Quasar hunting in amateur astrophotography
I'm not sure how big the astrophotography community, if any, is on ~tildes but I'd figure I'd open a topic up and see! Astrophotography is one of my hobbies, and it was brought to my attention (see link for two quasars near the M3 globular cluster) that it's actually pretty easy to photograph quasars. The same are visible in my attempt at photographing M3. Anyway, my question here is does anybody know of any particular interesting or distant quasars to photograph? I assume most will just be "dots" but it still sounds like fun since they're among the most distant objects you can see. I assume most quasars would be broad spectrum, so no filters are really needed, but I'm also curious if there's any bright yet redshifted objects you'd need infrared to capture.
My setup is an Astro-Tech AT80EDT 80mm Refractor f/6. I just got the f/0.8 reducer which I'm excited to take for a spin. It's a chonky piece of glass. My camera is a ZWO ASI585MC which does decent enough for deep sky.
Edit: To add, using something like http://simbad.u-strasbg.fr/simbad/ is great for finding interesting objects once I've already taken a photo, but it's less helpful to plan my shots.
I don't do astrophotography (other than cell phone photos) but I'm curious. I've thought about taking pictures of galaxies, though I understand you need a long exposure or lots of stacked frames. What would be a beginner-friendly way to get started?
Astrophotography is a deep rabbit hole and the learning curve can be as steep as the money pit is deep. However, with that said, there's some relatively inexpensive ways to get into astrophotography with stuff you might already have laying around the house. Smartphone cameras, as good as they're getting these days, are finicky because the app software often doesn't give you good control over shutter speed, taking lots of exposures, etc... I have done it with a smartphone mounted to a telescope eyepiece, but it's pretty hard.
But anyway: I'd start with a mirrorless DSLR camera and a tripod. With a basic DSLR camera and a camera tripod, you can already take pictures of many large objects (such as: The Milky Way, the Moon, Orion Nebula, Andromeda Galaxy, etc...) without a telescope or even tracking. If you really get into it, you can then move towards things like a proper mount (German equatorial with tracking) and a telescope. A DSLR can also be mounted to most telescopes without much trouble with an adapter.
I'll reply later with a little more info on this since it's rather complicated and opaque at first glance but isn't actually so bad. A lot of the astronomy software (DeepSkyStacker, AutoStakkert, Siril) is also free.
So, a little word on that. There's a whole family of techniques depending on what kind of target you're shooting. The only time you wouldn't stack is if the object is incredibly bright (the Moon) or you're doing very long exposures (e.g. like 5 minutes). Even then stacking of some kind is usually useful. There's also no 100% must use technique. Lots of people mix and match strategies or even do "suboptimal" things because of their equipment or for the challenge.
If you're shooting deep sky objects, there's two general philosophies which depend on your equipment. For free software, either Siril or DeepSkyStacker can do this (and plenty of others):
MANY short exposure images you stack together. Think like taking 1 second exposures, but 1,000 of them. This technique is useful if you don't have motorized tracking from your mount since the short exposures negate the Earth's rotation. This technique also can help if you have very poor seeing conditions (thus a fuzzy twinkling sky). You would generally use this style of image capture with say a normal DSLR on a fixed tripod where you're photographing a wide image. Some people also use this with telescopes on small targets like galaxies.
Fewer (but still in the hundreds) of longer exposure images. Think 2-3 minutes. This requires you have a motorized mount with tracking unless you're aiming to make star trails. This is probably the bread-and-butter technique for anybody shooting galaxies or nebula. As a rule of thumb, your motorized mount (I have a SkyWatcher HEQ5) should be more expensive than either your telescope or your camera. Weight becomes a big deal here as well as you want your mount to be rock-steady.
Thanks!
It sounds like shorter exposures is easier in general, as long as you have software to deal with all the images. What advantages to people get from moving from 1 second to 2-3 minute exposures?
That's great image of the Moon.
Here's a detailed video that runs down how to start astrophotography with just a DSLR camera, a tripod, and an intervalometer (which might be built in your camera anyway): https://youtu.be/iuMZG-SyDCU
It's lengthy but goes over all the little nitty gritty details.
The main benefit if storage space and stacking time. Stacking can be a computationally intensive process. So, consider you want 4 hours of "integration time" (aka total exposure across all images). If you do 2 second exposures (easily done as untracked) you need 7,200 photos. If you instead do 2 minute exposures, you only need 120 photos. The former will take a much longer time to process and be unwieldy to work with especially if you do a lot of processes prior to stacking.
Additionally, and this matters more for fainter targets, you have to deal with read noise in the camera which effects your "signal-to-noise ration" (SNR). Taking lots of short exposures means any given image has predominately more noise than intended signal while say even taking a 10-20 second exposure might give you primarily signal. This little tidbit depends on your camera and gain, but let's just say we're getting in the weeds here since there's other noise sources to consider.
Anyway, you can spend dozens of hours reading forums (CloudyNights is nice) or just go experimenting or some combination thereof. The latter is much more fun to be honest!
Makes sense. As a casual photographer, waiting four hours for a photo is not something I want to do, so I guess I don't need to worry about this. (That's a long time to wait for a 3D print job, too.)
Maybe I should start with how long I'm willing to wait and work backwards.
Haha. For what it's worth, most people don't baby their telescopes for the entire night. I either (a) do astronomy socially, so a bunch of folks get together, set up gear and chat enjoying the evening or (b) I set everything up and then leave it running overnight and pack up in the morning.