RASC Hamilton Pentax Astro Tracer

[David Galbraith]

Thanks Gary,

certainly a consumer dSLR is not going to compete with a dedicated astrophotography camera in many regards - although some great results can be obtained with a dSLR. Your point about the fixation with pixels is well taken. The 24 megapixel Pentax K3 achieves that resolution on an APS-C-sized sensor, too - so the pixels are under 4 microns, which is very small, even for a dSLR. In comparison, Canon EOS REBEL T3i bodies have 18 megapixel sensors that are built of 4.3 micron pixels. The EOS 7D comes in at 6.5 microns (Canon has developed a new full frame sensor with 17 micron pixels). 

Interestingly, there is no anti-aliasing filter on the new Pentax camera; there is anti-aliasing emulation in on-board software that can be turned off. 

cheers,

- David


----------------------------------------
> From: gary at bendun.net
> To: astronomers at hamiltonrasc.ca
> Date: Fri, 29 Nov 2013 21:48:42 -0500
> Subject: Re: RASC Hamilton Pentax Astro Tracer
>
> An interesting concept.
>
> I think you probably know already that 24MP is way too many, but the
> manufacturers are in a race to keep piling more pixels into a small chip.
> Small pixels are going to have a hell of a time collecting already rare
> photons.
>
> Gary Bennett
>
> http://bendun.net/
> http://photos.bendun.net/
>
>
> -----Original Message-----
> From: astronomers [mailto:astronomers-bounces at hamiltonrasc.ca] On Behalf Of
> David Galbraith
> Sent: November-29-13 9:29 PM
> To: astronomers at hamiltonrasc.ca
> Subject: Re: RASC Hamilton Pentax Astro Tracer
>
> Thanks Gary,
>
> It's clearly only going to work for relatively short exposures (max. of
> minutes - then other problems are going to start getting chronic, too, like
> noise from sensor heating during long exposures). What I've read indicates
> that the Astro Tracer system drives sensor motions throughout each exposure,
> attempting to minimize star trailing. The built-in sensor motion system
> (which is how Pentax and also Sony cameras reduce vibration) is three-axis -
> up & down shifts and rotation. Canon and Nikon cameras do not have similar
> systems (IS and VR are systems that move elements within lenses. The
> advantage of moving the sensor is that the system will work with any lens,
> not just one with the extra VR mechanism, motors, etc. built in - and extra
> cost per lens too). Some people who have posted results of trying Astro
> Tracer in on-line reviews report differences in trailing relative to the
> direction pointed.
>
> Astro Tracer appears to be included in several of the Ricoh/Pentax camera
> line. It requires fitting an external GPS unit (Pentax O-GPS1). I haven't
> found an easy listing of which bodies will work this way yet, but the K5-II
> and newer, 24 megapixel K3 certainly do.
>
> cheers,
>
> - David
>
> ----------------------------------------
>> From: gary at bendun.net
>> To: astronomers at hamiltonrasc.ca
>> Date: Fri, 29 Nov 2013 20:39:36 -0500
>> Subject: Re: RASC Hamilton Pentax Astro Tracer
>>
>> I have never heard of this gadget before but I suspect you would
>> achieve a better result with one of these gadgets:
>> http://www.kwtelescope.com/home/vixen-polarie-star-tracker.html
>>
>> I suspect that the Pentax system only shifts the sensor between
>> exposures (not during). That is just a guess on my part. But the Vixen
>> device rotates full-time. The identical unit is now sold under several
> brand names.
>>
>> Gary Bennett
>>
>> http://bendun.net/
>> http://photos.bendun.net/
>>
>>
>> -----Original Message-----
>> From: astronomers [mailto:astronomers-bounces at hamiltonrasc.ca] On
>> Behalf Of David Galbraith
>> Sent: November-29-13 8:23 PM
>> To: astronomers at hamiltonrasc.ca
>> Subject: RASC Hamilton Pentax Astro Tracer
>>
>> Hi,
>>
>> Has anyone experimented with the Pentax Astro Tracer system for
>> tripod-based night sky photos? It looks like it's available for
>> several of their cameras, including the new flagship dSLR the K3. Requires
> a separate GPS unit.
>>
>> From http://www.dpreview.com/news/2011/7/8/pentaxastroreport:
>>
>> "Japanese website DCWatch has published a test of the star tracking
>> feature of Pentax's O-GPS module. The Astro Tracer mode uses the GPS
>> coordinates to calculate the camera's movement relative to the stars,
>> then utilizes the camera's image stabilization system to shift the
>> sensor to track that movement. The report, which is a little tricky to
>> follow in its Google-translated form, includes several example images,
>> showing the system's effectiveness. (From DCWatch)"
>>
>> As noted, the original review from Japan comes through the translation
>> process badly, but here it is:
>>
>> http://translate.googleusercontent.com/translate_c?hl=en&ie=UTF8&prev=
>> _t&rur
>> l=translate.google.com&sl=ja&tl=en&twu=1&u=http://dc.watch.impress.co.
>> jp/doc
>> s/review/special/20110708_458911.html&usg=ALkJrhjnsWtb5a4SAFAl_k0iBlD1
>> mMfMXg
>>
>> cheers,
>>
>> - David
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