Friday, June 20, 2008

Total Solar Eclipse Setup

First of all, it's the polar alignment. The Takahashi TG-SP II does not come with a mechanism for polar alignment. I've a V-adapter specially made for Hong Kong, but for overseas trips, I need to use the Manfrotto 410 head to provide the fine adjustment. I've asked a local friend to make an adapter plate so that I can mount a polar scope there for polar alignment. For a small mount like this one, I believe that a polar scope is usually fine enough without the need for drift alignment.

This is the computer. A computer is nearly a must in today's astrophotography setup. You will need a computer to control the exposure of the camera, to will want a computer to help the focusing. Of course, all these could be replaced by dedicated hardware, but a computer is definitely helpful.

This is a Sony Vaio U3, and it's pretty slow in today's standard. It features a Crusode 933MHz CPU with 512M memory. It's small and portable as you can see with this side by side photograph with a JMI hand controller for motorized focusing.

I'll use it to control the exposure of my Canon 450D, it now supports direct control of exposure including BULB exposure without the need of any special cable. I'll also use it to control my DMK31AF03.AS for solar imaging. Notice that this slow notebook can only support up to around 10fps only, but then portability rules for overseas trip. Finally, I will also use the DMK for deep sky imaging as well, together with a couple of fast C-mount prime lenses.

This is the setup. In this photograph, I'm trying to show the location of the counter weight. This is a very small counter weight, but then as you can see, it's enough to balance a camera with a lens, as well as a small telescope with H-alpha solar filter! The TG-SP II is so compact and well designed that it's not just small by itself, but it also requires less counter weight. The reduction of counter weight is done by using the motor as part of the counter weight, and the scope mounting is very close to the RA axis. Counter weight is a big part in an equatorial mount, it usually takes up 3-4kg of your total setup weight, but for this small mount, it is less than 1kg and it's enough for most cases.

Let's talk about the imaging setup. For white light, I will use a Canon 200mm f2.8L with a Kenko 2x Teleplus, of course, I will also need a white light solar filter which I will show in the later photographs. 400mm focal length together with a Canon 450D will give a solar disc bigger than 700x700 pixels in size. And with the outer corona, the field size will be big enough to cover everything. And it's still manageable by the small TG-SP II.

For H-alpha, I will use a Borg 45ED II. The Borg is equipped with a JMI NGF-S to provide fine focusing. Camera will be a monochromatic DMK 31AF03, again the solar disc size will be slightly smaller than 700x700. I hope to be able to capture some special moments before the totality, and even the partial eclipse with it. The solar filter is my Coronado Solarmax 40 with BF10.

I have used a third party ring for my Canon 200mm f2.8L, without using it, the balance point would be different for different side of the meridian. This small ring fixed this problem, and it also allows changing the orientation of the camera. Notice that this shot is taken with the Hong Kong V-adapter rather than the Manfrotto 410 head.

This show shows the cameras end. The Canon 450D is connected to the computer via USB 2.0 interface, and the DMK 31AF03.AS is connected via Firewire.

This is to show the relative location of the dovetail to the mount. You can see that the Canon side is heavier than the DMK side.

The whole thing showing the computer as well. I hope that I will have a table in the observation location, but I know it's not going to be real.

The front end again, showing the thirty party ring for the Canon lens, and the Borg is connected to the dovetail directly, I used this mounting hole instead of the one on my focuser because it allows better overall balance.

Finally, the white light filter is attached for another shot. The filter is a Thousands Oaks Glass Type 2+, this is originally acquired for my Ranger many years ago, now it's useful again.

This setup will also be used at night for wide field imaging. We will have two nights there in the observation site and I hope to be able to do something there as well.

For the Canon side, the Kenko 2x will be removed for deep sky imaging requires more tracking accuracy that I would prefer to do it at 200mm at f/2.8 rather than 400mm at f/5.6, since both 400mm and the slower photographic speed demand more accuracy than my TG-SP II can provide.

For the Borg side, the solar filter is removed, and a 9mm adjustable illuminated reticle from Meade will be used for manual guiding in case required. This can also be used for drift alignment.

Finally, here is another version from facebook:-

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