How to take Light, Flat, Bias & Dark Calibration Frames for Astrophotography

imaging the nighttime sky can be one of the most rewarding things to do in amateur astronomy you're literally collecting photons of light from objects that are hundreds thousands or even millions of light years away this process can also be complicated and in today's video we're going to break down the basic steps and techniques and how to capture light flat dark and biased frames to greatly improve the details of your images and astrophotography if you enjoy this video please like it and subscribe to this channel but most importantly let me know about your questions and techniques for improving these frames in the comment section below now let's get started by taking a look at the most important part of this process collecting the actual data of the target that we're imaging this night and what we call our light frames light frames are the most important part of this process because they're the actual data of the object that we're capturing in the nighttime sky nothing else beyond this initial process really matters unless we have sharp properly exposed images to work with down the line an important concept to understand for our light frames is referred to as the signal to noise ratio basically the more light frames we have the more we can stack that data to pull out fine details of these deep sky objects a resource that's helped me greatly with understanding some of these concepts is the deep sky imaging primer 2nd edition by charles bracken and i'll be sure to leave a link to it in the description below tonight i'll be capturing my light frames using a dslr samyang 135 millimeter lens and the ioptron sky guider pro tracking mount which is already polar aligned and ready to go there are three main things that we're going to do to make sure that we have excellent light frames to work with and those are making sure our camera's quality is set to raw adjusting our focus and setting our exposure to the proper length i've got a video that goes into more detail of other specific settings such as choosing things like your iso and f number and we'll be sure to tag it and include a link in the description below to capture our light frames let's start by setting our camera to manual mode and raw quality next let's work on getting sharp focus for our light frames by focusing our equipment on the brightest star we can find one thing that can help you with this is a botanav mask after placing it over your camera lens slowly adjust focus until the center spike is perfectly between the other two spikes now that our camera is set to raw and we've adjusted our focus let's turn our attention to making sure that we get the proper exposure time for our target tonight which for me is the orion nebula let's test out different exposures for our light frames by taking a 15 second 30 seconds 45 second and one minute exposure to determine which exposures worked best i'm going to press the info button to see the difference in the histogram for each image the trick is to get a histogram that is about three-fourths of the way over to the left too far to the left and you don't have enough difference between your object in the background of space too far to the right and you may lose some of the brightest details of your object from the data getting clipped off tonight it looks like the best exposure for me will be somewhere around 20 seconds the exposure time that you choose is going to vary greatly it's going to depend on the target that you're imaging the capabilities of your tracking mount and even the light pollution of your area to assist you in capturing your light frames use something like a remote shutter release trigger to set how many exposures you want and how long you want them to be my goal tonight is to capture at least 200 separate 20 second light frames of the orion nebula before it gets too low to the horizon and enters a good deal of light pollution in my area remember these light frames are the most critical part of the process and will take up the bulk of your time with your night of imaging the more light frames you have to stack together later on in the process the greater your signal-to-noise ratio will be which will bring out faint fine details of these incredible deep sky objects [Music] alright i'm back outside after my camera has captured some incredible images of the orion nebula for about the past hour and 15 minutes my attention now turns to capturing the additional frames that will be used to take out any imperfections in these light frames that were just captured and we're going to do that by beginning the process with capturing flat frames flat frames will improve the quality of our image by removing unwanted differences in brightness such as vignetting and dust shadows on our sensor to get rid of these imperfections your flat frames need to be perfectly illuminated across the entire field of view when you capture them to accomplish this i like to use the incredibly sophisticated and expensive scientific instrument known as the white t-shirt begin by making sure your imaging setup is in the exact same orientation as it was for the light frames and make sure you are still shooting in raw quality with the same iso and f number as before the only thing you will want to change on the camera is the mode from manual to av carefully stretch a white t-shirt over the lens hood making sure there are no wrinkles once that's done you're going to need a light source to evenly illuminate it i like to use a white background on my iphone with the brightness turned up to 100 percent with both of those things in place press the shutter button to take your flat frames as for all these frames the more the merrier but there is obviously a diminishing return when you get to a certain point on most nights of imaging i like to take around 75 flat frames our next type of frame is the quickest to take and simply requires you to place the cap on your lens to make sure that no light gets onto your sensor these bias frames will improve our image by removing the bias signal and read noise from our sensor switch your camera back to manual mode and be sure to keep the same raw quality and iso setting that you've used all night go into your settings and select the fastest shutter speed available for your camera for this camera that's a shutter speed of 4 000. with all of these settings in place click your shutter to take as many bias frames as you'd like on most nights i like to take around 75 of these as well [Music] finally we end our night with dark frames these are used to improve our image by removing the thermal signal and hot and cold pixels that may have showed up throughout the evening like bias frames you want to make sure your lens cap is on so that no light hits your sensor but unlike bias frames you want your exposure length to be the exact same as the light frames that were captured earlier in the evening what i would suggest you do is keep your equipment set up just as it was outside and use your remote shutter release trigger like before to capture your dark frames at the exact same length as your light frames were earlier in the evening i normally try to take between 75 and 150 dark frames it just depends on how long the exposure times are the temperature changes outside and honestly what time i want to get to bed that evening i hope you've enjoyed this video on how to take all of these different types of frames in astrophotography i'm going to have a video coming up soon that i'll be sure to tag and leave a link to in the description below that's going to walk you through exactly how to stack each of these frames in deep sky stacker for the next step of our process be sure to check it out if you're interested please let me know in the comments section below also about any questions you have or techniques that you know of to improve this process even more thank you all so much for your continued support and clear skies from late night astronomy

Channel: Late Night Astronomy

Views: 12,085

Keywords: light frames, dark frames, bias frames, flat frames, how to take light frames, how to take dark frames, how to take bias frames, how to take flat frames, stacking dark frames, stacking bias frames, stacking flat frames, astrophotography, how to take light flat dark and bias frames, best techniques for astrophotography, deep sky astrophotography, how to stack frames, signal to noise ratio, stacking light frames, light, dark, bias, flat, how to take calibration frames

Id: u6Zk_LQDOD8

Length: 10min 2sec (602 seconds)

Published: Tue Apr 06 2021