Posts Made By: Alex McConahay

I finally saw this telescope. It is a 14.25" F6.7 Cassegrain on a Schaeffer Mount. Although it is somewhat dirty, it looks like it is in working order.

Anybody got any ideas of what it is worth?

Alex

If you get a focuser made for an SCT, you can add an adapter at the front the lets it fit in a two inch focuser tube. THen, you can use it for fine focusing after inserting it into a very low profile focuser (like a helical, for example.

SOme warnings why this might not be too wise:

First, so what are you going to do with the old tube? Put the focuser you did not like back on it? Sell it? If you are kkeping it, you gotta get it a focuser.

Second, you will hve all sorts of back focus issues--will the extra focuser get close enough?

THird, the SCT focuser will probably have short focus travel--not good as a general purpose focuser (but, you can make up for this if you have a good low profile focuser to fit it into).

I do use just such an arrangement on my various tubes with my NGF-S/Robofocus. THis allows me to move the focuser from tube to tube as needed.

Alex

Well,

I got there and it was great. The people were wonderful and welcoming. The scopes were mighty innovative. And there were lots of them. I am glad I went.

The rental car and a loaned tent space kept me dry--if not warm. The food was pretty good, and, again, the company was wonderful!

Alex

Maybe its time to move this discussion over to the Laser Forum.....

Alex

Floyd,

There is a whole lot going on in astroimaging that needs to get done, but I think it is best to start on just the most important things, and that would be on getting the best possible light frame with the roundest, smallest star images.

After that, you can worry about the other aspects.

I think Darks is one of the next level of tricks to master. They are relatively easy, and get a lot of bang for the buck.

Darks are necessary to remove a lot of bad things you don't want in the way of systematic noise from the chip.

Flats are not much more complicated, but don't do as much as darks. There's not as much bang for your buck. Flats are necessary to remove bad things that come from your optical system. However, they are not as important as darks (unless you have a real problem system).

Bias frames are relatively unnecessary unless you want to use a set of dark frames at a time or exposure different than what they were taken at.

However, my big piece of advice is to just get the smallest stars possible. And do dark frames. When you have that as well as you can, take some flats and see how much they can help.

Biases will probably not be necessary as long as you take sufficient matched darks.
Alex

Doug,

Of course, you realize that it takes more than Spellcheck?

Each of the terms you used would pass a spellcheck.

Alex

You mean it isn't going to happen?

Shoots my plans.

Alex

A hole saw is nice, but hard to use when you are simply enlarging a hole. (Because you don't have any place to put that central drill bit.)

A router or Roto Zip can work well, too, but has to be pretty much freehand. On the other hand, the hole does not require the greatest precision.

And are you sure the new hole has to be an inch bigger? I thought the hole was already oversized!

One thing to note--how high is the crayford compared to your previous focuser. YOu may need to MOVE the hole (or get into moving the primary). The eyepiece needs to be the same distance away from the primary that it used to be. If you had a focuser that puts the eyepiece three inches away (Typical rack and pinion focuser) and your crayford puts it two (more typical for Crayford), you need to move it one inch up the tube. Which means your hole has to be enlarged to one side more than the other. And the secondary has to move (if there is not enough travel in the support, you may have to move the spider also to achieve this). Moving the primary back may achieve the same thing.....but I believe Starfinder mirror cells are already set about as far back as they can go.

Alex

OK, If I had nothing, and wanted to buy something to get as much as I could for as little as possible, I would get a modified Canon DSLR. You can use it for one shot color. You can control most of the noise with stacking multiple exposures, dark framing, and using it mostly during colder nights. I would guide with a webcam.

Alex

And while we are at it, nobody has yet discussed the difficulty of classifying surface brightness considering that various objects have that brightness in different colors-- and even parts of the spectrum.
Alex