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Thread: Problem matching main scope & finder scope

  1. #1
    Join Date
    Feb 2008
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    Problem matching main scope & finder scope

    Newbie question on calibrating the finder scope.

    My wife brought home a Jason model 514, 525 x 60 refractor scope. I followed direction of sighting in on an object w/ the telescope then adjusting the finder scope so that the object is exactly on the cross hairs. I did this (several times in fact), but when going to view planets, stars, once I center them in the finder scope, they are no where near the telescope field of view.

    Is it just because of movement in the mount or stand, or is there something I don't get? Seems like a pretty simple concept.

    Also, when I took the main tube out of the box (never opened) there were 2 nylon washers / bushings. The larger one - a split bushing w/ one end tapered or beveled is the one that fell off. It doesn't seem to fit down in the mounting yoke, but doesn't really seem stable enough when just barely fitting down into the mount.

    Thanks.

  2. #2
    Join Date
    Dec 2005
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    What magnification are you using on the main scope? It's better to put a low magnification eyepiece in to find an object (using the finder scope) and then increase the magnification step by step, centring the object in the field each time. If you swing your telescope to a new object with a 6mm eyepiece in you're never going to find it!

  3. #3
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    Jan 2008
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    Good answer... I'm with Clop. It does sound like you've switched from a low power ocular when you did your alignment and a higher power one to try to make observations. If you're a little off on the alignment of your finder it will turn into a huge difference with the higher power lenses.

    Maybe you could try aligning the sighting scope during the day using your highest power lens, then they'll all be dead-on.

  4. #4
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    If you are sighting on a terrestrial object, make sure it is far enough away that parallax does not throw the alignment off, or else make sure you allow for it.

    Suppose the finder is 4 inches above the axis of the main scope and you are looking at a distant street sign. Line up the main scope on a spot on the sign, and then line up the finder on a spot 4 inches higher. That will get the two scopes parallel.

    At night, you can sight in on Polaris to fine tune the alignment. It will stay put plenty long for you to work without rushing.

  5. #5
    Join Date
    Feb 2008
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    Thanks all for very helpful suggestions. I am a very technical person, but little experience w/ telescopes (done a bit of surveying). Wife & I are separated & this was supposed to be a "date." Didn't go that well, but no arguments! She's a science teacher & it would really help us to "rebond" if I could get one of these scopes working.
    If you are sighting on a terrestrial object, make sure it is far enough away that parallax does not throw the alignment off, or else make sure you allow for it.
    For optimal results, how far away should the object be when aligning the finder scope?
    line up the finder on a spot 4 inches higher
    I guess that means you have to go & measure the object you're sighting in on to pinpoint 2 spots that are exactly the same distance apart as are the cross hairs of finder scope & center of main scope?
    What magnification are you using on the main scope? It's better to put a low magnification eyepiece in to find an object (using the finder scope)
    I think I understand - but the finder scope has only one power - no replaceable eyepieces, AFAIK. I used the 20 mm eyepiece to align finder scope. You were referring to using lowest mag eyepiece in main scope - yes? Which would be 20 mm (came w/ 4, 12 & 20 mm).

    1) That is the way I sighted in the finder scope - w/ lowest power eyepiece. Maybe I need to pick an object farther away, that has an obvious identifiable small "spot" and like Hornblower suggested, compensate for the difference of center of finder scope from center of main scope.

    2) But ultimately, once the finder scope is aligned w/ main scope, shouldn't they still be aligned switching to higher power eyepieces?

    3) I found (sometimes - only used it one nite) that using the finder scope & 20 mm eyepiece, I could find the object, but even though I THOUGHT I'd aligned the finder scope, the object (star / planet) were NOT in the center of the scope. Sometimes, not in it's field of view at all - had to move the scope a bit to find it.

    Once the object WAS in focus in the scope w/ 20 mm eyepiece, switching to the 12 or 4 mm, made it impossible to find again. And using the Barlow lens was out of the question.
    Maybe you could try aligning the sighting scope during the day using your highest power lens, then they'll all be dead-on.
    I like that idea.

    4)Another thing. The finder scope is straight - no diagonal mirror. When finding / viewing objects high above horiz, have to get down on knees - tough on the back. Is this the way it has to be done w/ this type scope?

    5) She also got a Bushnell AG 78 1546 some time back w/ "546" on side of scope, which assume is obj focal length?
    It appears to be a MUCH better scope than the Jason, w/ metal tripod & more adjustments. Would everyone agree? Only one eye piece was w/ it - 5mm, making it hard to align finder scope.

    * HOW FAR AWAY would an object need to be to focus w/ the 5mm eye piece & the ?546? focal length scope?

    Haven't tested if the eye pieces are interchangeable, or how much replacements are.

    With this model Bushnell, and higher power eye pieces &/or Barlow lens, what sorts of things could you see clearly? I.E., rings of Saturn, Marvin the Martian waving from Mars?

    Thanks everyone.

  6. #6
    Join Date
    Dec 2006
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    I'm not familiar with that particular Jason. Does the 525x60 mean they are claiming 525 power?!? If so that scope is likely a toy pretending to be a real telescope. I hope they mean something else by that number like focal length.

    Though the Jason's I've seen brought into Hyde Memorial Observatory by kids who were given one were unfortunately mostly useless. Some refractors could be salvaged with new eyepieces and a few changes to the mount. Though by then they'd paid more than if they'd bought a real scope to start with. We see only the problems so don't know about good ones, if they exist that is.

    A 60mm scope should be used at about 25x (no more than 35x) to find an object. Then once centered you can raise the power to say 80x for the moon and planets for a closer view. If you can't change the eyepiece and have it stay on the object the mount is bad. Typical in dime store scopes unfortunately. A good quality 60mm will max out power at about 120x. One with a long focal length, 700mm or more might stretch to 150x but by then the image is very dim and somewhat fuzzy like an over enlarged picture. Every time you double the power an object, say the Orion Nebula, gets 4 times dimmer. Go from 20x to 120x and it just got 36 times dimmer and it was not all that bright at 20x! Go to 500x as some irresponsible manufacturers claim and you make it 625x dimmer. Talk about black holes!

    Some Jason's I saw used a rubber ring to hold one end of the finder. Does yours? That ring was insufficient and the finder would move once you pointed the scope to another part of the sky. No way it would hold alignment. Think that was a 3" reflector that had that finder. Only solution was to go with a simple soda straw glued atop the tube the finder was in. If you saw the moon through the straw it was in the eyepiece at 25x. Or else buy a cheap red dot finder for it. They went with a plastic straw.

    Right angle finders create a mirror image which is very confusing to beginners, and this experienced user for that matter. You can get them that do correct for this but their cost is likely higher than what you paid for the Jason. Their quality is far higher than any Jason I ever saw as well.

    In any case start with your lowest power when finding anything. Usually that is a 20mm or longer (bigger number) focal length eyepiece. Power is the focal length of the scope divided by the focal length of the eyepiece. So the smaller the number on the eyepiece the higher the power. If they gave you a barlow it will say 2x or 3x on it. If used (not recommended as those with these types scopes tend to give barlows an undeserved bad name) multiply the power obtained by dividing the focal length of the scope by the eyepiece focal length by the factor on the barlow. That's the approximate power of the set up. Remember, viewing with a 60mm refractor will be done at 120x or less, lower is often better and always start at the lowest power possible.

    Anytime you see a telescope advertised to work at magnifications greater than 50x per inch of aperture (2x per mm of aperture) they are making claims that are false in the sense such excess powers are worthless. Good manufacturers never make such claims, only that they provide eyepieces of certain focal lengths and powers. They are always well below the maximum (usually low and maybe medium power) and are NEVER printed in big bold letters across the box. When you see power in big bold letters on the box you are likely looking at a "toy" not a real, telescope.

    In 27 years at Hyde I'm yet to see a Jason OR Bushnell scope worth buying. Again we see only their junk scopes. If they make good ones people don't need help so we don't see them. But the cynic in me doubts they exit. Providing only a 5mm eyepiece is totally irresponsible in my opinion and is a sign they are only out to take your money and provide little of value in return. A 5mm is cheap to make as it uses far less optical glass than a 20mm so the temptation to do this is high if you are a greedy manufacturer. Bushnell changes model designations hourly it seems so I'm not at all familiar with that one. I've seen 50 or more at Hyde, many identical but NONE with the same model designation except a couple that bought two, one for each kid, both wasted money as well. Is that to keep ahead of the bad notices on the net? Makes you wonder. If that 546 is the focal length then a 5mm eyepiece is right up near the max usable power assuming better optics than I've found in any Bushnell brought to hyde. Refractor or reflector they all had pinched or otherwise distorted optics. How they do it amazes me. Even Jason usually has a good objective, its everything else that's a problem.

    Assuming the scope is otherwise ok and doesn't have the optics problems I've seen too many times (a local club member can evaluate this) a couple new eyepieces, I assume it takes standard 1.25" ones though some take 0.926" ones, would be needed. Sirius Plossls are about as cheap as I'd go as they would work on any other scope you might buy in the future. They cost about $35 each when on sale. Usually you can find a dealer offering a sale. Orion has them for $34 I see. They sell some 3 element modified Kellners for $29 but the focal length selection is poor so might not fit your needs.

    A bargain telescope isn't a cheap one, its one of good quality that will hold its value so when you are ready to move up later you can get much, if not all, of your money back when selling it. Think more like buying an investment you can use than a computer that will be obsolete, worn out and worthless in 5 years. A well maintained 50 year old scope shows you the sky exactly the same as it did when new. 2 of mine are over 50 and 7 over 40. Astronomy clubs are often a good source of used, good quality, bargain (in the sense that it holds value) telescopes as members are selling to move up. 3 or 4 come available in my club each year and are quickly sold to other members. One, a 6" Criterion RV6 over 45 years old now has gone through over a dozen members. BTW, Bushnell bought Criterion and turned the RV6 into junk much to the dismay of amateurs everywhere. They soon discontinued it for lack of sales. It had been the best selling 6" scope prior to their buyout of Criterion.

    The best way to learn what various scopes can do is to attend a few star parties thrown by your local club. There you will see real, not toy, scopes and learn what they can and can't do far easier and better than any other way. Take the scopes you have, they may see a easy way to fix a problem you're having. Some larger clubs have loaner scopes for members waiting to save up to buy a usable scope as well.
    http://www.astronomyclubs.com/
    http://www.skyandtelescope.com/community/organizations

    Rick

  7. #7
    Join Date
    Feb 2008
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    63
    so if you align during the day with highest power then any other eyepiece will be close to center in the main scope ? i didnt think about this but thats a good idea to try out..
    Quote Originally Posted by FriedPhoton View Post
    Good answer... I'm with Clop. It does sound like you've switched from a low power ocular when you did your alignment and a higher power one to try to make observations. If you're a little off on the alignment of your finder it will turn into a huge difference with the higher power lenses.

    Maybe you could try aligning the sighting scope during the day using your highest power lens, then they'll all be dead-on.

  8. #8
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    Quote Originally Posted by malevy View Post
    so if you align during the day with highest power then any other eyepiece will be close to center in the main scope ? i didnt think about this but thats a good idea to try out..
    During the day I would stick with the lowest power eyepiece and align the finder roughly on a distant street sign, as I described in an earlier post. That would make finding Polaris with the same eyepiece a sure thing. Then I would center the star in the main scope, switch to high power, touch up the centering, and finally touch up the finder. If everything is good and tight, you should be good to go for finding other objects in the high power eyepiece.

  9. #9
    Join Date
    Dec 2007
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    My suggestion is to align at night, using a light on a distant radio tower or street light as far away as possible. One mile or more is better than across the street, that's for sure.

    Good luck with the scope and the domestic issues.

    -Veeger

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