Ironing out imaging problems

[Carole]

Mark has kindly adapted my old mains lead for me so I can use it to power the telscope straight off the 12V battery (rather than through the invertor and then the mains adapter because I didn't have the right connector) and it seems to be working fine.  I have also - since DSC - tried out my telescope on the mains and that also seems to work fine, so I think all my problems at DSC must have been due to power problems thank goodness.

However, I still have one remaining problem and that is getting the object actually on the chip.  Sometimes I can manage it and sometimes I can't.  I looked at a day time land object when I was at DSC and what was in the centre of the scope was at the bottom of the screen through the Webcam, so I guess at astronomical distances this discrepancy gets even wider. 

I was wondering whether any-one has a spare webcam they are not currently using (which seems to line objects up centrally - vertically and left to right if poss) that I could borrow in order to see whether it's me or a slight misalignment of the chip in my webcam. 

It would also be useful to be able to try one that shows more than Moon and planets as when all I get is black sky (if my planet is off the chip) I have no idea where I am looking. 

Many thanks

Carole

[JohnP]

Carole - do you have a finder scope with your setup..? Does the CCD chip on your camera look as though it is centred correctly in the 1 1/4 inch eyepiece adapter...?

John

[Rocket Pooch]

Carol, I'd be gobsmacked if it was the web cam, are you using an adaptor?

Chris

[Mike]

Get your image dead centre on the webcam and then line up your finderscope to also be dead centre on the object after that. From then on use the finderscope to find your objects and they should be pretty much dead centre.

[Carole]

Get your image dead centre on the webcam

If only I could, this is what I am having difficulty doing.  I can see the object right in the middle of my eyepiece when I put a lens in (NOT the finder scope) (surely this has to be more accurate than the finderscope, and when I take that out and put the webcam in I get nothing (it's not as if the object has drifted between taking the eye piece out and putting the webcam in because I then put back my eyepiece to check and it's still dead centre.  Ian saw this happen at DSC.  It's very frustrating. I have tried putting the webcam in both the eyepiece and the rear port, to see if there was any difference, but it happens to both.

are you using an adaptor?

I just have webcam with IR filter, in eyepiece of scope then straight to laptop.

do you have a finder scope with your setup..? Does the CCD chip on your camera look as though it is centred correctly in the 1 1/4 inch eyepiece adapter...?

I do have a finderscope on my telescope, but I don't quite understand this question, what is a 1 1/4" eye piece adapter?  I don't think I'm using one (see previous quote and response). 

I would have thought if I can see the object dead centre in the eyepiece of the telescope then I should see it dead centre in the webcam, albeit out of focus, but I don't, I have to fiddle around until I can and don't always manage it.

Carole

[Tony G]

Carole,

I found that when using my web cam that if the setting was above 15fps that the object would be very difficult to find, but if you was to reduce it 10fps or even better 5fps the object would  appear on the monitor, but sometimes you may have to adjust the brightness as well, which i don't think would happen during the day when testing as it would be to bright, you could try this, it worked for me.

Tony G

[The Thing]

Carol,

I have the same effect with my Phillips webcam, nothing over 10fps shows stars unless they are very bright. Also over 10fps the video stream is compressed by the camera so the quality deteriorates. It could be that the compression that stops the object appearing, if it is relatively small compared to the frame size.
You can't turn off the webcam compression unfortunately, its done automatically to allow the data to squeeze down the USB cable quickly enough. Hope this helps.

[Mike]

Agreed, make sure that you have a low fps and the gain turned up and point it at a bright star. You can see the star even if your close to it but don't have it on the chip as the glow from it starts to appear on one side of the chip (putting the scope slightly out of focus helps). Once you do have it on the chip, make sure it is in focus and dead centre, then match your finderscope to the screen. From then on finding the object should be a lot easier. Remember that you have a long focal length which means the Field of View is going to be pretty tight, which doesn't help. You are always going to have problems centering objects with the ETX mount as it is a very sloppy mount and there are no fine controls or accurate GoTo on it so anything you do isn't going to be easy.

[Carole]

Thanks every-one for their advice and in-put, but I don't think its a question of not seeing the object because I have the wrong settings as I normally have it on 5fps.  I found long ago that if you fiddle with the controls you will often see something that appeared not to be there before, and so I always try altering the settings, but having moved all the sliders up and down and all combinations I cannot get anything on the chip at all on occasions. 

I'll give what you suggest a try Mike, but I still don't see how the finderscope is going to be any more accurate than having the object dead centre in the eyepiece.

I would just like to borrow some-one else's webcam to see whether I still have the same problems, so I can eliminate whether it's my technique or the webcam that is at fault. 

Carole