New full frame Pentax K1 has an astro tracking feature

[gregbradley]

Using the sensors stabilisation system and GPS and electronic compass it can track when doing a long exposure. This has been available on their APSc models.

Could be an interesting camera for nightscapes. No need for a Polarie or equivalent.

It also has that yummy 36mp Sony sensor that is soooo good.

http://www.dpreview.com/news/7158808396/worth-the-wait-a-look-inside-the-pentax-k-1?slide=10

Greg.

[glend]

I wonder about who is guiding development of these new DSLRs and what they see as their business objectives. An auto tilting sensor sounds like a precusor to AO, and all the complexity that goes with it. It would be a nightmare for the DSLR mod guys.
Can't find any mention of the size of each of those many pixels. In past model releases, when trying to pack ever more pixels into a standard sensor size (whether APS-C or Full Frame) they are of course constrained by the physical dimensions of the sensor, so they work to make each pixel ever smaller to crow about the increase in pixel numbers. I am not sure this is great news to those that might prefer the larger pixel sizes in past models.
Like past 'astro' models, will this be a limited production release to gauge market interest or something that will become mainstream? Sorry if this seems a 'downer' to some but increasing complexity doesn't excite me; give me a DSLR with a great sensor, low read noise, deep wells, etc and none of the daytime filters, and better still give me a mono option.

[gregbradley]

The Pentax K1 is a mainstream camera release and is not an astrophotography targeted camera.

Its a full frame DSLR for popular use.

It happens to have this astro tracer function which is ideal for nightscapes and for those using Vixen Polarie mounts.

As far as the sensor even though its an older Sony 36.4mp Exmor sensor its still light years ahead of anything Canon has. Exmor can give clean shadows that you can boost with no noise unlike competing Canon sensors (Canon is getting better though but Sony is surging ahead leaving them further behind).

Pixel size? It seems counterintuitive but each new gen of DSLR/Mirrorless seems to get more pixels and lower noise. The Canon 50mp 5DSR has better noise than 5D3. So manufacturers look for ways to improve the sensor, get more megapixels and lower noise so high ISO is less noisy.
Full frame sensors are 2.5X larger in area than APSc so 36mp full frame would have larger pixels than 18mp APSc.

This Sony 36mp sensor is a gem, I have used one in 2 different cameras now for 3 years. Awesome.

Sony has done this by using thinner copper wiring instead of the usual aluminium giving faster cleaner readouts plus it can make the sensor stack thinner which allows more light into the same pixel, by using back illuminated sensors, by having the analogue to digital converters on the chip itself and other electronic tricks.

Greg.

[rustigsmed]

I wonder how far the sensor could track till it starts degrading the image

[OzEclipse]

The Pentax astrotrace function is interesting and convenient when traveling in that the GPS unit is the size and weight of a matchbox.

I hae used it with my Pentax K5 APSc DSLR.

The tracking/exposure time is limited by the available movement of the sensor. Longer focal lengths have shorter max time than short focal lengths. Multiple subs are out because the sensor resets after each exposure.

The XY movement of the sensor can't exactly cancel the rotational sky motion. However it does a reasonable job. It does not replace or surpass the performance of a good equatorial tracking device or mount. I view it as a traveling convenience rather than something I use as a mainstay tracking technique.

You can see an example here, about 3/4 of the way down the page there is a 300s exposure with a 12mm lens.

http://www.joe-cali.com/eclipses/PAST/ASE2013/index.html

To activate it you have to do a precise calibration of the GPS. After turning it on you select precise calibration then you have to slowly rotate the camera 360 deg with GPS turned on in 3 Cartesian axes (X,Y,Z). This allows the GPS then sense pointing direction. The processor then computes how to minimize sky motion by 2D movement of the sensor. It's not as bad as guiding on an alt-az mount because the camera is pointing at the sky.

In the example, you'll see linear motion in top right and lower left corners which is an artifact of this strange tracking.

Cheers

Joe

[OzEclipse]

The Pentax astrotrace function is interesting and convenient when traveling in that the GPS unit is the size and weight of a matchbox.

I hae used it with my Pentax K5 APSc DSLR.

The tracking/exposure time is limited by the available movement of the sensor. Longer focal lengths have shorter max time than short focal lengths. Multiple subs are out because the sensor resets after each exposure.

The XY movement of the sensor can't exactly cancel the rotational sky motion. However it does a reasonable job. It does not replace or surpass the performance of a good equatorial tracking device or mount. I view it as a traveling convenience rather than something I use as a mainstay tracking technique.

You can see an example here, about 3/4 of the way down the page there is a 300s exposure with a 12mm lens.

http://www.joe-cali.com/eclipses/PAST/ASE2013/index.html

To activate it you have to do a precise calibration of the GPS. After turning it on you select precise calibration then you have to slowly rotate the camera 360 deg with GPS turned on in 3 Cartesian axes (X,Y,Z). This allows the GPS then sense pointing direction. The processor then computes how to minimize sky motion by 2D movement of the sensor. It's not as bad as guiding on an alt-az mount because the camera is pointing at the sky.

In the example, you'll see linear motion in top right and lower left corners which is an artifact of this strange tracking.

Cheers

Joe

[rustigsmed]

thanks Joe - i was thinking there must have to be some kind of artifact, was it going to be alt az like or something else!?

[RickS]

A little arithmetic shows that the pixel pitch is around 4.9 um - comparable to the sensors in many popular astro cameras.

Cheers,
Rick.

[gregbradley]

Also the idea that more megapixels equals smaller pixels equals more noise isn't really working out as engineers are aware of all this. They design new aspects to overcome that likely increase in noise and most seem to be able to get cleaner sensors generation after generation.

Look at smartphones. They often have around 1nm size pixels yet in decent light they produce some pretty nice photos.

But then those sensors have all the latest sensor tech in them.

Greg.

[RickS]

I'm sure that great improvements are being made in reducing read noise and dark noise in new sensors, Greg, probably also big improvements in in-camera noise reduction.

Shot noise is still the fundamental thing that favours big pixels, especially at low light levels.

Cheers,
Rick.

[gregbradley]

In some cases the megapixel count has gone up in Sony CMOS sensors but the pixel size is actually larger.

This is due to CMOS sensors having circuitry surrounding each pixel unlike CCDs. So putting them upside down and thinning them and having the circuitry on the underside saves 40% of space. Also thinner copper wiring
(its typically been aluminium wiring due to reactions in the process)
allows the sensor "stack" (microlenses, pixel light well shaft, cover glass etc) to be thinner allowing more light to be angled in to each pixel.

Other advancements were analogue to digital converters actually on the sensor and not a separate piece of electronics (reduces read noise and why Sony sensors are so good at lifting shadows with no noise). I think there are other tricks to do with a 2nd capacitor with a gate that opens when full well is achieved to increase capacity (and dynamic range) a 2 stage ISO amplification that gives a boost at certain points in the ISO range that increases Dynamic Range at those points. It seems like there is a continual flow of new improvements over the last few years.

For example I read recently that the read noise of my Sony A7r2 42.4mp sensor at one ISO is .8 electrons. No CCD camera matches that. So perhaps CMOS may play a part in future astro cameras?? Are they coming of age?

Greg.

[RickS]

Hi Greg,

I agree that we'll continue to see improvements in sensor technology that will be very welcome. I just wanted to make the point that there are also fundamental limitations that engineering can't fix. Shot noise is one and QE <= 100% is another.

0.8e- read noise is excellent though 1 ISO doesn't seem very useful for astro work :) There are EMCCD cameras with read noise less than 1e- but they are quite expensive.

Cheers,
Rick.

[dannat]

the price seems attractive

[N1]

Hey Joe, great photos of the eclipse!
While I'm not sure either what exactly is going on in the Milky Way image, I do suspect the "linear motion" might be caused by the distortion inherent to the (corrected?) wide angle lens lens rather than the tracking function itself.

Basically, I think the star images that appear to be stretched, may have changed their distance from the lense's optical axis during the exposure more dramatically than the ones that don't appear to be elongated. Unless the camera "ensures" that the rotation is about the celestial pole (and based on the description I don't think it does), this is exactly what I would expect to see in the final image. You've recorded "star trails" showing the journey of the star images towards/away from the optical axis.

What sort of results do you see with low-distortion lenses such as a fixed 50 or a macro?

[gregbradley]

LOL ,I meant one ISO as in one as an impersonal pronoun. I think it was ISO640 or higher.

Greg.

[gregbradley]

I think the price surprised a lot of people. It offers a lot for that price.
Its a lower than a Nikon D810 and has features the Nikon does not. But the D810 is probably near the end of its product cycle and a new Nikon is probably not far away no doubt with a newer more megapixel sensor like the 42.4mp in the Sony A7r2. Unfortunately though that sensor unless Nikon does a better job of implementing it, is not ideal for astro as its got quite a lot of colour noise in the dim areas at high ISO long exposure. Long exposure noise reduction handles it, dark subtract may as well but the previous model didn't have that issue. Its always something eh?

Greg.

[N1]

Also not sure how well it would work for nightscapes (i.e. photos that contain both landscape and sky). How would the sensor compensate for the relative movement between the two?

[Atmos]

The only way to use that feature in nightscapes would be to take two images, one for foreground and another for background.

[OzEclipse]

I don't have any. I agree roughly with your assessment however, I'd describe it as the result of the interaction between the lens distortion and the tracking function. I suspect the sensor can only rotate about its axis. If the centre of the image was pointing at the SCP, it might work. If not it won't. It does the best it can but something in the field won't track properly. I checked my images and I don't think I have any 50mm images taken with the gps. As I stated, I use it as a convenience when traveling. I'll try some 50mm shots when I get a chance.

Thanks for the comments on the eclipse shots. I mostly travel to total eclipses, not a big fan of annulars. However, this one on the horizon was spectacular with all the distortion.

Cheers

Joe

[Regulus]

Pentax don't seem to get the attention they deserve in my opinion. they often build a good camera, and lenses whose optics a very good.
What would be lovely is if you could plug a camera into the mount to and use it as an auto guider as well :-)
Since the sensor is active it should be capable of tracking and adjusting the tracking. Wonder if Canon or Pentax would consider the idea :-)

Trev

[zardos123]

I just preordered my k-1, i have been waiting for this

[zardos123]

next

[zardos123]

the star tracer is a great feature but..........have a look at this http://diglloyd.com/blog/2016/20160218_1331-PentaxK1-SuperResolutionMode.html
this will be the game changer for astro folk i think. I have pre-ordered mine and am keen to intergrate a little data from a modded k-5, in a year or so i will get the k-1 modded. the sensor on the k-1 is a newer gen of the sony in the d810 and sony camera according to a bit of inside info i have been given:eyepop: it is supposed to be an incremental improvement over all that has preceded it. Pentax has shown in the past that with the same sensor(k5,d7000) that they seem to sqeeze more out anyway, so we will see
regards brad

[Regulus]

I'm a bit more than impressed Brad. Thanks for the link.
I almost bought a Pentax but opted for th eos600d because i need the articulated liveview screen. Now this has one plus the rest, it's tempting.
Cheers - Trev