Help. Pollution or something else ? - Forums

Topic starter

Jan 24, 2022

Hello

I just started taking photos in December so extremely new to me. Though I’ve came across a little nag.

im using a skywatcher 200p on an eq5 pro. I use an asiair and a asi120mm mini as a guidescope. My main camera is an unmodded canon 700d.

basically whenever I try to photograph the target I get a white cloud on the image. Upon processing the image is just unusable. White fog all around.

i took nearly 2 hours of lights of m31. All had this white fog which moved over time over the FOV.

i do not know what it could be but it’s ruining all my pictures.

i have attached a few pics from my Asiair. Excuse how small they are. As you can see it moves from the top to bottom of the screen. Even with flats it can’t be used as there seems to be some sort of change during the session.

thanks

andrea tasselli

Frequent contributor

Jan 24, 2022

You should upload a higher resolution image of the frames but, yes, it's light pollution, quite strong as well.

Gernot Schreider

Jan 24, 2022

Do you have street lamps or other artifical light nearby ?
You could have stray light from these sources.

CS
Gernot

Jjmorris90

Topic starter

Jan 24, 2022

andrea tasselli:
You should upload a higher resolution image of the frames but, yes, it's light pollution, quite strong as well.

*** The site says 1MB only ***i

Salvatore Iovene

Admin

IOTD Staff

Frequent contributor

Jan 24, 2022

The site says 1MB only

That's the upload limit for forums, for the Free accounts. But if you upload to your gallery, it's much higher.

Well Written Concise

Jjmorris90

Topic starter

Jan 24, 2022

Gernot Schreider:
Do you have street lamps or other artifical light nearby ?
You could have stray light from these sources.

CS
Gernot

There are LED streetlights yes but not in direct view of the scope. The scope was pointing at the sky.

Jjmorris90

Topic starter

Jan 24, 2022

I have uploaded a photo in my gallery. This is post processing. You can see the awful white bands around the image.

the raw files are in fit format so not sure how to upload those

Jjmorris90

Topic starter

Jan 24, 2022

Or the raw data is available here
https://drive.google.com/drive/folders/1ZL25zd5anVjfuNZapSDhvsKsWZHJMqMA?usp=sharing

andrea tasselli

Frequent contributor

Jan 24, 2022

All I can see is monochrome fits files. No colour information that I can see. Weren't you using a Canon DSLR?

Jjmorris90

Topic starter

Jan 24, 2022

andrea tasselli:
All I can see is monochrome fits files. No colour information that I can see. Weren't you using a Canon DSLR?

Yeh I was - canon 700d via an ASIAIR

andrea tasselli

Frequent contributor

Jan 24, 2022 · Edited: Jan 24, 2022

Something went quite wrong along the way then, because your lights/darks/biases are 16bit monochrome fits files and your flats are standard CR2 files.

Concise

Jjmorris90

Topic starter

Jan 24, 2022

andrea tasselli:
Something went quite wrong along the way then, because your lights/darks/biases are 16bit monochrome fits files and your flats are standard CR2 files.

I was under the impression they remain mono until debayering in post processing ?

andrea tasselli

Frequent contributor

Jan 24, 2022

They are not mono, they are OSC. Here is what your fits files say:

SIMPLE =                    T / file does conform to FITS standard
BITPIX =                   16 / number of bits per data pixel
NAXIS   =                    2 / number of data axes
NAXIS1 =                 5208 / length of data axis 1
NAXIS2 =                 3476 / length of data axis 2
EXTEND =                    T / FITS dataset may contain extensions
COMMENT   FITS (Flexible Image Transport System) format is defined in 'Astronomy
COMMENT   and Astrophysics', volume 376, page 359; bibcode: 2001A&A…376..359H
BZERO   =                32768 / offset data range to that of unsigned short
BSCALE =                    1 / default scaling factor
PROGRAM = 'PixInsight 1.8.8-11' / Software that created this HDU
COMMENT PixInsight Class Library: PCL 2.4.15
COMMENT FITS module version 1.1.9
COLORSPC= 'Grayscale'          / PCL: Color space

Once converted from "supposed" Bayer format into colour they all return equal colour planes. IOW, I can't see any colour at all. I suspect that they were saved as grayscale files originally then converted into FITS.

Helpful Concise

Jjmorris90

Topic starter

Jan 24, 2022

andrea tasselli:
They are not mono, they are OSC. Here is what your fits files say:

SIMPLE =                    T / file does conform to FITS standard
BITPIX =                   16 / number of bits per data pixel
NAXIS   =                    2 / number of data axes
NAXIS1 =                 5208 / length of data axis 1
NAXIS2 =                 3476 / length of data axis 2
EXTEND =                    T / FITS dataset may contain extensions
COMMENT   FITS (Flexible Image Transport System) format is defined in 'Astronomy
COMMENT   and Astrophysics', volume 376, page 359; bibcode: 2001A&A...376..359H
BZERO   =                32768 / offset data range to that of unsigned short
BSCALE =                    1 / default scaling factor
PROGRAM = 'PixInsight 1.8.8-11' / Software that created this HDU
COMMENT PixInsight Class Library: PCL 2.4.15
COMMENT FITS module version 1.1.9
COLORSPC= 'Grayscale'          / PCL: Color space

Once converted from "supposed" Bayer format into colour they all return equal colour planes. IOW, I can't see any colour at all. I suspect that they were saved as grayscale files originally then converted into FITS.

Odd. I get colour when I’ve stacked in siril. Not sure what’s going on.

andrea tasselli

Frequent contributor

Jan 24, 2022

Neither I. It does say Bayer pattern further on in the FITS header. Converted into RGB doesn't bring any joy though as the colour planes are essential identical. I can see the Bayern pattern in the flats' CR2 however.

Jjmorris90

Topic starter

Jan 24, 2022

andrea tasselli:
Neither I. It does say Bayer pattern further on in the FITS header. Converted into RGB doesn't bring any joy though as the colour planes are essential identical. I can see the Bayern pattern in the flats' CR2 however.

Hmmm. Next time Il save the files directly to the camera as opposed to the asiair

Torstein Thomassen

Jan 24, 2022

It looks like you have a light leak, try to cover the primary mirror side of the telescope next time with a jacket, tin foil or something to test it.

Concise

Jjmorris90

Topic starter

Jan 24, 2022

Torstein Thomassen:
It looks like you have a light leak, try to cover the primary mirror side of the telescope next time with a jacket, tin foil or something to test it.

Will do thank you. I know that when I put the dust cover over the lens to take flats light gets in through the bottom

David Moore

Jan 24, 2022

Have you tried a dew shield as you may have reflections off the tube. What happens when the street lights go out if you have them? Have you tried a woolly hat or something around the bottom of the tube? Is light getting in around the focusser somewhere?

Concise

Jjmorris90

Topic starter

Jan 24, 2022

Have you tried a dew shield as you may have reflections off the tube. What happens when the street lights go out if you have them? Have you tried a woolly hat or something around the bottom of the tube? Is light getting in around the focusser somewhere?

I’m going to get a dew shield. I’ve not tried when they go out. Usually at midnight. I will try when the weather permits it.