Sunday, 22 January 2017

A Low Contrast Moon

Hooray!  Scope time!!!

Of late, I’ve whinged many times about the lousy weather we’ve had over the last few months.  This latest stretch really has been just terrible.  If not overcast, then too hot, or seeing has been miserable.

Earlier this week I did manage some time with a scope with a mate who came by with a couple of new scopes (a couple of lovely refractors) and some eyepieces.  We had a great time putting his scopes and eyepieces through their paces, and using his eyepieces in a Newtonian of mine for comparison.  Seeing was not great, but we managed some good testing of his gear with our combined experience.  No sooner did we call it quits, clouds rolled in, spelling the end of a potential Moon sketch for that evening… <sigh>

This Sunday morning was surprisingly clear, and the Moon was pretty much at zenith (straight overhead).  At 9:30 in the morning, the Sun is well up, and the sky a brilliant bright blue.  While the Moon looks lovely and bright up in this bright blue sky to the naked eye, through a telescope, the Moon is a very low contrast object, and only a low power proposition.  Yet, the blue and white composition really appealed to me!  Knowing that I had sky blue paper, I decided that the Moon was fair game today, and the low contrast challenge made it all the more appealing to me as I haven’t undertaken such a sketch before – yep, I’m a weirdo… LOL!  So, I set up my ED80

First thing to decide on was the optimal magnification.  Very low, the contrast is improved, but the details are too fine.  High magnification, the contrast is too low to make out any details.  So for the first time I used my Baader zoom eyepiece.  The zoom feature makes it much easier to figure out the best magnification to use.  So, today, 20mm was just right.

Not have experienced such a low contrast situation before, I was on new ground to work out how to go about this.  Colour selection of the soft pastels was the first.  Black was out straight away as it is just too strong and not actually what’s seen through the eyepiece.  I have a blue soft pastel, but it was too intense and not the right hue.  So, from what I had at hand, I decided to use white and the grey soft pastels.  The grey, while also too dark neat, it would be easier to tone down by going over it with the white.  And a little experimentation as I go along is also in the mix.

The image through the eyepiece was beautiful.  The leading edge being so bright and sharp.  The terminator faded into the blue of the sky gradually.  The maria, mountain ranges and craters varied so softly in shades of pale blue that it made keeping track of the feature I was laying down difficult.

This was not a sketch with which to lay down the most intricate of details.  I became aware that the piece would best resemble an Impressionist work, with only the gross details identifiable, and finer details hinted at with the texture of the paper and the way the soft pastel is handled.

After an hour I was done.  It became too difficult to pull out and follow the fine details as the low contrast was becoming too difficult to negotiate.  Only then did I examine the overall piece – and I surprised myself!  Soft pastel being what it is, depending on the angle that the piece is examined the brilliance of the paper is toned down, and the soft pastel begins to glow.

I hope you enjoy this piece as much as I do myself.


Object:  “Low contrast Moon”
Scope:  ED80 f/7.5
Gear:  Baader zoom @ 20mm, 33X
Date: 22nd January, 2017

Location:  Sydney, Australia

Friday, 6 January 2017

My scopes at the moment...

So, persistent cloud cover at night and terrible seeing conditions during the day have laid waste to any plans I have had for any sketching.  A couple of nights things cleared up around midnight, and of course I’m headed to bed… and then a couple of hours later it starts raining…

Oh, well, part of the deal with astronomy….

With this spell of poor astro weather, I’ve decided to look over the gear that I have.  Maybe move on some of it, and consider any things that may help.  Why I have the scopes that I have (too many…), and the bits and pieces that go with them, like eyepieces.  As eyepiece design needs to be matched to the telescope being used (all to do with matching focal plane shapes produced by telescopes), I’ll see if there are any eyepieces that I just don’t use enough, and find new homes for them.

There is no such thing as a “perfect telescope”.  Too many different functions are at play.  A really big aperture is nice for seeing the arms of spiral galaxies, but totally useless to see the wonderful network of dark nebulosity seen through the Milky Way, where binoculars or a rich field scope provides.  And while a big aperture can provide high magnification, it is also more suceppetible to the effects of atmospheric turbulence than a smaller aperture.  There is a trade-off always somewhere.  So a lot of people have a few scopes to cover different aspects of interest they have.  I’m no different, and may I confess, probably a scope tragic too…

Odessius:  my 17.5” f/4.5 cannon.  When I got this scope, it was configured as its original Coulter Optics Odyssey II SonoTube form.  Coulter made big aperture scopes affordable for amateurs in the 1980’s.  From 8” bubs through to a 29” monster that I drooled over ads in astro magazines.  And their mirrors were generally very good.  And for the time, these instruments were what defined “portability” in big apertures.  With hind sight, these were a nightmare to move around – my Odyssey II OTA occupied the entire passenger side length of my Mazda Tribute, from the front seat to the rear gate!  And the mount was a disaster.  But like I said, it was the best for its time.

When I got this scope from an old fellow astronomer, while the OTA and mount wasn’t much, the optics were just fine, and the primary mirror had been recoated only a year before.   When I got it home, the first thing I looked at was M42, and WOW!  I saw filaments of pink, blue and green in it!!!  Alas today I no longer can see these colours as my eyes have changed since then.

I got this scope with the thought of re-purposing the optics into a collapsible instrument.  The result was Odessius.  I was inspired by Albert Highe’s tri-strut 17.5” scope, and I fashioned my scope with my own take on things.  And Odessius is a joy to use.

Kulali:  This is my 8” f/4 compact travel scope.  Crafted by me, I can have this little scope sit on its own tripod, or coupled to an equatorial platform.

Kulali is my big aperture rich field scope.  With the right eyepiece, I can get a tick over 3° true field of view – the ENTIRE circle of the Veil Nebula fits in this!  Magnificent!  Kulali is one of a couple or rich field scopes that I have.

F4:  This is my grab ‘n’ go scope at home.  I built this 8” f/4 (see where I got its name from???) with a good mate of mine.  The tube came complete, but without a cell for the primary, which was easy to make one up.  As this scope is always set up, and always at hand, and very quick to cool down being a solid tube Newt., if I see a clear sky, I use F4 to tell me how seeing conditions are for plundering the Moon for a sketch.  And of course, I us F4 for whatever viewing I want to do at home.  As an outreach scope or a scope I lend to friends, it is wonderful as its mount sets the eyepiece at a comfortable height while seated.

I’ve modified the mount many times, using it as a test piece for ideas.  The way I have the cradle made up, I can quickly remove the OTA from it and place the OTA on an equatorial mount and use the scope for video astronomy – one thing this little gem of a scope excels at because of its big aperture and short focal length.

Orange tube C8:  When I was a kid, THIS was a dream scope of mine.  One of famous advertisement in astronomy magazines from the early 1980’s was of the late Leonard Nimoy promoting this model telescope:

This old timer is my high magnification scope I use for the Moon and planets.  When conditions are as good as they get, this scope’s optics allow me to push things to 400X with magnificent resolution.  Its mirrors may not be as pristine and reflective as when new, and the corrector plate doesn’t even have coatings (Special Starbright Coatings were an optional extra when new at the time).  Despite these “shortcomings”, the quality of the optics is just something else.  I’ve seen newer C8’s that are not up to the same standard as this old bird.

For a long time, this was the only instrument with a clock drive that I had.  Yet even now, unless I am doing video astronomy, this is the only clock drive scope that I use for visual observing.  The picture below is of myself next to the C8 about to do a sketch of the Moon.

Amgab:  this was first DIY telescope.  This 10” f/5 scope I built with the assistance of a friend who had access to some wonderful tools.  For the design I was inspired by “A Scope like Alice” made by Ron Ravneberg.  Ron’s two pole design reminded me of an article I had seen in a 1970’s Sky and Telescope magazine article which described the structural mechanics of different cantilever systems.  At the time I was also undertaking a Civil Engineering course at university and this particular article really appealed to me.   I understand the mechanics behind the viability of the two pole design, and coupled with Ron’s design idea, I came up with my own take on it.  I very much believe in the Amateur Telescope Makers’:  It is sporting to lift this design or that of someone else, as long as one adds their own unique design take on things.

 Amgab was my first big aperture scope.  It led me on a path of discovery within telescope making and innovative design.  I’ve seen many wonderful things with it, and taken it on many lovely outings, including with my family as its stowed configuration takes up so little space.  Amgab is the acronym of my friend’s name and my own.

Refractors:  I have three refractors at the moment.  I don’t need all of them and most likely will find a new home for one.  One is an ED80 that I use with my Daystar Quark filter with the Sun.  I tried out the Quark filter with many other refractors both achromats and apochromats, and found the good old ED80 f/7.5 to be a great match with the Quark.  Another refractor is a 100mm f/5 achromats which I use as a grab ‘n’ go rich field scope – this scope gives me up to a 5° true field of view.  The last refractor is an 80mm f/5 achromats – I can use this for video astronomy and as a rich field scope, but in all honesty I have other scopes that I prefer for these same purposes.  This last scope most likely I’ll be moving on.

I do have another refractor, my very first scope, a 50mm Tasco.  I really don’t use it now, but I keep it for sentimental reasons.  I’ve had this little thing for over 30 years now.  I first saw Saturn through it, and did my very first astro sketch using it – of Halley’s Comet!  Most recently I used a good quality Plossl eyepiece with it instead of the poor cheap eyepieces that came with it.  I was stunned by the quality of the image this scope through up!!!  Where previously I only saw the central bright “fan” that surrounds the Trapezium in M42, with this good Plossl eyepiece saw lovely wispy extensions of material, a soft faint glow of body, and even some bulk to M43 and a glow of The Running Man, all previously invisible to my younger eyes under the darker urban skies I had 30 years ago!  I cut my astro teeth with this little scope.  I learned a lot with it despite it being hobbled with poor eyepieces.  The most important thing I learned was:

It does not matter what quality of telescope you have – what is most important is that you have a telescope to go with your curiosity!

Marana:  This is my big aperture travel scope.  A friend of my said to me when they saw me pack it up “Gee Alex, that thing just disappears into its belly button!”.  A very innovative detail of this scope is that it uses active truss elements, not passive.  What’s the difference?  Passive elements means that the member components are locked into place not preloaded with any stress.  Active elements means that the member components are loaded with stresses as they are locked into place.  All the components have a corresponding element that is loaded in an opposite direction, so they all work to balance out the system – something that I’ve picked up from my engineering background.  This way supposedly thinner elements can be used and still produce an optically stable system.  I’ve loaded Marana with a big 1kg eyepiece, and it has maintained perfect collimation.  Takes me just a few minutes to set up, and is silky smooth to use.  And yes, it is a balanced scope – ALL my scopes are balanced, not a brake or clutch in sight, just the occasional counter weight and the same quality of action all the time.  Perfect!

114mm dobbie:  Really this scope belongs to my kids. I made a table top dobbie mount for the little scope that the kids love to use.  But I every now and then commandeer the scope for video astronomy.  It is a modest little scope, with a fast spherical mirror, so best limiting things to low magnification, and it does very well at this.  A fun little scope to use.

So, this is my artillery selection.  Too many scopes?  Probably.  Will I get more?  Well, one James Bond title is “Never say never-again”…  But for now not likely…  I wonder how long the “for now” period will last…