Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
6 Days Ago   #1
New Member




Join Date: Jan 2019
Location: Perdido, Florida
Posts: 10
Star Trails

I was experimenting with the 50mm f1.7 Pentax lens attempting start trails. My settings were as follows:

ASA 200
Shutter set to B
Exposure time 30 minutes
f3.4
Focal length 100

This is what I ended up with, see attached photo. Any idea what may have caused the over exposure effect? Note I did notice the neight had a porch light on, so I backed up into the shadows. Perhaps the long exposure washed it out...Comments please.

Thanks!

Rodney

Attached Images
View Picture EXIF
PENTAX K-r  Photo 
6 Days Ago   #2
Loyal Site Supporter
Loyal Site Supporter




Join Date: May 2007
Location: Flagstaff, Arizona
Posts: 331
I think you are just overexposed.

Also, where was the moon? If your EXIF date is correct, you were shooting tonight, and although the moon is only a few days old, it can still add a moderate amount of light to the night sky.

Try using shorter exposures and stacking them.
6 Days Ago   #3
Pentaxian




Join Date: Dec 2011
Location: Nevada
Photos: Gallery
Posts: 1,941
As you surmised, your image is badly overexposed. If you increase the contrast and decrease the exposure in processing, you might be able to salvage it. The biggest problem with your technique is that according to the EXIF you took the shot at 7:16 pm yesterday (the 11th). At that time the Moon was still above the horizon and about 39% illuminated. That is much too bright for 30 minute exposures. Try doing star trails when the Moon is below the horizon. I'd also advise shorter exposures and then stacking them with one of the freeware stacking programs like Startrails. Go out when the Moon is below the horizon and try six 5 minute exposures at 400 ISO and f5.6 as a starting point.





Aiming toward the poles will make curved star trails. Toward the equator will make straighter star trails. Increasing ISO or wider apertures will give you more and wider trails. Increasing the exposure time lengthens the trails.
5 Days Ago   #4
Pentaxian




Join Date: May 2014
Location: Linz
Photos: Albums
Posts: 619
QuoteOriginally posted by Beachbum Quote
Focal length 100
May I ask why you entered a focal lenght of 100mm (not that it makes any difference for a 30min exposure on a tripod )?

5 Days Ago   #5
New Member




Join Date: Jan 2019
Location: Perdido, Florida
Posts: 10
Original Poster
Just playing around with the settings. I read someplace where it said an increased focal length can reduce the time taking these trails. Default for this camera is 45. I reset it there. My thinking on it was to reduce the time and maybe filter out some of the light pollution.

QuoteOriginally posted by othar Quote
May I ask why you entered a focal lenght of 100mm (not that it makes any difference for a 30min exposure on a tripod )?


---------- Post added 01-12-19 at 09:33 AM ----------

Have not tried the stacking method yet. Is there some software that you would recommend for this that I can download? I have a MacBook...

Thanks,

Rodney


QuoteOriginally posted by AstroDave Quote
I think you are just overexposed.

Also, where was the moon? If your EXIF date is correct, you were shooting tonight, and although the moon is only a few days old, it can still add a moderate amount of light to the night sky.

Try using shorter exposures and stacking them.
5 Days Ago   #6
Pentaxian
photoptimist's Avatar

Join Date: Jul 2016
Photos: Albums
Posts: 2,774
This is most likely the moon or light pollution.

There's a slight chance that some of the fogging is sensor dark current if you had long shutter time noise reduction turned off (note that if you turn it on and take a 30 minute bulb image then the camera will lock-up while it takes a second 30 minute correction image of the dark current).
5 Days Ago   #7
New Member




Join Date: Jan 2019
Location: Perdido, Florida
Posts: 10
Original Poster
Star Trails

I'll most likely have to wait until this moon cycle is over. Probably need to go to a darker site as well. My neighbors have outside lights which the long exposure is picking up. That was my guess. I think i would have had a very nice shot had it not been for this.

Probably I need to do the stacking. I've never done this. Is Photoshop or Paint Shop Pro good for this? or would you recommend another software.? I had one on my Mac last year but deleted it for some reason. Can't remember the name, started with an L.....Linkyeos or something...


QuoteOriginally posted by photoptimist Quote
This is most likely the moon or light pollution.

There's a slight chance that some of the fogging is sensor dark current if you had long shutter time noise reduction turned off (note that if you turn it on and take a 30 minute bulb image then the camera will lock-up while it takes a second 30 minute correction image of the dark current).
5 Days Ago   #8
Pentaxian




Join Date: Dec 2010
Location: Ontario
Photos: Gallery
Posts: 3,023
QuoteOriginally posted by Beachbum Quote
Probably I need to do the stacking. I've never done this. Is Photoshop or Paint Shop Pro good for this? or would you recommend another software.? I had one on my Mac last year but deleted it for some reason. Can't remember the name, started with an L.....Linkyeos or something...
StarStaX is freeware, easy to use, and available for Mac or Windows. Photoshop (elements or the full version) will also work, as should most software that has some version of layers and a "lighten" mode or equivalent for the blending modes.

4 Days Ago   #9
Pentaxian




Join Date: Apr 2007
Location: Sweden
Posts: 2,048
QuoteOriginally posted by Beachbum Quote
Just playing around with the settings. I read someplace where it said an increased focal length can reduce the time taking these trails. Default for this camera is 45. I reset it there. My thinking on it was to reduce the time and maybe filter out some of the light pollution.

Rodney
They probably meant the real focal length as in a longer lens, not just changing the setting.
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!
camera, exposure, light, moon, pentax help, photography, technique, time, trails, troubleshooting
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Star Trails over Australia peggers Monthly Photo Contests 18 09-10-2018 04:31 PM
Star trails experiment chaplain143 Monthly Photo Contests 2 09-09-2018 07:08 AM
Thematic Post & Discuss Your Astro Tracer Star Trails & Star Shots wtlwdwgn Mini-Challenges, Games, and Photo Stories 27 08-28-2018 08:09 PM
Astrotracer star trails *sigh* AlexanderS Troubleshooting and Beginner Help 23 05-08-2018 07:23 AM
Interval Composite Mode for Star Trails? JayRock Troubleshooting and Beginner Help 5 05-26-2017 09:46 AM



All times are GMT -7. The time now is 12:54 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