I set up my Mintron camera with the 50mm F1.4 Lens I picked up and played around to see what sort of results I could get.

I have to say I’m very impressed, even over the light polluted skies of Auckland City (I’m very central city at the moment), I was able to get the following images (Annotated using astrometry.net).

Orion's Sword

Orion's Belt

Some of those really faint specks are stars of around Magnitude 9. These images were direct from the Mintron camera, so no processing has been done on the light levels.

I’ve been busy the last two weeks converting code and waiting for deliveries to arrive.

I finally received the 50mm F1.4 lens I ordered off ebay. This lens is a lovely unit, especially for US$50. It’s nice and heavy with manual aperture and focus controls. A quick test on the light polluted skies of Auckland resulted in me being able to image stars of Magnitude 4, so it’s well within the limit for the project.

The 50mm F1.4 Lens attached to the CCD Camera

I’ve also been very busy converting the C++ code by David.A.Vallado implementing the SGP4 and SDP4 formulae into Delphi/PAS files. So fair it’s looking promising, but I’m still to run the tests and confirm compliance with the C++ base code.

I’m also trying to optimize this code to run on an AVR micro controller. The code uses a lot of floating point maths and even at 20MHz it takes a good second to output a result.

I’m still not sure on exactly how my PC software will communicate with the device. It’ll either come down to a micro controller being sent the Two Line Element data and doing the SGP4/SDP4 calculation, or the PC software. If it’s the latter, there are plenty of issues to work through with regard to delays in the RS232 protocol and the best method to send real time linear commands to the micro controller.

Hopefully I’ll have more information and answers in the coming week.

I don’t have much new to report on the Satellite tracking platform.

I’ve been looking into equipment for the system and at communications protocols.

My initial plan was to use Linux as my operating system to run the tracker, but I like the idea of ASCOM which provides a software driver interface so that end users do not need to worry about the hardware implementation. Unfortunately, for a system which is heralded to be “Open” wherever possible, it is only a standard for Windows. The end result will probably be that I write an ASCOM driver to run the unit on windows but retain the ability to talk direct to an RS232 serial port for other systems where required.

I’ve also got my hands on a MAX7456 Breakout Board. This is an on screen display chip which should let me overlay accurate GPS time on top of a PAL or NTSC video signal. The chip is extra handy as it has Horizontal and Vertical Sync outputs so I don’t even need to built a circuit to get the Sync pulses.

I’ll keep you all updated….

The main circuit board worked and using serial could be commanded to go to a position or even store positions, but it lost out due to not supporting the speeds I wanted to control. I specifically wanted to be able to go from 1 revolution per day (About 0.0007 RPM), up to about 15 RPM.

Even if the board couldn’t be used whole, it still contained bipolar stepper motor drivers. It used matched pairs of L297′s and L298′s. I quickly decided against using these due to the simplicity and size of the EasyDriver.

Out came the 48VAC to 24VAC toroidal transformer and I was left with this:

If space permits, the camera can be mounted on this plate upside down, and it will Pan and Tilt around it's nodal point.

The Pan and Tilt axis both have magnetic sensors for “home” positions. I’ll probably add limit switches to the Pan axis, mainly for when it powers up to calibrate itself. If I didn’t, the only way to calibrate the Pan axis with a “middle of travel” sensor is by traveling full travel in one direction (hitting the physical stop and stalling the motor) each time, which just seems plain wrong.

Of special importance was that the unit used Stepper Motors to drive the two axis’ and it uses a 12 way slip ring for electrical connectivity. These stepper motors are each 200 pulses per revolution and are geared 10:1 to the axis, this gives a total of 2000 pulses per revolution, which is 0.18 degrees, or 10.8 arc minutes. I’m hoping to be able to drive the stepper motors at 1/4 stepping, which will give me 2.7 arc minutes of position resolution. The slip ring means that the Pan axis can turn continuously and the wires will never get “tangled”.

The unit is also designed in such a way that a small camera and lens assembly can be fitted so that it pans and tilts around the “nodal point” of the lens. This means I could potentially build myself a high resolution, heavy duty Gigapan.

I’m not 100% sure of the final details yet, but I hope to be able to drive the pan tilt (and possibly lens zoom and focus) by a computer. I have another project planned which uses an AVR to overlay a very accurate time stamp (and possibly RA/Dec) onto a composite video signal.

I hope to have the whole unit up and operational by March/April 2011 in time for the next launch of a Boeing X-37.

Expectations are high, with a peak ZHR (Zenithal Hourly Rate) of up to 120. The moon will set in the west around midnight giving nice dark views of the Northern sky.

The Geminids radiate from their namesake, the constellation of Gemini.

The Constellation of Gemini (''Borrowed'' from www.heavens-above.com)

Unfortunately for me, Gemini is very low in the sky when viewing from New Zealand.

For the next week, Gemini will
0000 – Rise from the North East
0330 – Max altitude to the North of about 30 degrees
0700 – Set in the North West

I might even try and get my Mintron low lux camera out and record my first Geminid on video – Watch this spot

On top of this, the earth is at perihelion at the moment (the point where earth is closest to the sun), so the moon will also be extra bright.

Calculations show that the moon should be 33 arcminutes and 30 arc seconds (just over half a degree) in size.

While you’re at it, put a reminder in your calendar to photograph the moon on the 24th August – this is a full moon at apogee (the point where the moon is farthest from earth), where it will appear to be only 29 arcminutes and 24 arcseconds in size.

When you take your photos, I suggest noting down the zoom, iso, shutter speed and aperture so you can compare both the size and relative brightness with August.

Here is a link to a previous post about this.

Source: Wikipedia

The Geminids are a meteor shower caused by 3200 Phaethon which should result in around 120 to 140 meteors per hour. On top of this, the best dates to view it are two days before a new moon so the sky should be nice and dark.

The meteors should radiate from the constellation Gemini, which is right next to Betelgeuse in the Orion constellation.

For more information on the Geminids, try the spacedex website.