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08-27-2018, 08:37 PM - 12 Likes   #1
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A beginners guide to Astrophotography

Continuing with my beginners guide to shooting the night sky series we will move on from shooting the simplest object in the night sky to chasing other things. Last time we went after the moon which is a good place to start as it is big, bright, and easy to find. Thus it is always a good place to start to start mastering things. Now we will go deeper and shoot things farther away. Starting with things that are largest in the sky. Before going there lets cover some of the basics to get everyone pointed in the general directions.

Equipment
Lenses
While the moon is a pretty forgiving target and a kit lens or cheap zoom will work other things in the night sky demand something good and fast. Zooms will work but even here you will want them on the wide side of things. Again as fast as you have. Wides work best for landscapes where you want to have a huge expansive night sky in them like those pictures where they have the milky way arching over the entire view. You can also get some great whole sky star trails with these lenses.

Once you get past the wides you have normal lenses in the 35mm to 55mm range. These lenses produce great results as they are generally inexpensive lenses high quality and you can get some great old ones for very little. I mostly use lenses like this for capturing some foreground landscape with either a generic star field or with a constellation in them. Almost all constellations will fit in the field of view of a 50mm lens on an APS-C camera. Last spring I got all of Orion near the horizon with a frozen lake in the field of view. The other nice thing with these lenses is that other objects start becoming visible as there is something more there. These are the larger and brighter Messier Objects which are good starting points for Deep Sky Object (DSO) photography. With these lenses planets will still appear as dots that are slightly brighter than the other dots in the sky. With these lenses go for fast, your 50mm f/1.4 is ideal for this type of shooting. While a narrower field of view star trails still look good with these lenses.

Going up from there you have your telephotos and ultra-telephotos. Now these aren't as fast as the normals unfortunately. the good news is that you can just crank up the ISO and stack images (this will be its own topic later) and get some good results. With these lenses you can get some pretty nice images of the various Messier Objects, even the dark ones in badly light polluted areas. Even something like the old Pentax-M 200/F4 lens can produce stunning results (holy crap Pete quit makign the rest of us look like we don't know how to operate a camera) with practice. I highly recommend that you have some form of tracking when using these lenses so that you can get more exposure. With these lenses you will also now start to see planets as disks, saturn with ears, and jupiter's moons.

After this just go get a good telescope and an eyepiece that lets you connect it to your camera and really chase DSOs and get some good planet pictures.

Tripods:
When doing these shots you will always need a tripod or some sturdy place to stick your camera and lens. Shots will range from .5s up to several minutes depending on what you are doing so you will need a tripod. The heavier the better too. The only question you should be asking is do you get a tracking mount now or will you just work around that. A tracking mount allow you to take some nice long exposures to capture those precious few photons. These are fairly expensive for ones that aren't garbage (my understanding is expect them to start around $600-$700 and only go up from there) so if you are unsure if you want to do this don't buy one right away there are ways to work around it that can produce some pretty reasonable results.

Other gear:
Other things that are must haves include an extra battery or 2, as well as a release cable. You can get all fancy and get an intervalometer which will make things easier as it will push the button for you but you don't need that. I made my one release cable with extra big buttons so that I can used it with mittens on for about $10 so you really don't need to get super fancy. If you are shooting a a very light polluted area you may also want to consider getting a red enhancing filter. It turns out that these filters are actually a pretty good poor mans light pollution filter. I haven't used one but others around here swear by them. I strongly suggest against using any other filters they can only do more damage to the image that any benefit they offer in the form of reflection, loss of precious photons, aberrations, etc. This means take off those UV filters, ND filters, and CPLs.

The last key item you really need is a focusing aid especially with telephotos. For wides and normals focusing using live mode works but with a telephoto or telescope an aid is basically essential. The preferred aid is the Bahtinov Mask which produces a useful diffraction pattern that lets you know if you have the perfect focus or not. The nice thing is that you can create a template for one with an online generator.

Location and time
One thing that people quickly find out is that what is up in the sky varies over the year. If you are unfamiliar with what is up there are tools available to help. The simplest is a star chart and you can either buy a nice one or simply print your own for a given month. One thing you will notice is that there are different ones for your latitude so pick the right one. These are nice and the ones you can buy offer a lot of neat features like picking the date and time and showing what is up. If you would rather not use one of those there are smart phone apps that offer the same functionality. I use StarWalk2 (free) or SkyMap. The best feature of these is that they take into account the compass, tilt, and GPS data that your phone offers and can show you want is in the general direction of where you are looking. One program I recently found out about and haven't had a chance to use is Stellarium which some of the masters of astrophotography around here use so it can't be all bad.

Now that you know what is up and when it will be up now you need to find a location to shoot in and be there at the right time. There are are better times and better places to shoot. Basically the darker it is the better results you will get. To find a dark place I like using this website which does a pretty good job of showing the amount of light pollution. Here you will notice that when you click on a spot it gives a bunch of info. Probably the easiest thing to understand with that info is the Bortle class which will let you know what is naked eye visible. Thankfully your camera can see more than this but darker is always better. For example my backyard is a very bright Brotle 8 but I have photographed one of the dimmer Messier Objects, M51 the Whirlpool Galaxy, about an hour after sunset.

This is bring me to the next point which is when to shoot things. Ideally you want to be out shooting when it is actually dark, not dusk, not civil dark ,but proper astro dark. To find out when this is you can use this site which also give an astro observing forcast for your location. It is also a good idea to check the weather too as high humidity and wind only make things worse for you. Here in minnesota some of the best time for astro shots is in the winter when it is cold and dry, if you have similar conditions they may be worth shooting in but the cold eats batteries.


Shooting Technique
Here are some general rules for shooting technique depending on the gear you have.

First is if you can shoot as high in the sky as you can. The reason for this is that it cuts out a lot of things that detract from your image. This includes sky glow at the horizon, humidity, haze pollution, etc all because you are shooting through less atmosphere when point more up. So plan your shots and night accordingly. For shots that involve a landscape this is something you will need to keep in mind and plan your shot accordingly. Sky glow can create some nice silhouettes of items in the foreground.

The next recommendation now becomes very dependent on what equipment you have but this is exposure time. There are 2 routes to go here you can either have pinpoint stars or you can go for star trails.

Getting trails is actually easy. You just need total exposure measured in minutes or hours depending on how long you want those trails to be. My advice here is get the exposure right for 1 30 second exposure (find a reasonable ISO and f-stop) put the camera in continuous shoot mode and let it blast away until you have enough exposures to get the long trails you want. Then just combine the images in photoshop or what ever your favorite software and blend them with brightness. This will give you the nice trails. For getting star trails all you need is the release cable and a good tripod.

Getting point stars is more difficult. If you have a nice tracking mount it is a matter of getting it polar aligned and then keeping the exposures short enough so that the error in each doesn't accumulate too much. This will give you the longest exposures which means the best data.

For those of us not lucky enough to have a tracking mount like that you may have tracking built into your camera or with a small add on have the ability to gain it. Here I am talking about the astrotracer function built into newer pentax cameras. Much has been written about it with people getting mixed results or having incorrect expectations. Having played with and used astrotracer with the external O-GPS1 on my K-3 it is kind of finikey and you have to understand what throws it off. First off calibration is key, this takes practice, so go and do it. I have gotten to where I can get it calibrated on the first attempt for the regular and fine calibration with my 300mm lens attached but the first time I tried before I went out it took some effort and even then wasn't right. Next up is to be sure you aren't setting your self up for failure, magnetic fields and high iron content nearby throws it off. So don't set it up by your car, home AC unit, under power lines, etc because all of these will throw it off. Finally pentax has always seemed overly optimistic in astrotracer's ability to track for long periods of time. They claim up to 5 minutes but you are just fooling yourself at that. I find that the best results are achievable when one stays under 1/4 of whatever the recommended maximum time its. For example with my 300mm lens I will typically take 20 second exposures and the recommended maximum time is usually between 110 seconds and 140 seconds. I have tried some shots longer than the 1/4 maximum but in every case I started getting noticeable trails after that and since I usually go after DSOs you really don't want trails. When using astro tracer always take a sample picture before you start blasting away and check that exposure is at least reasonable. This means checking that the tracking is good, that you are getting a nice starfield, if you are shooting something like M51 in my backyard that you can find the smudge that it appears as just above the noise floor of the image. Adjust ISO and exposure as necessary.

For those who don't even have astrotracer you are stuck with the rule of XXX. Here XXX is some number, typically 600, 500, 300, or 200. Basically take the number and divide it by your focal length to get the maximum number of seconds you can shoot for without getting noticeable trails. The 600 and 500 is for not noticeable trails on a full frame camera, with 500 being the one most used. On a APS-C camera 300 will give you no noticeable trails. If you want to have no trails you should use 200 for APS-C and 300 for full frame. This is how I started out shooting DSOs and got some not awful results. Now when shooting with normal and wide lenses you can see that we don't really need tracking. A 50mm lens would give you 4 seconds of exposure on an APS-C camera with no trails (rule of 200), a 14mm lens would give you almost 15 seconds of exposure with no trails. If you want to have slight trails (rule of 300) that aren't noticeable you can get 6 seconds with a 50mm or almost 20 seconds with a 14mm lens.

Settings
Having seen a number of astro images and taken some non garbage ones myself here are some setting reccomendations

Milky Way:
ISO 1600 to 3200
F-Stop: 1.4 to 4
Shutter speed: 10-30 seconds
Lens: Wide to Normal
Find a dark area, if you can sort of see it your camera can really see it.
Can bring out color and detail with some light post processing in Lightroom, photoshop, Gimp, rawtherepee, etc. Doesn't need to be stacked but that will improve image quality.

Constellations:
ISO 400-1600
F-Stop: Wide open to about 5.6
Shutter speed: 10-15 seconds
Lens: Normal
For the bright ones you can get these with ease in very light polluted areas
These don't normally need stacking and good results can be achieved with some light post processing in Lightroom, photoshop, Gimp, rawtherepee, etc. If you do stack these photoshop can handle them pretty well.

Planets:
ISO 100-400
F-Stop: go for sharp but close to wide open
Shutter speed: I get color when close to 1/30 to 1/60 of a second when shooting jupiter but the 4 Galilean moons appear at about 1 second of exposure at ISO 400.
I have shot this off my deck at dusk so don't worry about light pollution here.
A special note on planets is to instead use your camera and take a video through a big telescope. Then process it in a program like Autostakkert!3 or RegiStax if you just take a pile of stills. Stacking becomes really important for bringing out the detail in planets. Once you get a stacked image you will need to do a fair bit of post processing.

Deep Sky Objects (DSOs)
ISO 400-3200 (tracking dependent)
F-Stop: As open as you can get it with acceptable chromatic aberrations and purple fringing (you will find out just how good your lens it when shooting these)
Shutter speed: As much as you can have without trails. Here you are looking for total exposure time. I would really recommend at least 30 minutes total with several hours being ideal.
You will need to stack and you will need to do a lot of post processing. For stacking there are 2 programs that I see come up frequently here because they are good as stacking these. One is Deep Sky Stacker (DSS) and the other is Astro Pixel Processor (APP). DSS is free and APP is a pay program. These are more advanced topics that deserve their own thread which I will get to another day.

Hope this helps get people out there shooting. Remember this is just a beginners guide meant to get someone out there shooting in the right direction. I will also post some example photos later too.

08-28-2018, 03:12 AM   #2
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I've only briefly scanned this article, but there seems to be a lot of valuable knowledge imparted here. Although it's not an area of personal interest for me (yet), I'm looking forward to reading and absorbing this more thoroughly later today!

Thanks for posting... Sharing knowledge like this is one the nicest aspects of PentaxForums
08-28-2018, 04:05 AM - 2 Likes   #3
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As promised here are some pictures. Note that there has been a fair amount of post processing with these.

A stacked image of orion taken with my 35mm plastic fantastic. My best guess for the settings used here were ISO 400 at a few seconds. I don't know how many images were stacked as this was one of my very first attempts.


Here we have the big dipper. This is a stack of 10 images 15 second exposures taken with my 28mm SMC Takumar. ISO 400 fairly early in the evening. This was cropped down to this size. I combined the stacked sky with one of the foreground exposures so that the trees weren't blurred to get this.


Here we have Jupiter and the 4 Galilean moons. This was a single 1 second exposure at ISO 400. I used my Sigma 300mm F/4 APO lens. Note the slight trailing from the movement. This is a 100% crop.


This is one that I captured recently. It is M51 and it was in the park behind my house about an hour after sunset. It was captured using astrotracer with the K-3 amd Sigma 300mm F/4 APO lens. This is a 100% crop. 18 20 second exposures at F/4 at ISO 800. There was a lot of light as the last picture was taken on a little more than an hour after sunset with a 3/4 moon up, with haze and humidity in the summer air, in a bright Bortle 8 area.


This is a picture taken using astro tracer and my 55mm SMC Takumar of the orion constellation. The Orion nebula is clearly there. The blurring of the foreground is because astro tracer keeps the stars stationary. I believe that this was a stack of 6 60 second exposures at ISO 100 with the lens stopped down to F/8.
08-28-2018, 06:47 AM - 3 Likes   #4
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QuoteOriginally posted by BigMackCam Quote
I've only briefly scanned this article, but there seems to be a lot of valuable knowledge imparted here. Although it's not an area of personal interest for me (yet), I'm looking forward to reading and absorbing this more thoroughly later today!

Thanks for posting... Sharing knowledge like this is one the nicest aspects of PentaxForums
QuoteOriginally posted by BigMackCam Quote
Thanks for posting... Sharing knowledge like this is one the nicest aspects of PentaxForums
That is what I am going for. I have learned a lot from others here and since these are items I keep seeing others ask about I figured that since I do know something why not write it all up in one place and then can refer someone who is just starting to them. I don't inted for this to be the be all end all on the subject but it should get them going. Get them off on the right foot so that they don't have to make all the mistakes I and other did when starting out is the goal. As a side benefit these posts should up the signal to noise ratio of the posts as some around here a putting up a lot of little to no effort posts.

08-28-2018, 07:03 AM   #5
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Last edited by monochrome; 08-28-2018 at 03:31 PM.
08-28-2018, 10:04 AM   #6
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QuoteOriginally posted by MossyRocks Quote
Hope this helps get people out there shooting.
Thanks for compiling this guide, a very useful starter.
08-28-2018, 10:36 AM - 1 Like   #7
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QuoteOriginally posted by Kevin B123 Quote
Thanks for compiling this guide, a very useful starter.
Great to know that people are finding benefit in it. If others have tips for beginners that helped them please post them. Lets get an info dense thread that is really useful.
08-28-2018, 10:54 AM   #8
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Nice job compiling this, cant wait for a clear night to go out and do some astrophotography

08-28-2018, 11:13 AM   #9
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Thank you for the guide, I been itching to give astrophotography a try but didn't know where to start.
08-28-2018, 12:12 PM - 1 Like   #10
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QuoteOriginally posted by Sapper Quote
Thank you for the guide, I been itching to give astrophotography a try but didn't know where to start.
Then stay tuned because I will probably write up a beginners guide to processing astro images in the next day or 2 as that is the other major part of astrophotography. I haven't processed a milky way image as things just refuse to cooperate but I have done DSO processing so will focus on that. Pete_XL got me pointed in the right direction as I found some tutorials that lead me down the very wrong path initially. Pete has taken a stab at some of my image data and gotten some impressive results and I keep on practicing and am getting better but he is a true master and has much more experience. He finds things in my images that didn't know were there.
08-29-2018, 12:31 AM   #11
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QuoteOriginally posted by MossyRocks Quote
Then stay tuned because I will probably write up a beginners guide to processing astro images in the next day or 2 as that is the other major part of astrophotography. I haven't processed a milky way image as things just refuse to cooperate but I have done DSO processing so will focus on that. Pete_XL got me pointed in the right direction as I found some tutorials that lead me down the very wrong path initially. Pete has taken a stab at some of my image data and gotten some impressive results and I keep on practicing and am getting better but he is a true master and has much more experience. He finds things in my images that didn't know were there.
Thank you Mossy, I'll be looking forward to reading it.
08-29-2018, 10:44 AM   #12
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Thank you for taking the time to write this up! Very useful.
08-29-2018, 10:51 AM - 1 Like   #13
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QuoteOriginally posted by Binth Quote
Thank you for taking the time to write this up! Very useful.
You're welcome. Now I just need to find the time to write the other up so that it beginners can know what to do with all those hopefully not awful first astro pics they just took.
08-29-2018, 10:59 AM   #14
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Yes! Processing is the part I struggle with the most.
08-29-2018, 11:46 AM - 1 Like   #15
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QuoteOriginally posted by Binth Quote
Yes! Processing is the part I struggle with the most.
I still struggle but no where near as much as I did. Now I struggle to get near the fantastic results guys like Pete_XL, DrawsACircle, VoiceOfReason, and others more experienced in editing can get, but I keep trying. My problem was I didn't know how wrong what I was doing was so I didn't know bad I actually was doing as it produced some results that on initial inspection looked OK. Once I got pointed in the right direction I saw a rapid improvement in the overall image quality even if the first few attempts didn't turn out all that great.
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