Give me a break. I used an angular diameter of 1/2 degree (30') for my
calculation of 1500mm to fill a 13mm high frame. If you're willing to
wait as long as a lunar month you might find it gets as large as 34'.
That would allow you to get away with a focal length of about 1350mm vs.
1500mm.
Your 300mm lens is making an image of about 3mm maximum diameter even at
perigee and maybe 2.5mm at apogee. I'm glad your images are selling but
300mm is still woefully inadequate (even at perigee) for filling the frame.
Chuck Norcutt
On 4/26/2013 10:47 AM, Ken Norton wrote:
>> To fill the frame vertically with the moon (1/2 degree) using a 4/3
>> sensor (13mm) will require a 1500mm (actual) focal length lens. My
>> 2000mm Celestron 8 is unable to do it on full frame (24mm vertical)
>> using only prime focus. Air currents, haze and vibration are serious
>> problems with any telescope. Fortunately, the moon is bright and usege
>> can use a pretty high shutter speed.
>
> Depends on apogee vs. perigee.
>
> All of my moon-subject shots are taken with 300mm on 4/3. This works
> out pretty well. There are times when i crop down to an equivalent of
> 600mm, but most of the time my compositions benefit from having a
> little bit of air around it. When you get beyond 600mm on 4/3, it's
> almost impossible to track the moon and frame it without a proper
> telescope mount. The moon is really scooting along and you've got only
> seconds for it to traverse the entire image area.
>
> These moon shots are actually selling. I have no idea who is buying
> them for what purposes, but I've gotten a few stock image sales out of
> them.
>
>
> --
> Ken Norton
> ken@xxxxxxxxxxx
> http://www.zone-10.com
>
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