24 replies to this topic

[fcathell]

After catching Titan, Rhea, Dione and Tethys in my C90 Mak at 208X tonight, I figured I would try for the craterlets in Plato.  In 45+ years of serious observing, I've never looked for these, so I thought I would try after reading a post here on CN about them. Not a trace, even after waiting until the moon got reasonably high. One thing I became acutely aware of was all the stuff I can see in my eye and any traces of dirt on the eyepiece (I assume) field lens. After a little experimenting with eyepieces I found that 165X was about all I could do on the moon without being seriously aggravated by floaters, other unworldly looking things, etc in my eye.  I assume that this is due to the small exit pupil caused by the combo of the 90mm aperture and magnification.  It appears that a 0.5 mm exit pupil is about all I can tolerate on the moon.  This is not an issue on Saturn or Jupiter, but neither is the glare/brightness factor.  I may have picked the wrong moon phase also to look for these craterlets.  I think I read that the optimum time is around a 12 day old moon. Then again, maybe a 90mm aperture is just not adequate for visual detection. Comments from you seasoned lunar observers are definitely welcome.

 

Frank

[John O'Hara]

You could do one of two things: Get a binoviewer or use more aperture.  Even an inexpensive binoviewer can work well on the moon and planets (I have an old Burgess unit).  The .5 mm exit pupil is also my "magic" number, where my floaters take over with a single eyepiece.  

 

I've only made one serious attempt to see craterlets in Plato, a successful one.  I used my astronomy club's 14" Meade LX 200 with an Orion 16.8 mm MegaVista eyepiece (212x).  The seeing that night was exceptional.  I've not tried in smaller scopes, but you've given me a challenge.  

 

Incidentally, this is Challenge 128 in Phil Harrington's book, Cosmic Challenge, which would be a great guide for this task.

[Don Taylor]

I have seen a few (the one near center, the one about the same size about 1/2 way to the S rim, and the two slightly smaller ones nearly touching also about 1/2 way NW from center to rim) with my deforked 90mm ETX but generally have the same problems with floaters as you.  I do a bit better with the 4" ED or the ETX125TB.  0.5mm is my limit too but I do better with a little larger exit pupil. I see some really strange tree limb like objects floating by.........

Edited by Don Taylor, 08 November 2019 - 10:36 PM.

[RadioAstronomer]

Interesting. I just came back from observing the moon (also in Tucson) with my TV 102 at 176x (5mm Pentax SMC Ortho eyepiece) and saw three Plato craterlets. Two of them were very easy.

[PirateMike]

Keep trying Frank, you will see them sooner or later. 

 

 

Miguel   8-)

 

.

[Codbear]

Frank,

 

I believe it's all about seeing and aperture to identify as many craterlets as possible. I've seen 6 craterlets with my C14 Edge HD. I just got a new NP101is and will be interested to see how many it can pick off with its 4" aperture.

 

Also John...thanks for the reference. I have just purchased Phil Harrington's book you alluded to and I'm sure I will enjoy the challenges. Interesting that there are 187 challenges - you might say it's a real "killer" of an endeavor!

[Astro-Master]

HI Frank, I read a post on CN about a year or so ago about the Plato craterlets, it had some nice photos with the diameters of the craters.  I tried for them first with my Stellarvue 105mm APO, I think I saw three or more.  The next night I tried with the 180mm  Intes Mak-Cass, I think I saw 5 or maybe 6, I should have taken notes.

 

I don't usually look at the moon, I'm more of a deep sky observer.  I'll have to give it a go again and this time I'll take some notes

[Asbytec]

Plato Challenge. One of the great observing threads on CN.

https://www.cloudyni...lato challenge

[NorthernlatAK]

I just came back in from observing and was focused on the aristarchus plateau region, but took a gander at Plato to see if I could see anything. To my surprise, I was able to see several bright albedo spots where the craters are at 266× in my 8" dob. Would this count as an observation of the craterlets?

[Astro-Master]

Plato Challenge. One of the great observing threads on CN.

https://www.cloudyni...lato challenge

 

Thanks Asbytec, that was the great post I remembered reading that made me want to take the Plato Challenge.

[Redbetter]

Some of this is likely familiarity with what these craterlets look like in different conditions and apertures, and detection vs. seeing it more as a crater.  Finding them first in somewhat larger aperture provides some discrimination between the real and imagined.  It has been awhile since I studied them, but have found the big 4 or 5 accessible with small apertures when conditions are favorable.  Tonight I took a quick look with the 60ED then the 80ED.

 

The 60ED showed A as a vague brighter spot not quite centered.  I had some indication of it even at medium power but confirmed at 90 and 120x.  The floaters/texture of my eye are a challenge for this at 0.5mm exit pupil, but I had vague indications of two others:  B and the C/D pair (not individual).  I wasn't really sure on either, the seeing was not that steady and I didn't recall what the orientation should be.  (I did a check on Rigel just to make sure I was seeing Rigel B.)

 

I brought out the 80ED to see if it revealed more.  The scope was cooling some, but its own thermals were not the primary obstacle:  even after a time I noticed that some local thermal effects were impacting the seeing for considerable spells.  Despite that A was seen immediately in a better stretch.   I cycled through 100, 120, and 150x trying to confirm the others and felt I was seeing them more frequently and in the same orientation, but not quite consistently enough. I was getting a wide triangular lighter albedo affect on the crater floor next to one of the suspects, which I believe was B.  

 

I haven't kept score with the 80 on these, but on good nights I think I have been able to recognize C and D individually with it (though marginally), and perhaps detected E as well.  I know I have done so with the 110ED and 127 Mak.

[AJK 547]

Plato Challenge. One of the great observing threads on CN.

https://www.cloudyni...lato challenge

Many thanks to you CN’ers (and that excellent thread!) in nudging me into this challenge!  It took a great night of transparency and ‘seeing’ for me to bag ‘em as true craterlets (not albedo) in the C8-A (Delos 8 + Baader 2.25X Barlow).  ‘F’ and ‘W’ came in and out of view over the next hour.  Too bad those nights of excellent seeing are sooooo rare.

 

A later session I tried my C6 (w/Delos 3.5) on the craterlets (during a night of <average seeing), only 'A' resolved as a ‘pit’... B, C/D just ‘albedo’ sadly.  Too much power + below avg seeing = no success!

 

My next challenge is the Vallis Alpes ‘Rille’ on a night of excellent seeing and transparency.  Any recommendations on what it takes to discern the rille as a true depression?

Edited by AJK 547, 09 November 2019 - 08:21 PM.

[BillHarris]

Another good thread on Plato's craterlets is

https://www.cloudyni...ato-craterlets/

The OP tried to see these craterlets at a colongitude of about 51*. Plato has a longitude of about 9*, so this makes for a solar elevation of about 40*. The three largest craterlets are about 1 arc-sec (about 1.5mi/2.4km) in size, which is marginal in a 100mm scope, and likely impossible at that sun elevation. I'd try again about 1 to 1-1/2 days after Plato sunrise, at a colongitude of 20* to 25*. I've been able to barely discern the largest craterlets under a low sun and good seeing with my Questar 3.5.

Good luck and keep trying!

[Asbytec]

My next challenge is the Vallis Alpes ‘Rille’ on a night of excellent seeing and transparency. Any recommendations on what it takes to discern the rille as a true depression?

As with the craterlets, seeing is king. Hang in there. IME, the rille is tough in a 6 inch even when seeing is nice, but it can be done even if marginally so. Keep at it until things come together one night.

[Astroman007]

I must try for these craterlets myself, next night of the right phase and sunlight angle.

 

My highest magnification at the moment is about 130x, but I'll give it a go regardless. Worst case scenario, I'll enjoy a good view of the Plato ("Greater Black Lake") region.

[NorthernlatAK]

I must try for these craterlets myself, next night of the right phase and sunlight angle.

My highest magnification at the moment is about 130x, but I'll give it a go regardless. Worst case scenario, I'll enjoy a good view of the Plato ("Greater Black Lake") region.

That will be real tough... My guess would be you need a minimum of close to 250× and some excellent seeing. Let us know how it goes!

[Astroman007]

That will be real tough... My guess would be you need a minimum of close to 250× and some excellent seeing. Let us know how it goes!

I might be getting a 2x 2" Powermate before year's end, taking advantage of that Tele Vue sale. Regardless of timing I'll be getting one at some point. That would definitely help.

[AJK 547]

I must try for these craterlets myself, next night of the right phase and sunlight angle.

 

My highest magnification at the moment is about 130x, but I'll give it a go regardless. Worst case scenario, I'll enjoy a good view of the Plato ("Greater Black Lake") region.

Astroman007,

 

FWIW, it took my C6 (coupled with Delos 4.5, then Delos 3.5) to resolve as true ‘pits’.  As everyone mentions above, wait for a night of at least VG+ seeing and transparency to give yourself a good chance at bagging these little craterlets (the Big Four ... A, B, C /D) as ‘pits’.

 

The C6 w/ Delos 4.5 gives me ~333X... the Delos 3.5 gives ~428X...  you can imagine that pulling 71X/in out of the C6 requires truly excellent seeing as you well know.

 

My C8 (with the Delos 3.5) gave me ~581X that excellent seeing night/morning and the detail I observed on the Plato ‘Massif’ was something to behold.  To see detail (visually) like the detail of the Massif ‘split’ from the crater wall was pure enjoyment’.

 

I’ve included an image of the ‘Massif’ (I found on the internet) that gives a good idea of how excellent the seeing was that unique observation night.

 

Good luck!

Attached Thumbnails

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Edited by AJK 547, 19 November 2019 - 10:10 AM.

[Frisky]

I was out tonight looking at Plato and Sinus Iridum. At 155X, I couldn't see craterlets. I went inside to get my barlow and a few other eyepieces to hit it with high power. I walked back outside and clouds had moved in! It's still cloudy, so I'll probably have to wait for another chance. 

 

Joe

[AJK 547]

I was out tonight looking at Plato and Sinus Iridum. At 155X, I couldn't see craterlets. I went inside to get my barlow and a few other eyepieces to hit it with high power. I walked back outside and clouds had moved in! It's still cloudy, so I'll probably have to wait for another chance. 

 

Joe

Joe, last night I was observing Hadley Rille (and testing my C8 equipment) and intermittently saw ‘The Big Four’ (A, B, C/D) when I turned my scope to Plato.  Seeing and transparency was only Avg+ but I immediately saw ‘A’.... then the other 3 came in and out of view.  I was using 406X to start, then upped to finally to 677X.  
 

What I suggest is use a high power EP that gives you the finest resolution, contrast, etc. .... wait for proper lighting within the lunar cycle... wait for VG+ seeing/transparency/jet stream/etc.  ... AND (as Damien Peach says  “precise collimation, precise focus, optimal OTA acclimation and seeing” is required for success.

 

Good luck and Clear nights.

Edited by AJK 547, 07 December 2019 - 05:38 PM.

[Qwizatzhaderach]

Relative newb here, but I was just looking at Plato minutes ago only an ST80 with pretty good seeing, at 115x, and can’t see them at all. I can make out a few with a much bigger scope (8” dob), but they’re not huge. Is it possible to resolve them with an 80mm or 90mm scope? Just guessing they’re near the edge of what’s resolvable? Could be wrong just asking anyone who light know with certainty.

[Frisky]

I was out in poor seeing but tried anyway. I hit Plato with 339X and 309X. No go. Last night would have been the night and I blew it by waiting too long and letting clouds roll in. Tonight, I had to look through thin clouds and had gusty winds. Just not good conditions. I think they'll be doable with my 120mm under the right conditions. I'll definitely try again and again.

 

Joe

[AJK 547]

I was out in poor seeing but tried anyway. I hit Plato with 339X and 309X. No go. Last night would have been the night and I blew it by waiting too long and letting clouds roll in. Tonight, I had to look through thin clouds and had gusty winds. Just not good conditions. I think they'll be doable with my 120mm under the right conditions. I'll definitely try again and again.

 

Joe

Joe, IMHO if you can detect the ‘A’ Craterlet (nearly centrally located within Plato) then conditions are probably good enough for sporadic detection of the ‘Big Four’.  In avg.+ seeing, I immediately detected ‘A’... then ‘C/D’ came into view after a few minutes of viewing... finally ‘B’ briefly showed itself.  
 

The litmus test with my C8 was if I could discern various rock formations on the ‘massif’ on the southwest wall.  If I do, it’s a go for detecting these pesky little dudes.  I need a comfortable eyepiece like the Delos or Delite because I’ll spend quite a bit of time just waiting for that brief moment when the craterlets reveal themselves to you.  
 

*** As you know, VG+ to Excellent seeing is most important.  I usually start with ~450X then move up or down from there.
 

Good luck and Clear nights.

Edited by AJK 547, 08 December 2019 - 09:53 AM.

[JimFR]

I did catch the ’A’ last night in my 5 inch mak.  The sky was pretty quiet and the temps settled at 0C  with no further drop through the night.  I put the scope out just after 7pm and let it stablize.  Since the temps barely budged, scope was dead stable by 9.  The Baader zoom at 8mm is the highest I can reach with it and I can’t use that end of it on the scope very often but definitely last night.  It took about 200x to find A and I came back to it several times to be sure.  I think the other larger ones are in reach if I can get a hair more magnification.

[Redbetter]

Had somewhat better seeing tonight (and dew) before the fog rolled in.  I took out the ED80 to catch Armstrong, Aldrin, and Collins (and possibly Sabine C.)  The sun angle was such that these were just brighter spots.  I then turned to Plato and was able to use up to ~170x.  I didn't have a craterlets chart with me and hadn't worked out the RA and alt-az flips so I had to work back through what was detected.  I was sure of A, B, C/D (as elongated albedo feature), as well as what turned out to be E, and possibly g. 

 

Wish I had been better prepared as I had some hints of other albedo differences that might have corresponded to others.  I don't know that I have seen as many with this scope before.