Imaging without an equatorial mount?

[Axeldude]

Hi!

I've got a question: as the topic says, is it possible to do deepsky imaging without an equatorial mount? I thought I saw a thread somewhere on the internet but I can't seem to find it anymore, it involved high ISO and about 4" exposure.. could someone enlighten me please?

I've got an 6" (150 mm) dobson

Thanks!

[freeflyjay]

I`ve experiemented a little with my 10" dob, with little success, can only go 1 or 2 seconds then you start to get star trails, it`s not really long enough to gather enough light, most imagers are using between 30 secs and 10 minuits, or though an equatorial platform might be usable, i`ve been thinging of getting one myself but they are quite expensive, so if you wanted to do astro photography properly you`ll really need to get a motorized equitorial mount.

[Digz]

I think you'll find DSO work without a GEM mont is very difficult - not impossible but don't expect wonders. If your really interested in trying AP grab a copy of making every photon count.

[DirkSteele]

Unfortunately even using a tracking Alt Az GoTo mount does not really open up the scope the world of astrophotography. Because the Alt Az is not polar aligned, it will be tracking the sky using 2 axis of movement rather than just one. The effect of this is to cause field rotation - everything in your image will appear to rotate around a central point which will cause blurring of the image. I do use my Alt Az mounted C11 with my Watec video camera which allows up to a 10 second integrated image to form before being shown on a TV screen. Over such short exposures, the field rotation does not manifest enough to be objectionable, but for exposures of the length required for DSO astrophotography it will.

[Ganymede12]

I have a question on a similar line.

Can DSLR cameras take single shots and how good would the shot be? Better than a digital camera held up afocaly?

[Axeldude]

Hmm alright, might have to get a mount when I've got the funds to spare..

Thanks for the info!

[Digz]

I have a question on a similar line.

Can DSLR cameras take single shots and how good would the shot be? Better than a digital camera held up afocaly?

Not quite sure I understand what your asking? Of course a DSLR will take a single shot, but if it's not on a tracking mount you will be limited in exposure length unless you want to shoot star trails. The are, of course, othe factors with DSLRs that come into play.

[Ganymede12]

Basically, can I use a DSLR like a digital camera but with a better image.

[Digz]

I assume you are comparing a DSLR to a compact digital camera?

The simple answer is yes. Have a look through the imagining section of the forum and see what people use.

[freeflyjay]

you can of course take perfectly good moon pictures on a dob, my profile pic is a compact camera single exposure shot a focally hand held, and this was my first attempt 2 days after getting my scope so as you can guess not exactly hard.

[Digz]

you can of course take perfectly good moon pictures on a dob, my profile pic is a compact camera single exposure shot a focally hand held, and this was my first attempt 2 days after getting my scope so as you can guess not exactly hard.

Correct but the OP was talking about DSOs

[Zakalwe]

Basically, can I use a DSLR like a digital camera but with a better image.

A DSLR IS a digital camera.

[Ganymede12]

Let me phrase it differently

My digital camera can't see DSO's but could a single shot DSLR image see DSO's?

[Digz]

Let me phrase it differently

My digital camera can't see DSO's but could a single shot DSLR image see DSO's?

Not really, your question is rather simplistic and other factors will come into play to determine what will be picked up:

Seeing

Focal length

Aperture

ISO

Sensor pixel size

etc etc to name a few.....

[Ganymede12]

Lets say I was at a dark sky sight with a Skyliner 200P dob and very good seeing. Would it be at all possible?

P.S Sorry for hijacking the thread!

[RikM]

Lets say I was at a dark sky sight with a Skyliner 200P dob and very good seeing. Would it be at all possible?

P.S Sorry for hijacking the thread!

Short answer is No.

DSLR's generally have a bigger chip and better control of noise at high ISO than a compact but that is only really useful for astronomy when you can take long exposures. A second or two won't make any practical difference. The DSLR will be better but it still won't be any good. If you want to image DSO's—and be able to recognise the object in the image—you need at least tracking and it is very much better with an equatorial mount.

[Ganymede12]

Ok thanks.

[Zakalwe]

Short answer is No.

DSLR's generally have a bigger chip and better control of noise at high ISO than a compact but that is only really useful for astronomy when you can take long exposures. A second or two won't make any practical difference. The DSLR will be better but it still won't be any good. If you want to image DSO's—and be able to recognise the object in the image—you need at least tracking and it is very much better with an equatorial mount.

It'd be possible. There was a guy on Flickr with an album full of DSOs taken with hundreds of short exposures. He used IIRC, a Canon L lens (so it'd be fast....maybe f2.8) and a standard photographic tripod. Exposure times were only a few seconds long, and he was re-framing by hand.

There was a lot of noise in the images though. He almost certainly would have gotten better results by selling his fancy 500mm f28 and buying an HEQ5, an ED80 and a T-Ring.

Pretty much anything is possible. Heck, it'd be possible to go to work on a pogo stick if you wanted to. It's just that there are far easier, cheaper and more effective was of doing things.

[dph1nm]

At zero declination the sky moves 15 arcseconds per second. I would guess that a typical DSLR on a 6" dob (depends on the focal length) has around 2" pixels, so basically you are going to struggle without any form of tracking (that is not to say it is impossible - in principle you could stack lots of 1/10s subs, but you would suffer badly from read noise in the camera, meaning you would have to acquire a much longer total exposure time than normally would be the case). Not as bad as you get to higher declinations of course, although field rotation will limit you even at the pole.

If you have alt-az tracking then you can happily do most Messier DSOs by limiting your self to 30s-1min exposures (although you might still have issue with tracking errors caused by the mount, of course!).

NigelM