Full Moon - 350D + 300mm lens practise

iceman (Mike) · #1 30-07-2007, 09:08 AM

It's good to practise when you've got a big Total Lunar Eclipse coming up!

For eclipse night, I figured I'd be able to use my 350D + stock 75-300mm lens @ 300mm to capture the changing face of the moon as the shadow passes over it.

While testing this theory out last night, I came to realise that 300mm isn't nearly enough to get good detail on the moon. Even with the 1.5x crop factor (making it 450mm instead of 300mm), the full moon still only fills 1/5th of the frame or so.

After cropping, so that the moon is a reasonable size for display, there's no fine detail present as the Moon just didn't cover enough pixels on the CCD. It looks as if it's had too much noise reduction applied.

The attached result is cropped, sharpened and had levels adjusted. I'm really not happy with it and so it's definitely made me re-think my plans for the 28th August.

I need more focal length! Might have to go back to afocal - shooting through a lower power eyepiece. hmm more testing to do tonight.

h0ughy (David) · #2 30-07-2007, 10:10 AM

dare I say it Mike - what about through the 12" - you know like prime focus????

sheeny (Al) · #3 30-07-2007, 10:22 AM

Cloud stopped me from playing last night, Mike, but I understand the problem... HOughy's idea any good with your scope and camera?

I thought about using my scope with the E-510, but I know the moon fills the frame of my OM-1 at secondary focus, so the E-510 won't fit it in even with the 0.63 FR.

So my plan was to make do with the kit 40-150 lens @150mm (300 eq).

hmmm I could try my old OM 75-150 zoom at 150mm with my OM 2x teleconverter... I'll need to practice with that to get focus right!

Al.

ving (David) · #4 30-07-2007, 10:52 AM

what f# you working at mike? kyou could buy a teleconverter if you are at like f2-4.

iceman (Mike) · #5 30-07-2007, 11:50 AM

I was at f/7.1 I think.

sheeny (Al) · #6 30-07-2007, 11:58 AM

hmmm just had another thought... I might have to investigate the ToUcam with an OM lens...

Al.

RB (Andrew) · #7 30-07-2007, 01:15 PM

Quote:

Originally Posted by ving

what f# you working at mike? kyou could buy a teleconverter if you are at like f2-4.

Quote:

Originally Posted by iceman

I was at f/7.1 I think.

Are you guys talking about Mike's 75-300mm lens?
If so then increasing the f# won't give you a tighter FOV.
You need more FL.
Unfortunately a teleconverter won't fit on the 75-300mm.

h0ughy (David) · #8 30-07-2007, 01:17 PM

Quote:

Originally Posted by Rocket Boy

Are you guys talking about Mike's 75-300mm lens?
If so then increasing the f# won't give you a tighter FOV.
You need more FL.
Unfortunately a teleconverter won't fit on the 75-300mm.

well I will just have to use my 50-500 and the 2 times teleconverter with the pentax

ving (David) · #9 30-07-2007, 03:35 PM

Quote:

Originally Posted by Rocket Boy

Are you guys talking about Mike's 75-300mm lens?
If so then increasing the f# won't give you a tighter FOV.
You need more FL.
Unfortunately a teleconverter won't fit on the 75-300mm.

you are quite right.... but a teleconverter will give more magnification, but at the scarifice of f#... i think a 2x tc will drop his lens back 2 stops... therefore making it no longer a f1.7

iceman (Mike) · #10 30-07-2007, 03:40 PM

It was at f/7.1. The lens itself is f/5.6 at widest zoom, i think. Not fast by any means.

I don't own a 2x teleconverter either and don't particularly want to buy anything new for the eclipse.. but I do want better photos than the one above!!

Will have to try afocal through the newt - can't do prime focus. It wouldn't come to focus and I don't have the necessary adapters and t-threads anyway.

Thanks for the input.

sheeny (Al) · #11 30-07-2007, 04:07 PM

Quote:

Originally Posted by iceman

After cropping, so that the moon is a reasonable size for display, there's no fine detail present as the Moon just didn't cover enough pixels on the CCD. It looks as if it's had too much noise reduction applied.

The attached result is cropped, sharpened and had levels adjusted.

Mike,

How much did you have to adjust the levels, and did you use spot metering to set your exposure just on the moon itself?

I don't doubt you probably did

... I'm just trying to throw up some ideas in case there's some room to move if getting more focal length is really out of the question...

Al.

iceman (Mike) · #12 30-07-2007, 08:35 PM

Hi Al
I took several test exposures and checked the histogram after each shot to get the exposure right. Nothing was over or under exposed - the exposure was just right. The levels were adjusted just to add a bit of contrast (darken the mare and lighten the rays).

I'm definitely not using that technique, the result is just not at the standard I set for myself.

I tried some alternatives tonight (involving a 12" and a dob

). I'll post the results tomorrow morning, chugging through Jupiter data now

Ingo · #13 30-07-2007, 09:17 PM

Not bad, great exposure, looks a little out of focus though. Use manual focus, and take a bunch of shots around the focus where it looks right on. I know I have to do this with my lens.

Also, I have found out on the lower end lenses canon and nikon make, 7.1 and up aren't their sharp points. I'm guessing the 75-300 is F4-5.6, so keep it on 5.6.