Mirror lenses for eclipse

I am going to be viewing the total solar eclipse in November, so am looking for a lens to put on my 600D to take some photos of it.

I have done some test shots of the moon with an old FD 500mm reflex lens with an adapter, and I think that 500mm should be about right as a focal length (i.e. allowing enough space around the moon to see the corona during totality).

I don't have a 500mm refractive lens, and am not looking at spending thousands of dollars to get one at this time (currently, I don't shoot wildlife or birds).

Hence my interest in mirror lenses. I understand that they have optical defects (sharpness, donut bokeh) and limitations (fixed aperture), but most of those are no problem for astrophotography (excepting sharpness, which was acceptable from the FD lens I tested on a moon shot). I'm not interested in a mirror lens as a telephoto lens for general use, but they are so cheap that it makes sense to get one as a small telescope to put on the front of my camera.

My question is essentially this - there are a bunch of cheap mirror lenses for sale on (e.g.) B&H - e.g. Samyang, Rokinon, Vivitar, Bower - they all look very similar (I assume that at least some of them are the same lens rebadged) - and there is little comparative information online. Is there any difference in quality between them? Can anyone with direct experience help?

Alternatively, is there a cheap way of getting to 500mm with better IQ, apart from sticking a 2x extender on a 55-250 (at about 4x the price of the mirrors?).

--
Cheers,
Damien

You are correct: mirror lenses are a really good choice for eclipse photography: compact, cheap for the focal length and manual focus and bokeh is irrelevant for this. Here is a collage I did some years ago using a Yashica 500/8:



(the partial phases and the corona!). If you will be happy with NEW cheap off-brand lenses I dont know but the USED marked for Nikon, Canon, Contax, Yashica... could be helpfull. Look at ebay. These lenses are robust!

Franz

Maybe you know this already: http://advancedphototech.wordpress.com/lenses/mirror-mirror-a-guide-to-choosing-and-using-mirror-lenses/

There the tamron 500mm looks good!

dodgyexposure said:

I am going to be viewing the total solar eclipse in November, so am looking for a lens to put on my 600D to take some photos of it.

I have done some test shots of the moon with an old FD 500mm reflex lens with an adapter, and I think that 500mm should be about right as a focal length (i.e. allowing enough space around the moon to see the corona during totality).

I don't have a 500mm refractive lens, and am not looking at spending thousands of dollars to get one at this time (currently, I don't shoot wildlife or birds).

Hence my interest in mirror lenses. I understand that they have optical defects (sharpness, donut bokeh) and limitations (fixed aperture), but most of those are no problem for astrophotography (excepting sharpness, which was acceptable from the FD lens I tested on a moon shot). I'm not interested in a mirror lens as a telephoto lens for general use, but they are so cheap that it makes sense to get one as a small telescope to put on the front of my camera.

My question is essentially this - there are a bunch of cheap mirror lenses for sale on (e.g.) B&H - e.g. Samyang, Rokinon, Vivitar, Bower - they all look very similar (I assume that at least some of them are the same lens rebadged) - and there is little comparative information online.

Click to expand...

they are all the same, made by samyang
The Samyang 8mm fish-eye is sold under many names:
http://photonius.wikispaces.com/Fish-eye%2C+Panorama%2C+Stitching

Other brands are I think all discontinued, except perhaps the Sony, but you can get them on ebay.

Is there any difference in quality between them? Can anyone with direct experience help?

dodgyexposure said:

Alternatively, is there a cheap way of getting to 500mm with better IQ, apart from sticking a 2x extender on a 55-250 (at about 4x the price of the mirrors?).

Click to expand...

No teleconverters fit EF-S lenses so far, unless it's possible to pop off the back part of the 55-250 IS like on the Canon EF-S 10-22.

dodgyexposure said:

--
Cheers,
Damien

Click to expand...

--
Life is short, time to zoom in ©

Thanks - those images are what I am looking for. Did you use a solar filter for the partial shots? From what I can glean from astro sites, threaded filters aren't available in large enough sizes (95mm seems to be a common filter thread size for the mirrors), but the telescope cap type filters (say, a 100mm) might be the go.
--
Cheers,
Damien

photonius said:

they are all the same, made by samyang

Click to expand...

That makes sense.

photonius said:

No teleconverters fit EF-S lenses so far, unless it's possible to pop off the back part of the 55-250 IS like on the Canon EF-S 10-22.

Click to expand...

My inexperience showing - I have no TCs, and I chose the 55-250 for this example because it is cheap and, well, 250 is half of 500. Is there a budget option that would work in getting to 500mm+?

--
Cheers,
Damien

The other posters have discussed mirror lenses more thoroughly than I could, but a decently priced refractive lens solution is Canon's 400/5.6. It's still quite sharp with a 1.4x TC attached. The only downsides are that it loses AF with the TC attached (on most bodies), it's rather slow at 560/8 (which you won't care about for eclipse photography on a tripod), and at ~$1100 on the used market (including TC) it's more expensive than the mirror lenses you're considering.

Lots cheaper than a 500-800mm supertele though. And after the eclipse is over it'll make a really nice lightweight wildlife lens.

500mm is not going to give you a very large image of the sun/eclipse

You're looking at needing 1200mm to get a decent image size, even on a crop sensor.

Your best bet is to rent a 600 f4 L and a Canon 2x - also a very sturdy tripod and gimbal mount.

You'll also need a cable release, and a sun filter

The sun filter should be a 'mylar' type, which you can size to fit over the 600 f4L hood.

Astrozap make good ones.

With this set-up you'll get a shot at some decent images - but focus and exposure will be very very difficult during eclipse - so bracket a lot!

Sample from 5DII using 600 f4L and 2x, plus solar filter - Venus Transit



Set-up on gimbal





--
http://www.dodkin.com
[email protected]
Mac Pro/MacBook Pro/iPods/iPhones/iPad

Thanks for your reply.

Is that sun shot cropped? Otherwise, 1200mm looks to be too tight on my crop sensor for coronal shots . . .

And what happened to the back leg of your tripod? It looks like it disappears halfway to the ground!
--
Cheers,
Damien

Yep - that's a crop image

The formula for determining the size of the lunar/solar images on a 35mm sized sensor is found by dividing the focal length (in millimeters) by 109 to arrive at the lunar diameter (in millimeters) on the sensor.

So for a full frame like the 5DII with 600 and 2x - I got 1200mm/109 = 11mm diameter

Or on a crop you'd get 17mm diameter

Now your sensor might only be 22.3x14.9mm, so going with the 1.4x extender instead of the x2 with the 600 f4L might be better

You'd get 840/109 * 1.6 = 12.33mm diameter

500mm lens alone would get you 500/109 * 1.6 = 7.3mm diameter - rather small!

The tripod 'leg' you're looking at is actually the center column - otherwise it would haven fallen over!!
--
http://www.dodkin.com
[email protected]
Mac Pro/MacBook Pro/iPods/iPhones/iPad

Chris Dodkin said:

Now your sensor might only be 22.3x14.9mm, so going with the 1.4x extender instead of the x2 with the 600 f4L might be better

Click to expand...

The problem with hiring a 600 is that no one that I can find in Brisbane (Aus) rents longer than a 300 lens. And for the price of renting a 300/2.8 for a week, I could buy 2 mirrors . . .

Member said:

You'd get 840/109 * 1.6 = 12.33mm diameter

500mm lens alone would get you 500/109 * 1.6 = 7.3mm diameter - rather small!

Click to expand...

Thanks for the calculation. Diameter about half of the shorter side of the sensor sounds about right to get the corona in shot (i.e. the 500mm lens) - is there something that I'm missing?

Member said:

The tripod 'leg' you're looking at is actually the center column - otherwise it would haven fallen over!!
--

Click to expand...

Ha! I see the leg now - I thought that you had a nifty invisible tripod leg.

--
Cheers,
Damien

dodgyexposure said:

photonius said:

they are all the same, made by samyang

Click to expand...

That makes sense.

dodgyexposure said:

No teleconverters fit EF-S lenses so far, unless it's possible to pop off the back part of the 55-250 IS like on the Canon EF-S 10-22.

Click to expand...

My inexperience showing - I have no TCs, and I chose the 55-250 for this example because it is cheap and, well, 250 is half of 500. Is there a budget option that would work in getting to 500mm+?

Click to expand...

Alas, not really, been looking myself for years. Always end up with something like the canon 100-400, or, considering a bridge camera, some of these go to 1000mm quivalent now, and I guess you can set ISO 100 with the right filter.

dodgyexposure said:

--
Cheers,
Damien

Click to expand...

--
Life is short, time to zoom in ©

On a crop 500mm is just perfect to get also the corona! To document the partial phases this is also enough! Lets take a 7D. Its 4.3micron pixel corresponds to 1.8 arcseconds. Keeping in mind all the needs for a very stable (tracking for the corona exposures!) mount and a stable atmosphere I would in your case not overdo it and enjoy the eclipse with "easy" equipment like such a small mirror lens. Another important add: photographic lenses are NOT the most cost effective lenses for astronomy. For the money of an L supertele you get a much better astronomical telescope for the purpose. To have autofocus, IS, correction for all distances leeds to a suboptimal compromise for astronomical work...

Not to forget: as solar filter I use the Baader Astro solar films that are easy to fit all sizes... http://www.baader-planetarium.com/sofifolie/sofi_start_e.htm

Clear skies!

I second the 400/5.6 + 1.4x suggestion since this is a very versatile wildlife lens too! Can be an investment for a long time! (again manual focus when using the 1.4x is not problem here!)

There's something wrong here - the image size is the same regardless of the sensor size.

Chris Dodkin said:

The formula for determining the size of the lunar/solar images on a 35mm sized sensor is found by dividing the focal length (in millimeters) by 109 to arrive at the lunar diameter (in millimeters) on the sensor.

So for a full frame like the 5DII with 600 and 2x - I got 1200mm/109 = 11mm diameter

Or on a crop you'd get 17mm diameter

Now your sensor might only be 22.3x14.9mm, so going with the 1.4x extender instead of the x2 with the 600 f4L might be better

You'd get 840/109 * 1.6 = 12.33mm diameter

500mm lens alone would get you 500/109 * 1.6 = 7.3mm diameter - rather small!

The tripod 'leg' you're looking at is actually the center column - otherwise it would haven fallen over!!
--
http://www.dodkin.com
[email protected]
Mac Pro/MacBook Pro/iPods/iPhones/iPad

Click to expand...

If you're not already a member, I can recommend joining this group:

http://tech.groups.yahoo.com/group/SEML/

Many of the top eclipse chasers are members of this group; some have seen 15 or more.

I don't know specific lenses to recommend, but I can give some tips:

1. Go on the smallish side. If the goal is the corona, you'll want a large enough field of fiew to cover it. You can always crop your shots, and more importantly, the sun will stay in the field of view longer. It can be tough keeping the sun in the field of view with a very large lens (assuming you don't have a tripod that tracks the sun)

2. How long is the totality from your location?

3. Related to #2: PRACTICE! Set up your equipment as if it's the real day. Have someone time you with a stopwatch. At the end of your practice routine, ask yourself:

Had that been the real eclipse, 1. Would I be satisfied with the pictures I took? 2. Did I take time to really LOOK at the eclipse? 3. Did I take time to look at the other features of the eclipse (darkened sky, other people reacting, etc.)

Practice it multiple times until the flow is seamless. You do NOT want to spend so much time with photography that you don't look.

4. if you have a second camera, consider setting it up and do wide angle shots of the eclipse above the surrounding landscape.

5. consider having a prerecorded message on an audio recorder playing to prompt yourself

6. Don't forget to remove the solar filter for totality!

7. If something goes wrong, don't fight it for too long. Just get a few snapshots and enjoy the view. NOTHING compares to seeing a total solar eclipse.

Good luck!

Steve Balcombe said:

There's something wrong here - the image size is the same regardless of the sensor size.

Click to expand...

You are correct. I think that the 1.6 multiplier should only be applied when considering the size of the moon in the final image (i.e. percentage of sensor), not its size on the sensor in mm.

--
Cheers,
Damien

Thanks for your great tips. I have done some online reading about eclipse photography, and it seems to attract some very committed devotees.

Totality should be about 4 minutes where we will be, and I am not planning to be taking photos for the entire time.

I'm practising by taking moon shots. From my reading, I think that the exposure is similar for shooting during the eclipse, and setting up and shooting in the dark should be good practise. Once I get a lens and a solar filter, I will also try some sun shots.
--
Cheers,
Damien

Franz Kerschbaum said:

On a crop 500mm is just perfect to get also the corona! To document the partial phases this is also enough! Lets take a 7D. Its 4.3micron pixel corresponds to 1.8 arcseconds. Keeping in mind all the needs for a very stable (tracking for the corona exposures!) mount and a stable atmosphere I would in your case not overdo it and enjoy the eclipse with "easy" equipment like such a small mirror lens. Another important add: photographic lenses are NOT the most cost effective lenses for astronomy. For the money of an L supertele you get a much better astronomical telescope for the purpose. To have autofocus, IS, correction for all distances leeds to a suboptimal compromise for astronomical work...

Click to expand...

I have looked briefly into telescopes, and the longer focal lengths seem to be a better option for astrophotography generally, but not essential for moon and eclipse shooting. And, like lenses, there is a wide range of quality and prices. And then there are the tracking mounts! I don't need another expensive hobby just now!

Franz Kerschbaum said:

Not to forget: as solar filter I use the Baader Astro solar films that are easy to fit all sizes... http://www.baader-planetarium.com/sofifolie/sofi_start_e.htm

Clear skies!

Click to expand...

--
Cheers,
Damien

"Totality should be about 4 minutes where we will be"....

You seem to be doing the right thing in preparing for the big event, but, unless you're on a ship, don't expect 4 minutes of totality. If you're on land in Australia, then expect more like 2 minutes. This may affect your plans a bit.

If you are on a ship, that may affect your lens choice because of the stability issues.

dodgyexposure said:

Steve Balcombe said:

There's something wrong here - the image size is the same regardless of the sensor size.

Click to expand...

You are correct. I think that the 1.6 multiplier should only be applied when considering the size of the moon in the final image (i.e. percentage of sensor), not its size on the sensor in mm.

Click to expand...

As Chris Dodkin hasn't come back yet, here's a calculation of the actual image size on the sensor:

Angular size of the sun is (from Wikipedia) about 32' (32 minutes of arc) or 0.53 degrees. The moon varies a bit either side of that, which is why we get annular eclipses, so let's use the figure for the sun.

The size of the projected image is:
focal length * (2 * tan(0.53 * pi/360))

Which works out at 11.1 mm for the 1200 mm lens in Chris's example. So his figure for full frame is correct, but it doesn't change for crop.