andrew s

Strehl ratio also has issues. It refers to actual v ideal, however ideal is a function of both wavelength, and aperture (and possibly design depending on the definition you use) . I think it's fine if you compare like with like say 5 " APOs but comparing a 1" APO with a 5" APO would make no sense. Regards Andrew

I have a wide range of power tools I could use but will choose not to. Regards Andrew

Sorry, it was just a quick test to see if as @mikeDnight said he could resolve the plants better with the detail vertical rather than horizontal. This was intended as a quick test. I had not considered the display characteristics influencing it. Regards Andrew

I did it with the screen in both orientations and got the same result. But ideally a printed gray scale would be best. Regards Andrew

It would be good to test @mikeDnight observation on vertical v horizontal resolution. Do you loose resolution differently with the two sets of lines in the first image in the link as you recerd from it? Pick the high contrast pairs next to each other. I get a difference. Regards Andrew

Moving it slightly made it pop out for me. Regards Andrew I just noticed it was very clear when scrolling the page. The diagonal line blur and it leaps out.

Thanks, that is the process I had in mind. Regards Andrew PS just seen a YouTube clip where they used a jubilee clip to cut against to keep it square. Might try that if I can get one big enough.

How much did you remove? Any advice on the best way to do it? Just got mine and want to use a Herschel wedge with it. Regards Andrew

So no fancy new technology glass APO refractrors or eyepieces then. Regards Andrew

You could use an eye patch on your observing eye and use the other for reading maps. Regards Andrew PS remove eye patch when observing!

Welcome Jamie, Ely is my home town but now in Cheshire. Enjoy SGL. Regards Andrew

Not tried it yet. Will update when I have. On dew, it can't stop it if the air temperature is below the dew point. All it can do is stop it cooling below the air temperature. Regards Andrew

More like a score draw.🪐 Regards Andrew

It fits very well. When you increase magnification you dim the background sky as the light is spread but not for unresolved point sources thus it increases the contrast Regards Andrew

Thanks @JeremyS it's clear there is a whole wealth of information on visual observing that lays forgotten in old journals. More to ferret out. Regards Andrew

Very nice. You may need a sun shade and a bottle of white on ice. It's hot today. Regards Andrew

What type and focal length eyepieces are you using the the Barlow? Regards Andrew

Thanks @Pixies that was a fantastic read. I still need to follow up the references but it translated a lot of what I had been reading into the astronomy context. Thanks Andrew.

I have set myself the personal goal of researching the science of visual astronomy with the aim of trying to satisfy myself that if all the relevant science is taken into account does it explain the claims of skilled visual observers or not. I think a lot of the issue is that partial explanations from limited fields (say just optics) is used and often out of context. An example might be that "a 1mm exit pupil is optimum" without context or qualifications. Regards Andrew

Not one I have got but Anazon has one for £216.25 second hand so look after it. Regards Andrew

As part of my reintroduction to visual astronomy I have been reading "Foundations of Vision" by BW Wandell. It's fascinating stuff at least to me. One, amongst many, things I just learnt was that vision goes from trichromatic to dichromatic to monochromatic with both increasing spatial and temporal frequency. Put along side the loss of colour perception with lowering light intensity it's no wonder we all have different experiences with magnification. Regards Andrew PS They look like lemons to me, at a distance, with the lights off.

@Sunshine I did a short note on it for the BAA. You can see it here https://www.pixelskiesastro.com/article (with permission of the BAA Journal Editor) Regards Andrew

Whatever floats your boat I take between 1000 an 2000 images/spectra a night of the same star to try to catch it flaring. Regards Andrew

The human visual system is a lot more than the optics and receptors in the eye. We learn to see. As a learnt skill we will all develop our prefered strategy. As an example I tend to pull away from blured or pixellated images to try to sharpen them up. I am currently reintroducing myself to visual astronomy and it will be interesting to see how this develops. Regards Andrew

You can easily measure the magnification. Measure the size of the exit pupil when scope is pointing at day time sky. Calipers or a ruler will do. Just look down the eyepiece from 50 or so cm back. Divide this into the aperture of the scope gives the magnification This assumes the binoviewer does not vignette the scope Regards Andrew