Focussing problems

[Deacon]

Hi

Im having trouble focusing my scope on objects in order to align my finderscope!

I manage to collimate the mirrors using a hotech but I can't focus on objects through the finder.

Can anyone help. The scoop is a skywatcher 8imch don.

Thanks

Deacon

[Tinker1947]

You may need a extension on the focuser.......

[RichM63]

Aligning finder scopes is best done in the day time.

You point the OTA at a very distant object and focus.

Then you move the finder adjuster screws until you see the same object through it.

If your finder is not focused at all, check that you have not accidentally unscrewed part of the tube assembly.

Cheap finder scopes are fixed focus/magnification and seem to be generally regarded as mediocre.

(ps, adding general location details to your visible profile can help you to receive localized help).

[mikeobrien]

Is it the main scope or the finder you can't focus?

[ronin]

What is it that you are trying to focus the scope on?

If it is less then one or two miles away you may have problems.

They are not intended for objects much closer, think about it, the moon should be the closest thing that you focus the scope at. :grin:

[Deacon]

I'm trying to focus on an object in order to line up the finderscope. Sub Giant has probably hit the nail on the head as I am trying to focus on things that are closer than 1-2 miles. The problem is that my back garden has quite high fences and I've not really got many distant objects to focus on.

I tried to do this in the afternoon but having no joy I got fed up and packed it away!!

[John]

Astro scopes frequently have a "closest focus" that is a good hundred feet away or more. You could wait until an easy to find object such as Jupiter or the Moon are in the sky and use that if you can't get a suitable terrestrial object.

[Deacon]

Great I'll try that thanks

[Warped Drive]

If you live in a two story house, do you have any better views of distant objects from a front or back bedroom window. This is what I had to do as I had the same problem in my back garden not being able to see anything terrestrial that wasn't more than a couple of hundred feet away. This might not be as easy with your 200mm Dob as it was for me with my 130p but may be worth a look at.

[Deacon]

Hi warped

I live in a ground floor flat so I'm pretty limited to what I can focus on.

Thanks for your help.

[keithatrochdale]

Pop the scope in the car during the day and go somewhere where you have a view. Try looking for high ground.

Focus the main scope on something distant (use a low power eyepiece), we use pylons about 1/2 a mile away and then adjust the finder scope so it is on the cross hairs or red dot. 

Then try something further away and repeat, then use a higher power eyepiece - job done.

If you are near us, pop up and we will help you sort it.

[Night Hawk]

I have same scope as you. The first few times I aligned my FS I focused on a nearby TV aerial from my bedroom. Started aligning using 25mm EP,then used my 10mm to fine tune. But tbh I've never looked back since I got my Telrad. I align using polaris ensuring that its centered in my ep and Telrad. I then will align my FS. Good luck.