Is Astrophotography Without Tracking Possible? (2022) • Hacker News Board

Re: Is Astrophotography Without Tracking Possible? (2022)

#21

Post by shmerl » Sun, May 25, 2025, 5:57 PM UTC

calmbell wrote: post #18

shmerl wrote: post #16

Earlier quoted context omitted.

I guess it would need some experimenting. I was thinking of getting something like Apertura AD8 for visual observation, but I was wondering if photography with it is feasible.

Don't buy a dob to do untracked astrophotography. It will be hard, and you will be disappointed with the results. I would pick between visual observation and astrophotography. They are almost separate hobbies that require separate kits. Get the Apertura AD8 for visual or a smart telescope like the Seestar S50 or S30 for astrophotography. The dob would provide great views of the Moon, Saturn, Jupiter, and decent views…

I mostly want it for visual observation, but if photography with it is possible - then why not try it. It's not the primary goal.

Re: Is Astrophotography Without Tracking Possible? (2022)

#22

Post by labcomputer » Sun, May 25, 2025, 6:21 PM UTC

JPLeRouzic wrote: post #17

cconstantine wrote: post #8

Earlier quoted context omitted.

The problem is that the noise can swamp the signal. Another example of this would be doing astrophotography during the day. The sun doesn't block anything, it just makes the sky glow with "noise". Theoretically it has exactly as much signal from space as it does at night, but because the sun adds so much noise it's completely lost.

> " because the sun adds so much noise it's completely lost. " Do you mean that it would be conceptually possible to image planets or even deep-sky objects during the day with incredibly efficient denoising software? (I am a noob in astronomy)

I would be, yes. As early as the 1950’s, several avionics companies made daylight-capable star trackers (for jam-resistant long-distance airplane navigation) using chopper techniques. Those trackers were mostly mechanical, except for electronics to demodulate the star signal from the single pixel sensor.

Re: Is Astrophotography Without Tracking Possible? (2022)

#23

Post by labcomputer » Sun, May 25, 2025, 6:26 PM UTC

dreamcompiler wrote: post #15

shmerl wrote: post #14

What about using a reflector telescope like a Dobsonian? Would it be able to capture more light lowering the requirement for exposure time?

The conventional wisdom is "Dobbies are not designed for photography" but that assumes tracking is necessary for photography. I'd expect that for untracked photography a Dobbie would work fine provided you could lock it down in alt/az and the whole assembly was robust enough not to vibrate for a few seconds. That might be a tall order.

That conventional wisdom is because a Dobsonian is a Newtonian telescope on an altaz mount.

The altaz mount, not lack of tracking, is what makes it difficult for conventional astrophotography because the image rotates as you track the star. That prevents using a single long exposure. Equatorial mounts keep the image stationary.

Re: Is Astrophotography Without Tracking Possible? (2022)

#24

Post by shmerl » Sun, May 25, 2025, 7:16 PM UTC

labcomputer wrote: post #23

dreamcompiler wrote: post #15

Earlier quoted context omitted.

The conventional wisdom is "Dobbies are not designed for photography" but that assumes tracking is necessary for photography. I'd expect that for untracked photography a Dobbie would work fine provided you could lock it down in alt/az and the whole assembly was robust enough not to vibrate for a few seconds. That might be a tall order.

That conventional wisdom is because a Dobsonian is a Newtonian telescope on an altaz mount. The altaz mount, not lack of tracking, is what makes it difficult for conventional astrophotography because the image rotates as you track the star. That prevents using a single long exposure. Equatorial mounts keep the image stationary.

What about short exposure which is the point of the above post?

Re: Is Astrophotography Without Tracking Possible? (2022)

#25

Post by astroimagery » Sun, May 25, 2025, 9:05 PM UTC

I also don't agree that deep sky astro is losing its appeal and that is indeed what I am interested in. I think that each astrophotgrapher has his own style which is totally unique and if you check some of my image then you'll see what I mean. https://astroimagery.com/astrophotography-deep-sky-images/

Re: Is Astrophotography Without Tracking Possible? (2022)

#26

Post by dreamcompiler » Thu, May 29, 2025, 2:57 PM UTC

labcomputer wrote: post #23

dreamcompiler wrote: post #15

Earlier quoted context omitted.

The conventional wisdom is "Dobbies are not designed for photography" but that assumes tracking is necessary for photography. I'd expect that for untracked photography a Dobbie would work fine provided you could lock it down in alt/az and the whole assembly was robust enough not to vibrate for a few seconds. That might be a tall order.

That conventional wisdom is because a Dobsonian is a Newtonian telescope on an altaz mount. The altaz mount, not lack of tracking, is what makes it difficult for conventional astrophotography because the image rotates as you track the star. That prevents using a single long exposure. Equatorial mounts keep the image stationary.

That was my point.

1. Long exposures require tracking.

2. Dobbies can't track because they have altaz mounts [0].

3. But short exposures don't require tracking. Therefore a Dobbie might work for short exposures iff you can lock down the altaz axes and sufficiently reduce vibration.

[0] It is possible -- and fairly common -- to track with altaz mounts. Both axes require coordinated, computer-controlled stepper motors. In addition you need a third motor to rotate the tube. This was not possible before digitally-controlled motors. So some Dobbies do track but that kind of defeats the purpose of a Dobbie as a cheap light bucket anybody can afford.

In contrast tracking with an equatorial mount only needs a single motor and that motor doesn't need to be digitally-controlled.