Internal reflections in a GSO 2" ED Barlow

[dugnsuz (Doug)]

Hi all,
Received my 2" ED GSO Barlow from Bintel yesterday.
Checking out Jupiter I noticed some bright internal reflections bouncing around when I moved my eye around the 22mm Pano in the barlow.
Effect not noticed on deep sky work.
On inspection of the barlow, I noticed that the chrome barrel between the eyepiece holder and lens sections is not fully blackened - sort of dark metallic grey colour.
Could this be the reason for the reflections on bright objects?
If so, what is the best way to blacken an internal surface?
Any ideas/suggestions???
Cheers
Doug

[janoskiss (Steve H)]

Could be, but more likely it is off the lenses themselves. Perhaps reflection off eyeball in through the EP and then back to the eye again from the lenses in the barlow. Most barlow lenses tend not to be coated as well as FMC eyepieces, so they are more reflective.

[dugnsuz (Doug)]

Sent it back to Bintel in exchange for a Telrad!!
Anyone thinking about this barlow should remember the old advice - 1.try before you buy and 2. you get what you pay for!!!
I'm saving for a Powermate mate!
Cheers
Doug

[janoskiss (Steve H)]

Originally Posted by dugnsuz

Sent it back to Bintel in exchange for a Telrad!!

Good move!

Anyone thinking about this barlow should remember the old advice - 1.try before you buy and 2. you get what you pay for!!!
I'm saving for a Powermate mate!

You might like to have a read of this brief report on CN by Daniel Mounsey, who appears to be a very experienced observer - judging from his articles on CN under CN Reports, User Reviews and Articles. Basically he is saying that for best on-axis performance go with the standard barlow rather than the powermate. It would be good to get John B's opinion on this. I've only had brief looks through powermates and they seemed to work very well, but I cannot comment on how they might compare with ordinary TV barlows. But they sure are damn expensive.

I find the Televue barlow to be excellent. You have a good chance of picking one up second hand perhaps from someone "upgrading" to a powermate.

[Starkler (Geoff)]

Originally Posted by janoskiss

You might like to have a read of this brief report on CN by Daniel Mounsey, who appears to be a very experienced observer

A fascinating read, thanks Steve
Daniel appears to be quite the planetary observing guru, and (going off topic) his work on fan cooling of newtonians is a must read.

[Harpspitfire]

it could be alot of factors- even reflections off the cornea- thats also extra glass being put into an F5 system- al nagler even admitted the extra reflections and light scatter when comparing barlowed naglers to a simple quality abbe ortho, i once had a C5 that drove me crazy with reflections- turned out to be a collimation issue- jupiters tuff to judge, what does a bright star test show on reflections?

[dugnsuz (Doug)]

Cheers Steve,
I would have liked to get the TV 1.8x you got from AEC a week or so ago.
But, the final post in that thread stated that they had sold out.
I've just read through the cloudy nights link - thanks, lots of interesting stuff there and food for thought.
I went for the 2" GSO as it had been suggested that hanging a 22mm Pano off a 1.25" barlow might cause some focus issues. Don't know if that would be a problem - do you have any problems with larger EPs?
Cheers
Doug

[dugnsuz (Doug)]

Originally Posted by Harpspitfire

it could be alot of factors- even reflections off the cornea- thats also extra glass being put into an F5 system- al nagler even admitted the extra reflections and light scatter when comparing barlowed naglers to a simple quality abbe ortho, i once had a C5 that drove me crazy with reflections- turned out to be a collimation issue- jupiters tuff to judge, what does a bright star test show on reflections?

Yeah, Jupiter was 'orrible!!
I actually looked up to make sure it wasn't a car's headlights I was seeing!!!
Deep sky and bright stars were OK but the image was very soft. Took a little while and concentration to find optimum focus.
But it's all academic now as I sent it packing!!!
Cheers
Doug

[janoskiss (Steve H)]

Originally Posted by dugnsuz

I went for the 2" GSO as it had been suggested that hanging a 22mm Pano off a 1.25" barlow might cause some focus issues. Don't know if that would be a problem - do you have any problems with larger EPs?

I don't have that sort of EP, but the 19mm Pano works without any problems and the 22mm is very nearly parfocal with the 19mm so that should be fine too.