By popular demand, drawings for the iOptron MiniTower Equatorial Wedge project I completed in 2010 August-September (see old blog posts: base, top, side, knobs)
Here's how the wedge looks like. It consists of a fixed plate that attaches to the tripod, two fixed side plates that bolt to the bottom plate, and a moving plate that tilts about 10 degrees. The wedge is designed so that the centre of gravity of the MiniTower is positioned straight over the middle of the tripod.
The extra 6mm hole in the side-plates is for an M6 threaded rod through the mount which should provide precise azimuth-adjustment. I did not complete this feature (for example a rotating nut in the fixed plate would be needed).
About 2 hours more work on the triangular base for the telescope dobson-mount.
Here I have added one more profile in the middle of the triangle which holds an 11mm diameter steel pin, around which the upper platform will rotate. Roughly 30mm high acetal plastic cylinders at the midpoints of the triangle-sides support the upper platform and will hopefully provide the right amount of friction. Too much and it will be hard to move the telescope, too little and it won't stay aimed at a particular target.
This is the upper platform, a piece of oak-board. The steel pin fits in a brass-fitting which is bolted to the center of the board.
This is how the two pieces fit together (upside down). The oak-board will rotate around the steel pin while resting on the three acetal posts.
I made this triangular base for the telescope Dobson-mount we are building. It has three ca 640mm long 25mm-by-25mm aluminium profiles, cut at a 30-degree angle to make an equilateral triangle. It is held together with tapered pieces of 100mm wide 10mm thick aluminium bar that attach to the T-groove of the profile with M6 screws. Each corner has an adjustable foot.
The mount that goes on top of this triangle is also from 25-25 alu-profile:
Stay tuned for hopefully some lunar and/or planetary images when this project is done.
Some intense aurora borealis (northern lights) visible last night around 23:00. I stayed out watching and photographing until about 00:30 but it seemed the intensity was fading continuously while dark clouds also appeared.
As usual the camera sees a much more intense green, while the red is almost completely invisible to the naked eye (at least for me).
Here is a time-lapse video of all frames from last night.
Before shooting auroras, I captured 60s exposures for this milky way time-lapse:
The bright star that starts out about mid-height to the left of the middle is Deneb, the brightest star in the constellation Cygnus. As it swings down and to the right the Andromeda galaxy becomes visible in the top left corner towards the end of the video.
Some nice northern lights (aurora borealis) appeared just as I was going to pack away by tripod and camera after shooting another fixed-tripod milky-way time-lapse.
So no packing away and instead Aurora Borealis shooting for another three hours. These are 20s exposures through a 17mm/F4 lens on a Canon 500D at iso3200. Fixed tripod.
The time-lapse video is 340 frames shot from around midnight to 3am on Wednesday 28th September 2011 looking north from Oravainen, Finland. As with all photography the camera sees things differently from the eye. The lights look brighter and more yellow on the camera, and the red hues visible on camera are very faint or nonexistent by eye.
Photo equipment was fairly simple: I hung a plastic bag containing stones on the tripod to stabilize it in the wind. Timing and shooting with an intervalometer. Shoe-driers taped to the lens with masking-tape worked as improvised dew-heaters. I'm using a Canon ACK-E5 powersupply so I don't have to change batteries constantly.
Time-lapse movie was compiled by first resizing images (JPEGs straight from the camera, no modifications) with mogrify -resize 1280 *.JPG
and then compiled into a movie with mencoder -nosound mf://*.JPG -mf w=1280:h=853:type=jpg:fps=8 -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=2160000:v4mv -o movie.avi
Update: I also had my older 20D camera with me, and a 50/1.4 lens. No tripod, just camera placed on a wooden board pointed towards the sky. No dew problems despite no dew-heater. Here is a time-lapse of ca 400 frames exposed for 3 s. This is much darker than the first video, and doesn't bring out as much red/yellow color. This is probably closer to how it looks to the naked eye.
Up north away from the civilisation light pollution, it's easy to see the milky way with the naked eye. Here's a short time-lapse of 60s exposures with the camera on a fixed tripod (I didn't drag my tracking-mount with me this time).
Without a dew-heater it didn't take long for the lens to fog up (I didn't bring my dew-heaters either!).
I turned these knobs from 40mm stock on a manual lathe during the week, and JI cnc-milled them to shape today.
There's still one bit missing from the wedge: the fine-adjustment piece for the azimuth-angle during polar alignment. I'll try to make it on the lathe next, and then everything should be ready for anodizing.
CNC machined two side-plates for the equatorial wedge today. Next up are some M10 and M6 knobs on the lathe, and the fine-adjustment for azimuth. Then all parts should be polished and anodized.
