terrestrial clarity

[rightguard]

living on the 6th floor in halls i am often tempted to use my scope to look across the landscape.

There's a building in the distance with fujitsu written on it. After much searching on google maps / streetview I found out it was in bracknell which is ~ten miles away from reading.

The thing is, when using the 6mm skywatcher uwa ep I cannot get a nice sharp focus on the wording 'fujitsu' - I know im looking through a window but still. Same with a 9mm. Had to use a cheap 25mm uwa to get focused enough to read it

If it cannot achieve a nice focus from 10 miles away, how on earth is it supposed to perform well on planets?

I checked collimation, all is well.

Scope is a 200p on a heq5, so a 6mm isnt breaking the limit of the scope

Anybody hazard a guess?

thanks,

tom

[Stephen]

I was under the impression it's not designed to focus on objects close to you - it's designed to focus on things millions and millions of miles away

[rightguard]

so I shouldn't worry? It got me thinking tho, cos the moon always looks cracking even with the 6mm, and I would've thought it could handle 10 miles?

[Mr Q]

Looking through any medium other than air will effect the image. When looking through a window pane (even a single pane), the light gets distorted and the higher the magnification used, the greater the distortions. The distortion gets to a degree that no longer can a focused image be had. Add to this the swirling air as it rises/falls when near the ground (causing a mirage effect), Its a wonder you can see anything in focus through a window above say 2 or 3 power of magnification.

Telescopes (and most binoculars) are designed to be used out doors, where the only thing between you and the object being observed is air and the steadier the air is, the steadier and more focused the image will be. It would be nice to observe the cosmos from inside a comfy room and through a window but things just don't work that way when it comes to the physics of light waves through anything denser than air.

Hope this answers your question without getting too technical.

[John]

It could be the window glass that's messing things up - two bits of glass if it's double glazed.

The 9mm and 6mm UWA's are not bad eyepieces although an F/5 scope is stretching them somewhat. They should be clear enough in the central part for the field of view.

It's an astro scope though so judge it by it's performance on astro objects - not viewed from the 6th floor and though windows of course !.

[rightguard]

double glazed windows yes.

Always take scope outside for normal use of course

thanks for the replies

tom

[umadog]

Also, you're pointing the scope at a target near the ground and during the day, when the air is most turbulent. The air turbulence will mean awful seeing. I do solar observing and it's a rare day that I can push more than 60x. The sun is obviously higher up than your building, so less near-ground air to punch through. You will do planetary observing at night (obviously) with the planet high in the sky. Views will be better. Remember that in optics it's the angle of the light rays that rule, not the distance of the object per se.

[ronin]

Optically it should focus on the writing, the difference between something at infinity and at 10 miles is just 0.0625mm difference in the focal plane.

So the window is the most probable culprit.