Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
11-22-2013, 07:22 PM   #1
Site Supporter
Site Supporter




Join Date: Jun 2013
Location: Montreal, Canada
Photos: Gallery | Albums
Posts: 552
Astrotracer first impressions - blind spot near zenith?

Greetings

Just got my new O-GPS-1 and tried it on comet Lovejoy two mornings ago. The moon was almost full so it was not the best of nights for astrophotos. Here's the best picture I could manage. It is a very short stack of 2 20s exposures.





I used my old pentax-A 135 f/2.8. That little gps is nothing short of great! 25 years ago I strained my eyes guiding manually my K-1000 for 10 min using Tri-X film. Now all I have to do is calibrate, aim and press the button!

Some pictures I took showed lots of trailing though. Lovejoy was very high in the sky near the zenith and only one 60s shot turned out ok (and, of course a huge satellite went right through the comet!). For what I can see tracking precision depends on the unit correctly determining the true azimuth (so the unit can correctly know which way the stars are moving). On the best shots gps azimuth was within 1 degree from true azimuth as determined by comparing stars in the picture with star maps from a planetarium program. On the trailled shots gps azimuth could be off by as much as 6 degrees. Shots taken around 50 degrees of altitude or less were almost always sharp. So there seems to be a blind spot for the astrotracer near the zenith, probably 65 degrees and up. Has anyone experienced this? I know it wasn't a problem with satellites since in all shots, good and bad, the gps had locked on 11 satellites.

Anyhow, this unit just won a place in my photo bag. These days I do most of my sky watching when camping and the price and size of the gps is just perfect compared to an equatorial mount or even an ioptron skytracker.

Best regard

11-22-2013, 08:17 PM   #2
Site Supporter
Site Supporter
jimr-pdx's Avatar

Join Date: May 2010
Location: 1hr north of PDX
Photos: Gallery | Albums
Posts: 3,821
Very nice shot and good report; thanks! I too recall the old days of shooting, using my barn-door mount & slowly turning a screw for two minutes while Hyakutake flew by. I went mad at two minutes, couldn't contemplate going longer

Interesting about high-latitude sky shots, I will watch for replies on that one - and some day soon a GPS1 will fit in my bag too!
11-22-2013, 09:07 PM   #3
Site Supporter
Site Supporter




Join Date: Mar 2008
Location: Prince George, BC
Photos: Gallery | Albums
Posts: 3,305
Greetings from the other side of the country. I haven't really found a weakness with the O-GPS1 at the zenith. But it seems to struggle a bit the closer you get to the celestial pole. I imagine this is because that even though the angular velocity is minimal compared to at the celestial equator, there is more rotation at the poles that it has to compensate for. You just have to up the ISO, shorten the exposures, and increase the number of exposures in the stack to compensate.

Jack
11-22-2013, 09:44 PM   #4
Pentaxian




Join Date: Jan 2011
Location: New York
Posts: 4,763
My experience with the O-GPS1 has shown random errors. Overall, I'm content with it, but if I take multiple shots at the same angle some will track well and some will track poorly.

11-23-2013, 04:12 AM   #5
Otis Memorial Pentaxian
RobG's Avatar

Join Date: Dec 2009
Location: Canberra
Photos: Gallery | Albums
Posts: 7,579
The behaviour of the astrotracer program does seem variable, but just to ask - did you do the fine calibration? Anyway, I imagine that the astrotacer would work better when it was moving the sensor prety much vertically or horizontally rather than rotating it?

PS Interesting comet pic! I don't think I've seen colour in a comet before.

Last edited by RobG; 11-23-2013 at 04:28 AM.
11-23-2013, 06:28 AM   #6
Site Supporter
Site Supporter




Join Date: Jan 2008
Location: SE Michigan USA
Photos: Gallery | Albums
Posts: 1,272
QuoteOriginally posted by SunValley Quote
Just got my new O-GPS-1 and tried it on comet Lovejoy two mornings ago.
WOW !

Keep'um comin'... Very impressed...

Cheers...
11-23-2013, 07:00 AM   #7
Site Supporter
Site Supporter




Join Date: Jun 2013
Location: Montreal, Canada
Photos: Gallery | Albums
Posts: 552
Original Poster
Thanks everyone for your replies.
I did a fine calibration when I turned the unit on. Would it help to recalibrate once in a while? I was also curious about the color and apparently it comes from carbon atoms which have a strong emission line in the green part of the spectrum. I'm glad to read that I'm not the only one with trails on some pics and not on others. From what I gather from your posts there will always be a random part in the precision ot the tracking. But since the gps is so easy to use I don't mind that much.

Thanks again!

11-23-2013, 01:35 PM   #8
Site Supporter
Site Supporter
jimr-pdx's Avatar

Join Date: May 2010
Location: 1hr north of PDX
Photos: Gallery | Albums
Posts: 3,821
QuoteOriginally posted by SunValley Quote
... From what I gather from your posts there will always be a random part in the precision ot the tracking. But since the gps is so easy to use I don't mind that much.
Thanks again!
Good point, if one in ten isn't ideal that's eight more than I'd usually get!
11-24-2013, 09:28 AM   #9
New Member




Join Date: Jun 2012
Posts: 5
QuoteOriginally posted by jimr-pdx Quote
Very nice shot and good report; thanks! I too recall the old days of shooting, using my barn-door mount & slowly turning a screw for two minutes while Hyakutake flew by. I went mad at two minutes, couldn't contemplate going longer

Interesting about high-latitude sky shots, I will watch for replies on that one - and some day soon a GPS1 will fit in my bag too!
Know what you mean. I could go for a minute, maybe two tops with my hand drive tracker based on a bike wheel. Then I decided to build a motorised barn door - you can see it and some photos here http://www.bencooper.karoo.net/AstronomyMountsBarn.html
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
azimuth, degrees, gps, impressions blind spot, lovejoy, shots, spot, tripod, unit
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Misc First Attempts using AstroTracer aant Post Your Photos! 3 07-24-2013 03:40 AM
My first dslr, first impressions and in need of a couple of advices carlosodze Pentax K-30 & K-50 6 07-03-2013 07:24 PM
K30 First Impressions godwinaustin Pentax K-30 & K-50 31 02-19-2013 08:07 PM
K-01 first impressions robert Pentax K-01 25 11-17-2012 01:26 PM
First impressions K5IIs David&karen Pentax K-5 & K-5 II 14 11-10-2012 12:10 PM



All times are GMT -7. The time now is 04:52 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top