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Really noob DSLR question


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Hi, I'm pretty new to astronomy in general, and er, very new to astrophotography in particular.

I'm trying to image, well anything really, through a 200mm Newt using a Canon 500D prime focus. All I am managing to do is take lots of lovely images of the Newts mirror, and nothing else.

Please can some kind soul tell me what I am likely to be doing wrong?

Thanks,

Feeling very foolish,

Black Knight

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BK, which mirror are you getting shots of ? When you look through the viewfinder, what do you see.. even better activate liveview on the camera and look at the screen as you can zoom in. The moon, whilst not very high at the moment, makes an easy target to view and focus on for the next few nights (not so good when full as there's so little surface contrast). I'd suspect, that your focus position is out, so instead of focusing on the light from the mirror, you're getting the mirror instead.

Something to bear in mind, I have no experience of reflectors... having only really used refractors and a Mak.

Edited by jgs001
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I think john has hit the nail on the head. It sounds like you haven't achieved focus yet. I assume you have connect everything correctly? It would be good to see a pic / description of what you have got connected.

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If it looks like this, then you're not in focus. If you've tried focussing all the way in and out, then you may need a barlow or some other means to get focus.

post-18563-133877464393_thumb.jpg

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Have you got the 200p with the crayford focuser? If so I remove all the eyepiece adapters and connect the camera directly to the focus tube! and then I can achieve focus.

On my nikon the t-adapter fits snugly inside the focus tube then I just tighten the two thumbscrews.

If you havent got the skywatcher crayford I can't help you!

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I had this exact same issue when I tried on my reflector. Once I put a 2x Barlow on I was able to focus and get some pics. It was suggeste to me that I move my primary mirror up 30 mm or so, this should allow me to stop using a Barlow to achieve focus.

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id be to scared to move my mirrors i take my hat of to those brave enough. but i have seen the results first hand as a society member has done just that and it worked a treat

Grahame

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I recently found out that my skywatcher 250p ds has a removable thread on the 1.25" EP adapter which hopefully should allow me to achieve focus without a barlow. unfortunately the skies havent been clear enough for me to test this!!

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  • 2 weeks later...

Well, I got all the gear out intent on having another go at hopefully capturing a few DSO subs with my Canon 500D. Alas, no joy again - same problem as before.

After a lot of tinkering around though, and after completely removing the 1.25" EP adapter, and manually holding the camera in the focus tube for a few test exposures, I came to the conclusion that I was not able to achieve enough inward travel to reach focus.

So, SlipperySquid, I think your prognosis is correct. Thanks for that :D. I just ordered a 2" T adapter and hopefully this'll do the trick. And thanks to everyone else that came up with ideas for me to try out. It was really much appreciated.

So although it was a bit of a frustrating experience, I feel that at least now I may be going forward. And I did grab a look at M57 as well, so it's not all bad :).

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Well, had a good night tonight. Tried the Canon with the 2x Barlow and it worked! I swear I already tried it previously to no avail, but hey - I ain't complainin' :)

Majorly chuffed I got it working :D. The only problem I'm getting is the target gradually moves from the centre towards the edge of the picture, which I assume is lousy polar alignment or bad star alignment setup?

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Yup - it's a common problem with newts - not enough "inward focus". A barlow is one solution - or direct camera connection - some get round it by fitting a low profile focuser.

On an eq mount make sure your tripod is dead level and mount pointing magnetic north. Set the altitude to the latitude at your location. You should see polaris in the finder and if lucky it'll also appear in a low power ep (25-40mm).

Center it up in the ota using the alt/az screws, then go to a higher power and repeat the centering. I usually finish around 10-15mm for observing. This should eliminate drifting.

Hope that helps :)

Edited by brantuk
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Join the club Andy....i've totally overlooked that part being that i'm only just getting into being able to take more than 1 second exposures with a rough polar alignment via scope.

Oh well, another thing to do then i see haha.

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Oh and just to add, I replaced my skywatcher with a moonlight focuser due to not enough inward travel. That sorted, I now need an extension tube as i can get great focus with the camera, but require more outward travel for the eyepieces >..<

NM, it works, which is more than I'm used to :)

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  • 1 month later...
I recently found out that my skywatcher 250p ds has a removable thread on the 1.25" EP adapter which hopefully should allow me to achieve focus without a barlow.

I've been a complete plank!

I had no idea until five minutes ago the barrel on the 1.25" eyepiece adapter itself unscrewed. Up until now I have been using a 2x barlow (and not getting enough light in my exposures as a result), so now using this er, direct camera connection, I can get a little more light on my exposures.

Gah! What a donut! I'm feeling really stoopid now! :)

Setting up my mount now and hoping the clouds clear away ......

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It happens to the best of us Andy. I didnt have a clue about this until someone here told me. Now I know this works its great!!!!

Im gonna be getting my kit out in a mo to try my hand at some widefield :) cant wait, gotta wrap up warm though as its icy here.

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