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View Full Version : I think something's wrong with my friend's telescope...



Madcat
2003-Sep-12, 09:44 PM
He's had this problem for a while now and it really perplexes me...

The scope seems to work fine on just about everything, except for Mars. It works on stars, the moon, city lights, etc. When we pointed it at Mars a few weeks ago, all we could see was a huge yellow light. It filled up the entire field of vision. At first I thought the scope had a hole in it somewhere and we put a blanket around it... no dice. Then I thought it might be a light coming from the same general direction as Mars so we moved a few miles and set the scope up again. Same thing happened. Beginning to assume a problem with the Telescope itself, we changed the eyepiece to no effect, and then began looking at other things to see if they came into focus. They did. It had no trouble resolving stars. The only time this thing had any problems whatsoever was when we looked at Mars. Any guesses as to what's going on here?

gethen
2003-Sep-12, 10:06 PM
Very strange. I was going to suggest a different eyepiece, until I saw you'd tried that. Charlie in Dayton, where are you?

Dickenmeyer
2003-Sep-13, 04:27 AM
What kind of scope is it? An out of focus newtonian can show a big bright blob but I can't say why you wouldn't be able to focus on Mars if you can focus everything else. An eyepiece giving too much magnification for the seeing conditions is awfully hard to focus too, in many cases it can't be focused at all because the air is just too turbulent. Did you try lower power eyepieces?

kookbreaker
2003-Sep-13, 04:49 AM
The yellow color and the filling of the field of view are perplexing. Mars as a blob should, by all rights, be a red blob.

Since you mentioned city lights. You wouldn't happen to be trying to look at Mars with a streetlight or other light source between the opening and Mars, woiuld you?

[/u]

Madcat
2003-Sep-13, 04:58 AM
As to the type of the scope, I honestly don't know. I could ask him. (Heck, I will ask him! :) ) It was a Newtonian scope. One other question. (forgive me here, I like the concept of Astronomy but I hadn't done much before the night in question.) Is it normal to see the second mirror inside of the scope? I mean, should you see the little disc inside that reflects the light into the eyepiece obstructing the view of the sky?

beskeptical
2003-Sep-13, 05:53 AM
There is no logic in the scope 'working' when viewing the Moon or stars and not when viewing Mars.

You are doing something different when you move the scope around. Maybe when you try to focus Mars you are doing something.

Mars from my scope isn't too red, it is a small yellowish ball. I have an D 80mm, F1200mm scope. I have a Newtonian also but I haven't had it out lately.

Madcat
2003-Sep-13, 06:33 AM
There is no logic in the scope 'working' when viewing the Moon or stars and not when viewing Mars.

Well, yes I understand that. I'm puzzled though, as I actually did spend the better part of the night trying to come up with logical reasons that the scope was not working and remedy them. I couldn't. (Just so you know right now, I'm not trying to suggest that there is an "illogical" reason that the scope did not work. I do not believe that "someone was keeping me from seeing Mars" or any such **. I believe the scope is damaged in an unusal fashion and was wondering if anyone has ever had a similar problem.) Is there any logical reason that a scope could view certain objects but not others? You seem to be implying that there is not, and while I agree with you I am rather sad because the telescope still does not work. :(

beskeptical
2003-Sep-13, 08:23 AM
If I could see it I could tell you. I didn't think you were being irrational or anything. It's kind of like when I used to have trouble with my computer years ago. I kept thinking it was messing up. Eventually, I would find what I was doing wrong.

That's what I think is happening to you. You are doing something and if you keep trying to figure it out, you will. Because it just isn't logical that something would be wrong with the scope and give you those symptoms.

Whenever I have a big fuzzy light in my telescope view, it is waaaay out of focus. That will do it. And, I think the suggestion you are pointed at a foreground light could do it but it sounds like you checked for that. A really dirty or scratched eyepiece could do it, but you wouldn't see the Moon if that were the case.

Did you focus on the Moon and then move your scope over to see Mars? If you did, there isn't any reason Mars wouldn't be at least almost in focus.

SarahMc
2003-Sep-13, 03:49 PM
As to the type of the scope, I honestly don't know. I could ask him. (Heck, I will ask him! :) ) It was a Newtonian scope. One other question. (forgive me here, I like the concept of Astronomy but I hadn't done much before the night in question.) Is it normal to see the second mirror inside of the scope? I mean, should you see the little disc inside that reflects the light into the eyepiece obstructing the view of the sky?

I assume you mean that you can see the shadow of the secondary in an EP. If you mean just looking into the scope, either through the aperture or the focuser, yes you should see the secondary also.

That would indicate an out-of-focus image. When you defocus a star, you should see a "doughnut" shaped object in the EP (with a newtonian, SCT or MCT, not refractors). The center dark area is the secondary mirror blocking light from the object.

Since you have good focus on stars and the moon, it's highly unlikely that you wouldn't be able to focus on Mars. If you can focus on stars, you can focus on Mars. Even the moon is close enough (regarding focus) that you should be very close to focus - if you just move the scope to Mars after focusing on the moon's surface.

Is it possible the secondary mirror support, or the spider itself is loose? Maybe just lowering the scope to a lower altitude changes the secondary's alignment, whereas when looking at stars or the moon you were at a higher altitude and the secondary was supported (more steady) by gravity?

I'd have him check all the hardware/mechanicals, do a collimation, and try again. Always start observing with the lowest power EP ( largest size in mm ), then move up in power if the conditions/scope can handle it. If you start getting "mushy" or "soft" images, you've gone too far and need to drop back to a lower power. I can rarely get above 300x, except for a few times a year when the conditions are just right. Have him check (and set) collimation with a star at the zenith, and then check again with a star closer to the horizon.

Also, you didn't state at what time you were viewing Mars, but try to wait until it's reached it's highest altitude for your location. The seeing is always better the closer you get to the zenith.

RichField
2003-Sep-15, 05:36 PM
As a troubleshooting procedure, I'd recommend trying the following:

1. Set up the scope in an area with a clear dark southern and eastern horizon if possible.
This isn't critical, but may help later. As Sarah mentioned, try to wait a bit to let Mars get higher up in the sky, but if you have time, you can get the scope outside to make sure that it's temperature is near ambient to reduce tube currents.

2. Start with the lowest power (longest focal length eyepiece) and try to find a naked eye star within a few degrees of Mars in the sky, then get it in the scope. This is where the darker sky will help. If you can't find any close by, you can just point the scope a few degrees away from Mars, I'm pretty sure that there will be stars there visible with the scope.

3. Now that you have stars in the field of view, focus the image. Should be pinpoints, or pretty close, right?

4. Now shift the scope over to Mars. Go slowly in case something is loose, and don't touch the focuser.
What do you see now? Is it still a full FOV blob?
Like others have said, at least you have a good idea that the image is focused or pretty close.

If by chance you get a disk to appear, take your time and look at it. Details on Mars are very subtle, especially now that the polar cap has shrunk so much. Poor atmospheric conditions (seeing) can wash out most of them. On a bad night you may only see a brightly colored disk with edges that look like they're boiling or burning. Seeing changes by the second, that's why patience may pay off and details will often pop in and out of view. In any case, the image should not fill the entire FOV.
If this is working and you want to change eyepieces I'd suggest repeating the process starting with the stars to make sure you get the focus right. Again, you'll probably have to wait some time to make out surface features.

Some other thoughts. Personally, I don't see Mars as red. To my eye, it's closer to a light orange or pale brick. Is that still red? Maybe, but I don't see it that way. And I can never remember if it's the bending or non-bending red :)

Finally, dew, you may want to check for it, particularly on the eyepiece or secondary mirror. I doubt it would produce the effect you described, but it could definitely negatively impact the overall performance and views.

Let us know how you make out.

Madcat
2003-Sep-16, 04:42 AM
Well, I don't want to give up on the scope, but my vacation's over. I'm back in the big city so there's not much to see at the moment. Thank you for your suggestions though, I'll have to set aside a weekend to go someplace and try them out. :)

Charlie in Dayton
2003-Sep-17, 04:30 AM
I'm here, I'm here...lessee...[trundles off reviewing other posts in the thread]...how interesting...[trundles back]...

There will be points here that others have covered. Great minds think alike.
:-?

1. Start low power and work up. It's easy to wash detail out of an image yet still have the image there as a sharp but featureless disk. Max telescope power rule of thumb is 2x per mm aperture/50x per inch aperture.
2. It doesn't take much to wash detail out of Mars, as it isn't that sharp to start with. Even with proper power and good viewing conditions, with the naked eye you'll spend a few minutes looking before some detail comes swimming out. The Polar Cap is the most obvious. The dark vs light areas are much more subtle.
3. Do the stars resolve to sharp pinpoints? Can you resolve good crisp crater views of the Moon? Is the terminator (not Ah-nuld) sharp? Resolving city lights - how close are those lights? It's tough for a scope to focus close (50 feet or so) and far away (stars etc)..
4. How's the aiming? Is what's dead center in the finder relatively close to dead center in the scope?

Seeing as everything else was in focus but Mars, I believe you went too high a power, and expected to see something that looked as detailed as the Moon. Ain't gonna happen. Focus so that the edges of the disk are are sharp. Gaze at that featureless blob for a moment. Look for a much brighter area, probably at the top, which reminds you of a space picture of Earth looking at the South Pole. The bright spot of the Polar Cap will suddenly make itself plain to you. Then, just look for awhile. The subtler light/dark areas will resolve themselves eventually -- just takes your eyes to get used to it for awhile.

Don't expect Dreamworks-style details -- they ain't there...

Go give it another try with a different mindset. I'll bet things start working.

And by the way -- Mars is still so bright, this stuff should work pretty close to equally well in the city or in the country. I amble out of work at maybe 2ayem here, and if it's not cloudy, Mars is plainly, almost painfully, obvious. I've seen Mars every clear night after work for 10 days now -- but because of light pollution, hadn't seen a star for better than a week.
Don't let seeing no stars with the nekkid eyeball fool you -- set that scope up and go to it. Y'all will be amazed... :o

digitalspector
2003-Sep-17, 05:56 AM
here is my cheap contribution...

my brother has a cheap Jason group scope.....75$.

he kept telling me how clear mars SHOULD be seen...yet to him it was a blob.

it came with a 6mm lens and hmm a 12mm (not sure on the 12....think so though) and a 2x barlow.

cheap optics....its was about 6 years old and the optics were pretty much crap.

moon looked good through the larger mm lens....but after that things got warped.

gethen
2003-Sep-18, 01:04 PM
I hate to even suggest this, but it came up the other night when a friend was looking through my scope and complained that she could only see a big white blob. Of course, the scope was just out of focus and she was seeing the mirrors. If you expect to see something very large like the moon, and you're looking at Mars, you could just be way out of focus like my friend and not realize it. Sorry if this seems condescending, but it did happen to me.

tngolfplayer
2003-Sep-18, 03:44 PM
Most of my views of mars are either dark yellow or slight orange. Even the pictures I took of it are that way(excepte one that was blue but that was a software error).