Focus question

[Dindsy]

Hi,
In my quest to focus my camera and take pcitures I thought to check my camera focusing in the daylight. So this morning I set it up and tried to focus on a tree about 1Km away. It didn't focus very well so I went back to basics and tried to focus the telecsope itself (without camera) on the tree. I couldn't get a very sharp image. it was almost focus but still not sharp. Is this normal or is there something wrong with my scope.

Details are:Skywatcher 150mm, focal length 1000mm, 25mm eyepiece.
It was morning and the scope wsa inside looking out through a window.

thanks

[iceman (Mike)]

Sounds like collimation may be a problem?

Have you ever collimated? Is a short-tube newt with the built-in barlow?

[Dujon]

Dindsy, were you looking through the glass pane of the window? If you were then try opening the window (no fly screen) and try again. If you can't do that then try and take the 'scope somewhere you can do the same test with nothing between the 'scope and the target.

Even clean window panes are far from optically pure, regardless as to how they look to your eye.

[Dindsy]

It was through the glass. no flyscreen.

I can, and will, do it with window open. Should it be crisp?

[chunkylad (David)]

You should be able to achieve a crisp focus under the above conditions (no glass and no flyscreen between you and your target).

If not, see Iceman's post above.

Dave W

[huckabuck]

dindsy, the temp difference along with the uplifts and and such surrounding the house will cause the same effect as REALLY bad seeing. also the glass will effect the magnification in a very bad way. take it outside!!!

[Dindsy]

I will definitely have another go outside.

It is a Newtonian reflector. Long tube. No Barlow.

It has never been collimated. I know this because I have no idea what that means even though i have seen it mentioned a lot.

cheers

[[1ponders] (Paul)]

What sort of camera is it Dindsy and does it have a Diopter adjustment at the top right corner of the viewfinder window?

[iceman (Mike)]

You definitely need to learn collimation if you own a newt. You will never get the views you hope and expect until you learn to collimate, and can ensure that your collimation is correct.

Where abouts in Sydney are you?

You should endeavour to come to our Kulnura observing night on the 17th Feb - you'll get help from experienced people about collimation and we can show you how to do it properly.

In the meantime, do a search on collimation and there's a tonne of threads discussing the hows and whys.

Collimation is critical. It's a must-learn skill for anyone with a newtonian.

[Dindsy]

I'm in Epping, North west. How do I find out about the observing night in Kulnura.

I was hoping that Collimation was for advanced people doing fancy stuff so I'd ignored it. But I guess I will start searching.

My camera is a Nikon d100. It does have a diopter adjustment. Never thought to use it though.

the annoying thing is that I've been hunting around for hints and found people with fantastic d100 images on what (to me) appear to be smaller aperature scopes. So I will perservere.

cheers

[Dujon]

I am assuming, Dindsy, that you have now done the outside test?

If so (and in no way manner or form did I mean in my previous post to counter Iceman's comments regarding collimation) and you still cannot attain a decent focus then collimation is probably the solution.

Please, do not be put off by the 'jargon' used in astronomical fora such as this. Collimation is simply the lining up of a telescope's mirrors or lenses. It is not hard, but it can be fiddly. You do, of course, need to get a feel as to what this means.

If you are not fully cognisant of the ins and outs (or the jargon) I recommend that you view this:

http://www.andysshotglass.com/Collimating.html

"this" is a short (but almost 4mb) explanation of collimation. If you can afford the bandwidth it's well worth watching.

[Dindsy]

John,
Thanks for that video link. It explains collimation and shows how to do it. Awesome. I'm still scared stiff to touch screws on my OTA but I will have to get a collimator. Gee, another excuse to buy toys how sad

Haven't done my outside test yet, pesky visitors...

[Dindsy]

I did my outside test and the telescope focus is sharp. That's one less problem.

However, I'm not sure if its a meaningufl test without a collimator but I looked into my focuser (without and eyepiece) until my pupil was in line with the primary mirro dot. Doing this it seems that the collimation is out quite a bit. the secondary mirror circle is not centred.

Anyway I'm getting a collimator so will know for sure soon.

As for the camera. When I have the eyepiec in the camera adapter, attached to the camera and mounted in the focuser I still can't get shar images. Even though the camera viewfinder shows a sharp image. hmmmm

[Dujon]

Great news, Martin. You are now half way 'there'.

Don't thank me for the link - I dug it up somewhere else on this site.

I'm sorry, but I cannot help you with your camera question as I have not used a camera of any description on my 'scope. There are many people on this forum who do use cameras on a regular basis so I'm sure you will receive a sensible answer from one or more of them.

Good luck with the collimation exercise.

[Dennis]

Originally Posted by Dindsy

I did my outside test and the telescope focus is sharp. That's one less problem.

As for the camera. When I have the eyepiec in the camera adapter, attached to the camera and mounted in the focuser I still can't get shar images. Even though the camera viewfinder shows a sharp image. hmmmm

Hi Martin

This description reads like you are jumping in at the deep end, where even experts fear to tread…..

Using the DSLR (without lens) + Eyepiece Projection Adapter + Eyepiece gives you a highly magnified image, depending upon the focal length of the eyepiece used.

The stars may appear to be in focus on the viewing screen, but it is likely they will not be at the best focus, so in the final (> 3000x2000 pixel) image they will look blurred.

Also, if you press the shutter release manually, your contact with the release button is sufficient to knock the camera and ‘scope set up, which will trail or blur the stars, as will the vibrations of the DSLR mirror as it flips out of the way, unless you have a mirror lock up function.

If that is not enough, then it is likely that your mount (if it is tracking) would not be up to recording the star image as a dot for exposures of more than 2 or 3 seconds using eyepiece projection.

None of this is either operator or equipment error; it is just that you are pushing the envelope when using eyepiece projection.

Cheers

Dennis