by Tom Campbell
| Observer | Tom Campbell |
|---|---|
| Location | Iola, Kansas (Long: 95°30'W Lat: 37°55'N) |
| Equipment | 8" Discovery DHQ dob |
| Eyepieces | 1.25" Plössl - 25mm (49x) |
| Filters | Baader AstroSolar full-aperture |
| Time | 3:00pm - 3:15pm CST |
| Transparency | Clear (8/10) |
| Seeing | Fair (6/10) - due to lack of thermal equilibrium |
| Weather | Temperatures in the upper 40s. There was little or no wind. |
Recently, I found a good deal on a partial sheet of Baader AstroSolar film. It was a large enough piece to make a full-aperture filter for my 8" and have enough left over for my 60mm refractor. When the film arrived, I followed the enclosed instructions for making my own filter cell.
I made the cell out of black posterboard and black foam. I cut two rings out of the foam board, with the inner diameter matching that of my primary mirror and the outer diameter matching my telescope's tube. The posterboard was cut into long 2" strips and glued together and wrapped around the telescope tube to make a snug fit for the cell. I then glued several posterboard "flaps" to the cylinder section of the cell, folded them over, and glued the folded portions to one of the rings.
Next, I applied several pieces of double-sided tape to the top of the the ring section. After carefully placing the Baader film on top of the first ring, I then applied more double-sided tape to the second ring section and laid it down on top of the film. My solar filter was complete!
With one of the inner circles from the ring cutouts, I cut an off-axis circle that would fit between my secondary spider vanes. I then glued spare pieces of foamboard to each of thse circles (to use as handles) and glued a layer of tissue paper to the underside of the circles (to help protect the fragile film). Now my solar filter has a dust cover with a smaller circle that can be removed for off-axis viewing. I'll post pictures here as soon as I can.
For the last week or so, the skies have been overcast. To top it off, our part of the country was caught in the throes of a terrible ice storm. That'll teach me to order a solar filter in winter, I suppose.
Since it arrived, I've been anxious to have some clear daylight skies to try it out. Friday was clear, but the Sun was setting by the time I arrived home from work.
Finally, today turned out to be gorgeous. I didn't have a lot of free time, but I was determined to take advantage of the opportunity. I ended up with about 15 minutes of spare time before I had to take off for another appointment, so I quickly carried my astrogear outside and set up.
| Sun | Star | 3:00pm CST | |
|---|---|---|---|
| I didn't have nearly as much trouble aiming my telescope at the Sun as I
thought I would. After putting the solar filter in place over the front of
the telescope, I swung it around until the tube was making a circular shadow
on the ground. To fine tune my adjustment, I held my open hand a few inches
away from my 6x30 finderscope until the projection of the Sun through the
finder was centered within the finder's shadow. I looked through the
eyepiece, and there it was.
I didn't have time to allow my telescope to cool down to ambient temperature, so I did my best to ignore the waves of air currents along the edges of the image. The view was an eye-pleasing grayscale. I had made an off-axis filter cell overlay in case I felt the image was too intense, but I thought the full-aperture image was fine, so didn't try it. Several sunspot groups were visible. The largest and most interesting was group 9802. It resembled a volcanic chain of Pacific islands. The umbral "islands" were surrounded by a penumbra resembling a barrier reef. The photos on my website ( http://www.iolaks.com/softech/astro/20020203.htm ) don't capture all the detail that was visible, but help to show the general appearance. I was able to see all of the major sunspot groups labelled by the SOHO image (also shown at http://www.iolaks.com/softech/astro/20020203.htm ), as well as some of the bright regions along the outer limb of the Sun. I was quite pleased with the performance of my homemade solar filter. The Baader material offers a nice contrast and the 8" of aperture will allow me to really crank up the magnification whenever I get the chance. Because of my limited time, I knew I wouldn't be able to properly record all of my observations. So I grabbed my digital camera and snapped a few quick photos. | |||