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marktownley
Carpal Tunnel
Reged: 08/19/08
Posts: 2272
Loc: West Midlands, UK
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Found myself having a solar 'ponder' this afternoon seeing as the clouds have returned and wondered what folks experiences were...
Double stacking a Ha scope results in great contrast and detail on the disk, filaments are easier etc - i've seen this in the pickies from you folk and also from a brief visual foray with a DS unit.
Now I know the proms become fainter and harder to see visually in a DS, but how does this affect things from an imaging point of view? With the camera as they are fainter does it pull out more detail not seen in a SS if the exposure is cranked up, or with proms is it the same detail just fainter in a DS?
Does anybody know / have experience of this? does anybody have any 'comparison' pics that could illustrate any differences, if indeed there are any?
Daydreaming on a sunday afternoon,
Mark 
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stephenramsden
Pooh-Bah
Reged: 08/17/07
Posts: 1326
Loc: Atlanta, GA--USA
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Mark,
Did you say clouds.. ? Oh boy. The new scope curse, huh?
Double stacking any etalon reduces the overall image brightness by 40% visually or photographically. It can be compensated for by adjusting gain but you still get the standard additional graininess when you add gain.
--------------------
Stephen W. Ramsden
Atlanta, GA--USA
NASA SOLAR SYSTEM AMBASSADOR
www.solarastrophotography.com
www.SolarScopeReviews.com
www.stephenramsden.com
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solarGain
super member
Reged: 07/18/09
Posts: 135
Loc: London & la Palma, Canary Is.
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Mark try this site. I'm going thru the archive.
http://dot.astro.uu.nl/albums/images/album.html
John
PS I have made a real hash of this sorry.
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Solar eclipse chaser: Madagascar 2001, Libya 2006 and booked for Easter Island 2010.
PST Original blue . Manfrotto head/tripod x2.
Denk PST corrector, 21's & Denk II Binoviewer, wow!
Denk Bino/lunt diagonal adaptor.
Lunt LS100THa/ B1800 (Pressure-tuned) w/ Feather touch focuser. Vixen GP2 motorised ,& Vixen pier.
added 07 24 2009
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solarGain
super member
Reged: 07/18/09
Posts: 135
Loc: London & la Palma, Canary Is.
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Mark I don't yet know how to do a linked thread back to the archive but this is one of Pete Lawrence' post from way back. ""Another SS vs DS comparison
#2325636 - 04/14/08 06:22 AM""
It came up in my trawl 30 mins ago. Good luck John
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Solar eclipse chaser: Madagascar 2001, Libya 2006 and booked for Easter Island 2010.
PST Original blue . Manfrotto head/tripod x2.
Denk PST corrector, 21's & Denk II Binoviewer, wow!
Denk Bino/lunt diagonal adaptor.
Lunt LS100THa/ B1800 (Pressure-tuned) w/ Feather touch focuser. Vixen GP2 motorised ,& Vixen pier.
added 07 24 2009
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swisswalter
sage
Reged: 03/29/09
Posts: 417
Loc: Eastern-Switzerland
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hi mark
yes i did the comparison several times at differnt days, see also my folder at yahoo (walter's sun). i did not get any useful results, nor enhacements in DS mode
walter
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only dust in the wind, TAK on GM8, Lunt 60, DMK31,still greenhorn, but as a golfer used to be humble
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Keith Howlett
scholastic sledgehammer
Reged: 03/06/07
Posts: 977
Loc: Northumberland, UK
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Hi John,
This one... Another SS vs DS comparison
Cheers,
Keith
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DAVIDG
Carpal Tunnel
Reged: 12/02/04
Posts: 1990
Loc: Hockessin, De
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Resolution is set by the aperture of the telescope and contrast by the bandwidth of the filter. The resolution of a single stack vs a double stack solar telescope of same aperture is the same. What the double stacking does is improve the contrast, making the features easier to see and photograph.
When your talking about promeninces and not surface features, too narrow a bandwidth will reduce the features that can be seen. The material in the proms can be moving at very great speeds which causes Doppler shifts. The shift in frequency can make part or all of proms in invisible when tuned to 656.28nm
If you really want to see prominences at their best then view them through a coronagraph that has a bandwidth of around 2 angstroms. The contrast will be very high since the design of a coronagraph eliminates stray light and occults the disk of the Sun, leaving a bright image of the prominences against a black background. The larger bandwidth allows all the features in a prom. to visible at the same time.
- Dave
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Homemade 'scopes 8"f/7,6" f/5", 6"f/4, 4.25" Schief. 60mm Coronagraph,60mm H-alpha system, 4.25" White-light Solar Newtonian,solar spectroscope, 4.5" f/16 Schupmann Medial refractor, 14 Stellafane awards 7 in optics
Engineering = Taking what you have and making what you need.
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marktownley
Carpal Tunnel
Reged: 08/19/08
Posts: 2272
Loc: West Midlands, UK
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Thanks for all the responses guys.
I think what was in the back of my mind when asking the question was the setup needed to produce the ideal composite disk / proms shot.
Taking my SM40 as example: If it was double stacked then (for the aperture it is) it would produce the optimum views / pickies for disk shots. However, for the prom bit of the composite then the best views / pickies would come from the SM40 when it was SS.
Now, a further question on this mind exercise: Would a PST therefore give better prom shots with it's 1A bandpass, as opposed to the 0.7A bandpass of the SM40?
Anybody got any comparison shots of the same proms taken with an SM40 compared with the PST?
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Fish
sage
Reged: 10/13/07
Posts: 470
Loc: Norridgewock, ME
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Good evening,
Actually, the best bandpass for prominences is around 1.5A but at this width any surface detail is washed out by energy leaking through from the photosphere. Filters of this width are available but since most people want to see both surface and edge detail, the 0.7A filters remain the best compromise.
Given this, a <1.0A PST promience image combined with a suface shot from an SM40 SS or DS can provide very nice 40mm performance.
Regards, Marc
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Goseck Observatory
Kunming 152 f/5.9 & Baader Wedge
Orion ED80 & LS75FHa2/B1200
Meade 102ED & LS18CaKMDd2
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Tom Masterson
member
Reged: 08/08/09
Posts: 14
Loc: Pacific Northwest - Astronomy'...
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As mentioned above, you will lose some details in the proms with the double stacked system due to doppler shifting. The tendancy would be to lengthen exposure to show more of the prominence but this can cause problems because atmospheric turbulance begins to blur the image. Plus you can't get back the features that the narrower bandpass has filtered out.
I like to take a shot with a single etalon for the prominences and combine it with a doublestacked shot for the disk.
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Tom
12" Meade LX200 Classic
AstroPhysics 6" f/8
Brandon 94 f/7
Meade 30mm 5000 UWA, my primary weapon
20mm Nagler Type2, my back up weapon
16 and 12mm Nagler Type2s, in case the first two didn't finish 'em off
17mm and 13mm Stratus, 9mm and 6mm TMB Planetaries
Coronado ,6a SMn-35 w/90mm ERF
Lunt LS50/BF1200
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