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What am I doing wrong?

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#1 KD58

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Posted 24 January 2013 - 11:05 PM

I am a novice at astronomy and I am having trouble with simple AP.

I have an ES 127 and have been trying to image the moon with my 5D MkII. However I can't seem to be able to get focus. All I see is a large white spot in live view. I have used a 2" adaptor connected directly to the focuser, tried attaching the adaptor to a 3-1/2 inch extension tube, attached the adaptor to a diagonal, tried a 5 inch extension tube but no luck. I can achieve perfect focus with an eyepiece, and an eyepiece attached to a 4X powermate but can't focus with the DSLR. It's driving me nuts and I'm sure that I am making some basic mistake but am too stupid to appreciate what it is. I would appreciate any help and advice that I can get.

#2 lamplight

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Posted 24 January 2013 - 11:13 PM

Hi

Welcome to CN!

I'm not an expert on this but what I found on my refractor is I have to remove the diagonal to get focus when attaching my camera prime.

#3 KD58

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Posted 24 January 2013 - 11:15 PM

I have tried that but no luck:(

#4 shawnhar

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Posted 24 January 2013 - 11:40 PM

Reduce the exposure time to 1/125 second?

#5 KD58

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Posted 24 January 2013 - 11:52 PM

Can't say for sure if I tried 1/125 but in the dark I dialled up and down to see it it made a difference, just made it brighter or darker. I'll try to do it again tomorrow if clouds allow it.

#6 pogobbler

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Posted 25 January 2013 - 03:30 AM

You might first try the setup in the daytime, focusing on a distant object so the focus will be at or near infinity, make sure not to move the focus and then try it at night. With that, you know the focus, at least, should be correct or nearly so.

#7 Startraffic

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Posted 25 January 2013 - 06:20 AM

KD58,
You might even try shooting it in the afternoon. The Moon is up right now & bright enough to be able to see & still have enough light to see what your doing. It may be you don't have enough back focus.
I also see that you fairly new to astronomy, AP is not a simple task to do. Visual is much easier to make sure your gear is working for you. DAMHIKT

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#8 Achernar

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Posted 25 January 2013 - 08:36 AM

Usually a camera is connected directly to the focuser, that is when you are doing what is calle prime focus photography. I would try setting up during the daytime, and testing your scope and camera on a landmark at least a mile away. If you can get the camera to focus then, you should be able to focus the camera on the moon and stars. If not, there is not enough travel in the focuser to bring it to focus. If there isn't enough travel, it appears you can't rack the focuser far enough inwards to focus the camera. It takes quite a long path for light to pass through a diagonal then an eyepiece, and many refractors for that reason have no problem bringing a camera to focus.

There is another possibility to investigate. If the telescope has been outside for a period of time, the objective lens can dew up despite the dew cap most refractors have. If it does dew up, the moon will be turned into a blurry blob. If you get sharp focus during the daytime, I'd bet my last eyepiece that's the source of the problem. I would see if there is a local club, problems like this one really require hands on help. Hopefully, I narrowed down the list of possible causes.

Taras

#9 KD58

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Posted 25 January 2013 - 09:57 AM

I appreciate all the helpful advice. I'm at work right now but will set up tonight and try to work out the problem based on all of the suggestions. I'll try viewing in the daytime tomorrow as I'm likely to get time.

#10 michael hester

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Posted 25 January 2013 - 10:24 AM

You probably don't have enough backfocus. This happens on refractors a lot. They design the focuser such that any eyepiece placed in the diagonal they included would come into focus. Your diagonal easily adds 4 inches to the backfocus so you need to compensate that much.

I assume you have a T adapter for your camera and the appropriate 2 inch nosepiece (or 1.25 inch nosepiece). If you don't have these then you need to get them to do prime focus photography. If you don't want to use these or don't have them you can put an eyepiece in and do par-focal photography. In this case what you see is what you get: focus the eyepiece as normal then hold the camera up to the eyepiece with its lens on.

With a T adapter/nose piece combo you can attach your camera to the diagonal to get the back-focus you need. If you want to go straight through rather than diagonal then you need to compensate for the backfocus with a tube extension (you mentioned you had one). Finally this weekend the moon is approaching full moon and will be ridiculously bright. Your scope will amplify the brightness several fold (that's what it's designed to do). If your scope came with a lens cap with a removable center you'll need to use that. You'll also need to use a significantly fast exposure, on the order of 1/2000 or faster. The bright side of this (no pun intended) is you can record video and stack it to increase signal to noise ratio and get some awesome detail out of the moon disc.

#11 Fogboundturtle

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Posted 25 January 2013 - 11:24 AM

seems to me you are not in focus and your exposure is too long. I have an Meade 127mm (same as the ES) and I have no problem focusing with my Mark III. I am pretty sure this scope as enough backfocus as the focuser has huge amount of travel.

#12 SkipW

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Posted 25 January 2013 - 07:31 PM

You are doing this with the lens off, aren't you?

Try pointing it at the moon, then take the eyepiece out, rack the focuser all the way in and see where you have to hold your hand behind the tube to get a sharp image of the moon on it. That's the focal plane and where the sensor inside your camera needs to be.

#13 KD58

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Posted 28 January 2013 - 12:50 AM

Thanks for everyones help. I was able to focus with a little patience, proper exposure, and a small extension tube. However, now I need help with the photo itself. Here is an example:

http://www.flickr.co...s/88866446@N03/

It's not sharp, unlike the view through the eye piece. I use my 5DII in live view mode at 5x to focus and trigger the shutter remotely. Please understand that I am a novice and appreciate any advice that I can get. This seemed the best focus I could get. It's cropped but no PP. ISO 100, 1/500 s.

#14 CJK

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Posted 28 January 2013 - 06:33 AM

Focusing can be a major challenge. I read about focusing masks here on CN and decided to splurge on this one from Spike-A. My opinion: expensive, but worth every penny. It takes me less than a minute to get perfect focus now.

Focus masks are easy to make -- Ron Wodaski's book has a whole section on them -- so you don't have to spend $60 unless you want the added convenience and durability.

-- Chris

#15 Stargaz18

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Posted 28 January 2013 - 07:25 AM

Looks like a pretty good pic of a full moon to me. You'll get much more detail if you catch it at first or last quarter.

#16 Phil Sherman

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Posted 28 January 2013 - 12:44 PM

Getting the correct exposure for prime focus images of a full moon is easy if you remember the old (from film) daylight exposure rule: f/11 with a shutter speed equal to the ASA speed of the film. Use ISO for ASA and remember that each f/ stop change represents a doubling or halving of the exposure. The moon is lit by the sun, with the same amount of light we get during the daytime.

If you have an f/4 refractor and are shooting at ISO 200, you'll be three f/ stops faster that f/11 which means that you should be using an exposure time of around 1/1600 second.

Focusing on the full moon is very frustrating because there's no shadows to help you judge when you're in focus. Digital cameras with a "live view" function and image magnification can be easily focused by using a bright star or planet and a focusing mask. My preference is a Bahtinov mask, which you can make yourself using the generator at:
http://astrojargon.n...CookieSupport=1
When focusing with live view and a Bahtinov mask, use the highest ISO setting your camera has to make it easier to see the spikes. Better is to hook the camera to a computer and use its display for focusing and framing. If you don't have live view, you can take a series of exposures to get good focus. Once you're focused. point to your target of choice and start imaging.

Always use RAW recording mode for astrophotography. The moon can be imaged using JPEG but you'll still have better data to work with starting with RAW mode. In-camera JPEG conversion, when doing deep sky imaging, can easily discard 50% or more of the photons captured by the camera.

Astro images can be processed using Photoshop but you'll do much better using a program designed for AP. Mike Unsold's ImagesPlus (IP) is designed to work with DSLR (Canon, Nikon) RAW images and FIT images from almost all astro cameras. Best of all, it's a lot less expensive than Photoshop and doesn't require the additional purchased plugins that you'd end up getting for Photoshop. IP also has a camera control module, IPCC, that controls Canon and Nikon cameras. Exposures longer than 30 seconds with Nikon and older Canon cameras require an additional cable and some hardware to enable bulb shooting.

There's a steep learning curve for processing astro images. With anything other than the moon, you'll need to learn about lights, darks, flats, bias, flat darks (maybe) and how they all get used to make a good astro image. The days of taking a multiple hour exposure on a glass film plate are long gone and almost all astro images today are done by stacking multiple shorter exposure images together then processing the merged image. Planetary imaging is easiest to do with video recording and selection of a few tens of frames out of thousands taken. Planetary imaging also requires long focal lengths, generally obtained using a "Powermate", stacked barlows, or eyepiece projection.

Phil

#17 KD58

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Posted 29 January 2013 - 03:09 PM

Thanks for all the wonderful advice. CJK, I did order the Bahtinov and will post images with it when it arrives and the skies around here clear once again.

#18 rigel123

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Posted 29 January 2013 - 05:14 PM

That's a decent full moon being a single exposure and it's full! Most planetary, moon and solar images are done by taking video of the object and then stacking many images together and then using wavelets to bring out the details. Go to the Solar System Imaging Forum to catch some tips on the best methods and processing software for those types of objects.

#19 KD58

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Posted 30 January 2013 - 12:03 PM

Thanks for you advice Warren. I'll certinly do that.

#20 tedbnh

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Posted 30 January 2013 - 12:42 PM

I was reading that the MAHLI camera on Curiosity (on Mars) does auto-focus by taking a series of images at different focus points and generating a JPG file from each them. The better the focus, the more detail in the JPG file and thus the larger the file. They fit a parabolic curve to the focus points which create the largest 3 files and use the focus point corresponding to the maximum file size as the "best" focus.

Could we do the same for pictures of objects like the full moon? (The Bahtinov Mask is probably sufficient, but if you didn't have one this might be a backup plan.)

#21 Ratchet

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Posted 30 January 2013 - 01:43 PM

Mirror slap can vibrate the imaging train. Pro cameras have a mirror lock up setting. Or you can use timer delay to trigger lockup on some cameras.






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