ccd and lrgb imaging starting from the beginning help needed

[iwols]

right guys after a few misspent hours last night trying to image with a new ccd mono camera and lrgb filters,ive decided to start from the very beginning again,going to use 5x1 minute l,r,g,b images(i know i need more data for a better image) what else do i need ?darks, flats ,bias?? as you can see i mean the very begining ,using an 414ex ccd on a ed80 on a heq5 pro mount polar aligned but not guiding yet

[Uplooker]

Yes to all of the above. I would also advise that you take all you subs for each filter in turn i.e. if you plan on taking 10 off subs - do 10 Lum, 10 Red, Green, 10 Blue. You may not get all in one night but you need to refocus for each filter.

[geordie85]

I would definitely take some flats. I've heard the 414 doesn't need darks but I'm not sure. If it has set point cooling then you can always build a dark library during the day and cloudy nights. You shouldn't need bias if using darks as the same data is in both

[johnrt]

Most don't take darks on the very clean Sony chips, like in the Atik 414ex, so worry about those later. You will need bias - they are not temp dependent, expose for the shortest time possible on the camera with no light allowed to reach the chip.

You will also need flats - point the OTA at an even illuminated surface and ensure the camera orientation and focus point is unchanged from the lights, then aim for around 22/23k ADU (look at the histogram if your using Artemis Capture).

Shoot as many as you can of each, the more the better, I aim for min of 100 bias and 50 flats.

[iwols]

9 minutes ago, johnrt said:

Most don't take darks on the very clean Sony chips, like in the Atik 414ex, so worry about those later. You will need bias - they are not temp dependent, expose for the shortest time possible on the camera with no light allowed to reach the chip.

You will also need flats - point the OTA at an even illuminated surface and ensure the camera orientation and focus point is unchanged from the lights, then aim for around 22/23k ADU (look at the histogram if your using Artemis Capture).

Shoot as many as you can of each, the more the better, I aim for min of 100 bias and 50 flats.

 

[iwols]

You will also need flats - point the OTA at an even illuminated surface and ensure the camera orientation and focus point is unchanged from the lights, then aim for around 22/23k ADU (look at the histogram if your using Artemis Capture). ??? never taken flats before can you expand a little please john...cheers

[Uplooker]

Use a light panel such as this for taking your flats

https://www.amazon.co.uk/Huion®-Tracing-Inches-Adjustable-L4S/dp/B00J3NRAV2

Flats are subs that are taken to mitigate the effect of vignetting. As John says aim for an exposure length so the ADU value is around the 20,000 mark.

You need to take the same number of subs as you did for your Lights I.e. Lum, Red, Green, Blue and or Ha.

I use APT, your capture software should have an option to generate Flats where it will work out the correct exposure for a given ADU value.

HTH

[Astrosurf]

I really don't know how much colour data you'll get for just one-min subs. I have to push the processing with just a few 8-min subs. I also bin my colour subs 2x2 as that's more sensitive and the colour data doesn't need to have perfect detail. The images will be half the size of the luminance so you'll need to resize the TIFF accurately to the pixel.

What capture software do you use? I use Artemis Capture.

I have filters from a set that are parfocal so I don't need to focus each time. They seem to work fine. What make are yours?

Alexxx

[MattJenko]

Don't bother with darks for now. Bias and flats (I simply point at a white monitor screen for my 414 and filters. They not only compensate for vignetting (you won't get much of that with the little 414 chip), but more importantly cater for the dust motes/bunnies on the images.

If you are only shooting that few subs for 60 secs, then choose targets which can be done RGB only, like open clusters. This should get you up and running and practising and don't require L to begin with. Getting stars right is harder than it sounds, but is great practice for all targets later on.

[johnrt]

43 minutes ago, iwols said:

You will also need flats - point the OTA at an even illuminated surface and ensure the camera orientation and focus point is unchanged from the lights, then aim for around 22/23k ADU (look at the histogram if your using Artemis Capture). ??? never taken flats before can you expand a little please john...cheers

 

Flats are to compensate for uneven illumination and calibrate out any dust particles on the camera window, filters or optics. They need to be around 22/23k ADU, if your using Artemis the white and black point is on the histogram in the top left corner.

Find a even surface, (I sometimes use an iPad screen) or point at the sky with a white T Shirt stretched over the front of the scope, and find the right exposure time to roughly saturate the chip on your camera 1/3rd (histogram peak 1/3rd in from the left or 22/23k ADU).

As you are calibrating out physical particles of dust etc, the camera needs to have the exact same orientation to the OTA as when you shot the lights, or the dust particles will not match up, likewise for the focus point, focus changes will make them either a little smaller or bigger.

They are fairly easy to make, with a little practise.

Here is the current Luminance flat from my 6" RC, some will suggest taking flats for each filter, but I just make 1 from the luminance and use it for all (I am lazy) - RGB, experiment and see what works best for you.

This has been stretched heavily to show the dust and uneven corners, they look plain and grey straight out the camera.

 

[iwols]

then aim for around 22/23k ADU (look at the histogram if your using Artemis Capture). ??? never taken flats before can you expand a little please john...cheers i am using artemis at the minute is this the best for capturing or is there something else while im starting out agai n

[MattJenko]

The exposure for flats should be about 1/3 saturation, so for a 65k bit depth camera, that equates to about 22k ADU (units).

[carastro]

To be honest, you really need to sort guiding out, you're not going to get anywhere without that.  By all means have a little practice with your camera and filters, but the advantage of a Mono CCD camera is to be able to take long exposures with cooling.

Flats are the most essential calibration frames you need to take.  If you don't do anything else you must take flats.  Darks as stated can be done any old time and can be saved in a darks library, same length same temperature.  Bias can also be done (shortest sub possible with the camera and also saved in a Bias library.  

Flats will need doing every time unless you leave your camera permanently on the scope.  

Carole 

[johnrt]

9 hours ago, iwols said:

then aim for around 22/23k ADU (look at the histogram if your using Artemis Capture). ??? never taken flats before can you expand a little please john...cheers i am using artemis at the minute is this the best for capturing or is there something else while im starting out agai n

Open the display window in Artemis, and take an exposure. You will see a black point and a white point value in that window. The white point gives you your max ADU count. Experiment with different lengths of exposure until you find one that gives you a white point value of around 22/23k ADU. Easy!

[iwols]

1 hour ago, carastro said:

To be honest, you really need to sort guiding out, you're not going to get anywhere without that.  By all means have a little practice with your camera and filters, but the advantage of a Mono CCD camera is to be able to take long exposures with cooling.

Flats are the most essential calibration frames you need to take.  If you don't do anything else you must take flats.  Darks as stated can be done any old time and can be saved in a darks library, same length same temperature.  Bias can also be done (shortest sub possible with the camera and also saved in a Bias library.  

Flats will need doing every time unless you leave your camera permanently on the scope.  

Carole 

thanks ,did have a go on my ed80 with the qhy5ii mono on my finder scope without much joy would i be better using a different scope for guiding?

[carastro]

I use a QHY5 (the older version) and the Skywatcher finderscope for guiding and it works really well.  I wonder why yours is not working very well.  What was the problem, maybe there is something in your settings in PHD you need to adjust? 

I see you are also using Artemis which I also use, it is very user friendly.  

Taking flats with Artemis, you can see a little box at the bottom of the screen, if you run your cursor over the image (or flat) you will see the numbers change rapidly.  With a flat you need an evenly illuminated (not too bright) light - use typing paper or a white cloth (I sometimes use a folded pillow case) to even out the light, some use a white T shirt, and keep looping (without saving) until you get a reading (in that little box at the bottom) of around 23,000 - 25,000 and this will be fine for your flats.  If its too high or 64,000 you are too bright, so you need more layers of paper or white material.  If it's below 23,000 you need to increase the light or remove a layer of white paper.  OR, lengthen or shorten the exposure. 

Once you have the right reading (ADU) tick the save box (don't forget to name your files as flats).  I normally do around 15.  

I used to use an EL panel but this went wrong, so now I just wait until the next day and use day light (dimmed down).  However it is imperative not to move your camera or focus between taking of images and flats or the dust bunnies will not line up. Not every-one has the luxury of doing their flats the following day, but saves having to do it when you're dog tired in the early hours and just want to get to bed. 

WARNING: You can sometimes get light leak if you do your flats during the day, so I always wrap up my camera and FW with a black cloth.  

 Even if your camera is new you will get some dust, and there is always the Vignetting that needs removing from your image before you can process it properly.

HTH

Carole 

 

[iwols]

thanks keep meaning to have another go with phd,but when time allows there seems to be something else to get your head round from memory i found the blue and red track lines just flew off the scale and never returned,i think

[carastro]

OK, well one thing that sometimes trips people up is calibration steps (in the Brain), if it is set too low then calibration often won't work, but that doesn't seem to be your problem.

Things to think about:

How good was your polar alignment?

Any cables snagging?

Any flexure between the finderguider and the imaging scope. 

How good was your focus on your guide camera?  

Did you choose a guide star that was big, you only need a small star for guiding. 

Confirm you were on sidereal tracking. 

You need to calibrate in the area you are going to image in.  If you move away from the area of calibration you need to re-calibrate.  

Clouds upsetting the guiding. 

Have you got a dew heater for the guide camera, if it mists up it will upset the guiding. 

I am sure there are other things I may have missed.

I really think you should sort your guiding problems out as a priority as you will be seriously hindered without and a waste of a good imaging camera. 

Carole 

[iwols]

your right i must sort it out ,you can still use stellarium at the same time cant you,off to find a good video on phd set up now cheers

[carastro]

Quote

you can still use stellarium at the same time cant you

I presume you mean to control your Mount,  yes that should be OK.

Carole 

 

[iwols]

so i presume phd2 works alongside the sidereal output from stellarium  then?

[carastro]

I have used EQMod in the past and that doesn't drive the mount unless you give it commands to do so.  Neither does another software I have used that controls the mount, think that was Sky6.  Presume Stellarium works the same way, PHD works independently.  

Carole 

[iwols]

thanks what i mean is i use stellarium to find my target,which is obviuosly in sidereal mode then i start phd2 guiding does it stop in sidereal but phd just buts in now and again to make corrections,hope that makes sense thanks

[geordie85]

51 minutes ago, iwols said:

thanks what i mean is i use stellarium to find my target,which is obviuosly in sidereal mode then i start phd2 guiding does it stop in sidereal but phd just buts in now and again to make corrections,hope that makes sense thanks

Your mount should start sidereal tracking once you slew to a target. PHD just sends corrections to the mount to either speed up or slow down the sidereal rate to keep your chosen guide star in the same place on its sensor.