Yes polar align is the only alignment mentioned in the manual.
I have been looking at your equipment list. The M31 at the top of the thread was captured with a scope. Consider using the Samsung 135mm instead if the lens weighs less than the scope. Reducing the weight the tracker has to carry will help with tracking and hence allow exposure time to be increased.
As you gain more experience with the equipment your images will improve. My M31 above was the result of 4 years of imaging. I made lots of mistakes. Hours wasted with poor alignment, poor focus, bad balance and lack of understanding of calibration frames. Persistence is the key.
Dave
Reasonable Expectations
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Lensman6626
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Re: Reasonable Expectations
I'm hoping for a bit of clarification on a point or two that've been creating an itch in the back of my mind since watching Robin's fantastic Youtube lecture, that it's appropriate to this thread (apologies if not). Obviously one of the main takeaways (if not the main takeaway) is that sub exposures can be a lot shorter than had commonly been believed heretofore--so much so that some (e.g., Richard Wright) have concluded that 'guiding must die'. My beginner-level assumption is that what this means is that exposures can be short enough that tracking errors from one sub to the next can be taken care of after the fact by stacking software (please explain if I'm going wrong here).
My first practical question is: at what point does this occur? How short must a sub be to avoid streaks and other artifacts--sort of a 'rule of 500' idea. I'd imagine this would depend on location of observer and target as well as how accurate the mount is. Could one use something like RMS periodic error to make an estimate? I've read that guiding incurs many headaches and conversely that it's not much of a problem, but it strikes me that the fewer processes, the better, and hard drive storage is getting cheaper all the time.
The second question relates to modifications for OSC cameras and narrowband filters. The rule-of-thumb figures from the lecture suggest a factor 3 for the former and 25-100 for the latter, if memory serves. But what about both at once, as might happen if using, as some suggest, multiband filters (e.g., Radian Triad or some such) with a OSC? My simple-minded thinking would be that here factor might be around the 25 figure, since you're admitting three bands.
So the overall question boils down to: would it be feasible for one use the OSC + tri-band filter and take short enough subs to avoid guiding?
My first practical question is: at what point does this occur? How short must a sub be to avoid streaks and other artifacts--sort of a 'rule of 500' idea. I'd imagine this would depend on location of observer and target as well as how accurate the mount is. Could one use something like RMS periodic error to make an estimate? I've read that guiding incurs many headaches and conversely that it's not much of a problem, but it strikes me that the fewer processes, the better, and hard drive storage is getting cheaper all the time.
The second question relates to modifications for OSC cameras and narrowband filters. The rule-of-thumb figures from the lecture suggest a factor 3 for the former and 25-100 for the latter, if memory serves. But what about both at once, as might happen if using, as some suggest, multiband filters (e.g., Radian Triad or some such) with a OSC? My simple-minded thinking would be that here factor might be around the 25 figure, since you're admitting three bands.
So the overall question boils down to: would it be feasible for one use the OSC + tri-band filter and take short enough subs to avoid guiding?
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Re: Reasonable Expectations
Hi,
two good questions...
You have fairly much answered the first one yourself - there is so much variation in equipment and setup (how well the mount tracks, how well it is aligned, pixel size of camera, focal length of telescope, quality of focus) that it is hard to give any meaningful rule of thumb. Even if you use all the same setup and equipment, results might vary in different parts of the sky (if your polar alignment is off in the E/W direction, you will hardly notice it when imaging to the east or west, but it will introduce a dec drift when imaging near the meridian).
All of the above means that the best bet is to just try things out - work upwards from the SharpCap recommended exposure until you start to see issues with elongated stars (even if they only happen in some frames), then go back down a bit until you stop seeing issues.
On the second one, if you are using a multiband filter on a colour camera then you can just take account of the multiband filter and ignore the bayer colour filtes on the camera itself. The reason is that if (for instance) one of the channels on your colour filter is Ha, all the red light getting past the Ha filter that strikes red pixels will pass through the red filter on the pixel (which is a much wider bandpass anyway). Therefore the pixel filters don't further reduce the light level and can be ignored for the purposes of exposure calculation.
cheers,
Robin
two good questions...
You have fairly much answered the first one yourself - there is so much variation in equipment and setup (how well the mount tracks, how well it is aligned, pixel size of camera, focal length of telescope, quality of focus) that it is hard to give any meaningful rule of thumb. Even if you use all the same setup and equipment, results might vary in different parts of the sky (if your polar alignment is off in the E/W direction, you will hardly notice it when imaging to the east or west, but it will introduce a dec drift when imaging near the meridian).
All of the above means that the best bet is to just try things out - work upwards from the SharpCap recommended exposure until you start to see issues with elongated stars (even if they only happen in some frames), then go back down a bit until you stop seeing issues.
On the second one, if you are using a multiband filter on a colour camera then you can just take account of the multiband filter and ignore the bayer colour filtes on the camera itself. The reason is that if (for instance) one of the channels on your colour filter is Ha, all the red light getting past the Ha filter that strikes red pixels will pass through the red filter on the pixel (which is a much wider bandpass anyway). Therefore the pixel filters don't further reduce the light level and can be ignored for the purposes of exposure calculation.
cheers,
Robin