Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
08-14-2015, 01:06 PM   #16
Pentaxian
Na Horuk's Avatar

Join Date: Feb 2012
Location: Slovenia, probably
Photos: Gallery | Albums
Posts: 11,183
One more thing I would suggest is to work on focus. You should use MF. Best is you learn where true infinity focus is on your lens in good daylight, then mark it (maybe with some masking tape, the kind that won't leave residue). That way you can easily find the best focus when you are out in the dark. And finally, I would suggest you stop down the lens a little bit, even if just 1/3 or 1/2 aperture.

08-14-2015, 01:15 PM   #17
Pentaxian
aurele's Avatar

Join Date: Jan 2011
Location: Paris, France
Photos: Albums
Posts: 3,187
to me it looks like you hav manually focus your 35mm f2.4 until the focus ring hit the end. And it mean, it ain't focus on anything ! The DA 35/2.4 don't have a hard stop at infinity. Turn the focus ring then go back for a milimetre or two and you'll be focus on infinity. Otherwise you'll focus beyond.
08-14-2015, 03:44 PM   #18
Loyal Site Supporter
Loyal Site Supporter




Join Date: Jun 2009
Location: Tumbleweed, Arizona
Photos: Gallery | Albums
Posts: 5,425
The posts on focusing - especially with the newer lenses, is an excellent point. My older manual wider lenses are a real joy to use. The newer lenses with their ability to slew by infinity in order to let the camera not bang in to a hard limit, makes focusing a lot more difficult. The last time I was out, I missed focus and blew the entire evening's worth of work - and I should have known.

08-15-2015, 12:55 PM - 1 Like   #19
Pentaxian




Join Date: Dec 2011
Location: Nevada
Photos: Gallery
Posts: 2,011
QuoteOriginally posted by realitarian Quote
Here's one I took on Wednesday on the K-3....
The second image doesn't show trailing but it is out of focus. Try using live view to focus on the moon some night to determine infinity focus for each lens. Reduce the lens aperture a couple of clicks to sharpen up a little more. The longer exposures possible with the Astrotracer will compensate for the loss of light. Your first image shows some trailing as well as out of focus. Because of that difference, I wonder if the problem is camera shake. Bumping the tripod or the camera on a weak tripod in a wind gust, etc could cause what appears to be star trails. Any camera movement will defeat the Astrotracer.

08-15-2015, 07:45 PM   #20
Loyal Site Supporter
Loyal Site Supporter




Join Date: Jun 2014
Location: Los Angeles, CA (San Gabriel Valley region)
Photos: Albums
Posts: 208
Original Poster
Wow, lot of super informative tips. Thanks guys and gals! I'll give it a shot at the next dark sky opportunity. I have a 28mm f3.5 manual lens, will give that a shot after figuring out its sharpest infinity. I have been using a carbon fiber travel tripod, next time I'll take the alt-az mount that is a good 18 lbs.

After that once I am sure everything is figured out with the camera I'll hook up the camera to my f/12 Mak-Cass telescope (probably can't get more than a few seconds exposure on that, but should be interesting).

Last edited by realitarian; 08-15-2015 at 09:26 PM.
08-15-2015, 08:05 PM - 2 Likes   #21
Pentaxian
Digitalis's Avatar

Join Date: Mar 2009
Location: Adelaide.
Posts: 9,534
QuoteOriginally posted by Na Horuk Quote
One more thing I would suggest is to work on focus. You should use MF.
I agree, AF systems on DSLRs aren't designed for or capable of accurately focusing on night sky objects.

QuoteOriginally posted by Na Horuk Quote
Best is you learn where true infinity focus is on your lens in good daylight
This should be done with Live view if possible, the true infinity focus point will sometimes be drastically different from what is marked on the lens.

With this setup:



I was able to get this by pointing my camera straight up:


Pentax K5IIs - Sigma 18-35mm f/1.8 @ f/1.8 18mm, Pentax O-GPS - 30s ISO 800 - no bias frames or DFS used.

With the above image I used magnified live view and I focused on the brightest stars in the central portion of the image.

Last edited by Digitalis; 08-16-2015 at 07:30 PM.
08-17-2015, 09:09 AM   #22
New Member




Join Date: Aug 2015
Location: Grenada
Photos: Albums
Posts: 10
Am a new & beginner of using K3II & this was my tryout last night... with a DA 55-300mm HD lens at F4, ISO 1600, 30s Exposure using a flu card tethered to my iPhone


08-17-2015, 09:28 AM   #23
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 15,199
Am I wrong in assuming that a bunch of stacked pictures are better than a single long exposure? Does the tracker support that as well?

08-17-2015, 09:53 PM   #24
Pentaxian
Digitalis's Avatar

Join Date: Mar 2009
Location: Adelaide.
Posts: 9,534
QuoteOriginally posted by UncleVanya Quote
Am I wrong in assuming that a bunch of stacked pictures are better than a single long exposure? Does the tracker support that as well?
Doing that through astro stacking software is superior to using in-camera processing. The tracker does support taking multiple frames, however you have to shift the camera to compensate for the motion of the sky.
08-18-2015, 06:04 AM   #25
Loyal Site Supporter
Loyal Site Supporter




Join Date: Jun 2014
Location: Los Angeles, CA (San Gabriel Valley region)
Photos: Albums
Posts: 208
Original Poster
QuoteOriginally posted by Digitalis Quote
Doing that through astro stacking software is superior to using in-camera processing. The tracker does support taking multiple frames, however you have to shift the camera to compensate for the motion of the sky.
Just to clarify, you should be able to take several 20-sec exposures within a 5 minutes or whatever time span than the astrotracer function recommends, right?

You could of course go longer with a motorized equatorial mount, but not having that, the astrotracer should work for compensating for movement along the ecliptic and taking multiple exposures for a short time for stacking, no?
08-18-2015, 06:59 PM   #26
Pentaxian
Aaron28's Avatar

Join Date: Jan 2015
Location: Huntsville, Al
Posts: 1,200
QuoteOriginally posted by UncleVanya Quote
Does the tracker support that as well
no on board intervalometer in astrotracer function.....


QuoteOriginally posted by realitarian Quote
take several 20-sec exposures within a 5 minutes

yes as many as ya like to stack
no need for the astrotracer with a motorized mount and yes that's my chase if I knew how to blend images together outside of a stacking program for good foreground composition
08-18-2015, 07:28 PM - 2 Likes   #27
Loyal Site Supporter
Loyal Site Supporter




Join Date: Jun 2009
Location: Tumbleweed, Arizona
Photos: Gallery | Albums
Posts: 5,425
QuoteOriginally posted by realitarian Quote
Just to clarify, you should be able to take several 20-sec exposures within a 5 minutes or whatever time span than the astrotracer function recommends, right?

You could of course go longer with a motorized equatorial mount, but not having that, the astrotracer should work for compensating for movement along the ecliptic and taking multiple exposures for a short time for stacking, no?
I can help shed a bit of light on the topic. You should be able to take any number of images with or without the GPS unit of whatever duration and use a utility like DeepSkyStacker to stack them up. The stacking utility will register and align each image against all the others (and count the number of stars in each frame), so the resulting image will essentially be the common area across your stack (or you can take the combination of all the frames).Using the GPS unit will enable you to gather more light while you are tracking. If you have a static landscape object in the frame it will just smear. Not using the GPS unit will be just like what everyone else will be doing. The big advantage I can see is that with the GPS unit you should be able to capture say 30 to 60 second images, while everyone else will be trying to capture 15 to 20 second images.

Professional astronomers take exactly the same approach. Their telescopes are tracking and guided, and they usually take a series of images (well it depends on the specific instrument that is mounted for the session, the type of data that they are collecting and exactly what they are trying to accomplish). A lot of the images you see are taken with nitrogen cooled CCD imaging arrays over the course of several hours up to an entire night in duration. But, they stack their take across several sessions (nights) together in order to aggregate the light.

QuoteOriginally posted by realitarian Quote
Just to clarify, you should be able to take several 20-sec exposures within a 5 minutes or whatever time span than the astrotracer function recommends, right?
Also, just to clarify, it's not several 20 second exposures within a 5 minute "window", each exposure starts a new tracking period that can be up to 5 minutes in duration (depending on the focal length of the lens).

08-19-2015, 05:25 AM   #28
Loyal Site Supporter
Loyal Site Supporter




Join Date: Jun 2014
Location: Los Angeles, CA (San Gabriel Valley region)
Photos: Albums
Posts: 208
Original Poster
Very cool! Thank you.
08-19-2015, 06:10 AM - 1 Like   #29
Loyal Site Supporter
Loyal Site Supporter




Join Date: Jun 2009
Location: Tumbleweed, Arizona
Photos: Gallery | Albums
Posts: 5,425
Here is a paper that presents stacking images - without tracking.
09-21-2015, 06:21 AM   #30
Junior Member
sindbad1's Avatar

Join Date: Jun 2010
Location: Germany
Posts: 45
Hi, I'm looking for a table with maximum tracking/expoure times for the astrotracer in pentax K-3 oder K-3 II. I couldn't find it on ricoh's website. Does anyone have a link?

Tom
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!
alignment, calibration, camera, cameras, exposure, focus, foreground, images, k-3, latitude, length, lens, mount, nr, photography, scope, secs, shutter, sr, stars, thanks, time, tripod
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Firmware Update - What am I doing wrong? Liney Troubleshooting and Beginner Help 20 03-07-2014 06:08 AM
K-01 Focus peaking what am I doing wrong Banskojoe Troubleshooting and Beginner Help 17 12-08-2013 07:58 AM
Landscape Starstax: What am I doing wrong? Sage97 Photo Critique 4 10-29-2013 08:18 PM
What am I doing wrong? File size is unreal! haycyn Video and Pentax HDSLRs 5 09-13-2013 08:05 AM
What am I doing wrong with new K-30 lenorehig Troubleshooting and Beginner Help 10 08-20-2013 09:34 PM



All times are GMT -7. The time now is 09:46 AM. | 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