General solar observing questions from a beginner

[choochoo_baloo]

Hello all,

I am a new amateur astronomer (I own a 6" reflector), but wished to just clear up my understanding of solar observing, after watching some videos and it being mentioned on Stargazing Live tonight.

Firstly, if I fitted a decent (e.g. Baader) solar filter to the end of my normal Newtonian reflector, what would I see with my eye: the white disc with sunspots and maybe some flared around the periphery? Am I right in saying that to see the 'textbook' appearance of the Sun - deep orange colour, grainy surface, clear sunspots and orange flares from the surface - requires a standalone Hydrogen alpha telescope? Ie to get really good results requires a discrete telescope designed to only transmit the very narrow band of wavelengths that allow this sort of view?

Secondly, assuming the H-alpha type is needed, sorry if this is a daft question, but I assume the 'textbook' appearance I described above will be fully visible in the eyepiece and is safe to human eyes?!

Thirdly, assuming the usual physical issues of correct focusing on a small solar telescope can be overcome, can video be taken through a suitable eyepiece so as to then successfully stack and reproduce the described 'textbook' image I saw with my eye as a digital photograph?

Thank you, any help appreciated.

Matthew

[Moonshane]

hi Matthew

broadly you will see the sort of image show in this thread http://stargazerslounge.com/topic/204340-sun-in-white-light-7-1-2014-1215-gmt/ with a baader film. make sure the filter is sturdy and cannot come off the scope. you won't see any prominences etc in white light as you are looking straight through them.

other than that your answers are all pretty much yes to all questions.

[JamesF]

A solar Ha telescope takes the incoming light and rejects a huge amount of it, just passing some of the very narrow band of visible light centred on the wavelength of light emitted when an electron "drops" from the third to second energy level in the hydrogen atom.  This is about 656nm, which is the "textbook" red-orange colour you mention.  The amount of light rejected makes this safe to view, and because it is in the visible spectrum is visible to the human eye.  A specialised telescope is required for this firstly because the filter is so narrow and secondly because sufficient energy has to be rejected to make the final image safe to view.  Whereas DSO imagers might use a 7nm or 3nm "wide" filter for Ha imaging, a solar Ha telescope typically passes less than 0.1nm (from memory I think the PST is 0.07nm) centred on the Ha wavelength.  There are then additional filters to reduce the intensity to a safe level.

It's quite possible to use a standard fast frame rate camera to capture that image and stack/process the details in much the same way as you would for a lunar or planetary image and when the weather allows you will see a number of such images posted here.

James

[JamesF]

I should add, generally you'd use a mono camera for capturing Ha images, because there's no green or blue component to the image and attempting to use a colour camera would mean that 75% of the pixels were effectively unused.  The mono image often then has the red-orange colour added back during processing.

James

[choochoo_baloo]

Thanks both.

I am afraid I am still slightly unsure what is visible with eye and then camera per frame, and then stacked.

I'm reading physics at university currently, so have a good grasp of electron excitation etc thus why the particular Hydrogen transition is what we're interested in for these sorts of Solar temperatures.

However please find attached two images off of the internet to illustrate (hopefully) my slight confusion (obviously ignore the magnifications, I'm mainly interested in just comparing colours):

As James said, I would have thought that the ~ 1 angstrom band on Coronado PST etc would produce an image like the top photograph. Since surely the visible red wavelength that corresponds to H-alpha would be all that is transmitted?

However I read elsewhere that more orange images, like bottom photo', (the 'textbook' ones I referred to in my original post), are immediately visible by eye on a proper standalone solar telescope (e.g. Coronado PST)?

In either case, is stacking (for digital photography) required to get the resolution and detail in a photograph from amateur grade cameras that we use at this level? Ie what would a properly focused single frame (if the bottom image is seen by eye) on a DSLR look like?

Many thanks in advance.

Matthew

[StevieDvd]

With a simple filter to view/image the sun (white light) you will see sunspots, some granularity and unlikely to get any prominences or flares. These filters can be false coloured to give a green or orange/yellow cast to the viewed image but most folk suggest using a mono camera and adding your own colour cast post capture.

The HA scopes like the Coronado do show a red image, but can visually see both surface details and flares/prominences. Again though most imagers will use a mono camera and add colour post capture. Where you see the ncie ornage images on the internet with great surface detail and flares etc these are usually a composite image, one exposed to show surface detail and a longer exposure to capture the prominences.

Post processing as you have initimated does usually involve using a stacking software to get the best 'additive' image, these are then coloured & tweaked to pull out the detail and finally overlayed on a seperate processed flare/prominence image.

White light filters can be a few pounds and home-made up to more expensive glass based filters and dedicated wedges (see Baader Herschel wedge in google for higher end example & price).

HA scopes are a lot more expensive than standard telescopes, let alone filters. Starting from several hundreds of pounds to several thousands. These can be tweaked for viewing or imaging depending on requirements.

If you go down the imaging route your pictures will look better than most viewed if processed properly. 

[choochoo_baloo]

Thanks all.

Does anyone have a suitable link to photographs (preferably both singles and stacked etc.) taken through the Coronado Personal Solar Telescope (apparently with adapters fitted it can be done)?

[JamesF]

As James said, I would have thought that the ~ 1 angstrom band on Coronado PST etc would produce an image like the top photograph. Since surely the visible red wavelength that corresponds to H-alpha would be all that is transmitted?

However I read elsewhere that more orange images, like bottom photo', (the 'textbook' ones I referred to in my original post), are immediately visible by eye on a proper standalone solar telescope (e.g. Coronado PST)?

In either case, is stacking (for digital photography) required to get the resolution and detail in a photograph from amateur grade cameras that we use at this level? Ie what would a properly focused single frame (if the bottom image is seen by eye) on a DSLR look like?

To my eye, the visual appearance in a PST is a closer colour to your top image.  That is all that is transmitted.

However, as the images are generally captured in mono (that is, greyscale), the false colour applied is up to the imager, who may prefer a slightly more orange colour as in the second image, often because rightly or wrongly (wrongly, let's be honest) that's the colour people perceive the Sun to be.

A DSLR (or any colour camera) is not really desirable for solar Ha imaging, because three quarters of the pixels (the blue and green ones -- half the total will be green) in the colour mask will end up with no data, which doesn't make for a good image.

James

[JamesF]

Thanks all.

Does anyone have a suitable link to photographs (preferably both singles and stacked etc.) taken through the Coronado Personal Solar Telescope (apparently with adapters fitted it can be done)?

Look for images in the solar image section posted by Montana.  She often posts images for Ha and CaK using the PST and a mono CCD camera.  I don't off the top of my head know of any single-frame examples I'm afraid.

James