10" dobsonian and astrophotography

[TheEli]

Hey, im thinking of buying a 10" dobsonian, but the one i'm looking at doesnt have any tracking abilities, so will I be unable to take deep space photos with it?

[BertUK]

sorry to say but no you wont,tracking or guiding is required to image dso,s.

[appalachik]

Bert's right... but looking on the bright side, you'll get some wonderful visual astronomy opportunities, to say nothing of the money you'll save on imaging gear and all the stress it'll give you getting it to work.

Dont let me put you off though

Jenna

[RikM]

A 10" Dob is great for visual astronomy but absolutely no chance at all of DSO astrophotography. Even with the swish new tracking dobs it ain't going to happen. Top of the list for deep sky imaging is a beefy equatorial mount.

With a classic Dob you may be able to get some nice afocal snap-shots of the moon and planets just by holding a compact digital camera to the eyepiece. You will need to take loads of pics and most of them will be hopeless but there will be the odd Gem amongst them if you are lucky.

[umadog]

The first thing you need to know is that photography is one hobby and visual observing is another. A scope which is good for the former isn't good for the latter. I'm afraid the beautiful astro-photos you see are hard to get and don't come cheap. The best advice for a beginner is to start as a visual observer (that 10" Dob is more than good enough) and learn the sky. Have some fun, etc. Use the time to learn about imaging and, if you're still up for it, dive in with your eyes open.

Note that even with tracking it'll be hard to take great astro-photos with a Dob. Some of the best photos I've seen have been with a ServoCat/Argonavis controlled Dob: Astrophotographie mit dem Dobson However, the drive and computer alone cost about 2 grand. You'll also need a field de-rotator for even moderately long exposures. The rig won't be able to deal with really long exposures. I have a ServoCat and wouldn't fancy trying to set it up for long-exposure AP. Imaging will always be easier on a dedicated system: a properly mounted imaging refactor and a knowledgeable operator can produce amazing results.

Two inch scope: Imaging with the Astro-Tech 66mm Refractor - Review

Seven inch scope: Astrophotography - 7" Refractor Images

[brantuk]

"The first thing you need to know is that photography is one hobby and visual observing is another. A scope which is good for the former isn't good for the latter."

Extremely good advice and very nicely put

A dob is primarily an "observing" scope.

[Macavity]

Driven (sic?) Dob owners might consider VIDEO astronomy. Short exposure times, software de-rotation. Not HST quality, doubtless, but Hey? If the basic "will" is there, and you don't start off with the premise of impossibility...

[stolenfeather]

That telescope will give you amazing sights with it's light capturing power but the show will remain yours alone since photography is pretty much impossible. I have to say that I have taken some with my 10" but,... it's nothing,.. NOTHING compared to what is seen on this forum!

Isabelle

[TheEli]

Thanks for all the advice guys!!! I could get an 8" one that does track, but as some of you have already said taking pics wont be as good with it than with a scope using an equatorial mount (and apparently the 2 inch difference has a large effect). One last question, would the 10" be hard to use because of it's weight?

Cheers

[dmahon]

Aperture is not important for astrophography. Focal ratio speeds up your image taking and focal length affects magnification.

Dobsonians are no good for long exposure photography, even if they track, as the base is alt-az rather than equatorial so the stars will rotate on the frame during the capture.

The usual advice is to get a small fast refractor (ED80) on a tracking equatorial mount (HEQ5, though you might manage with an EQ5) to begin with.

[dmahon]

Bert's right... but looking on the bright side, you'll get some wonderful visual astronomy opportunities, to say nothing of the money you'll save on imaging gear and all the stress it'll give you getting it to work.

I never understand the advice sometimes given to budding astrophotographers to get a visual scope first - it's like telling someone wanting to start out in photography just to go out and look at things and forget about the camera.

[Macavity]

I sense once a thread has been initially so dominated by a two-choice "either or" (NOT) opinion, there is little hope? <grin> BUT I reiterate a modest (friendly) hope that folk do not dismiss, alt-azimuth tracking, combined with e.g. VIDEO imaging out of hand... As a viable, alternative, *REAL*, possibility for DSO imaging.

[umadog]

Nobody is trying to put off budding photographers. The problem is that many people coming to the hobby want a cheap good for both imaging and photography. However, such a scope doesn't exist. Since these posters generally want both visual and AP, it makes sense to guide them down the cheaper visual path initially. The visual scope will always be useful later: they can peak at other objects whilst their future AP rig is busy doing its stuff.

To the OP: there isn't a great deal of difference between an 8" and a 10" aperture. If you know you want tracking then you're not giving away a whole lot by going with the 8". Macavity is right that video is a real possibility with a tracking Dob, so you could certainly start with that. You'll be getting colour images of DSOs relatively easily. If you can be clearer as your goals then we can offer better advice.

[TheEli]

If i were to buy the 10", is it possible to later on remove the tube from the Dobsobian mount and place it on an equatorial one?

And again thanks for all the help!!!!!

[Space Cowboy]

You can have great success imaging Planets and the Moon with a auto tracking alt/az Dob and cheap webcam i.e spc880/900. The short exposure needed for these objects makes accurate tracking less important. Its a simple setup that is a great way of starting astrophoto work.

[TheEli]

what about DSO's?

[swamp thing]

One last question, would the 10" be hard to use because of it's weight?

I use my 10" Dob as my grab n go scope as do many others.

They're lightweight and very easy to manage.

If i were to buy the 10", is it possible to later on remove the tube from the Dobsobian mount and place it on an equatorial one?

Many people do this for photographic reasons. On a GEM a 10" Newt is nowhere near as portable and user friendly as a Dob.

Regards Steve

[BertUK]

i use a skywatcher 200p reflector on an eq5 mount and a £90 long exposure webcam and have had good pictures of various dso,s and planets.all at a cost of less than £700

[Ptarmigan]

what about DSO's?

I have also been wondering about this and it would seem that DSOs are possible on other cameras ( not just webcams) with a Dob tracking in Az and El.

Dont take my word for it cos I am new to this and not yet got my Dob!! However, for what its worth :--

Depending upon where in the sky your DSO is you can take lots of short exposures to avoid too much field rotation (like a few seconds up to maybe a minute) then stack them. If the DSO is in the east or west then the exposure can be longer than if it is to the north or south.

Have a look at Gary Honis site HERE and look for his DSOs taken with his big 20" Starmaster GOTO Dob. For example this one ngc891

Charts showing typical exposure times for a small sensor are HEREand a pdf is HERE.

The maths is in there as well to calculate times for larger sensors, but I guess trial and error might be easier !

hth,

Malcolm.

[Macavity]

Standard webcams have a sensitivity measured in a few (one) Lux. Some e.g. "Planetary" Webcams struggle to display fainter naked eye stars in real time. On the other hand, Low Light level VIDEO cameras have a sensitivity 0.00002 lux. Coupled with (say) an 8-10" Dobsonian, you can display 16th magnitude stars on a screen in REAL time. (Galaxies approach a surface brightness of +12?). If you can see it, you can image it.

You can find out more here: http://stargazerslounge.com/groups/video-astronomy.html

Of course, VIDEO astronomy, may not be the best and is certainly not the consumate(!) way of imaging. But, it provides the additional possibility of imaging, if you have a reasonable visual setup. The choice is never easy? At the perhaps same weight/cost: A smaller DRIVEN Dob - with e.g. some (Video) imaging possibilities. Or a bigger Dob with greater visual potential etc. etc. I sense it depends on your priority to begin imaging, and the quality you hope to achieve.

[RikM]

If i were to buy the 10", is it possible to later on remove the tube from the Dobsobian mount and place it on an equatorial one?

Yes, you could...but it would not be nice starting point for DSO astrophotography. You would need an EQ6 at minimum. The weight would be huge and difficult to set up so really would be better permanently mounted in an observatory. The long focal length would make guiding much more challenging and you would be restricted to smaller objects because of the narrower field of view.

There are some things a 10" tracking Dob will do very well indeed, webcam imaging of planets or video astronomy for example or even...looking at stuff but 'Dob' and 'deep sky astrophotography' shouldn't normally be used in the same sentence.

If your main interest is imaging DSO's, a small refractor on an equatorial mount is the way to go about it. But do get a copy of 'Making every photon count' for a comprehensive run down of how to get started.

[SniffTheGlove]

Hey, im thinking of buying a 10" dobsonian, but the one i'm looking at doesnt have any tracking abilities, so will I be unable to take deep space photos with it?

I use a 10in Dob (well at least when there is no clouds about )

The visual viewing is great and you will see millions of stars through it.

As for astro imaging of planets/moon , you can only really work with a webcam (SPC880NC etc) and using Sharpcap is best, you will record what you see by recording to video and then putting the video through Registax (etc), this will break the video down into individual frames that you can then work with.

Depending on how fast or slow your scope is will depend on how quickly the image will track across the eyepiece/sensor. On my F7 with the SPC880 it takes approx 12sec.

To improve this I have built a Equatorial Platform for my dob to sit on and now I can keep the image in place for at least 15mins before needing to adjust speed etc by just rotaing my speed knob. Now this is no good for long exposure as the tracking is not accurate enough.

I am also having some success with using a EOS350D on the above setup but this is taking much longer due to lack of suitable viewing conditions .ie clouds. What I do is again use the platform and use my laptop to take hi-res shots using AstroPhotographyTool. I can do 200 shots at 3sec exposure and then use the stills in Registax/DSO

To me I know that I will not get the fabulous shots other SGL members get using their ED80/EQ6 setups but I am having fun doing what I can do on my 250mmDob/EP setup and having fun is the inportant bit.

If you get a kick out of AP then you can trade/buy etc a ED80 with a NEQ6 and slap a modded Canon EOS later on.

[RikM]

what about DSO's?

Take a look at the fantastic images posted by members in the Imaging - deep sky forum. Have a look at the equipment used and count how many are taken using Dobs.

[Capricorn]

You need a equitorial mount for reasonable astrophotography, and to put a 10 inch newtonian on you will need a big equitorial. Say EQ6 as a start.

The weight of a 10" scope is not insignificant, you have already asked about moving one round. The mount really needs to be big enough to handle about twice the scope weight, and you have to add in the camera. Starting to get big.

A driven dobsonian mount is Alt/Az and rotation of the object occurs, a rotated DSO is a blur.

As has been said astrophotography is not visual observing. I will add that astrophotography is not the same as you do during the day or in a studio. Consider that a single exposure for AP may be 10 minutes long and the object has to remain exactly in the centre of the scope while it is actually rotating across the sky.

This means accurate polar alignment by you, nothing else will do the alignment, you have to and it has to be accurate. Again it takes time, so stand the mount outside, level it, aim it at polaris and take a shot is not on.

Is there a club in your area which has an imaging section or group? If so pay them a visit first. You will get a lot of direct information from one. You may see what it normal and what you could use as a first foray. I will guess that it is not what you expect.

[Ptarmigan]

Low Light level VIDEO cameras have a sensitivity 0.00002 lux. Coupled with (say) an 8-10" Dobsonian, you can display 16th magnitude stars on a screen in REAL time.

Very interesting, so coupled to a modest lens it would serve as a clear sky detector if fed to a small monitor on top of the TV ?! Thanks, I have been reading the forum for a while now but only just found the groups, joined the Dob group 'tuther day, now I'll have to watch the video group as well

What sort of ball park do they cost?

Apologies to TheEli I dont mean to usurp your thread:icon_salut:

A smaller DRIVEN Dob - with e.g. some (Video) imaging possibilities. Or a bigger Dob with greater visual potential etc. etc.

yes that is the big dilemma ! I am tending to the visual side with imaging taking a back seat.