[Stone G.]

There have been a few recent threads about "Astrotracer Troubles" so, I would like to show some results with my fairly long Tamron Adaptall-2 SP 350mm f/5.6 (Model 06B) lens.

I have only had the O-GPS1 for about 5 weeks by now, but so far, results have been encouraging as this shot at star Vega and surroundings will show:


Pentax K-5 and Tamron Adaptall-2 Model 06B. Stack in Deep Sky Stacker of 3 exposures of 20 seconds at ISO 400
Image contrast enhanced in PhotoImpact. Click on image to see larger version.

Here are 100% crops of the fields indicated:


Alpha Lyra (Vega)


Double Star Epsilon1,2 Lyra


Double star Zeta1,2 Lyra

These test images weren't taken in the best of nights, The almost full Moon was up and there were drifting clouds. Otherwise, I would have boosted both ISO and exposure time. Anyway, I think that starts are neatly round and the double stars, even the rather difficult Zeta Lyra, are clearly split.

And outside the field shown, I even managed to capture this one:


The Ring Nebula, M57 in Lyra. Stack of 5 exposures in DSS. Other details as above.

I mainly bought my O-GPS1 for geotagging but surely, Astrotracer can indeed produce "useful" results too. Don't you think so?

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Last edited by Stone G.; 08-09-2012 at 06:55 AM.

[Ben_Edict]

I mainly bought my O-GPS1 for geotagging but surely, Astrotracer can indeed produce "useful" results too. Don't you think so?

Agreed. After the recent discussions I was quite weary about the O-GPS1. But when I see your ring nebula I am tempted to think more seriously about buying one. It is certainly much easier to carry around, than taking a scope and a mount with me...

Thanks for showing these examples.

Ben

[Quicksand]

Wow, that's really impressive. I'm guessing that's a 100% crop on the Ring Nebula? I may have to pick one of these up.

How hard is it to aim the camera/O-GPS1 at a desired target in the sky with a long lens? If I know the azimuth and altitude, will the interface help me point there -- and is it pretty accurate in doing so?

[Stone G.]

@Ben_Edict: I cannot rule out there there may be cause(s) for being wary, but I haven't really encountered such major problems as others have described. I see three major, potential causes for failure:

1. Hardware flaws: The O-GPS1 seems to be mechanically speaking a fairly robust design, and I would be surprised to find mechanical failure here. But the camera body's sensor actuators could - I don't know - be the culprit in some of the cases reported?

2. Compass accuracy: The accuracy is limited in itself, and one should certainly be observant for local disturbances to Earth's magnetic field. Astrotracer "knows" the magnetic declination overall, but it will be sensitive to very localized disturbances.

3. Potential problem: The focal lenght can only be dialed in for MF lenses (which I use for astro photography) in discrete steps and FL is an important parameter for the firmware to calculate the proper amount of motion. I wish it would be possible to dial in a "continuous" range of FLs in order to possibly fine-tune a given setup.

Anyway, it is natural that people feel more prompted to report problems in search for assitance so, all you you with positive experiences: Let's hear from you. And as Ben_Edict says: When it works, as it does for me, it is indeed a very handy grab-and-go system!

@Quicksand: You are right. All crops shown are 100%, 700 pixels wide. Regarding aiming the camera, it may take some practice, but with long and large lenses it is quite easy to see the brighter stars in the viewfinder. For example, you can fairly easily spot all the stars that form the Lyra. That holds, not only for my bright K-5 but also for my less bright K200D viewfinder. With smaller, wide-field lenses, you can only see the very brigtest stars and you have to point by eyesight off-camera.

Or, you can use a spottingscope as finderscope. I made one from an old 80-200mm Adaptall-2 zoom:



The electronic compass will give you the azimuth right away with a reasonable accuracy unless you have very long focal lengths, but I have found no way to read-out the altitude even though the firmware certainly has that information which is needed for calculating the centre point's declination. An external inclinometer might be part of a solution together with the electronic compass of the O-GPS1. It should surely work for wide-field lenses where you have the worst problems in seeing anything in the viewfinder.

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Last edited by Stone G.; 08-09-2012 at 03:11 PM.

[Ben_Edict]

Thank you Steen for sharing your thoughts!

Ben

[mikeSF]

I initially had issues with comma shaped trails from my O-GPS1, but after updating to the latest firmware, the problem was resolved. In all, i give the device about a B- grade. It seems to suck down batteries fast (i need a new battery for every outing it seems), that bright blue LED is ridiculous in complete darkness, and $200+ is too much, IMO. Besides that, i find the coordinate plotting useful as well as the astrotracer.

[Stone G.]

I initially had issues with comma shaped trails from my O-GPS1, but after updating to the latest firmware, the problem was resolved. In all, i give the device about a B- grade. It seems to suck down batteries fast (i need a new battery for every outing it seems), that bright blue LED is ridiculous in complete darkness, and $200+ is too much, IMO. Besides that, i find the coordinate plotting useful as well as the astrotracer.

Regarding battery consumption: Well, yes and no - the external battery is a benefit (just ask Nikon GPS users). My findings are that the battery life statement in the manual (under specifications) are accurate (about 7 hrs. of continous use).

Regarding blue light: I believe this is a compromise. You will apreciate it, when you use the O-GPS1 for geotagging in broad daylight. At night you may indeed want to extinguish or dim that light by means of some cover. (I use a right-angle finder and don't have that much of a problem here).

Regarding price: Hmm, weil, if you compare witn Nikon and Canon that seems to be level, wherther fair/reasonable or not....

Rgarding your rating: If you only buy the O-GPS1 for Astrotracer, you may be about right - but if you want a good geotagging system and just take Astrotracer as an added benefit, I would rate it higher.

The Astrotracer isn't a real substitute for an equatorial mount, but I still find it convenient as an easily portable "grab-and-go assistant".(Although it does give you grey hairs in the head once in a while).

[Stone G.]

My latest session with 350mm/Astrotracer was one of those where everything that could also did go wrong.

The sky was unusually dark for my current observing site from an urban 4th floor balcony and the air was deceptively clear and seemingly calm. There were lots of stars to bee seen in the viewfinder, but my brain and eyes just wouldn't cooperate to navigate to my target. When I finally got there, I found out that seeing was lousy and I ruined a good deal of shots through improper focus. After re-focusing - and here the liveview at 10X magnification was really helful - I ruined yet a good deal of shots because, meanwhile Astrotracer had changed its mind about the motion of the stars.......

After renewed precise calibration, tracking reults at 350mm weren't really satisfactory in any directions but one:


Globular cluster M13 in Hercules: Combined stacks in DSS of 5 45 second exposures, 10 25 second exposures
and 10 15 seconds exposures. All taken at ISO 1600. Resulting image post-processed in PhotoImpact. Click on
image to see a non-resized 100% crop (1280 pixels wide).

And thus, while my first "real" Astrotracer-M13 image developed before my eyes, I felt that I was after all being rewarded for three hours of labour and frustrations.

[Ben_Edict]

My latest session with 350mm/Astrotracer was one of those where everything that could also did go wrong.

The sky was unusually dark for my current observing site from an urban 4th floor balcony and the air was deceptively clear and seemingly calm. There were lots of stars to bee seen in the viewfinder, but my brain and eyes just wouldn't cooperate to navigate to my target. When I finally got there, I found out that seeing was lousy and I ruined a good deal of shots through improper focus. After re-focusing - and here the liveview at 10X magnification was really helful - I ruined yet a good deal of shots because, meanwhile Astrotracer had changed its mind about the motion of the stars.......

After renewed precise calibration, tracking reults at 350mm weren't really satisfactory in any directions but one:

And thus, while my first "real" Astrotracer-M13 image developed before my eyes, I felt that I was after all being rewarded for three hours of labour and frustrations.

I must say, I am very impressed. I would not expect 350mm FL to work that good with the AstroTracer. Amazing - and thanke for another great image.

Ben

[cheekygeek]

Very nice!

If you do some research on astrophotography with a DSLR, you'll see that good images of Deep Sky Objects (DSOs) require:
a) adequate integration time (meaning the cumulative exposure from stacked individual exposures). For this, darker sites are better than light-polluted sites and faster (quality) lenses are better than slower lenses
b) individual exposure times short enough to avoid skyfog (sometimes also called skyglow)
c) removal of any exposures that have defects (quality images will be made up of stacks of quality individual exposures)

One site I found says that most DSOs require at least 2 to 3 hours of integration time, even at a dark site to come out nicely. Obviously, the more frames you can stack the better.

I just got my O-GPS1 and am very excited to try it once the nearly full moon exits the sky and gives me the opportunity.

[Class A]

How did it go for you, @cheekygeek?

The O-GPS1's astrotracer functionality seems to be a bit of a hit and miss affair.

[stephp]

@Class A:
From my own experience, the ASTROTRACER functionnality works well: Galaxie du Triangle (M33) | PhotosSteph

[Stone G.]

@Class A:
From my own experience, the ASTROTRACER functionnality works well: Galaxie du Triangle (M33) | PhotosSteph

So are my experiences too (Astrotracer Images (1)) - but I am afraid that Class A is right. Others have had less sucess, se for example:

https://www.pentaxforums.com/forums/pentax-camera-field-accessories/234691-st...ls-o-gps1.html

[gleeman]

hello all,

it works well for my K5 with DA*200

here's my setup and experience

(written in traditional chinese)
Pentax O-GPS1(How to)

[Stone G.]

here's my setup and experience

I got the DA* 200mm a few months ago and can confirm that this lens, the O-GPS1 and the K-5 make a terrific trio.


Stack in DSS of 10 exposures of 20 seconds at f/4.0 and ISO 3200

More examples from my (mostly light polluted) skies here: DSLR Astophotography: Astrotracer Images with Petax GPS Unit O-GPS1