Last updated: 26 June 2005

Subject:	Craterlets in Plato
Sent:	Thursday, June 23, 2005 08:23:12
From:	C.A.Warburton (
Thought I'd email you about an observing session I had last Saturday
18th June with my MIGHTY ETX-90. I was actually testing out a couple of
new eyepieces and comparing them to my existing ones.

Being a budget ( and not very dedicated astronomer ), I had purchased a
32mm Celestron and a 20mm Omcon from Ebay ( 16.00 and 10.00
respectively). ( both these eyepieces incidentally are made in Taiwan.

Through the Celestron 32mm the moon was an inspiring sight. I could see
the whole of the globe ( being 4 days from full ), a very crisp image in
the central 75% of the field but I did notice that the image became
increasingly mushy toward the field edge.

The 20mm was awkward to use as my face tends to foul the finder with
short eyepieces, but coupled with my Apo Barlow it performed quite well
showing decent  contrasty views.

What really did surprise me though was seeing a craterlet on the floor
of the crater Plato. Even though the Moon was very low in the sky at
around 10.15 pm and not fully dark. At a magnification of x125 with the
Barlow and the 20mm Omcon E.P. I centred Plato in the field and there
was very distinctly a small crater flickering in and out of sight.

I tried a couple of my other eyepieces ( these included a 9mm Sky
Watcher Ultra Wide; a Seben 14mm ED; an Orion Explorer 11 zoom and an
Orion Epic ED-2 5.1mm ) I found that in the 9mm and even the Zoom I
could see the craterlet in Plato.

The 14mm didn't seem to have enough magnification and the Epic ED2 had
too much.

I was amazed when I checked out the size of these small craters. The
largest seems to be about 1.5 miles across, just on the resolving limit
of the telescope! What an amazing scope!

I tried the Omcon and the Barlow on Jupiter. I could see five belts and
a little additional detail in the belts but it was very low in the sky.
One problem I did notice with the Omcon was ghost images. There was a
small ghost blob floating around opposite Jupiter and a more diffuse
ghost area in the centre of the field .

I hope my somewhat inexpert observations are of interest Mike.

Thanks for a great site.

Kind regards,

Chris Warburton.



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