[Pete Glastonbury]

Hello folks, my first post here.
I have been trying to image Comet C2 Lovejoy using a Pentax K-R and the GPS unit but am getting upward trails.
How can I get it to track properly? I have calibrated it in Astrotracer but all the photos have a slight trail.
Many thanks,
Pete

[mattt]

post photo with EXIF

Most often the exposures are too long. There is another thread on O-GPS that may be of use... especially this post

[jbinpg]

Also, the O-GPS1 seems acutely sensitive to both magnetic fields and metallic objects. So don't use a cell phone around one and don't put a block of iron next to one either.

Jack

[maxxxx]

Long exposures are definitely a problem for mine. Mine also seems to lose CV calibration quickly. When I attempt stacking the first three exposures are good but then I suddenly get trailing.

[Pete_XL]

Hi Pete,
I experimented a lot with o-gps1 the last months. After a lot of frustration concernig trails I now have made my peace with it. Beeing frustrated at first I read a lot about traditional tracking devices for astrophotography. I found that regarding the precision and effort needed in astrophotgraphy to orientate systems along the rotating axis of the earth to avoid trailing with long lenses it is obvious that the precision of the system camera/o-gps1 can not be accurate enough to conquer traditional astrophotography tracking systems..

But, knowing and handling the system reglematations, o-gps1 is a phantastic tool!!! I found that it gives me 10x - 15x the exposure time I would have without it. And that is a lot!!

For example: following the rule: exposure time without trails = 500/(focal length x crop) you would end up with 1.6s exposure time with a 200 mm lense ant a K-5 without a tracking device. O-GPS gives me 15s-25s withe the 200 mm lens, depending on the direction I am pointing to (angular speed varies with position in sky). And that is enough to get all a lot of deep sky objects acurately ont the sensor. With shorter lenses e.g. 50 mm you can pull exp.-time to more than a Minute.

In the attachments you find some examples of Lovejoy 2014, Orion and Andromeda I made this winter.Lovejoy was a challange for me but I got 5 great photos in less than an hour and am excited about the possibilities of the system. Unfortunately picture quality in these small jpgs is very bad.

But as you see in the resulting photos it is better to not extend your exposure time to uncertain sizes is but to live with 10x the 500/f-rule-time, push ISO high, open the apperture to the max and make a series of shots. Then use e. g. the cost free deepskystacker software and stack photos to eliminate noise and pixel-shift.

Picture Near Miss! was 1 shot with K5/O-GPS of 15 seconds at 200 mm F3.5, Iso 1600
The Lovejoy II picture was stacked from 25 K5/O-GPS shots of 15 seconds at F3.5 and ISO 800-1600 at 200 mm focal length. It shows details of the dim comets tail.
Lovejoy III was stacked from 195 shots of 4s with Olympus OM-D and an adapted Pentax A 50 mm at F2.0

Peter

[Aaron28]

nice!