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Any advice on selecting a scope for lunar photography?

astrophotography beginner equipment moon
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#1 jeffry7

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Posted 24 August 2019 - 01:07 AM

Hi Folks,

 

I have been thinking about getting a telescope to take another step in my quest to get decent moon pics. In thinking about this, I realized I did not know what qualities would be good in such a scope.

 

Do you want a long focal length? Do you get a short one and work with barlows and eye piece projection? Or what?

 

It seems like if you got a telescope with a color corrected lens, you would also need to get good barlows or eye pieces that were also color corrected, otherwise what would be the point?

 

For the moment I am sticking with my DSLR, but at some point I will upgrade that as well, just to get the frames per second.

 

Any thoughts? Suggestions?

 

Thanks!



#2 clarnibass

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Posted 24 August 2019 - 01:54 AM

Do you want photos of the entire moon or the smallest parts possible?

 

FWIW my approx 2000mm telescope with a full frame DSLR attached directly to it has about the entire moon in the frame, with very little borders around it. You can compare that with the sensor size you have and what you are looking for.


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#3 sg6

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Posted 24 August 2019 - 01:57 AM

Moon is big, but falls into the planetary aspect, so people use long focal lengths like Mak and SCT to obtain a video. The process the video = select only best frames (200-10%) and then stack just those and process, sharpen etc.

 

You will get the looking through water effect, hence the pick just the good frames from the video.

 

Size of moon is the "catch". With longer focal lengths you will get just a part of the moon, say where Armstrong went for a walk. So selecting the close in target and maintaining good tracking comes into it.

 

For long focal lengths you could need a lunar rate on the mount. Adds to the accuracy.

 

Not sure of a good scope, cannot recall the scopes that people have used when posting good lunar images. As ever you want sharp. Usually that means less glass in the path.

 

From working with someone one night if you want higher contrast then drop the ISO. Many start increasing it thinking that they are/will be making the difference between bright/dim greater. It doesn't, it makes everything bright.

 

Have fun, could start with the DSLR and a decent lens. And a tracking mount of some variety.


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#4 Tom Glenn

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Posted 24 August 2019 - 02:18 AM

With the Moon, you often have to balance resolution with field coverage.  Both can be maximized with mosaics, but to do this well requires extensive practice and experience.  The Moon is unique because of its size, and for this reason it tends to look good even at small image scales, which in turn means that even relatively inexpensive equipment can produce excellent images.  That being said, the Moon is very unforgiving when it comes to processing.  It has an extreme dynamic range, and it's not easy to recreate a natural look across the entire image.  There are many, many examples of garish lunar images to prove this.  

 

We would need to know more information about your budget and goals to recommend anything.  DSLRs do not excel at transferring raw data quickly from large ROIs of the Moon at high resolution, but they do a nice job of taking individual frames of the entire Moon.  So if you are serious about staying with a DSLR, I would consider something that fits the entire Moon into one frame.  Reflectors are generally preferred because the bright limb of the Moon will create visible chromatic aberration in refractors unless you spend money on an expensive triplet, which there is simply no reason to do for the Moon.  For inexpensive images of the Moon, it's hard to argue against a cheap Newtonian, although for wide field coverage you do have to factor in the price of a coma corrector.  Below are examples of images I have produced with a 6 inch, $200 Newtonian.  Usually I use a dedicated astronomy camera, but it does produce nice images with a DSLR, as shown in the second link.  I have posted many other images with this scope.  Hard to beat the image quality for the price.  And there's nothing special about that particular scope......my point is the Moon does quite well with modest equipment. 

 

https://www.cloudyni...ive-6newtonian/

https://www.cloudyni...inch-newtonian/

 

Many quality lunar images have been posted here, along with hundreds of pages of information, so I would recommend searching and reading.  And be skeptical of any advice that is not backed up by high quality images, in this case specifically of the Moon. 


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#5 james7ca

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Posted 24 August 2019 - 02:52 AM

Tom and I have the same 6" Newtonian (TPO brand, f/6) and coma corrector (Baader MPCC) and I agree that this is a good and relatively inexpensive way to start in lunar (or planetary) imaging. Another option (and quite popular) is something like the Celestron C6 (Schmidt–Cassegrain or SCT). When on sale you can get the C6 optical tube for around $400 (U.S.) but this is a longer focal length instrument that is better suited to taking images of parts of the moon (i.e. not the full disk, unless you do a mosaic).


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#6 jeffry7

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Posted 24 August 2019 - 04:20 AM

Do you want photos of the entire moon or the smallest parts possible?

 

FWIW my approx 2000mm telescope with a full frame DSLR attached directly to it has about the entire moon in the frame, with very little borders around it. You can compare that with the sensor size you have and what you are looking for.

I am wanting to do the full moon rather then individual features.



#7 jeffry7

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Posted 24 August 2019 - 04:42 AM


 

Have fun, could start with the DSLR and a decent lens. And a tracking mount of some variety.

This is what I am doing while dithering on what to do next. smile.gif



#8 jeffry7

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Posted 24 August 2019 - 05:11 AM

With the Moon, you often have to balance resolution with field coverage.  Both can be maximized with mosaics, but to do this well requires extensive practice and experience.  The Moon is unique because of its size, and for this reason it tends to look good even at small image scales, which in turn means that even relatively inexpensive equipment can produce excellent images.  That being said, the Moon is very unforgiving when it comes to processing.  It has an extreme dynamic range, and it's not easy to recreate a natural look across the entire image.  There are many, many examples of garish lunar images to prove this.  

 

We would need to know more information about your budget and goals to recommend anything.  DSLRs do not excel at transferring raw data quickly from large ROIs of the Moon at high resolution, but they do a nice job of taking individual frames of the entire Moon.  So if you are serious about staying with a DSLR, I would consider something that fits the entire Moon into one frame.  Reflectors are generally preferred because the bright limb of the Moon will create visible chromatic aberration in refractors unless you spend money on an expensive triplet, which there is simply no reason to do for the Moon.  For inexpensive images of the Moon, it's hard to argue against a cheap Newtonian, although for wide field coverage you do have to factor in the price of a coma corrector.  Below are examples of images I have produced with a 6 inch, $200 Newtonian.  Usually I use a dedicated astronomy camera, but it does produce nice images with a DSLR, as shown in the second link.  I have posted many other images with this scope.  Hard to beat the image quality for the price.  And there's nothing special about that particular scope......my point is the Moon does quite well with modest equipment. 

 

https://www.cloudyni...ive-6newtonian/

https://www.cloudyni...inch-newtonian/

 

Many quality lunar images have been posted here, along with hundreds of pages of information, so I would recommend searching and reading.  And be skeptical of any advice that is not backed up by high quality images, in this case specifically of the Moon. 

Hi Tom,

 

I have seen some of your images and been amazed.

 

I have been taking pictures of the moon for a while and have come to appreciate just how difficult it can be.

 

My specific goal is to have a set of pictures I can put up on my wall and say I took those. A little arbitrarily, I am going for whole disk of around 20" across at 300 dpi. I figure this will require a photo mosaic. But I also think this is something that will take years to accomplish with many intermediate steps along the way. In other words a $200 newt, which would never have occurred to me, sounds like a perfectly good stepping stone.

 

I agree that the DSLR is a limiting factor. My reason for sticking with it for now is to just change one thing at a time.

 

With the newt, do you not have to use a barlow to make up for the lack of back focus?



#9 jeffry7

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Posted 24 August 2019 - 05:14 AM

Tom and I have the same 6" Newtonian (TPO brand, f/6) and coma corrector (Baader MPCC) and I agree that this is a good and relatively inexpensive way to start in lunar (or planetary) imaging. Another option (and quite popular) is something like the Celestron C6 (Schmidt–Cassegrain or SCT). When on sale you can get the C6 optical tube for around $400 (U.S.) but this is a longer focal length instrument that is better suited to taking images of parts of the moon (i.e. not the full disk, unless you do a mosaic).

What mount do you put the newt on? I do not currently have anything that would do.



#10 james7ca

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Posted 24 August 2019 - 06:13 AM

What mount do you put the newt on? I do not currently have anything that would do.

I use it on a Celestron AVX mount, as shown below (this makes the mount look small and the scope overly big because of the wide-angle perspective of the camera).

 

And here is a link to my first light report on the TPO:

 

  https://www.cloudyni...n/#entry7166212

 

If you want to see some more shots of the moon using this scope then search for some of Tom's or my images (I've also done images of Jupiter and Saturn with this scope, also posted on CN).

Attached Thumbnails

  • TPO 6 Inch Newtonian on AVX.jpg

Edited by james7ca, 24 August 2019 - 08:51 AM.

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#11 aeroman4907

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Posted 24 August 2019 - 03:20 PM

Hi Tom,

 

I have seen some of your images and been amazed.

 

I have been taking pictures of the moon for a while and have come to appreciate just how difficult it can be.

 

My specific goal is to have a set of pictures I can put up on my wall and say I took those. A little arbitrarily, I am going for whole disk of around 20" across at 300 dpi. I figure this will require a photo mosaic. But I also think this is something that will take years to accomplish with many intermediate steps along the way. In other words a $200 newt, which would never have occurred to me, sounds like a perfectly good stepping stone.

 

I agree that the DSLR is a limiting factor. My reason for sticking with it for now is to just change one thing at a time.

 

With the newt, do you not have to use a barlow to make up for the lack of back focus?

Ultimately if you get a planetary camera, particularly the one the Tom and James use (based upon the IMX 183 sensor), you can drizzle the data by 1.5x with AS!3 and easily get a 300 dpi print of the moon greater than 20".  Drizzling should be more effective than usual if you use the identical setup of imaging around 900mm focal length, which is undersampled.  Undersampled data responds fairly well to drizzling.

 

I would also say from personal experience that printing even at 150 dpi will result in adequately sharp images, particularly with the moon which has more defined features.  Printing the moon at 300 dpi pretty much requires you to stick your nose on the print to see all the details.  That's a slight exaggeration, but not by much.  The whole 300 dpi for prints is a pretty excessive and archaic rule to go by and more consideration should be given to a reasonable viewing distance intended for the subject.  Just think about 4k televisions with arrays around 4096 x 2160.  If you went by the 300 dpi (or ppi in this case), 4K televisions would be ridiculously small at 13.67" wide by 7.2" tall.


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#12 jeffry7

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Posted 24 August 2019 - 07:44 PM

Ultimately if you get a planetary camera, particularly the one the Tom and James use (based upon the IMX 183 sensor), you can drizzle the data by 1.5x with AS!3 and easily get a 300 dpi print of the moon greater than 20".  Drizzling should be more effective than usual if you use the identical setup of imaging around 900mm focal length, which is undersampled.  Undersampled data responds fairly well to drizzling.

 

I would also say from personal experience that printing even at 150 dpi will result in adequately sharp images, particularly with the moon which has more defined features.  Printing the moon at 300 dpi pretty much requires you to stick your nose on the print to see all the details.  That's a slight exaggeration, but not by much.  The whole 300 dpi for prints is a pretty excessive and archaic rule to go by and more consideration should be given to a reasonable viewing distance intended for the subject.  Just think about 4k televisions with arrays around 4096 x 2160.  If you went by the 300 dpi (or ppi in this case), 4K televisions would be ridiculously small at 13.67" wide by 7.2" tall.

Good stuff!

 

I will have to do an experiment with 150 dpi and 300 dpi and see if makes a difference to me.



#13 Tom Glenn

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Posted 25 August 2019 - 12:44 AM

300 dpi may be arbitrary, but it is the often quoted standard for print resolution, for images that are intended to be viewed at very close range.  This comes from the fact that the average "normal" human vision yields a resolution of about 1 arcminute, which at a 12 inch viewing distance (very close inspection) equates to 0.00349 inches.  300 dpi equates to a diameter of 0.00333 inches per dot, so this makes it just under 1 arcminute of angle at 12 inches.  Therefore, people with normal vision should not be able to detect any pixelation in a 300dpi image.  

 

Images far below 300 dpi can be printed without pixelation, although the image scale does also affect the ability to perceive sharpness.  Images are always perceived as being razor sharp when the details that can no longer be resolved by the image (due to the optics and the quality of the image) are also too small to be perceived by the human eye in the print.  But keep in mind that a photo of the Moon that you hang on your wall becomes like any other fine art or photograph.  Most people enjoy these images from several feet away, and don't scour the image for detail.  Because this forum caters to the pixel peeping crowd, it is easy to forget that people don't generally inspect wall art that way!  

 

The other trap to be aware of is the 100% scale trap.  This will be different from monitor to monitor.  On my MacBook Pro, which has the Retina display, the screen resolution is 220ppi.  For all practical purposes, if an image looks sharp at 100% scale on this monitor in Photoshop, then nobody would detect any flaws at 300 dpi print size, even if inspected at 12 inches.  But I have a monitor at work that is much larger in size, but only 150ppi, and on this monitor, if I display an image at 100% scale and inspect close up, I can easily perceive the reduced sharpness compared to my 220ppi monitor.  When evaluating a potential image print size, be sure you are displaying the correct image size on your screen, and viewing from an appropriate distance.  

 

A 20 inch print of the Moon is a very attainable goal, even with a DSLR and a modest scope.  You can still benefit from image stacking, using individual raw files, if you convert your raw files to tif format and then use Autostakkert.  


Edited by Tom Glenn, 25 August 2019 - 12:46 AM.

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#14 clarnibass

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Posted 26 August 2019 - 07:53 AM

300DPI is a good standard but there are a lot of variables. The type of paper, type of printing, etc. can make more of a difference to how it looks overall than e.g. 300DPI vs. 240DPI, or even 180DPI sometimes (these are standards). It also depends what the printer can do and its quality. Just to give one example, I just did another project where I printed a lot of photos from about 45cm (17") to about 150cm (60"), all from a 24MP camera. The type of paper and printing was more significant than a certain amount of DPI difference.

 

It is usual to do tests i.e. print small parts of photos at the same scale you'd have eventually, to see differences like that. I would try that and see what you need, and maybe decide on the setup based on that.

 

One thing to consider is the entire eventual setup, if you really have a specific goal. You can get e.g. a telescope that would be best with the rest of the setup you have now, but if you eventually decide to get a different camera then you might find that the best option is one that would work better with a different telescope.




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