andrew s

That applies to a large number of threads! They are organic and evolve. I normally find a thread is reaching its end when it reduces to a series of jokes. I have tried to kill a number of Takahashi threads this way without any success. Regards Andrew

And what is wrong with abstract may I ask? I have just found an interesting paper that shows experimental results that the eye can detect a single photon . In doing so it turns up the gain so it is more likely to detect the next few. Which is an excellent strategy given that light follows London Bus statistics (Poisson) which makes "photons" bunch togather. Regards Andrew Harmless fun.

I agree, it is much ore complex than just truncation the top of an Airy disk. Regards Andrew

Yes, but the eye/brain only integrates over a few second. Is 50 to 150 hits enough to define the 2D Airy disk that well. I think not. We will just "see" an unresolved somewhat localised source on the edge of visibility. Clearly, this needs some controlled experiments rather than more theoretical speculation! Regards Andrew

I fully agree provided you have enough illumination. The interference pattern builds up one detection at a time. You need enough detections for the pattern to appear. At the limit of detection is this true? Regards Andrew

Might be better to discuss a perfect continuous detector. The size of a photon is a whole new can of worms, even if it has a well defined meaning at all. Regards Andrew

Just to complicate matter even more. How relevant is the Airy disk at limiting magnitude. Clark in "Visual astronomy of the deep sky" says you need 50 to 150 photons of green light over several seconds to detect a star unaided. If it is a similar limit for the aided eye then just how well defined will the Airy disk be? Most will be concentrated in the central peak but it is not as clear cut as @vlaiv diagram with just the peak showing. Regards Andrew

Not only is the eye on linear it is non uniform. In addition the angle of incidence effect the response of the rods (and cones). Averted vision, blind spot and all that. For more details see the pdf I linked to above. Regards Andrew

I came across this pdf https://www.brayebrookobservatory.org/BrayObsWebSite/BOOKS/EVOLUTIONofEYEPIECES.pdf that tells you more that you might want to know about the history of eyepieces. However, it has an appendix on " Apparent luminance of telescopic image" which is well worth a read. It includes a consideration of the angle of incidence of the ray on the rods and cones of the eye something not yet discussed here! And I thought quantum optics was a stretch and classical optics straight forward. Silly me. Regards Andrew

Fully agree, regards Andrew

I certainly defer to your greater experience. Looking at the out of focus image made me consider it looked a bit rough but it is very difficult to separate roughness and seeing. Regards Andrew

Unfortunately rather looks like one or other of the mirrors . Regards Andrew

One last idea. If you rotate the camera say 30 deg does the pattern shift relative to the diffraction spikes? If it does I might be the camera. Regards Andrew

Are the edges of the secondary blackened? I would strongly suspect scattered light. I don't know this scope but I would look for and shiny surfaces in and around the tube focuser, primary mirror cell etc. Regards Andrew

It is. Regards Andrew

Don't cry for me my brass Ramsden I never left you... ..because you froze to my eye! 😱😭🥶 Regards Andrew

Oh dear, plugging an upcoming book in the first answer without even answering the question. Regards Andrew

You might also see if it happens with the star in the centre of the field. Regards Andrew

Ok toss a coin, heads refractor tailes coma corrector. Don't go with the result but your emotional response to it. Regards Andrew

Might you need a field flattner for the refractor ? Do you want a drop in aperture? Regards Andrew

Hi @carastro, the weather in Castillejar has been very poor but the next two nights are looking good so I hope you are in luck. Regards Andrew

Which way round do you use it? Regards Andrew

@vlaiv is it not possible in software to not just do a nxn average but a more nuanced reduction using a better algorithm? Regards Andrew

Do you have to look last the central obstruction? It's shadow in the exit pupil will be significant! Regards Andrew

Does anyone really care? Apart from the odd visual variable star estimate visual observation have long been discredited as too prone to oberver expectations for serious , ,scientific work. That has freed it to be a pleasurable pursuit, a do as you want , disregard what you will hobby. I am not being down on visual astronomy as the same applies to most imaging. The aim is to have an enjoyable time and a pleasurable outcome. Magnify as little or as much as you will. Regards Andrew