Teleconverter versus Barlow?

Hi there, got a question for all those out there who use Barlows and/or Teleconverters for getting that extra bit of focal length...

A while back I had a cheap 2x teleconverter, which worked okay with my EF 75-300mm, EF 24-105mm and EF 18-55mm lenses. I never actually tried it with my scopes though, but instead always plumped for the Barlows.

My dad ended up with the Teleconverter, and I've just got another. The first was an "MC4", but this new one is an "MC7"...7 elements as opposed to 4 apparently...a better quality product apparently. So I thought I'd try it the other day.

I read somewhere that if the lens has a smaller aperture than f/4 that the auto-focus won't work. So I tried my 50mm f/1.8. Aimed at something 10 or 15 feet away, half-pressed my shutter button and the lens proceeded to focus all the way back and forth, very rapidly, without actually focussing on anything! I thought this seemed a bit odd.

I then hooked up my 400mm scope, aimed towards Venus, focussed the scope and pressed the shutter button, and got an error on the camera..."Can't communicate with lens", or something like that.

I read in a book somewhere that Teleconverters give better results than Barlows, but at the moment I strongly disagree. With the Canon EOS 450D is there a way to disable the camera-to-lens communication, so that it'll work when using a Teleconverter between the camera and a scope?

Thanks.

Does ANYone have a cheap EF Teleconverter that they've successfully used with a Canon lens? This Teleplus one I have doesn't work at all, so I'm hoping to get a Jessops one, like the first one I had.

I do not think it is a problem with the teleconverter. I have a Canon Extender
EF 2X II. It work wonderfully well with my 200mm L f2.8. I have a Celestron Onyx 500mm f6.25 OTA that I wanted to extend to 1000mm with the converter. It reports the ERR 01, even with everything set to manual.

The question may be, "How can we "fool" the camera into thinking it is a manual converter?"

Dale

Will probably buy a barlow!

Dale

dale65bama wrote in post #7262138
It reports the ERR 01, even with everything set to manual.

The information I read about TCs being better than Barlows is probably quite old, before cameras got too "clever" for their own good.

Oh well, thanks for that, I'll just ditch the idea then.

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Anyone want a Teleplus 2x MC7 Canon EF-fit Teleconverter?!

EDIT: Ignore that, it would seem that blocking out the contacts on the TC will prevent the errors. I'll try it tonight.

Thought I'd toss an option into the mix.

The TeleVue Powermates are excellent. I have the 2" 2x model with the T-ring adapter.

http://www.televue.com​/engine/page.asp?ID=42

I tried the 1.4 Canon Telecon with my W/O ZS70 and could not achieve focus so gave up.

If you are handy, clean tap those gold pins and use TC in manual mode. You will not get error 99 (Try only at your own risk. I accept no responsibility if something goes wrong!).

chris.bailey wrote in post #7268409
I tried the 1.4 Canon Telecon with my W/O ZS70 and could not achieve focus so gave up.

Have yet to try it still, but how's the WO ZS 70, (changing the subject here somewhat)? I'm hoping to get a WO ZS myself any day now, and thinking of the 66mm. Widescreen Centre have them for £199, which I think is pretty good.

In case anyone's remotely interested, I taped over the connectors on my 2x TC last night, and it would then successfully take a photo with no lens attached, whereas before I was getting Err01 on the camera. Just in case anyone else was thinking of trying such a thing.

With my 2x Barlow, which is 2", and my 2x TC, I should still be able to get a fair bit of light in, but shoot at nearly 5000mm. Saturn...where are you...?

I have a WO ZS 66. Great Scope. You will need a WO flattener to get decent results though. The flattener also allows my 40D to connect directly to the Scope, with a mounting ring. Got mine from Ian King Imaging. Really helpful pleasent chap. Worth a call.

70mm f/6 and 0.8x Flattener ordered.

I hereby apologise to all in the UK, because cloudy skies are bound to appear when I receive it!!

How are you getting along with the new scope?

Haven't used it yet due to the weather. Plus I'm needing to do some jiggery pokery to get it attached to my EQ5 mount. It's a lovely piece of kit though...really solid, good quality in every respect...can't wait to give it its first light.