New eye piece, but do I have a problem?

[dobserver]

I just took reciept of my new Paradigm 8mm eye piece yesterday. Needless to say it was cloudy so I couldn't give it a proper trial, but I did spot a break in the cloud and whipped out the 8" Skywatcher for a look-see.

Betelgeuse was just visible, so I quickly pointed at that while I still could. All seemed fine with the view once in focus. I altered the focus, taking it out first one way and then the other. One way (turining the focuser towards the OTA) was fine, a clear circular pattern, but when I went out of focus the other way it was a different story. The circular pattern was there, but there was a 'bite' out of the left hand side of it!

Now I don't know much about these things, but I've not heard of this before. I know the mirror wasn't cooled properly and I need to give it another try, but with the weather we're getting at the moment gawd knows when that's going to be! I don't want to be stuck with a duff EP because I've not returned it in time....

Any one know what might have caused this and if it's going to be a problem?

I did have a look at the moon through the clouds with it and from what I could see it looked great - and HUGE!! So maybe I'm worrying about nothing, I just want to be sure....

Cheers,

[wulfrunian]

How long did you look at it for? - only thing I can think of is the edge of a cloud obscuring it, but if it stayed like it for a while then I suppose that's less likely.

Or maybe you've discovered a hitherto unknown companion star eclipsing it, get it named after you

[dobserver]

Hmm, no it wasn't another star. I wish I could draw a picture of what it looked like. I only noticed it when it was deliberately out of focus, and it was the fuzzy circle that you would expect to see, but with a chord on the left hand side, and the part of the circle beyond the chord was missing! Most strange....

[Merlin66]

I hazard a guess that the eyepiece is OK and you have either a collimation problem or something ( edge of focuser tube etc) sitting into the beam.

ken

[haitch]

I doubt it's the draw tube interrupting the beam - you mentioned it happened when you racked it out but not in and you would expect either both ways or the opposite way round I would have thought.

First things I would try (I'm no expert though) would be collimation or pinched mirror. Have you experienced this with any other EPs?

[dobserver]

No, I just literally tried out this new EP last night for about 2 minutes! I'm not worried about the scope - it's brand new and, although the collimation could be off slightly, it won't be major.

I just realised that the 2" to 1 and a quarter inch adaptor was loose - I'm hoping this might be the cause. The one on my scope doesn't unscrew, so I never thought to check it! I wonder if that might be the cause and my new EP is OK after all. I sure hope so.....

[Doc]

I think your eyepiece will be fine, you say the view was Ok when in focus, so this only happens when you defocus.

Is it a solid tube dob or a truss tube?

I had a similar thing happen to my dob and it was the bottom of the light shroud crossing the light path.

[dobserver]

I was using Reece's 8" Skywatcher solid tube...just cos it's easier to take outside quickly than mine.

[RobH]

It does sound like somethings obstructing it Steph, although why it should be one side of focus and not the other is puzzling.

Put it in your 12 inch and see if the same thing happens. If your sly is like mine at the moment, there are stars visible through the high cloud.

Cheers

Rob

[dobserver]

Yes boss, I'll give it a whirl!

[RobH]

Clear here now....looks like you have got a good clear patch imminent too

How is Jasper getting on with that new collar?

Rob

[dobserver]

OK so I tried it in the Lightbridge and I'm pretty pleased with it to be honest. Gawd knows what was going on with it last night - I'm guessing it was something to do with that sloppy connection on the adaptor, which I've now tightened, btw.

The good news is the image is clear and sharp. The moon, although full and 'boring' was so huge I had to slew around to see it. I had fun positioning the scope to the right of the moon then watching it move across the FOV like a movie! You know what they say - small things.....

Pointed to Mars and tried the defocussing, no problems at all. Then I tried it on M42. I think it'll perform really well under a darker sky. So I did the whole in and out of focus thing again, and to my dismay there was a line across the circle at the top right when I racked in and the bottom left when I went out!! I grabbed Carl to have a look and he gave me the good and bad news.

Good news - there's nothing wrong with my new toy, in fact Carl is so impressed he wants some too.

Bad news - I'm a daft fek!! - it was a telegraph wire in the FOV!! Doh!! *sigh*

Live and learn, eh?

Rob, Jasper loves his collar thanks. I'll email a piccy one of these days.

[dark knight]

hehehehe, need I say any more

[albedo0.39]

it was a telegraph wire in the FOV!! Doh!! *sigh*

Top grin ! Hey Steph - got your PM... will construct a reply soonest... glad to hear you are experimenting with EP's. Gotta get my finger out now in time for this years sessions. Just have not decided what to get yet !