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Tips for newbie and the moon


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Hi Folks. I've just got myself a DSLR to begin learning a bit of astrophotography. I'm using a 150-PDS on a manual mount so was going to start with the moon. Very new to photography in general so could do with a few tips on suitable setup for getting some at least satisfactory shots.

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The Moon is very bright so youll be surprised how short the exposure time has to be. Set the camera to manual mode and ISO to the minimum. Try out different exposure times until you dont overexpose the bright parts of the Moon. Alternatively the "aperture priority mode" will also probably work. In that mode you choose ISO and the camera chooses the exposure time to be what it thinks is ideal. It works for the Moon a good chunk of the times.

Preferably underexpose rather than overexpose, since you cant recover detail from a fully white pixel but can stretch the darker pixels to appear brighter.

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I have a couple of tips that I use...

Focus, Use live view on the camera X10 while looking at the terminator area.

Manual will work but is a bit hit and miss if you dont know what settings to initially start with so go for AV or T which are semi auto modes. I cant remember off hand but one of those setting mentioned  does a good job of simulating the final shots correct exposure on the live view screen while you adjust shutter speed for example.  There will be trial and error involved but you will soon get the hang of the basic "go to" setting to start with.

Avoid starting out shooting in video mode for stacking images, a well focused and exposed single image can be a wonderful thing.

Thing to remember is that with a scope connected the camera has only two options to adjust for correct metering those are ISO value and shutter speed so keep an eye on both during setup, the ISO needs to be as low as you can get it but not at the expense of a slow shutter speed so its a fine balancing act.

Use a remote to control the camera or the in built delay to avoid any shake.

If the image is coming out slightly too bright or dim then use the exposure compensation control, especially important if running in a semi auto mode.

Have fun.

Alan

 

Edited by Alien 13
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Excellent, thank you both. I've downloaded EOS Utility on my laptop (had to get it off Canon's Hong Kong site, for some reason the UK/EUR/US sites only have the updater) so was planning to use that to remote control it. Just need to wait for some clear skies now to start playing 😁

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I recommend using a 2x Barlow. Your scope is a bit fast and the moon will appear too small and bright at the native focal lenght. With a Barlow at say 1500mm focal length the Moon will fit perfectly on a crop sized sensor. 

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1 hour ago, Nik271 said:

I recommend using a 2x Barlow. Your scope is a bit fast and the moon will appear too small and bright at the native focal lenght. With a Barlow at say 1500mm focal length the Moon will fit perfectly on a crop sized sensor. 

Ok thanks. I have a 2.5x powermate so that will be handy. What do you mean by crop sized sensor? Other than hovering my phone over the eyepiece I'm completely new to this. 

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You said you have a DSLR, so I assume you wish to attach it to the scope at the focuser (at 'prime focus') essentially using the scope as a big lens for the camera. The sensor inside your DSLR is either 'full frame' size ( 36x24mm) or a crop sensor (size varies, most often it's the APS-C  size: 23x15mm).

The image of the moon projects on the sensor and its size depends only the focal length so you should match the focal length with the sensor to fit either the full moon or part of it.

This calculator will show you what you can expect. Choose the imaging mode and enter the details of your telescope and camera.

https://astronomy.tools/calculators/field_of_view/ 

I suspect that without a Barlow the image of the moon will be undersampled i.e. too small for the resolution of your telescope. Sure it will still look good but with 150mm of aperture you may be able to resolve more detail.

For the Moon and planets ideally you should aim for focal ratio about 4 times the pixel size of the sensor in micrometers. Most cameras these days have pixel size of about 3-4micrometers, so you want a F12-F16 focal ratio to catch the best detail possible. In your case F5 is very undersampled but with 2.5 Balrow you are at F12.3 which seems about right.

The above applies for planets when you are taking very short exposures.

For imaging DSO it's the other way round you take long exposures (minutes long) and then big focal length is disadvantage because the tracking mounts are never that perfect. So for DSO your scope does not need the Barlow at F5 it's close to ideal. But then you need a tracking mount. 

 

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I had a look and it is the APS-C size. All useful information so thank you. A tracking mount is next on my wishlist as I'd like to give DSO a go one day. Would a 4x/5x Barlow be of any use or is that going too far the other way?

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a 4x/5x barlow will be a wobbly nightmare on a manual mount, and will be just a fuzzy mess.

The 2.5 powermate will give you not too bad zoomed in views, but use video capture best frame stacking to generate the best still image.

(lots of youtube tutorials on this)

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So the width with your 2.5x is fine. If you rotate the camera you can fit all of the terminator, which is the best area to photograph.

4x and above Barlow will not be worth it, in my opinion. It will create more trouble keeping the object in view and probably lead to oversampling.

 

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1 hour ago, Nik271 said:

So the width with your 2.5x is fine. If you rotate the camera you can fit all of the terminator, which is the best area to photograph.

4x and above Barlow will not be worth it, in my opinion. It will create more trouble keeping the object in view and probably lead to oversampling.

 

Plenty to be getting on with and lots more to learn. Much appreciated 

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