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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

telescopic auto extension tube (1 Viewer)

Seems a good idea but how practical? Would the auto tube handle the weight of the camera better than our regular focuser. If not, then we'll ended with some sort of collimation problem. OM mount is not a problem, it can be changed.
 
No, I don't think it would replace the focuser. It would replace what we usually have as extension tubes - and in this case it will function as an extension tube with fine focusing properties, as well as a variable extension tube. This is at least as I imagine how it could work. You would have to rough focus with your regular pinion/crayford focuser and the fine tune it with this one.
 
I suppose it would benefit those with good eyesight. I still need to struggle a bit with the regular focuser needles the say the fine focusing knob (as with 2 speed focuser). Very attracted with the Sony A55 which comes with electronic VF and very bright LOL.
 
thornlv said:
It would probably be better for adjusting your minimum focus distance rather than fine focus itself, could be fiddly focusing fist rough with the focuser then fine with the ext tube - youd need three hands.

there is also something similar from scopes n skies here

http://www.scopesnskies.com/prod/vet42-variable-extension-tube.html
Click to expand...

Yes, I can see how it can become fiddly - and the three hands - well, sometimes I think I need them already..:)

the scope n skies thingy - is that really for a refractor type of scope? Most of those seems to be for the other kind of scopes (mirror ones you know). I know Borg have helical focusers for their line, but haven't found anyone that have adapted one of those to a 80ED-scope.
 
It can be used for shooting shore birds or other slower moving birds where you want to really spot on focus. But bear in mind, any additional moving parts will sag your camera more due to free play, thus affecting picture IQ. Something similar to collimation.
 
Am i getting this right .. its just an extension tube, that can be adjusted for length, but has no glass ?

If thats so, this isnt going to help with the actual focusing on the subject. Your eyes do that.
 
I think he means that because you can 'vary' the length, you could in theory use it to focus, which you could if your crayford/rack and pinion was fairly close already.
 
Ok yes, so its an adjustable extension, but once you have the required length to achieve close and infinity focus, the adjustablilty of the length becomes irrelavant , doesnt it ?
 
I could see it being used to achieve closer close focus better, anyway have ordered the Astro engineering one so will give my thoughts on it later.
 
Well thats exactly what the right fixed length extension tubes will do. I think the vast cost of the Oly adjustable length extension tube that cango is looking at, is a waste of money.

I think its posted on the forums somewhere, maybe Paul C posted it, that to get close focus down to say 5/6 metres, and infinity focus too, one needs about 80mm of fixed length extension tube.

Once you have close focus sorted out to 5/6 meters, and you still get infinity focus with 80mm extension tubes, where is the benefit of having the extension tubes giving futher adjustability ?
 
If i want less than 5/6 meters, should be able to do it for less than the price of the Oly one.

ps: how's the eyes going ?
 
yes, just buy longer extension tubes, ( more than 80mm ) but I think there's a limit to how close you can get

The eyes are ok, but still got another laser operation yet ;)

Thanks for asking
 
Pete, the basic of discussion here is on the micro extension adjustment with the extension. The extension can extend and retract like when you are zooming with conventional zoom lens. It gives fine focusing more feeling (helical focusing). You must first focus as normal and when in focus, you can use the helical adjustment on the extension to fine focus.

But bear in mind, it wouldn't work for you and me. Like you said, it's in the eyes and we loose part of them already. We are leaning towards hit and run method LOL.
 
alphan said:
Pete, the basic of discussion here is on the micro extension adjustment with the extension. The extension can extend and retract like when you are zooming with conventional zoom lens. It gives fine focusing more feeling (helical focusing). You must first focus as normal and when in focus, you can use the helical adjustment on the extension to fine focus.

But bear in mind, it wouldn't work for you and me. Like you said, it's in the eyes and we loose part of them already. We are leaning towards hit and run method LOL.
Click to expand...

That's right. It's not the ability to variably extend the extension tube, though a nice feature, but the feeling one gets through the helical focusing - and that comfort might turn to better pics. who knows. Yet, the price is just little too much just to test.
 
Have got the Astro engineering variable extension. It has female T2 thread at the front and male T2 at the rear, so it just screws on to my nosepiece adapter and a T2 ring screws on the rear (then camera, TCs, extension tubes)

At first glance will give me about 1.1 meters difference in close focus (ie: nosepiece - vari adapter - T2 ring - bayonet ends of an extension set - camera = 5.5m to 4.4m)

Its lockable and gives a stable extension. It would be no good for fine focus as it is too jerky/rough in its present state but could be if I can find a way to make it more smooth.
 
thornlv said:
Have got the Astro engineering variable extension. It has female T2 thread at the front and male T2 at the rear, so it just screws on to my nosepiece adapter and a T2 ring screws on the rear (then camera, TCs, extension tubes)

At first glance will give me about 1.1 meters difference in close focus (ie: nosepiece - vari adapter - T2 ring - bayonet ends of an extension set - camera = 5.5m to 4.4m)

Its lockable and gives a stable extension. It would be no good for fine focus as it is too jerky/rough in its present state but could be if I can find a way to make it more smooth.
Click to expand...

So yours are only good for reducing the near focus and yet able to go infinity within a second. How was the free play (sagging on the camera)?
 
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