My Sketch Pad Rig
Thought I'd show the sketch pad rig I use and made for myself.
It came from a desperate need to have something made quickly for an upcoming dark sky trip, and that holding the sketch pad in my hands was not the way to go when up a ladder. Yet it was the very ladder that I used that proved the source of inspiration and design.
Taking after my mum and dad, I am not the tallest fellow in the world. And even though I built my 17.5" Karee dob to have the zenith height of the eyepiece as low as possible to the ground, I still need a single step up to reach the eyepiece at zenith.
Ok, I now need a ladder - but which one? I had to find one that satisfied a tight set of parameters:
* Stable & sure footed
* Easy of a novice to negotiate in the dark and allow them to hold onto so that they didn't first reach for the scope, especially little kids
Might seem not a broad set of criteria, but most ladders are not suitable. Either too tall, the rungs too narrow, set too steep, even too many steps or too few. Three steps would be idea. I had an old step ladder at home that satisfied the second point of my needs, and had just three, but in the dark it was too small to be stable. Then a chance visit to the local hardware store, and BINGO! There was the perfect step ladder! Three steps that were deep and wide, tall frame that allowed for easy gripping, and has a collapsible try at the top that I can use to hold the odd bit of gear. Problem solved!
The sketch pad rig
With the step ladder issue solved, a desperate need to knock up a rig to hold my sketch pad became apparent. The tall frame of the step ladder held the clue to how to design it. All I had to do was find or design a hook for the clip board I was to use to hook over the ladder's frame. Another trip to the hardware store and I found the perfect broad hook! How lucky is that!!!
Another difficulty popped up when I thought about the sketch pads I use and could use. I had A4 pads, which the clip board I had was designed for, and of course it could also hold smaller pads. But, it couldn't take a larger pad, say of A3 size. So the clip board was discarded, and a piece of perspex (Plexiglass) that was scrap from another project was the perfect size for A3 paper, and a little larger. It was also thick enough to allow the hook to be screwed into it without having the fixing screws cause interference. If I had to make this rig again, I would use plywood instead of perspex, as the perspex is very reflective and difficult to paint black. I only used perspex in this instance as it was the material I had at hand at the time as I didn't have any plywood.
The "clip" that holds the paper securely I made myself from a timber off-cut, a couple of machine screws and a couple of wingnuts. This mechanism allows me to not only accommodate any thickness of paper pad, but I can also regulate the squeezing pressure it applies so I can use either a single sheet of paper, or a really heavy and bulky A3 pad with equal easy and security - something that an off the shelf clipboard just doesn't allow.
Then the eternal problem that is the bane of amateur astronomers reared its ugly head - DEW. A heating element for the sketch pad was out of the question as the thickness alone of the sketch pads can vary, would take ages to heat the paper pad, and would just complicate the entire set up, which I wanted to keep as simple as possible. So, after some thinking about how dew forms, I came up with a simple solution. Dew forms by falling. So all I needed to do was design a shelter for the paper. And the local council elections gave me the solution for the material to use - black Coreflute® sheet. As I am right handed, the left side of the shelter could come straight down the side of the sketch rig. Overhanging element I extended out further than the edge of the rig so that I wasn't hindered by the shelter, and the overhang also provided a little more protection from dew than if I just trimmed off the Coreflute® flush with the sketch rig.
The final design allows me to hook the rig not only onto my step ladder, but also just about any chair should I need the rig to be set down lower than the ladder will allow for.
There was just one element left to allow for - lighting. That proved very easy to deal with. Firstly, the lighting should not come from the direction that one is looking from. Having the light come from where you are standing, square to the paper, you will get the glare from the reflection of the light off the paper come straight back at you, reducing contrast, washing out faint details, and hindering your precious night vision. Having the incident light come from the side, the reflection off the page is sent off to the other side of the rig, and with very little coming up into one's eyes.
At first I used a bulldog clip to clamp the red light torch I first used onto the side of the rig's shelter. Today I use a dual light gooseneck lamp with red LEDs that has its own clip that I mount into a notch I cut into the shelter. I can then move the gooseneck lights freely at will to any part and direction onto the page.
So there you have it. Inspiration, good fortune, stuff that's lying about the place, and a council election all serving to create the sketch rig that I use.
(25th October, 2015)
(20th April, 2015)
Article: Cooling of Newtonian Opitcs - an insight
Note that the hair drier solution only has intermittent effect as dew will form again requiring the use of the drier once again.
If you would like more specific information regarding your own particular requirements, please follow this link to the discussion thread of this article in the Australian amateur astronomy Ice In Space:
Article: Cooling of Newtonian Optics, Ice In Space
There you will find people with specific skills within visual and imaging who would be well placed to assist. This article is intended as a collection of the current ideas of best practice, and a starting point for understanding the principles behind the cooling of optics. It is beyond its scope to offer singular information for any one instrument. That can be addressed at the link above.