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02-15-2012, 12:29 AM   #46
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I gave the orion nebula another go, this time at iso80. Unfortunately a thin cloud layer appeared and kind of ruined it. I also tried another way of converting the DNG to TIFF before stacking this time, using dcraw and settings that did as little processing as possible of the raw data. Result was a little less sharp image, more noise, a couple of dead pixels, but also more colors in the shadows. Notice also that the burnt out area in the center is smaller due to using iso 80 instead of 1600.

so 8 pictures, a 30sec, iso80, 135mm, 100% crop.



02-15-2012, 08:36 PM   #47
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Its all your fault

I made the mistake of starting to read this thread and off I went into Internet search for hours. The moon has always had a fascination for me but then I realized, you could just point your camera at an "empty" sky and discover. I live in a heavily wooded neighborhood so even with bare oaks, there aren't a lot of tree free holes to the sky. Found a small one in the backyard with a fairly clear sky. This is a fixed tripod shot. After a couple of nights reading, I know I'm not going to invest the time and money for my own Horse Head Nebula shot but it does enhance re-reading Cosmos.
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02-18-2012, 05:51 PM   #48
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Well I've sent mine back. I just wasn't happy with how the unit functioned with regards to the calibration method(s) also the results in usage were disappointing for me. I will probably get an GEM mounted scope and work on astrographs from that standpoint.

I will say that the concept of this unit is an excellent idea and I hope that Pentax will sort out the calibration issue as well as provide a more detailed usage manual.
02-18-2012, 07:00 PM   #49
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What calibration problem are you are having that Pentax has to fix. All you are doing is moving the camera in it's three axis through the earths magnetic field at the location your are located. It should then calculate the the three angles of deviation from the earths axis that your camera pointing in the heavens while it is set on your tripod using also the input from the GPS unit. It should then move the camera's sensor at a Sideral time rate for 1/2 of a degree in the right direction to co-inside with the movment of the earth with respect to the stars your are trying to photograph. A one minute exposure is desirable with a max on 2-3 minutes depending on the direction the camera is pointing in the sky. Unless you have a very good GEM ($$$) you would be lucky or well skilled to get more than 5 minutes subs with many shot to stack with a stacking software. Then beauty of the astro tracer is it is small and portable can be easily set up at a walk in dark sky area.
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02-18-2012, 08:17 PM   #50
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I have found that the O-GPS1 works fine with the unit's given max exposure times with focal lengths of 200m and less. But above that I get trailing with anything over about 15-30 seconds regardless of the given exposure time and declinations of 60 degrees and less. In short, a stellar (forgive the pun) unit for wide field work but possibly not so much for narrow field subjects. I still try the longer focal lengths regardless. Anything close to Polaris is fine for all exposure times

Jack
02-18-2012, 10:08 PM   #51
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QuoteOriginally posted by oneeyedhawk Quote
What calibration problem are you are having that Pentax has to fix. All you are doing is moving the camera in it's three axis through the earths magnetic field at the location your are located. It should then calculate the the three angles of deviation from the earths axis that your camera pointing in the heavens while it is set on your tripod using also the input from the GPS unit. It should then move the camera's sensor at a Sideral time rate for 1/2 of a degree in the right direction to co-inside with the movment of the earth with respect to the stars your are trying to photograph. A one minute exposure is desirable with a max on 2-3 minutes depending on the direction the camera is pointing in the sky. Unless you have a very good GEM ($$$) you would be lucky or well skilled to get more than 5 minutes subs with many shot to stack with a stacking software. Then beauty of the astro tracer is it is small and portable can be easily set up at a walk in dark sky area.
Hank
E/W alignment v. N/S. It will not calibrate along the N/S axis and, the cal process is often 'mysterious' (see above comments from the OP) probably relating to this issue. I also noted earlier that the tri-axial calibration method in the standard setup indicates completion after only 2 axial rotations. When I did figure out the E/W issue I still was left with trailing stars (200mm lens @ 30 sec exposure, well below the maximum allotted for the focal length).

QuoteOriginally posted by jbinpg Quote
I have found that the O-GPS1 works fine with the unit's given max exposure times with focal lengths of 200m and less. But above that I get trailing with anything over about 15-30 seconds regardless of the given exposure time and declinations of 60 degrees and less. In short, a stellar (forgive the pun) unit for wide field work but possibly not so much for narrow field subjects. I still try the longer focal lengths regardless. Anything close to Polaris is fine for all exposure times

Jack
^This

Regarding the trad method of astrophotgraphy, I'm well aware of what's in store regarding mount costs and expectations of results. The point I'm making is, that within the typical framework I can learn to a better degree the art and craft and have more control over the inputs even at the beginning level. The O-GPS1 seems to have too great a 'mystery' regarding it's setup and use at this point and I sense too much lies within 'the box' for me to get a better grasp or at least to trust implicitly. The GEM route is well documented and there is plenty of literature to hold my hand as I learn as well as being completely extensible to all comers.

In the end I was probably asking too much of the device and its concept, and after taking the plunge figured out that if I want to continue with astrophotography, I'll need to start with the basics and go from there.
02-22-2012, 06:00 AM   #52
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I got O-GPS unit yesterday and I went to test it quickly. There is couple things I learned. One is that I noticed growing hate towards airplanes..



Another thing is that frozen sea isn't the most steady ground and wind might also cause vibration.

So I need to lower my tripod and find a better place. Maybe I should also check how good the calibration is with normal compass.
02-23-2012, 05:29 AM   #53
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QuoteOriginally posted by ErZi Quote
I got O-GPS unit yesterday and I went to test it quickly. There is couple things I learned. One is that I noticed growing hate towards airplanes..
Another thing is that frozen sea isn't the most steady ground and wind might also cause vibration.
So I need to lower my tripod and find a better place. Maybe I should also check how good the calibration is with normal compass.
When shooting stars the ONE thing you will begin to disapprove is summer with short nights, especially high up north ;-)
Looking forward to seeing more of your pictures.

Cheers from Berlin,

jephi!

02-24-2012, 04:02 AM   #54
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The Twins

We had a couple of hours of clear skies the other night so I took the old Tak 135/2.8 out to do some wide-field work with the O-GPS1. Ended up getting 7 frames of Castor (top) and Pollux in Gemini of which DeepSkyStacker used 5 frames. Exposure was 10 seconds per frame at f/4 and ISO3200. ISO3200 works the best for me since it brings out the fainter stars. DSS counted 125497 separate stars in this frame. We can't see all of those. The original 16 bit tiff is more impressive than this knocked down jpg.
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02-24-2012, 07:36 AM   #55
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As a complete newbie to this astrophotography stuff (I do have an O-GPS1 unit on my K-5) I have a question about this photo stacking stuff.

Basically, you just take x number of photos one after the other with the same settings? Or do you adjust anything? Even with the GPS Astrotracker, I would presume that between each shot the star field would have moved slightly (well, actually, WE'VE moved but you know what I mean) but you leave the camera where it is and let the stacking software deal with the slight adjustment needed.

Do you also need to put in a lens cap on shot to get a copy of the noise levels? Does this need to be done and the beginning AND end of the sequence?

For some assistance I've attached a couple of not great photos I've taken with the O-GPS1 unit and would appreciate any comments about how to improve them. There is a LOT of learning to this astrophotography topic and I feel I'm on a crash learning course.

I am presuming that the blur in the second is caused by camera movement probably due to a not too sturdy tripod or perhaps over exposure as well. Both these were single images.

Thanks for any help.
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02-24-2012, 08:22 AM   #56
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QuoteOriginally posted by mtansley Quote
Basically, you just take x number of photos one after the other with the same settings? Or do you adjust anything? Even with the GPS Astrotracker, I would presume that between each shot the star field would have moved slightly (well, actually, WE'VE moved but you know what I mean) but you leave the camera where it is and let the stacking software deal with the slight adjustment needed.
Right, same settings, no adjustments between shoots (unless you need to re-frame now and then.)

You can do a number of "dark" frames (lens cap on) but it is not necessary, I haven't done it yet personally.
02-24-2012, 10:47 AM   #57
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Software such as DeepSkyStacker can adjust up to a certain number of pixels to keep everything aligned. I find that I can get maybe 5 in a row off and then I will reframe to keep the subject in the middle. I agree with Gimbal - the K-5 has such low dark noise that a dark frame is not necessary.
02-26-2012, 12:11 AM   #58
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DeepSkyStacker works very very well for stacking images of stars and deep sky objects. Below is a picture of the Orion Nebula I took with my K-5. Its 5, 15 sec exposures at ISO 3200 in some very light polluted skies. No dark frames used or required (k-5 sensor has zero hot pixels at -10*C). The shot attached was taken using an Orion EQ-1 mount.

I'm thinking about getting the GPS unit as an equatorial mount is a real pain to setup correctly. Usually takes about 15 minutes to set up plus lots of correction periodically though the night. How long does the O-GPS take to setup assuming everything goes well?

BTW, the k-5 is the first camera I've ever used that actually works in the cold covered in frost and snow. All other cameras I've owned began to freeze up and stop working about 30 minutes into astrophoto sessions in the winter time. Anyone know if the O-GPS is cold proof as well?
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02-26-2012, 02:25 AM   #59
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The o-gps1 is a bit unreliable as it sometimes work just great and sometimes it seems impossible to get a god result. But when it works it takes about a minute to calibrate and you can start shooting. But then perhaps 10 minutes later the result degrades and it can be next to impossible to get a god result again. That is the strange part and I haven't figured out why this is happening. But then after a number of calibrations (but still with bad results) all of a sudden all is good again and I can continue shooting.

I have used the o-gps down to -8 or so for about an hour and a half. The only thing failing was the cheap alkaline battery for the gps, I now use a quality rechargeable battery and the unit is running a lot longer with that.

I was out last night and captured about 20 frames a 30 sec of the Orion nebula at 135mm. I've done a quick stacking test and the results are promising. This will probably be my best astro shoot so far.

Last edited by Gimbal; 02-26-2012 at 02:31 AM.
02-26-2012, 11:44 AM   #60
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I have used the O-GPS1 down to about -20C with no problems. But the single battery in the unit doesn't last long at those temperatures. Clear skies tonight with a fresh batch of Arctic air to play in so will let you know how it goes.

Jack
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