Sundays Ha Sun

[marktownley]

Poor weather all weekend finally broke at about 5pm sunday evening leaving clear skies. I had the scope setup ready to go... A slight banding present on this one as a result of knocking the etalon whilst taking the dark frame - moral of the story, flat first then dark... Taken with the usual setup, DS40 @ f20, DMK31 6 panes assembled in CS4.


Ha Full Disk B&W by Mark Townley, on Flickr

Full Size Here!



Ha Full Disk colour by Mark Townley, on Flickr

Full Size Here!

I'm hoping the weather will be kind and will let me get some more solar in through the week...

Hope you like!

Mark

[Derek Klepp]

Nice Mark no sun here today

[Cschur]

Gorgeous Mark! Why do you need a dark frame with gobs of light?

[swisswalter]

Hi Mark

very fine full disk and work out of the color version

[marktownley]

Thanks everyone!

Chris, I take a dark as all my shots are 'one shots' so, while there is loads of light on the disk, in the prom regions and surrounding disk there is not; when I am teasing every last photon of prom energy out in my pics, I find it is this area that benefits from having a dark applied, allowing me to push the procssing that little bit more...

Mark

[smerral]

Super stuff Mark.

[mattwastell]

That is a great pic - it draws you in to look at the detail - love it!

[Montana]

Beautiful Mark, not your usual with all the lines but still a super full disc

I still don't understand flats and darks, it worked only once for me in one picture, the rest I get strange patches of light and dark everywhere and it makes the picture worse so I gave up. You must have a good technique.

Regards
Alexandra

[edobosz]

Good stuff Mark. Still trying to figure out the banding. Is this some sort of standing wave cause by the vibrations in the etalon?
Ted

[smerral]

Is not the banding a variation on Newton's rings, a diffraction pattern? I must be extremely lucky as I never seem to be bothered with them at all with my combo.

[marktownley]

A bit of an explanation to the banding...

Any tilt tune external etalon is going to have some banding to a lesser or greater extent, the exact pattern / angle of this is dependent on the exact position (tuning) the etalon is set at. Normally, I take the 6 panes that make up the full disk mosaic then set the fov dead centre on the suns disk, defocus and take a flat. This captures any dust bunnies and any banding that may or may not be present. Then, I put my cap or a beanie hat on the objective end of the scope and expose an avi for a dark frame. For whatever reason yesterday (probably bcause I wasn't conncentrating!) I took the dark frame before the flat - the effect of me putting my hat on the end (etalon) on the scope was to slightly alter its position relative to the original position when the image panes were exposed. Now, when my flat with its subtley different banding pattern was applied to the image frames with their subtley different banding pattern a constructive / destructive interference pattern is set up which gives the banding seen in the final image. It's a curious thing: when flat frames go wrong this is the result, if you look at the individual raw image panes, or even the flat frame, the banding is barely noticeable, if you weren't looking for it you wouldn't probably see it - however, like I say, the wrong result is obvious!

[Montana]

How much do you defocus? a little or a lot? Also when you do the edges (limb) how come the photo doesn't go white where the dark is if you haven't got a matching dark patch on the flat?

Regards
Alexandra

[xn44]

Good images, Mark!

[marktownley]

How much do you defocus? a little or a lot? Also when you do the edges (limb) how come the photo doesn't go white where the dark is if you haven't got a matching dark patch on the flat?

Defocus quite a bit. Important thing is that you're dead centre on the solar disk, else you get a gradient across the image; Also very importtant not to touch the etalon, rotate the diagonal / cam etc. Not sure why the edges don't go white

[Montana]

Mine do!!

Alexandra