H-Alpha/Solar observing questions

[MimasDeathStar]

I heard the sun wasn't very active at the moment. Is it still active when you look through H-Alpha? (I don't really understand the difference!)

[Rob Sellent]

1 hour ago, MimasDeathStar said:

Thats fab really nice colour rendition. I heard the sun wasn't very active at the moment. Is it still active when you look through H-Alpha? (I don't really understand the difference!)

Broadly speaking, white light filters show you the photosphere, H-alpha the chromosphere.

In astro-terms, white light viewing is quite cheap. You can purchase a dedicated solar filter that fits over the scope's front end, you can buy just the film and make your own filter and if you own a refractor, you can up grade to a Herschel Wedge.  White light features include observing sunspots (the umbra and penumbra), light bridges, faculae and limb darkening.

Hydrogen-alpha (H-alpha) filters work by transmitting only one specific wavelength of light seen as the red colour through H-alpha solar filters. Due to this very specific nature of design, H-alpha filters are significantly more expensive than white light filters. Typically, astronomers buy dedicated H-alpha refractors either at 50mm or 60mm or dedicated eyepieces that are used with good quality refractors and due to the nature of the eyepiece, preferably quite fast refractors. H-alpha features include plages, flares, spicules, filaments and prominences.

There is also the possibility of using Ca-K filters but due to this wavelength and the inability of many eyes to see detail at this wavelength, Ca-K filters are more commonly used by imagers.

At the time of writing the Sun in white light is relatively inactive. Perhaps as much as every 100 days or so, only 30 will show signs of sunspots. I imagine we're on course for another year of relative inactivity and then gradually we'll pull out of the slump. Needless to say, in H-alpha there's generally something to view - albeit not always spectacular - every day.

Both white light and H-alpha have their pleasures and most solar observers wouldn't want to go without either.

Finally, from the words of Ant:

Never, ever look at the Sun directly through any optical instrument - instant blindness could be the result.

Even looking at the Sun with the naked eye can be harmful.

DO NOT look at the Sun with magnifying glasses, cameras, binoculars or telescopes, any optical instrument in fact, without the use of a properly designed, approved and tested filter or specialised instrument.

DO NOT use photographic film, smoked or tinted glass, plastic or metal film.

Use only materials and instruments designed for the specific purpose for viewing the Sun.

If in doubt, seek expert advice first!

Edited September 8, 2019 by Rob Sellent

[MimasDeathStar]

On 09/09/2019 at 00:00, Rob Sellent said:

In astro-terms, white light viewing is quite cheap. You can purchase a dedicated solar filter that fits over the scope's front end, you can buy just the film and make your own filter and if you own a refractor, you can up grade to a Herschel Wedge.

Thanks Rob thats really useful. I just spent 20 minutes googling what half of those things were; it was very interesting I had no idea there was so much going on!

Would you say a Herschel Wedge is a significant step up from a solar filter? They seem much more expensive are they like 5 times better or doesn't astronomy work like that? Although I think I'll just get a solar filter to start with anyway so it probably doesn't matter.

Bad news about the activity - although I read about why which was fun to learn. Although as an absolute beginner it probably wouldn't do me any harm to start off slowly! At least I know if I'm starting off at solar minimum (just learnt that woo) then things can only get better!

Thanks again.

[Rob Sellent]

@MimasDeathStarThe Baader solar film (there's visual grade & imaging grade) is excellent for white light. It is of excellent quality, gives good contrast and is cheap. Many observers claim that there's visually no difference between the film and wedge.

For a good couple of years I used Baader's solar film until I was sure that 1) I really liked using refractors and 2) enjoyed solar observing, and only then did I purchase a wedge. For me the Herschel wedge has the advantage that it does not deteriorate, can be used on different aperture refractors without having to get new filter sizes and is safely in my hands rather than fitting over the tube end which always made me a little nervous. Image quality is extremely good, it is sharp and contrasty but perhaps it is only better-better than the film under very good seeing conditions.

For the cheap price of the filter while adding another dimension and knowledge to astronomy, I really think every observer should have the Baader filter. And as you so rightly say, with this solar slump the only way is up 🙂

- - -

@StuJust wanted to say thank you to Stu for kindly setting up this thread, so as not to disrupt or derail the original OP in sketches 

Edited September 10, 2019 by Rob Sellent

[MimasDeathStar]

Thanks Rob thats good news for my wallet if nothing else.

Thanks everyone, apologies for derailling the other thread, I was just getting carried away!

[Stu]

1 hour ago, MimasDeathStar said:

apologies for derailling the other thread

Really not a problem. Rob just thought you might get some more input this way. All good

Welcome to the forum by the way