Astrophotography as a hobby for city dwellers

[donheff]

I found this old thread and wasn't sure if it made sense to resurrect it or start a new one. New one it is.

In the earlier thread I asked about others who were interested in astrophotography. I had a home built 6" Dobsonian telescope my daughter and I built and took some moon and planet photos with it. Last August, I dug it out of the closet and took some more planetary photos, but I found myself limited because I am solely in DC these days. And my interest has evolved to Deep Space Objects (DSO) like nebulas, galaxies and star clusters.

Unfortunately, to image DSOs I would need a few $K in refractor telescopes, cameras, goto tracking mounts, controllers, a new laptop, etc. Worse, I have concluded that with all the gear in the world it won’t happen here with my tiny window into DC’s light polluted skies. And it won’t happen in the infrequent trips to marginally better skies at friends’ houses. You need a lot of time and the right type of “seeing” to capture these beasts. So, you really do need decent skies where you live.

Enter a guy I met online whose family runs Utah Desert Remote Observatories, in the desert just north of the Grand Canyon where I recently experienced stunning dark (Bortle 2) skies. Their primary business is hosting astrophotography equipment for well-heeled enthusiasts who station their scopes out there and run them with remote control (and a little help from their friends onsite). It turns out they will also lease time on a couple of their own telescopes to desperate wannabes like me trapped in the city.

The first photo, Andromeda, is the result of "my" first remote data capture. Well, sort of mine. I own the image data but could not get it on my own. What I got was a few gigabytes of my remotely gathered images plus a lot of other data to use in processing. The result that you see below is my first effort with lots of fine tuning to come. I used SiRiL, an open source astrophotography program to stack and stretch the image and Gimp for some final edits.

The second photo is a copy of the single “image” that you get after stacking all the photos you took in your time using the telescope (open it, you can just see the galaxy core). Your task, should you choose to accept it, is to tease the galaxy you see above out of the dark. For those of you who process your regular photographs, you have probably seen a histogram that charts how the RGB data is mapped across your viewing space. If space is wasted, you tweak your photo to get it in balance by spreading the histogram out a bit. Well, in astrophotography, the data is all packed into a steep peak at the left, so narrow that you can’t really see it. You have to streeetch the histogram out. That’s most of the effort. And luckily, there are sophisticated open-source tools to help.

This was tremendous fun and seems to have resurrected astrophotography as a viable hobby despite my bright city location.

Edit: My tongue and cheek challenge about editing a dark stacked image does not apply to the little jpg I posted here. That one doesn't have enough resolution to get anything out. But, if anyone want to try it, I can post or send a higher resolution file to play with.

 

[JoeWras]

What are the sizes of these images you get?

 

[DrRoy]

I understand that Andromeda is quite large in the sky, larger than the Moon, if it was bright enough to see.

 

[donheff]

What are the sizes of these images you get?

The individual lights were 116 MB each. 19 were 5 minute RGB exposures through a neutral luminosity filter. Seven were 10 minute narrowband HA and OIII exposures thru an Optolong L-eNHance filter. I stacked and stretched the narrowband data separately and added it in Gimp as an overlay layer. That addition tinted the output a bit green but SiRiL has a nice remove green noise tool that fixed that. I have a lot to learn about processing. This image used a SiRiL auto stretch function but that can be fine tuned manually. I also used Starnet to separate the galaxy and the stars and processed them separately. SiRiL integrates Starnet in it's process if you want to use it.

Studying other peoples' work online, I expected to need a lot more hours on the telescope to get decent results. But this is a high end scope and camera in a Bortle 2 sky. The scope is a Takahashi FSQ106 and the camera is a ZWO ASI6200MC Pro.

Edit: I forgot to add, that I also downloaded a stack of darks, flats, and bias frames that add up to a lot more than the lights. I will be able to use that data for other images thru the same scope and camera.

 

[donheff]

I understand that Andromeda is quite large in the sky, larger than the Moon, if it was bright enough to see.

Yes, it is huge. In a dark sky you can just make it out visually, IIRC. Through a telescope (I have observed it through my Dob), like all these DSOs, it is faint and wispy. There is nowhere in space that you could see these things visually like you see them through stacked images.

 

[JoeWras]

donheff: I think I need to do some research or learn a new language to understand what you are doing. It is kind of beyond me at this time, but I aspire to understand it some day.

 

[donheff]

donheff: I think I need to do some research or learn a new language to understand what you are doing. It is kind of beyond me at this time, but I aspire to understand it some day.

It is intimidating at first but the basics of processing are fairly simple. The fine tuning is a bit of an art and never gets perfect. The same thing with gear. If I had decent skies where I live, I would go down an expensive rabbit hole with telescopes, cameras, and mounts.

But, keep in mind, this started for me with a homemade telescope and a $50 quickcam.

 

[RetMD21]

Nice photo. This is fascinating. I know someone in Michigan who does astrophotography of DSO while facing issues of clouds, cold weather, and light pollution. He has some great images but I think it takes him multiple attempts. It had never occurred to me that remote control of the telescope could be done from across the country. I was thinking of from my house to the backyard.

 

[donheff]

Nice photo. This is fascinating. I know someone in Michigan who does astrophotography of DSO while facing issues of clouds, cold weather, and light pollution. He has some great images but I think it takes him multiple attempts. It had never occurred to me that remote control of the telescope could be done from across the country. I was thinking of from my house to the backyard.

If I had slightly better viewing conditions (like I had when I had a weekend house) I would give it a try like your friend. But not only do I have terrible light pollution but I also have a very restricted view of the sky due to trees and adjacent townhouses.

People who buy their own gear (including a headless computer of some sort) and host it out at the Utah site are doing the full remote control (clearly needing some assistance from people out there) like you are talking about in the backyard.

What I am doing is a simpler but less my own end to end achievement. I am working with the owner to setup the session on one of his scopes/cameras. But he kicks off the session and then posts the files on dropbox for me to download. I then handle the stacking and post processing all of which I am particularly interested in.

An outfit called itelescope.com hosts a bunch of telescopes at the site I use (and others around the world). I think they may offer a more direct hands on remote control of their equipment. After I have progressed a bit on the approach I am taking now I may look into theirs.

 

[skyking1]

This topic interests me, I have wanted a good telescope for a while now. I found the https://www.lightpollutionmap.info/ and looked up our new home site and got these values.
Zenith sky brightness info (2015)
SQM 20.68 mag./arc sec2
Brightness 0.578 mcd/m2
Artif. bright. 407 μcd/m2
Ratio 2.38
Bortle class 4
Elevation 91 meters

My current location:

Zenith sky brightness info (2015)
Coordinates
SQM 20.13 mag./arc sec2
Brightness 0.956 mcd/m2
Artif. bright. 785 μcd/m2
Ratio 4.59
Bortle class 5
Elevation 153 meters

Looking better there!
It's about a half hour drive to some Bortle class 2 from there.

 

[RetMD21]

The light pollution map is fascinating. I looked up the Bortle class 1 area around Portal AZ

 

[walkinwood]

I...

Enter a guy I met online whose family runs Utah Desert Remote Observatories, in the desert just north of the Grand Canyon where I recently experienced stunning dark (Bortle 2) skies. Their primary business is hosting astrophotography equipment for well-heeled enthusiasts who station their scopes out there and run them with remote control (and a little help from their friends onsite). It turns out they will also lease time on a couple of their own telescopes to desperate wannabes like me trapped in the city.

A wonderful idea and service. Another thing that the internet enables.


It isn't like you can "see" these images even if you were there in person, though seeing a night sky in the high Utah desert (or other dark spot) is something everyone should experience.

 

[mystang52]

Great picture. I took my 6" scope to my Astronomy Club's dark site and was mesmerized when I saw Andromeda. Yes, it was a mere fuzzy white ball, but knowing what I was looking at, and how freakin' far away it is, had me captivated. And the more I stared at it, the more detail I was able to make out.

 

[donheff]

Here is my second deep space object.

The Pinwheel Galaxy (M101) is a spiral galaxy 21 million light years away from earth. It's visible through binoculars a bit above the handle of the big dipper if your skies are dark enough to see. I chose it as my second DSO to image because a supernova exploded into view in May and who knows how long it will be visible. The supernova known as SN2023ixf was discovered on May 19 by Koichi Itagaki, an amatuer astronomer in Japan. It's the closest SN to earth in a decade and exploded when a super giant star collapsed. To our eyes it just popped into view but the light has been on its way here for 21 million years.

The image below is my first crude effort to process 5 five and a half hours of data from 68 5 minute monochrome exposures using red, green, blue, luminosity, and hydrogen filters to capture different colors in the galaxy. As I learn how to do this I expect to be able to bring out more details in the spiral arms. The red pointers in the second version point to the SN. The Big Dipper sketch shows where the M101 galaxy is in our sky.

Disclaimer: I didn't take this from my light polluted backyard. I rented time on a nice telescope housed in the Utah desert. This one was a PlanetWave CDK12.5 with an f/8 2541mm focal length. The camera was aa ASI6200 cooled astrophotography camera with a 35mm sensor with 64 megapixels of resolution. The telescope alone goes for about $12K, the equatorial mount was probably $14K and the camera with filters about $6K. In addition, there are automated filter casettes, concrete piers for the mount, a shed with retractible roof, management computers and software, and on and on. If I was doing this myself I would probably invest about $10K for everything. So, even in a darker location like our former river house, I would need to take exposures over many more hours to approach the level of detail. In DC, forget about it.

 

[jimbee]

Donheff, your imaging looks great!

 

[homestead]

Donheff, your imaging looks great!

+1
I appreciate the effort that went into getting those images.

 

[skyking1]

I read about all that work you do to stack and filter the images. I too would need a guidebook.
Thanks Don.

 

[audreyh1]

So cool!

Did you go to Utah? Or is this kind of setup somehow available remotely?

 

[donheff]

I read about all that work you do to stack and filter the images. I too would need a guidebook.
Thanks Don.

There is a bit of a learning curve but once you get the basic idea it can go pretty quick, The software does all the heavy lifting. With the long (5-10 min), and very clean, exposures I get from the desert location I do not have to deal with a huge number of frames and do not need to inspect them before stacking. If I was doing this with my own telescope in a semi rural location like my former river house with decent but not truly dark skies, I would probably stay at 1 minute exposures and would need more total time. If I doubled the time I would end up with about 10 times the number of frames to stack. I would also have to instruct the software to improve the stack by discarding a certain percentage of worst frames (in which case the process would take a lot longer but would still be automatic). Or, if I was a perfectionist, I could inspect the frames (the software allows you to view a rough version of what the data in each frame will look like when stretched so you can individually weed out blurry frames, satellites or planes coming through, etc). That can take a long time.

The fun part is stretching out the histogram of the single combined (stacked) image (color) or set of images (mono) to disclose the details hidden in the dark. The tools are incredible and the processes are fascinating.

I have also discovered that there are camps centered on different approaches. But that is a complicated topic. I am struggling with whether to cross camps by tackling a new software package with a reportedly steep learning curve due to it's different object oriented, math based approach to image development. The engineers here would love this one.

 

[aja8888]

Don, very cool work! This is so fascinating!

 

[GalaxyBoy]

The last time I did astrophotography was with hypersensitized Kodak Tech Pan 2415 film using a 10" scope. Guiding was manual using an off-axis guider and keeping an anonymous stair centered on a crosshair for 30 minutes at a time. Then you crossed your fingers the shot came out and the kid at the photo store would actually print what looked at first glance to be an unexposed frame.

Eventually I called it quits. In those days, shooting galaxies was like hitting yourself with a hammer - it felt good to stop!

These days, shots like yours rival the best images taken 30 years ago and put on the cover of Sky and Telescope magazine. Kudos!