The size of telescope needed to see Mercury's phases

[Matt1979]

I have not seen Mercury much as a 777ft. hill blocks my western horizon, but when I have seen Mercury with my 60x spotting scope, it only appears as a tiny disc, not much more than a dot. Can a 3 inch refractor such as my Celestron (72x when using Barlow Lens) show the planet's phases? The manual to the telescope does say that it would although it doesn't specify magnification. I don't think I have ever heard what the smallest required telescope size is that will show the phases.

[DirkSteele]

In my smallest scope (105mm) I have seen the phases of Mercury at between 60-80x magnification but that is contingent on the seeing conditions being relatively good as the planet always looks small, and any atmospheric turbulence tends to wash out the phase rather easily, which given Mercury is never seen far from the horizon is more common than we would like.

[Paul M]

It's a long time since I looked at Mercury through a telescope but I saw it display phases in my old Dixons own brand (re badged Tasco?) 60mm refractor.

My memory is of it being a reasonably easy, if small target.

It's not so much the telescope that matters as the elevation of Mercury above the horizon and sky brightness. Throw all the aperture you want at it but if the conditions are poor you'll still struggle.

[Matt1979]

In my smallest scope (105mm) I have seen the phases of Mercury at between 60-80x magnification but that is contingent on the seeing conditions being relatively good as the planet always looks small, and any atmospheric turbulence tends to wash out the phase rather easily, which given Mercury is never seen far from the horizon is more common than we would like.

Thanks for letting me know. I thought 60x would probably show the phases in good seeing conditions. Sadly, when i saw Mercury near the end of May, it was against a very murky sky and only just above the horizon and was so discoloured it looked orange-red so these conditions would obviously not show the phase.

[Matt1979]

It's a long time since I looked at Mercury through a telescope but I saw it display phases in my old Dixons own brand (re badged Tasco?) 60mm refractor.

My memory is of it being a reasonably easy, if small target.

It's not so much the telescope that matters as the elevation of Mercury above the horizon and sky brightness. Throw all the aperture you want at it but if the conditions are poor you'll still struggle.

A good point. Mercury was against a very murky grey sky when I saw it and practically on the horizon. When I first saw Mercury through my 60x spotting scope in late February 2007 the planet was much higher and it seemed to just about show a gibbous phase although its small size and discoloured appearance (it looked pink-orange the first time but not as badly discoloured as it was five weeks ago) made it very difficult to see if I could definatley make out the phase.

[Paranoidsam]

Be careful looking at Mercury... you don't want to catch the Sun by mistake.

[Matt1979]

Be careful looking at Mercury... you don't want to catch the Sun by mistake.

I always make sure the Sun is set when I look at Mercury. On the two occasions I have seen the planet it was in a dusk sky.