#1  
Old 28-06-2013, 04:42 AM
TanjaC (Tanja)
Registered User

TanjaC is offline
 
Join Date: May 2012
Location: Johannesburg, South Africa
Posts: 30
Linear and Non-Linear in PixInsight

Hi guys. I've just switched to using PixInsight. As I'm working through a few tutorials I notice that my data seems to be non-linear already straight after stacking.
My image acquisition was done via Nebulosity as FITS files. I took completely unedited FITS files and did the calibration, star alignment and integration in Pixinsight. (one FITS is 107mb)

Resulting stack looks great, but it looks non-linear. When I open the histogram it already appears to have some stretching. I also don't actually have to use the STF (screen transfer function) to make my targets visible - it's there as if it's non-linear? So now I am unsure if processes like colour calibration actually works, or deconvolution.

Both stacks in PI and Nebulosity looks identical btw.
Could there be a problem in my acquisition?

Help appreciated. Thanks
Reply With Quote
  #2  
Old 28-06-2013, 08:35 AM
alocky's Avatar
alocky (Andrew lockwood)
PI popular people's front

alocky is offline
 
Join Date: Aug 2010
Location: perth australia
Posts: 1,287
The problem is the fits file. Pixinsight cannot interpret the header that Nebulosity writes, so it re-scales the image. I discovered this when I used Nebulosity to drive my CCD and wondered why the calibration data made the images worse. You can work around the issue by converting the fits to tiffs in Nebulosity.
Cheers,
Andrew.
Reply With Quote
  #3  
Old 28-06-2013, 04:18 PM
TanjaC (Tanja)
Registered User

TanjaC is offline
 
Join Date: May 2012
Location: Johannesburg, South Africa
Posts: 30
Quote:
Originally Posted by alocky View Post
You can work around the issue by converting the fits to tiffs in Nebulosity.
Dammit. Thanks a lot for the help. I'll do the conversion to see if it helps. But that means I'll have to find something else for image acquisition on my Mac....

Cheers
Reply With Quote
  #4  
Old 28-06-2013, 04:28 PM
alocky's Avatar
alocky (Andrew lockwood)
PI popular people's front

alocky is offline
 
Join Date: Aug 2010
Location: perth australia
Posts: 1,287
Converting everything to tiff saved one imaging session - pixinsight handled the tiffs fine. You can set the exposure length and iso and all the important fits keywords when you import to pixinsight.
I switched to sequence generator pro and have not looked back - but sadly does not seem to be available for Mac OS.
Good luck!
Andrew
Reply With Quote
Reply

Bookmarks

Tags
pixinsight

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 12:30 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Celestron Australia
Advertisement
Lunatico Astronomical
Advertisement
SkyWatcher Australia
Advertisement
Meade Australia
Advertisement
OzScopes Authorised Dealer
Advertisement
NexDome Observatories
Advertisement
Astronomy and Electronics Centre
Advertisement