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Started by Kevin Barker, 08/22/2002 04:58PM
Posted 08/22/2002 04:58PM Opening Post
I have asked questions about Plato before. Here is another.

Two nights ago(between showers) I observed Plato a couple of days before full moon. I find a full moon is also a good time to view plato and the surrounding areas.

I viewed 4 craterlets including the double craterlet.
Telescope was a 130 mm apochromat. Power used 166 X.
Seeing was OK perhaps 7/10. Antares was split OK at 166 X. Nu scorpio's double double was just discernible at 125X.

I was not able to discern the 5 th craterlet that is closer to the triangular wall feature(See Rukl's map)3 or 4??

What aperture do others find necessary to view these craterlet?? Especially the 5 th. I have viewed these 4 in a 100 mm apo too and the central crater in a 63 mm refractor??

Your experiences on this fascinating crater are rrequested??

Best wishes

Kevin Barker
Posted 08/22/2002 05:35PM #1
I find the 5th to be a little tough in my 10" Disco PDHQ, but you're right - full moon is a good time for Plato...

Posted 08/22/2002 06:12PM #2
Kevin, 5 or more craterlets can be observed with an 8" Newtonian, if the seeing is good. I'll have to give Plato a try when the moon is full. I've been inclined to observe it a day after 1st quarter. Darian Rachal

[COLOR="Blue"]Darian Rachal[/COLOR]
Posted 08/23/2002 02:09PM #3
Hi Kevin

Last night I failed to see ANY craterlets in Plato. I was using a Widestar 4" (older model) 600 mm focal length, TV 2.5 powermate and 10 mm Clave'. The moon was only about 25* above the horizon when I abandoned observations due to cloud. How many craterlets can be seen do you think with the above setup? Seeing was average at best. How difficult are the craterlets to see with your 100 mm?

I found this using googlesadPlato craterlets view)
Quote" A few years back they were under such odd, cooperative light that I'm fairly sure the five majors would have shown easily in an 80mm scope. "End of quote.

I also found this David Kingsley account on same search:
Quote " For the Plato test, I began with a Vixen 24 to 8 mm zoom eyepiece ccombined with a Celestron Ultima 2x barlow. That gives a maximum magnification of about 240 in the 7 inch Starmaster. Views were very steady, so I put the same zoom eyepiece into a Televue 3x Barlow instead. At full zoom, that combination gives a maximum magnification of 360x in the 7 inch Dob (just over 50x per inch). Views were still nice and steady, so that's what I used for the rest of the night. When I first looked at the moon, I could make out 4 small craterlets in the otherwise smooth floor of Plato, (a tight double pair, and two single craterlets in a curving arc). I didn't have an atlas with me, so decided to sketch positions for later comparison to Rukl and photographs. As I have often found before, the act of sketching was a big help in teasing out additional detail. As I carefully studied Plato to make my sketch, additional craterlets begin to pop into view. One was near the western edge, as prominent as the first 4 that I had seen. This one had been missed before only because of its proximity to the rim. Then smaller ones began appearing near the original single craters near the center. These were harder to hold, like faint companions of a difficult double star. But I was patient, the sky was steady, and as I remained seated and still at the eyepiece, several small craters became obvious. I had sketched positions of 12 craterlets when the skies finally clouded over for good at about 1:15 am."End of quote.

Anthony @ 41*S 175*E

Posted 08/24/2002 12:09PM #4
Kevin, Some time ago I counted 12 craterlets with a 6" f/8 Celestron refractor. I live in New Orleans where oppressively muggy, hot, still conditions prevail all summer with poor transparency but often outstanding seeing. (Transparency is generally not an issue with the moon ha ha!) It was such a nite. Here is my post to my club:

As a followup to an interesting thread a couple of weeks ago at the Yahoo Telescope forum I spent 3 1/2 hours counting Plato's craterlets with a 6" f/8 Celestron refractor last nite. I started around midnite.

I am extremely excited to report counting 12 craterlets "fair and square". I confirmed the count by drawing what I saw just after I finished and comparing the drawing to the photo in the excellent free program "Virtual Moon Atlas" that Jack told me about. To tell you the truth I was quite surprised how well they all matched up. There was a 13th that I did not draw because I didn't feel certain enough of it but it showed up in the photo too!

I tried eyepieces all the way from 10.5mm to 4mm. They were:

Eyepiece FL Power Exit Pupil

Pentax XL 10.5mm 114x 1.31mm
Brandon 8.0mm 150x 1.00mm
Edmund RKE 8.0mm 150x 1.00mm
Pentax XL 7.0mm 171x 0.88mm
University OR 6.8mm 176x 0.85mm
Clave' Plossl 5.0mm 240x 0.63mm (Thanks Ron!)
Orion Ultrascopic 5.0mm 240x 0.63mm
TeleVue Radian 4.0mm 300x 0.50mm

The 8mm Brandon consistently produced the best images for counting but differences in seeing always linger in my mind with "tests" like these. However as the nite wore on it was pretty obvious that it consistently took less effort to count with the Brandon and more of the craterlets were obvious all the time.

The 7mm Pentax was a close 2nd with an entirely different image. The darker areas were not as dark as the Brandon (or several of the others) but the craterlets were visible for counting. I only saw all 12 with the Brandon and the Pentax. Apparently 5mm and down just produced more power than the conditions could handle for these craterlets.

Its interesting to note that a side trip to Schroter's Valley had the 4mm Radian producing the best image. Aristotles and Eudoxus at times
were spectacular with all eyepieces.

BTW, I had a 9.25 SCT set up to do a comparison but the images were so good in the 6" that I never got to it. Maybe I'll get there next time. It goes without saying that I was impressed with the images in the 6" achromat. I didn't really notice color at all with Plato or any of
the mentioned features but I wish I had taken a few peeks thru the 9.25 just to see what colorless really looked like last nite......but then I may have wound up up all nite. Clear skies!

Ralph Junius