Ah, perhaps it's not the software for me. I'm looking to use my dSLR for photographing heavenly bodies. I suppose in order to get some really breathtaking pictures, I'm going to need a tracking device of some sort. In the mean time, what advice can you give me with regards to focusing with the dslr and reducing fringing.

Kyle,

I think you read wrong. I have read that the ISO is about 10,000 or higher, and that's right. You can barely take a daylight exposure with those cameras without taking ridiculously short exposures through the filters--which are very narrow-band and therefore cut out most of the light.

If I take a five-minute exposure of M42, the core will be totally blown out and even the faintest of regions will be visible. With a DSLR, those faint regions won't be visible even at 10 minutes.

The quantum efficiency of the astrocameras ranges from 50% on the low end (meaning 50% of the photons that hit them are converted to signal), to over 90% on the high end. A great comparison is the STL-11000XM and STL-11000CM (with color). The QE peaks at 51% for the XM, and peaks at 42%, 37%, 34% for BGR, respectively. This means the color version peaks at an average of 38% QE, or roughly 35% less sensitive than the monochrome.

Your DSLR has a similar array on it to the STL-11000CM, but the chip also has inherently less sensitiivty--I have heard the average is about 30% QE at max. This means the QE on the STL-11000XM is about 70% greater than a DSLR--approaching twice as much QE.

Next you have huge well depth compared to DSLRs--this is why we take long exposures. We can with those cameras, and still get good data. It also maximizes the S/N ratio (the noise is higher becuase the ISO equivalency is so much higher--hence the peltier cooling as well).

Now let's talk some really sensitive cameras--like the back-thinned SITE chips, with 90+ QE. A 30s exposure with one of these easily reveals Barnard's Galaxy, or detail in the spiral arms of M51. Lots of detail. There is just no comparison to a DSLR....

Jeff

DSLRs are a great way to get a big FOV and not spend that much money, plus you dont need a computer in the field unlike with a CCD. CCDs however let you do a lot more with images. They're much more expensive but most serious astrophotographers go into CCD work. A BIG thing that DSLRs cant do is H-alpha (certain wavelength of light) astrophotography. DSLRs take RGB single shots. Most CCDs are not single shot RGB, but instead B&W. You then add a color filter wheel in front of the CCD and then taken a very long luminance frame (B&W), R, G, B, and then can do other things such as H-alpha to add even more detail to the image. DSLRs block out a lot of H-alpha stuff, its just the way they are. You can tell a difference between a shot of an object with and without H-alpha data, it just adds so much to it.

However, DSLRs are great for widefield work and a great way to get started. There are also some serious imagers with DSLRs, though they realize their limitations. CCDs being cooled is helpful and then some, the images can be so much cleaner.

Jeff,
Thank you for the link, very interesting information there. I know Terry's website, but didn't know that he also made QE measurements.
But still, looking at the 300D curves and comparing it with the one of the 11000(C)M I can't see much of a difference:

300D: