Re: Porr images with 20D/C90


"jess" <jgates@xxxxxxxxx> wrote in message
news:1127567780.618535.183230@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> I have a relatively new DSLR and an old (~ 1980, black tube) Celestron
> C90. The other light I tried taking a picture of the full moon with
> the camera at prime focus (tripod, ASA 400, 1/300, remote release
> after ~10 sec of MLU), and the results were well-exposed but very
> fuzzy. I thought that perhaps the 'scope was damaged or had
> deteriorated in some way, but visual observations (30mm Kellner) look
> very sharp. So, I have a few questions:
>
> 1. Is it normal for lunar astrophotographs to have much lower
> resolution than visual images?
> 2. Since the 'scope focus "beyond infinity", it is very
> difficult to focus on the screen in a Canon 20D. Do you have any tips
> for manual focusing with a DSLR, or is it largely trial and error?
> 3. The tripod I was using was an old, cheap Velbon (~$25 new) I
> bought for a video project, and is none too stable. If you touch the
> 'scope at all the image dances all over the place. After some
> research, I've ordered a Bogen / Manfrotto 3246 with 488RC2 Midi
> Ballhead that will be used primary for daylight photography, but it
> hasn't arrived yet. Would you folks with experience expect this to
> be any better?
>
> I understand that the 'scope is not the greatest, and this was my
> first try at lunar imaging, but my images look nowhere near as good as
> those I've seen from similar setups. I don't expect miracles, but
> these pictures are pretty sad. Any suggestions?

Yes.
Use a much shorter shutter speed.
What speed is the C90 - f/10 or thereabouts?
Sunny 16 suggests about 1/1000th - but I'd go for 1/2000th at least.

When I look through my 600mm, fixed on my very stable tripod, it takes at
least a few seconds to damp down any shakes, and I suspect the mirror slap
would really play havoc.

Much easier to fix a few stops of underexposure than it is to fix image
blur. :-)

Focussing? Trial & error or a Hartman mask.

....and yes, the Manfrotto will be *much* nicer than the old Velbon.

- but just try bumping up the shutter speed.

--
Jeff R.


.

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