Another Lunar 100 ite

[Moonshane]

Observing Report 24th April 2010

Location Stockport

Equipment – 12” Orion Optics UK Dobsonian

Main Target: Lunar 100

I only recently became aware of the Lunar 100 list and it is an excellent way of concentrating observing time on specific targets. Previously I have only spent time (rather enjoyable time it must be said) scanning the surface for interesting features but never really taking time to learn the various names of the craters, rilles and laval seas that make up the surface of the moon. Personally, I have been inspired by Mick (Doc) to do this as his reports ‘got me going’ and I know others have also said the same thing, so cheers Mick! I have put links to the objects which are all open access but I thank the photographers who have created such great images. I have waffled on a lot here. Sorry about that but sometimes my enthusiasm boils over. The comments are a mix of my own observations and the text in the checklist I was using.

My initial intention was to try and compare the viewing with my 12” Dobsonian reflector and my 120mm achromatic refractor. Although I set them both up and got them cool, the mist rolled in a little thicker and it threatened a shower or two. As the refractor takes a lot longer to strip down than the Dobsonian I decided to err on the cautious side and take the refractor inside. As it happened it stayed dry all night but the cloud increased as the evening went on and made viewing eventually impossible.Despite the poor conditions, I managed to work my way through a good number of features on the waxing, slightly gibbous moon.

The Lunar 100 is design in such a way that the targets become more challenging as you work you way through them. Below is a summary of the features I managed to see during this evening. I basically started at zero as I wanted to see the full list over the next few months or so.

1. The Moon

LPOD - Lunar Photo of the Day - February 16, 2004

Yes, simple as that. Look up and see our satellite neighbour. First one ticked off.

3. Mare/Highland Dichotomy

http://the-moon.wikispaces.com/Mare-Highland+Dichotomy

This is the basic difference between the darker, usually flat laval sea areas and the paler and rocky crater laden or mountainous regions. Again, this is a naked eye target with which almost everyone in the world must be familiar.

4 Apennines

http://the-moon.wikispaces.com/Montes+Apenninus

This large and obvious range of mountains is part of the wide Imbrium basin rim and is again a naked eye object; certainly very visible through binoculars. It stretches right across a large area of the upper central lunar surface and there are lots of different areas to explore with the telescope. It is a very useful marker point to locate other targets.

6 Tycho

http://the-moon.wikispaces.com/Tycho

Just visible when I viewed the moon , this is a large rayed crater with a central peak. One of the most impressive craters with pale rays which extend over a huge area of the lunar surface.

7 Altai Scarp – Rupes Altai

http://the-moon.wikispaces.com/Rupes+Altai

This feature shows as an obvious sinuous line covering a long distance in the south-eastern quarter of the moon. It effectively joins the craters of Piccolomini and Catharina (see below).

8 Theophilus, Cyrillus, Catharina

http://the-moon.wikispaces.com/Theophilus

http://the-moon.wikispaces.com/Cyrillus

http://the-moon.wikispaces.com/Catharina

These three craters close to the Altai Scarp create a sequence illustrating different stages of crater degradation. Theophilus has a central peak and overlaps the older Cyrillus.

10 Mare Crisium

http://the-moon.wikispaces.com/Mare+Crisium

This is one of the laval seas which cover the surface of the moon eradicating a huge number of earlier craters. Mare Crisium is contained in a large circular basin in the north-east quarter of the moon.

12 Proclus

http://the-moon.wikispaces.com/Proclus

This is a crater which has large and very obvious oblique-impact rays. They spew out across Mare Crisium on two sides only indicating the direction of travel before impact.

15 Straight Wall – Rupes Recta

http://the-moon.wikispaces.com/Straight+Wall

Straight Wall is a good example of a lunar fault line. Despite being a somewhat plain feature, it was one that intrigued me the most. It looked somewhat ‘man made’ but clearly seems to be where the ground had dropped away along a straight line which stands out really well in shadow.

16 Petavius

http://the-moon.wikispaces.com/Petavius

This is a crater with a domed and fractured floor as well as a central peak. As it was in a bright area of the moon, it did not reveal as much detail as I’d hoped but I will watch this again next time the terminator is closer to it.

18 Mare Serenitatis

http://the-moon.wikispaces.com/Mare+Serenitatis

This is on the list as there are distinct mare areas with different compositions and this was obvious when looking at the area in the telescope.

19 Alpine Valley – Vallis Alpes

http://the-moon.wikispaces.com/Alpine+Valley

This is a long and wide cleft in the mountains close to the large lava filled crater, Plato. Quite impressive and worthy of further detailed exploration in due course.

20 Posidonius

http://the-moon.wikispaces.com/Posidonius

Another large, floor-fractured crater at the edge of Mare Serenitatis.

21 Fracastorius

http://the-moon.wikispaces.com/Fracastorius

This large crater was not very obvious but easier once located. It is at the base of Mare Nectaris and the ‘seaward’ side has subsided, presumably inundated with lava flows. The floor is fractured and again this would be a good one to look at further in the future.

24 Hyginus Rille - Rima Hyginus

http://the-moon.wikispaces.com/Rima+Hyginus

This is a long rille snaking through the centre of a small crater, Hyginus. It contains rimless collapse pits and I managed to see at least three or four of these. Really quite impressive at higher magnifications.

25 Messier and Messier A

http://the-moon.wikispaces.com/Messier

Although quite small, this close pair of craters are in a laval area otherwise flat and dark so they are actually quite prominent. The fact they are the result of an oblique ricochet-impact can be seen clearly as the rays extend in only one direction, again indication the direction of travel of the meteorite or whatever else cause the damage.

26 Mare Frigoris

http://the-moon.wikispaces.com/Mare+Frigoris

This area is a dark laval sea above the crater Plato, and it extends horizontally across the upper area of the lunar surface.

41 Bessel Ray

http://the-moon.wikispaces.com/Bessel

This is a somewhat faint ray near the Bessel crater that is apparently of uncertain origin. It extends a good way across Mare Serenitatis.

I really enjoyed this session and will certainly be back for more, aiming to complete the 100 over the next few months or so. Given that the moon lights the whole sky virtually, it is a good way to spend your time in a less frustrating way than trying to locate DSO’s etc when the moon is up.

One thing that is rather obvious really, but surprised me nonetheless, is that when looking at the moon with a fast reflector at reasonably low magnification you may see the secondary mirror housing. This was most prominent with the 24mm Panoptic even with a 13% moon filter fitted. It is obvious why I suppose as even though the (unfiltered) exit pupil with my Dob is only 4.5mm, it is clear that such a bright object, will encourage contraction of the pupil and therefore the exit pupil is much larger than my own pupil. It’s really quite strange sitting up from the scope and having one pupil dilated and one contracted – a bit like those eye drops they put in to check for eye problems if you have ever had it done, but the complete opposite.

Although it’s bearable, and worse if you move your eye away a little from the ‘best position’, I suppose stacking another moon filter or using a variable polarising filter might be the answer to the secondary issue; I have one on order from Scopes N Skies for £3. This approach may also solve problems where you use a wide field lens in a faster scope for general use. I am thinking about trying this if I buy a 40mm Aero and use it in the Dob. This would then get around the possible exit pupil issue (which would be 7.5mm in the Dob) and also allow me to get a wider field of view (1.7 degrees in the Dob and 2.7 degrees in my refractor).

I have a further report to write for the night of 26th April when the moon was almost full and this will follow another day.

Cheers

Shane

[Doc]

A really nice read Shane and very imformative. I'm glad I managed to get a few of you guys interested in Lunar, I hope you enjoy it as much as I do.

It's very strange that you see a shadow of your secondary while observing the moon. I have never had this problem, and my 16" is very bright.

[Tantalus]

That's an impressive list you got there Shane with good details. You can update your sig line now.

Out of curiosity, (technical issues aside) what gave you the more pleasing views - the 'frac or the Dob?

Those polarising filters sound like a bargain, Let us know how you get on with it.

[Moonshane]

A really nice read Shane and very imformative. I'm glad I managed to get a few of you guys interested in Lunar, I hope you enjoy it as much as I do.

It's very strange that you see a shadow of your secondary while observing the moon. I have never had this problem, and my 16" is very bright.

cheers Mick

I agree, I have noticed it also when using my 33mm 2" eyepiece, especially when the sky i still blue. it's not unbearable though as I say, although slightly annoying as the full moon fits perfectly in view with the 24mm Pan.

[Moonshane]

That's an impressive list you got there Shane with good details. You can update your sig line now.

Out of curiosity, (technical issues aside) what gave you the more pleasing views - the 'frac or the Dob?

Those polarising filters sound like a bargain, Let us know how you get on with it.

cheers - list updated!

I have to say that rather surprisingly to me anyway, the dob was far better at this target. for some reason, the field of view seemed wider to me and things moved across it slower. now I am used to the dob, and as I am definitely visual only for the foreseeable future, I prefer the dob for everything. you have more light, more resolution, more magnification and more detail on almost all subjects; I have only found the frac better on one single target which was Epsilon Bootis a reasonably bright double star. it's easier to use, quicker to set up and actually takes up less space than the frac/tripod/mount.

there's nothing wrong with the frac by the way and it's a great scope (hence me keeping it) but I prefer the dob.

[jgs001]

Nice start Shane, and well written up. I really must get back to the Lunar 100 and see if I can get closer to finishing it... maybe I'll just start again...

[Moonshane]

cheers John

it's really great to pay the old girl some attention.

I'd start again if I were you - I'll probably do it a few times I think.

[PeterW]

My lunar eyepiece is a 5mm Nagler, smallest exit pupil I can take without the floaters bothering me and wide enough field of view to prevent me having to keep moving the scope about all over the place. I've just begun to get over bid dob aperture fever... my skies make deep skies not worth the effort. I thought that lunar observing would allow me to go for smaller, higher quality optics... seems like the 'curse' of the BIG DOB is lurking here too.

Once we have all run off the Lunar100, I have found some others:

AstroLeague Lunar I and Lunar II observing clubs.

Observing List | The Astronomical League

Lunar II Club Introduction | The Astronomical League

A huge collection in a spreadsheet that helps you work out what is best to observe.

Lunar Observation Planner Spreadsheet with Lunar Terminator Calculator- project homepage

Should keep us busy for a while!

PEterW

[Moonshane]

cheers Peter! really useful :0)

I can see lunar observing becoming a bit addictive.

[Talitha]

Wonderfully written report Shane! Messier and Messier A always make me giggle... they look like a pair of robot-eyes shooting death rays at crater Leakey.

[pvaz]

Great report!

I'm also starting this, unfortunately the clouds are working against me this past week. To be honest I was never that interested on the moon but with this trend Mick started I'm feeling motivated to make the most of it.

[Moonshane]

ha ha cheers Talitha - I see what you mean. we obviously share the same kind of weird imagination - see my next report http://stargazerslounge.com/observing-lunar-solar/103204-lunar-100-update.html where I prove that I have lost my mind in a couple of the observations.........

Thanks Paulo - I agree, Mick is a proper trendsetter. it makes total sense doesn't it, that if you cannot beat them then join them - if the moon is so bright you cannot see anything else well then have a proper look at it while you can

There's so much detail on the moon. We all struggle to see a bit of a cap on Mars with a squint and is it, isn't it?? a spot on Jupiter ... but you can actually see inside craters maybe 2km across on the moon - amazing!