Teleconverters and Telescopes
Dudley Hanks
Rebel XSi. As soon as it warms up a bit, I'd like to try taking some pics
of the moon, etc, and I'm wondering if using a 2X TC would work with the
scope. Or, will it make the exposure so long motion will be excessive?
Anybody have any experience in such situations?
PixelPix
wrote:
The moon itself is as bright as a sunny day and exposures are
generally quite short, so I think you may get away with using the 2x
if it fits OK. Depending on your cam and it's noise characteristics,
you also have the availability of using higher ISO to compensate for
the 2x light loss.
Cheers
Rusty
Troy Piggins
What focal length and aperture is the scope? What camera are you
using?
Exposure times won't be a problem with the moon. It's very
bright. Well, not at the moment as it's near new, but you know
what I mean :)
--
Troy Piggins
Dudley Hanks
--
Take Care,
Dudley
"PixelPix" <ma...@pixelpix.com.au> wrote in message
news:dd2691a3-d342-4b88...@y34g2000prb.googlegroups.com...
Cheers
Rusty
Noise doesn't seem to be too bad with the XSi high ISO speeds, so I wouldn't
be afraid to use it. Also, I can switch in the optional high speed noise
reduction routine -- haven't had to use it yet, so I don't know how
effective it is.
Thanks, Rusty, I'll give it a try and see what happens.
Rich
news:dHRxl.18230$Db2.8994@edtnps83:
Likely your old reflector is about 800-1000mm in focal length so putting a
2x converter on it (won't hurt much optically, no more than a barlow lens)
might make to moon too large to fit into one (top to bottom) frame of the
camera, but it will get you closer. Just remember to let the scope reach
outside air temperature before shooting and to try to avoid shooting over
heated rooftops or pavement. Shooting over grass or water works best.
Dudley Hanks
"Rich" <no...@nowhere.com> wrote in message
news:a7OdnYTob-pVoVXU...@giganews.com...
Thanks, Rich, appreciate the tips.
Pulled the scope out this evening to check it out. My wife could only find
the following info:
Skywatcher
d=130mm
f=900mm
Couldn't find anything written on the lens, but it came with 2 eye pieces
with the following data printed:
Super 10 Long eye relief
Super 25 wide angle long eye relief
Also, has the EOS t-mount for mounting Canon SLR cams.
Probably won't get around to actually shooting anything for a week or two,
since it sounds like we're in for a stretch of cloudy weather. As soon as I
can get it out and take some shots, I'll give it a try.
Once again, thanks.
Take Care,
Dudley
Troy Piggins
>
> "Rich" <no...@nowhere.com> wrote in message
> news:a7OdnYTob-pVoVXU...@giganews.com...
>> "Dudley Hanks" <photos....@dudley-hanks.com> wrote in
>> news:dHRxl.18230$Db2.8994@edtnps83:
>>
>>> I have an old reflector type telescope and a T-mount adapter for my
>>> EOS Rebel XSi. As soon as it warms up a bit, I'd like to try taking
>>> some pics of the moon, etc, and I'm wondering if using a 2X TC would
>>> work with the scope. Or, will it make the exposure so long motion
>>> will be excessive?
>>>
>>> Anybody have any experience in such situations?
>>
>> Likely your old reflector is about 800-1000mm in focal length so putting a
>> 2x converter on it (won't hurt much optically, no more than a barlow lens)
>> might make to moon too large to fit into one (top to bottom) frame of the
>> camera, but it will get you closer. Just remember to let the scope reach
>> outside air temperature before shooting and to try to avoid shooting over
>> heated rooftops or pavement. Shooting over grass or water works best.
>
> Thanks, Rich, appreciate the tips.
>
> Pulled the scope out this evening to check it out. My wife could only find
> the following info:
>
> Skywatcher
> d=130mm
> f=900mm
That's about an f/7 f-ratio.
There's this free program here:
http://www.newastro.com/book_new/camera_app.php
direct download of application here:
http://www.newastro.com/downloads/ccdcalc/ccdcalcfull.exe
You can type in your scope's focal length and aperture, camera's
sensor size, pixels etc, and from a drop down box select
different astronomy targets like galaxies, common nebulae, and
the moon, to see how much of the frame they'll fill.
Without the teleconverter, with a 30D and 900mm scope you'll fill
a lot of the frame - probably half of the short side. Should get
pretty good detail out of that.
Little tip - the full moon is pretty boring. Get it just before
or just after full moon. You get some better shadow lines on the
craters, nicer textures.
Oh, make sure you don't take too much time between composition
and shooting. You'd be surprised how quickly the moon moves at
those sort of focal lengths.
Another tip - for rough exposure calcs for the moon:
http://www.adidap.com/2006/12/06/moon-exposure-calculator/
Hope that helps.
--
Troy Piggins
Dudley Hanks
Thanks, Troy, those links sound very interesting. I'll check them out while
I'm (im)patiently waiting for a chance to set it up and click some pics.
We've had the scope for a number of years, but never took any shots with it.
Set it up a few times for the kids to look through, but (with the help of
the LCD on the back of the XSi), this will (hopefully) be the first time
I'll be able to see anything through it.
Take Care,
Dudley
Twibil
> Oh, make sure you don't take too much time between composition
> and shooting. You'd be surprised how quickly the moon moves at
> those sort of focal lengths.
Hint: read up on your Galileo.
~Pete
Rich
Forgot one thing, use the camera's mirror lock up function if it has one
and fire the shutter with a remote or with the self-timer, to eliminate
as much vibration as possible.
Dudley Hanks
Yep, the XSi has mirror lockup, and I've got fairly easy access to that menu
item. My camera actually has a fairly wicked kick when the mirror moves
around, especially when using Live View, so I'll probably have to compose
shots in Live View, and then go back to regular mode and shoot with mirror
lockup.
I want to pick up a remote control so I won't have to depend on the 2 sec.
timer.
Take Care, and thanks for the tip.
Dudley