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Attempting Deep sky observations by Prime Focus Method.


tibbs1972
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I've been attempting to take shots of Betelguese tonight.

I managed to get some descent shots, but it was time consuming. I origionally wanted to get a shot of the Orion Nebula.

I aligned my scope with my 20mm lens, got the nebula in the centre of the lens.

When I swapped the lens for my DSLR camera for Prime Focus viewing, I could not locate the nebula, as the focus changed.

I repeated this method frequently without success.

Is there a better method than swapping lenses and re-focusing.

The spotter scope is the origional from Celestron. This isn't very good and is difficult to align. I can just about use it to find the Nebula with my 20mm lens.

I've finished tonight as the orion nebula has dropped behind the tree line.

Even though I didn't have sucess, I've got some good pictures of Betelguese, which I'll upload when I have processed the images.

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Hi Tibbs, it may be better if you post the question in the imaging section.

A 20mm lens on a DSLR is very wide, to shoot the Orion nebular will require something a bit longer. I think you will need a telephoto lens of at least 300mm for the job. A wide angle lens is best for shooting star trail and constellations.

If you don't have a telephoto lens of that focal length, you can try connecting the your DSLR to your scope. However, I am not sure if a DSLR can come to focus on your Powerseeker using the stock focuser. You can try it out on the moon to check.

I am just beginning to do a bit of astrophotography, so I am sure other people can give you much better advice. The way I took my Orion Nebula was to attach the camera to the scope right from the start and focus the system on the brighter stars of the Orion belt. Then I use the RDF to centre the rig on the nebula and begin shooting. The framing may not be very accurate, but there are enough room on the DSLR sensor to cope with these inaccuracy when shot with a FL500mm scope.

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  • 2 weeks later...

E621Keith - I think he meant a 20mm eyepiece, not lens, as he said when removing the `lens` he put the camera in its place..

Saying that, back to the original poster. Not knowing what DSLR you are using I cant really help too much, but if you have live view on it then that would be the best way of focusing.. You may need to `eye in` the focus using the usual method of the viewfinder, but switching to Live view, getting a nice bright star (beetleguese for example) and using the zoom function of live view will normally allow you to achieve a nice sharp focus - then recompose the shot to bring your subject back into view.

Edited by Simms
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Tibbs

I am new to this myself but have had reasonable success on Orion nebula.

First of all aim the scope using your lens.

Change over and attach your camera i.e. prime focus.

You will need to refocus and probably recentre your target.

You can use a Bahtinov Mask to aid your focussing but not essential.

Set camera to ISO 800 and take 10 to 30 sec exposures. Whichever is best you choose.

A remote to trigger your camera also helps avoid "camera shake"

Good luck

Neil

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E621Keith - I think he meant a 20mm eyepiece, not lens, as he said when removing the `lens` he put the camera in its place..

Sorry, my bad, I should have realise from his signiture.

Back to the OP, you mentioned a Celestron spotter scope, did you mean finder scope?

If you did meant a spotting scope are you imaging with that or your 127 Newt? If your are imaging with your Newt you can use the spotting scope as the finder for framing the nebula, it will do better than the standard finder scope. Frequently swapping camera and eyepiece in the dark is not a good idea.

How long is your exposure, you need at least a minute to get anything meaningful, if your DSLR does not show anything, it may be because the exposure time is too short.

If you were trying to image with your spotting scope, the DSLR may not be able to reach focus. Have you tried focusing at infinity in day light to check whether the scope can focus with a DSLR? My spotting scope cannot focus a camera at infinity without using a barlows lens.

Also, do you have RA motor drive on your GEM. If you do, it may be best trying to image with camera lens, because the Powerseeker GEM is far too light to handle a scope with a focal length of 1000mm. On the other hand, shooting with a nifty fifty at f2.8 will get you wonderful results after 30 seconds.

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I'm having the same challenges.

I am guessing, that the camera, is only viewing a small amount of the view.

It's a bit hit & miss (especially as up until now I haven't been using a tracking motor).

I want to try this with the camera, connected to the laptop - see what happens then.

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Tibbs, If you've not tried already, downloaded or used one. Download a camera utilities but of software.

I've just been using Backyard EOS - it changed things completely - so much easier to find, focus, etc, etc.

Shame the bloomin cloud came over, or i'd still be out there ......

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Tibbs, If you've not tried already, downloaded or used one. Download a camera utilities but of software.

I've just been using Backyard EOS - it changed things completely - so much easier to find, focus, etc, etc.

Shame the bloomin cloud came over, or i'd still be out there ......

Thanks, I'm trying out various free software packages now.

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