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11-18-2011, 01:04 AM   #16
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QuoteOriginally posted by KansasHorizons.com Quote
I think there is some serious compass issues. I went outside just to see if the N S offset was a given and the E W wouldn't even line up..
My compass wouldn't even turn 360 degrees the first time I used it, but after a couple of "normal" calibrations it now work ok, a couple of degrees off at most. (when level)

So unless you mess up the normal calibration (turning with uneven speed, or to quick, or to slow) it does sound like a faulty device.

11-27-2011, 12:27 AM   #17
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I finally managed to get a few night of clear skies after getting my replacement GPS unit. The compass seemed to be a little more accurate than the last but it is still a bit random. I managed to get some great tracking with the 50mm lens to the NNW but when switching around to the NE even with re-calibration it failed to track. Overhead it failed to track, pointed North it failed to track. If I switched to the 90mm Tamron or the 135mm manual lens it wouldn't track though it had been with my 50mm. The 18-135 mm wouldn't track either.

I gave up on the item as rubbish but on the way home I went East of town to shoot the Orion Nebula. I was able to get good tracking to the East now but not NW again with the 50mm. If I switched to the 90mm Tamron or an old 135mm Manual it wasn't tracking again. For giggles I put on the 500mm Bigma and with 50 seconds of tracking it did pretty good. Back to the 90mm and the 135 mm for more failures. Through this all I re-calibrated with regular and precise calibration over and over.

The simple fact is that this item can get a few good tracks out of hundreds and that is about the size of it. Switching lenses, directions or anything else seems to cause tracking errors that calibrations aimed at any direction cannot cure. Battery life with new alkalines was 2-3 hours max before the light was blinking on both units. Tracking on even the working lenses started to fail after 2:30 to 3 minutes.

I have quick built single arm barn door trackers that I can rough align the hinges with the pole star and get better results while manually turning the knob and rough counting the seconds as I turn it than I get out of this item 99% of the time.

If you are satisfied with GPS only or are willing to spend hours upon hours trying to get lucky with the astrotracer function of this unit then buy away. If you expect some form of consistency you better leave this at the vendor. I think numerous nights with two separate tracers was enough for me. I had such high hopes for this item but I am back to the plans to build another double arm barn door tracker, Aluminum this time.

I think my results must be quite common because with thousands of units out there you find only a small handful of pictures that look good, and they were stacked.
11-27-2011, 02:08 AM   #18
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One thing you might want to check up (which I just discovered myself) is that the ball-head I use on my tripod seems to be slightly magnetic. After having a hard time calibrating the compass to be correct the whole 360 degrees around. I removed the camera and put on a normal compass on the top of the ball-head and then watched the needle while turning 360 degrees. Sure enough, the compass wandered back and forth +-10 degrees at certain headings.

As for stacking, it will always improve the signal to noise ratio no matter how professional equipment you use. So even if the o-gps1 was perfect, you should still stack the result.

Last edited by Gimbal; 11-27-2011 at 02:13 AM.
11-27-2011, 02:52 AM   #19
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QuoteOriginally posted by Gimbal Quote
One thing you might want to check up (which I just discovered myself) is that the ball-head I use on my tripod seems to be slightly magnetic. After having a hard time calibrating the compass to be correct the whole 360 degrees around. I removed the camera and put on a normal compass on the top of the ball-head and then watched the needle while turning 360 degrees. Sure enough, the compass wandered back and forth +-10 degrees at certain headings.

As for stacking, it will always improve the signal to noise ratio no matter how professional equipment you use. So even if the o-gps1 was perfect, you should still stack the result.
I have tried two different tripods and the compass still plays games with me alone holding it though again the second was far better than the first. Stacking would certainly help but at what cost? What chance will there be the unit will ever get enough non trailing images to stack? And even forbid the thought of getting it to work in the direction that I want it to that day. You can get random shots that work but with a whole lot of failed effort.

This was the shot with the Sigma 500mm. The wind was picking up a bit so in this case I know I had wobble very apparent in Jet capture and some trail due to the wind. The geosynchronous satellites show how much trail would have been there otherwise.



Again the big problem is there is nothing consistent about the unit except that it is consistently inconsistent. I will probably play a bit more and hope I can work something out but if the results don't improve it is back to Amazon before I am stuck with it.

11-30-2011, 01:23 PM   #20
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After the last few nights I give up. These things are junk and or my camera is. The only direction I can get anything close is at Andromeda and the opposite direction at near the same height when I hit the Orion Nebula. Anything anywhere else cannot be hit with any success.

Last night added a new problem of a dead GPS unit when I arrived at yet another distant shooting area. I tried numerous new batteries and was gonna go back home when a good tap on the unit brought it too life.

I have re-calibrated regular and precise calibrations dozens of times in slow and fast motions, I have done it with 180's in one and both directions and full 360's in one and both directions. It will alter the compass readings a bit but still fails.

I have changed locations by 10 to 15 miles in case someone had buried a giant magnetic UFO under where I was shooting or the nuclear plant 10 miles away was affecting me. I have tried various tripods, lenses, chants, standing on my head etc to get this to work.

I have tried it with and without the battery grip, different batteries in the camera and the unit. In the unit I had no choice because it eats them in under 2 hours.

I have tried various lengths of time and while shorter is obviously better it still doesn't work.

Last night I could not get the usually working 50mm to track at all until again aiming at the Andromeda Galaxy. I then switched to the 500mm and it still worked:



Until I switched it a bit South to the Triangulum galaxy:



And don't ask what that banding is because it happens every time I use the 500mm with this thing and I have no idea.

It was perfectly still on a hard packed road and no earthquakes ongoing. Using remote and mirror lockups etc.

Now one strange note that makes me suspect the camera SR is part of the problem. I shot this last night as well with the 50mm so this is a 100% crop of Praesepe i think it was:



I took the camera off the tripod to give up and decided to rotate it in a manner to force the SR to rattle to all corners and sides of its travel area and put it back on and got this:



Though I could never repeat it again while trying to figure out if it was the camera.

I am at a loss with the remaining possibility that the camera and gps unit are both quality control nightmares. Even if it is the camera the failure to even start the gps unit last night without repeated love taps tells me it has issues as well.
11-30-2011, 07:48 PM   #21
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I hesitate to write this because I have only a limited use of the unit doing astrophotos. In my uses if I put the camera on the tripod and set it to astrotracer raised the camera in elevation then moved in azimuth I seemed to have problems getting a good track. If I set the unit to astrotracer moved my azimuth then raised to my elevation I seamed to get better results. The weather has not been any good to see if I can replicate these results. If this is the case it would make sense to me. The unit probably uses a fluxgate compass. As the fluxgate gets farther from level it can't tell the magnetic direction as well and it needs this to determine how to move the SR system to track the sky. If it can start with a good azimuth first this may help. I am not going to get any good weather to test this were I live for a long time so I will not be able to test this my self.


As for your other problem of getting it to work I haven’t seen any thing like that with my unit.


DAZ
12-01-2011, 01:29 AM   #22
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Well it is possible but for last nights and many other nights runs I was starting at the horizon or close because there is a comet there. So That hasn't helped me. I have purposely set it level then raised it as well with no luck. At this point both units are on the way back to Amazon and I called Pentax and will be sending the camera in for repairs. I already had mirror flop and a ton of dead pixels since day one that some wont map out so I guess I am going to have Christmas without the camera as it seems to be taking so long to get them returned. Either I managed a bad batch of GPS units or my camera is messed or both. Supposedly they will test it with a gps unit there?

QuoteOriginally posted by DAZ Quote
I hesitate to write this because I have only a limited use of the unit doing astrophotos. In my uses if I put the camera on the tripod and set it to astrotracer raised the camera in elevation then moved in azimuth I seemed to have problems getting a good track. If I set the unit to astrotracer moved my azimuth then raised to my elevation I seamed to get better results. The weather has not been any good to see if I can replicate these results. If this is the case it would make sense to me. The unit probably uses a fluxgate compass. As the fluxgate gets farther from level it can't tell the magnetic direction as well and it needs this to determine how to move the SR system to track the sky. If it can start with a good azimuth first this may help. I am not going to get any good weather to test this were I live for a long time so I will not be able to test this my self.


As for your other problem of getting it to work I haven’t seen any thing like that with my unit.


DAZ


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