Monday, 10 April 2017
A few years ago I salvaged an old set of SCT forks that was about to be trashed. The RA motor still worked, and its handset still controlled the RA rate. I realised that this old fork mount would be perfect as a video astronomy rig. So I turned my DIY hand to making a wedge to suit.
For my purposes, my immediate design appeared to be fine. With sketching being my primary niche in astro, and at the time using another SCT, I never really paid much attention to the consistent error in alignment that the mount had. No matter how accurately I set the wedge to my latitude, and no matter how much care I took with my rustic alignment, there was a persistent misalignment that saw the object drift out from the FOV.
I recently bought a brand new SCT OTA that I coupled to these old forks. When I coupled the scope to the wedge, I noticed something shocking! Something that I should have been aware of and stopped from occurring when I built the wedge – FLEX!!!
Despite the 30mm thickness of the platform that the mount sits on, long and unsupported cantilevered plywood platform yields to the large mass of the likewise cantilevered mount! A doubly cantilevered system. And now add the heavy mass of the new OTA, and the amount of flex in the platform increased.
This explained the consistent misalignment of the video rig!
But how to fix this?
A pair of aluminium angle brackets placed along the length of the mounting platform.
The mechanical properties offered by the brackets acts much like an RSJ bar (I bar). And with using just four screws to fix the brackets, the bracket/platform arrangement acts just like a laminated system, increasing the rigidity of the system.
Over the weekend I tested the pimped wedge. When I coupled the mount to the wedge I cannot say I noticed any flex in the platform. With the magnification on the scope at 250X, there was only the most minor misalignment noticeable that despite my rough and ready alignment of the wedge kept Jupiter in the FOV for a couple of hours.
Flex problem 95% solved! Any further improvement to the remaining flex will mean rebuilding the whole wedge - something I have not totally discounted as this pine plywood can be improved upon that will further improve rigidity, the new design would reduce the length of the unsupported mounting platform, and the wedge bracing would also be more centred over the tripod. All of these are weak points in the current wedge.
Now for some clear skies for a sketch or two!
Thursday, 6 April 2017
With the sky continuing to be terrible for sketching, it has afforded me time to consider other projects I’ve had in mind for some time.
Well, I have my Frankenstein SCT, but I don’t have anything to store it in out of harm’s way other than a plastic bag – and that just won’t do. My old orange tube C8 came in a trunk, and something that size would be perfect for this “new” instrument.
Purchasing something ready-made though was not ideal as really for a few reasons: either be too large or too small, not support the scope as needed to minimise undue stains on clutches and the OTA, and adapting a ready-made case may be either difficult or implausible due to the materials it is made from.
So the only option is DIY.
The other day I went to my local hardware store to look for some plywood for this project when I noticed a few long sheets of MDF that were being collected for disposal. Their apparent size quickly drew my attention, and with a tape measure I realised that just one of these sheets would be perfect for my project! So, $1 later, I carted off a brilliant find for me.
Ok, the $1 cost of the case is just of the MDF. But this was the only additional expense I had in making the case as every other component I already had at home. The true cost of the case with the other components considered was closer to $60. Other than the MDF, all the other timber elements were scavenged off-cuts from home, and the foam rubber was also off-cuts.
Knocking up the box was easy. What concerned me was making it too easy for little creepy-crawlies to sneak in through the gap between the lid and base, so from a plywood off-cut I fashioned a lip that the lid sits around, and provides a better seal.
Ok, now I have a very drab case made out of MDF large enough to hold the scope. So it won’t be enough just to make a scope case, but the MDF needs to be pimped too.
The real work now commences to fabricate the necessary supporting elements. That was the one problem with the case of my old C8 – the case was just that, an empty box, and the fork and OTA were pretty much left on their own inside the foam filled case.
First thing though was to varnish the entire case inside and out to protect it from shedding its uncoated fibres. The varnishing is also the first part in the pimping process to seal the surface. This allows for the decorative processes to happen.
The OTA is supported as is the fork mount, to minimise undue stain on the clamps and mounting brackets, and to allow for the OTA and fork mount to be supported should the clamps come loose. The distribution of the supports and the OTA also allows for plenty of storage space for bits and pieces. Down the track I can install compartments to hold accessories.
The decoration of the external MDF surface was done taking inspiration from some how-to videos on Youtube on how to achieve a faux-timber appearance on MDF. The decorating was done before the aluminium trim was fitted.
The screws used to fix the trim were selected according to the faces that the case is to sit on, namely the bottom face, and the back face with the hinge (the case is stored standing on this hinge face). Those faces not taking the weight of the case have pan-head screws that sit proud above the trim. Those two faces which are used to sit the case on, the screws are countersunk below the trim.
Even the handles have special consideration. As MDF is not the hardest material, special measures need be taken to reinforce the areas around the fixing screws. The top pair of screws bite into the hardwood plywood lip. The bottom pair of screws are machine screws that back onto a pair of massive washers to distribute the load of the case over a very large area, and thereby avoid the risk of screws pulling out.
I am very happy with the way this case has turned out. A couple of friends have commented that they couldn’t believe that this was MDF! There are plenty of hollows which can be used to store accessories, such as a diagonal and finder. I can add compartments to the case as my experience with the case grows. Velcro straps could also be used to hold some of the accessories.
If you’ve been considering scope case options, I hope this project of mine has given you some ideas on what can be done. My project is certainly not the be all and end all with scope cases. It is just my take with the materials I had at hand, the ideas of what I wanted, and the inspiration that came to me.
Saturday, 11 March 2017
I recently purchased a new SCT optical tube assembly to replace my lovely orange tube C8 that I retired from action. I’m pleased to say that the Old Girl has found a new home with a collector who will look after her.
So, this new SCT needs a mount.
I purchased this scope knowing that I have a German Equatorial Mount (GEM) that can take it. However, GEM mounts do not place the eyepiece at the most convenient location. There is also the meridian swap in order to keep the motor drive loaded appropriately without undue stain. Yet a fork mount has a much more limited range of eyepiece placement, and is not affected by the strain of meridian shift.
So, I’ve got a new OTA, but which set of forks?
One reason that I bought this particular OTA is that it has screws on it that would seem to correspond with the coupling holes on the fork mounting plates. I have an old set of forks from the same brand as the OTA, so why not look at seeing if I could couple this OTA with these old forks? I’ve been using these old forks as my video astronomy rig, having made a platform that spanned the forks.
Alas at first glance not. The OTA appeared to be wider in diameter than the span of the forks and the coupling holes did not match. The latter was by just 1mm, but enough for the screws not the fit.
So begins the search for a set of forks to match, and an interesting saga of near misses, useless sources of information, wonderful people willing to help, and pigheaded, devil may care, try it and see try to fix it attempt.
So, after the question asking, frustrations, and fruitless searching, the promise of finally a clear sky and the chance of finally doing a sketch of the Moon, I decided to have another go at fitting the OTA to the old forks. I mean, how hard could it be, right? So after dinner, I disappeared into my workroom and let the Devil take over!
I decided to take the arms off the mount, modify the holes to allow the screws to fit the OTA. This was very quick and easy to do as it was just a minimal amount of material that I had to adjust. To my joy, the third hole in the coupling plate was a perfect match to the corresponding hole on the OTA. Bonus! This allowed me to first couple the tynes to the OTA with this third, leaving the two other holes easier to deal with.
Once both tynes were fitted, I lowered the OTA onto the mount. I expected there to be a gap between the mount and the tyne attachment points, and had thought of a way to deal with it. But to my surprise, there was no gap! It was a perfect match! Perfect!
Finally I have a brand new SCT OTA with the convenience of the fork mount that I preferred. I am overjoyed that I have been able to once again re-purpose the old forks. The wedge I made some time ago and my kids decorated it, and the tripod is a surveyors’ tripod. So my “new” scope is a real Frankenstein, made up of old and new, DIY and re-purposed. And it all works brilliantly 😎
Now, to get scope time once again. I’m hoping that the sky finally clears this weekend. The forecast is promising. I’m now all dressed up, and nowhere to go until the clouds clear. Oh, well, that’s how things go with astro…
Sunday, 22 January 2017
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
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…
Friday, 9 December 2016
John Steinbeck wrote “The best laid plans o’ mice an’ men, go oft awry”.
One of Murphy’s Laws states that “If something can go wrong, then it will”.
So it seemed that this was to be the eventuality of a perfect start to my night up in the Blue Mountains, when mist, fog and clouds started rolling in in turn after sunset.
Four mates and I arrived at sunset at Mt Blackheath Lookout. There’s a take-off ramp for hang gliders and paragliders, and a couple a paragliders were taking advantage of the last of the day’s thermal currents with some last minute flying. I always find it exhilarating how they pull on the ropes, the blade obediently puffs up, and after a little run up the glider and pilot are lifted into the quiet sky. And to see a brace of gliders’ silhouette against the orange setting sun, and floating over a green valley, gorgeous.
When we arrived, the wind was firm and from the west. I thought that the easterly change that was forecast would have no chance against it. No sooner did the sun set that there was a sudden change in wind direction, and the warm westerly was sent packing by a roaring easterly. I have to say that the change was spectacular.
Unfortunately the change meant that the clear sky would cloud out soon – Easterly winds come from the coast, so they are moisture laden, and when they encounter the mountain range, clouds form as the moist air climbs up the mountain range. The moisture content was very significant as mist soon surrounded us, meaning that if I started a sketch, the paper would quickly absorb the moisture, regardless of any measures I had taken to prevent this from happening.
The three hours of clear dark sky that we had was invaluable though. I had taken two telescopes for the purpose of sketching the Large Magellanic Cloud (LMC). An 80mm f/5 achromat, and a 100mm f/5 achromat. With the LMC being so large (over 12° in its largest dimension), I was not sure which would be the best scope to use. The 80mm gives me a 6° true field of view with the appropriate eyepiece. But the image is not as detailed as that provided by the 100mm refractor, despite the larger scope giving a smaller true field of view of 5°.
So the dilemma for me was which instrument. Large field of view and less detailed, or smaller field of view and more detailed. So without the pressure of having to produce an actual piece (I made the decision that this night was not the appropriate one for a sketch), I was able to take my time with each telescope in turn to find out what each actually has to offer. Which of the two instruments I would settle on using.
So, I settled on the 100mm. The image it gives is just so much more appealing, that despite the additional detail, it just shows so much more of the LMC that I feel compelled to lay down on paper everything it has to offer, and not settle for less, even if it means an “easier” time for me.
Ok, I now have the telescope. But this still left the task of how to undertake such a large piece. I have a new extra large easel which I haven’t initiated as yet, nor any experience with sketching on such a large sheet. I described the new easel in my previous blog post.
The next day at home an idea came to me. The inspiration coming from the Old Masters who undertook a series of study works before tackling the actual piece. This approach allows for many different technical and composition issues to be sorted. Very often, the work behind these study works is greater than the time and effort involved in the final work.
Undertaking a study piece of the LMC would do several things for me:
· Give me some experience on handling the easel
· Give me a sense of scale in developing the sketch
· Become more familiar with the LMC, and identify certain details
· Give me a notion of how to produce a piece that conveys the vitality of what I see through the eyepiece. My examination of the LMC on the Saturday night gave me a fabulous view of its brilliance and expanse – I need to somehow convey this without making the sketch flat and underwhelming.
Another problem next presented itself. Finding photographs of the LMC is easy. Manipulating those photos so they more closely resembled how I saw the LMC is easy enough to do too. But how to reproduce the smaller field of view of the scope compared to the size of the galaxy, and so give me an idea of handling the scope and doing the sketch? The solution was surprisingly very low tech. A sheet of dark card with a hole cut out of it, and scaling the image of the LMC on the computer screen to match that seen though the scope. As the sketch develops, I move the background image and/or the mask to allow me to work on other sections of the LMC as I go.
I’ve since been working on a series of study sketches. This has been a good journey to undertake. It has presented me with several technical aspects I had not anticipated, and allowed me to consider ways to deal with them. All that’s left now is to tackle the LMC out in the field.
The main thing I want to convey is not to expect to undertake a sketch out in the field without having done some practice in the cool light of day. It is invaluable to become familiar with your media, how to manipulate it, what different brush strokes do, and how different objects present different challenges and how to develop a technique that best works for you. No athlete takes to the field without practice/training. Surgeons do not undertake complex surgery without gaining experience. Artists are no different when it comes to developing their technique and familiarity with their tools and media. Don’t think that practice is cheating. The only cheating that happens is to yourself as you won’t be producing work to your fullest potential.
Clear skies and sharp pencils,
Friday, 25 November 2016
I have recently been commissioned to do a sketch of a very particular object, the Large Magellanic Cloud. Both an honour to be commissioned by a professional astronomer for this piece, and also terrifying by the very nature of the beast I’ve been asked to chase down.
Every now and then, I find that a particular object I am considering to sketch, some preparation needs to be made. Some of these preparations come from previous experiences and how they relate to my style of sketching. As an example of one aspect of my sketching style is how I don’t use a “field of view circle”, or as I affectionately call it “The circle of Death”. I tend to develop the scale of an object pretty much on the fly, letting the natural action of my wrist and fingers begin the scaling process and the rest takes care of itself. And to this, an A4 sheet of paper is usually plenty big enough.
There are a few objects however that I recognise as being so large that an A4 sheet wouldn’t be sufficient to accommodate them. For these I sought out an A3 pad of black paper in order to sketch them. The Orion Nebula is one example where I deliberately used this larger sheet size. As too the sketch of the Andromeda Galaxy.
This last one however brought to my mind that there are even some objects that even A3 is not big enough. For me, the finished sketch of M31 is a little more “constricted” than I would have preferred. If I had started the sketch with a slightly tighter wrist, and made the initial brush strokes tighter, then the final sketch would have been less constricted. But the difficulty is anticipating the ultimate amount of expansiveness that M31 is to reveal. So for the Andromeda Galaxy, I feel I still did pretty good, despite my own critique.
Now, the LMC is a different beast altogether.
While M31 has a maximum angular dimension of some 3°, the largest dimension angular dimension of the LMC is some 10.5°! Flaming enormous! Knowing my own style of sketching, I can see that even with an A3 sheet I would struggle to fit the LMC.
So, I need to build a larger easel to accommodate a larger sheet as the one I currently have can take an A3 sheet and no larger.
It is also not just a simple matter of scaling up what I currently have. I also need to consider the experiences that I’ve had with sketching in the night air, and work out some ways in which to counter some of the problems that can be encountered.
One thing that is seen through the eyepiece during an extended examination of an object is the apparent rotation of the object in the field of view as the objects transits through the sky. So to work with this is to rotate the sheet.
Another difficulty that can arise comes from dew. While the shielding that the Coreflute wrap that I have over my current easel works very well most nights, it is those occasional nights of excessive humidity that overwhelms the shielding and the paper warps as it absorbs excessive moisture, and the texture of the paper is also altered to the point that it becomes soggy and impossible to continue working on without causing damage to sketch that’s been laid down.
Even how to illuminate the large sheet needs consideration.
So, time to work on Sketch Easel Mk II
I decided to utilize the same clamp mechanism to hold on to the sheet. It is simple and effective, and with a little thought it can be made to allow for a broad rotation range of the sheet. To help control any possible flapping from gusts of wind, I devised a few clips made from wire that I bent into shape. These clips gently hold the paper down and their long reach allows them easily reach the paper even when it is tilted for rotation purposes.
While the shielding I’ve made has more overhang than the first Easel, if the night happens to be a humid one, particularly with the longer amount of time that this piece will take me, I’ve had to come up with some system by which to help control dew soaking into the paper.
I’ve long thought of different way that this could be achieved. Heating the paper is one way, but the power requirements of such a heater is large and complex to design and fabricate.
I then thought about the way we control dew with our scopes – with the movement of air. Dew does not form on a surface that has a constant stream of air flowing over it. So I came up with a battery of fans to blow gently down the face of the page. I’ve used two fans rated at 12V, installed in series so to reduce the airflow to a gentle blow, and not have the easel become airbourne.
Of course, this dew mitigation method for paper is purely experimental, though not without pedigree. Time will tell how effective it is.
The lighting aspect I’ve addressed by having additional anchor points for the dual lamp that currently use. I’ll also have some extra little reds lights in my pocket and tape in case I find I need some addition illumination.
Now that the Easel is done, I just need some eyepiece time with the Large Magellanic Cloud…