With the same approach but different or tunable filters, you can further refine observations and possibly overlay different measurements -- but there you enter the VERY EXPENSIVE territory (Daystarfilters & Luntsolarsystems). Sometimes the different filter- / wavelength images are stacked & colored.


Using a narrow-band filter isn't the only secret to improving solar images. These details will be blurry or even invisible when you watch them through a turbulent atmosphere and don't apply corrections / post-processing. Therefore an additional strategy is to capture lots of images using an uncompressed VIDEO-stream instead of a single still-image. Given the brightness of the sun (even with ERF- or H-alpha filters) shooting at < 1/60s or even 1/100s is very feasible ==> 15...100 frame per second streams are possible. Compared to one shot every few seconds with a SLR (#1)(#2)(#3)(#4).


One opponent to getting sharper images of our planetary neighbors and the Sun is the Earth's atmosphere. Not only does it (unevenly) absorb light's different frequencies, it causes diffraction, and it also is unstable and dynamically distorts observations. On a hot summer's day it is worse compared to a clear cold winter night. Different layers of air (e.g. jetstream) cause additional turbulences in the observation.


It is possible to reduce the impact of these disturbances :
-) short exposure times reduce the motion blur
-) trade-off between short exposure (less motion blur) and more noise (higher ISO)
-) shoot many images and use math to reduce noise and improve details
-) better use a mount capable of tracking the target -- preferably an EQ-mount as the target won't rotate during the observation

This approach isn't proprietary to NASA -- you may have seen some lunar images I took and post-processed with the same technology : /stargazer95050/28740045
The first investment for this type of imaging is the "right" camera -- and it is the opposite of a dSLR -- their flip mirrors cause vibrations and the max FPS and depth of the buffer limit the usability. Suitable (video)-cameras usually are controlled solely via USB + laptop and have no user-interface buttons on the outside. They record uncompressed (AVI) streams. You don't want the MPG compression to throw out faint or tiny details, eliminate stars or reduce dynamic range just because the MPG algorithm classifies that as expendable or noise.
Many of these cameras are monochrome -- when you shoot narrow-band images, there's no point in using RGB. In fact, shooting RGB reduces resolution as 3 out of 4 pixels may be of the wrong color.
UPDATE : The doppler-effect causes a change in the light's frequency -- speed & direction determine the shift. With a color camera & high-resolution CCD, it is possible to measure & display that using a single exposure. OTOH, filters can be tuned and you can use a monochrome camera -- but need to record extra exposures for different filter settings. For solar images, AFAIK are less timing-critical and you can shoot a sequence, alter the filter and shoot the next


What's needed

1. telescope, preferably on a motorized EQ-mount
2. FAST streaming camera (some use analog video cams + digitizer (video grabbers), others USB-based cameras), preferably with high dynamic range
3. laptop with USB connection to the camera plus a lot of free disk space -- the uncompressed AVI stream can occupy as much as 1GB/minute !! even on a small 1MPixel image
4. tool to control the camera and run timelapse and interval shots
5. post-processing video-tool(s) to perform a number of tasks, including preview, trim, crop, resize and resample & convert to other formats
6. astronomy-specific tasks : image-alignment & -stacking, various enhancement algorithms, color & B&W
7. H-alpha and other narrow-band filters aren't a requirement but they benefit a lot from this approach
8. Beautify the images using your existing photo tools
9. Combine the multiple stills into a video timelapse

#1 -- if you read this, it is likely, you already own one
#2 -- (approx 2 years ago) I've picked a DMK-41. In 2014, you may find better cameras -- especially USB3 opens the door to higher resolution & frame-rates but make sure your laptop + HD is fast enough. I haven't seen a need to upgrade, but the DMK-23 is tempting but pricey.
#3 -- is something you likely already own
#4 -- often is included with the camera. I disliked that tool and prefer different freeware tool : SHARPCAP. There are others.
#5 -- a small toolchest of open-source tools + codecs can do all the necessary tasks : VirtualDubMod, Handbrake & TEncoder. Add VLC-player for playback & trim of various formats.
#6 -- AVISTACK2 does a great job when it comes to post-processing these video-streams, be it lunar or solar / H-alpha. AUTOSTAKKERT has been recommended in various blogs and seems to have similar capabilities as AVISTACK and also shows solar image processing abilities.
DEEPSKYSTACKER is NOT SUITABLE for planetary images. REGISTAX may do it but I had no luck. IMO, their focus is on starry deep-sky images
#7 ===> I'll discuss that in the next section
#8 -- use your existing tools to improve TIFF & JPG. For simple tasks IRFANVIEW & FASTSTONE provide many useful features and can apply them across a large batch of images
#9 -- many of the tools listed under #5. Or simply use StarTrails (static stacking) or PhotoLapse (output movie)


The technique isn't unique to solar imaging and in fact I first used it to refine images of the moon and with the exception of #7 solar filter the process is the same. Below you see the result of steps 1)....6) + 8) : /stargazer95050/19370405

For MOON images, it ALSO HELPS TO USE FILTERS -- not the extreme narrow ones used for solar capture. Since the moon is nearly B&W, you can use a single color filter and reduce lens imperfections (aberrations, focus-shift, ...)


H-alpha and other narrow-band filters for solar imaging
The FIRST STAGE of all solar observations is a way to prevent the MASSIVE amount of energy from entering your scope and hit the sensitive sensor (be it eyes or camera). Sophisticated solar observatories and casual eclipse watchers need them -- the effort, precision & cost differs.

When you first try to look at the sun you likely will start will start with the "eclipse shades". And as you start to photograph the sun directly, you will have upgraded to one of several forms of (white) Energy Reduction Filter (ERF). Some really show the sun as a white circle.
Other filters are more selective and favor various colors. The setup that took this shot is similar to this and uses a GLASS filter : www.ipernity.com/doc/stargazer95050/19370235. While I like the resulting color, the (rear) GLASS surface causes a serious problem. Light entering the lens hits the sensor but some portion is reflected back and usually that's no big issue. No one notices a small amount of light bounce back out of the front of the lens -- UNLESS. You add a GLASS filter with the REAR of the filter also reflective. This creates filter glare & ghost reflections at an unprecedented scale.
The only cure to that problem I know is the use of shims or other means to angle the filter and divert these reflections out of sight. The MYLAR/FILM filters don't have this problem and next time I likely will pick one of those (and us editing to tweak the color)

The SECOND STAGE is the actual narrow-band filter. This can be a H-alpha Etalon or way more sophisticated tunable filters. Many H-alpha filters combine the energy reduction & Etalon into a single unit or even a custom telescope (e.g. Coronado ). Other filters still require a reliable ERF reduction (not included in their $$$$ price tag).

The THIRD STAGE, especially with H-alpha Etalons, is a bandpass filter -- often located inside the rear-diagonal. The 2nd-stage filters are narrow, but they let pass the upper harmonics (which still would be powerful enough to do harm to the eyes and distort scientific observations) and this 3rd-stage bandpass eliminates these harmonics. Important for astrophotographers is to pick a diagonal & BF (Bandpass-Filter) with the suitable size. A dSLR (1.5x crop factor) with diagonal of "only" 30mm IMO isn't the best choice for many solar H-alpha filters as most of those are using 1.25" tubes and will cause vignetting. I only have looked at the prices for Coronado BF -- and they become very expensive and hard to come by in sizes exceeding 15mm.

Optional FOURTH STAGE is for observers who wish to further narrow down the bandwidth to see more details. I mention this as 4th stage because it isn't for starters and you may want to add it later on. This "stage" is an add-on to Stage #2 -- basically you combine 2 identical or slightly offset filters to narrow the window of light to let pass through. (It doesn't eliminate the need for Stage #3 / Bandpass Filter)


WHICH TELESCOPE ?
That decision is a complex one for a number of reasons -- trying to re-use an existing telescope may be more expensive than buying a dedicated solar-scope and here are some example to consider

• Do you have a camera capable of capturing high frame rates with a 30mm sensor diagonal ==> look for a system with a 2" wide optical train (including the bandpass filter).
  ==> you can reuse your refractor but the cost to add the filters will be very significant. In return, the resolution will be superior. At a steep price.
• A "budget" solution is an all-in-one combo like the Coronado 60 + BF15. The optical path is not wide enough for DX-dSLRs but sufficient for many of the smaller & faster CCD imagers, like the DMK-41.

As you contemplate telescope & CCD you should ignore the focal length and instead look at the image of the sun projected onto the sensor (of your fast streaming camera). Yes, a larger aperture means (theoretically) higher resolution -- but when your magnification is high, you cannot capture the the full disc of the sun -- do you want to give up that option ? Furthermore, you want to have some margin around the sun to overexpose an image and capture the protuberances

And before you complain about the prices of these telescopes, please look at the price tags of a simple zoom for your SLR. And look at the price of a high-end lens. A telescope is a high-end lens -- don't expect the $99 telescope in the toy-isle to match the quality of your $999 zoom. The telescope delivers much higher magnifications and it is not a surprise these scopes aren't cheap -- they are far less expensive than a 400mm f/4 Nikkor -- and way cheaper than the f/2.8 or 600mm or longer !!


Here are the reasons why I bought the Coronado 60 (400mm f/6.6) + BF15 + DMK-41

• the resulting FOV of that combo is a good match and captures the sun's full circle + room for protuberances : 960 pixel height of the image won't impress SLR-shooters but it is way higher than many TVs and even 720p films. It is close to the HDTV 1080p's vertical resolution.
• The DMK-41 delivers 15FPS uncompressed AVI -- I already own this and that setup was proven ==> no extra costs for HW & SW
• CAUTION : often you see (cheaper) combos with 5 or 10mm bandpass filter -- the 10mm may be very suitable for VISUAL observation. Imaging requires larger image circle to avoid vignetting.
• I have considered the larger Coronado 90mm and decided against it
  - it needs a larger sensor to capture full circle images of the sun -- for me, FULL CIRCLE was a must
  - naturally it also would require a larger BF filter -- and those aren't cheap
• LUNT also makes good solar scopes -- price, availability swayed me towards the "small" Coronado. Plus I have seen results with similar setups and liked them
• possible expansion plans using the "small" Coronado 60 setup while staying way below a 90mm Coronado or other options :
  - adding a BARLOW to increase magnification --> $150...$800 for FFC
  - adding a secondary Etalon to further narrow bandwidth --> ~ $900
  - replacing the camera with a new one --> ~ $1000 for a DMK-23
  I can mix & match them as I want and gradually upgrade
• compare that to the $6000 price for a Coronado 90 (no secondary Etalon, no camera ) : www.optcorp.com/coronado-solarmax-ii-90-bf15.html. Or compare to the $9000....$3000 for daystar filter alone (add camera + scope) : search/result/index/q=daystar

As mentioned in the introduction, solar imaging with narrow-band filters is a very specialized challenge and it requires investments. And as usual, there is not much of an upper limit but the lower entry-point is IMO a 60mm Coronado with BF + camera. You also can use a LUNT-scope.
Or you can use your current telescope and go a DIY route by adding a ERF filter, find a suitable adapter to fit your scope, add Etalon & bandpass and fit that into your optical path. And add a (fast, monochrome) camera. The off-the-shelf solar-imaging solutions are much cheaper because they are designed for much smaller aperture and smaller image circles.
Given the brightness of the sun, a telescope with a huge aperture is not necessary and the cost of the various adapters usually outweighs the cost of a moderate solarscope-combo (even after you add some extras)

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LINKS to dowloads :
SharpCap2 : www.sharpcap.co.uk/sharpcap/downloads
FireCapture : firecapture.wonderplanets.de
wxAstroCapture: arnholm.org/astro/software/wxAstroCapture/#WINDOWS_INSTALL
AVIstack2 : www.avistack.de/download.html
AUTOSTAKKERT :
VirtualDub : www.virtualdub.org
Handbrake : handbrake.fr
TEncoder : sourceforge.net/projects/tencoder
VLC player : www.videolan.org/vlc/index.html
DEEPSKYSTACKER : deepskystacker.free.fr/english/index.html
REGISTAX6 : www.astronomie.be/registax/download.html


NOTES :
(#1) Shooting RAW, dSLRs can achieve 5..12fps -- but they cannot sustain that speed. Usually the buffer is large enough for 10...20 RAW images -- OTOH when streaming video, there usually is no buffer limit
(#2) When using a SLR on a telescope, you need to be careful to avoid vibrations from the shutter and that's another reason rapid-fire SLRs aren't a good choice for this type of observation
(#3) dSLR can record video -- but IT IS COMPRESSED and limited to 8bit/channel. For the post-processing the extra fine details are important and CCD cameras can provide uncompressed 8...12bit monochrome data at 15...60fps (and 1...2MPixels)
(#4) tethering a dSLR to a PC via USB can have unwanted side-effects. Depending on camera model & software it WILL NOT store images in the camera but all shots must be instantly downloaded to the PC -- that can take several seconds per shot.

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