Posts Made By: Alex McConahay

Mark,

Be sure to go here, especially on a day when the lava is flowing and the seeing is good.

Alex
(with apologies for taking up bandwidth if you have seen this picture posted before.)

Go get Covington's software--Exposure calculator I think it is called (download for free). Can't remember the link, but just do a search.

It will tell you all that and more.

Alex

Ken,

You are talking to people who do this for a hobby, not for real life. THerefore, you will have an inordinate number of people who fuss things a whole lot more than necessary if they were just getting along on a day-by bay basis. You can look to MAPUG and find hundreds of people complaining (and coming up with fixes for) the LX200--one of the most wonderful pieces of technology ever delivered to the masses. (And the same can be said for, the Obsession group, and virtually all other scopes.) After all, they have repair shops for Rolls Royces.

By the way, I am one of those fussy people sometimes.

My advice--quit reading, and go visit star parties. Lots of them. ANd use lots of scopes. And then think about what you want for your first scope. (And your second, and third, and whatever--because you will not find one that satisfies every need.)

Most of your questions are about value judgements. They will be answered one way by Ford drivers and another by Chevy, and a third by Mercedes owners, I won't get into them. What you value is up to you.

One question has gone unanswered (actually two, since your question about false color and achromatic/apochromatic have the same answer). A lens focuses light by bending it. However, different colors of light bend to different degrees. A simple lens (one element) focuses the different colors of light at different points. As a result, you will get something in focus, and every other color shifted left or right of that color that is in focus. SO, you see the object, and a colorful glow on either side. This glow is "false color." An achromat is usually made of two elements, one counteracting (or at least working with) the other to focus two colors at the same point. Obviously, you get something in focus, and two glows on either side of the object. An apochromat (specially designed with multiple elements and different types of (usually expensive) glass to work together) focuses all three colors of light at the same point, so you get the object in focus, but no glow on either side. You have to pay more for more glass, more expensive types of glass, and better engineering and execution of the design. Since you have already paid more, they throw in more expensive mechanics in the scope, better fit and finish, and really bump up the price of the scope......That is why you pay more. As you can see, apochromatics are better for what you see, but not as good for the budget---As I say, what do you value?

As for an astrophotography rig for less than $1000, nothing will do for long, but you can start with a small scope on a CG-5, and a short focal length camera lens. (But you will have to move on to something much more costly soon if you are at all serious.)

Alex

Hi all,

Please check the star party links at Riverside Astronomical Society. We have a party every month. Everybody welcome. Details at Rivastro.org.

(I think this is the first time I have been on this forum since December something--that's a long time away.

Alex

Brian,

It depends on what you are scanning and what how you intend to output the results. If you are going to print it, what is the resolution of your printer? If you are saving for the web, what size computer screen? It also depends on how high hefty your computer and how fast it is.

Having said that, I generally try to scan at the highest resolution possible, and then reduce the file size after the scan if I am not outputting to a large print.

Alex

Be aware that if you move your primary up, you may have problems bringing your eyepieces to focus from the other side--the problem is that your camera adds an inch or two to the length of the lightpath--if you move the primary up, the light path will be too short for the visual eyepieces.

One thing nobody has mentioned is that you might have just enough travel in your collimating screws to move the primary just enough.

Alex

RTMC and Camp Oakes is fine. It made it through last October's fires without damage, and this week's was far away (Big Bear is a big place.)

However, the fire marshall was pretty strict last Memorial Day. (He doesn't want anybody hurt on his watch.....And that is the way it should be.) Therefore, he is holding the RTMC staff to coming up with a pretty strict safety plan, including staff monitors, evacuation routes, and such. It won't change RTMC (might re-arrange some of the parking), but it will make it more clear that the fire rules have to be reckoned with.

Alex

Wayne,

I agree with Randy that it does not sound like your mirror needs recoating. You would be talking about places where the coating is thin enough to see through, or irregular areas of the mirror--part of it looking different from other parts.

I assume your interest in "wave-rating" is merely curiousity. Are you happy with the images? Then the wave rating--whatever that means-- is good enough. If not, it is not. (Although it could be a lot of things besides "wave rating" affecting your view.)

But, to answer your question. You can probably easily get a test by visiting a local ATMer (Amateur Telescope Maker) by contacting your local Astronomy Club. If you are in SOuthern California, please come to a RATS (Riverside Amateur Telescope Makers) meeting. (See Rivastro.org.)

If that is difficult, get any good book on star testing or telescope making, and you should get the right procedures.

I would not go to the difficulty of shipping the mirror off someplace--you have the possibility of damage, and a bunch of other tribulations-- and all you will find out is a number that means little unless you intend to have it refigured for sure because you are unhappy with performance.

Alex

Try your local Ace hardware before you get too fancy--they have much of what you are looking for--and you can try the size out right there in the store.

Alex

Guide stars show a whole lot better in It is a whole lot easier to use a guidescope than an off axis guider. IN an off axis guider, by definition, your are using the edge of the field, and there may be no convenient stars there for you. WIth a refractor, it should be fine. With a Newt (to a minor degree) or an SCT, you have to be a lot more careful about image shift. Using a refractor as a guide scope with an SCT you may get image shift.

I'm not really familiar with the rest of your terms, so, I'll stay out of that part of the conversation.

Alex