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Forum: Pentax K-1 & K-1 II 07-26-2017, 01:58 PM  
Settings on K-1 for the eclipse
Posted By Bob 256
Replies: 17
Views: 2,763
That's true about Samyang Mike. I think I heard somewhere that they make a couple of the CAT lenses but I'm not sure which ones. Probably a better bet than one of the unknown brands.

I don't know how much you would gain with PS. Unless you have a really sharp lens, it probably wouldn't be of benefit. There isn't that much detail in the partial phase and the total phase will show the corona and maybe some prominences which are kind of "whispy" anyway though better sharpness might be better to see fine details in the prominences. A complication is that the successive shutter actuations of PS could introduce some vibrations countering any improvements. I would test it ahead of time on a target like the moon and see if there is any advantage to PS shots (take a look at the small craters). The moon will also move like the sun so you can see if that introduces PS problems. Also, you can get some thermally induced distortions (heat waves) with the sun that could change each of the PS frames slightly causing ghosting artifacts. I don't plan to do any PS shots but will do substantial bracketing (another complication with PS is if you want to bracket).

I live in the totality zone near the Oregon border but plan to move north so I can get the full 2 minutes of totality. Where I am will only have 1 minute. Half of Boise might be moving with me so it could be a crazy day, especially after the eclipse. Will take camping gear & supplies just in case.
Forum: Pentax K-1 & K-1 II 07-25-2017, 09:59 AM  
Settings on K-1 for the eclipse
Posted By Bob 256
Replies: 17
Views: 2,763
Those are the ones.

The design uses a thin lens up front with a small circular spot in its middle that's aluminized to reflect light from the main mirror at the back. The rear mirror is spherical which is low cost to make and the lens corrects for most of the spherical aberrations of the mirror. These are also referred to as a "folded" optical system and are shorter than just having the main mirror in a tube like a Newtonian (standard type) reflecting telescope. It allows a focal length of 500mm in a lens much shorter than 500mm.

If the manufacture does their job well, this can be a pretty good lens (though less contrast than a refractive lens but that can usually be corrected in post-processing). The "CATS" that B&H carry are of Asian origin and may or may not be constructed so well. I really can't advise since I haven't used any and there may be variations between brands or even individual lenses, but there are some promising reports elsewhere (some in the Pentax forum) you might check if interested. Try Googling also.

The image quality would probably be on a par with most low cost telescopes and maybe even better since the "CAT" has better aberration correction (theoretically). They are certainly easier to handle because of their compact design. As you surmised, they probably won't stack up to a Sigma prime 500mm and they are slow compared to f5.6 or f4 (and have fixed aperture and no autofocus capabilities).

I would get or make a solar filter that fits over the front of the CAT. Alternately, you can buy a skylight or UV filter, remove the retaining ring with a spanner wrench and put a disc of solar filtering material in place of the glass, making sure there aren't any gaps at its edges when the retaining ring is screwed back in. I just mention the latter because of the short time, you may want to order a filter mount at the time you order the CAT if you choose to do so. The slip-on type filter changes faster than a screw-in filter though.
Forum: Pentax K-1 & K-1 II 07-25-2017, 06:51 AM  
Settings on K-1 for the eclipse
Posted By Bob 256
Replies: 17
Views: 2,763
A good lens would probably be better than or the equivalent of a telescope. Telescopes (particularly reflecting scopes) tend to have less contrast and may have more aberrations but on a cost basis, you can get a longer focal length for less money in a telescope. Most telescopes are higher f numbers so lenses tend to be faster and may be better at totality. Some higher priced refractors can have better performance than a camera lens but they are quite pricey.

I looked at the low cost Maksutov lenses (mirror optics) on B&H as a possible backup - they are around 500mm and as low as $95US. Their limitation is fixed aperture at around f8 but that's not a limitation for solar photography (though not the best for totality). Also, they are easily fitted for a solar filter. Another limitation might be image quality since most of these are not the best optics on the planet - I haven't any personal experience with one so I can't state how good they are but the K-1 would probably exceed their resolution capability - a cheap lens to consider in the right focal length ballpark though.

If you want to take a look at telescopes, I would recommend the Orion site (telescope.com) or Celestron. Orion offers low cost scopes and Celestron some higher end ones (Orion does also$$). You don't need a large aperture scope so even a 4 inch would work for the eclipse. Don't go too high in focal length or you'll lose out on the corona during totality.

Another consideration is a telescope will require a specialized mount since most won't mount on a regular tripod mounting so you may need to include a mount or adapter for a scope.

---------- Post added 07-25-2017 at 08:02 AM ----------



I'm not sure if you can bracket using the Astrotracer. It should work but in my own opinion, I wouldn't trust it for this one time event. If it decides not to work quite right, you won't have enough time to do anything else.

You should be fine during the partial phases with a static (non-tracking shot), and that will probably work during totality as well though you may need to boost ISO to keep the shutter speed in a usable range. The advantage of tracking is primarily so you are freed from having to move the camera or telescope to keep the sun in view. That's best applied over long term (throughout the 2 hour event) and the Astrotracer won't work that long in any case. For example, I have a camcorder which I want to use from the beginning to end of the entire eclipse - that's an application for tracking. Most of my other shots will be on a tripod.

To answer your question, however, yes the Astrotracer will track the sun (and the moon) since their motion is almost (but not quite) the same as the stars and the K-1 doesn't know if it's daytime or night when you use it, but I wouldn't use it in this case.
Forum: Pentax K-1 & K-1 II 07-22-2017, 02:03 PM  
Settings on K-1 for the eclipse
Posted By Bob 256
Replies: 17
Views: 2,763
I've also heard that, and in fact it can happen when an anti-shake servo "hunts" because of the very small error signal, but recently I shot some 500mm tripod shots with my K-1 (anti-shake on) and couldn't see any evidence of reduction in image sharpness. I did however, shoot some earlier shots on a tripod with SR on, and thought I saw some blurring I attributed to it though I had no comparison photos to substantiate that. Later, I saw something similar with SR off, so assumed the blurring was do to bad focus or some other factor.

It's probably best to turn it off with a tripod and not take any chances. If the tripod is doing its job and you've taken care not to touch the camera or tripod prior to the exposure, you shouldn't need shake reduction anyway. Also be sure you're on solid ground and there's no motion nearby, because vibrations can be carried through the ground and amplified by the tripod in certain cases. Best take your 6" concrete slab with you for those long tele shots:)
Forum: Pentax K-1 & K-1 II 07-17-2017, 01:05 PM  
Settings on K-1 for the eclipse
Posted By Bob 256
Replies: 17
Views: 2,763
Great shots and great exposure information. That will help many who are reading here to anticipate exposures for the main event. Were you using a guided mount to keep the image centered or did you adjust by hand each time? Good wishes for the August eclipse! Two great states to visit and explore when the eclipse is over.
Forum: Pentax K-1 & K-1 II 07-11-2017, 02:54 PM  
Settings on K-1 for the eclipse
Posted By Bob 256
Replies: 17
Views: 2,763
I would try to keep the ISO as low as possible (but settle with 200 as the lowest) so as to reduce noise in the image. You can experiment with that as well on the sun with your filter (for the partial phase). I would allow high shutter speed but if you find your ISO going 1600 or higher, begin lowering the shutter speed. Thermal effects will be minimal and with high ISOs, you'll find image noise more objectionable. Changing the ISO is no problem but again, give lower values preference if possible.

For totality, the same applies. You'll probably find the shutter speed going to pretty long values, especially for the lower bracket exposures, but again, I wouldn't worry that much as long as your mount is steady and you have the astro drive working. Be sure to wait after you reset the bracket value for vibrations to die out (about 5 seconds) before you take the shot and be careful not to move the telescope when you change the shutter speed (check the LCD in live view (which you should be using). Don't change the ISO for bracketing - use shutter speed, but feel free to vary the ISO when setting up the shot for the center bracket exposure.

You might see if you can lay your hands on a second camera to use with a lens. That way you don't need to bother your main setup, and you can get a few shots with a camera lens - always nice to have environment shots because of the shadow cone and the ambiance during totality (leaving a small video camera running is another idea).

In your practice, keep a watch on the time. It really is more important to take in the event but some photos are nice to have as a remembrance.
If nothing else, take one or two shots and then enjoy.

There is another US eclipse in 2024 so it's not the last opportunity but it's the only opportunity for the "Great American Eclipse" of 2017.

Good moon shot - the sun image will be almost identical in size as the moon for reference. Another target to practice on:)
Forum: Pentax K-1 & K-1 II 07-10-2017, 01:51 PM  
Settings on K-1 for the eclipse
Posted By Bob 256
Replies: 17
Views: 2,763
There are two basic phases of the eclipse - totality and everything else.

For the time leading up to totality and after, you probably want to get in close on the sun. I would use full-frame. Cropping in camera will not increase the resolution and that can always be done later. Before we get too far along, take special note: this phase of the eclipse can damage your eyes, your telescope, and your camera if proper filtering is not used! Whatever lens or telescope you choose, it needs a good solar filter in place before you even begin to use it (Thousand Oaks Optical is one source for solar filters). If you get a good fairly bright image looking through the telescope, that filter should work fine with the K-1. If the image is really dark, you might want a filter designed for photographic use which isn't as dense.

To fill the K-1 sensor to the edges (vertically), a focal length of about 2750mm is required. You don't need or want to go that far. I've used a 400mm lens with a 3x FL converter but a telescope is your best bet. A good lens at 1200mm will beat a poor one at 2400mm. The size of your telescope (4 inch versus 8 inch) won't particularly matter if the optical quality is good. Use your auto guider - it should track the sun just fine for the eclipse.

I would use manual mode and the histogram to set the exposure. With the telescope, you'll have a fixed aperture so the exposure will be set using shutter speed (and ISO). Set the top right function dial to ISO so you can change the ISO if needed with the top adj dial. The front adj dial will set shutter speed. Use your remote or timer to reduce vibrations when setting off the shutter (remote with live view is probably best for everything though you might need some shading to see the LCD clearly prior to totality). No shake reduction needed nor can it be used with your telescope so - OFF.

Practice on the regular sun with your filter in place. Use live-view with magnification to focus (push the enter button and then the rear dial for magnification). You should see some solar granulation which is a good goal for focusing (try focus peaking also to see if it helps). Since this phase is so contrasty, I wouldn't worry about the exposure too much - no HDR, no expanded dynamic range, no AA filter, no auto bracketing. Just try a few manual shutter speed changes and see what you get - PRACTICE! You'll be an expert in short order for the non-totality part and you have plenty of time to make exposure adjustments for this phase of the eclipse (boooringgggg).

Totality is another story. Your filter comes off (not before totality and get it back on before the end of totality!!!) and manual exposure should work best again once you get the right point using the histogram. I would definitely bracket this phase of the eclipse with about 5 or more brackets 2EV apart. You want to go over and under to catch the details (some photos I've seen, show the craters on the moon's dark side facing us). It assures you will have plenty of exposures to work with (but maybe you'll only use the best one), and you can incorporate them in an HDR later. The corona is quite bright so underexpose to catch its inner details, though overexposure is needed for its extreme edges. The focus won't change from what you used prior to totality, so don't worry about that unless you bump the focus by accident (maybe check it once to be sure). For totality, you want something considerably less than 2400mm (maybe half to one tenth that -maybe a regular telephoto lens) since the corona will extend from the sun a long distance, and you want to capture it all.

Practice on a distant street lamp at twilight and try to get the lamp details, and the background using bracketing. That should give you a taste and some ideas of what to do.

No composition adjust, no digital filter, no custom image. Keep it SIMPLE! 2 Minutes and counting...........

Basically, manual exposure - find the best histogram, click-click (2EV) below that, again, again, click-click (2EV) above best histogram, again, again using shutter speed . Pause each time to let vibrations stop (use a remote release so you don't have to touch the telescope or camera), watching through live-view. Done!

NOW - (get that solar filter back on or it's ADIOS K-1) and take in the event!!!!! Don't pass this once in a lifetime chance up with too much time at the camera.

One other note - have a good pair of binoculars with removable solar filters to take a closer peak yourself. Use some caution with the filtering and Good luck!
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