Orion nebula, failure

[royvanrijn]

Hey everybody,

After a great start with my 130P Dob photographing the moon and Jupiter (stacked) I decided to next try the Orion Nebula. The night was perfect, crystal clear cold night, but the nebula was kind of a failure. The limitations of the Dobsonian became painfully clear, very short exposures hardly showed any nebula, longer exposures (1 to 2 seconds) really clearly showed star trails.

In the end it was still amazing to see the nebula blurred... but it feels like it could have been so much better. Is there anything I could have done? I tried stacking some short exposure images, but those just didn't have any nebula to stack...

Or is photographing these objects with a (small) dob just impossible without a motorized tracker?

[Alien 13]

Not impossible its been done but depends on the camera settings.

Alan

[bogdog]

1 or 2 seconds exposure wont really collect much data...and you dont say what camera or iso setting you use?

a tracking mount ideally is what you need and an iso of 400 or 800 should show something,there are people who can image

with a dob though

[Steve 1962]

Hi  - well done for having a crack at it!

I wouldn't want to use the word "impossible", but it is going to be very difficult.

Although your Dob is a fine visual scope with which you can get good results on bright lunar and planetary targets, it isn't really suited to imaging faint DSOs (Deep Sky Objects) for two reasons:

1. As you've identified, it's not motorised, so it doesn't track the sky and if you go for long enough subs to get any detail in faint objects , the stars will trail.

2. Even if you motorised the mount to track the sky so that you could get longer subs you'll get field rotation - and to get rid of that you'll need a field re-rotator (nightmare!), an Alt Az mount on a wedge or, ideally,  an equatorial mount for your OTA.

Sorry not to be more positive!

Steve

[Alien 13]

I dont know your setup or the f ratio of the scope but you would need an ISO of between 1600 and 3200 to get some detail at 2 seconds exposure.

This thread might help. http://stargazerslounge.com/topic/204890-m42-through-a-goto-dob/

Alan

[royvanrijn]

I should have mentioned, I used my Canon 550D, with ISO up to 6400 (grainy) and also 3200. It did show a nice nebula, but with 1 second exposures it showed star trails already, and of course the nebula also had motion blur.

[royvanrijn]

Sorry not to be more positive!

There is nothing wrong with hearing my current setup isn't up for the job, I bought this beginners scope to see if it was worth any money to start with. Having looked at Jupiter and the Moon, and getting started with astrophotography I don't mind hearing that at all; that is exactly what I needed to hear to start looking into more advanced equipment!

Although I'm not going to sell the 130P Heritage, I'm going to keep that as travel scope and when my daughter gets old enough she can play around with it!

*goes browsing on what to upgrade to*

Any hints/tips? I like the idea behind dobs (simple, lot of light) but there are obvious drawbacks, maybe buying a good EQ first (attaching the current Heritage OTA) and upgrading the OTA afterwards? Seeing I enjoy astrophotography more than just looking around...

[Langy]

I don't know the focal length of your scope but if you are not tracking them you will need to use the 600 rule.

600 / (crop factor x focal length) I believe the crop factor on most canon cameras is about 1.6 as my 300D is.

[Steve 1962]

Hi again Roy.

If you're serious about ap, then you'll need a good eq mount. I would suggest a Skywatchers Heq5 as a minimum, but there are people who have success with smaller mounts.

Steve

[Pete Presland]

pretty tough doing DSO's with a dob, what about some widefield with a fixed tripod? you take multiple short images and stack them, its surprising the detail you can see.

[wxsatuser]

Hi again Roy.

If you're serious about ap, then you'll need a good eq mount. I would suggest a Skywatchers Heq5 as a minimum, but there are people who have success with smaller mounts.

Steve

Stick a SW 80ED on it and you have excellent bang per buck.

[cepheus42]

Hi,

I have just hit the astrophotography wall myself and its a very steep learning curve. I was told by a published astrophotography that "The Mount is everything". I bought a Skywatcher 80ED Pro for AP today and the recommended mount was an HEQ5 pro synscan. There were a few other bits that went with it but I got the whole set up for £1478 from Steve at First Light Optics. Ive got 3 other telescopes but for deep sky imaging the advice I was given lead to the ED80 and I bought it as a dedicated AP set up. So like you I'm embarking on the ride of a lifetime. But the point is, all the advice I have been given lead to the set up as described.

Hope that helps.

Peter Hutton