Webcam Focusing

[AJSullivan]

As I have mentioned in another thread (though it got a little long), I am having problems focusing my webcam. I only have a small scope ( see signature) and just bought toucam, and the adaptor. I set it up as the tutorial says which was excellent by the way.

I tried to focus on jupiter and could manage it. I needed to focus towards the scope more, but I had already come to the end, as in I couldnt physically turn the knob any more. The best result I could get was this:

Now i searched the net for ages to find an answer and the closest I could get was a 4/5 year old forum post, heres the interesting snippet:

"One problem often faced by owners of small reflectors is that the focal point of the optics is inside the focuser, to the point that even with the focus travel right in it is not possible to get a clear image onto the webcam's CCD. You could try determining the focal plane of your 'scope by placing a piece of tracing paper over the end of the focuser and then try to focus an image of the Moon onto that paper by racking the focuser in and out to the maximum travel. If you can't get focus this way then you won't be able to get an image onto the CCD without moving the main mirror up the tube a little."

OK well there you have it, any ideas? If it IS the mirror, I dont feel capable of doing this, therefore could i get an astro shop to do this for me? Is it expensive?

Alex

[legion48]

I had the same problem with a previous reflector. A shorter "low profile" Toucam adapter solved the problem for me. Follow the link and scroll down to the "Low Profile adapter".

http://www.astro-engineering.com/Adaptors/adaptorsforteles.html

[scotastro]

Legion48 got in ahead of me but I'll post anyway.

Your are correct in your thoughts - there is a lack of inward focus on your scope, but there might be other solution without moving the mirror.

What sort webcam is it and what adaptor are you using as there are different lengths. Sorry to ask this one but did you remove the lens from the webcam?

Any chance of some pics of the webcam and adaptor (sepately).

Mike

[AJSullivan]

Mike

I removed the lens and have set it up correctly. I followed step by step instructions from another astrophotography website. I am looking at this low profile one which looks interesting.

[Sam]

This is a common problem with reflectors and is certainly pronounced when imaging with a DSLR. There are a bunch of things you can try:

1. Buy a low profile focuser.

2. Move the primary mirror forward.

3. try and get the ccd chip closer to the focuser through a low profile adapter.

I couldn't afford a new focuser, an adapter wasn't going to help too much so I moved my mirror forward - basically collimated it forward by "extending" the screws with a small piece of wood attached to each screw - sounds dodgy but works very well.

Sam

[AJSullivan]

yeah the mirror thing sounds great..but I wouldnt have a clue where to start.

[PhillyDee]

If its the standard eyepiece adapter I can modify it at work by turning the lip off. Just make sure you tell me exactly what you want, oh, and it wont be anodised on the turned bit anymore. I can shorten it too, thats not a problem. Or jou could just File it off . . . .

[Kaptain Klevtsov]

Or use a Barlow lens. These usually need more out travel so it should work in your favour here as well as giving a bigger image scale.

Kaptain klevtsov

[barkis]

Alex,

Just wondering what the make of scope is you have. I don't suppose it's the type with an artificially extended focal length, which would already have a lens inside the focuser. It's just that sticking a Barlow in there might damage it, if it is of that ilk that is. Of course I am merely speculating.

A quick check on the specifications might reveal all.

Ron.

[Reggie]

If its that kind of focuser then surely putting an ep, barlow, T-adapter etc. would all damage the lens in the focuser.

[AJSullivan]

My telescope is in my sig. I have a barlow and it works really well so I dont think its what you are thinking of. Using the barlow does not help the webcam problem alas.

[barkis]

Moving your primary mirror up the tube seems to be the best solution, although another problem may result from doing that. If your secondary mirror has been designed specifically for your OTA, then moving the mirror may cause vignetting, resulting in light loss. The other option you have, is to fit a low profile focuser.

Is there no one near you who could make an on the spot assessment of the situation, and advise you as to the best solution.

Ron.

[daz]

My telescope is in my sig. I have a barlow and it works really well so I dont think its what you are thinking of. Using the barlow does not help the webcam problem alas.

Are you saying that you cannot achieve focus when using the barlow?

[Ant]

From a quick search online, this scope appears to be an F4. So it is unlikely to have the lens in the focuser.

So adding a barlow into the equation wouldn't harm anything, AND will push the focus point out (away from the scope).

I have a cheap 1.25" barlow I can loan you if you want to try before you buy? PM me.

Ant

[AJSullivan]

(ignore this post something very odd is happening with the forum..)

[AJSullivan]

People seem to be getting confused as to what my problem is, so let me summarise it.

I have NO PROBLEM, focusing on stars, moon, planet etc (even though i cannot get any defintion on jupiter ). I can quite successfully use the barlow (x2) and have had no problems with it.

The problems occur when i try to use my toucam. I bought it and set it up as per instructions on this website and another. I tried to focus on jupiter but the best I got was (see bottom of post)

I could not physically focus inwardly anymore. This is where the problem lies. I have been told that a shorty webcam adaptor might help, and at £13 seems the best answer. Someone also mentioned moving the primary mirror.

I tried to focus with and without my x2 barlow with no success. I would have bought the shorty barlow already, but I am waiting for my new webcam to arrive. During the process of trying to make the webcam focus, I over tightened the webcam adaptor, and suffice to say the huge "Smash" from inside the webcam was NOT a good thing, it was the ccd chip breaking

Anywho, hope that clears up what the problem is. Let me know if you have any other ideas!

Alex

P.s how odd. If you put imbed a image into the post, it wont recognise anything you post after it..weird!

?

[daz]

Erm, with respect, I think its you that's confused.

The normal problem with Newtonians is that the focuser does not travel inwards enough to achieve focus. The solution is therefore to employ a barlow, which as has been stated, pushed the focus point OUT and should allow the camera to come to focus.

So, what we need to know is what happens when you use the barlow?

And for clarification, does the focuser have a lens in it already?

[AJSullivan]

"I tried to focus with and without my x2 barlow with no success."

Using the barlow with the webcam does not seem to make any noticeable difference.

Not sure how to tell if the focuser has a lens in it, but if its just a case of looking inside it, then no it does not.

[Ant]

Adding a 2x barlow will make a huge difference to the focus point. Maybe 1 or 2 inches further out from the scope.

The image you have attached to your post is clearly an out of focus image.

By the look of it your scope also needs collimating! At f4 collimation will be critical.

Ant

[AJSullivan]

I thought it could be colimination as well. But wouldnt that make focusing on stars and moon difficult as well? Because other than with the webcam I have had no problem.

I had a little go at looking at the mirrors etc. and they all look pretty good to me (though of course this could be rubbish because i am a massive n00b )

[barkis]

Alex, I know you must be getting fed up with this problem, but just to categorize the situation, and explain what is needed for the equipment to come together and perform, what is necessary is the following.

1= the webcam must have it's original lens removed. You will not get a focus otherwise. Make sure this is the case, as the guy you bought it from, may have replaced it incase he thought you would want it.

2= The focal point of your scope must extend far enough into your focuser, and

fall onto the sensor of the webcam when it is inserted into the focuser.

3= If the focus of your scope falls short of the webcam sensor, then focus is

impossible. A suitable remedy for this, is to place a Barlow into the focuser,

and insert the webcam into the Barlow. The Barlow function is such, that

the focal point of you telescope is extended sifficiently to allow focus to be

accomplished. If this is still not possible, then I am starting to believe that

the webcam lens is still in place.

4= If you telescope f ratio is f4, then it is very unlikely to already have a

negative lensin the focuser. This is a ploy by some manufacturers to

artificially turn a short focal instrument into a longer focal length one.

Alex, at the risk of incurring your wrath, I implore you to once again check that the webcam lens has indeed been unscrewed and removed. After all you have said regarding your telescope behaving normally with an eyepiece in the focuser, and also a Barlow, it all points to the webcam lens.

Ron.

[Ant]

Ah I think we might be getting someone now.

But wouldnt that make focusing on stars and moon difficult as well? Because other than with the webcam I have had no problem.

So from this quote, I'm assuming that you can focus on the moon and stars with an eyepeice? But with the webcam you can't?

Hopefully thats right.

This is exactly what we thought. The focus point for a web cam and eyepeice (in most cases) will be different.

It is almost always the case that a Newt will not have sufficient in focus for a webcam or CCD or dSLR. Unless of course the scope has been soecifically designed for that purpose (most aren't).

Put in the webcam and wind the focus all the way in, centre the object as near as you can, then add the barlow. Chances are that the screen will now be blank - this is because the object is now very out of focus in the opposite direction. Start to focus outwards slowly - hopefully you'll start to see an image not too different from the image you attached, this should get smaller to more you focus out.

Hopefully it'll come to a sharp point (in focus) before you run out of "Out travel".

Collimation will make a difference, but you should still be able to pass through the point of best focus - even if best focus isn't ideal.

Ant

[AJSullivan]

Ant, though dubious, as I tried focusing all the way in, all the way out, and even shake it all about at some points, I still couldnt manage to focus the object, though i will try again next time. ALso I have checked my focuser and there is NO lens inside it.

Barkis: close to imploring my wrath but here you are:

[Ant]

Ok mate, but you are getting close with the focus on that shot.

I'd estimate another third of an inch and you'd be there.

I take it that the "dougnut" got larger and fainter as you wind out the focuser?

Describe exactly what happened to the star image as you focused all the way in to all the way out. When you added in the barlow (it was a barlow and not a focal reducer wasn't it?) did you see the dougnut on the screen at all? if so what happened when you went through the focus travel?

Have you tried picking a street light (at night) or another far away object (during the day) and having a practice?

Thats what I did when I couldn't work out where the focus point was!

Ant

[AJSullivan]

I havent tried another object with the camera yet.

You are right that the donught got larger and fainter as I wound out. As I said earlier, I am waiting for a replacement webcam to come as I broke mine overtightening the adapter :oops: