Saturday, March 31, 2007

Some actual observing...

Mostly the weather has been bad and I've been really busy, so I haven't had much time to observe.

However yesterday afternoon the moon was out in the afternoon sky, and could be seen in my home office window. I was able to get a nice view without ever leaving my chair care of my 15x70 binoculars. This morning as I got up before dawn to go to Natz* Jupiter was shining high in the south. Maybe one day this week I will get up to get a good look, as I didn't have a chance to get the binoculars out.

*Natz, is the jewish morning prayers done literally at dawn (IE The first possible moment you can) . I go because there won't be a long sermon to listen to.

Thursday, March 29, 2007

Tools needed

So I figure to build these scopes I will need these power tools:
  • Plunge Router (with some bits and jigs)
  • Miter saw. Specifically I will need to make an angle of 32° (as I live 32° north)
  • Hand drill
  • Jig saw
(Tools I have)

Non power tools that I may need:
  • Goggles (for eye protection)
  • Sandpaper
  • Clamps (a bunch)
  • hammer, screwdrivers etc
  • Tape Measure
All of this will also put me in a good position to build a bunch of bookshelves.

As for router bits, I think a Dado bit and something to let me cut circles, the dado may work there, a small quarter round might be helpful too.

I'm going to see if my jigsaw can cut on an angle with a jig. Cutting at 30° should be good enough. Or I can see if a neighbor has a miter saw that can do 32°

Tuesday, March 27, 2007

Two scopes

So for right now I'm working on the 4.5" starter scope, after that I plan to make a larger (10-12") scope. The question is really how big a scope can I make that will still fit in the trunk of my car. It will be some time until I can afford the optics etc for this scope, so at this point its more a theoretical thing. For now I am planning on taking a tape measure to the trunk of the car.

Sunday, March 25, 2007

Building an equitorial mount (Some Math)

I want to build a simple equatorial mount, which is to say a mount that can be aimed at the North Celestial Pole, and then turn at the rate of 1 turn per sidereal day. Or 1 turn in 1436.06 minutes. This will match the rate at which the stars move across the sky.

To do this I will need a main gear which will be a wood disk cut on a router of radius R.
This will be driven by a threaded rod with 20 turns per inch turning at 1 rpm. This will move the disk at the rate of 1/2oth of an inch per minute. As such the circumference of the drive wheel must be (1436.06 minutes * 1/20 inches /minute) which is 71.8 inches.

Thus the radius (R) of the drive wheel should be 11.4278 Inches. I expect 11.45 or so will be about as close as I can machine the thing, this should be close enough for visual use and for astrophotoraphy as long as the exposures are short (say 10-15 minutes max).

In need of tools

I found a few episodes of "The New Yankee Workshop", and have been watching them to learn something about woodworking. Last night I saw the router 101 episodes (as well as the lathe episode). It looks like plunge router and a few jigs will get me a long way to where I want to go.

To build various scope parts I will need a circle jig, which he showed how to make, and it looks quite doable.

Starting Small

So I think I am going to start by building a 4.5" F8 small dob. The primary & Secondary will cost me about $53 (USD) with shipping plus any customs. I sent an email to the customs service to see how much that will be.

The next thing to decide is do I want to make it a solid sonotube or some sort of truss travel scope. I am looking around talpiot for sonotube, and will try to see how much it goes for. From there I can decide if I want to lug the scope around in 1 piece or not. I'm thinking with this one a solid tube makes sense.

Thursday, March 22, 2007

Finding optics

I have found these 3 companies that sell telescope mirrors on the low end.

Meridian has a 4.25" F8 mirror for about $32, which would be about $40 with shipping. This also includes a secondary mirror. It would make a decent long tube for a narrow field of view.

A 6" F5 mirror seems to be about $80. This would make a nice wide field scope. including a spider and mirror cell it would run me about $150.

If I want to go larger then I found a 12" F4.5 with secondary for about $399. It would need a mirror cell and a bunch of other stuff. This is a plan for the future.

I think for now the 6" rich field scope makes the most sense.

Wednesday, March 21, 2007

pocket microscope

My dad sent me two 30x pocket microscopes. They are quite fun. I have one in the office today and have been showing it off to pretty much everyone. This thing is pretty simple. It has a small flashlight bulb to illuminate the target and a simple set of optics, which I assume are plastic. You don't need slides, just press the front end against what you want to look at and adjust the focus knob.

30x is enough to see quite a bit of detail without.

Things worth looking at (so far).
  • Coins
  • Bank notes
  • Fabric
  • leather (tooled leather even more so)
  • LCD screens.
  • A dish scrubby/sponge
  • A photo (not very useful, but interesting)
I have 2 of them, I'm going to at some point give one to each kid and give them a scavenger hunt where they have to find various types of features under the microscope.

This is pretty cool for a toy that costs about $9 (USD), plus 2 AA batteries.

rebuilding a telescope

So I have this telescope. Its a meade short tube reflector. Which is to say that it has a spherical primary (bad) which is probably about F4 or F4.5. It also had a bad finder which is now broken and a crappy focuser and mount. So I'm going to rebuild it a piece at a time, until I have a scope that I like. First step is a new finder scope and a crayford focuser. The new finder is a 9x50 from Orion and the focuser is from the same source.

Next step is to rebuild the mount into something better for this there are 3 options:

  1. A standard dob. maybe a travel dob. Basic alt/az platform scope, nothing fancy but will be easy to build.
  2. A Equatorial mount. I have seen plans for some that use a wood disk for a drive wheel. My cousin in Hod Hasharon is a wood worker with a lathe so if he can help me this would be an option. This would require a motor that can be adjusted to allow it to track the sky. The major advantage here is that i could use this for piggyback photgraphy.
  3. A Trackball. This would involve mounting the mirror in a sphere such that the scope could turn any way. It would therefore be possible to have a polar drive motor to track the sky, but it probably would not be possible to balance it to do photography.
If I go with 1 or 2 I may get a palm pilot or the like and hook up a mouse or two to act as an encoder to be a setting circle. This would allow me to know exactly where my scope is pointing and allow me to find object quite easily. On the other hand I'm not sure I want all that complexity, and of course there is the trunk space issue (my car is quite small)

Tuesday, March 20, 2007

Photoraphy and astronomy blog

This blog is designed to be my photography and astronomy blog. Different from my livejournal. In terms of astronomy I'm mostly using a pair of Celestron Skymaster 15x70 binoculars. And trying to rebuild a meade short tube reflector into something decent over time.

In terms of photography I'm using a Pentax K-1000 (35mm), a Rolleiflex TLR 2.8E (120 format) and soon a Sinar F-1 view camera. I am almost exclusively shooting Film, mostly slide film (Fuji Provia and Velvia). I plan to start doing some black and white soon so I can develop at home.

Photography targets are mostly landscapes and the night sky.