago, Stu said:

Yes, 6" refractors can be modified to view Ha. This is generally done by modifying a PST which means taking the back end of a PST (the etalon and focus mechanism) and grafting it onto the larger scope. You must know what you are doing to do this, it involves replacing the safety filtering provided by the PST front end with a D-ERF which filters out most of the harmful energy from the sun.

@Peter Drew and @Merlin66 are two of the acknowledged experts in this area, and infact Peter made the scope I am using, which is a 4" Vixen f10. There is plenty of info on the forum about these mods.

The simple reason for modding PSTs is to bring additional resolution (and brightness) to the views, and they are very good.

Another way of achieving similar results is to use a Quark. This is a powered unit which fits into the diagonal and accepts an eyepiece. This provides the filtering but it also requires additional energy rejection depending upon the aperture of scope you use it in. They do work very well in the 152mm f5.9 scopes from Altair Astro and Teleskop Service.

The Quarks include a x4.2 Barlow so generally provide lovely high magnification views in larger scopes, although they will show full disk in small, shortbfocal length scopes.

PST Mods can provide full disk views but also high quality high mag views so are perhaps a little more flexible.

Thanks for the information Stu most grateful for the clarity you have produced, as it happens I have the 152 AA on order.

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The 152 AA will be ideal for a Quark for Ha but a PST mod would reduce the effective aperture to 90mm as the 20mm etalon of the PST will vignet the 152 to F10.  

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I would highly recommend getting a PST as an entry to the wonderful HA world ... I wouldn't necessarily worry too much

about modding one until your fully conversant with all things HA ... modding will certainly achieve greater resolution

but won't lower the units bandwidth and can sometimes offer fairly blank disk views.

 

Brian 

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+1 for this good advice although I can't recall seeing a blank disc so far with my 6" PST mod. :icon_biggrin:

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Piggy bank to be fed copious quantity of wonga to allow PST purchase.

Do these come up used much?

Any units recommended as a starter unit?

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Have you considered a second hand Lunt LS35? I bought one from a fellow member of this community. Very happy with it indeed and relatively affordable if you can find a used one. Just a suggestion. 

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