Astrophotography tips

Beta Ray Bill

Hi

I'm using an old camera (Sony SLT A55v)

I'm connecting the camera to a meade 7.5 inch refractor telescope

The pic of the Moon are "ok" but when I take a picture of Jupitar and it's moons all I get is bright dot and 4 red dots.

I don't its exposure, I think the target it to bright against a dark back ground (Is this called over saturation?)

Pics below, any tips on what config changes I should make to fix up the pics?

G.

DaireQuinlan

They're overexposed. I assume you're just using whatever auto mode the camera has ? You should be in manual mode, stopped down a bit, and choose a shutter speed that results in a properly exposed gas giant. Caveat: I've never down astrophotography so I'm sure I'm missing some nuances, but basic exposure is the same.

Probably not a huge problem for planets and moons and what not, but the camera might not be ideal for general astrophotography. It's an SLT camera, which means it has a permanently fixed translucent mirror, so you're losing x% of the light all the time.

Beta Ray Bill

https://www.boards.ie/discussion/comment/121427621#Comment_121427621

I'll give this a bash.

Gregor Samsa

As Daire said above, the Jupiter shot is over-exposed. Astrophotography absolutely has to be done in manual mode, and don't worry about what the camera's light meter says, because as you alluded to, most of the frame is pitch black with a very small but very bright subject.

How are you interfacing the camera and the telescope? If you're connecting your camera directly to the telescope (basically using the telescope as the lens), then you won't be able to stop down the aperture in the normal way of just adjusting the aperture setting in the camera (you'd have to use use an aperture mask on the end of the telescope, but it's a very different process to changing the aperture on a regular lens).

Jupiter is very bright, so to get detail, you'll have to up your shutter speed. Start with about 1/20s and see if you get any more detail on the planet itself. However, you won't get the Jovian moons at this speed. For the moons, you'll need a slower shutter speed - about 1 second (although if you don't have a tracking mount on your scope, this may be too long). Then you'd combine the two photos. Try ISO 800 for the shots.

If you want to try Saturn, it's not as bright, so try 1/5s for it.

For deep space objects (the Andromeda galaxy, for instance), you'd be shooting at 30 seconds per shot (and taking maybe 60 of those). And you'd need a tracking mount for long exposures like that.

Also, as Daire mentioned, the fact that the A55 is an SLT means it's losing a 1/3d of a stop of light to the translucency mirror. It's not ideal for deep space astro (nebulae and galaxies, where all the light you can get counts), but not as critical for planets, and you should still be able to get better shots than you are now with a bit of tweaking and patience.

If you want to get more detail, you really need to stack multiple photos rather than rely on a single image. This allows you to cancel out the random noise in each image, and bring out the details. Stacking can get quite complicated (not to mention time consuming, as you can be taking hundreds of photos to stack), but the article below talks about some simple stacking using just 4 frames.

http://soggyastronomer.com/how-to-photograph-the-gas-giants-jupiter-and-saturn/

Also, post-processing is really important in astrophotography - don't expect things to come out perfect in camera. It just can't happen, no matter what setting you use. You will need to tweak in Photoshop/GIMP/whatever.

Beta Ray Bill

https://www.boards.ie/discussion/comment/121428050#Comment_121428050

How are you interfacing the camera and the telescope? If you're connecting your camera directly to the telescope (basically using the telescope as the lens), then you won't be able to stop down the aperture in the normal way of just adjusting the aperture setting in the camera (you'd have to use use an aperture mask on the end of the telescope, but it's a very different process to changing the aperture on a regular lens).

yes direct connection. I have an aperture mask for the end of the telescope but its just one size (not adjustable)

I'll use it next time and give the high shutter speed a blast.

I've no experience doing post image processing, I'll try get the raw picture first and check cleaning them up after.

The Telescope is on a LX85 mount which I believe follows a target.

Also I've noticed I need a clicker that's connected to camera via a wire as opposed to pressing the button as even the slightest touch wobbles the telescope enough to blur the pic (especially for long exposure)

Gregor Samsa

https://www.boards.ie/discussion/comment/121428176#Comment_121428176

The aperture mask that came with the telescope is probably good for the Moon, but might be too much for Jupiter. But give it a go. You'll instantly know if you're cutting out too much light.

You're all set with the LX85 mount - it's perfect for back-garden astrophotography of any kind.

DaireQuinlan

Great additional info from Gregor Samsa, if there was one other thing I'd add is that neither your moon pic nor your jupiter pic seems focused correctly to infinity, I assume the Jovian moons ought to be little dots for example. Again, no experience shooting astrophotography so maybe Gregor Samsa could suggest how best to ensure you're focused correctly.

Beta Ray Bill

https://www.boards.ie/discussion/comment/121428791#Comment_121428791

Here in lies the dilemma

The Telescope has a manual focus. It's not very good for ultra fine focusing. and its even harder through the eye piece of a camera.

I think this is going to be a trial and error type thing

bullpost

https://www.boards.ie/discussion/comment/121428176#Comment_121428176

You might be able to use the camera self-timer instead of clicker

Gregor Samsa

https://www.boards.ie/discussion/comment/121428980#Comment_121428980

There's a thing called a Bahtinov Mask that makes focusing very easy. It's basically a plastic or aluminium grid that goes over the aperture of the telescope, and when you look though the viewfinder (or your camera), bright stars are seen to have six spikes coming out of them. You adjust focus until the spikes line up correctly, then you can point the scope at whatever you want. You should be able to find one to fit your scope. Otherwise, go with trial and error - it can be hard to get it right, especially looking through the camera. Take a shot, view it on the back screen zoomed in, and then make adjustments as necessary.

Beta Ray Bill

Lads/Lass's this all class advice

Thank you 😁

Gregor Samsa

Clear night last night, so I gave Jupiter a go. I do have a telescope, but it's packed away, so I used my Sony 200-600 @600mm with the Sony A1. Took 10 shots (on a regular tripod, not tracked), 1/640s, f6.3 ISO 1000, cropped them significantly, then manually aligned them in Photoshop. I then exported each aligned layer as a separate image, and stacked those in Starry Sky Stacker. Then I spent far too long processing it in Photoshop. Not a great image, but at least you can see the bands and a hint of the Great Red Spot. The moons visible are Ganymede Europa, and Callisto. If I had waited about an hour, Io would have been visible too, but it's obscured by Jupiter in the photo. You'd really want to take a separate set of photos with a different exposure for the moons, and combine it with the planet one, but I didn't do that.

Tried something new with the Moon too. The A1 can do "Pixel Shift Multi Shooting", where it can take a burst of 16 photos, but it moves the sensor by half a pixel in each direction for each shot. Then you can combine the 16 photos in software to create a 100 megapixel image (the A1 is 50 megapixels).

Up until recently, you could only do it on static scenes - perfectly still landscapes shot on a tripod. But a recent update allows it to use image stabilisation data from the sensor to combine moving images. So I decided to try it with the Moon - which was moving across the sky. So this is 16 shots combined to double the sensor's resolution (not stacked like the Jupiter image), each take at 600mm, 1/250s, f6.3 ISO 500. Even with the 600mm, this is a heavy crop (and Boards resizes it to 1084 pixels)