Elongated Stars On Outside Of Images

[Carter Thiel]

I just got into astrophotography and I am having a problem with elongated stars.  Stars will look fine in the middle of the picture but as you move further outside the stars start to get all messed up and elongated.  I have a feeling it is from the adapter I am using to connect my Canon 450d to my telescope but I am not for sure.  

Any ideas of what I am doing wrong or how to fix it? 

Thanks

(Image of the Orion Nebula in heavy light pollution was just testing)

[Dave In Vermont]

Looks like a bad case of 'coma' and, perhaps, poor tracking. We'd need further information to nail down the culprits. So.....

What sort of telescope are you using? And tell us about your mount that you've got your set-up on, please? How long were you taking the Orion test-image for? The more details - the better.

If it's any help, it doesn't look like anything is broken or damaged. The probable 'fix' would require throwing some $£€'s at it. Financially speaking - astro-photography is a financial 'bottomless-pit.' But the results, many would agree, is well worth it!

Oh - this is your first post:

Greetings, Carter, and a warm welcome to SGL - we love to help people find answers to any & all questions in the learning of astronomy!

Starry Skies,

Dave

[JohnSadlerAstro]

Hi,

Welcome to SGL!  You will probably get more replies later, as it's 3 AM in the UK (where most of us are from) right now!  

Are you using a barlow or eyepiece at all? Or are you just attaching the camera body (ie., no lens) straight onto the focuser? What sort of scope is it, too?

If your camera is pointing into the eyepiece it's likely it just reflections off of the lenses.

John

[JohnSadlerAstro]

@Dave In Vermont

Good, we have an American -6 hour GMT--I'm off to bed!  

John

[Carter Thiel]

I am using a 130st on an equatorial mount.  In this image I took 90 pictures all at 1.3" exposures.  I also took 20 dark frames and 20 bias frames.  

I am using a 25mm eyepiece with no Barlow.

I am quite new to this so thanks for the quick responses. 

 

Also, I plan on getting a motorized mount soon, so if I am correct it should be a lot easier.

[JohnSadlerAstro]

Hi,

Right, so the issue is the method you are taking the shots by. Using a lens and eyepiece (afocal imaging) wont really work very well on deep-sky objects: what you really need to do is attach the cam directly to the scope (turning the scope into a lens). One of the main reasons for this is that it will give you a larger FOV and better quality shots. I would recommend the book, "Making Every Photon Count" by Steve Richards, it goes into all aspects of deep-sky imaging and is a must if you want to go further with this: get the book before you make any other purchases, and it will all make sense fast.

As to my thoughts though, I would suggest you get motors and a say, 55-200mm lens that you can use piggy-backed on the scope for some widefield images.

John

[Carter Thiel]

Thanks a lot I will start researching and let you go to bed 

[JohnSadlerAstro]

 <yawn>

I wish you all the best--it's hard, this astronomy thing....

John

[Dave In Vermont]

I'd help more, but I have no experience as an astro-photographer - though I plan to begin doing video-AP this Spring/Summer - so I can't help you more on the AP side of things. The optics of telescopes and what can go wrong I can help with. Hence my thinking of 'coma' and 'tracking' coming into play here. Hence Johns' advice on a motor-drive and such - which will allow your telescope & camera to track objects in space automatically.

I'm sure reading "Making Every Photon Count" by Steve Richards - this is an excellent book suggestion John has made. You can find out more about this with this link:

http://astronomynow.com/books/MakingEveryPhotonCount.html

You should be able to find it easily on the web, or shops in Florida.

A question for you, Carter: Have you got Stellarium yet? Or know what this is? I'll give you a brief description:

Stellarium is a "planetarium-program" which will show you a very realistic image of your night sky from your location - which you enter - and the images will be as simple, or as advanced (more types of objects) as you choose. It helps to find your way around out there and how to find them. Software-Programs like it (Stellarium is one of the best) can cost you over $200 easily. But Stellarium is free-of-cost. Nothing to buy. I consider it the greatest astronomy-bargain in existence. So if you don't have it, and would like to, let me know. I'll send you the links to download and install it.

Have fun out there!

Dave

[geordie85]

As already mentioned your main problem is having an eyepiece in your imaging train. The main problem this has caused it's it has greatly exaggerated the coma present in your FOV. You'll need a coma corrector which will fix the stars at the edges of your images.