Question about Bushnell Deep Space 78-9518 (675 x 114mm) Telescope

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Lost vision The telescope was working fine until I was trying to match the view through the smaller spotting scope with that of the main telescope, and suddenly I could faintly tell I was aimed at the moon by a soft glow alone, but could no longer actually see details nor the usual brightness of it. I've taken the scope apart and cleaned the lenses and mirror. I can see beautifully if I remove the eyepiece, but of course I'm just looking at the mirrors inside at that point. When I replace the eyepiece, all I can see is that very faint glow which, when focused, gives me that funky view of the inside of my own eyeball like when you get your eyes checked at the optometrist's office and they shine that bright light in your pupil. Any idea what's happened here and how I can fix it? Maybe I need a new eyepiece?

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Your telescope is a "Newtonian," as such it requires regular "collimation" Collimation the alignment of the optics. The mirrors must be lined up properly for the telescope to deliver a good image to the eyepiece. Your scope sound like it is way out of collimation. My guess is that the diagonal (secondary) mirror has rotated in it's mount. There are three basic tools for collimating a Newtonian the Sight Tube, Cheshire and Autocollimator. To get your digonal aligned correctly you need a sight tube. Rather than spend a lot on these consider making your own and keep an eye on eBay offerings. Don't bother investing in a laser collimator, they simply don't do the job unless you go for the very best. From some help with the collimation process check these links.
http://www.astronexus.com/node/6
http://www.amateurastronomy.com/collimate.html
The 60 page pamphlet "New Perspectives on Newtonian Collimation," Fourth Edition by Vic Menard and Tippy D’Auria runs $10, but if you really want to do it right it's worth the money.
HTH, George

Posted on Mar 01, 2008

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What is field of view in Binoculars, Spotting Scopes and Rifle Scopes?


Optical field of view (FOV) refers to the width of the area that you can see when looking through a pair of Binoculars or a Spotting Scope, quite simply, how wide an area you can see through your optics. Field of view is usually described in terms of 'linear field of view' or 'angular field of view'. Both figures essentially indicate that the field of view of the optic is a certain width, but they just use different numbers to describe this.

Linear field of view is also known as the true field of view and indicates the width (in m) of the area that you can see when standing 1,000m away from an object.
Angular field of view is also known as the apparent field of view and refers to the true angle (in degrees) seen through the optics.
It is easy to convert between the two field of vision measurements:
To convert an angular field of vision to a linear field of vision, simply multiply the angular field of vision by 52.5.
To convert a linear field of vision to an angular field of vision, simply divide the liner field of vision by 52.5.

When choosing your binoculars or spotting scope, take some time to consider where you are planning to use them, as this will indicate the most suitable field of view required to get the most out of your product. The most important thing to remember is that the larger the number is given to the field of view (FOV), the larger the width of the area you will be able to see through your scope. A larger field of view is desirable if you are planning to use your scope to watch anything that is moving quickly across your viewing area as it will make it easier to aim and stay on a moving subject. For this reason, scopes with a larger field of view are favored by people watching birds in flight, a ball at a cricket game, an athlete in a race or views from a moving car.
Don't forget field of view (FOV) and magnification are closely linked, with higher magnifications resulting in a smaller field of view. Take some time to consider whether you wish to view your subject in great detail, or would prefer to be able to keep track of it if it is moving quickly; after all, there's no point being able to see the fine detail on a bird's feather if you can't find the bird in the first place!

Mar 21, 2018 | Optics

1 Answer

MI have a 90mm cassegrain gps computer astrophotography telescope. I am able to locate items on the viewfinder/spotter scope but unable to view it thru the telescope, what could i be doing wrong


Your finderscope is NOT lined up with the main tube. Point the scope at a bright star or planet or even the center of the moon. Get it CENTERED in the main eyepiece of the telescope. Then without moving the main tube adjust the crosshairs on the finder scope to point at the same spot.

May 12, 2011 | Optics

1 Answer

We cant see anything but black


New telescope users are taken by surprise at the difficulty of just pointing the telescope in the right direction to see anything. The field of view is quite limited, especially if you are using a high power eyepiece. The higher the power of eyepiece on a telescope, the dimmer the image, the more difficult to aim it at any chosen object, and the more difficult to focus. When the scope is not focussed, even if there are stars in the field of view, they will only be faint blurs.

It is best when you are starting out with a telescope to try it with the least powerful eyepiece (the one with the highest number) to begin with, until you become more familiar with how it works. Do NOT use the Barlow lens if one came with the scope.

The finder scope is meant to help you get the main scope lined up on the object you want to view, but it won't be any use in pointing the telescope until you adjust it to precisely line up with the main scope. Telescope manuals recommend that you do this in daylight, by pointing the scope at an object on the horizon and adjusting the finder to match (never point a telescope toward the Sun!). Once you have a tree or mountain peak in the center of the main scope's image, you can then adjust the screws around the finder scope to get the crosshairs (or red dot) centered on the same object. It is very difficult to do this job in the dark, especially as objects in the sky are constantly on the move.

You will find that there is a very wide range of movement in the focus mechanism, because different eyepieces focus at different points, but the actual focus range for any eyepiece will be a small part of the overall range afforded by the focusing mount. It is much easier to familiarise yourself with this in daylight.

At this point you will learn that astronomical telescopes usually show an upside down image. There is a good reason for this- erecting the image needs more bits of glass in the light path, which reduces the amount of light and increases aberrations. Even if this is only slight, astronomers prefer to avoid it, and they don't really care which way up the Moon or Jupiter appear. It is possible to fit an erecting prism or eyepiece to most astronomical telescopes, and some of them come with one, but one wouldn't bother to do this with the small finder scope.

Once you have done the above, you can try the scope at night, on an easy to find bright object like the Moon. Looking at random stars will probably be disappointing, as they don't look different under magnification. You will have to find planets, star clusters or nebula to see anything interesting. You will also find the the object you are looking at swims out of the viewing field, and you must continually move the scope to follow it. This will be more pronounced at higher magnifications. Again, use the least powerful eyepiece. Small scopes are often advertised as having unrealistic powers (300, 500) which can never be practically achieved. You just get dim blurs.

There is an excellent website for beginner telescope users at THIS LINK

Jan 24, 2011 | Vivitar (1607225) Telescope

1 Answer

Just had a konusmotor 500 telescope and have built it to the instructions, but nothing on how to use. only a beginner but how do you increase the size of the object you are looking at,eg the moon looks the...


Are you viewing the moon through the small finder scope on top of the main tube? That is only used for aiming the scope, and has very little magnification. The moon should fill the field of view on even the lowest magnification on the main scope.

A reflector type scope has the eyepiece mount on the side of the main tube, near the top end, pointing into the side of the scope. This mount should have an eyepiece placed in it- use the one with the biggest number to start with (that will have the least magnification). Do NOT use the Barlow lens if one came with the scope. You look into the side of the tube with this type of scope, not along it.

New telescope users are taken by surprise at the difficulty of just pointing the telescope in the right direction to see anything. The field of view is quite limited, especially if you are using a high power eyepiece. The higher the power of eyepiece on a telescope, the dimmer the image, the more difficult to aim it at any chosen object, and the more difficult to focus. When the scope is not focussed, even if there are stars in the field of view, they will only be faint blurs.

The finder scope is meant to help you get the main scope lined up on the object you want to view, but it won't be any use in pointing the telescope until you adjust it to precisely line up with the main scope. Telescope manuals recommend that you do this in daylight, by pointing the scope at an object on the horizon and adjusting the finder to match (never point a telescope toward the Sun!). Once you have a tree or mountain peak in the center of the main scope's image, you can then adjust the screws around the finder scope to get the crosshairs (or red dot) centered on the same object. It is very difficult to do this job in the dark, especially as objects in the sky are constantly on the move.

You will find that there is a very wide range of movement in the focus mechanism, because different eyepieces focus at different points, but the actual focus range for any eyepiece will be a small part of the overall range afforded by the focusing mount. It is much easier to familiarise yourself with this in daylight.

At this point you will learn that astronomical telescopes usually show an upside down image. There is a good reason for this- erecting the image needs more bits of glass in the light path, which reduces the amount of light and increases aberrations. Even if this is only slight, astronomers prefer to avoid it, and they don't really care which way up the Moon or Jupiter appear. It is possible to fit an erecting prism or eyepiece to most astronomical telescopes, and some of them come with one, but one wouldn't bother to do this with the small finder scope.

Once you have done the above, you can try the scope at night, on an easy to find bright object like the Moon. Looking at random stars will probably be disappointing, as they don't look different under magnification. You will have to find planets, star clusters or nebula to see anything interesting. You will also find the the object you are looking at swims out of the viewing field, and you must continually move the scope to follow it. This will be more pronounced at higher magnifications. This scope has a motor to track the scope and keep objects in view, but you will have to get the scope set up for that for it to work correctly. Again, use the least powerful eyepiece to start. Small scopes are often advertised as having unrealistic powers (300, 500) which can never be practically achieved. You just get dim blurs.

There is an excellent website for beginner telescope users at THIS LINK

Jan 22, 2011 | Konusmotor 500 (230 x 114mm) Telescope

1 Answer

Cannot sed anything in my brand new telescope. I have a full moon in the cross hairs of the viewfinder, but the moon is faint in the scope.


New telescope users are taken by surprise at the difficulty of just pointing the telescope in the right direction to see anything. The field of view is quite limited, especially if you are using a high power eyepiece. The higher the power of eyepiece on a telescope, the dimmer the image, the more difficult to aim it at any chosen object, and the more difficult to focus. When the scope is not focussed, even if there are stars in the field of view, they will only be faint blurs.

It is best when you are starting out with a telescope to try it with the least powerful eyepiece (the one with the highest number) to begin with, until you become more familiar with how it works. Do NOT use the Barlow lens if one came with the scope.

The finder scope is meant to help you get the main scope lined up on the object you want to view, but it won't be any use in pointing the telescope until you adjust it to precisely line up with the main scope. Telescope manuals recommend that you do this in daylight, by pointing the scope at an object on the horizon and adjusting the finder to match (never point a telescope toward the Sun!). Once you have a tree or mountain peak in the center of the main scope's image, you can then adjust the screws around the finder scope to get the crosshairs (or red dot) centered on the same object. It is very difficult to do this job in the dark, especially as objects in the sky are constantly on the move.

You will find that there is a very wide range of movement in the focus mechanism, because different eyepieces focus at different points, but the actual focus range for any eyepiece will be a small part of the overall range afforded by the focusing mount. It is much easier to familiarise yourself with this in daylight.

At this point you will learn that astronomical telescopes usually show an upside down image. There is a good reason for this- erecting the image needs more bits of glass in the light path, which reduces the amount of light and increases aberrations. Even if this is only slight, astronomers prefer to avoid it, and they don't really care which way up the Moon or Jupiter appear. It is possible to fit an erecting prism or eyepiece to most astronomical telescopes, and some of them come with one, but one wouldn't bother to do this with the small finder scope.

Once you have done the above, you can try the scope at night, on an easy to find bright object like the Moon. Looking at random stars will probably be disappointing, as they don't look different under magnification. You will have to find planets, star clusters or nebula to see anything interesting. You will also find the the object you are looking at swims out of the viewing field, and you must continually move the scope to follow it. This will be more pronounced at higher magnifications. Again, use the least powerful eyepiece. Small scopes are often advertised as having unrealistic powers (300, 500) which can never be practically achieved. You just get dim blurs.

There is an excellent website for beginner telescope users at THIS LINK

Jan 19, 2011 | Celestron PowerSeeker 114 EQ Telescope

1 Answer

Cannot see anything in the telescope looks dark


New telescope users are taken by surprise at the difficulty of just pointing the telescope in the right direction to see anything. The field of view is quite limited, especially if you are using a high power eyepiece. The higher the power of eyepiece on a telescope, the dimmer the image, the more difficult to aim it at any chosen object, and the more difficult to focus. When the scope is not focussed, even if there are stars in the field of view, they will only be faint blurs.

It is best when you are starting out with a telescope to try it with the least powerful eyepiece (the one with the highest number) to begin with, until you become more familiar with how it works. Do NOT use the Barlow lens if one came with the scope.

The finder scope is meant to help you get the main scope lined up on the object you want to view, but it won't be any use in pointing the telescope until you adjust it to precisely line up with the main scope. Telescope manuals recommend that you do this in daylight, by pointing the scope at an object on the horizon and adjusting the finder to match (never point a telescope toward the Sun!). Once you have a tree or mountain peak in the center of the main scope's image, you can then adjust the screws around the finder scope to get the crosshairs (or red dot) centered on the same object. It is very difficult to do this job in the dark, especially as objects in the sky are constantly on the move.

You will find that there is a very wide range of movement in the focus mechanism, because different eyepieces focus at different points, but the actual focus range for any eyepiece will be a small part of the overall range afforded by the focusing mount. It is much easier to familiarise yourself with this in daylight.

At this point you will learn that astronomical telescopes usually show an upside down image. There is a good reason for this- erecting the image needs more bits of glass in the light path, which reduces the amount of light and increases aberrations. Even if this is only slight, astronomers prefer to avoid it, and they don't really care which way up the Moon or Jupiter appear. It is possible to fit an erecting prism or eyepiece to most astronomical telescopes, and some of them come with one, but one wouldn't bother to do this with the small finder scope.

Once you have done the above, you can try the scope at night, on an easy to find bright object like the Moon. Looking at random stars will probably be disappointing, as they don't look different under magnification. You will have to find planets, star clusters or nebula to see anything interesting. You will also find the the object you are looking at swims out of the viewing field, and you must continually move the scope to follow it. This will be more pronounced at higher magnifications. Again, use the least powerful eyepiece. Small scopes are often advertised as having unrealistic powers (300, 500) which can never be practically achieved. You just get dim blurs.

There is an excellent website for beginner telescope users at THIS LINK

Jan 09, 2011 | Meade DS-2114 ATS (325 x 114mm) Telescope

2 Answers

All we see through the telescope is black


New telescope users are taken by surprise at the difficulty of just pointing the telescope in the right direction to see anything. The field of view is quite limited, especially if you are using a high power eyepiece. The higher the power of eyepiece on a telescope, the dimmer the image, the more difficult to aim it at any chosen object, and the more difficult to focus. When the scope is not focussed, even if there are stars in the field of view, they will only be faint blurs.

It is best when you are starting out with a telescope to try it with the least powerful eyepiece (the one with the highest number) to begin with, until you become more familiar with how it works. Do NOT use the Barlow lens if one came with the scope.

The finder scope is meant to help you get the main scope lined up on the object you want to view, but it won't be any use in pointing the telescope until you adjust it to precisely line up with the main scope. Telescope manuals recommend that you do this in daylight, by pointing the scope at an object on the horizon and adjusting the finder to match (never point a telescope toward the Sun!). Once you have a tree or mountain peak in the center of the main scope's image, you can then adjust the screws around the finder scope to get the crosshairs (or red dot) centered on the same object. It is very difficult to do this job in the dark, especially as objects in the sky are constantly on the move.

You will find that there is a very wide range of movement in the focus mechanism, because different eyepieces focus at different points, but the actual focus range for any eyepiece will be a small part of the overall range afforded by the focusing mount. It is much easier to familiarise yourself with this in daylight.

At this point you will learn that astronomical telescopes usually show an upside down image. There is a good reason for this- erecting the image needs more bits of glass in the light path, which reduces the amount of light and increases aberrations. Even if this is only slight, astronomers prefer to avoid it, and they don't really care which way up the Moon or Jupiter appear. It is possible to fit an erecting prism or eyepiece to most astronomical telescopes, and some of them come with one, but one wouldn't bother to do this with the small finder scope.

Once you have done the above, you can try the scope at night, on an easy to find bright object like the Moon. Looking at random stars will probably be disappointing, as they don't look different under magnification. You will have to find planets, star clusters or nebula to see anything interesting. You will also find the the object you are looking at swims out of the viewing field, and you must continually move the scope to follow it. This will be more pronounced at higher magnifications. Again, use the least powerful eyepiece. Small scopes are often advertised as having unrealistic powers (300, 500) which can never be practically achieved. You just get dim blurs.

There is an excellent website for beginner telescope users at THIS LINK

Jan 08, 2011 | Tasco Novice 30060402 (402 x 60mm)...

1 Answer

I cant see anything through my telescope


New telescope users are taken by surprise at the difficulty of just pointing the telescope in the right direction to see anything. The field of view is quite limited, especially if you are using a high power eyepiece. The higher the power of eyepiece on a telescope, the dimmer the image, the more difficult to aim it at any chosen object, and the more difficult to focus. When the scope is not focussed, even if there are stars in the field of view, they will only be faint blurs.

It is best when you are starting out with a telescope to try it with the least powerful eyepiece (the one with the highest number) to begin with, until you become more familiar with how it works. Do NOT use the Barlow lens if one came with the scope.

The finder scope is meant to help you get the main scope lined up on the object you want to view, but it won't be any use in pointing the telescope until you adjust it to precisely line up with the main scope. Telescope manuals recommend that you do this in daylight, by pointing the scope at an object on the horizon and adjusting the finder to match (never point a telescope toward the Sun!). Once you have a tree or mountain peak in the center of the main scope's image, you can then adjust the screws around the finder scope to get the crosshairs (or red dot) centered on the same object. It is very difficult to do this job in the dark, especially as objects in the sky are constantly on the move.

You will find that there is a very wide range of movement in the focus mechanism, because different eyepieces focus at different points, but the actual focus range for any eyepiece will be a small part of the overall range afforded by the focusing mount. It is much easier to familiarise yourself with this in daylight.

At this point you will learn that astronomical telescopes usually show an upside down image. There is a good reason for this- erecting the image needs more bits of glass in the light path, which reduces the amount of light and increases aberrations. Even if this is only slight, astronomers prefer to avoid it, and they don't really care which way up the Moon or Jupiter appear. It is possible to fit an erecting prism or eyepiece to most astronomical telescopes, and some of them come with one, but one wouldn't bother to do this with the small finder scope.

Once you have done the above, you can try the scope at night, on an easy to find bright object like the Moon. Looking at random stars will probably be disappointing, as they don't look different under magnification. You will have to find planets, star clusters or nebula to see anything interesting. You will also find the the object you are looking at swims out of the viewing field, and you must continually move the scope to follow it. This will be more pronounced at higher magnifications. Again, use the least powerful eyepiece. Small scopes are often advertised as having unrealistic powers (300, 500) which can never be practically achieved. You just get dim blurs.

There is an excellent website for beginner telescope users at THIS LINK

Jan 07, 2011 | Meade 60AZ-M Jupiter Telescope 60mm...

1 Answer

I cannot see anything and what is the finder scope on top for?


New telescope users are taken by surprise at the difficulty of just pointing the telescope in the right direction to see anything. The field of view is quite limited, especially if you are using a high power eyepiece. The higher the power of eyepiece on a telescope, the dimmer the image, the more difficult to aim it at any chosen object, and the more difficult to focus. When the scope is not focussed, even if there are stars in the field of view, they will only be faint blurs.

It is best when you are starting out with a telescope to try it with the least powerful eyepiece (the one with the highest number) to begin with, until you become more familiar with how it works. Do NOT use the Barlow lens if one came with the scope.

The finder scope is meant to help you get the main scope lined up on the object you want to view, but it won't be any use in pointing the telescope until you adjust it to precisely line up with the main scope. Telescope manuals recommend that you do this in daylight, by pointing the scope at an object on the horizon and adjusting the finder to match (never point a telescope toward the Sun!). Once you have a tree or mountain peak in the center of the main scope's image, you can then adjust the screws around the finder scope to get the crosshairs (or red dot) centered on the same object. It is very difficult to do this job in the dark, especially as objects in the sky are constantly on the move.

You will find that there is a very wide range of movement in the focus mechanism, because different eyepieces focus at different points, but the actual focus range for any eyepiece will be a small part of the overall range afforded by the focusing mount. It is much easier to familiarise yourself with this in daylight.

At this point you will learn that astronomical telescopes usually show an upside down image. There is a good reason for this- erecting the image needs more bits of glass in the light path, which reduces the amount of light and increases aberrations. Even if this is only slight, astronomers prefer to avoid it, and they don't really care which way up the Moon or Jupiter appear. It is possible to fit an erecting prism or eyepiece to most astronomical telescopes, and some of them come with one, but one wouldn't bother to do this with the small finder scope.

Once you have done the above, you can try the scope at night, on an easy to find bright object like the Moon. Looking at random stars will probably be disappointing, as they don't look different under magnification. You will have to find planets, star clusters or nebula to see anything interesting. You will also find the the object you are looking at swims out of the viewing field, and you must continually move the scope to follow it. This will be more pronounced at higher magnifications. Again, use the least powerful eyepiece. Small scopes are often advertised as having unrealistic powers (300, 500) which can never be practically achieved. You just get dim blurs.

There is an excellent website for beginner telescope users at THIS LINK

Jan 06, 2011 | National Geographic 76AZ (525 x 76mm)...

2 Answers

Hi i have an optus telescope when i find a star in my view find or the spacestation orbitating the earth i find it in my view find and when i look through the lens on the scope i see notting and i have...


Your finder is not aligned with your telescope. During the day time focus on a distant small object with the telescope-- then without moving the telescope adjust the crosshairs in the finder to match the telescope.

Dec 27, 2008 | Optics

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