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Astrotrac and Canon 70-200 F4 L

ashworthacca

By ashworthacca
in Imaging - Discussion

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brianb

brianb

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70-200 f4L USM on its way

Nice ... you won't be disappointed.

I am also toying with the 50mm f1.4 as well

Do yourself a favour, get the f/1.8, it works just as well and is about 1/3 the price. The f/1.4 is very wooly at full aperture, the f/1.8 works just as well as the f/1.4 when set to the same aperture. The 50mm f/1.2L is a lovely lens but the cost ought to put you off ... in any case the extra stop of speed is of dubious value for astro work, exposures will be limited by sky glow (or light pollution) in any case.

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brianb

brianb

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Already got the 1.8 but need another... finding it needs to be stopped down to around f4 to give the best results..

How are you focusing?

The reason I ask is that I had an issue with my camera and lenses faster than f/2.8: turned out that the autofocus detector wasn't quite in the same plane as the image sensor. With some of the more expensive cameras there is a "microfocus adjustment" which allows you to tune the focusing mechanism, otherwise it's send away to get adjusted. Made a big difference with my camera.

If you're focusing using "live view" then the AF sensors are bypassed & all this is irrelevant.

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ashworthacca

ashworthacca

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On my lenses at home I use a 2" eyepiece strip. Works for me.

Dave.

ah, thanks Dave.....I'll get one ordered now.

:)

EDIT: Just thinking out loud but if I got a dew strip to fit my ED80....say 4" could that be adapted for use on my Canon lens? Could kill 2 birds with one stone......:(

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davew

davew

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You may need to wrap it round on it's self. I can't see it overheating if you keep the power down. I have one of those for my frac and I have used it on the lens. Trouble I found is that I need to wrap around the focuser on one of my lenses so as the mount moves the focus COULD change. Nail it all down.

This applies to both dew straps not just the 4".

Dave.

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ashworthacca

ashworthacca

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You may need to wrap it round on it's self. I can't see it overheating if you keep the power down. I have one of those for my frac and I have used it on the lens. Trouble I found is that I need to wrap around the focuser on one of my lenses so as the mount moves the focus COULD change. Nail it all down.

This applies to both dew straps not just the 4".

Dave.

That's good to know Dave....many thanks for the info.:)

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brianb

brianb

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are these available for a range of canon lenses? Do you have a link?

Try here ... these are not manufacturer dependent, just get the one that matches the filter thread on your lens. I'm sure there are lots of other suppliers if you look.

I didnt fany paying £123 for the official canon tripod bracket for the lens but found this one...

Probably worth the risk. Some people have reported fitting issues with cheap tripod brackets (so the lens is free to vibrate a bit in the mount) but that's fixable with extra felt. Just watch out for cracked castings.

I have a third party tripod bracket on my 70-200 f/4L IS & it's indistinguishable from the genuine article, apart for saying "for Canon" instead of just "Canon" and the font of the word "Canon" being slightly different, probably to avoid copyright issues. Cost me around £30 incl import duty & carriage from Hong Kong.

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ashworthacca

ashworthacca

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My replacement astrotrac arrived this morning and I've just had it tracking for 2 hours. Connected first time and didn't miss a beat.

Thanks to FLO for sorting it out for me without a problem.

Got home about 5.30 and the skies were clear only for the clouds to roll in as I got my winter woollies on.:)

Itching to have a play now though.:(

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davew

davew

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Just an update.

I tried a metal hood last night. I found I had to up the dew control power a tiny bit as a small amount of mist started to appear. Other than that it all worked as normal.

The 2" eyepiece band still fits.

Dave.

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