[jatrax]

He applauds pentax, chides Nikon and canon, but says ultimately it won't shift the dial. At least, that is his view.

And I thought that was fair. Dedicated Nikon or Canon shooter will need a lot of persuasion to jump to Pentax. The fact that he even considered it in the article is a milestone for Pentax. You need mind share before you can get market share. Every mention of Pentax in this context is a very good thing IMHO. Just emphasizes that Pentax is alive and in this writers opinion compares quite favorably to Canon or Nikon. Maybe not enough to make him switch but enough to be considered on the same field.

[Pete_XL]

We here say "Versuch macht klug" what should be the same as "learning by doing" in your language. A friend of mine owns the new Olympus O-MD E M5 Mark II which does pixel shift as the first camera in the world as far as I know. I will try to persuade him to borrow it for a test with pixel shift and Skywatcher when the moon is less disturbing than it is at the moment. I will report.

I could not acquire the Olympus for a Pixel shift test yet but hat a chance to test the precision of the Skywatcher Star Adventurer (small eq. mount) with last night to get a feeling, if the acuracy could be in the range needed for the new pixel shift technology together with astrophotos and "small equipment".


After a god but not perfect polar alignment and on a shaky tripod I shot for 2.5 hrs with K5 and my 200 mm lens at F4.2 ISO 640 with 3 minutes of exposure each, letting the system track without changing the setup. To get the total tracking error calculated I took the first and last pichture of the series and measured the distance between identical points (stars) in the two pictures. This is what I found:


The accumulated error shift distance after 9.150 seconds (ca. 2.5 hrs) was only 101 pixels! This is 0.66 pixels per minute or 91 seconds exposure with 1 pixel error.

I am sure that with a more precise polar alignment this could even be much better.

My conclusion is that pixel shift technology in the K-3 II could really work together with a precise equatorial mount, especially with shorter lenses.

At least in theory because practically I once more had to realise that lack of focus should be the limiting factor with long standard lenses in astrophotography together with pixel-shift. I did what I could in focusing with live view loupe but it was not enough in the end. The degree of focus blurring was higher than the degree of shift by tracking inaccuracy within the 3 minute exposures. I will always use my self made bahtinov-mask to get optimal focus in future - this time I was (again) too lazy for that.

[Pete_XL]

When they integrate Astrotracer into the new K-3 II it would be great if they allowd to use it together with interval shooting mode.


The standard technology in astrophotography is to take sets of photos and stack them later to obtain the final image. I often shoot dozens of photos of one object.


Using the Astrotracer you have to press OK after each and every single photo, having to stand near the camera all the time and getting cold in winter time. If you forget or miss the button you have to got through the whole menu again. This is extremely inconvenient and annoying.


I believe it should be an easy job for the Ricoh/Penty engineers to fix that in the new Version and allow combining it with internal interval mode. The greatest thing and perhaps easiest way would be if the Astrotracer could be triggered by remote control.

[novsky]

When they integrate Astrotracer into the new K-3 II it would be great if they allowd to use it together with interval shooting mode.


The standard technology in astrophotography is to take sets of photos and stack them later to obtain the final image. I often shoot dozens of photos of one object.


Using the Astrotracer you have to press OK after each and every single photo, having to stand near the camera all the time and getting cold in winter time. If you forget or miss the button you have to got through the whole menu again. This is extremely inconvenient and annoying.


I believe it should be an easy job for the Ricoh/Penty engineers to fix that in the new Version and allow combining it with internal interval mode. The greatest thing and perhaps easiest way would be if the Astrotracer could be triggered by remote control.

+1 hope that engineers will fix that soon...

[Dr. Zee]

Went out to catch the meteor shower last night. It was a bust, so I spent 3 hours dicking around with Astrotracer and Bulb Mode. I found that any exposure longer than 10 seconds led to a star trail. Can anyone else corroborate?

I was shooting at 120mm, I guess it's possible that the effect would be reduced with a shorter focal length. I'm in Chicago and was shooting a planet that was barely visible at 120mm anyway.

For the more experienced star photographers here, what is the purpose of taking multiple shots and stacking them? Also, does anyone have techniques for getting sharp focus on a star? They seem to confuse the AF, and the difference between soft and sharp seems to be less than a mm on the throw.

[jatrax]

I was shooting at 120mm, I guess it's possible that the effect would be reduced with a shorter focal length. I'm in Chicago and was shooting a planet that was barely visible at 120mm anyway.

I am no expert on this but I do know that focal length has an impact. The longer the focal length the shorter the possible exposure without trails. Based on my limited use of the Astrotracer I think 10 seconds is about right for that focal length. I have used 50mm up to about 20 seconds with out trails.

[Quicksand]

Went out to catch the meteor shower last night. It was a bust, so I spent 3 hours dicking around with Astrotracer and Bulb Mode. I found that any exposure longer than 10 seconds led to a star trail. Can anyone else corroborate?

I was shooting at 120mm, I guess it's possible that the effect would be reduced with a shorter focal length. I'm in Chicago and was shooting a planet that was barely visible at 120mm anyway.

Ah, I can't find it now but there's a chart somewhere -- perhaps in the O-GPS1 documentation -- that lists how long you should be able track based upon lens focal length and declination, I think.

And I'm pretty sure at 120mm you should be able to have the shutter open for a couple of minutes. In any case, much longer than ten seconds, even if you're pretty conservative. You might have a calibration issue.

[mattt]

Ah, I can't find it now but there's a chart somewhere

I believe this is the post you are refering too

https://www.pentaxforums.com/forums/22-pentax-camera-field-accessories/187813...ml#post2743629

[Dr. Zee]

Ah, I can't find it now but there's a chart somewhere -- perhaps in the O-GPS1 documentation -- that lists how long you should be able track based upon lens focal length and declination, I think.

And I'm pretty sure at 120mm you should be able to have the shutter open for a couple of minutes. In any case, much longer than ten seconds, even if you're pretty conservative. You might have a calibration issue.

I was shooting west at roughly a 70 degree angle. A 30 second exposure with the Astrotracer produced about 1/3 as much trail as without. But still, that would have to be a heck of a calibration issue.

[Pete_XL]

For the more experienced star photographers here, what is the purpose of taking multiple shots and stacking them? Also, does anyone have techniques for getting sharp focus on a star? They seem to confuse the AF, and the difference between soft and sharp seems to be less than a mm on the throw.

The main purpose of stacking is to increase the Signal to Noise Ratio (SNR). The series of shots is shifted and rotated to get the stars (=signal) aligned and on top of each other and the "flattened" down to one single picture. In this process the signal persists or is even amplified while the noise is reduced significantly (by effects of math -> median, averaging, etc). Stacking enables you to use high ISO values and shorter exposure times especially for dark objects (e.g. nebula). A single shot of 10 s at ISO 800 might not catch enough photons to show the object. A single shot of 10 s at ISO 3200 would be too noisy to be used. But the stacked result of 100 such shots would show only little noise and sharpened stars, you see objects that never could be noticed in a sigle frame. take so called "darks" with the same camera settings and with lens cap on at the end of the series. Darks contain the sensor noise and are used by the stacking software to further reduce noise. A good and easy-to-use freeware is DeepSkyStacker. Shoot in RAW, pass the shots as 16 bit TIFF-files to the stacking software. Instructions on how-to-stack are a lot in the web.

Stars are tricky in matters of sharp focus. Good focus on stars is not possible with AF. Better use manual focus and live view. Being in the live view mode use the 10x loupe to get into good focus. Close the aperture one stop. Do test shots, use zoom to control the results and iterate until stars are pin-point-sharp. Use remote control and mirror lockup to avoid vibration blur. It is very important to turn of the Image Stabilisation (if it is not automatically turned of by camera)!!

[Dr. Zee]

The main purpose of stacking is to increase the Signal to Noise Ratio (SNR). The series of shots is shifted and rotated to get the stars (=signal) aligned and on top of each other and the "flattened" down to one single picture. In this process the signal persists or is even amplified while the noise is reduced significantly (by effects of math -> median, averaging, etc). Stacking enables you to use high ISO values and shorter exposure times especially for dark objects (e.g. nebula). A single shot of 10 s at ISO 800 might not catch enough photons to show the object. A single shot of 10 s at ISO 3200 would be too noisy to be used. But the stacked result of 100 such shots would show only little noise and sharpened stars, you see objects that never could be noticed in a sigle frame. take so called "darks" with the same camera settings and with lens cap on at the end of the series. Darks contain the sensor noise and are used by the stacking software to further reduce noise. A good and easy-to-use freeware is DeepSkyStacker. Shoot in RAW, pass the shots as 16 bit TIFF-files to the stacking software. Instructions on how-to-stack are a lot in the web.

Stars are tricky in matters of sharp focus. Good focus on stars is not possible with AF. Better use manual focus and live view. Being in the live view mode use the 10x loupe to get into good focus. Close the aperture one stop. Do test shots, use zoom to control the results and iterate until stars are pin-point-sharp. Use remote control and mirror lockup to avoid vibration blur. It is very important to turn of the Image Stabilisation (if it is not automatically turned of by camera)!!

So minimizing noise while avoiding rotation blur. Good to know.

I had no idea the 10x loupe existed! Thank you very much.

Why turn off optical stabilization?

[jatrax]

Why turn off optical stabilization?

Assuming you are on a tripod, which you would be for this, the SR feature tries to eliminate shake when there is none and actually introduces motion. Check the manual, Ricoh advises turning off SR when on a tripod. Also, some modes assumed to be used on a tripod( remote and 2 sec delay) automatically turn off SR.

I forgot one day and took about 200 shoots of some Big Horn sheep, on a tripod in perfect light while they were just plainly posing for me at about 75 yards distance. All the shots exhibited slight softness from blur introduced by the SR mechanism. A lesson I will not forget again.

[Pete_XL]

I forgot one day and took about 200 shoots of some Big Horn sheep, on a tripod in perfect light while they were just plainly posing for me at about 75 yards distance. All the shots exhibited slight softness from blur introduced by the SR mechanism. A lesson I will not forget again.

Yep! Blurred sheep and stars .......... because SR is designed for use without tripod and is "confused" when there is absolutely no shaking and beginns to vibrate itself. The same happens using lenses with own internal OIS system on a tripod.

[UserAccessDenied]

Assuming you are on a tripod, which you would be for this, the SR feature tries to eliminate shake when there is none and actually introduces motion. Check the manual, Ricoh advises turning off SR when on a tripod. Also, some modes assumed to be used on a tripod( remote and 2 sec delay) automatically turn off SR.

I forgot one day and took about 200 shoots of some Big Horn sheep, on a tripod in perfect light while they were just plainly posing for me at about 75 yards distance. All the shots exhibited slight softness from blur introduced by the SR mechanism. A lesson I will not forget again.

I love the SR but sometimes I forget to turn it off when shooting from a tripod. Even shooting off a monopod at times I notice the SR can introduce blur in the images if I'm very still when shooting.

But this just goes to show me that once again the fault lies not at the sensor, but 12" behind the sensor...

[Dr_who]

How pixel shifting and astrophotography fit together is a very good question.

I just assumed that pixel shift and astrotracing work so well together that they had to go together in the new camera. If they are incompatible, it makes Ricoh's decision to replace the onboard flash with the GPS unit more odd (as this camera is an update to the K-3, which has an onboard flash).

I wouldn't think of using the pixel shifting with astrophotography as exposures are often in the 4-5 minute mark, and to do 4 shifts all at 4 minutes. Also most astrophotography stacking programs debayer the raw files before stacking anyhow.