You misunderstand the difference between “a few minutes before drifting off the target star” and “maximum exposure time” before a star starts to blur in an image/the background becomes too bright for usable images.
You misunderstand the difference between providing an argument with appropriate sources and pulling something out of one's rear end. You have provided no sources for this, and therefore it is the later.
If the limitation is the camera exposure then on the MIT telescope why, exactly, is the limit for an unguided mount max exposure only up to 5 minutes, while the exposure for guided mount is listed as 60 minutes plus?
This is a catastrophe of an argument. But really, it is obvious that this argument is no mistake. You clearly just came here to make things up and lie to us.
Tom, I don’t need to cite the sources you yourself have already provided. Your citations only prove what I’m trying to say.
I’m going to say something that I should have made clear in my first response to you. When you’re talking about astrophotography, which your sources are, the “max exposure time” is the maximum time you can shoot before the start begins to visibly drift in frame, resulting in non ideal photographs. It does not mean that the stars or planets just fly out of frame within seconds or minutes, as you seem to imply.
http://www.pk3.org/Astro/index.htm?astrophoto_mount_errors.htmAs per your first source, and so there is no confusion -
“Telescope mounted on equatorial mount is rotating in opposite direction of Earth rotation, thus no trails should appear. The word SHOULD is used intentionally, because there are several factors which affect perfect tracking:
The mount should be perfectly aligned with Earth's polar axis. Any deviation of mount's polar axis from Earth's axis causes tracking errors.
Even quality machined mount parts like worms, worm gears, shafts are not absolutely perfect. The parts are machined in micrometer precision at best. We must realise that in astrophotography we require tracking precison up to arcseconds. That means, that e.g. teeth of teeth on perimeter of wheel with diameter of 8cm must be machined with accuracy of hundreeds of nanometers!
As mount's shaft rotates, any error in its surface and shape and also in worm and worm gear surfaces and shapes causes a periodic bump in tracking. The most observable is so called periodic error of the mount which is caused by inaccuracy of of worm. The period of this error takes one revolution of gear (usually 5-10 minutes for common mounts).
More expensive mounts has possibility to suppress this error by means of electronics - Periodic Error Correction (PEC). The principle of PEC is based on recording tracking corrections made by observer by star tracking during one period. This tracking corrections are then applied during normal mount use.
Atmospheric refraction causes that stars are not moving exactly according to their calculated trajectories.
Further effects - tripod, scope, focuser and other parts firmness, vibrations, thermal changes agffect the result tracking accuracy.”
https://starizona.com/blogs/tutorials/exposure-timesAnd for your second source, a blog, discussing exposure time -
“For deep sky imaging, suffice to say that longer is always better, at least until light pollution starts to overwhelm the image.”
Again, these sources, the ones you have provided, prove my claim. Being able to accurately track a body through the night sky depends on the mechanical precision of the equipment, which can never be prefect, and the accuracy of the alignment on the celestial poles.
https://web.mit.edu/wallace/instruments.htmlYour third source, the MIT telescope.
It appears the professional telescope is accurate enough to track(for astrophotography purposes), unguided to compensate for inevitable mechanical inaccuracies, longer than most amateur setups can while guided. Not surprising.
I’ll say it again as you ignored it in my last reply. Time lapse photography of the night sky reveals concentric circles around the celestial pole, proving my point about EQ mounts while removing the problem of their inherent mechanical errors.
I’ll repeat that this is impossible on a flat plane with objects circling around overhead. The only place that would work is on the North Pole of a flat earth map, and that’s quite clearly not the case.
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