[TopherTheME]

So I bit the bullet and bought a O-GPS1 unit with mostly intended use for astrophotography. I was a rather skeptical about how well it would work given the many negative opinions on it especially regarding its Astrotracer function. Now after using it for two nights I can now see that all those negative opinions about the quality and function of this device are complete nonsense. This thing is freaking great! I'll let the pictures speak for themselves but the fact that you can shoot galaxies from a tripod using a very mediocre telephoto is rather incredible. Yes, the device does have its quarks but once you understand how it works and realize how to use it there is no reason you can't get fantastic results. As long as I did a precise calibration every now and then, stayed away from power lines/stations, and kept my phone in my car I got very good repeatable results.

Attached is a picture of M51, the whirlpool galaxy. I shot it with my K-5 piggybacked on my dobsonian telescope using a DA 55-300mm lens wide open at 300mm. The shot consists of 4x45sec and 6x60sec subs @ ISO 3200 stacked using DSS and a little bit of post processing. Also, this was taken in a white zone. I really wish I had some nice glass as the DA 55-300 is rather soft at infinity and has a good amount of vignetting.

Attached Images

 

---

Last edited by TopherTheME; 05-15-2012 at 01:29 PM.

[TopherTheME]

Attached is a cropped image.

[Adam]

Congrats on the purchase, and wow, that's quite impressive, especially considering you used the 55-300mm!

[Bob from Aus]

I love your photos. When you put so much work into getting your photo, nice to see the GPS does the job. I certainly don't have your patience, but I should give it a go.

I have only had mine a short while and I am amazed at just how easy it is to use. There are comments about how costly it is, but my handheld GPS cost a bucket load more and then all the messing about to geotag.

[mtansley]

Very nice photos. Glad you're enjoying it.

I did find that if you're not familiar with the stars and/or astrophotography in general, then you can't get the best out of the astrotracer function.

It is amazing how it does work, it does work much better than I thought it would.

I find that I have a great deal of trouble lining up the camera with the object I want to photograph, also, not knowing the night sky very well doesn't help either.

There is a place on the accessory database on this website to put your review about the device, please do, pointing out what you like about it.

[interested_observer]

The GPS unit is one item that has been on my list and I have been considering getting it. However, the negative comments have so far given me enough reasons to not pull the trigger. These comments and images however have given me pause to go back and reconsider my reluctance. Personally I wanted to get the Milky Way shots, and have never considered the M51. A K5 and the 55-300 along with a good tripod and head (of which I have all), so this appears to me now to be pretty promising.......

[fuent104]

I would love to see a thread of shots taken using the astrotracer function. I find it to be incredible that so much is visible in the night sky, even with wide lenses, when the exposures are long enough.

[Gimbal]

Impressive.

[Stone G.]

So I bit the bullet and bought a O-GPS1 unit with mostly intended use for astrophotography. I was a rather skeptical...... .

Congratualations TopherTheME!

The GPS unit is one item that has been on my list and I have been considering getting it. However, the negative comments have so far given me enough reasons to not pull the trigger. These comments and images however have given me pause to go back and reconsider my reluctance. Personally I wanted to get the Milky Way shots, and have never considered the M51. A K5 and the 55-300 along with a good tripod and head (of which I have all), so this appears to me now to be pretty promising.......

Try to take a look at this thread:

https://www.pentaxforums.com/forums/pentax-k-5-forum/167500-k5-o-gps1-astrophotography-pix-experiences-namibia.html

And myself? I ordered one yesterday.............................

[TopherTheME]

Very nice photos. Glad you're enjoying it.

I did find that if you're not familiar with the stars and/or astrophotography in general, then you can't get the best out of the astrotracer function.

It is amazing how it does work, it does work much better than I thought it would.

I find that I have a great deal of trouble lining up the camera with the object I want to photograph, also, not knowing the night sky very well doesn't help either.

There is a place on the accessory database on this website to put your review about the device, please do, pointing out what you like about it.

I think this may be where I have an advantage over many Pentax users. I've been an amateur astronomer for about a year and half or so now and know the night sky fairly well. I've also done some non-astrotracer astrophotography so I am very familiar with the whole concept of taking pictures of faint moving objects.

Even more important than that though is that I also have a solid background in electronics and electrical engineering. This is a rather big deal in that if you don't know how the thing works you wont know how to get the best results from it. For example, GPS units have a SNR of well under -100dBm, the satellites themselves often more than that. Yet, you still see people trying to test out the astrotracer indoors and wondering why they can't get a signal! Like all commercial GPS units, they need a direct line of sight to the satellites themselves otherwise they just can't work. Also, the astrotracer determines the cameras orientation through a 3-axis fluxgate sensor (electronic compass) and possibly through the use of accelerometers as well (not sure about his part, yet). Accurately measuring earth's magnetic field can be very difficult as its only about 300mG. So things like powerlines, cell phones, and even ferrous materials (like a car) can throw off the sensor.

Anyway...I've attached another picture I took during the first time I tried to use the thing. Its M13, the Hercules Cluster taken with the same lens as the shot above. Its a 45sec exposure I think at ISO 1600. This one has had basically no processing and is a single shot.

[mtansley]

I think this may be where I have an advantage over many Pentax users. I've been an amateur astronomer for about a year and half or so now and know the night sky fairly well. I've also done some non-astrotracer astrophotography so I am very familiar with the whole concept of taking pictures of faint moving objects.

Even more important than that though is that I also have a solid background in electronics and electrical engineering. This is a rather big deal in that if you don't know how the thing works you wont know how to get the best results from it. For example, GPS units have a SNR of well under -100dBm, the satellites themselves often more than that. Yet, you still see people trying to test out the astrotracer indoors and wondering why they can't get a signal! Like all commercial GPS units, they need a direct line of sight to the satellites themselves otherwise they just can't work. Also, the astrotracer determines the cameras orientation through a 3-axis fluxgate sensor (electronic compass) and possibly through the use of accelerometers as well (not sure about his part, yet). Accurately measuring earth's magnetic field can be very difficult as its only about 300mG. So things like powerlines, cell phones, and even ferrous materials (like a car) can throw off the sensor.

Anyway...I've attached another picture I took during the first time I tried to use the thing. Its M13, the Hercules Cluster taken with the same lens as the shot above. Its a 45sec exposure I think at ISO 1600. This one has had basically no processing and is a single shot.

Thanks for the info, that is very interesting about the background to these GPS devices.

I know that in my review I covered myself by saying that I am not an astrophotographer and that those who are will get much better images out of the device than I will.

I ended setting up a red dot finder next to the camera so I could adjust both to sight on a planet (Venus or Jupiter) or a bright star that I could see through the camera viewfinder (amazing how dim viewfinders are for looking at stars!!). I could then use the red dot finder to sight on what I was trying to see. Still very difficult though unless as you do, you know the sky very well.

I figured the O-GPS1 would have a fluxgate compass as well as using the GPS to calculate info. What is it actually doing when you rotate it? I know about fluxgates but don't know much about them if you see what I mean.

[derekkite]

TopherTheME: great shot. 400mm? What lens?

[TopherTheME]

mtansley, I'm actually not quite sure what is happening during the calibration procedure but I would assume that the camera is more or less "finding ground" or determining the orientation that is normal to the earths surface. Earth's magnetic field changes by location and time of day so I would imagine that some type of calibration is required to determine the orientation between the earths magnetic and gravitational fields, probably using the camera's accelerometers. But again, I didn't design the camera and haven't ripped mine apart yet so I don't really know.




derekkite, that shot was taken with my Orion ST80 I think (have to check image data) which yes, is 400mm. I don't think my DA 55-300 is capable of producing pinpoint stars like that. Also the ST80 has far more field curvature which is evdient in that shot.

[mtansley]

mtansley, I'm actually not quite sure what is happening during the calibration procedure but I would assume that the camera is more or less "finding ground" or determining the orientation that is normal to the earths surface. Earth's magnetic field changes by location and time of day so I would imagine that some type of calibration is required to determine the orientation between the earths magnetic and gravitational fields, probably using the camera's accelerometers. But again, I didn't design the camera and haven't ripped mine apart yet so I don't really know.

Interesting graphic, thanks.

I remember from flying training about magnetic north moving around and having to calculate heading. The maps always had a date and indicated the magnetic north adjustment so you could calculate how much extra or less magnetic adjustment you needed.

That little GPS unit is actually doing quite a bit in the background. Makes it quite impressive.

[TopherTheME]

I tried M51 against last night except this time with my ST80. I had a really hard time with star trails this time, I'm guessing because I'm using a telescope instead of a lens. I took about 20 frames, only about 7 of them ended up being usable.


7x45sec ISO 3200 F5.6 Orion ST80 400mm