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Old 14-10-2020, 07:31 PM
Mark.Tanner (Mark)
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Tiny circle on eyepiece

I've struggled finding anything in my Nexstar 8SE. This is a picture of the image coming out of the eyepiece during the day. The black dot is I believe a reflection of the mirror. But why is the sight so tiny??
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  #2  
Old 14-10-2020, 08:42 PM
alval (Alan)
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The black dot looks like the secondary mirror on the front corrector that folds the light back through the mirror to the diagonal. Its hard to tell from the photo but what eyepiece are you using in the diagonal?
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Old 14-10-2020, 09:04 PM
Mark.Tanner (Mark)
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Yes that's what the black dot is. I believe collimating it would get rid of that, correct? And it's a 25mm. There's no way I will be able to see anything in that tiny point of light haha.
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Old 14-10-2020, 09:39 PM
alval (Alan)
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Collimation? Is this a new to you scope? Unless its been damaged you should still get an image. Are you trying to focus on distant objects if they are to close it wont focus.
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Old 14-10-2020, 09:46 PM
raymo
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That is a bit odd, its pretty much what you would see through the focuser tube when there is no eyepiece inserted, or with just a Barlow lens inserted.
The glass seems to be awfully wide in that 25mm eyepiece. Whatever your problem is, collimating it almost certainly won't fix it. Really need
to see what you get outside at night.
raymo

Last edited by raymo; 14-10-2020 at 09:48 PM. Reason: more text
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Old 14-10-2020, 09:56 PM
SkyWatch (Dean)
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It looks to me like it is way out of focus: the black dot is the secondary mirror, which you wont see if you have an image focussed and your eye on the eyepiece. The collimation looks fine: the black dot is central as it should be. The white circle is the exit pupil of the eyepiece: this is the light that goes directly into your eye: your eye only dilates to about 2mm during the day, and up to 7mm at night, so any exit pupil that is bigger than that is simple wasted light. Have a look at this article if you are unsure about what this all means: https://en.wikipedia.org/wiki/Exit_pupil

As Alan pointed out, the scope is not designed to focus on nearby objects, so I think you need to point the scope at a distant object (say a tree on the horizon) and turn the focus knob until you see a clear image. You might have to turn it quite a way, and experiment with clockwise and anti-clockwise because I think it might be a long way out, and there is no way to tell which way from your description and image. Once you have focused on a distant object you will find that it is almost in focus for the stars too, so it wont need much more tweaking at night.

While you are at it, line up the finder scope so it too is centred on the same object, and lock the nuts so that when you point at something at night you will be able to find it...

Good luck,

Dean

Last edited by SkyWatch; 14-10-2020 at 10:08 PM.
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Old 15-10-2020, 10:09 AM
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mental4astro (Alexander)
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Mark,

I've been intrigued by your question here. I've also looked at the other posts that you have made because your question and comments in this thread have me puzzled and I wanted to get a better feel for your experience before offering some help.

Have you looked through a telescope before? I mean this sincerely because your comments come across as being from someone who does not know how to use one or what to expect from a telescope. I am not putting you down. That is something I never want to do. The telescope you have is a very capable instrument, but it can be very confusing with all its mirrors, peculiar apparent tiny round image seen so coming from the eyepiece. It all points to a total novice who has jumped straight into the deep end! Now we need to learn to swim

Before going any further, have you managed to get a nice, clear and sharp image from the scope? Have you managed to figure out how to focus it?

Nothing more. We really need to start from here. Like I said, I am not putting you down. I just need to know your level of experience.

Don't worry about strange words like "collimation". For now it means bugger all and has absolutely no impact on getting you going with the scope. This word only serves to confuse and create false impressions that only complicate things for a novice right now. This is obvious to me by your comment related to it. Forget about it for now. Let's get the scope working for you first.

Alex.
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Old 15-10-2020, 04:53 PM
Mark.Tanner (Mark)
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I've fixed the issue! As many commenters suggested it was a focusing issue. I now have the telescope focused on a distant object and aligned with the finderscope. It's all setup by a window to see some stars if they come out tonight and will take it out on the next clear night.

Your assumptions are right, Alex. I haven't looked through a telescope properly before (only ever mine, with the closest to a 'proper' view being terrestrial views an hour ago). I've done a good amount of research into the scope and how to use it and it all seems quite straight forward until I run into a problem that I can't Google my way through. Thanks for the help!
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Old 15-10-2020, 05:18 PM
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mental4astro (Alexander)
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EXCELLENT!

Now that you are treading water, now comes the time to aim the scope skyward!

To help you out with navigating the night sky, in case you haven't already done so, a phone app like Sky Safari is a great resource. They have a free version and a couple of paid versions. The free version is great to get you started. It will list the brighter stars in the sky and this will help you to locate the alignment stars.

Be patient with yourself here. It can be tricky at first.

You don't need to have the mount aligned to get your first view through of the sky. You can use the direction control buttons to move the scope about to view "manually".

Just to get you started, before attempting an alignment, locate Jupiter and Saturn on the app, then locate them up in the sky, and then move the scope (with the direction control buttons) to either one of these. They are very bright which makes them easier to locate and identify as being planets because when focused they will not be just pinpoints of light.

The only other button to look for on the handset is the "motor speed" button. Press that button and then the one of the numerical buttons. The higher the number the faster the mount will move the scope. To get the scope first pointing to the planets use speed number 9 to get the scope quickly up, and then press motor speed and number 5 to fine tune the pointing and move the scope when the object moves from the field of view.

Oh, and use the 25mm eyepiece here!!! It will give you the lowest magnification of your eyepieces, and it will be plenty to get you started with the planets. With your 8SE it will give you 80X magnification. The shorter the focal length of the eyepiece the greater the magnification, and the smaller the field of view of the sky it will give you, which right now is like using a wee straw to look through to find stuff in the sky.

This will get the ball rolling for you. The Moon will be visible next week, and Mars is rising in the east at sunset right now. Jupiter and Saturn are perfect to get you going.

Once you have these two under your belt you will be a hell of a lot more familiar with the mount when it comes time to start an alignment process and exploit its capabilities more fully

Alex.
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Old 15-10-2020, 08:28 PM
Mark.Tanner (Mark)
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.Thanks Alex!

I've got Stellarium already. That has been pretty incredible! I'll certainly be viewing planets/stars manually initially (I've got to do that to align the scope anyway!).

Thanks for the suggestions re. Jupiter and Saturn. Looking at a website showing when planets rise over the horizon, it seems that Mercury, Mars, and Uranus are the only ones visible before 2:30am so will have to stuck with them. I can't wait to see Mars and Saturn though!

Thanks for the tip re. mount movement speed! I didn't know it could do that.

Yes I'm using the 25mm eyepiece. I've got some smaller (more powerful) eyepieces but probably won't need those for awhile!
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Old 15-10-2020, 08:44 PM
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Umm, Jupiter & Saturn are up early in the evening...

You might want to check you have the right Lat/Long & date/time entered into Stellarium...

Mars is up pretty early in the evening too... even way down south in North Antartica where you are located..

Not sure what website you are looking at but, I googled planet rise times for Hobart & came up with this...

https://www.timeanddate.com/astronom...stralia/hobart

Cheers
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Old 15-10-2020, 09:15 PM
Mark.Tanner (Mark)
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That's the website I'm looking at. Jupiter and Saturn rise at 2:29am and 2:51am respectively. Not what I would call early evening haha.
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Old 15-10-2020, 09:43 PM
raymo
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Those times are the times that J and S are visible until, not from when.
raymo
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Old 15-10-2020, 10:18 PM
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Quote:
Originally Posted by Mark.Tanner View Post
That's the website I'm looking at. Jupiter and Saturn rise at 2:29am and 2:51am respectively. Not what I would call early evening haha.
As Raymo says, that's the time they are visible to not from... they actually rise in the afternoon...
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Old 16-10-2020, 04:24 AM
astro744
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Go out after sunset during the Blue hour onwards and face north then look straight up. (You may spot Jupiter a little earlier in the Golden hour but later is easier). Jupiter is the brighter one on the left (more west) and Saturn the other one.

They will be close together around Christmas above the horizon at sunset but at present are ideally placed for telescopic observation. Each day they move further west at the same time of night due to the Earths movement around the Sun and they also move against the background stars due to their own movement around the Sun.

Mars is on the horizon in the East at sunset. Give it an hour at least to clear any obstructions (depends on your locale). The higher you observe it the better. Itís a bright orange Ďstarí.

None of the above requires any tablets or computers. Enjoy!
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Old 16-10-2020, 06:38 AM
Mark.Tanner (Mark)
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Oh yes, you're right! Thanks, I'll try to find them tonight if the weather holds up
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