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I have been trying to collimate my newton f5.

And I think it´s pretty much with in the tolerances.

But when i turn it towards a tree or a building in the distance and focus, in the image I see the spider reflecting.

I have to have my eye pressed against the okular to avoid it. And I cant remember that it was like this before.

Is this because I´m trying it in daylight, if so, does it dissapear in the dark?

I followed a guide and it does not mention this fenomenon. Its just lika a vauge glare in the center of the lens.

Starting to get dark in a week or two so I want the scope to be in prime condition.

I have buildt an extremly sturdy case, so I will probably not need to collimate it so often,

Two pictures below just to show u guys.

Me and my cousin build it. It´s an old case from the army, it originally held a distance measurer

Anyone here that wishes to weigh in, be my guest.

/Christian

(Sorry for my second grade english, I´m a swede after all and we speak swedish =)

DSCN2591.jpg

DSCN2594.jpg

Edited by albusdlx

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I am guessing that the tree/building isn't far enough away.

When this happens the focuser has to be moved outwards a fair bit and then the image of the spider, somewhat blurred, can come into the image that is formed.

If you try the moon then I suspect that the focuser will have to be moved inwards by 10-15mm and the spider image will disappear.

Could find a tree that is further away as well.

Your English is better then many on here who are English.

Does the dog guard the scope ?

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I am guessing that the tree/building isn't far enough away.

When this happens the focuser has to be moved outwards a fair bit and then the image of the spider, somewhat blurred, can come into the image that is formed.

If you try the moon then I suspect that the focuser will have to be moved inwards by 10-15mm and the spider image will disappear.

Could find a tree that is further away as well.

Your English is better then many on here who are English.

Does the dog guard the scope ?

He guards his master =), but on the picture he´s just beeing lazy.

Ok, thanks for the answer. And you are wright, the focuser is high, like 1-2 cm from absolute max.

If the weather stays the same I could try it out tonight and test out your theory.

I measured out, and made my own centermark yesterday,

I´m about to buy a cheshire collimator.

Seems to be the easiest way for a noob like me.

This will only be my second season.

But I´m already contemplating getting a bigger scope.

We´ll se. This will do for now. :)

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Curious how far away the tree was, figures for your scope would imply only 50-60, possibly 80, meters or thereabouts.

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Ï would say about 50-70 meters. Probably closer to 70. The thing is it did not matter if i used the 20mm or the 32mm ep. Same story all the same. It´s not like the image gets detroyed, but it´s annoying. I could take out it now and test on something a bit further out. See if it helps. And another thing, I can see the edge on one side of the secondary mirror, but with the c-cap it looks good when i cover the main mirror. It´s in the middle of the focuser and a more or less perfect circle. I think that the main mirror need adjustment, but then the central mark would not appear to be centred in the ep.

Maby if i reset the main all together and try to adjusting it again?

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I can focus it. But in the middle of the lens it appears to be slightly out of focus. Se if I can capture an image of this

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About 150-200 meters to the balcony from where I stand.

Something between this: ((look at the satellite dish)

DSCN2601.jpg

And this: (top right of the dish)

DSCN2599.jpg

And this is how it look in the focuser. Not easy to take a good picture, holding it straight and steadyby hand and all. But you can see that it does not look terrible...

DSCN2606.jpg

Edited by albusdlx

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Very sturdy looking case :) Looks like you have a rocket launcher in there hehe

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Very sturdy looking case :) Looks like you have a rocket launcher in there hehe

And it´s sealed with silicone = dust and waterproof :)

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Hi!

Your collimation isn't terrible, but there's room for improvement. :) Here is a collection of useful links: http://www.physiol.ox.ac.uk/~raac/collimationLinks.shtml The second link (about secondary placement) shows you what to look for in the eyepiece. You'll get that darkening in the centre of field regardless. The third link down most clearly explains the steps of using a cheshire/sight-tube tool.

It's normal to see the secondary obstruction during the day. You are using lower power eyepieces which produce a large exit pupil and so a large image of the secondary obstruction. Your pupil is small during the day and so the size of the secondary obstruction image approaches the size of your pupil (and also your camera's iris, it seems). As a result, you will see a darker region in the centre of the field of view. With higher power this should become less noticeable. When observing at night your eye's pupil dilates and the darkening at the field centre becomes far less pronounced. The darkening is not related to your scope being collimated or not.

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Hi!

Your collimation isn't terrible, but there's room for improvement. :) Here is a collection of useful links: http://www.physiol.o...tionLinks.shtml The second link (about secondary placement) shows you what to look for in the eyepiece. You'll get that darkening in the centre of field regardless. The third link down most clearly explains the steps of using a cheshire/sight-tube tool.

It's normal to see the secondary obstruction during the day. You are using lower power eyepieces which produce a large exit pupil and so a large image of the secondary obstruction. Your pupil is small during the day and so the size of the secondary obstruction image approaches the size of your pupil (and also your camera's iris, it seems). As a result, you will see a darker region in the centre of the field of view. With higher power this should become less noticeable. When observing at night your eye's pupil dilates and the darkening at the field centre becomes far less pronounced. The darkening is not related to your scope being collimated or not.

Thank you for explaining this. The camera showed more or less of the dark area depending how much i zoomed in or out. It´s a normal digital camera with 21x optical zoom. A nice compact but nothing more. And yes, you are wright. I tested it out in the dark and it felt alot better. Since my 32mm and 7mm Ep´s are multicoated i thought that reflections were abolished, it seems not to be the case. And the longer from the Ep, the clearer the spider gets. Say 20 cm and i se it clear as day in the middle of the lens. But perhaps all of this is normal when I work on it in daytime.

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How is your scope by the way? Im wondering if to buy the same model as a first scope.

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Since my 32mm and 7mm Ep´s are multicoated i thought that reflections were abolished, it seems not to be the case. And the longer from the Ep, the clearer the spider gets. Say 20 cm and i se it clear as day in the middle of the lens. But perhaps all of this is normal when I work on it in daytime.

What reflections are you referring to? The purpose of the coatings is to ensure good light transmission. When light enters a glass surface most of it is transmitted but some is reflected. The reflected light is considered lost. The coatings reduce the amount of reflected light and so improve transmission and reduce light loss.

Each eyepiece has a fixed position, or distance (termed the "eye relief" http://en.wikipedia.org/wiki/Eye_relief), at which you position you eye for viewing. With modern eyepieces this is about 10 to 20 mm. It is at the this range that you should be evaluating the eyepiece. You know you're at the right distance because it's the point at which you see all of the field of view. You will never be viewing 20 cm from the eyepiece because out there you are missing most of the field of view.

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