Posts Made By: Alex McConahay

One thing I was surprised to realize when I first started to polar align using the drift method is that your adjustments are likely to be much larger than you anticipate. If you can see drift fairly quickly, you may be as much as three or four eyepiece fields of view off. So, go ahead and crank the adjusters.

In short, the reason that Arcturus still drifts after you adjust is that you need to adjust al LOT more.

As for the focusing of the eyepiece/camera--what you need to do is focus the camera dead on--and then never touch the focusing knob. Put the eyepiece in its tube and move it in and out until it gets focuses. If you cannot move it in far enough, you may need some kind of adapter to move the camera back further. Or if when you do get the eyepiece to focus, there is not enough of it in the tube to hold firm when you tighten the setscrew, you will need an extension to hold the eyepiece out further (my OAG has a three inch extension). You may want to try a Barlow in it first. This sometimes changes how much travel you need in the drawtube.

If you can get it to focus, scribe or mark (or put a "parfocalizing" ring) on the eyepiece so that you know wehre it should be in the tube each time to match your camera.

Alex

Ron,

I listened to a telescope designer explain his job a while back at RTMC.

You don't have it right.

The job is one of choosing parts, having others designed, and then asembling them together. Things that you would never consider part of the telescope must be part of the design. For instance, packaging (as in the size of shipping boxes)is one of the many considerations.

At any rate, many of the optics are produced to order not by the opticians whose name accompanies the scope, but by an optics company whose name you will never hear.

There is a lot more to the story.

Have you ever made a scope yourself?

Alex

Need more details.

Your exposure would depend on what size eyepiece you are using for the projection, the speed of your film, How far the eyepiece is from the focal plane, what part of the moon you want to capture, the clarity of your air, and a few other things.

Set your camera at 1/250, and then take an exposure from there to 1 second, at every click of the shutter speed.

Take notes. Film is cheap. Experience costs.

Alex



Alex

Brad,

If you have Excel, try RATDATA at

http://www.rivastro.org/landers/RATS/intro.htm

It was written to be easy to use, and very flexible. It allows you to enter a five-zone couder mask and up to three sets of readings on a mirror. Either fixed or moving light source. It has three graphs on each run, the full Texereau data table, and a bit of notes to explain itself. (It is informative, even if you choose not to use it as your main program.)

It also contains another spreadsheet that allows you to chck two different sets of data to check astigmatism or the differences between figuring sessions.

And it is a spreadsheet--so you can change it if you don't like it.

Alex

Randy,

My Telrad is just stuck on with the standard two sided tape that comes with the Telrad base.

Alex

Mike,

there is a lot of myth, opinion, and nonsense floating around about aperture masking.

It cuts down the amount of light, everybody concedes that. This may be useful for extremely bright objects.

It may enable you to overcome defects in your mirror. If you shield off a significant portion of your mirror, you shield off some of its defects, and make for a longer F ratio--which is generally easier on the optical system.

It might help on nights of bad seeing--although there is a lot of folklore and disagreement on this. If the size of the hole is smaller than the sixe of the disturbed cell, the theory goes, you will have a more stable view. This has not been my experience.

Anyway. I would not be surprised if you got lots of contradictory responses.

Alex

Ryan,

Assuming you are going out about now--
and will be looking for easy to find things--

In addition to those mentioned elsewhere, you should have a few interesting craters on the moon. Venus. M57, M4, Lagoon, Trifid, and a few other objects in Sagitarius, and M13. Alberio, and Alcor-Mizar.

These are fairly easy to find objects, and will impress your frinds.

Alex

Matthew,

The simplest and most effective is a Hartmann Mask. Get a piece of stiff cardboard, cut so that it will fit over the end of your scope. Cut two matching holes in it, one on either side of the central obstruction. Rig something so that it will stay attached to the end of the scope. (I used embroidery hoops--little rings of wood--glued to the back of the cardboard.)

Place this over the front aperture of an out of focus scope, and you will see two of everything. Bring the scope to focus and you will get one of everything. Remove the mask, and take the picture. (Be sure to remove the mask.....)

Alex

Robert,

I have a Ranger, an 8-24 zoom, and a lightweight photo tripod. The package is as good as it gets for backpacking, and I have done it once. To your package I would add a Barlow (or powermate). Don't worry about the extra diagonal. Do something to the quick-release attachment so the Ranger will not slip around. (THe 1/4-20 screw from a photo tripod will not hold tight enough to keep the Ranger from rotating, so you have to get another points to tie it down to the attachment.) Don't worry about the Ranger--it is tough. I imagine the ST-80 would do well, too, but the optics are not quite the same.

However, I think you should ask yourself a serious question. How good will your stargazing be on a backpacking trip. I reserve my moonless nights for stargazing, and go backpacking other nights. Of course, I have drive-in access to the mountains or desert year round. So, I do not have to combine trips. I do whatever I can to avoid weight on a backpacking trip. If you need to do something, take a good pair of binoculars. They are more useful during the day, and almost as useful at night.

Alex

John
Don't buy any for a year.

Go to a bunch of star parties--you will find plenty of other people's scopes to look through for free.

Borrow a scope (or a series of scopes) from your local club.

Then decide what you want to do.

Then decide which scope is best for you to do it with.

Alex