Unanswered questions for astrophotography

[Hatan]

Hello,

I've been reading a lot about type of astrophotography and accessories, but I have some unanswered questions. So if you can give me some advises I would greatly appreciate it.

So far, my astrophotography has been based on Afocal and I might consider moving to something more advanced - prime focal (wich also mean new telescope, mount, guiding and of course new camera).

So my first easy question is, what is the difference between a CCD and DSRL cameras. Some people seem to consider them the same thing, other consider them as 2 different categories.

Second question a bit harder. A lot of people are talking about video cam(Phillips toucam or the StarShoot Solar System Color Imager II etc) and they say they take GREAT planet pictures, but how can these be better than a 10 megapixel Camera (considering both of them supporting prime focal)? The webcams are around 150-200$ and you can now have a 8-10 mega pixels for 250-400$. The webcams are around 0.3 - 1.2 mega pixels which basically mean the 10 mega pixels have rougly 3-5 zoom bonus right there (because of the precision).

Third question, How can a webcam: this one in particular: "DSI PRO II w/CCD color filters" be SO expensive (700$) and only supportig a max resolution of 752 x 582. What is so great about it compared to the other 150-200$ webcams?

And fourth questions, this same webcam is called "DSI" for DEEP SKY Imaging". I thought that webcams were only good for planets and you absolutly needed a CCD for deep sky imaging? How can this webcam succeed in taking deep sky objects?

So that's it, thanks in advance :)

[Siguy]

1.) A CCD camera is something that's MEANT for deep sky imaging, it connects your telescope and computer so that they work together. A Digital SLR camera is high resolution and works without graininess but it works on it's own. If you want to see what a standard Canon EOS 350D can do for astrophotography, go here. This guy is amazing. http://octane2.deviantart.com/

2.) Telescope webcams are crap. They are only for you if you just want to go cheap and only get pictures of the Moon. They give very blurry images of planets. You need a high quality imager like a Meade DSI if you want to go that way.

3.) It isn't like other webcams. It is meant for deep sky CCD imaging. It isn't about resolution.

4.) DSI is a CCD camera. It isn't really a webcam.

[Siguy]

I also want to add that with the Meade DSI, you can get more for your money if you buy it coupled with a good Meade telescope for $130 (B&W) or $228 (Colour). Much more professional deep sky CCD imagers that cost much more are worth the cost, but low resolution ones like the DSI aren't worth it as much if you buy them alone.

Just don't forget to buy a telescope on a sturdy equatorial mount. ;)

[Kaptain K]

The secret of webcams is that you don't take just one image, but tens, hundreds, or even thousands of very short images and combine the best of them with a program like Registax (freeware). By combining only the best images, image quality and resolution can approach the theoretical limits of your optics. Amateurs with modest scopes (8-12 inches) and webcams are getting better images than the pros with unlimited equipment were able to do a generation ago!

[ozark1]

Hello,
So my first easy question is, what is the difference between a CCD and DSRL cameras. Some people seem to consider them the same thing, other consider them as 2 different categories.

The primary difference is that the astro CCD has very low noise compared to the DSLR. The astro CCD is also more sensitive to light/ has bigger pixels.

Second question a bit harder. A lot of people are talking about video cam(Phillips toucam or the StarShoot Solar System Color Imager II etc) and they say they take GREAT planet pictures, but how can these be better than a 10 megapixel Camera (considering both of them supporting prime focal)? The webcams are around 150-200$ and you can now have a 8-10 mega pixels for 250-400$. The webcams are around 0.3 - 1.2 mega pixels which basically mean the 10 mega pixels have rougly 3-5 zoom bonus right there (because of the precision).

As has already been said, 1 long exposure is easily beaten by a stack of the best of 10000 pictures. It is to do with the (lack of) atmospheric stability.

Third question, How can a webcam: this one in particular: "DSI PRO II w/CCD color filters" be SO expensive (700$) and only supportig a max resolution of 752 x 582. What is so great about it compared to the other 150-200$ webcams?

The DSI PRO II is extremely sensitive to light. Part of the reason is big sensors. On a small chip = lack of resolution. However it gets 6 magnitudes below naked eye on a 10 sec image! One other good astro feature - it's black and white - try selling a black and white dslr.

And fourth questions, this same webcam is called "DSI" for DEEP SKY Imaging". I thought that webcams were only good for planets and you absolutly needed a CCD for deep sky imaging? How can this webcam succeed in taking deep sky objects?

The DSI is easily good enough to mag 17-18 on a 5" telescope. How Deep Sky do you want?

[Dave Mitsky]

2.) Telescope webcams are crap. They are only for you if you just want to go cheap and only get pictures of the Moon. They give very blurry images of planets. You need a high quality imager like a Meade DSI if you want to go that way.

I wouldn't exactly call webcam planetary images like these crap.

http://www.astroshow.com/mars/ccdmars.html

http://www.astrophoto.fr/jupiter.html

http://geogdata.csun.edu/~voltaire/saturn1.html

For more on the topic, see http://www.astrophoto.fr/ccd_video.html

Dave Mitsky

[Hatan]

Thanks a lot for your answers, this is very much appreciated. You answers actually bring up some more questions :)

Assuming money is not an issue, I guess the DSI from meade would be much better for planet and moon imaging than the StarShoot Solar System Color Imager II from Orion?

What about Deep sky objects, which one would create better results, the DSI from meade or some other CCD for the same price range?

And, according ozark1, it looks like that B&W ccd are better than color? Why? I prefer to have my planets in color than B&W usually :) I guess it has to do with the fact most DSO will not have color anyway and you need to have the filters to create them?

Thanks again.

[Siguy]

I have seen planetary pictures from Meade DSI cameras, and they look about the same as pictures from normal webcams, but they are mainly used for deep sky.

I don't know of any other CCD for the same price as the DSI.

Most CCDs for deep sky imaging are black and white for some reason, and all professional ones, including the ones NASA uses, are black and white. I forget why, but it's good just to get the filters.

[Peter Wilson]

Basically, in a color camera, you are recording 3 different colors at once. This reduces the effective sensitivity by a factor of 3. This lost sensitivity doesn't matter for daylight cameras, but for astrophotography...