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Total New Moon and Planet Imaging with a DOB!

Posted by Jim Ruddy   04/21/2006 00:00:AM

Total New Moon and Planet  Imaging with a DOB!
After a ten year post-high school break, I've been back into astronomy for around 5 years now. I am also married, have a mortgage, a child, two cars, insurance, bills, bills and more bills.

As such, my astronomical equipment budget is practically negative. And yet I have the bug...

First - my equipment: 6" Synta Dob, Kodak CX6330 P&S digital camera and various eyepieces.
With these meagre supplies I have been able to image not only the moon, but also Saturn and Mars.

Imaging with a basic digital camera and a dob is a bit tricky. The biggest pitfall of a manual dob is that at medium to high magnification, your images will quickly drift out of your field of view. This is a critical problem for two reasons.
1 - You need to use a fast shutter speed to 'stop' the motion.
2 - You need to continually adjust the position of your scope if you want to stack multiple exposures.

Now, luckily, the moon and the planets are nice bright objects, so you can get away with a faster shutter speed without losing any light information.

Using a cheap digital camera also has it's challenges. The biggest challenge I face with my Kodak, is the complete un utter inability to control the shutter speed. Luckily I've determined that putting my camera into Sports mode and playing with the exposure ev adjustments, I've been able to come close to ideal shutter speeds for Saturn and Mars.

The last problem to overcome is keeping the camera absolutely still when taking the picture. My first experiments involved my film SLR, a tripod and the moon. The results were excellent. But when I jumped to my little digital camera, I had to abandon the tripod as there simply isn't enough room beside the dob to get the P&S into place.

So I turned on the LCD screen and held the camera to the eyepiece and took around 30-40 pictures, of which maybe 1 turned out.

Frustrated, I broke down and bought a good, solid digi-cam adapter, the kind that clamps on to the eyepiece. The results were still less than ideal, but I finally remembered my SLR days, and started to use the timer on the P&S. (You can not hold a camera still and depress the shutter.) This is why you should to use the timer to take the picture. The problem with this approach with a dob is that the image will drift on you. You need to develop the skill of knowing how much drift there will be and where to put the object in the field of view when starting the timer. You will need to experiment with your set up to get the best results for you.

So for the most basic start you need:
1 - a telescope on a solid mount
2 - a digital camera with a shutter speed setting or possibly a 'sports' mode
3 - a good, solid digi-cam adapter
There are some more expensive camera's from the better manufacturers (Nikon comes to mind) that have threaded lens housings. You can get connectors to attach these directly to your eyepiece. I have no experience with these, but I've read good things about this set up.

1 - Make sure you have a supply of good batteries or an A/C adapter for your camera.
2 - Visually locate the object and observe it to determine seeing conditions.
3 - Go to a medium magnification for a start. On my 1200mm dob, this is my 15mm WA lens.
4 - On this medium lens, mount your digital camera via the adapter. Be careful to get the camera lens nice and close to the eyepiece lens without touching it. Also make sure it is straight and lined up perfectly. Before you mount it, set your camera to a 'normal' zoom setting. On a film SLR this is around 50mm. Basically, it is close to what you would see with your two eyes, and you usually need to zoom in slightly on the cheap P&S digital cameras.
5 - Set your camera to Sport Mode (or Shutter priority) and TURN OFF THE FLASH!
6 - With another eyepiece, verify that the object is in the field of view and insert your camera. (If your lenses are parfocal it helps) Either manually focus the camera (if possible) or try to get the image in the auto-focus brackets.
7 - Take a shot. It will likely be blurry.
8 - Check it for brightness. Most digital camera's let you adjust your camera to slightly over or under expose.
9 - Estimate the path of the object across the field of view for the length of your camera's timer.
10 - Set the object in a position where it will drift into the centre of the view by the time the timer is done and start your timer (press the shutter on most cameras)

To magnify the image, I find it is easier to use a barlow than trying to use the zoom on my camera or switching eyepieces. I might try using the camera zoom function with a better (much better) digital camera.

That's it.
You will be frustrated and may give up, but if you master this skill with these clumsy tools, you will have something to impress your family and friends, if not, at least the guys at the local astronomy club will think you're insane for trying to image planets on a dob.

Once I have multiple good images from the same session, I use Registax (FREE) to stack them. It isn't totally intuitive, but it is free.

This is my experience with digi-scoping on the cheap. Go to it!

Jim Ruddy