ring around star

[Poita (Peter)]

That is really interesting, would be great to see if a rolled up piece of flocking paper removed it.

[PeterM]

I bought Joshuas scope to take out to Leyburn to do my SN search from there and leave my other 12inch in the observatory.
I did 2 weeks of testing once I recieved it, apart from a slight miscollimation I have not seen anything that concerns me optically with this telescope.
I have been using my 12inch LX200R since 2007 and what I see in my 30 second images in that scope are the same as in Joshuas old scope.
I have had a look at a couple of 3rd mag stars visually when collimating and the stars are as I would have expected.
Joshua had cleaned the corrector to what I would say was an excellent job, infact it looks better than my existing scope that gets cleaned once a year.
So I cannot comment on what Joshua saw or imaged other than in my 30 second images I am more than happy.
There is a slight tracking issue that I think I have resolved with a Petersen Ezi Clutch but will know more about that after this weekend at Leyburn. I have added a counterweight set also as well as a Moonlite focuser.
From memory (the scope is in its JMI case) the baffle tube is matt and not gloss, will come back on that to be sure.
Oh yeah I also use an astrozap dew shield that is flocked (nearly spelt that wrong) and a dew zapper built in.

[Joshua Bunn (Joshua)]

Originally Posted by PeterM

Joshua had cleaned the corrector to what I would say was an excellent job, infact it looks better than my existing scope that gets cleaned once a year.

Thanks Peter.

I painted the area / circle immediately inside the visual back because i thought it looked shiny, to about 1" deep. I didnt paint the baffle tube. I used what i think was chalk board paint. It made no difference, the ring was still there.

Also, I rolled up some black felt and pushed it to the top of the baffle tube, with a little of the baffle tube left exposed at the visula back end because the felt wasnt long enough. This too made no difference - the ring was still there when looking through the scope.

Thought ide say what had been tried by me.

Josh

[casstony]

Thanks for the info Joshua. I guess the next question is 'are there any 12" Meades that don't show the ring'? Maybe it's inherent to this particular model. Looking into the front of the scope it's clear that more off-axis light gets past the secondary to the rear of the baffle than in the 10".

It's all an exercise of curiosity for me - the scope shows very nice images generally and has given me my best view so far of eta's Homunculus.

[casstony]

Originally Posted by PeterM

I have been using my 12inch LX200R since 2007 and what I see in my 30 second images in that scope are the same as in Joshuas old scope.

Peter, do both scopes show an obvious ring around Sirius or other bright stars, as per the photo's earlier in the thread?

[PeterM]

Hi Tony,
Just waking from 2 days of Flu sorry for not replying sooner. I haven't taken any direct 30 second images of really bright stars, as what I see in my 30 second galaxy/star images looks fine to me. I am working with a Starlight Xpress SXVH9 @F7 so my field is small at 13x11 arc minutes. I will get around to doing that with Joshuas old scope this weekend and mine maybe next week. It would not surprise me if there were a ring around really bright stars given the light collection of the scope/moisture & on the corrector etc and that a few have reported similar, I have seen a similar effect in a 30 second image if a reasonable bright star is nearby . Even so if the galaxy/star images are as good as in my LX200R then I see no need to worry.