Posts Made By: Alex McConahay

Paul,

Having lurked over there a few times, I would disagree. Potshots are frowned upon, and long two part diatribes are the accepted way to heaven over there.

It's not like over here

Alex

Mark,

Color correction is the science of making all colors focus at the same place. In any glass, one color will focus at a slightly different place than another. Therefore, one side will be fringed with violet, and the other will look yellow (if I recall correctly). (The main object in the image also is muddied by this phenomenom, but it does not show as much because there are too many colors in the middle.)So, the telescope makers put together different combinations of lenses and types of glass so that all three colors are "corrected" to focus at the same place.

A lens showing zero color will show no such false color. But I have am not familiar with the expression "8 times color correction."

(As usual on the forums--where one does not know exactly where the other guy is coming from--please forgive me if I have explained the obvious to you. I am sure the explanation will help some lurker if not you.

Alex

Should you recoat or clean?

That is hard to say without looking. But generally, dust and such would not affect the view all that much. Are there any obvious discolorations, flakes, or other anomolies? You have to weigh the hazards of cleaning against the amount of dust and such. Minimize cleaning, but don't be afraid of it.

Recoating? If you hold the mirror up, can you see lots of light through it? (then recoat) Is it regular and even all the way across? (then don't recoat) From the front, are there any obvious discolorations of the coatings? (then recoat--or maybe just clean first)

If you have scattered light, it is more likely the result of internal reflections in the tube and other places in the lightpath.

As for bluer--that sounds more like the result of an eyepiece. Did you use the same eypieces in your comparisons?

Alex

Contact a few local photographers or graphic artists. They will know where you can find a professional photo lab in the area. THen you talk to these people. They probably have done astrophotos. If not, they can be taught. Bring in samples of what you wantm, and show them.

Alex

Hi all,

Thank you all for your wonderful suggestions--and those of you who have not applied, pitch in what you can.

A couple of individual comments:

I did not realize the depth of the need. Several of you are expressing real gratitude for someone even asking. I say to you--don't get desperate. Listen to the fellows who spoke of just sitting out under the stars. If the telescope does not work just as you thought it might, you are still outdoors under the great dark. This is not a competitive sport, its just a hobby where we are out having fun. Sometimes experience comes only with, well, experience.

Kathy, I think it was, said she wanted to move nearby so she could call me regularly and get help with the observing--Well Kathy, if you live in Southern California, you can. If you don't, just remember, there are lots of other somebody just like me, or even better probably, in your local astronomy club. Just do a search at the Sky and Tel website for local astro clubs. (Where are you anyway?) ANd you always have astromart and your sounding board here.

And Backyard Astronomer's Guide idea is brilliant. You are right. That is one of my favorite books, and a great way to organize what there is to know.

Thanks all, and keep your ideas coming.

Alex

Good timing. It looks like you caught the ovum just before conception.

Alex

Jon gives good advice.

But you may actually want to go the other way in your eyepiece shopping. The ETX already has a long focal length, and therefore lots of magnification and relatively narrow field of view.

A barlow would give you magnification, and narrower field of view.

Consider any of the wide range of 40 mm eyepieces to expand your Field of view.

Incidentally, if you are into solar system objects, disregard what I just said.

When buying an eyepiece set, you should have 1)one that gets you in the range of 40-70 power, 2) an eyepiece that will get you about 250 power when barlowed (or, in a scope less than five inches, one that will get you about 50 power per inch of scope aperture when barlowed), and 3) a wide field/low magnification eyepeice. (Assuming your interests are general observing, and not focusing on double splitting, or solaar system observing, and whether I buy the wide field or the higher mag eyepiece second would depend on whether I wanted to observe solar system (buy higher mag) or deep space more (buy wide field).

Secondly, choose your eyepieces such that, when used with a Barlow, you actually get six eyepeices, and do not duplicate eyepiece length. (For instance, if you have a 26, and a two power Barlow, do not get a 12 or 13. (You would already have a 13 if you use the 26 with the Barlow).

Alex

You can't reach between the arms of the spider and get all the way down there? Remember--you don't have to reach it, just the end of the wrench.

NOw, not being familiar with that particular scope, I would say it is easier to remove and replace the primary cell--mirror and all, than the secondary. Before moving anything, though, be sure to mark which way the cell currently sets. (It probably has three or four holes holding it in, just make sure you mark the orientation of the cell so you can put it in the same way you took it out.) If you do so, you should be lucky, and it will need little if any collimating when it goes back in. Maybe as much as you would give it on an ordinary start-of-observing night.

While you have it out, it might be time for a cleaning, and center spotting if it isn't already done!

Alex

The cg-5 and Losmandy use different dovetails. Either should be available from Anacortes. Or, if you have a machine shop, you can make them fairly easily.

Alex

The answer depends on a lot of assumptions--like how high the focuser is, what size diagonal, and all sorts of stuff.

Go here

http://home.att.net/~dale.keller/atm/newtonians/newtsoft/newtsoft.htm

and download the program. Then make some assumptions and re run till you get a design you are happy with.

Alex