What a view... (June 10th)

[Starman]

A new active region on the eastern limb which appeared yesterday, is now framed nicely with a rather lovely looking prominence close by. There's another nice prom a bit further along which I'll add in later.

[MrEd]

Lovely Stuff Pete.

Looks like you timed that shot just right.

Nice to see the new cycle underway.

Ed

[Starman]

Thanks Ed

[barkis]

You were on the job early for this one Pete. Well worth it too, It's a wonderful sight is that.

Ron.

[Starman]

Thanks Ron. Just putting together a wider field view now...

[CELESCOPE]

Now i know why the sun always shines in Selsey , blimey pete the sun loves you , even puts on a great show for you now , .

Splended image , love it

Rog

[SteelRat]

Yup, very nice solar prom pic that Pete

cheers

Matthew

[algol]

awesome, love the solar pics just looks destructive and violent.

[lunator]

Pete

Very nice image.

I hope that the brightspot turms into a Sunspot....

[Talitha]

Thanks Pete!

[Starflyer]

Cracking image Pete,

I'm loving the quality and quantity of amazing solar pics that get posted on here. The only downside is that I really want one of those Solarscopes, but have many many other things emptying my wallet for the foreseeable future

Thanks for sharing,

Ian

[Trevor]

Lovely shot Pete.

Could you please tell me how the double stack works.

[Starman]

Thanks for the comments.

Trevor: The double-stack works by emptying your wallet at twice the normal rate. It's effectively two etalons in series. Oh heck, now you're going to ask me more questions! Ok, here goes...

An air-spaced etalon like the kind used in the SF-70 uses two optically flat plates held in parallel to one another. So you have plate, air-gap, plate. The inner surfaces of this air sandwich are polished to a high optical flatness (1/100th of a wavelength in the case of the SF-70) and coated so that they are semi transparent. Light enters the filter through an energy rejection filter (ERF) which strips out the UV and IR components. What's left passes into the etalon where it bounces back and forth between the inner surfaces of the etalon plates. As these surfaces are so accurately figured, the wavelengths align and some destructively interfere while others constructively interfere. The latter reach a sufficient intensity to be able to escape their semi transparent cage. The former don't. The result is a series of wavelength peaks being passed by the etalon, one of which, if the filter is designed correctly is centered on the h-alpha wavelength. The quality of the etalon determines how narrow the peak is and the narrower the peak, the higher the contrast of the surface detail seen will be. Unfortunately a narrow peak also lowers the intensity of the peak so that it appears dimmer the narrower the peak becomes. You can imagine the output of the etalon as appearing as a number of wavelength spikes, something which gives it the title of a "comb" filter. Futher down the optical path (at the eyepiece end) is a blocking filter. This removes all of the unwanted peaks leaving just the h-alpha one to pass through.

In the case of the single stacked SF-70, the peak (FWHM) is 0.7 Angstroms wide. The use of a second etalon allows you to further reduce the width of this peak (in this case to 0.5 Angstroms) which means a higher contrast on surface detail. The downside of a double-stack system is that prominences often appear dimmer.

[Trevor]

Thank’s for the very detailed reply Pete, my wallet will be empty very soon :crybaby: might stretch to a PST though