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Hello all,

I always been fascinated by astronomy and finally purchased a celestron nexstar 8se. Setup went smoothly but I'm a little stuck on the lens. I attached the star diagonal to the telescope and focused in on an object. I was able to see a part of the leaf on the plant in my house and I attached a picture of that. Moving the telescope left and right allowed me to see other things. I then took out the 25mm lens and can see through that when not attached to the telescope. I can see my sandals and feet through the lens and attached a picture of that. I then inserted the 25mm lens into the star diagonal and that's where all hope gets lost. I see white (assuming that's my wall) and yes the cover on the telescope is also off. No matter where I move the telescope. All I see is white. I tried last night in clear skies and pointed towards some clear stars using the skyportal app to align but I didnt see anything except pitch black through the lens. I also played with the focus but nothing. Am I doing something wrong, I would think the 25mm wouldnt be so zoomed in that I cant see anything? Thanks for any help you can provide me. Looking forward to exploring!!

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All. Thanks again for all your advice. I went back out in the nice sun (on eastern time). I turned on the finder scope and pointed it to trees behind a home about a half mile away. I could tell it was

It's very much to do with the sensitivity to brightness of the viewers eye.  I can look at the Moon with a 20" without needing any filter whereas my wife would need sunglasses to look at a full Moon w

The vast majority of the time that I'm observing the moon, I am using quite high magnifications, which has the effect of dimming the brightness of the image making it comfortable to observe for extend

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This type of telescope (An SCT) , has quite a narrow view and is often used for small targets like planets.

It will not show much unless you are close to the focus position.

It would be best to try at night with a bright easy to find target so you can find the focus position , the moon is ideal for this.

Attached is the size the moon will look using your 25mm plossl, but the moon is very small in the sky ,

(the yellow circle is the view in your viewfinder)

Are you using a finder to get close to your target.

As the view is so narrow unless you are in exactly the right spot you will miss the target which is why a finder is fairly important with this kind of scope

(but you need to align finder and scope together)

 

The blue circle shows the view through an average finder.

 

Also your telescope is not designed to focus on close objects , to look for focus during the day try to find a far off target a few miles away , like a church steeple or hilltop

 

 

 

If you have a GOTO mount you must polar align then do a star alignment before the GOTO will find your targets.

Image11.jpg

Edited by fifeskies
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Try to focus on something out of your window that is a far away as possible to see, then adjust your focus (which has quite a lot of range in this type of scope) till you achieve focus OK. If your finder is aligned this will help you aim the scope, but if not try to see the image of the object in view as best as you can without the 25mm EP in place. You should be able to see if you  are on or near alignment with the object. Once lined up with a distant object you should be able to then adjust you finder scope so that it is aligned with your telescope to make it easier to get things in view. 

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Thank you both for your input. I was not using the finder scope so will try to align an object far away or a star tonight with it first and then try to find it through the telescope. That would have helped If I tried that. Your picture of the moon is something I was expecting to see but the moon wasnt out last night. I think when it's up there, using the finder scope to find the moon and then the telescope will make it better. 

I need to play with the focus, that might be also why I'm not seeing anything as you mentioned it has quite a lot of focus and I'm not going far out as I should. As a backup, I ordered the starsense auto align and have the skyportal wifi so will try with those two to see if it can make things easier. In the meantime I'll try to find far away objects to see if I can locate them using the scope once it gets dark here. Again, thank you both for the quick replies!

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There is a lot of focus travel on the Schmitt Cassegrain scope, keep winding the focuser gently and you will get there. As above, a distant target is needed. As the SCT uses a moving mirror to focus, there is a HUGE focal range, the advantage being that whatever accessories you have in the optical train, it can reach focus. Unfortunately you won’t really know which ‘way to turn’ so to speak until you get close to focus. Once there though you’ll find you won’t have to turn it that much to stay in focus.

PS the minimum target range to reach focus would probably be around 50 metres (I’m sure I’ve managed to get a pigeon in view at this range whilst messing about in daylight hrs). You won’t be able to focus on anything indoors.

Edited by Alkaid
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Personally, I'd take the scope outdoors during daylight and get used to the focus on distant objects (maybe buildings at the end of the street or somesuch) NOT the sun, obviously.

With your 25mm eyepiece in, and aimed at something like a distant building, move from one end of the focus to another and you WILL finf the focus point somewhere. As others have said, the range in the SCT is massive and you'll feel like you're turning that knob forever.  When you've got focus, play with the scopes movement and get your head around how much of the object you're seeing and how the movement works. On my 9.25" a house brick fills the view at around 200m.

While you're playing, set the finder scope up. Aim the scope at a specific point (TV aerials are my favourite), then twiddle with your finder until you can see the exact same thing bang in the centre. For exatra points put a more powerful eyepiece in the telescope, make sure the image is in the centre and check the focuser again. That will make finding objects in the sky so much easier.

When you do get out under the sky, the focus will be at a different point than viewing terrestrial objects, so there's more focus winding to be done. However, once you've focused on one thing, focus on other objects, or with different eyepieces, or different weather conditions, will only be a few turns, if that.

If you're looking at a star in the finder and the view through the telescope looks like a white dinner plate with a black hole in the middle, that's normal (and usually referred to as "the donut"). What you're seeing is the star out of focus and the black part is the shadow of the central obstruction (the secondary mirror in the middle at the front). Moving focus one way or the other will reduce the size of the donut until it focuses into a beautiful star.

StarSense is great, but it does add a level of complication to start with and takes a bit of setting up and getting used to (probably a night or two, truth be told). Once that's done it's terrific and allows alignment in under five minutes. But to start with I'd play with the scope without it for a while and get used to slewing around and using the finder.

Oh, sorry. Welcome aboard SGL 🙂

 

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All. Thanks again for all your advice. I went back out in the nice sun (on eastern time). I turned on the finder scope and pointed it to trees behind a home about a half mile away. I could tell it was focused on something brownish because I was no longer seeing the blue sky. I started from the knob all the way to the left and slowly starting turning it clockwise. After some focusing I could clearly see the leaves moving in the wind on the tree in crisp quality. I then started to explore with the knob and what I can see with the focus and got the hang of the scope finder and how to find an object. Looking forward to trying it out tonight! Cant wait to see the moon. I also got the 2x barlow lens and the celestron zoom eye peice that goes from 8mm to 25mm so once I get familiar using the basic lens and finding stars, I'm going to explore with the other lens and really go into detail. I'm so thankful to have found this community and I appreciate all the help you given to this newbie!! I am going to spend quite some time on this website and learn as much as I can. 😄

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The 8SE on GoTo is a fine telescope.  You'll soon get used to it.  At first, you can align on a planet or one star, esp. if you go for targets close by.  To get more field of view, you could later get a 2" diagonal and low power 2" eyepieces.

Have fun!

Doug.

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I remember those days well as my first scope was a second hand LX200GPS 8". My first attempt was on a freezing cold, crystal clear night. Fingers numb as hell, feet like blocks of ice!  I was lucky that evening. My first "star" I tried to get aligned on and in focus turned out to be Saturn - can you imagine how that felt! Well, the rest is history.

A word of warning though - this hobby can get expensive really, really quickly. Take care with purchases, don't buy cheap eye pieces - there is no cheerful when buying cheap.

A couple of things to consider - if you want to view the moon, get a "moon filter" - sounds stupid, but at these magnifications, it's as bright as hell and secondly if you live in an area that gets dew, I'd suggest getting either a dew shield or straps. Nothing like dew to cut short a clear sky session! (a dew shield can be made cheaply though if you are that way inclined)

Have the best of fun out here on clear nights, and back here on overcast nights

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Hi and welcome to SGL from Wet Wales

 

A tip for using the Finder is to keep both eyes open when you are looking through the Finder.

Both eyes open works in the same way as using a range finder.

Use the left eye to look at your target and the right eye to look through the finder, then just move the scope until they come together.

Good Luck

 

Pat

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On 16/11/2020 at 00:25, tenpinmark said:

if you want to view the moon, get a "moon filter" - sounds stupid, but at these magnifications, it's as bright as hell

I'd avoid a moon filter, and invest the money in a low magnification eyepiece. Of course, the moon is rather bright at low magnifications (but not brighter than observed with naked eyes). But, as detail is the most interesting thing, you will soon switch to higher magnifications, which will dim the apparent brightness rapidly. My moon filter is one of the least used items; and I'm observing with scopes up to 18".

Stephan

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57 minutes ago, Nyctimene said:

 (but not brighter than observed with naked eyes).

sorry but that is not the case for me

when my 10 inch scope gathers all the light from a 10 inch circle and pushes it through my tiny 5mm eye pupil circle I can assure you it is far brighter than looking direct at the moon without a telescope , especially if the magnification of the eyepiece is low.

 

It allows 2500 times as much light through so even at higher magnification it is still uncomfortably bright

 

Without my 10% moon filter I cannot bear to look through my big scope at the moon.

I get the large dark "sunspot" effect in my vision if I try it like a bright sun will do during the day, that never happens looking at the moon with a naked eye.

 

I don't feel I need the filter with my smaller refractors at high magnification however unless the moon is near to full.

 

Image11.jpg

Edited by fifeskies
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The  areal brightness of any extended sky object (galaxies; moon) remains the same, when viewed through a scope - it's just a much larger part of the retina covered by the enlarged image, creating the impression of higher brightness.

Stephan

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8 minutes ago, Nyctimene said:

The  areal brightness of any extended sky object (galaxies; moon) remains the same, when viewed through a scope - it's just a much larger part of the retina covered by the enlarged image, creating the impression of higher brightness.

Stephan

 

which is why the "perceived" brightness gets uncomfortable and a moon filter can be an asset.

The energy falling on the retina is far larger.

 

The common understanding of brightness will be described as an image "too bright to look at" without a neutral density filter to reduce it (to 10%  typically)

 

A full moon in an 8se will be too bright for many viewers without a moon filter.

I personally find it helps to see the moon as well , for me the contrast change brings out more lunar detail.

 

Edited by fifeskies
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I observe the moon regularly with my 12 inch dobsonian and don't find the need to use a moon filter :dontknow:

If you find it uncomfortable by all means do though. I have a moon filter with me at outreach events in case any one looking though my scope would like to use it.

 

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It's very much to do with the sensitivity to brightness of the viewers eye.  I can look at the Moon with a 20" without needing any filter whereas my wife would need sunglasses to look at a full Moon with the naked eye!    🙂

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As aperture goes up I am fairly sure the exit pupil will increase wider than the eye will open to under a bright view of the moon.

So after a while there will not be any brighter a perceived image as much of the light is being lost, but there will be finer detail resolved in the bigger scope.

This will also vary with age. (older among us have a smaller maximum iris opening)

 

The use of a moon filter has another benefit if you are going to other objects after the moon as dark adaptation is not lost as badly.

Edited by fifeskies
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5 minutes ago, Peter Drew said:

It's very much to do with the sensitivity to brightness of the viewers eye.  I can look at the Moon with a 20" without needing any filter whereas my wife would need sunglasses to look at a full Moon with the naked eye!    🙂

Its the same with sound  🙄

What I consider quiet can be regarded as a cacophony by some others 

 

Makes creeping about in the middle of the night a challenge at times (for astronomical reasons I might add).

 

Edited by fifeskies
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The vast majority of the time that I'm observing the moon, I am using quite high magnifications, which has the effect of dimming the brightness of the image making it comfortable to observe for extended periods.

I would not start looking for targets that need dark adaptation after observing the moon. Usually because such targets are not at their best anyway when the moon is in the sky !

 

 

 

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1 hour ago, fifeskies said:

sorry but that is not the case

when my 10 inch scope gathers all the light from a 10 inch circle and pushes it through my tiny 5mm eye pupil circle I can assure you it is far brighter than looking direct at the moon without a telescope , especially if the magnification of the eyepiece is low.

 

It allows 2500 times as much light through so even at higher magnification it is still uncomfortably bright

 

Without my 10% moon filter I cannot bear to look through my big scope at the moon.

I get the large dark "sunspot" effect in my vision if I try it like a bright sun will do during the day, that never happens looking at the moon with a naked eye.

 

I don't feel I need the filter with my smaller refractors at high magnification however unless the moon is near to full.

 

Image11.jpg

It can, in fact, be shown that the surface brightness of an extended object cannot be increased by a telescope. This is a rather surprising bit of science but also a misleading one since, subjectively, we don't see it that way. While it's technically correct that the surface brightness can't be increased, I've always found this to be a rather 'dry' point since, in order to see fainter objects, we need a bigger telescope. What's really happening is that a smaller telescope, in increasing the object's image size, is spreading the light out too far and dimming it. More aperture allows for the object to be spread out over a larger area without being so badly dimmed. So telescopes do make faint objects bright enough to see but they do it by making them bigger rather than brighter.

Olly

Edit: Think of a a rear bike light made of one LED. It won't be very visible at a distance. Add another twenty LEDs of the same brightness, and it will be.

Edited by ollypenrice
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6 minutes ago, fifeskies said:

Yes as much as I love the moon I sometimes resent its presence on the few clear nights we seem to get as it rules out a lot of other targets

It rules out extended deep sky objects such as galaxies and a number of nebulae types but asterisms, open and globular clusters, planetary nebulae, double stars, asteroids and the planets are still quite accessible in a moonlit sky :smiley:

 

Edited by John
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3 minutes ago, ollypenrice said:

It can, in fact, be shown that the surface brightness of an extended object cannot be increased by a telescope. This is a rather surprising bit of science but also a misleading one since, subjectively, we don't see it that way. While it's technically correct that the surface brightness can't be increased, I've always found this to be a rather 'dry' point since, in order to see fainter objects, we need a bigger telescope. What's really happening is that a smaller telescope, in increasing the object's image size, is spreading the light out too far and dimming it. More aperture allows for the object to be spread out over a larger area without being so badly dimmed. So telescopes do make faint objects bright enough to see but they do it by making them bigger rather than brighter.

Olly

Yes - Surface Brightness (brightness per unit area) is the same as with the naked eye, but the telescope enlarges the image, so the integrated brightness over that area effectively increases.

Doug.

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