Advice needed on calibration frames

[Astro Noodles]

Hi

I would welcome some advice about calibration frames. Do these look right to you?

Master Dark - 30x119sec

Master Bias ISO 1600 x 50

Mater Flat ISI1600 x 50

Any comments or suggestions would be welcome.

[vlaiv]

These are from DSLR, right?

I don't have that much experience with DSLR images - but they don't seem right to me.

1. Master dark shows bayer pattern features and dark should not show them as no light should be present. You might have a light leak when taking darks.

2. Bias is just flat black surface. Because it is Jpeg - I can't really tell if it looks good or not. I can't run any statistics on jpeg file

3. Master flat - well looks too flat. In fact it looks exactly the same as master dark for some reason. Master flat should have higher histogram (be brighter) and show some sort of variation across the surface. It should also show distinct bayer pattern (not the case here).

[Astro Noodles]

Thanks Vlav. Yes, a DSLR. Canon 1100d.

Please find attached .Tiff of Bias

MasterOffset_ISO1600.tif

200mm_ISO1600_119s_20deg.tif MasterFlat_ISO1600_200mm.tif

Edited July 29, 2021 by Astro Noodles

[teoria_del_big_bang]

You will get best advise from @vlaiv who has helped countless members with calibration files including myself.
Having looked at them and stretched them in PI I can only agree with vlaiv.

Maybe if you can attach the raw data files it will tell us more.
This is the master Dark stretched and magnified.

Steve

[Astro Noodles]

16 minutes ago, teoria_del_big_bang said:

You will get best advise from @vlaiv who has helped countless members with calibration files including myself.
Having looked at them and stretched them in PI I can only agree with vlaiv.

Maybe if you can attach the raw data files it will tell us more.
This is the master Dark stretched and magnified.

Steve

Thank Steve. I was puzzled as to why a session I did the other night was so noisy. I'm off to take another sequence of darks with the camera zipped inside a bag. 🙂

It was my first go at taking flats, using a light drawing pad. I set the pad to it's lowest light, set the camera to AV and took the flats. Is that the correct method?

[vlaiv]

13 minutes ago, Astro Noodles said:

Thanks Vlav. Yes, a DSLR. Canon 1100d.

Please find attached .Tiff of Bias

Ok, this, to me looks like regular bias with light leak.

Bayer matrix is still visible when I stretch bias sub:

And histogram tells similar story:

Although it is not easy to see - this histogram shows three distinct peaks. Maybe If I outline them, they will be easier to see:

(sorry for my poor drawing skills )

Bias and dark should not have any idea if pixel is blue, green or red - only when light hits that pixel there should be difference based on the fact that there is some sort of filter in front of pixel.

Fact that you have three distinct peaks in histogram means that there is light leak. Dark and bias should have one single nice looking bell curve.

There is a cap for optical viewfinder on DSLR that you should put on when doing bias and darks. Do you put it on?

It is usually located on strap.

Another option is IR leak - but that is likely only on astro modified cameras if you removed IR cut filter and did not replace it.

[Astro Noodles]

That will be it then. No cap over optical viewfinder. A Rookie error. 😄

Many thanks Vlaiv.

[teoria_del_big_bang]

6 minutes ago, Astro Noodles said:

Thank Steve. I was puzzled as to why a session I did the other night was so noisy. I'm off to take another sequence of darks with the camera zipped inside a bag. 🙂

It was my first go at taking flats, using a light drawing pad. I set the pad to it's lowest light, set the camera to AV and took the flats. Is that the correct method?

Been a while since I did anything with a DSLR but yes using AV mode is correct.

And as vlaiv says use the viewfinder cover , I think you can use for all images not just calibration files.

Steve

[teoria_del_big_bang]

Still best to do darks in a dark room as well as the covers, I always do mine in Garage and at night as well.

Steve

[Astro Noodles]

Right, I'm off to take the all again - properly this time, and then to have some fun re-processing.🙂

[Chefgage]

31 minutes ago, Astro Noodles said:

Right, I'm off to take the all again - properly this time, and then to have some fun re-processing.🙂

I take it then you have not altered focus/removed the camera/dismantled the imaging rig since imaging?

[Astro Noodles]

1 minute ago, Chefgage said:

I take it then you have not altered focus/removed the camera/dismantled the imaging rig since imaging?

Yes I have, but I can still re- take darks and bias frames. Fortunately it is 19deg here at the moment which is exactly what it was the other night when I took the images I want to re-process.

[Chefgage]

12 minutes ago, Astro Noodles said:

Yes I have, but I can still re- take darks and bias frames. Fortunately it is 19deg here at the moment which is exactly what it was the other night when I took the images I want to re-process.

Thought I might just ask. I have before wound the focuser in then realised I had not taken my flats!