Televue 40mm Plossl - do I have a problem?

[DRT]

I recently acquired a 40mm TV Plossl. I used it a week or so ago in my Dob but not for long as I was really just using it as a finder.

Today I set-up the CPC to have a look at the sun. After browsing around the sunspots with my Naglers I decided to start comparing the Naglers and the Plossls. I popped the 40mm into the diagonal and was surprised to see a very thin straight black line bisecting the Sun's disk. I released the lock on the diagonal and rotated the EP. The line rotated, so whatever it is is coming from the EP and not the diagonal of scope. When I moved my eye to the side so that the view blacked out the line was still visible, bot was now white instead of black.

At first I thought the lens on the Plossl must be cracked across its diameter but it looks perfectly fine. Given that it is visible when in focus and when blacked out I wonder if it is some stray light getting in from somewhere.

I checked all of the other Plossl's and only the 40mm shows this problem.

Has anyone encountered this before?

[Laurie61]

I have the 40 tv plossl and have not noticed this in mine. Did you buy it new or used, if used I wonder if it has been used as a finder lens and has had some D.I.Y cross hair's fitted at some point. A very thin wire or hair will show as described if this is the case. Although I would not think it would look like a bright line if viewed off angle ? 

[moriniboy]

Nothing like this on mine either

[DRT]

It was new from Telescope House. It hasn't been modified as far as I can see.

I'll get it touch with them and ask them to swap it.

[DRT]

I just went out for another look. I unscrewed the barrel and screwed it back in. The line has gone.

Quite bizarre.

[Laurie61]

Good to here you have sorted it  the tv 40's are a nice eyepiece. Although they do show a smaller field than the other Plossl's if you only have an 1.25" visual back and want to generate a bigger exit pupil they do a great job    

[Moonshane]

weird. must have been a misalignment of the optics assuming the nosepiece was loose. I have just used my 40mm widefield in the 6" f11 scope on the sun and was really pleased with the view actually. I may in future buy a 40mm TV plossl myself as I do prefer the simpler designs on brighter objects.

glad you are sorted Derek.

[Earl]

is it possible to be a hair inside the eyepiece tube or is it dead straight?

[DRT]

It was dead straight. There is definitely nothing on the lens or inside the tube.