28th Aug - statically photographing the lunar eclipse progression
Hi all
Ive taken the liberty of attaching several images I've captured from my planetarium software (Voyager 4) showing the progression of the moon's path on the evening of August 28th from 17:00 to 00:00 in hourly increments. Sorry about the clarity - I didn't want to overdo the image sizes. You can still see the horizon and elevation descriptive labels...just...
What I'd like to know - if I may humbly ask - is what field of view I'd be likely to need (and hopefully what lens) from a statically-mounted camera taking photos every 15 minutes or so so that the first and last shots are hopefully in-frame at either end of the progression?
I plan to mount a DSLR on a tripod and time it so that I take an exposure every 15 minutes. I don't want to move the camera as the moon moves through its arc.
I assume you want just the umbral phase? It lasts approx 3.5 hours from 18:50 to 22:20 I believe. Using very rudimentary maths (which may be completely wrong), I would guess that the moon would move 360 x (3.5/24) = 52 degrees during that time. I'm not sure what focal length gives that much coverage, but you could roughly work it out by measuring 52 degress of azimuth from your location and then seeing what lens will be wide enough. I'm sure someone more technical than me will work this out properly.
I imagine the moon will be pretty small in the shots with a relatively wide angle lens. I'd be tempted to shoot the moon with a long lens or telescope and add it to a foreground shot digitally. Whether you keep the relative size of the moon realistic is up to you!
Hi Morton I do want to go with the full penumbral phases included if I can fit it all. I guess that 50-odd degrees will be no problem and still give a reasonably-sized moon in frame.
Don't forget that the Moon has a real movement against the background stars too; it actually moves from West to East against the backdrop of stars at a rate of about 13 degrees in 24 hours.
Here is a simulation in Starry Night pro V6 showing the FOV for my Pentax *ist DS with a 50mm lens. I set the time as shown to show the coverage from diagonal to diagonal.
It looks like you will need a much wider lens to capture the whole sequence, resulting in quite a small Moon. I’ll run a 28mm scenario later on and post the results.
Here is a simulation in Starry Night pro V6 showing the FOV for my Pentax *ist DS with a 50mm lens. I set the time as shown to show the coverage from diagonal to diagonal.
It looks like you will need a much wider lens to capture the whole sequence, resulting in quite a small Moon. I’ll run a 28mm scenario later on and post the results.
Cheers
Dennis
Wow Dennis - that's superb! It's exactly what I was after. Thank you!! I'll experiment with Voyager to see if it can deliver anything similar or not...
How did SN6 simulate the *ist DS with a 50mm lens? Are there tables within it or something? I have the 18-55mm kit lens for my Nikon, so I gather that it gives around an 80-degree field of view.... I estimate ....
In Starry Night pro V6 you can manually create FOV indicators as well as select telescope, eyepiece and ccd pre-sets as installed with the software.
I created the Pentax *ist DS 50mm at 18 deg wide x 26 deg high (i.e. portrait mode.)
With the 18mm lens I created the FOV as 60 x 45 degrees.
Cheers
Dennis
PS – the attached file was created in Photoshop by doing a screen print for 6:30 through 10:30 and then pasting each screen print as a layer. I then rubbed out selected areas on each layer, to reveal the Moon underneath, so that the final result shows the Moon at those time intervals.
Last edited by Dennis; 15-08-2007 at 08:35 PM.
Reason: WAS: Photopaint. NOW IS: Photoshop.
Chris have a look at this image which sounds like what you want to do.
With a crop factor of around x1.5 or x1.6 on a DSLR I'd say around a 24mm FL will give you a similar result of a full frame camera with 35mm FL lens.
According to the book here in my lap, Astrophotography by H.J.P Arnold, a 50mm lens has a 27 degree vertical and a 40 degree horizontal field of view therefore a large part of the eclipse can be encompassed within it. You'll capture approx 2 hours of the eclipse in the FOV.
Personally, I'm not going to bother with the penumbral phase and just concentrate on the good bits.
Good Luck and Clear Skies!
I think the HP Arnold book was probably written in the era of 35mm SLR astro photography? If so, the field of view needs to be “adjusted” when using DSLR’s due to the DSLR “crop factor” from having a smaller sensor.
An SLR lens on a 35mm film SLR fully illuminates the 35mm negative (36mm x 24mm). My Pentax DSLR has a chip that measures only 23.5 x 15.7 and modern DSLR lenses are designed to illuminate this smaller frame.
My Pentax *ist DS has a crop factor of x1.5, whereas the consumer Canon DSLR’s seem to use x1.6 I think?
So, if I fit a 200mm lens on a 35mm film SLR and print the (36x24mm) negative to say, 10”x8”, then fit the same lens on my DSLR, I will have to enlarge the (23.5x15.7mm) DSLR image more to make it 10”x8”, hence the illusion that the 200mm SLR lens “appears” to “behave” like a 300mm lens on the DSLR.
So, to cut a long story short, Arnold’s (27x40 degree) 50mm lens on my Pentax *ist DS DSLR will give me a FOV of only approx 18x27 degrees, “behaving” more like a 75mm lens.
Well, in hindsight I'd say that a photo every 5 minutes will probably faithfully capture the progression nicely.
That's what I tried to do. I almost got half way doing it before the heavens opened up with rain.
If you photographed it you'll probably notice that there are few discernible features at the margins of the shadow. I assume there are no discernible features because a direct light at almost 0 degrees casts no shadow(?)
I got mare as the moon dulled, and there was a prominent crater near one of the poles which stood out. Apart from those features, it wasn't what I thought it would be.
I thought it would provide images of craters offset by their shadows. But that didn't seem to happen. Perhaps it is a question of time when it comes to getting the right image. I must admit I haven't seen any hugely cratered images. Just lots of images involving the mare.
- on the film in the camera - cross fingers I got the bracketed exposures right. Will develop it soon.
