Astromart

December 11, 2011 12:09 AM Forum: Astro-Physics

Cerro Tololo and Gemini South

Here is another view of Cerro Tololo from the valley below as we were driving in the mountains. One of the smaller domes to the right of the big one contains a 24" RCOS mounted on one of our 3600 mounts. It is being used for supernova searches in full robotic mode.

Rolando

December 12, 2011 08:24 PM Forum: Astro-Physics

Some images from the imaging conference in Chile

Posted By Roland Christen

This pix shows Daniel Verschatse, well known Chilean astrophotographer and owner of a number of observing sites in the Andes. Also Marj, and Alan Holmes of SBIG who also gave a talk at the conference.

Rolando

December 26, 2011 04:50 PM Forum: Astro-Physics

Aligning A-P Mach1 GTO

Posted By Roland Christen

Kelly McGrew said:

My work requires me to live about 7,500 miles from my A-P scope and mount, so I have only a brief time with them before I must return to the Sandbox. The first time I used them, in August, the alignment was spot-on.

This trip home, though, I can't seem to get the mount properly aligned. I follow the directions but, for example, after Polar aligning on Polaris (redundant, I know) and I direct the mount to slew to, say, Jupiter, the scope is pointed to the horizon in lieu of the zenith.

The date, time, and location all appear to be correct. Should I do a factory reset on the keypad? Is it possible to get the axis hubs out-of-alignment? I really want to get this working like it did the first time so I can enjoy these skies!

Thanks!

Kelly

Aligning the mount on the pole is only the first step in making a mount work. All that insures is that the polar axis is aligned, it does not insure that the scope is pointed in the proper direction with respect to the internal sky map.

The first thing you need to do after polar aligning the mount is to orient the scope to a known position. The easiest position to start with is the northern horizon. Loosen the clutches and place the scope horizontal, pointing north, with the counterweight shaft also horizontal. A simple carpenter's level can be used to accomplish this, or even eyeballing the scope and counterweight shaft is really good enough to start with.

With the keypad set to Autostart "NO", power the mount up, enter your location and then when it asks you for the start sequence, simply use the "Start from Park1" command. Now you can slew to any object, center that object in your eyepiece and press Recal. You are done, aligned and ready to tango.

Rolando

January 9, 2012 03:54 PM Forum: Refractors

Cassini in the EON 120

Posted By Roland Christen

e and f in the Trapezium are quite easy to see in a 4" refractor, and have been seen even in a good 80mm scope, so that is not a test of great optics.

Rolando

January 9, 2012 04:12 PM Forum: CCD Imaging and Processing/Deep Sky

First Light...

Posted By Roland Christen

This fall I got an Orion ED80T CF. I am going to really like the carbon fiber, since 40 degree swings are the norm rather than the exception here.

It is a fallacy to believe that carbon fiber will work to keep the focus constant in a refractor. The only way that carbon fiber can work is if the optics also are zero expansion, and that only occurs in reflectors that use Zerodur, Sital or fused quartz.

Unfortunately refractors use optical crown and ED glass, both of which have significant expansion co-efficients. In other words, a refractor's focal length shortens when the temperature drops. An aluminum tube also shortens, but at a lower rate, so there is some tracking of the focal point, but not perfect compensation. Using carbon fiber makes the problem worse. It may not show up much with a short focus 80mm, but it is definitely a problem in a 5"F6 size scope.

Rolando

January 11, 2012 12:22 AM Forum: Astro-Physics

Solar filter identification

Posted By Roland Christen

It is too bad that your pictures are so tiny. 19kb image is really not necessary - you can post as big as 450kb.

In any case, do not assume that because it is glass with nice shiny reflective coatings that it willproduce a high quality image. Most of not all of these inexpensive glass filters used cheap and cheerful window glass - have you ever looked thru your window with your scope? If so, you get the point.

Good glass filters are super expensive, because they basically have to be polished to the level of accuracy of a test plate. On both sides, no less! And the glass has to be first rate optical glass with no striations.

The nearest thing to that is a Baader Astro filter made from a very thin plastic foil material that has been carefully annealed and coated on both sides. Yes, believe it or not, it will outperform a typical inexpensive glass filter.

Rolando

January 11, 2012 03:46 AM Forum: Bad to the Bone Autos