Barlow Focus Problem

[StevenA (Steven)]

I am not exactly new and I am not completetly stupid either but I have a problem using my 2X Barlow. It seems when I inset it to it's limited stop point, I can not focus it at all and I have tried all my EP's. The only time it focus' is when I only inset it a specific disance into the slot. Now I don't mind using it this way but the question arrises : "At this point is it still a 2X Barlow or is it a fraction of the magnification, as it is not completely inserted.?"

I bought it awhile ago and for some reason or another ( Actually I know ) I didn't take it back and have it replaced which Bintel would have done according to it's rep'.

Does anyone have any thoughts on this question or answer etc? StevenA

[erick (Eric)]

Which scope Stephen? The 8" Bintel Newtonian? Is it f6 or f5?

Let me make a guess and say that it doesn't particularly matter where the barlow lens is placed in the converging rays, it will have the same effect on the apparent focal length - ie. double it for a 2x barlow - certainly a cm or so here and there in the bottom of the focusser should produce the same outcome at the eyepiece. But, it has been known that my guesses are wrong

If you don't like the barlow wobbling around when it is lifted up off the "stop" of the focusser, try getting a 35mm extension tube to put it in. That will also allow your draw tube to be wound back a bit further into the focusser body - might also be a bit more stable?

[circumpolar (Matt)]

Sounds like you need a Extension Tube for your focuser. Bintel have a 50mm (2") for $39.00.

https://www.bintelshop.com.au/welcome.htm

[multiweb (Marc)]

I have used a 2x barlow cell with extension tubes and in my experience the further it is from the eyepiece/camera, the more magnification you get. I never had any problem to focus. Having said that I wouldn't know what happens if the barlow cell is positioned too close to the eyepiece.

[StevenA (Steven)]

Erik, I have the BT200 which is: 800mm f/L at 4.5f (5f). The Barlow is a 2" (Bintel) 2X and when I first told them about it, which was not long ago, they didn't mention or suggest an Extention Tube. I will however get an Extension Tube as it sounds like a handy gadget and useful for other things too (I guess). So far every thing I have bought I have purchased from Bintel, from my 8" Newt' and Mount, all my lenses & filters, Books, etc and then my budget blowing (3 years to save for) EQ6Pro but had never been disapointed. This is the first thing I must say that I have been really unhappy with. It rattled when I fist bought it and had to tighten the thread that held in the lense. I was even told by ***** that sometimes it is required to move the Barlow 'in or out' in Observing in certain situations or for specific reasons. What ever they may be???? Anyway thank you for the advice. The other respondents too. Thanks. StevenA

[dannat (Daniel)]

what kind of focuser do you have - it is low profile? some of the bintel scopes now have an extension piece which you screw on for visual - unscrew for photography

[StevenA (Steven)]

Dannat. As for the type of focuser, sorry I don't really know exactly. It a Crayford type with two speed focusing. It doesn't seem to be shallow however in comparison to my old 5" scope (which I gave away to a friend daughter). I will contact Bintel in the near future and ask.

[erick (Eric)]

Stephen

Just check the Bintelshop site. https://www.bintelshop.com.au/welcome.htm On the ATM Supplies page are the normal. Search "low profile" to find that type. It should then be clear which one you have.

Eric

Originally Posted by StevenA

Dannat. As for the type of focuser, sorry I don't really know exactly. It a Crayford type with two speed focusing. It doesn't seem to be shallow however in comparison to my old 5" scope (which I gave away to a friend daughter). I will contact Bintel in the near future and ask.