Observing the Sun?

[oymd]

Hi all..

Solar scopes seem expensive...

Can some one please explain what are the benefits of a dedicated solar scope over a solar filter on a regular scope?

Thanks

[michael.h.f.wilkinson]

Essentially there are two types of solar filters: white-light and single-spectral-line filters. White-light filters block 99.999% of every wavelength of light making it safe to view the sun. The details you see are in an outer layer of the sun called the photosphere, where most of the light we see emanates. This allows you to see granulation and sunspots. White light is as cheap as it gets: Baader solar film costs a few tenners and gives great views. White-light solar filters can be added to any scope.

White Light example

Single-spectral-line filters block almost all wavelengths completely, but allow most of the light of just one very narrow passband through (<0.07nm compared to > 5 nm for most narrowband filters used in DSO imaging). Most often the H-alpha wavelength is transmitted, and this allows observation the chromosphere, which is a layer just outside the photosphere. The details seen are typically prominences and the like. These filters are much more expensive. They can be added to an existing scope, but that solution is often as expensive as a dedicated solar scope. The results are more spectacular.

H-alpha example

[Bizibilder]

A solar filter (Like Baader film) simply reduces the amount if light passing through the telescope to a level where either visual or photographic observing is possible (and safe!). It does not filter the light and you see a "white light" image. You can see the general surface of the Sun and the dark sunspots and brighter faculae.

A dedicated solar telescope is completely different. They generally have a filter system that only allows a very particular wavelenght of light to pass. This is in the red part of the spectrum and is the light associated with Hydrogen (It is called Hydrogen Alpha or Ha). It has a wavelenght of 656.281nm (nano meters). These filters and the associated bits and pieces are not cheap as you can see from the prices of dedicated solar scopes! With these scopes you can see things like prominences and far more surface detail.

A bit simplistic but I hope it helps.

(PS These HA solar scopes are NOT the same as an Ha narrowband filter used for astrophotography!!!)

[Sammyb]

Excellent responses to the original post

[jonathan]

With a dedicated solar scope you are only looking at one target, the sun, as such it is a highly specialized scientific instrument and can show far more than any other amateur method. The depth of your pockets dictates how much detail of the sun you will be able to see / photograph through one. As well as the Ha scopes which are primarily useful for visual observing, there's also the Ca-K which is used more for photography.

It should be said that solar observing comes with a responsibility to yourself to exercise extreme caution, you really need to ensure that the scope is configured correctly so that it is safe, if you use a solar film on an ordinary telescope then you must inspect the sheet on each observing session, remove or cover the finder scope, etc. Failure to observe precautions could lead to blindness and/or destroyed equipment.

[oymd]

wow...

Many thanks for the excellent explanation...

I'm learning something new every day on this great site..!!

[stevepeverall]

Two great images there Michael.

Do you know how the appearance would look as a visual user if you used a Baader Solar Continuum Filter like this in combination with the Baader Film that goes over the objective lens? Would the view look similar to the orange second image?

The reason that I ask is that i have just bought the Baader Film Filter and was wondering whether it is worth spending an extra £60 on the BSCF?

[stevepeverall]

Sorry, Baader Solar Continuum filter like this:

http://www.firstlightoptics.com/solar-filters/baader-solar-continuum-filter.html

[AndyWB]

At the risk of thread hijacking, I've some questions:

- How come Coronado PSTs seem much cheaper than other solar scopes?

- Ca-K - is that the purple images you see sometimes? Why is that mainly photographic? Spectral range?

- What the heck is double stacking? I keeping seeing the term, but it conjures some pretty weird images...

[Stu]

Two great images there Michael.

Do you know how the appearance would look as a visual user if you used a Baader Solar Continuum Filter like this in combination with the Baader Film that goes over the objective lens? Would the view look similar to the orange second image?

The reason that I ask is that i have just bought the Baader Film Filter and was wondering whether it is worth spending an extra £60 on the BSCF?

The BSCF makes the image appear green, and just enhances some of the detail you can see. It mainly assists in bringing out the surface granulation but is fundamentally still just looking at white light, albeit filtered to a narrower band.

It won't approach the second orange image as this is based on a specialist Hydrogen Alpha scope filtering to a very narrow bandpass which will show the prominences and filaments amongst other things.

Stu

[Stu]

At the risk of thread hijacking, I've some questions:

- What the heck is double stacking? I keeping seeing the term, but it conjures some pretty weird images...

Double stacking uses two etalons to reduce the band pass on a PST for example from sub 1.0A to 0.5A. The same basic idea can be applied to any solar Ha scope.

http://www.harrisontelescopes.co.uk/acatalog/Coronado_Personal_Solar_Telescope_0.5A.html

The effect is to give much better definition to surface granulation and other features, but I believe this is at the expense of brightness in the prominences.

From what I have read, single stack is good for visual, double gives better results for imaging, certainly on a small aperture like the PST. With more aperture I'm sure double stacking would be amazing visually.

Stu

[Zakalwe]

- How come Coronado PSTs seem much cheaper than other solar scopes?

Its not. The Lunt L35 is £645 at Green Witch. The PST is £659. I'm not sure if there is anything else at that end of the market?

- Ca-K - is that the purple images you see sometimes? Why is that mainly photographic? Spectral range?

Ca-K is barely visible to the naked eye. And the eye lens hardens with age, making Ca-K harder to see. Therefore it's mainly imaging.

- What the heck is double stacking? I keeping seeing the term, but it conjures some pretty weird images...

It refers to putting another Etalon in the imaging train to narrow the bandpass. This can bring out more detail at the expense of making the image darker.

[stevepeverall]

Cheers Stu

[AndyWB]

Thanks chaps, that's interesting and helpful.

[Peter Drew]

PST's "seem" cheaper pro rata than some other Ha telescopes as it has a small internal etalon rather than an external full aperture one. The etalon is the most expensive part of the system.

[oymd]

wow...and when I started this thread, I thought that the simple answer would be that a solar scope uses a special glass or something!!

etalons, nano meters etc....pretty complicated!!

[michael.h.f.wilkinson]

PST's "seem" cheaper pro rata than some other Ha telescopes as it has a small internal etalon rather than an external full aperture one. The etalon is the most expensive part of the system.

Many dedicated H-alpha scopes have internal etalons (like the Lunt LS60, LS80, etc). My LS35 has a front mounted one. The advantage of the PST is that it can be modded into something bigger quite easily.

[peroni]

Great explanation to a question I hadn't even considered (unsurprisingly )

I tried the Baader solar filter from FLO this summer and was pleasantly pleased with the results.

A good entry level introduction before shelling out on another scope.

Sent from my phone :-D