Stacking Solar scopes

[sophiecentaur]

As usual with specialist subjects, everyone uses the specialist terms an it can be confusing. I would really appreciate a two line resumé about stacking filters. How does stacking help for a sub Angstrom filter? How to get the two lines in the same spot?

Also, the Coronado seems the cheapest entry level option but will it limit me from progressing further? Is there much mileage in a Lunt wedge for my nice 80ED refractor and an internal etalon? It seems a shame not to be using the 80mm but I guess that CA is not an issue.

[xtreemchaos]

quark chromosphere by daystar its all you will ever need and you can use it with any doublet achro up to 150mm as long as you have a ERF fitted, works out a lot cheaper than a double stack system.  charl.

[sophiecentaur]

Thanks for the comment. I was beginning to think that myself and there seems to be a ready supply of s/h quarks. Perhaps it's an object that has limited long term appeal. Once you have been really impressed by some really dramatic features, that's more of less it unless you want to make a real study. Otoh, the night sky is full of variety. Of course, there will be people who fall in long term love with it.

[Freddie]

If you are thinking of a second hand Quark I would suggest you either see it for yourself or see an un processed image before buying as there is a wide variance in quality unit to unit.

[Peter Drew]

I agree with the previous posts but if solar viewing interests you at all it is seldom boring as every day (hour/mimute), presents a different view.

[xtreemchaos]

agreed Freddie, I had a try before you buy option with my one, also had a friends DS lunt to compaire ,I found the Quark more to my liking just for close up contrast and detail, the lunt DS was very good I couldn't pick a winner out the 2 but the quark would cost £700 against the lunt ds which was nearer £ 3000 so really the price swayed my heart. charl.

[Highburymark]

I've just done report of my new Lunt 60 DS in members equipment reviews - quite relevant to this discussion

[Merlin66]

I used a Coronado 60 double stack set-up for many years. No issue no drama.

To answer your original question Re double stacking. Each of the etalon filters are "tuned" to the H alpha central wavelength. The shape of the transmission curve albeit very narrow, approximates to a Gaussian bell curve.

When the two bell curves are superimposed on each other, the total transmission is reduced by around 50% and the final transmission  bandwidth by approx 40%. If two, say 1.0A filters, are stacked, you get around a 0.6A result.

 

[Solar B]

What about triple stacking Ken .... here with

a DS60 / SM40 ... a dull image granted 

but if one were to use another SM60

and only 1 external ERF then the image may

be quite manageable I suspect but would the 

bandwidth decrease pro rata ?

 

Brian 

 

[Merlin66]

Brian,

Interesting set-up....

Yes, theoretically the triple stack would further reduce the bandwidth - SS 0.7A, DS 0.5A, TS 0.35A and reduce the transmission to 0.8 x 0.8 x0.8 = 50% Removing the ERF is of limited value - the transmission of the ERF is around 90%.

Tuning a triple stack will call for some rigor. Each etalon must be tuned to almost exactly the same CWL......

 

[Merlin66]

The original OP..

The wedge is perfect for white light viewing - sunspots, granulation and brighter surface faculae - you need the expensive narrow band Ha filters to be able to see the filaments, prominences etc. A double stacked (or Quark) configuration allows finer detail to be seen on the surface (improves contrast).

Hope this helps.

 

[Solar B]

A Herschel Wedge is for viewing the Suns Photosphere

A Hydrogen Alpha Filter is for viewing the layer above known as the Chromosphere 

 

Brian 

[Merlin]

Not everyone will agree, but I prefer H-a viewing to white light, although, to be fair, the first deals with chromospheric detail and the latter with photospheric detail. It's just that there seems to be more going on at the chromospheric level, including majestic prominences. 

I have a Lunt  ( LSF50 ) double-stacked to a PST. The two etalons seem perfectly matched.

[xtreemchaos]

whitelight Vs HA eh, I love the disc detail coverage and contrast in HA which makes the processing much easer. But Whitelight is where my heart lays , theres nothing like a well processed shot of a nice big sunspot, WL wins in detail sharpness by a mile. I think its good to do both. charl.

[sophiecentaur]

Whew. That was a load of interesting stuff. I think a Quark may be the way for me to go for a start. The filter stacking effect is what I would have expected but i didn't realise the significance of it. 

Solar viewing really suits a lazy devil like me. A warm, bright, clear afternoon and a small telescope wins over the hope that it's worth while staggering out at midnight with a lump of Newtonian and ten layers of clothing. I could grow to love the sun.