Flats from different sessions
Stacking program, astrometric (plate) solver, fits file viewer
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I image using 8" and 10" carbon fibre Newtonian reflectors and a 2600MM mono camera with Antlia filters
Most of my light frames are generally captured over many different nights where my camera is removed and re installed each session , therefore I always capture new Flats each night session.
I always capture my lights , flats and flat darks for a particular filter ( eg: Ha ) over one night and complete that Ha filter's data on following nights , capturing more lights , flats and flat darks
For darks I use my Dark Library.
When stacking Ha , ie: the multiple nights of data for that Ha data set , I just load all my multiple lights into lights tab , all my multiple Flats into Flats tab, Darks into darks tab from library and multiple Flat darks into dark flats tab.
In regards to stacking multiple Flats from diferent nights for same filter ( Ha) should I be checking the Classify date box or does ASTAP know which Flats to calibrate with respect to light frames from different nights ??
Currently I have not been checking any Classify boxes at all for multiple night capture of lights , flats and flat darks relating to one filter eg: Ha
I welcome advice on the above and the correct procedure
Regards
Martin
After scouring the ASTAP forum , Stargazers Lounge and Cloudy nights I found my answer
For calibrating more than one set of Flats ie: Multiple nights capture where camera was removed and re nstalled or image train changed , use "Classify by date for Master creation " in the Flats tab located at the top.
Found this post on SGL back in 2021
https://stargazerslounge.com/topic/375334-astap-vs-dss/
Found this post in ASTAP forum back in 2021
https://sourceforge.net/p/astap-program/discussion/general/thread/7ae45b3019/
It would be most helpful if the ASTAP Documentation was updated with the above information relating to Flats.
Martin
Hi Martin,
I will improve the manual.
The program will automatic select the best suitable master flat based on exposure time and date.
But make the master flats one by one. Once one is made it is only used and not effected/modified when loading new individual flat frames.
Cheers, Han
Hi Han,
Im very strict when it comes to capturing Flats per session per filter as I soley use Newtonian Reflectors and my image train suffers severe vignetting. caused by my coma corrector. Presently we are only getting 2 clear nights per month , so in order to gather say 10 to 15 hours of data on a particular object , one can take many nights where my camera is removed. Sometimes I can have up to 3 to 4 sets of Flats per filter to complete a project.
This feature in ASTAP for creating Master Flats by date is a ideal for my imaging.
Also updating the ASTAP documentation will be a big help. It is a little out dated for newcomers using ASTAP for the first time,
Thank you
Clear Skies
Martin
I have rewritten this part of the help file:
http://www.hnsky.org/astap#classify
If something is unclear/missing, please tell me.
Han
Han,
Just a suggestion, why not use a similar explanation you wrote in SGL back in 2021 and include this under both Flats tab and Darks tab in documentation as follows -
1) Master flat and master dark can be created based on date. So you can add all flats to the flats tab and per day a master flat will be created. This is activated by option "classify by date for master creation"
2) For the light the master dark and flat with the nearest date will be selected. This will happen if more then one compatible flat or dark is found.
I think its important to identify and explain those Checkboxes at the top "Classify by date for master creation" to be used for Flats taken over multiple nights etc...
Also to "distinguish" them from the standard 6 Classify checkboxes at the bottom ( filter , object , exp time , gain etc.... )
Your thoughts ?
Martin
Hi Han,
I forgot to mention that I capture Flat Darks after my Flats for each night session on each filter over many weeks ( Like my Flats , I could have up to 3 or 4 sets of Flat Darks for each filter )
When I load all my multiple nights Flat Darks into ASTAP , how does it know which Flat Dark to calibrate with each Flat as there is no Classify by date option ?
In Flat Darks tab should I be selecting say Classify by Dark exposure time at the bottom ?
Await your advice
Thanks
Martin
I will rewrite the text a little.
For the flat-darks (bias) it is assumed the can be used for a longer time. Flats can be different if you collect new dust particles especiall in a mobile setup. Dust particles do not influence the flat-darks.
Personally I do not update my flats for months. I try to keep them dust free and then they work fine for a long period
But I agree flat-dark temperature would have an influence. If you flat-darks are made with an temperature controlled cooled camera this will work but not using a DSLR camera. Influence will be relative small since the flat is exposed with a lot of light.
Assume you have four filters, the idea is you make for each filter one flat series so total four. And only one flat-dark series. So if you process the frames of a mobile setup after two nights then you do this in two steps. So process first 4 flats+1 flat darks series from the first night and then again 4 flat +1 flat darks. Does that work for you?
If you want to process the all in one step the program has to look to the dates of the flat-darks. I assume they are made at the same moment as the flats so the temperature should be simular. Anyhow a check on simular temperature and gain and warning if not could be helpfull.
Hi Han,
Thanks for your reply
Heres a brief rundown of my set up and calibration ......,
I image with 8" and 10" Carbon Newts and use both 2600MC camera with filter drawer ( Antlia ALPT 5nm dualband ) and 2600MM camera with ZWO 7 x 2" EFW ( Antlia LRGB and Antlia 3nm SHO )
Ive never tried re using Flats for long periods of time , everyone advises to take new Flats for each capture and Flat Darks ( matched temp and exposure of Flat ) not Bias for calibration. ( My Flats for LRGB are around 0.15 sec to 0.50 sec and for SHO are 1.5sec to 5sec . Folk say dont use Bias ( 0.000032sec ) you must use Flat Darks matched to Flats temp and exposure time for the 2600 series camers ( Sony IMX571 sensor ) It is a time consuming calibration process. I even create a Dark Library every 6 months for both cameras , and some folk advise you dont need Darks for the 2600MC and 2600MM cameras, but I still use them.
My ZWO 7x 2" filter wheel is always kept fixed to my 2600MM camera and TS GPU coma corrector so no dust can enter.
I welcome your experience and advise on how i should move forward with streamlining my calibration process. I do think im going beyond what is actually technically required , "maybe " ???
Martin
If I keeping adopting the same calibration capture process for multiple nights captured on the same filter where my camera is removed and re installed ,and I take Flats and Flat Darks for each filters imaging run, could I successfully stack them as follows -
Example where different data per filter are captured many weeks apart ......,
Ha filter
Night 1 Lights , Flats and Flat Darks
Night 2 Lights , Flats and Flat Darks
Night 3 Lights , Flats and Flat Darks
Oiii filter
Night 1 Lights , Flats and Flat Darks
Night 2 Lights , Flats and Flat Darks
Night 3 Lights , Flats and Flat Darks
Sii filter
Night 1 Lights , Flats and Flat Darks
Night 2 Lights , Flats and Flat Darks
Night 3 Lights , Flats and Flat Darks
Darks Library used to match Lights for exposure , temp , and Gain / offset
Proposed .........
Ha Lights , Darks, Flats , Flat Darks
Stack Ha Night 1 using Sigma Clip improved ( fts)
Stack Ha Night 2 using Sigma Clip improved (fts )
Stack Ha Night 3 using Sigma Clip improved (fts)
Stack Ha combine N1 ,N2 ,N3 using Average ( fts )
Oiii Lights , Darks , Flats , Flat Darks
Stack Oiii Night 1 using Sigma Clip improved ( fts)
Stack Oiii Night 2 using Sigma Clip improved (fts )
Stack Oiii Night 3 using Sigma Clip improved (fts)
Stack Oiii combine N1 ,N2 ,N3 using Average ( fts )
Sii Lights , Darks , Flats , Flat Darks
Stack Sii Night 1 using Sigma Clip improved ( fts)
Stack Sii Night 2 using Sigma Clip improved (fts )
Stack Sii Night 3 using Sigma Clip improved (fts)
Stack Sii combine N1 ,N2 ,N3 using Average ( fts )
Calibrate and Align
Stack Ha combined ( fts )
Stack Oiii combined (fts)
Stack Sii combined ( fts )
Final Aligned Ha stack ( fts) ready to load into Startools Compose Module
Final Aligned Oiii stack ( fts ) ready to load into Startools Compose Module
Final Aligned Sii stack (fts ) ready to load into Startools Compose Module
Will the above stacking process for multiple mights hypothetically work Ok ????
Await your advice
Thankyou
Martin
I have a ToupTek camera with the same IMX571 sensor.
Not using darks is ill advised. I really don't understand why this goes around. You can clearly see the IMX571 sensor has still hot several pixels and some random telegraph noise. The noise goes down if you apply darks. Secondly the flat correction will not work properly without dark and flat-darks pedestal value. The pixels in the frames have also a natural variation in the pedestal value. Only if you have very poor skies maybe you will not notice in the images.
If you have a fixed setup and no visible dust particle changes, I would not bother making flats each capture. As said before I make new flats and flat-darks maybe in a 3 or 6 month interval and do it with an electroluminescence flat panel during a cloudy night. As long you keep the exposure times, temperature and gain matching it will work fine. Every few month I see a new large dust particle on my camera images and the only thing I do is to blow the camera front window clean and put it back. I do not like using the flat to correct for dust. My 2" filters (H-alpha and luminance) are pretty far away (a few cm's) from the camera and dust on these is in practice invisible
The setup is permanently in my observatory with a lot of natural ventilation.
The two options marked green are probably better moved down. Even I have the tendency to forget about them. Probably also adding alos the gain in the check is better.
I originally put them up not to make the menu too difficult.
Moving the menus down is not such a good idea. It is only related to the flats and not to stacking
Check-mark "Classify by date for master creation"
Using the flat-dark date in the selection doesn't bring anything. The flat-darks will be identical for every date. So the date selection only apply on the flats.
Check-mark "Classify by exposure for master creation"
The flat and flat-dark exposure should be the same. I'm not so sure if the gain has an influence on the flat-dark but I could add the gain. Same for the temperature. So I could change it in:
"Classify by exposure, temperature and gain for master flat creation"
The 2 options are fine where they are located , I suppose the updated notes are the important part.
Do you think my stacking procedure above should work ok as my set up is not permanent ?? If its ok I probably would not need to use the Flats tab "Classify by date for master creation" as my stacks for each filter over 3 nights are individually stacked using Sigma Clip improved and combine later stacking with Average. Master Flats would be created initally for each stack by selecting the option
“Replace checked - marked by master flat , flat dark included “
Is the above procedure Ok ?
Martin
I forgot to mention
All my Lights , Darks , Flats and Flat Darks always have same Temperature and Gain
If the setup is not permanent it should work as long the flats and corresponding lights are made on the same night. This to cope with any dust particles. But if there are no significant dust particles it could be done at separate nights
Yes for same temperature and gain then the date doesn't matter as long there is no new dust on the filters/camera windows, if any.
One more thoughts about DSLR cameras:
Check-mark "Classify by date for master creation"
DSLR users have no control on the temperature. They often have also no temperature indication. So then probably it is better to make it more strict as follows:
Check-mark "Classify by date for master creation (flats and flat-darks) "
I will make so changes and then update the help file.
I made some changes but I think I'm on the wrong direction. Creating each master flat can be done by selecting the flats and flat-darks of each evening and hit the button to make a master dark.
So creating the master flat is straight forward task for each filter. The flats of each filter will be matched with the corresponding lights. So separating the flats on exposure, gain and temperature is not very usefull. It is better to warn the user only that the flat and flat-dark are not ideal for the task. So it is probably better to remove the menus and keep it simple.
Attached the new menu. But better to remove them
Last edit: han.k 2024-05-21
I would just combine the three nights as they are made during one night. The equipment has not changed during the nights.
If you would have a mobile setup then the only thing to do it to make for each night a masterflat. The program will select automatically the best matching masterflat based on the date. So the lights from night 1 will be calibrated with the masterflat from night1. Same for night 2 and 3. If more then one compatible master flat is found, then it will select the flat with the nearest date automatically.
Last edit: han.k 2024-05-21
Han,
My example above Night 1 , Night 2 and Night 3 for each filter S,H, O are different nights on different dates where I have to remove the camera each night and re install !!!
Hope that makes it clear
Martin
So on Night 1 ,I captured Ha , Oiii and Sii data sets including Flats and Flat Darks
Then a few weeks later Night 2 more SHO data sets " " " "
Then say a month later Night 3 my final captured SHO data sets " " " "
Camera removed and re installed on all three Nights
Yes but should not be a problem. I combine sometimes new frames with old frames from last year. The only thing you should organise it to keep master flats There would be no need for more then one master dark unless you change gain, exposure duration or temperature. But better to keep the setting always on unity gain and same exposure.
Honestly I personally never used the options "Classify by date for master creation" and "Classify by exposure for master creation". So at the moment I think they can be removed but will rethink it tomorrow morning.
Cheers, Han
I'm working on some improvements in reporting. Not so easy.
Minor issues are only reported in the results and in the headers. Selection issues are report in the flat and darks tab.
Correct attachment
Thanks for your input
For my Flats, the Classify by date for Master Creation is still an option by I will try with and without using it for my multiple nights captures.
Im sure my camera assembly with filter wheel and coma corrector is relatively dust , so testing will prove otherwise
Thanks
Martin
I have updated the manual again and released a new ASTAP version. Tell me if it works for you or if something is unclear.
Han
Last edit: han.k 2024-05-23