This blog entry is to report on my first real successes chasing deep sky images with my Hestia (a.k.a. Canis Minor) last night. I’m far from expert, but I now know more than I did the previous time I went out.
I’m going to issue a disclaimer at the outset. I really don’t intend this to be a carefully wrought training discussion. I wanted to just post what I’m learning so others might benefit. I will also admit that I’m a PhD astrophysicist, so I do bring a scientist’s obsession with actually enjoying mundane data collecting tasks, like being obsessed with focusing and calibrating. You have to be able to focus Hestia with some facility. If it’s not focused to deliver reasonably sharp stars, then you won’t be able to find anything at night. (I won’t say anything more about how to focus, because the Gravity app will lead you through that process. If you’re new to the device you need to make sure the films are off the lenses and you need to practice.)
My years in the planetarium field have also made me intuitively aware of where constellations are in the sky, even when I can only see a few landmark bright stars. All the observations were done in a Bortle 9 park nearby, actually sitting in left field of a baseball diamond.
I will also assume that Hestia users are getting used to managing the little tripod. I think it’s fine for what Hestia was designed to do. But, we all need to know how to manage it in the dark deftly so we can loosen and tighten the bearings easily without causing the thing to go way off target. I’m finding it takes some sensitivity. I also am trying hard not banging into the tripod legs with my big feet. I’m sure some people will put Hestia on better tripods, but what I’m showing here does not require anything beyond standard equipment.
I also want to mention up front that it’s important to adjust our expectations too. Hestia does quite well with the Sun and Moon, but that’s it’s prime use, I feel. This is not a sophisticated device that will ever take amazing long exposure images of deep sky objects. It has a tiny aperture and its rudimentary mounting, which has to stay fixed during image stacking, can only remain on target for about a minute. So, it will be limited at getting deep sky objects. Nevertheless, I’m kind of impressed.
None of the images below were post processed. I’m just attaching what Hestia/Gravity delivered to my phone. I’m also not including the almost equal number I shot where I didn’t have the object centered properly.
I should add here that I've just been told that the Gravity app's Deep Sky mode is not compatible with certain Android phones. I use an iPhone 15 Pro Max and was running iOS 17.3 for what you will see here. Vaonis recently posted a description of Hestia Phone Compatibles. Check it out.
Background on How I Believe the Gravity App Works
Understanding what the app is doing is essential for the deep sky objects. IMHO Hestia is about 50% hardware and 50% the Gravity software. It’s not simply directing light onto your phone’s camera lens. It’s managing the images that come through the lens and both orienting the device as well as doing rudimentary processing.
We can only tell it to go to a particular star or nebula if it knows where it is pointing in the first place. It has data on the celestial coordinates for the objects, but it still needs to make a benchmark of where it’s looking at any given time. It does this by examining the star field and trying to match star pattern it sees with a data base in the app. This is called “plate solving.” If you go into the night time mode it will continually try to figure out where it’s pointing. It will tell you on the phone screen if it has failed or is succesful. Only when this has succeeded can you hope to find your object.
I live with pretty bright skies, so it can be tough at time to find enough stars to plate solve. I suspect that those of you who live in darker skies will have a much easier time with orientation. The sky will be worse at lower elevation too, since there’s more light pollution there. I had a devil of a time with M31 as you’ll see below.
Once you do find your object and lock on it, it will drift, of course, because the Earth -- with you and your Hestia -- is rotating. This means that when you do direct the app to make an image it will only have a couple minutes at best to snap some frames to expose. I think it stacks about twenty or thirty relatively short exposures.
It can’t do longer individual exposures because then the stars would streak. On one of my images below — Aldebaran — you can see that a frame that jostled found its way into the stack. In addition, the app also will throw out frames where Hestia shook or something trailed. That’s actually a good feature too, but I’m not sure it’s perfected yet.
As with all Alt/Az mountings Hestia will be seriously challenged (see my blog entry on this topic) at high altitudes from the horizon — near the zenith. I’d stay away from there also because I’d be afraid the phone would fall out.
My Results
Once I got set up on the baseball field I managed to shoot the following six objects within about an hour. I consider that a fast amount of time. Not all objects took the same amount of effort. My notes about each are below the pictures.
Aldebaran (Alpha Tauri)
I started with Aldebaran because it is bright and would allow me to keep fiddling with focusing. (I love to focus.) It took a while because I was just getting started and was fumbling with the controls. I had to stop a couple times trying to find it so the plate solving could do its thing. You’ll also notice a streak through the star. This is, I believe, because the app didn’t catch a frame where Hestia was bumped or buffeted. Usually it catches these frames and keeps trying.
M45 (Pleiades)
This cluster fits the field of view nicely. I shot a couple more and this is the most centered. I’m not sure I couldn’t have focused better, but otherwise I’m happy. I think there is a streaked frame in the stack too.
M31 (Andromeda Galaxy)
I knew this one would be a “reach” for me because it was pretty low in the sky and the light pollution was bad. This made plate solving challenging for the Gravity app. I persisted after a few failed attempts and kept my faith that the plate solving would finally get me on track. Here are the three previous failures. When I was finally on target, it could be seen faintly before the stacking. I was actually thrilled in the end I got to image the nucleus of the galaxy.
M31 Failures (#2 was way off.)
Double Cluster in Perseus (NGC884/869)
I was pretty pleased with this, though I went through a few attempts at imaging even when I knew I was in the right place. Luckily, this was easy and quick.
M42 (Orion Nebula)
I wasn’t planning on imaging this last night, but I couldn’t resist. Again, I had to start and stop a couple of times before zoning in so that the app could do the plate solving. I switched to square format too. Not sure my focus shouldn’t have been revisited, but it was getting late.
Jupiter — First Try
One of my main goals fo the evening was to try the planet mode. The image location went the same as before, but Jupiter is so bright it became quite clear when it was in my sights. I’ve learned that the planet mode basically takes one shot when Gravity thinks the image is still. I then saw that there was maybe too much light.
So, for the second shot, I tried to fiddle with the camera controls like exposure length and ISO numbers. Not sure what follows is as good as I could do, but it was a start and looks better than the previous. Little Canis Minor probably will not return cloud details on the planet.
Jupiter — Second Try
New Tips and Tricks
My first tip involves the image above. I put tape where I’ve found the magnets are when my phone is in the correct position. This really helped speed the set up. You might also notice that I had to tape my little rubber lens coupling back into place. I pulled mine out removing the plastic lens protector and can’t for the life of me get it to fit back on and stay. But, gaffer’s tape has worked well.
Make sure you have some decently focused stars before you go nebula hunting. The plate solving won’t work at all if Hestia is out of focus.
The new bag of tricks I’m going to need to perfect is learning how the plate solving works in practice. I found that if I was patient and pointed it to a place where it could see some stars it would work. Then if I moved where it said the object was and it wasn’t, then I waited for it to plate solve again and got closer if not right on target. Iterating seemed to work for me. I can believe that this is necessary because I can believe the small, unleveled mounting is not accurate over large angular distances. One of my next experiments will be to carefully level the tripod first and to have it on solid ground.
Be prepared to shoot the same object a few times. I continually found myself not being totally satisfied with my positioning after the first one or two stacking.
I don’t advise demonstrating this type of imaging to guests, especially if you’re unpracticed or if you swear. It will just make it seem like a blacker art than it already is.
Right now I think we’re limited to the objects given to use in Gravity. That’s fine. I know they will expand the list in time. As is typical, clusters will look the best.
Be prepared to have to experiment with some of the other exposure controls, especially for planets.
I haven’t tried the Moon yet, so I have no advice for it ... yet.
Summary and Reality Check
The most important take away from my last night’s observing is that indeed Hestia can return images of bright deep sky objects. It takes patience and practice, but ultimately it will be possible.
One should also always keep reality in mind with this thing. It’s not like my other imaging devices. I consider it novel and even fun, but if I really want to get a great deep sky object I would never use it. For the eclipse it should deliver excellent partial phase solar images.
Good luck and I wish you dark, clear skies.
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