Society for Popular Astronomy

Help i cant see a thing
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Author:  melly [ Sat Aug 01, 2015 2:54 am ]
Post subject:  Help i cant see a thing

I have purchased a nexstar 8se. I need to align it during the day with an object. I locate the object through the red dot finder but on the main eye piece i see nothing.
I searched for the object on the main eye piece but you still cant see anything. I played around with it and i can see the colors of objects, blue shade sky, green shade of grass, but you cannot see a thing. I turned the knob to focus but nothing at all. Not only i cannot find the object i centered on my red dot finder,i cannot focus my eyes piece on anything at all. not a thing.


Author:  Brian [ Sun Aug 02, 2015 7:29 pm ]
Post subject:  Re: Help i cant see a thing

Hi Melly, and welcome.

The best advice I can give is "don't panic" :D You have a very capable telescope there but it will take a little bit of getting used to.

To start with you will need to align your red-dot finder with your telescope field of view, not the other way round. The field of view of your telescope is very small, even when using your longest focal length (lowest magnification) eyepiece. So you need to get an object into your lowest magnification eyepiece and focus it. The best type of target to use is a distant chimney, aerial, streetlamp etc. Aim for something a mile or so away as your telescope is designed to see targets that are at infinity rather than close to. This type of target doesn't move so is easiest to lock onto. Currently the full(ish) Moon is well placed as a target as well but of course it will move and you will need to have the telescope track it. It's so bright that even when it's not actually in your eyepiece you will know its just outside it because of the bright glare it gives.

Schmidt-cassegrain telescopes like the 8SE have a very large range of focus. Focusing is done by moving the main mirror back and forth using the knob at the back of the optical tube. In order to get your target in focus you will need to turn the focus knob from completely clockwise to completely anticlockwise. Somewhere in that travel you will see the target pop into focus. You could count the number of turns so that it's easier to locate focus next time round. Bear in mind that focus will appear quickly and then disappear just as quickly so a light touch on the focusser is needed.

When you have your target in the eyepiece, then you can adjust the pointing of the finder to be at the same place. Thereafter you should be able to use the finder to get close to other targets, close enough to get them into the view of your lowest magnification eyepiece. That's all the finder needs to do.

Hope this will get you started. Look forward to hearing how you get on, and please don't hesitate to ask again if the problem persists or the are other thing we can help with,

Best regards,

Author:  melly [ Mon Aug 03, 2015 2:58 am ]
Post subject:  Re: Help i cant see a thing

Thank you so much for your reply. Tomorrow I need to figure out where I can set the telescope to find an object clear of at least a mile(that is not in the sky). It's been a little intimidating and I don't want to lose interest in the scope. I am going to attempt again and will fill you in. So you are suggesting I change the eyepiece that is 25mm to a lower magnification?

Author:  David Frydman [ Mon Aug 03, 2015 5:24 pm ]
Post subject:  Re: Help i cant see a thing

. Hi melly,
. The 25 mm eyepiece gives a magnification of 80 times. The field of view is about 35 arc minutes, which is just slightly bigger than the moon.
If you have a 40 mm eyepiece, use that, if not you just have to use the 25 mm to set up the finder scope accurately.

Once you realise how small the field of view is with a long focus telescope, you will understand why you need to look at something 1 mile away, or use the moon.

Regards, David

Author:  Brian [ Mon Aug 03, 2015 5:37 pm ]
Post subject:  Re: Help i cant see a thing

Hi Melly.

If you are having difficulty locating a suitable distant target from your observing site then you can use a closer target to get the finder set up initially. I would make use of what's available. The further away the target, the more accurate the alignment process, but you can always refine that alignment in future if a better target presents itself. In fact you may find that you need to tweak the finder alignment each time you set up the telescope.

The 25mm eyepiece should be fine for initially locating your targets. The only function of the finderscope is to place the target into the field of view of the 25mm eyepiece. The target doesn't need to be in the centre of the eyepiece, just in view so that the telescope can be moved using the handset buttons to do the centring. Then you can change to a higher magnification eyepiece if you want to, to get a closer view.

Have a look in the Gallery section here. You will find that at least a couple of posters there are using the Nexstar SE telescopes. Hopefully you will get some hands-on advice from that direction as well,


Author:  melly [ Mon Aug 03, 2015 11:31 pm ]
Post subject:  Re: Help i cant see a thing

Thank you Brian
Thank you David

I am going to attempt tonight to focus on moon. Wish me luck!

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