Astrophotography?

I'd like to get into a bit of Astrophotography. So far, I've been able to hold up a digital Camera to the lense and take pictures of basic things like the moon, but the pictures are rarely clear, and often have the edge of the eyepiece on them.
What sort of equipment would I need to get onto the more 'serious' level of astrophotography?

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This entry was posted on Tuesday, July 6th, 2010 at 11:06 pm and is filed under Information. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

2 Responses to “Astrophotography?”

Sean Esopenko Says:
July 6th, 2010 at 10:24 am
I just dabble and use a DIY scotch mount and 35mm lens on an SLR camera. It sounds like serious astrophotography is quite pricey…
Jeff Says:
July 14th, 2010 at 11:07 pm
expect to begin spending a lot of money…

For simple astrophotography, you can buy an adaptor for most digital cameras that hold it correctly over the eyepiece for a good image. I think some cameras can take pictures without the eyepiece in place (I forget–you might need a macro setting or something?), but if you’re taking a picture through the eyepiece, then get a high-quality eyepiece. This setup will get you pictures of bright things like the moon and maybe larger planets, and they’ll be less fuzzy because the adaptor will hold it in place better than your hand. The smallest bump makes a huge jiggle on the magnified image, so you should set your camera on time-delay exposure so that you can take the picture "hands off" and you’ll eliminate jiggles. My mom got one of these adapters for her C90 maksutov spotting scope and she has some great pictures of the moon.

For clearer pictures, you need to eliminate all those lenses between your telescope objective and the imaging surface. An eyepiece and camera lens is a lot of glass for light to pass through and get distorted. Digital astrophotography usually utilizes CCD imagers, which is just a bare digital camera chip on an adapter that screws on the back of your tele. The first thing you will probably notice when you get into higher resolution work or longer exposures is that your telescope mount is way shakier than you thought. You will end up wanting a very beefy equatorial mount with a tracking motor for your telescope. And if you’re spending that much money, you might as well upgrade your telescope as well. If you want to take pictures of nebula, galaxies, star clusters, etc, you will need to take long exposures –up to 30 minutes or more for really good pictures. Your tracking needs to be dead on and a bad telescope and mount will just frustrate you to no end. There are some technical solutions to bad tracking by stacking multiple images and taking out bad frames and correcting for field rotation and drift, but it’s a lot of work. If you’re just interested in planetary or moon work, the exposure times can be much less, requiring less patience and exactness in tracking, but you will need very good optics and atmosphere for good pictures. There is also a lot of imaging processing software out there to help stack and sharpen the good parts of the image. With the right software + hardware, amateurs have been getting incredible pictures of planets lately!

Oh yeah, if you’ll be doing long exposure photography, you’ll not only need a good equatorial drive, but also electronic controls for both axes and ultimately a CCD style auto tracker. Even a clock drive does not track perfectly and you have to make multiple corrections per minute which gets very tiring after a short time if you’re doing it manually.

Also, the high-resolution CCD imagers are actually just black-and-white chips. You need to get RGB filters–usually in an automated filter changer to get a color image. The "easy" color CCD chips like in digital cameras actually have 4 true pixels for every one final pixel, the pixels are usually RGGB arranged in a square of 4 pixels or something. The plus is that they require no filters, but the minus is that they have 1/4th the resolution of an equivalent black&white chip. A color chip is the equivalent of hooking up a normal digital camera to the back of the scope, minus the lenses. Standard digital cameras cannot take long exposures (more than 15 seconds or so) due to dark noise caused by heat. The more expensive CCD imagers are electronically cooled to decrease the dark noise and increase the exposure time.

All depends on how much time and money you want to devote. I’d start with an adapter on your existing system and maybe a better eyepiece, and move up if you feel like you’re dedicated and your wallet is too heavy.