Posts Made By: Roland Christen

It's time to bring the Mustango out again and drop that top.

The little pony spent some time in the spa this winter getting a little engine upgrade

Rolando

Hi all,

Gilles Cohen posted this short video showing the 1200 mount with C14 and 140EDF mounted side by side and slewing. That's Franck from Ovision at the controls:

http://www.youtube.com/watch?v=tBbmOZE2lis

Cool cool cool!

Rolando

Hi all,

Getting ready for NEAF, I pulled out my 130EDF refractor and had a look at the lens (Serial #01). I lent this scope to my friend Mark last summer, who took it to a number of star parties (Chiefland in Florida, Black Forest, Nebraska, etc). He told me that dew was heavy at all these events, and he did not have any kind of dew heater to prevent the inevitable moisture from settling on the optics. I didn't want to bring this lens to NEAF in the condition that it was in, so cleaning was in order. I am taking this opportunity to show you all how it is done.

First pix shows the lens in cell with retaining ring removed, the way it was returned to me last year (I have not had time to clean it since). Looks pretty bad, yes? In fact, the contrast was noticeably poorer than it should be for this optic. Lots of stray light surrounding a bright target image.

Rolando

From our friends Gilles and Franck of Ovision:

http://www.ovision.com/NEAF2009.html

Rolando

Cropped image of M101 galaxy.
Image shot by Tony Hallas using AP 206EDF refractor and Apogee 16803 camera.

Rolando

Image by Tony Hallas taken with 206EDF and new QSI 8300 camera. 12 x 20 minute exposure. Note the cool tidal effects around some of the galaxy clusters. Taken on a night of very poor seeing.

Rolando

Last night it was finally clear, and the 305F3.8 Honders Astrograph saw first light. Although the seeing wasn't the best, it was transparent enough to capture some faint detail using narrow band H-a and OIII filters. The image is reduced to 1/4 size to show the immense field of this astrograph using the STL11K (cropped full size at top right)

305mmF3.8 Honders Astrograph, 3600 Mount, MaximDL,
Camera STL11K, Baader H-a and OII combined as RGB, exposure: 9x10 minutes H-a and OIII

Rolando

This is probably the first image ever taken with a Honders-type Cassegrain astrograph.

305mmF3.8 Riccardi-Honders Astrograph, 3600 Mount, MaximDL,
Camera STL11K, Baader H-a and OII combined as RGB, exposure: 9x10 minutes H-a and OIII
Image has been reduced to 1/4 size with full size crop at top right.

For those unfamiliar with Honders, it is a design derived from the Schupmann Medial telescope, invented more than a century ago. Klaas Honders modified the original design into a Newtonian configuration, and from there Massimo Riccardi developed it further into a Cass configuration. My design is a 305mm F3.8 Cassegrain based on the Riccardi-Honders configuration. The basic optical layout is a front positive lens followed by a smaller primary Mangin mirror, a secondary mirror (same as a normal Cass secondary) and finally a small single element field lens about 4" in front of the focal plane.

This astrograph features a very wide,flat, fully diffraction limited field of about 60mm diameter, with essentially zero chromatic aberration and perfect spherical correction for all colors. All surfaces are spherical, and the primary mirror has a second surface aluminized coating, something that will last essentially forever and will never sleek or weather because it is an inside coating not exposed to the air.

Rolando

Here is a quickie M27 LRGB taken with 206EDF refractor and STL11K camera. Testing the field flattener for this scope. Image reduced 50%

Tony Hallas image, 8300 chip, 206EDF refractor, 1200 mount, 1/2 size.
Final image. (this would be cool if he did a mosaic of the entire area around this cluster of galaxies).