January 20, 2018. I finished construction of my "ONAG" today. This stands for "On Axis Guider". It is a device that will allow me to take many hours worth of 10 minute or so autoguided exposures of star fields for the exoplanet transit program without differential tube flexure caused by a separate guide telescope. A photo of the finished job and a diagram of the optics and mechanics of my ONAG is shown below:
The ONAG is built around a dichroic beam splitter (perhaps I should call it "Trichroic") I bought from Surplus Shed a couple of years ago. Using dichroic filters on the 45° diagonal inner surfaces, the beam splitter divides incoming light into red, green and blue beams. I believe the original purpose of the device was to feed three image orthicon tubes with images from one camera lens in color TV studio cameras. I wish I had bought a couple of them. No longer in stock.
I also put a 0.63x focal reducer/coma corrector from Starizona on the front of it. The purpose of this is to correct the residual coma of the C14's SCT design, to make shorter exposures possible and to give me a wider field. I measured the focal ratio this device gave me by taking an image of the crescent moon. According to the Lunar Atlas program, the moon was 31.41 minutes of arc in diameter. In radians, this works out to be 0.009137 radians. I measured the diameter between the cusps and found it was 5699 pixels. Each pixel is 3.8 microns across, so my moon image was 21.6562 mm in diameter. Dividing this by 0.009137 we get a focal length of 2370 mm and the focal ratio is just this value divided by 355.6, the diameter of the C14's optics in mm.
A nicer, not over-exposed version of this crescent moon image is on my Lunar Imaging page.
April 11, 2017. Beautiful clear blue sky this morning. With Venus about 30 degrees west of the sun, it seemed like a safe time to look for Venus in the daytime. I had a reasonably good pointing model in the C11 and spotted Venus right away in the optical finder and centered it. A nudge using the video finder put it right in the field of the ASI174MM using a 3x Barlow. I took a 120 second video with an exposure of only 1 ms. That gave me 28,273 frames. I aligned and stacked the best 1% of them in Autostakkert 2 and sharpened the result in Registax6 for the image shown at the left.
December 25, 2016, 5:05 pm. Venus makes a wonderful Christmas Star this evening. Mars is also visible to the east along the ecliptic.
May, 1955. India ink on paper exercise, art class, Loveland High School
Dewing of the diagonal for the 16" Newtonian was a very serious problem. Note in the first three pictures on the left above that the back of the diagonal is exposed to the sky and can easily radiate its heat away to the sky. To solve the problem, I made a shroud for the back of the diagonal from a 4" diameter bean can with a plywood disk screwed to the bottom and three slits cut to go past the three vanes of the spider. Strips of double sided foam tape were applied to the can and then three pieces of cardboard were cut to fit the profile of the diagonal mirror and fit the cylindrical spaces between the spider vanes. The release paper was peeled off the double sided tape and then the cardboard pieces were stuck on and the whole thing covered in Duvetyne gaffer's tape to give a nice non-reflective black finish. All the diagonal mirror can now see is the ground which is a lot warmer than space. Hope it works.
December 7, 2015. I didn't take this picture, but I wish I had. It is an animated GIF of four frames taken by the New Horizons spacecraft of Kuiper Belt object
1994 JR1. It was taken by LORRI on November 2, 2015. It was 170,000,000 miles from New Horizons when the snapshots were taken, an hour apart. This image is a
300x250 pixel segment of the 1024x1024 pixel CCD. The full field is 0.29° across, so this picture is 5.1x4.2 arc minutes in size. LORRI is a 8.18" aperture corrected Ritchey-Chretien
telescope with a focal length of 103.5 inches, i.e., an f/12.6 optic.
November 6, 2015. Light shield added to secondary cage. Constructed from thin polyethylene foam insulation sheet. Painted inside with spray flat black
paint. Held in place with velcro tape and Duvetyne gaffer tape. Very lightweight structure.
November 4, 2015. New truss and secondary cage added to 16" Newtonian. The telescope is considerably lighter than the 12.5" Newtonian previously on this Losmandy G-11
June 22, 2015. This is sunspot group 2371, the cause of a geomagnetic storm and extensive Aurora Borealis displays as far south as Massachusetts. The spot group was
visible to the unaided eye (through a proper filter of course). Above image was taken with a 5" off axis filter on my CPC-1100EdgeHD using the ASI174MC camera. Seeing was quite
August 4, 2013. Below is an image of the Ring Nebula in Lyra, M57, taken with the Orion StarShoot Pro color camera at the f/10 focus of the C-1100. It is a stack of three 60 second images with dark subtraction, but no flats. Needs better guiding and a lot more exposure. The ring nebula is the remnant left from the final phase of the evolution of an average sort of star like our sun. After going through its red gian phase, the outer atmosphere of the star was blown out to form the nebula leaving a white dwarf star remnant of the core of the star. You can just see the white dwarf in the center of the ring.
July 30, 2013. I tried my pointing model for the C-1100 EdgeHD in the daytime and had no trouble finding both Jupiter and Mercury, but was unable to find Mars. I attached the ASI120MM camera, fitted with #25 red and NIR blocking filters, to the f/10 focus of the telescope and took a 60 second video. The combination of the short exposure and small ROI resulted in a very high film rate of about 300 fps. The 18000 frame video was processed in AS!2, keeping only the 20% best frames and drizzling 3x. The result of this was sharpened in Registax6 and levels adjusted in Photoshop to give the image at the left. I think I am resolving surface features on Mercury.
June 20, 2013. The three lunar images below were obtained from videos taken with the ASI120MC at the f/10 focus of my C-1100. Seeing was below average overhead but quite poor at the ~30° altitude of the moon at the time.
Here is a panorama of the near miss of an apple tree blown over during hurricane Sandy. The top twigs just brushed the roll-off roof track SE corner. Looks like my eastern horizon won't be in the shade of the old apple tree anymore.
May 28, 2012. I took a few moon videos tonight, although the altitude was a little low to get much resolution. Above is a view of the southern crater Moretus with its central mountain barely lit up on the peak with the crater Short behind it. Some nice terracing is visible in the walls.
November 27, 2011. The above image is a stack of 230 five second exposures of the region around the Orion Nebula, M42, taken with a 75mm f/1.3 Navitar lens set at f/2.4 on the DMK31. M42 is a region of active star formation in a spiral arm of the Milky Way galaxy. Dense clouds of gas and dust are illuminated by the light of bright young stars. Our solar system had its beginning in this kind of nebula some 4.6 billion years ago.
November 2, 2011. The above image of the Andromeda Galaxy and environs was taken with a DMK31 webcam and a 25 mm, f/1.2 lens. It covers an 8.2 by 10.9 degree area of the sky. It is a stack of 494 frames from 1300 seconds of video. Exposure is probably about 2.5 seconds per frame. The video was processed with a dark frame using Registax 6, saved as a 16 bit TIFF and a final levels adjustment done in Photoshop. The faintest stars identified in the image are 12.3 magnitude, however there are fainter stars which do not show up in planetarium programs. All of the stars you see in this image are actually foreground objects in the Milky Way galaxy where we live. The dwarf elliptical galaxy NGC 205 is also visible above and to the right of the nucleus of M31. When the light which formed the image of M31 started its journey 2.6 million years ago, genus Homo was just a gleam in the eye of a lovely Australopithicine Eve.