Tag: photography

Different Types of Photo

I’m still struggling to get my big old scope to reproduce some of the behaviour of my smart scope. I won’t bore you with the endless rounds of incompatible software versions, missing drivers, missing star catalogues, multiple connection issues etc. etc. etc. Suffice to say that, after several months of mostly trial and error, everything nearly works. I can control the telescope from inside the house. The computer can compare the stars the camera sees with the stars it ought to see and move the telescope accordingly – a technique called “plate solving”.

My big problem at the moment is that, once the telescope reaches its target it tends to wander off somewhere. The photos from this aren’t very good. This one, of the Dumbbell Nebula is about the best of a bad bunch. Notice that the stars have diffraction spikes on them because this was taken with a reflecting telescope rather than a refractor.

https://en.wikipedia.org/wiki/Dumbbell_Nebula

The smart scope, on the other hand, allows me to explore a wide variety of photographic techniques. This, for example is the Triangulum Galaxy. At 2.7m light years away, it’s part of the Local Group that include the Andromeda Galaxy and the Milky Way. It’s a bit smaller than those two and can fit in a single frame of the smart scope.

The interesting thing about this image is that it was taken over several nights, each with a couple of hours exposure. Astrophotography has its own image file format that stores things like the coordinates and orientation in the sky of the photograph. This allows the images over different nights to be much more easily combined with one another. Notice – no diffraction spikes this time.

https://en.wikipedia.org/wiki/Triangulum_Galaxy

This same storage format also makes it easier to build mosaics of nearby bits of the sky. This picture of the Seven Sisters is actually a composite of two nearby frames. The whole cluster won’t fit in the smart scope’s field of view. But that’s no problem. Just photograph one bit then move the scope a little bit and photograph the next bit. The storage of coordinates makes it easy for software to combine the two.

https://en.wikipedia.org/wiki/Pleiades

I would love to sit up all night watching images appear on the smart scope. Unfortunately I have to sleep sometime. And sometimes the best bit of the sky appears exactly when I want to go to bed. The smart scope comes to the rescue once again. I can tell the scope to wait until a given time, and then spend a specified period photographing a named object. You can even give it a whole list of things, times and exposures, then just go to bed and let it do all the work. This photograph of M15, the Great Globular Cluster in Pegasus, was taken using just this technique.

https://en.wikipedia.org/wiki/Messier_15

I’ve got a very long way to go before I can get my old scope to emulate all these techniques.

All of the above photos were taken this week from my garden in Southend. The first with a Skywatcher Heritage 150p (6 inch reflector) and a ZWO ASI485MC camera. The rest with a Seestar S50 smart scope (2 inch refractor)

Jupiter

Jupiter is beautifully placed in the southern sky at midnight just now, with no moon to spoil the show. You might remember my previous effort to capture it was not a great success. Since then, I’ve picked up a new x2 magnifier for my scope. (Called a “Barlow” in telescope-speak.) I got it for £20 on Ebay, which I consider a bit of a bargain. I’ve no idea if it was responsible for any improvements. There are a myriad of factors that can affect a picture on any one night. But here are the old and the new compared, with the new picture on the right.

jup20Nov28nov

This isn’t what you actually see through the telescope. It’s heavily cropped. The original picture looks more like this. This is a 1/60s exposure at iso 1600.

I don’t normally save “raw” images on the camera. But that night I accidentally had that option switched on, and I’m glad I did. Just a reminder, most images on the web are jpeg type files, or similar. These are compressed images. But the compression algorithm is lossy, it doesn’t preserve all the original information. All the images you see above are based on jpeg originals.

This can work very well for every day pictures in bright light. However, for high magnifications, every bit of detail is important. Raw images save every bit that is captured by the camera. And what a difference it makes. Here they are compared, with the raw image on the right.

As you can see, there’s a lot more detail in the raw compared to the jpeg image. This feeds through the image processing. I took a dozen images in rapid succession and stacked them using my favourite photo processing program, called “Siril”. This is the result (raw on the right).

And here’s that final image close up.

Given the cheap equipment, and basic processing, I’m fairly chuffed with this.

Having said that, Jupiter is by far the easiest planet to photograph. More massive than all the other planets combined, and able to swallow 1,000 earths whole, it presents an easy profile to photograph in the night sky. Mars is tiny in comparison, Saturn is much further away, and Venus is just a featureless, cloudy blob. Initial attempts to photograph them haven’t been an outstanding success so far. I’ll let you know if my efforts improve.

Meanwhile, back in the Andromeda galaxy. No telescope this time, just an old Carl Zeiss lens I found in the cupboard, This was only a brief test, iso 3200 4s x28, so under2 mins total exposure. Based on the result, this might be worth playing with a bit more.

Some Photo Experiments

I’ve been trying out some different things over the last few weeks with my telescope and camera. Mostly I take photos by removing the eyepiece in the telescope and placing the camera there. This is called “Prime Focus” astrophotography. Even there I’ve been trying to push the boundaries a little bit.

Magnification is directly linked to the focal length of the telescope. This isn’t usually the main consideration in astronomy, where the size of the main lens or mirror is usually the principle characteristic. This is what controls its light gathering power and so determines the faintest objects it can see. My scope is relatively compact with quite a low magnification.

However, for planets and the moon, magnification is everything. You might have noticed that I’ve never posted any images of the planets and that’s the reason why. You need to add some extra optics to alter the focal length if you want to do planets with my scope. The result will never be as good as a dedicated instrument, but I can try. Here’s a single 1/200s iso 3200 shot of Jupiter.

jup20nov

That’s fairly typical of what you would actually see through the scope. I was hoping to get a few more over the last few nights, but weather, the moon, and me having to sleep sometime, have conspired to get in the way. To get improved results I need to take lots of images and stack them. This is most easily done by taking a movie. Here’s one of Saturn.

https://mega.nz/file/Ro4C3KTC#qwqi0L2sRXmHwE9wO8tH9om9PxEtq08ujE-g_jqB3DE

Unfortunately, my attempts to stack the frames from this haven’t worked out too well so far.

Increasing the focal length can also be used to get high magnification images of the moon.

This is the Mare Nectaris using this technique.

https://en.wikipedia.org/wiki/Mare_Nectaris

As well as increasing the focal length of the scope, I’ve also been experimenting with just using the camera directly. The problem I’ve always had with this in the past is that you need a really good tripod, with fine adjustments and preferably a motorised mount to track the sky. Expensive. Trying to take photos of the sky on an ordinary tripod has just proved too awkward.

However, I recently figured out a combination of lumps of metal, bolts and clamps that has allowed me to remove my telescope from its mount and put the camera directly in its place.

This has been great fun to use. It allows me to use the app on my phone to point the camera wherever I want and track it fairly accurately. It also lets me play with all the old lenses that are sitting in cupboards in the house. I’ve hardly begun to explore the possibilities here. At the moment I’m mainly using an old Pentax K mount f1.7 50mm lens. This has a field of view of about 15 degrees. perfect for Orion.

And Andromeda.

The way I’ve mounted the camera also allows me to balance it so that it isn’t front heavy. A big problem on a normal photographic tripod. This’ll let me play with some old telephoto lenses that are currently sitting unused. So I might be able to try out some new stuff in the months to come.

Astrophotography Moon Winner

Inspired by this stunning Astrophotography of the Year winner in the moon category, I thought I’d have a go and see what I could do.

moonWinnerSml

https://www.rmg.co.uk/whats-on/astronomy-photographer-year/galleries/our-moon-2024

Unfortunately, my best effort last night didn’t even come close.

4unnamedTubeSml

The winning image is of a small section to the top right of my photo. Still, undeterred, there are a few things I could do to try and improve things.

  1. Better telescope, better camera, better lenses. These all cost money. In some cases, serious amounts of money.
  2. Move to a better climate. This is my favourite solution. There are people who can actually plan what and when they’re going to photograph. They have regular clear skies and low light pollution. In my case, it’s more a matter of waking up at midnight, sticking my head out of the window, and if it’s a clear sky, hurriedly getting dressed and dashing out into the back garden to see what I can capture before the clouds roll in again.
  3. Don’t photograph the full moon. The above photograph has very low contrast because it’s a full moon. The winning photograph was taken when the sun was casting beautiful shadows across the craters and mountains of Sinus Iridium.
  4. Try stacking photos. This was a single image. It might be worth taking a few dozen and try stacking the results. Might be worth a go.

I’ll let you know how I get on.