SolarChat!

In This is Solarchat I posted a mosaic of these three wavelengths: viewtopic.php?t=40803. I will post the individual images here. 106mm aperture, 720mm focal length telescope. The Ca-H image was done with a 72mm aperture mask (and probably the H-beta might have benefited from a 90mm mask). ZWO 183MM camera under FireCapture, AS!3, ImPPG, Photoshop Elements. All scans were done in the DEC direction with an ROI length of 3304 pixels; width 120 pixels for Ca-H, 100 pixels for H-alpha, 70 pixels for H-beta -- the width of the ROI depended on the width of the spectral line. The narrower the ROI, the higher the fps the camera can output and therefore the higher the scan rate and shorter the acquisition time.


H-alpha, stack of 16 scans. Exposure 2ms, gain zero, 386fps.


H-beta, stack of 12 scans. Exposure 0.8ms, gain zero, 479fps.


Ca-H, stack of 9 scans. Exposure 3ms, gain 13%, 318fps.


Ca-H SHG data reprocessed to bring out the Calcium prominences. There is good correspondence with the H-alpha prominences (see inverted H-alpha image below)

Hi Doug,

Astonishing SHG images. They look like if they were made with etalons of normal filters but not with a Spectroheliograph.

Very well done. I have been clouded out since several days but had time to finally finish the braking system of my Land Rover and it is working as it should work.

Those are terrific - very impressive!

Kevin

Oh my!!! these are delicious, I can't work out whether Hbeta or CaH is my favourite what a box of chocolates!

Alexandra

These are outstanding. There is a "feel" about the Ha which is very different - more organic - than classic Ha etalon photos. Is that b/c of the SHG? And the CaH w the prominences is a feast for the eyes.

I'm sorry I missed the zoom on SHG you gave as we had guests - did that end up being recorded?

vineyard wrote: ↑Thu May 25, 2023 9:42 am There is a "feel" about the Ha which is very different - more organic - than classic Ha etalon photos. Is that b/c of the SHG?

I'm sorry I missed the zoom on SHG you gave as we had guests - did that end up being recorded?

Yes, there was a recording made. You can find it here: viewtopic.php?t=40847

There is a different feel to the SHG images. I think it's because they are typically full disks with both high spatial resolution (if the aperture is large enough) and with very high contrast, which I think increases the sense of depth and texture. I think you could get the same effect in H-alpha if you had a double-stacked 100mm etalon system -- that would give almost as high spectral resolution (i.e. contrast) and equivalent spatial resolution. But double-stacked 100mm is so expensive that you don't see images like that very often.

You can get even better spatial resolution and similar spectral resolution on a narrow field of view (i.e. with a quark + etalon) but that does lose the impact of the full disk. And for Calcium images, typical images are not really very narrowband since they are filters rather than etalons. I have once seen an H-beta etalon but they seem very rare (I think also hard to make since the H-beta line is much narrower than H-alpha).

Superb set of spectroheliograms Douglas and congratulations on SPoD,well deserved

Alun