« previous next »
Pages: [1]

Author Topic: what wrong with this picture?  (Read 5998 times)

Offline bcstein12

  • Newcomer
  • Posts: 22
what wrong with this picture?
« on: 2013 October 19 19:54:19 »
Started processing this image for the first time started seeing this background noise.  Anybody have any idea what it is?

nikon d90
ISO 800 36 x 280sec
36 darks 36 bias  no flats
orion 8" astrograph
Logged

Offline pfile

  • PTeam Member
  • PixInsight Jedi Grand Master
  • ********
  • Posts: 4729
Re: what wrong with this picture?
« Reply #1 on: 2013 October 20 09:52:04 »
this can happen when the dark temperatures don't exactly match the light temperatures, and you have enough differential flexure in your system that the hot pixels travel along the subs in lines. you can try more aggressive pixel rejection during integration. check your calibrated lights for the hot pixels.

rob
Logged

Offline MikeOates

  • PixInsight Addict
  • ***
  • Posts: 278
Re: what wrong with this picture?
« Reply #2 on: 2013 October 20 14:43:29 »
This type of pattern can also occur if you don't use dithering (or use too small a dither) when taking the subs, I know it did for me using a DSLR, increasing the pixel dither from 2.5 px to 7 or 8 px worked for me.

Mike
Logged

Offline bcstein12

  • Newcomer
  • Posts: 22
Re: what wrong with this picture?
« Reply #3 on: 2013 October 20 20:10:55 »
thanks for the help!!!!!
Logged

Offline TobiasLindemann

  • PixInsight Addict
  • ***
  • Posts: 126
    • Trackingstation
Re: what wrong with this picture?
« Reply #4 on: 2013 October 23 08:21:53 »
Some month ago I had the same problem. The solution was to make better temperature-matching darks and make more bias-frames. I think 36 bias is not enough. The "signal" in the bias is very poor, so you have to stack much of it. E.g. I use a masterbias consisting of 270 frames.
You may have a look at my thread: http://pixinsight.com/forum/index.php?topic=5583.0 (thanks again to Ruediger and Jan for the help)
Logged

Offline DMouse

  • Newcomer
  • Posts: 49
Re: what wrong with this picture?
« Reply #5 on: 2013 October 24 18:57:41 »
Hi, I have seen this type of noise before and it was caused by low battery, especially when it is cold. Also make sure you don't have your data cables next to your power cables, especially the ac ones.

Hope ya gets it fixed and Clear Skies
Logged

Offline MortenBalling

  • Member
  • *
  • Posts: 74
Re: what wrong with this picture?
« Reply #6 on: 2013 December 03 03:24:54 »
As Rob and Mike said: It's due to "bad" calibration and lack of dithering. Depending on what capture/guiding software you use, you should try to dither the mount between each exposure. I personally use Nebulosity/PHD, and dithering with those two are a walk in the park. Dithering makes a huge improvement, and I highly recommend it. I took me a while to realize, but setup is simple, and I wish I'd done it earlier. I have tons of non dithered data, which are very hard to process.

Cs (not here I'm afraid ;)

Morten
Logged
Pages: [1]
« previous next »