andrew s

Hardly a difficult ethical issue. Just do it. Regards Andrew

Proof of @ollypenrice comment can be found here http://www.rocketmime.com/astronomy/Telescope/SurfaceBrightness.html Regards Andrew

Of course not. It would have issues with achromatic distortion and absorption just to highlight the most obvious ones. Regards Andrew 😤

At least they don't need to wait for a clear night and work on it 24 / 7 Regards Andrew

Commercially viable fusion energy is still 10 yrs off. Just as it has been ever since I was old enough to keep records. 😊 Regards Andrew

I have noticed the cooling can be overwhelmed if you take multiple flats, or flat-darks with very short exposures so when doing this I add a delay otherwise not. Regards Andrew

A minor comment or two. Formally, Nyquist requires point sampling (in addition to other criteria) but a CCD or CMOS pixel integrates over an area. This also means they are not shift invariant i.e. the result depends on where the image falls in relation to the pixels. So again, formally, linear analysis like MTF etc. don't strictly apply and simulation is needed for accurate results. In my area spectroscopy, sampling at higher density than Nyquist is required for accurate estimation of line centre, line width etc. Regards Andrew

To have an independent meter would over specify the system of units unless you dropped c or the hyperfine frequency. It's just a matter of choice given our current understanding of physics which "things" appear to be constants of nature. I don't know of a candidate for length. Regards Andrew

It's not circular. In the modern SI system the derived units are as far as possible expressed in terms of fundamental constants. In the case of the meter we combine c and a hyperfine transition of a Cs to define the meter. The value if c is given by definition, it could be any value, but was picked to best match the previous accepted value. All the gory details are here Regards Andrew

We can in fact see galaxies moving away at up to about 3c ! "Speed" due to expansion of the Universe is not like kinematic velocity and this can exceed the speed of light. Of course the lesson of relativity is that there is almost certainly something moving relative to you at all kinematic speeds up to the speed of light. Regards Andrew

Still got to get it collimated and we all know how hard that can be especially when the actuators move at the speed that grass grows! 😉 Regards Andrew

No it would rotate relative to the camera. A 90 rotation if the camera would produce a 90 rotation of the pattern. Regards Andrew

This first thing I would do is check the secondary is correctly centered under the focuser. Regards Andrew

Just don't damage your L2 moving it. Regards Andrew

I take it books don't count as astronomy equipment as per your new years resolution? Regards Andrew

All the selfie cameras in the world would not have shown Hubble's myopia! They do, however help keep the paying public engaged. Regards Andrew

All purchases are equal but some are more equal than others. 😉 Regards Andrew

Maybe worth a try? https://arxiv.org/abs/2112.12673 Daylight Photometry of Bright Stars -- Observations of Betelgeuse at Solar Conjunction Regards Andrew

A simple way to calculate magnification is to measure the diameter of the exit pupil as see by looking into (from a small distance) the eyepiece. Divide this into the size of the entrance pupil i.e. normally the objective diameter and that's the magnification. Only need it roughly focused at infinity. Can be done by the fire in daylight! Regards Andrew

Nice work. Regards Andrew

Nothing new to add but when taking multiple short exposures (bias, flats, flat darks) I have found that the temperature control may not keep up. So I add a delay between them to ensure stability of the electronics. Regards Andrew

I have been very satisfied with mine too but only had it for about 18mths. Regards Andrew

Just one point spotting scopes are sealed and to a good degree waterproof for use in damp or even wet conditions. Astronomical scopes with changeable eyepiece are certainly not. Might be worth considering depending on your use. Regards Andrew

@saac you could start here for how the probe is designed. Regards Andrew