Will a Televue 3x barlow work with focustravel on Skywatcher 190MN?

[Mr Bergman]

Hi all, 

need a quick advice! I want to buy a Televue 3x barlow, and I do hope it will work with the focus travel on my scope without any extensions etc.? 

Anyone with same scope & barlow who could confirm that it works!? 

Best regards, 

Erik

[NGC 1502]

Hi Erik. Saw your post earlier but did not reply because I've no direct knowledge of this question.

However, since you've had no replies, perhaps the following could be of some limited help.

My TV 2x Barlow shifts the focus position very little from the eyepiece only focus point.

Maybe purchase from a supplier that will allow a return if not suitable ?

Regards, Ed.

[Ruud]

A barlow projects the focal plane farther out. They're sometimes used when you don't have enough in-travel on your focuser. (I know, I seem to contradict Ed, who notices little difference for the focus knob, but in the barlow the eypiece is farther out, by the length of the piece of barlow that sticks out. Ed just has a well designed barlow.)

You won't need an extension tube.

The part of the barlow that sticks in might be a problem, if it sticks in too deep. It might get in the way of the light entering the aperture. That would be bad. Do you have a low profile focuser?

[Mr Bergman]

Hello Ed and Ruud, thank you for taking your time answering, much appreciated! 

I have a low profile focuser; http://agenaastro.com/antares-low-profile-crayford-focuser-reflectors-dual-speed.html      Bought my scope second hand, but my focuser looks exactly like this one. When using my 2x barlow, I have to extend the additional 2" extensiontube before inserting my barlow...and that´s why I was a little skeptic about the 3x..

/Erik

[Ruud]

I see!

Look here: http://www.televue.com/engine/TV3b_page.asp?id=52

TV's 2" barlow sinks in much deeper than the 3x 1.25". You might be in luck. If it still sinks too deep, a few rubber O-rings might be enough to solve that problem.

How good is your scope? Is it an APO-killer?

[Mr Bergman]

Ah, ok. I guess it should work! I don´t need to put it in all way in, I can fix it halfway. 

My scope is really nice. It is very fast, but more demanding regarding collimation etc. My weakspot it actually the focusser; it is badly built and shifts if you touch it with the drawtube extended. A moonlite would make it better:-) APO-killer, I don´t know! I would like to be able to get out there imaging without worrying about collimation....but on the other hand it´s fairly fast with f-ratio 5,26...

[Ruud]

Thanks Mr Berman! 

I know the Maksutov Newtonian design only from Telescope Optics, Evaluation and Design (Harrie Rutten and Martin van Venrooij). They speak highly of it.