An Astropixelprocesser question

[muletopia]

Folks,

I started using NINA fro acquisition, all good for basic sequence use for lights, flats and darks. When I present  these to APP it issues dire warnings about the lack of a master flat. I guess that somewhere the is a command in APP to build he master flat. Where is this command?

Anyway attached is the result produced, only one hour of data, needs more time, Helix nebula NGC 7293.

Chris

combo2.tiff

[tooth_dr]

Do you take dark flats or bias to calibrate the flat?

[geeklee]

8 minutes ago, muletopia said:

I started using NINA fro acquisition, all good for basic sequence use for lights, flats and darks. When I present  these to APP it issues dire warnings about the lack of a master flat. I guess that somewhere the is a command in APP to build he master flat. Where is this command?

As @tooth_dr mentions the Flats would need calibrated if you're throwing everything into APP.

Typically the Master Flat will be (1) a set of Flats and (2) a set of matching Dark Flats or Bias frames.  This will produce a calibrated Master Flat.

The calibrated Master Flat can then be used with a Master Dark and (in APP) a BPM.

While you can absolutely throw all your raw calibration frames into APP, I create the masters then just have them added so its clear to me what's happening in case something goes wrong.  If you do decide to create Masters separately, under the Calibration tab is this button:

[muletopia]

18 hours ago, geeklee said:

As @tooth_dr mentions the Flats would need calibrated if you're throwing everything into APP.

Typically the Master Flat will be (1) a set of Flats and (2) a set of matching Dark Flats or Bias frames.  This will produce a calibrated Master Flat.

The calibrated Master Flat can then be used with a Master Dark and (in APP) a BPM.

While you can absolutely throw all your raw calibration frames into APP, I create the masters then just have them added so its clear to me what's happening in case something goes wrong.  If you do decide to create Masters separately, under the Calibration tab is this button:

OK geeklee, thanks. I read your words but in my ignorance I must ask, how do you make dark flats?

[tooth_dr]

2 hours ago, muletopia said:

OK geeklee, thanks. I read your words but in my ignorance I must ask, how do you make dark flats?

Whatever length your flats are, you then take dark frames (scope covered) the same length of time.

So for example if your flats are 1.35 seconds, then you take a set of darks that are 1.35 seconds long - these are your ‘dark flats’

 

[Clarkey]

Just to add to the comment above, if you use the NINA flat wizard it will do your dark flats too. Just put the right number of subs in the 'Dark Flats' box. Once you have done your flats NINA will tell you to cover the scope.

[muletopia]

3 hours ago, tooth_dr said:

Whatever length your flats are, you then take dark frames (scope covered) the same length of time.

So for example if your flats are 1.35 seconds, then you take a set of darks that are 1.35 seconds long - these are your ‘dark flats’

 

I am still confused. My lights are 180 seconds so I took 180 second darks to match them.

My flats are .001 seconds.

Does this mean that I should take a set of darks of .001 seconds to produce dark flats?

Chris

[tooth_dr]

2 minutes ago, muletopia said:

I am still confused. My lights are 180 seconds so I took 180 second darks to match them.

My flats are .001 seconds.

Does this mean that I should take a set of darks of .001 seconds to produce dark flats?

Chris

Yes that’s exactly it.  However your flats are very short. You may as well just calibrate with a bias frame instead.

My flats vary from 1s to 20s depending on the filter being used. I would recommend you decrease the light source output to make you flats a longer duration.

[rickwayne]

The math for applying flats only works if they're normalized to a reference level from which the processing software can apply the corrections. A frame exactly the same as the flat, but with no light signal, is one way to do this. Another is to establish the absolute base signal from the sensor, with no signal (thermal or otherwise) and scale that. That's done by taking a number of dark frames at the minimum exposure time for which the sensor yields reproducible results, and stacking those to create a master bias frame.

There is a perennially tiring debate about which is better -- flat darks require less extrapolation, bias frames don't have to be reshot every time you change exposure for your flats, tastes great, less filling, you get the idea. Some sensors (e.g. the Panasonic in the ASI 1600 series) do not yield reproducible results from very short exposures, and so bias frames are not an option.

For my 183, even with its famously wacko amp glow, bias frames work fine. I don't argue with anyone who advocates dark flats. They also work fine.

For an example, I use 1/8000" exposures for my DSLR, and 1/1000" on the 183.

Edited December 24, 2022 by rickwayne

[muletopia]

On 24/12/2022 at 20:28, tooth_dr said:

Yes that’s exactly it.  However your flats are very short. You may as well just calibrate with a bias frame instead.

My flats vary from 1s to 20s depending on the filter being used. I would recommend you decrease the light source output to make you flats a longer duration.

Well that was it, I took 20 .001 second flat darks this evening and all complaints about master flat darks went away, so thank you gentlemen. Final image is attached

Chris

[geeklee]

5 hours ago, muletopia said:

Final image is attached

That's great news Chris.  That's come out well and some of the fainter outer  edges just coming through in the periphery of the image.

[AstroMuni]

On 25/12/2022 at 13:23, muletopia said:

Final image is attached

That looks good. What scope do you have that produces the 6 spikes?

[muletopia]

9 hours ago, AstroMuni said:

That looks good. What scope do you have that produces the 6 spikes?

The telescope is a Takahathi Mewlon 250, An older model with 3 spider vanes.. The camera is a QHY8l that has 7.8 micron pixels which suits the telescope.

Chris

[tooth_dr]

1 hour ago, muletopia said:

The telescope is a Takahathi Mewlon

A takahathi you say Chris…is your surname… 😂

Edited December 29, 2022 by tooth_dr

[muletopia]

16 hours ago, AstroMuni said:

That looks good. What scope do you have that produces the 6 spikes?

OK Takahashi Melon 250

[JeremyS]

2 hours ago, muletopia said:

OK Takahashi Melon 250

Cantaloupe or Honeydew?

[muletopia]

3 hours ago, JeremyS said:

Cantaloupe or Honeydew?

If I could type straight Mewlon