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02-28-2016, 05:27 PM   #91
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Astrophotography encompasses several disciplines that require different approaches. Those doing deep sky photos of faint nebula and galaxies require large scopes with autoguided tracking and long exposures of 5-10 mintues per frame. Those doing comet hunting or planetary work require shorter exposures. And the latest rage of wide field landscape astrophotography even shorter exposures. The shorter the exposure, the greater the chance of pixel shift tech being a benefit to the result. But so far as mentioned, Pentax has not unlocked the various shooting modes to allow something as simple as mirror lockup for the duration of an interval sequence. Most likely this is because of the power needed to keep the mirror up. But many interval shooters are using external power sources so this is not a concern. There certainly are some firmware upgrades that could help astro people do their thing.

02-12-2017, 07:11 AM   #92
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Astrotracer issue

Good people of Pentax forum, I need your help.
I'm playing with Astrotracer for a while, and I don't know if this is a normal behavior, or I have a broken camera, or it's an magnetic anomaly follows me.

Look at the image. (full sizes are here: Yandex.Disk)
1. 30 seconds in manual mode, astrotracer disabled. Distinct star trails (upper left to bottom right, about 40 degrees angle).
2. 30 seconds, GPS and Astrotracer enabled, precise calibration made twice. Trails are much shorter, but their direction is different (bottom left to upper right, something like 30 degrees)
3. 3 minutes 10 seconds (maximum astrotracer suggest). HUGE TRAILS in a direction different from the one without Astrotracer.

If I understand it correctly, Astrotracer moves sensor in a slightly wrong way, causing huge trails to happen.

Of course, for a 20-30" time Astrotracer is better than nothing, but it still inacurate in a pretty bad way. Can anyone confirm this behavior? Should I go for Ricoh service? Too bad I have just 1 month left before warranty runs off. And the nearest service provider is in Shanghai, which means they won't be able to check Astrotracer in field (light pollution is too bad).

Or maybe I did something wrong?

K3II, firmware 1.10. This was shot with Tamron 70-300, but camera shows the same effect with any lens installed. I'm outside (not in house), did calibration at the very same spot a minute before the shooting several times in a row, it always says "Complete" (no error messages whatsoever).
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Last edited by wtigga; 02-13-2017 at 05:27 AM. Reason: upd info on location&calibration
02-13-2017, 07:31 AM   #93
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Are these pictures 100% crop in the center ?
02-13-2017, 07:41 AM   #94
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QuoteOriginally posted by CarlJF Quote
Are these pictures 100% crop in the center ?
Nope, but there's full scale jpgs in the link above, you can check them out.

02-13-2017, 05:30 PM   #95
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There's obviously something wrong since you should get good results for 30 seconds at 100mm. The astrotracer can sometime be erratic, but it's the exception, not the rule... The maximum time given by the astrotracer is often optimistic, nothing to lose for trying, but it's not unusual to have some trailing when pushingthe system to its limit.

I know that this isn't of much help to you, but I don't know why you get star trailing in shot #2 since it's a very usual condition to use the astrotracer. The only thing I can think of is a calibration problem, but you've already done it multiple time. Just to be sure, the calibration was the one in the Astrotracer menu and not the one in the GPS menu ? I'm just asking because, in the past, I mistakenly used the wrong calibration and got star trail. But I don't have a K3ii and don't know for sure if these two calibrations possibilities are there in its menus.
02-13-2017, 06:14 PM   #96
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QuoteOriginally posted by CarlJF Quote
There's obviously something wrong since you should get good results for 30 seconds at 100mm. The astrotracer can sometime be erratic, but it's the exception, not the rule... The maximum time given by the astrotracer is often optimistic, nothing to lose for trying, but it's not unusual to have some trailing when pushingthe system to its limit.

I know that this isn't of much help to you, but I don't know why you get star trailing in shot #2 since it's a very usual condition to use the astrotracer. The only thing I can think of is a calibration problem, but you've already done it multiple time. Just to be sure, the calibration was the one in the Astrotracer menu and not the one in the GPS menu ? I'm just asking because, in the past, I mistakenly used the wrong calibration and got star trail. But I don't have a K3ii and don't know for sure if these two calibrations possibilities are there in its menus.
Yeah, I don't expect much from the maximum limit, but these trails are just enormous, and obviously the sensor moves in a wrong direction. And yes, I did the precise calibration in astrotracer menu. The thing is, I don't know how to contact official Ricoh/Pentax to clarify this issue: the nearest service center located in Shanghai ignoring my emails, submit form on the Ricoh US are simply broken, and their twitter/Facebook account is silent as well. I could imagine how hard it would be to check Astrotracer function for a service center in a huge city...

upd: Facebook reply was "We don't care about customers outside of North America". :-/ Maybe someone could suggest an email address to report hardware/software problem with my camera?

Last edited by wtigga; 02-13-2017 at 06:36 PM. Reason: facebook reply
02-16-2017, 09:09 AM   #97
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So I finally received an answer from my local service center, saying:
"We studied your pictures and we think the issue is too long exposure. Please study manual of K3II and Astrotracer feature and try to operate accordingly. If you still have the same issue, please send it for repair". (my poor translation from Chinese).

First of all, I looked through the manual and never found any specific restrictions or warnings about exposure time, only the limitations set by the camera. I also went to Pentax website to see their samples of Astrotracer feature. According to their sample pictures, Astrotracer can deal with exposure up to 300 seconds without a sight of trails:


I went outside today and made a second series of shots with 70mm Tamron lens and 21mm Pentax lens, away from any metal constructions, and did basic and advanced calibration three times.
As you can see from the attached pics, I have significant trails at 120s on both lenses. So I'm going to send it to the service center and see what's their opinion on that.

If anyone can confirm this kind of behavior for K3II / K1, please reply, I will be very grateful.

(link for full size pics)
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Last edited by wtigga; 02-16-2017 at 09:10 AM. Reason: full size link
02-16-2017, 09:28 AM   #98
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These pictures look about like I would expect for these focal lengths. The maximum time indicated by the astrotracer is really just based on the physical movement allowed by the sensor. It doesn't mean it's the practical limit to get the best results.

I don't have a K3ii or K1, but based on my experience with the O-GPS1 module I'm happy to get a 3-stops improvement over the 1/500 rule. Anything beyond that is bonus but shouldn't be taken for sure. So, with a 21mm lens, I would expect good results up to 120s and, with the 70mm, up to 40 sec. Which is about what is observed in your last serie of pictures. It doesn't mean it's not possible to go beyond that under optimal conditions, just that it's not a sure shot.

02-16-2017, 09:35 AM   #99
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QuoteOriginally posted by CarlJF Quote
TI don't have a K3ii or K1, but based on my experience with the O-GPS1 module I'm happy to get a 3-stops improvement over the 1/500 rule. Anything beyond that is bonus but shouldn't be taken for sure. So, with a 21mm lens, I would expect good results up to 120s and, with the 70mm, up to 40 sec. Which is about what is observed in your last serie of pictures. It doesn't mean it's not possible to go beyond that under optimal conditions, just that it's not a sure shot.
But do you also see movement compensation in a wrong direction? I mean, on my pics sensor is clearly moving, but not quite the right way.
02-16-2017, 09:48 AM   #100
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QuoteOriginally posted by wtigga Quote
But do you also see movement compensation in a wrong direction? I mean, on my pics sensor is clearly moving, but not quite the right way.
Yes, when going for too long the trails often go in unexpected directions.

When working with astrotracer, what I usulay do is first taking a few pictures at about 3-stops over the 1/500 rule. After that, I take some "sure ones" at 2-stops. And only then I'm taking my chances to go for longer exposures, sometime it works, sometime doesn't. This way I usually end up with some workable pictures, better than I would have got without the astrotracer.

Last edited by CarlJF; 02-16-2017 at 09:54 AM.
02-16-2017, 06:43 PM   #101
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QuoteOriginally posted by CarlJF Quote
Yes, when going for too long the trails often go in unexpected directions.

When working with astrotracer, what I usulay do is first taking a few pictures at about 3-stops over the 1/500 rule. After that, I take some "sure ones" at 2-stops. And only then I'm taking my chances to go for longer exposures, sometime it works, sometime doesn't. This way I usually end up with some workable pictures, better than I would have got without the astrotracer.
Anyhow, I measured angles of star trails and matrix shift, and there is 5-6 difference for both lenses. If only it shift sensor in the right direction, it could compensate trails completely.
I will contact service center further and see what's their decision on it.
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02-23-2017, 06:51 PM   #102
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Updates
Good thing is, service guys admits the issue and did "adjustments" to the sensor.
Bad thing is, no clear sky to test it.

Updates 2
Ok, dunno what they did in the service center, but now it's not 5 but 20 difference between the star movement and the sensor compensation. Can anyone here try to do the same kind of test? (two long exposure shots with and without astrotracer)
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Last edited by wtigga; 02-25-2017 at 06:58 AM.
03-06-2017, 06:23 PM   #103
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Ok, so my problem is solved.
1. You do have to get away from big constructions and electronic devices: switch off your phone, wifi sd card in the camera, etc.
2. Calibrate with the tripod. Yes, attach the tripod and rotate camera with it.

Results are fascinating: on 21mm, I got 300 seconds exposure with practically no trails. On 70mm it was 180 seconds (sample). For 300mm, I only got 10 seconds without trails, but it's still 7 times more than I could do with "500 rule".
Can't wait to get out of the city to shoot a really dark sky!


QuoteOriginally posted by CarlJF Quote
Yes, when going for too long the trails often go in unexpected directions.
When working with astrotracer, what I usulay do is first taking a few pictures at about 3-stops over the 1/500 rule. After that, I take some "sure ones" at 2-stops. And only then I'm taking my chances to go for longer exposures, sometime it works, sometime doesn't. This way I usually end up with some workable pictures, better than I would have got without the astrotracer.
So I guess in your case it's either hardware problem, or you have magnetic fields nearby that fails the calibration, because mine goes much further than just 2-3 stops with no trails.

Last edited by wtigga; 03-06-2017 at 10:47 PM.
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