Hi Joe, I can't say as I'm not familiar with your imager. However, here's info on the ST-6: http://www.sbig.com/sbwhtmls/st6b.htm Cheers, patrick On 30 Oct 2010, at 23:42, Joe Bauman wrote:

Hey Patrick, how does it compare with my little ST-402XM? Is it a better camera? Thanks, Joe

On the newer rebels, XS, XSi, T1i, T2i, it is a 4 digit number. With the 16gig card I use on the XSi, I can shoot about 1000 full resolution raw format images. If I change that to the largest resolution jpg, it reads 3378. That does make more sense. The "burst" mode is only a few frames at a time, and really depends on which resolution you are at. It can do a lot more low rez .jpg's in a burst than full raw format. They are handy without laptop's, but are very handy with them as well. With the EOS utility, you can fully automate your shooting. I can setup an astro session, and go nap for a few hours. Here are some dark frame comparisons done by Gary Honis showing the 450D(XSi) the 1000D(XS) and the 550D(T2i): http://ghonis2.ho8.com/RebelMod550D/rebelmod550dcompare.html You can clearly see that even with the digic3 processor, the noise levels hold their own with this camera. 450D is a great astro camera, and all around general purpose DSLR. David On 10/30/2010 11:02 PM, daniel turner wrote:

Kurt:

I fear you are mistaken about the 4 shot limit. That sounds like the limit on the number of rapid fire shots that can be taken before the camera has to slow down and wait for the memory card to catch up. It varies with model and with options in use at the time.

The true shot left counter is a three digit number and depending on the model, card size and resolution can often be seen at 999 which means "more than a thousand". So you can shoot all night or all week if you wish and download at your leasure later.

Newer models have a "live view" mode that allows you to focus without the aid of laptop software.

I use a DSLR to avoid having to take a computer to the field with me. It contains everything needed to do the job on it's own and it greatly simplifies the process.

DT

--- On Sat, 10/30/10, Canopus56<canopus56@yahoo.com> wrote:

...

From: Canopus56<canopus56@yahoo.com> Subject: [Utah-astronomy] Purchase advice on Canon Digital Rebel XS, XSi To: "Utah Astronomy List Serv"<utah-astronomy@mailman.xmission.com> Date: Saturday, October 30, 2010, 6:17 PM I am getting ready to buy my first DSLR and I would like to buy a Rebel XS or XSi. This would be a general purpose camera but I want to cross-purpose it as an astronomy camera. I feel the cheaper XS model meets my needs.

I am unclear on:

1) For time lapse night time photography of a large sky section with the 15mm lens, how do you get the images off the camera in real time since it only holds 4 shots?

2) Other advice of comments are the purchase are welcome.

Thanks - Kurt

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Bob, You brought up a few points here I was curious about regarding color noise and luminance noise in relation to the pixel size. I tossed a few of these issues up on cloudy nights to get some more feedback. http://www.cloudynights.com/ubbthreads/showflat.php?Cat=0&Number=4158749&pag... I would think also that color noise degrades and image as much as luminance noise does, and if not, the difference would be little. Apparently the DIGIC4 only affects the jpg compression, not the raw. So even with basic processing of one shot, the T1i and T2i look like they would have inferior performance than the XSi if you compare the images that Gary Honis put together, even with the DIGIC4. Usually the more pixels you cram into the same APS-C sized sensor, the more secondary electronics, the more heat, the more noise. Shooting more involved shots with a DSLR is not that involved. There are free full package programs out there like Deep Sky Stacker that make the whole process very straight forward and easy. So instead of shooting 1 30 second exposure, you could shoot 30, and a few darks. Maybe some flats and bias if you want to get further into it. The final result isn't "over-processing" it is simply stacking the images to create a better light signal to noise ratio so the final result looks a lot better. I think this is a better approach than over compressing the image to get rid of noise, as this creates a lot of ugly jpg artifacts. The color balances, white balance, everything of this nature that keeps a natural look can easily be preserved. I am just saying that with a little more effort, the final results can be greatly improved. David On 10/31/2010 10:27 AM, Robert Taylor wrote:

David is correct with regards to astro-photography. The XSi have larger micro lenses (5.15 nm) than the T1i (4.68 nm) and therefore would have the better Chominance noise performance or those dots on the darks. For Astro-photography Chrominance noise is a factor. However for day to day shooting luminance noise is far more important and relevant, Chrominance Noise isn't really a factor.

Luminance noise is digital grain, here the Digic 4 cameras, T1i or T2i, are superior to the Digic III cameras, XSi or XS, hands down. Because you said you wanted a general purpose camera the T1i or T21 are better bets and will give you a lot more flexibility and superior results when shooting around the Christmas tree, on vacation and at the next family wedding, etc. They do a superior job in low light which translates into noticeably better shots in low light and even in medium light: in doors and late day shots for example, everything but bright sun. You will be able to get good shots with a T1i or T2i that you simply will not be able to get with an XS or in some cases the XSi. However for astro-photo purposes there are some advantages to the XSi, but only for astro-photography and only if you are going to shoot multi shots, stack, subtract darks, etc.

http://www.slas.us/gallery2/main.php?g2_itemId=1348

This is a single 30 second (actually a little less than 30 seconds) shot with a Digic 4 processor camera or "Asto-photography made easy" as I like to call it. There is only basic processing on this image; I only spent a few minutes on it, if that. I have since reprocessed it as I've gotten better with PhotoShop and it looks even better and I've pulled out more detail. This is not the reprocessed shot, it is the original with just basic processing, this better shows what the Digic 4 cameras can do without a lot of PhotoShop or post processing. One of the keys is to shoot in RAW, not JPG. These short shots may not be what you had in mind but thanks to the newer camera's ability to deal with noise and use very high ISO settings without the usual problems of long exposures, increased noise, both kinds for example, these very short astro-photos are now possible and practical in many cases.

If your choice is between the XS or the XSi, get the XSi as I originally suggested. The small difference in price will be more than worth it unless every penny counts and you are willing to give up some picture quality and have more missed shots due to the older and inferior auto focus system on the XS compared to the XSi. The XS is an old camera design and is long overdue for replacement; it will be replaced next year from what I understand. The XS is a camera for those that buy strictly on price. It's a collection of older parts and pieces Canon had hanging around from old, obsolete cameras like the Rebel XT and XTi, then they dumbed it down, removed features, made it slower, less capable, etc. The XSi is a couple of versions back from the current T2i but is still an excellent and a fairly current camera with regards to its technology and specs whereas the XS is not current technolgy. Did I mention the XS is older technology? The XSi is a generation above the XS.

In the world of Canon DSLR Cameras the number of numbers in the name will tell you what level the camera is, the more numbers the more entry level the camera is. The XS for example also goes by the name 1000D (4 numbers), the XSi also goes by the name 450D (3 numbers), that alone tells you the XSi is geared a little higher to the Enthusiast level and is a more capable camera whereas the XS is geared toward the Beginner/Entry level and is marketed just to get you into the Canon line-up knowing you will soon want a better camera. By comparison the 2 number cameras (40D, 50D and new 60D are aimed at the Pro-Sumer level, capable of professional results but without the Pro-level build and features for those that want more than a consumer grade camera but aren't ready to shell out the bucks for their pro grade single number cameras like the 1Ds, 1D, 5D and 7D series cameras which are the top of the line for Canon.

That said the XSi is one of the best of the Rebel series, you won't be disappointed and I highly recommend it as an all around camera unless you want to shoot video as well as stills in which case you have to get the newer T1i or T2i. Another important difference is the XS has 12 bit color depth; all the others mentioned here have 14 bit color depth which gives you many more colors graduations than a 12 bit camera like the XS. This will eliminate any banding which you can and will get with a 12 bit camera like the XS - just another reason not to get the XS. Again the XS is an entry level camera whereas the XSi, T1i and T2i are Enthusiast level cameras and more capable.

So really - at least get the XSi, it is a much better value than the XS for just a few bucks more.

Let us know what you decide. This is what happens when you ask people for opinions.

Bob

-----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of David Rankin Sent: Saturday, October 30, 2010 11:35 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Purchase advice on Canon Digital Rebel XS, XSi

On the newer rebels, XS, XSi, T1i, T2i, it is a 4 digit number. With the 16gig card I use on the XSi, I can shoot about 1000 full resolution raw format images. If I change that to the largest resolution jpg, it reads 3378.

That does make more sense. The "burst" mode is only a few frames at a time, and really depends on which resolution you are at. It can do a lot more low rez .jpg's in a burst than full raw format.

They are handy without laptop's, but are very handy with them as well. With the EOS utility, you can fully automate your shooting. I can setup an astro session, and go nap for a few hours.

Here are some dark frame comparisons done by Gary Honis showing the 450D(XSi) the 1000D(XS) and the 550D(T2i):

http://ghonis2.ho8.com/RebelMod550D/rebelmod550dcompare.html

You can clearly see that even with the digic3 processor, the noise levels hold their own with this camera. 450D is a great astro camera, and all around general purpose DSLR.

David

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