SBIG ST-8 as a first CCD?
Posted 22 May 2010 - 09:43 PM
I have a used Meade DSI-2 which I use for guiding my DSLR, but the thought of not needing a piggybacked guidescope has some appeal. I may stick with my current setup for a while (I am by far the weak link in my setup...), but I figured that I'd get some more experienced opinions while the sale is going on.
Posted 24 May 2010 - 05:03 PM
are you talking about the ST-8XME for $3k?? my opinion is that it is far from a starter camera. you will have to spend a chunk more on a filter wheel and filters. NABG, i think will be a challenge limiting exposure time (or dealing with blooming in post). if you want "pretty pictures", i recommend staying away from NABG cameras.
i use a camera now with self guiding and although i like it (vs. guide scope), i could not do it without an application like "The Sky" helping me figure out a guide star. linking my telescope to "the sky" and comparing real time images from the camera vs. where i am relative to a guide star was all new stuff i had to figure out when i went to self guiding (far from newbie as far as i was concerned). guide scope was so simple. finding a guide star without an app like "The Sky" would be a so frustrating.
do you want mono or color? there are some much lower priced mono (and color) options from orion and QHY. also, the new craze for 8300 chips is providing some nice packages.
hope that helps.
Posted 24 May 2010 - 11:24 PM
- It would (I think) shorten the setup time of the scope for each session (I don't yet have an observatory) but I may be wrong about this.
- I have a 10" newt and a big dob for visual. Currently, I'm using a Meade DSI-Pro 2 on the newt for guiding and imaging with a piggyback camera and telephoto lens. If I switch the DSLR to the newt for imaging, I'll need to purchase a refractor for guiding. Admittedly, an 80mm refractor is an order of magnitude cheaper than an ST-8.
Ultimately, I'm wondering if my best near term solution is to build an observatory. I'm not sure if I'm going to be at our current house for more than a couple years, so that's one hesitation there. So, I was hoping that an ST-8 with its self-guiding capability would make the setup and teardown less painful and eliminate the short term requirement of a guidescope, but perhaps that is wishful thinking. If I remove that aspect (i.e. autoguiding), then I agree with you that the 8300 or the mid-level Orion or equivalent CCDs make more sense for my current abilities or lack thereof.
Anyway, thanks for your insights. Sorry that I didn't articulate more of this in my original post.
Posted 25 May 2010 - 01:40 AM
If imaging faint fuzzies in reasonable time is your goal then it is a good choice.
The on board guider chip has both good points and bad ones. The bad one is that it can make finding a guide star difficult compared to other systems, especially when doing narrow band imaging. Also a guide star that looked fine in the L, R and G filter may not work with blue in that most fainter stars are red and don't emit a lot of blue light so when that filter gets switched in there goes the guide star. Also the guider chip is red sensitive adding to the problem. Always check blue beforehand to avoid this nasty surprise. Other guiding methods don't look through the filters so avoid this issue.
On the other hand flex from a separate guide scope can be very challenging to solve. I did it for years with film and sometimes it worked great. But then there were those other times! While I rarely guide (I have my Paramount so honed it isn't needed for 10 minutes even at 0.5" pixel size) when I do I've not found finding a guide star difficult at all. I do use The Sky but never used it to help find a guide star! When looking for one I just move the object down 5 minutes in my FOV. Any potential guide star is now seen in a 5 second exposure. If none I move the other way 10 minutes and again look for one on that side. I've never failed to find something usable on one side or the other but then I'm using a 14" scope but at 3650mm FL so my guider chip is small. Also since I don't rotate the camera if the guide star is on the wrong side I just wait and image that object when it is on the right side of the meridian. I have such a long to-do list this isn't an issue. Though my lack of guiding may also be a savior. I normally only guide if subs are longer than 20 minutes which is narrow band only. Mount quality has a lot to do with this. Better the mount and better it is polar aligned the longer you can expose a guide star and thus how faint you can go. I prefer not to guide with less than 10" exposures when I do as this averages seeing and I get a better fix on the star's real position. Many mounts can't do this however. I spent 50 years using such mounts
Some DSLR users find moving to mono a bit challenging, others find it no problem. You might want to get some time on an on line scope using a mono camera and see if it is for you.
ABG makes taking pretty pictures less of a hassle but increases imaging time. Many feel it worth the time others don't.
Matching pixel size to seeing is another issue. A small pixel camera like the 8300 fits a shorter FL scope and is rather ineffective on a 2000mm scope unless you have better than average seeing though binning is an option with a mono camera that preserves the high resolution for those rare nights of super seeing.
An observatory is great but if you're only there 2 years more build one you can move. The next owner will likely make you remove the pier as us amateurs are a rare breed. For now I'd think learning the ropes by moving the DSLR to the 10" (flattener like the one Baader sells will likely be needed) and buying a small refractor with a solid focuser (weak ones will sag even with a light DSI-2) would be a cheap way to go. Save the next move until you move and can build the observatory. In the meantime save for the best you can afford in gear.
All CCDs and DSLRs are a compromise, none is perfect. You will have to decide with compromises you can live with and which you can't, including budget, and dive in. The ST-8 may be an old chip but it still can take some fantastic images, so can most others when properly matched to scope and target.
I should go back and edit this into something that doesn't ramble but this is just how my mind was working tonight.
Posted 25 May 2010 - 12:51 PM
If you are in a light polluted area your exposures will be shorter due to fogging from light pollution. In this case the much more sensitive NABG chip can yield more data within the short exposure time.
Posted 26 May 2010 - 09:52 AM
Posted 19 September 2010 - 08:32 PM
Rather than the ST-8, why don't you give the Starlight-Xpress H9 a try. You don't need to take dark frames, it's sensitive, and doesn't bloom. Great mono camera to start out with.