Sunday, July 20, 2014

Camera tracking tests

On July 19th I set up the new equatorial mount right ascension axis for the first time. The goal was to test the tracking with a camera and 100mm lens. The photo's were taken in our backyard which is a 5minute drive from downtown tucson. As you would expect, the light pollution washes out the milky way, but fortunately I was able to prove the new mount is working extremely well. Polar alignment was roughly accomplished with a polar scope.

At first I was getting some very strange results. It turned out I didn't have the camera locked down on the swivel mount, whoops!

2 minute exposure, M8 the Lagoon nebula and M20 the Trifid Nebula are in the upper right. You can also see a Globular cluster in the far left of the field. Unfortunately this camera lens suffers from a great deal of Coma, which you can see in the comet shaped stars at the edges of the field.

Another photo of M8 and M20 more centered, this frame has been cropped.

5 Minute exposure of M17 the swan nebula and M16 the Eagle Nebula. You can see how washed out the image is due to the light pollution of downtown tucson. Note the pin point stars at the center of the frame, demonstrating the tracking is working great.

This is why you need a tracking mount. This is a 5minute exposure of Antares with the tracking turned off. Compare to the above images where there is no trailing in the images, even with a very rough polar alignment.

Tripod Base for the Fork Equatorial Mount

Welding the base:

I welded the base out of 2x4" steel tube, 14gage.
The leveling feet were purchased from mcmaster and have a 3/4" 16tpi thread 3" swivel pad
The machined aluminum plate is milled from a 3/4" plate. The central region that the equatorial head pivots on for latitude adjustment is 8" in diameter. 

This picture shows the equatorial head mounted to the tripod. The fork arm will place the CG of the system over the middle of the tripod footprint, maximizing the stability of the mount and scope.

The mount will be anodized and the tripod will be painted once the system is fully tested and I am happy with the performance.

Machining the 6"x6", 1/2" wall, box beam tube for the fork arm. There was a fair amount of bow in the extrusion that needed to be removed via machining.

Thursday, July 10, 2014

Equatorial Mount Fabrication Pictures

Single Arm Fork Equatorial Mount

I started the design and fabrication of a large equatorial mount for my 12" F/4 imaging newtonian.
Some of the basics on the mount are as follows:

-Single Arm Fork Equatorial
-Fixed Latitude, designed for Tucson
-Large 4.75" R.A shaft
-11" Stainless steel friction drive with a 1" Alumina Bronze roller and 2 stage timing belt reduction
-Siderial Technology Servo II system with pittman motors
-Polar scope for R.A axis
-Quick disconnect between R.A and DEC
-R.A weights approximately 65lbs, the Declination will be approximately 60lbs
-4" Shaft on DEC 
-7.5" worm gear for DEC drive with spring loaded linear rail system for backlash removal
-Steel tripod, approximately 45lbs

If you have any further questions on the design I would be happy to answer them for you. I will be adding pictures as the mount takes shape and undergoes testing.