Posts Made By: James McSheehy

Federal Reserve Chairman Ben Bernanke rides off into the sunset after saving the world, getting Obama reelected (with help from the GOP), and making TBTF an institution. How can we summarize this man's accomplishments from the perspective of average Americans?

Let's look at employment growth relative to growth in the Fed's balance sheet (i.e. QE):

http://tinyurl.com/myy3vo6

And here's the good news on housing starts:

http://tinyurl.com/kwlg2bz

Great job Mr. Bernanke -- thanks a pant load!

I use one on my 5D and it's a nicely-made piece of gear. The interior is threaded, but the grooves have the same shiny black anodizing as the outside, so I may have to attack it with some Krylon ultra-flat black paint.

Canon 5D

Pros:

Full frame sensor uses standard lenses without corrections for FOV or FL

Has the same large pixels as the 300D. Bigger pixels = lower noise in CMOS sensors

Can be modified with accessory filters

Cons:

Cost

It's big and heavy

Wide sensor shows vignetting

Doesn't use the latest image processing chips like the 40D

You make a good point. I know several amateurs who like to "evangelize" the hobby and volunteer for public viewing events sponsored by our club. We get a broad cross section of visitors to these events and invariably some of them ask rather specific questions about the value of equipment and where we keep our stuff. Innocent questions? Probably, but who knows these days?

IMO it's best to keep a low profile. I don't tell people outside of close friends and family about my astro gear and that includes neighbors and delivery drivers.

Bill,

I went that route 15 years ago (Enco lathe & manual mill) and found that the results were more instructional than useful. Other than some simple turned parts it is not possible to do precision, repeatable metal work with these low-cost machines. And buying the machine itself is just the start. Even minimal tooling for a $499 lathe can cost as much as the machine. IMO you would be better off taking your ideas to a real machine shop. It will certainly cost you less and the quality of the parts will be far better.

If that isn't possible or practical, look for used machines that include the tooling and spares. Also consider that basement stairs and 1600-pound chunks of cast iron are not made for each other. 8)

There is nothing wrong with owning a drill press, hand tools, band saw, etc., as these can be used for many other tasks. But if you need to turn precision threads for a custom eyepiece barrel, that Grizzly mini-lathe or Shop Smith 3-in-1 wiz-bang is probably not going to do a very good job of it.

The issue with these larger achromats is tube length. That Goto lens sold at a nice price, but think about what a three-meter focal length actually means in terms of the mount and eyepiece locations.

Folding the path is the obvious answer to get one of these lenses into an OTA normal people might want to use. Two folding mirrors at 92% reflectivity clips the 10" lens down to 8.5"aperture. IIRC the old ATM books even had configurations using three mirrors with a fixed eyepiece position.

When all is said and done you may be better off with that 6" APO...

Over the years many 8" MCTs (Intes-micro, AP, TEC) and one SCT (Takahashi) have been available that meet your criteria. Expect to pay $4K to $15K for the view.

Good, fast, cheap, pick any two.

Some observations regarding this scope:

1) When I first saw the photo, I assumed it was made by Intes-Micro. The design of the front cell looks exactly like the perforated cover used by I-M to allow airflow into the tube.

2) I own an f/4 MNT and at that focal ratio it's barely possible to reach up into the tube to adjust the secondary for collimation. At f/5.3 reaching the secondary would be almost impossible. Collimation of this scope is going to be "interesting" unless the secondary rotation is spot-on.

3) Focal ratios less than f/6 have lots of higher-order spherical aberration unless a surface is made aspherical to minimize it. An all spherical design (implied at this price) would not perform very well compared to other scopes with better figured optics.

Good luck on your project. I'm finishing a small roll off that was started in March 2007 and made my share of mistakes along the way. For what it's worth, here is some advice.

ELECTRICAL

Take the advice others gave and use PVC conduit for the electrical runs. It costs a bit more than just burying UF cable but IMO the advantages outweigh the extra expense. Electrical code requires separation between the feeder lines and the data and low voltage wires. They cannot be run in the same conduit or raceway, and inside the structure AC wires running in walls need a 2" minimum separation from the others. A good source for NEC related info is the search feature at:

http://tinyurl.com/5ayyho

If you have elaborate ($$$) gear in your plans, I'd recommend you consult with an experienced electrician to make sure your structure's grounds and bonding meet the code and will protect the equipment if lightning strikes nearby. Consider buying a UPS for the observatory with a built-in isolation transformer.

PIER

The pier should be designed so that freezing earth can't heave and push it upwards. That means the hole for the pier needs to taper outwards as you go deeper. Keep the reinforcing steel rebar inside the cement -- anything sticking into the ground will rust away in a few years. Remember to isolate the pier from the slab if you decide to go that route for the floor.

I used a wood-deck approach to my foundation and floor system and here are a couple of pictures that show the initial work. The concrete portion of the pier is mostly below grade and consists of a reinforced block about 3'x 4'x 6', with a small tapered section poking out above ground level. This is the base for a steel pier that my mount sits on. The observatory structure is build like a deck with 4x4 legs sitting on six concrete footers poured at grade. In theory, the whole building (minus the pier) could be moved at some later date.

Mirrors eventually have to be recoated, and that means anything you put on, paint, ink, glue, needs to be cleaned off. I would hesitate putting anything "permanent" on a mirror.