Matching Subexposure Data

Reggie Jones

Hi Adam.  I've downloaded Telescope Live LRGB data for the galaxy Messier 74.  There are 222 total sub exposures taken on the SPA-2 telescope; 57 subs were taken at 300 sec each and the remaining 165 subs are at 120 sec each.  Upon blinking them at the start, the 300 sec subs are binned at 2x2 and the 120 sec subs are binned at 4x4.

Trying to figure out my plan to process all the data into a single image; my initial thought is to resample the 2x2 sub exposure data to 4x4 using the Integer Resample Process via a Process Container and then combine and process all the data together.  I've not used the Integer Resample process very much (I think I've used it once in post processing); I've reviewed the documentation but I did not see a specific tutorial you might have on this process.  There is also a Resample process and I'm not sure what the differences are with these processes.

Would like to know your thoughts if I am thinking through this logically or if I need to consider something else...?  I initially thought of processing the 2 datasets separately and then combine them later in post processing but discarded this idea as I realized that would require using Star Alignment to align all the subs which I don't think would work because they are binned differently...

Thanks in advance...  Reggie

BlockHead

Assuming the data you have downloaded is already calibrated, your integer sample idea is just fine. I did demonstrate this somewhere... 

The difference between integer resample and general resample is that the general will interpolate pixel values- whereas integer resample just combines (or divides) the values of the data into bins evenly- no interpolation.  This is what you want to do to maintain the proper signal characteristics. 

You will need to calibrate them first before doing the resample if that are raw. 

Once you have done this, you should be able to treat the images normally. Force the registration reference to be one of the native 4x4. In this way the platescale and such will be correct for the Astrometric solution (since your resample will not be reflected in the header). 

You are correct that WBPP will always produced different masters for differently sized images.

-the Blockhead

Reggie Jones

Thanks Adam - if you remember where you demonstrated Integer resample, please let me know so I can review it.  I'm thinking there was something you did on merging older datasets with new data - maybe it's in there somewhere... I'll try to run that down and look.

Reggie