About my solar images…

Over time I've acquired my solar images with a cannibalized inexpensive webcam (the guts of a Philips Vesta 675), cooled with two small CPU fans, and a video camera. The cameras are attached to an inexpensive 150 mm f/8.0 achromatic refractor (one of the recent Chinese imports). The CCD in the Vesta series of webcams is a 659×494 5.6 micron square-pixel Sony color CCD. The onboard electronics resamples to produce 640×480 8-bit RGB output. The video camera CCD has 768×494 pixels, 8.4×9.8 microns.

Most of the early imaging here was done both at prime focus and with a good-quality, 3-element barlow. (Some of the oldest images were obtained with eyepiece projection.) Just in front of the camera I have an 82 Angstrom FWHM filter centered on 5200 Angstroms. This completely removes the chromatic aberration from the inexpensive doublet objective lens. Most recently, I replaced the barlow with a Televue 4x Powermate stacked with a Televue 2x "Big Barlow". These are 2-inch diameter components, so I had to cobble together a 1.25-to-2 inch adapter so I could keep using the 1.25-inch Herschel wedge. Later I obtained a 2-inch Herschel wedge from APM Telescopes in Germany.

A brief description and photos of my solar imaging setup and other hardware can be found here.

Nyquist sampling for this telescope and CCD occurs around f/24 or so. Prime focus imaging is therefore undersampled and benefits from the stacking of several frames. Flat fields, suitably normalized, were divided into all frames (thus removing most of the dust speck shadows) before any kind of processing was done. Orientations indicated are approximate. The Earth images are to scale.

Recently, special attention was paid to scattered light. I coated the insides of the refractor tube and extension tubes with the coarse, non-skid material from 3M that is used on cement steps. (It has an excellent adhesive backing.) I painted everything with Krylon ultra-flat black, including the non-skid material. Until recently, I've been using a full-aperture filter made of the excellent Baader solar filter material (both visual and photographic densities). I now use a Herschel wedge, thus dispensing with the Baader filter. The images are noticeably sharper with the wedge, and much brighter, thus allowing larger magnifications. As you'll see below, I can now easily record granulation and penumbral structures, despite the shortcomings of the inexpensive, 8-bit webcam, and the not-so-inexpensive StellaCam II video camera.

New video camera and NB filter

New video camera acquired and used for images from here on up. I now have an Astrovid StellaCam II, which is essentially a Watec 120N video camera. The CCD has 768×494 pixels, 8.4×9.8 microns. I'm using a frame grabber from ImperX to transfer the images from the camera to a laptop hard drive. Pixels are squared off in software to 8.4×8.4 microns for the images shown here. I'm also now using a narrower, 30 Å FWHM, filter centered on 514.5 Å.

Televue Powermate and Big Barlow

New image scale available from here on. I now have a 2" Televue 4x Powermate in tandem with a Televue 2x "Big barlow" and a spacer. The resulting image scale (0.0665 arcsec/pixel) is well beyond what is reasonable for a 6-inch refractor, but having 15 or so pixels across a resolution element (~1 arcsec) allows aggressive removal of the webcam image resampling and compression artifacts. That I am able to get images at this scale at all is due to being fanatical about scattered light in the optical system. I'm now adding false color, which appears to enhance perceived contrast.

1.25-inch Herschel Wedge

I now have a 1.25-inch Herschel wedge from INTES (Ukraine).  From here on, solar images will be aquired with this instead of the Baader solar film filter.  The views are much better contrast with the wedge.