Is this blooming on a STL11000M?

Discussion in 'Legacy Models (ST, STL, etc.)' started by Jarrod Koh, May 4, 2020.

  1. Jarrod Koh

    Jarrod Koh Standard User

    May 4, 2020

    I have been noticing comet tail artefacts in my images from 300 seconds. Could this be blooming?

    I am a novice at this..

    My mount is a Paramount ME
    Imaging camera: STL11000M with a CFW8 filter wheel- a 3rd hand camera now!
    Scope: Tak FSQ106 with a nightcrawler rotator/focuser
    External guide scope: ZWO 30F4 with a starlight Xpress X2- 14 arcsec/px

    Windows 7; TheSkyX 10.5.0; Maxim 6.11;

    I have included links to 60, 180, 300 and 600 exposures. (Baader Ha Filter)

    Many thanks for your advise.


    Jarrod Koh
  2. Colin Haig

    Colin Haig Staff Member

    Oct 27, 2014
    Blooming typically looks like this:

    The star will elongate up the columns, and spill a bit onto neighbouring pixels.
    The pixel values will be mostly 65535 on a 16-bit camera like that one.
    The KAI-11000 CCD sensor has anti-blooming gates to reduce blooming by draining away excess charge caused by too many photons.
    It won't cure all blooming, but helps.

    Some things you might want to check:
    - Tilt on the camera - there seems to be a bit of a collimation isse and some tilt on the camera. This probably means you have some droop in where the camera attaches to the back of the scope, eg in the focuser or however you have attached them.
    It's in the vertical axis.
    Stars aren't that tight in the 600 second image, so you need to consider improving the focus, the guiding and the polar alignment.
    It's decent, but you should be getting a bit better; this takes practice and a few iterations.

    As a tip, in MaxIm, you haven't set up the coordinates of your observing location.
    File... Settings... Site and Optics.
    You probably should also note the telescope in the FITS Header tab, Observer, etc.

    And who is Tan Yong Liang?
  3. Doug

    Doug Staff Member

    Sep 25, 2014
    I think it is actually a small amount of blooming.

    The anti-blooming characteristics of these sensors is a compromise between well depth and anti-blooming. If you increase the substrate voltage you will get more well depth, but it will compromise the antiblooming. Kodak recommended a substrate voltage setting for each individual sensor, which aimed for protection up to 100X saturation.

    Your bright stars were already saturated hard with flat tops on the 60 second exposure. On the 600 second exposure there are nearly 50 saturated pixels. It's possible that you've managed to exceed the 100X factor with the long exposures.
  4. Jarrod Koh

    Jarrod Koh Standard User

    May 4, 2020
    Thank you for that Doug and Colin. I will need to nail the basics first I think!

Share This Page