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smallest Lunar feature visible with DSLR camera and less than 5 inches aperture

dslr astrophotography moon imaging
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#1 Nicole Sharp

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Posted 11 September 2019 - 03:59 PM

Open question for anyone, but what is the smallest Lunar feature you have ever been able to identify using a DSLR camera and less than 5 inches (114 mm or less) of aperture?

 

Let me know what settings or techniques you might have used, and if possible post or link a photo.

 

Ideally trying to see something 20 km or less in scale, since that would have an angular diameter similar to what Mercury will have in 2019 (10 arcseconds).

 

I haven't attempted stacking yet, but my first run with a DSLR camera for Lunar imaging with 114 mm of aperture definitely doesn't have 10-arcsecond resolution for single-shot imaging (no stacking).  My target crater was Cleomedes G (19.4 km), but I could only identify the much larger Cleomedes (126 km) in the single-shot images.  It's going to take me some time to learn processing techniques, but I'd like to see some examples of what might be possible for high-resolution (less than 10 arcseconds or 20 km) Lunar imaging using a DSLR camera with small apertures (including telephoto lenses).


Edited by Nicole Sharp, 11 September 2019 - 04:05 PM.


#2 Aaron_tragle

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Posted 11 September 2019 - 04:27 PM

Impossible to calculate due to constantly changing and random effects of seeing.


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#3 rolo

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Posted 11 September 2019 - 04:40 PM

Neil Armstrong's footprint... 



#4 photoracer18

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Posted 11 September 2019 - 05:01 PM

If the FirstLight Twilight Nano manual mount is all you have then you are out of luck most likely. The more magnification you have the faster the Moon will move across the FOV and the shorter the exposure you can use to try and freeze the frame. Shooting video might work better but I am not an expert on video. Even an Alt-Az go-to mount would be better as the effect of field rotation is much less than the effect of no tracking at all.

 

I think I talked to you here previously as I see that you are not that far geographically from me. I would consider donating an Alt-Az go-to mount from my collection to you as I have a number of them I bought for a project (Nexstar 80 GT, SLT) that is over and I don't feel they are worth enough to ship to someone on a sale. I just need to check if the SLT has a Vixen rail plate-holder which is what I think you need. A bigger mount would be better but I don't have anything in-between I could give you.

 

My first Lunar images were done in the early 60's in high school with my Criterion RV-6 Dynascope Newtonian. B&W Film and a Praktica SLR which my father processed himself in our bathroom. I experimented with prime, afocal, and eyepiece-projection photography at the telescope. This came with a clock drive so it could track things in a basic sort of way.

 

Looking at your gallery I see some things that worked for you. At night there is something called the Looney 11 Rule. Its related to the photographers Sunny 16 Rule, except is is for night time and applies to lunar photography. Camera and/or scope at F11 and speed the reciprocal of the ASA of the film or ISO of the digital camera. If the telescope is around F11 then you can do prime photography using shutter speeds of like 1/100 to 1/400 depending on where you set the camera's ISO 100-400.


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#5 Nicole Sharp

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Posted 11 September 2019 - 05:34 PM

If the FirstLight Twilight Nano manual mount is all you have then you are out of luck most likely. The more magnification you have the faster the Moon will move across the FOV and the shorter the exposure you can use to try and freeze the frame. Shooting video might work better but I am not an expert on video. Even an Alt-Az go-to mount would be better as the effect of field rotation is much less than the effect of no tracking at all.

 

I think I talked to you here previously as I see that you are not that far geographically from me. I would consider donating an Alt-Az go-to mount from my collection to you as I have a number of them I bought for a project (Nexstar 80 GT, SLT) that is over and I don't feel they are worth enough to ship to someone on a sale. I just need to check if the SLT has a Vixen rail plate-holder which is what I think you need. A bigger mount would be better but I don't have anything in-between I could give you.

 

My first Lunar images were done in the early 60's in high school with my Criterion RV-6 Dynascope Newtonian. B&W Film and a Praktica SLR which my father processed himself in our bathroom. I experimented with prime, afocal, and eyepiece-projection photography at the telescope. This came with a clock drive so it could track things in a basic sort of way.

 

Looking at your gallery I see some things that worked for you. At night there is something called the Looney 11 Rule. Its related to the photographers Sunny 16 Rule, except is is for night time and applies to lunar photography. Camera and/or scope at F11 and speed the reciprocal of the ASA of the film or ISO of the digital camera. If the telescope is around F11 then you can do prime photography using shutter speeds of like 1/100 to 1/400 depending on where you set the camera's ISO 100-400.

 

As far as I know, all Lunar imaging is best done with short exposures.  So tracking shouldn't really be necessary for Lunar imaging, though does it make it a lot easier.  I haven't tried them yet, but I think there are applications that can crop and center the ROI, and then rotate the frames for stacking (PIPP was mentioned to me in another thread).  I found a really nice photo of Cleomedes G (19.4 km) with a DSLR camera and a (Barlowed) 750/150 Newtonian on AstroBin.com.  A 114-mm Newtonian might have half the resolution, but should be doable I think with similar processing and atmospheric conditions.  The photo from AstroBin required no less than five different software applications in order to produce, meaning it probably took a lot of time and work.

 

I've been to a couple of star parties with the Tri-State Astronomers in the Hagerstown-Martinsburg Area so it is possible we may have met there.  If you could even just loan a GOTO mount for the day of the Mercury transit, it would be a huge help!  I was going to try to rent a GOTO mount for November 11, but the budget is so tight, and I spent everything on the DSLR camera, so I haven't been able to get a power adapter, power supply, or intervalometer for the DSLR camera yet, which is probably going to be even more important than a tracking mount if I want enough images for stacking (6-image bursts are probably not enough).  But even a manual (nonmotorized) GEM would be easier to use for Lunar (or Solar) imaging than a manual altazimuth mount, especially at a longer focal length.

 

The feedback I have gotten so far is that continuous shooting at 6000*4000 will always produce better results than 1920*1080 video, even with a slower framerate.  I haven't tried 1080p video yet though to confirm that.


Edited by Nicole Sharp, 11 September 2019 - 05:45 PM.


#6 t_image

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Posted 11 September 2019 - 07:43 PM

Open question for anyone, but what is the smallest Lunar feature you have ever been able to identify using a DSLR camera and less than 5 inches (114 mm or less) of aperture?

 

Let me know what settings or techniques you might have used, and if possible post or link a photo.

 

Ideally trying to see something 20 km or less in scale, since that would have an angular diameter similar to what Mercury will have in 2019 (10 arcseconds).

 

I haven't attempted stacking yet, but my first run with a DSLR camera for Lunar imaging with 114 mm of aperture definitely doesn't have 10-arcsecond resolution for single-shot imaging (no stacking).  My target crater was Cleomedes G (19.4 km), but I could only identify the much larger Cleomedes (126 km) in the single-shot images.  It's going to take me some time to learn processing techniques, but I'd like to see some examples of what might be possible for high-resolution (less than 10 arcseconds or 20 km) Lunar imaging using a DSLR camera with small apertures (including telephoto lenses).

It is important to grasp the stark distinction between imaging the Sun during the day with 'seeing' issues, and imaging the Moon at night.

To set up a better analog, you need to try your experiments by imaging the Moon during the daytime (although less contrast),

you will get a better sense of daytime turbulence that impinges upon resolving details(which a Mercury transit entails) that are less during the night...



#7 sharkmelley

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Posted 12 September 2019 - 05:48 AM

If you are asking if it is possible to image the Mercury transit with a DSLR and a 114mm diameter scope then of course the answer is yes.

 

Just search "mercury transit" on astrobin.  Here's an example taken with a DSLR and a 110mm scope http://www.astrobin.com/248377/

 

You just need to decide if you want to capture the whole solar disc (making Mercury a tiny speck) or if you want Mercury to appear a good size.  It will determine what magnification Barlow to use.

 

For instance if your focal length is 500mm and your sensor pixel pitch is 5micorns then you have 2arcsec per pixel and Mercury will be 5 pixels in diameter and the solar disc will be 900 pixels in diameter.

A 5x Barlow will give an effective f/l of 2500mm and Mercury will be 5x bigger: 25 pixels in diameter.

 

Of course the atmospheric turbulence (i.e. the seeing) will be a limiting factor.

 

Mark


Edited by sharkmelley, 12 September 2019 - 05:56 AM.

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#8 Hesiod

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Posted 12 September 2019 - 06:44 AM

There are a few large threads you should check, "small bore challenge" under solar system astrophotography subforum.
Anyway, the analogy with Moon craters is not very good since these will have much worse contrast than Mercury crossing the Sun.
Be more relaxed: IMHO you should really care just about the kind of picture you want to take (e.g. timelapse, sequence, single shot) and exploit the next months to get familiar with the required techniques and equipment.

#9 KLWalsh

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Posted 12 September 2019 - 08:22 AM

Ok, I know this is pedantic, but 114 mm is not 5 inches it’s 4.5 inches.
A 5 inch aperture is 127 mm.
Also all DSLRs are not equal. The pixel size can vary a fair amount, as well as the quality of the electronics producing the image.

#10 KLWalsh

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Posted 12 September 2019 - 08:33 AM

You seem mostly concerned about photographing the transit of Mercury.
Why not begin now (?); start photographing the sun and maybe you’ll catch a small sunspot or two. And you’ll gain experience shooting the solar disk which is always harder to do on a first attempt than most beginners think. There is a LOT of glare and seeing the solar disk sharply can be a challenge.
You’ll learn what your scope and camera can do, what settings will work, whether guiding is an issue, etc.
As they say, one good test is worth a thousand theories.

Edit: They also say: Don’t get caught in analysis paralysis.

Edited by KLWalsh, 12 September 2019 - 08:37 AM.


#11 Nicole Sharp

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Posted 12 September 2019 - 10:22 AM

Is there a "small bore" challenge for Lunar features?  That's basically what I am looking for.  I posted in the DSLR forum since it would be a lot easier with a planetary webcam (and less of a challenge).

 

I am glad that the resolution for the Solar transit of Mercury will be less of a challenge than for imaging of small Lunar features.  But finding smaller Lunar features is a good challenge I think in and of itself.  I am learning a lot about selenography when I take the time to try to find particular features in my own images.

 

I think it should be possible to see 20-km resolution of the Lunar surface with 114 mm of aperture if I can learn computer processing techniques (and get really good atmospheric conditions for image acquisition).

 

Just wanted to hear if anyone else has tried this particular (DSLR) challenge with small apertures, and what were their results.


Edited by Nicole Sharp, 12 September 2019 - 10:32 AM.


#12 Hesiod

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Posted 12 September 2019 - 10:30 AM

It may be, I do mot remember.
I know that many use DSLRs even for hi-res solar system imaging, sometimes exploiting "hacks" to increase the frame rate.
Anyway, the key is to take as many shots as possible (either as stills or as movies) and feed them to a dedicated software; stack them and then sharpen as needed

#13 Nicole Sharp

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Posted 12 September 2019 - 08:57 PM

Found at least one example on AstroBin from afocal smartphone video with a 114-mm Newtonian by stacking hundreds of frames from 30 FPS video.  Definitely a resolution of under 20 km.  A DSLR camera with a Barlow would have higher camera resolution and less optical elements.  So it looks like I just need to learn how to stack up frames and I then maybe I can start wowing myself on the results, lol.  Will have to work on that.  If people have any "before and after" photos though from close-up Lunar imaging with smaller apertures would be curious to see the difference.


Edited by Nicole Sharp, 12 September 2019 - 09:01 PM.


#14 Alex McConahay

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Posted 12 September 2019 - 11:39 PM

>>>>>>definitely doesn't have 10-arcsecond resolution for single-shot imaging

 

I'm having trouble with the idea that you have difficulty resolving something 10 seconds wide.

 

Seems that we regularly resolve stars that are far smaller than that. 

 

Or am I missing something?

 

 

By the way, I understand that the smallest thing that can be resolved on the moon, from earth, is the size of the colosseum. Or the Coliseum. or......well, I don't know if they mean the LA Memorial Coliseum, or the colosseum in ROme, or what. And I have never found that in an official source.  I have also read that the smallest thing resolvable by Hubble on the moon is about 100 meters. It would be much less in your 114 mm. 

 

Alex



#15 Nicole Sharp

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Posted 13 September 2019 - 12:01 AM

>>>>>>definitely doesn't have 10-arcsecond resolution for single-shot imaging

 

I'm having trouble with the idea that you have difficulty resolving something 10 seconds wide.

 

Seems that we regularly resolve stars that are far smaller than that. 

 

Or am I missing something?

 

 

By the way, I understand that the smallest thing that can be resolved on the moon, from earth, is the size of the colosseum. Or the Coliseum. or......well, I don't know if they mean the LA Memorial Coliseum, or the colosseum in ROme, or what. And I have never found that in an official source.  I have also read that the smallest thing resolvable by Hubble on the moon is about 100 meters. It would be much less in your 114 mm. 

 

Alex

 

I think the problem is contrast.  Lunar imaging seems to be a greater challenge for getting resolution in that regard, especially without stacking.  I can see the Galilean moons and they are pretty small.  But they are bright against a dark background, and even then they only show up (at f/13) when I overexpose Jupiter.  Likewise, Mercury in black against a white Solar background should be easily visible too (I hope).


Edited by Nicole Sharp, 13 September 2019 - 12:04 AM.


#16 Alex McConahay

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Posted 13 September 2019 - 08:41 AM

>>>>>>> I think the problem is contrast.

 

Well, Mercury is pretty much a black dot going across the face of a bright sun. It really should be identifiable.

 

Alex



#17 KLWalsh

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Posted 13 September 2019 - 09:28 AM

With a 114 mm diameter scope at a 1500 mm effective focal length, the image of Mercury should cover about 20 pixels on the camera sensor.
You’ll need a high-quality full aperture solar filter, like the Baader solar film, and you’ll need practice shooting the Sun to be sure you’re getting a sharply focused image.
So what you really ought to be looking for is an app that will turn a series of full-resolution still images into a movie. (Or maybe a gif.)
Then you can shoot the transit with the camera using the time-lapse setting on the camera, and convert that into a movie using the app (if the camera doesn’t automatically do that for you).

Edit: You might want to make a Hartmann mask for your scope to help with focusing when aiming at the Sun.

https://lonewolfonli.../hartmann-mask/

Edited by KLWalsh, 13 September 2019 - 09:35 AM.


#18 BQ Octantis

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Posted 14 September 2019 - 05:50 PM

Is there a "small bore" challenge for Lunar features?  That's basically what I am looking for.  I posted in the DSLR forum since it would be a lot easier with a planetary webcam (and less of a challenge).

 

I am glad that the resolution for the Solar transit of Mercury will be less of a challenge than for imaging of small Lunar features.  But finding smaller Lunar features is a good challenge I think in and of itself.  I am learning a lot about selenography when I take the time to try to find particular features in my own images.

 

I think it should be possible to see 20-km resolution of the Lunar surface with 114 mm of aperture if I can learn computer processing techniques (and get really good atmospheric conditions for image acquisition).

 

Just wanted to hear if anyone else has tried this particular (DSLR) challenge with small apertures, and what were their results.

Small Bore Challenge: The Moon w/6" or Less (linked to Tom Glenn's results from a 114 Newt):

 

https://www.cloudyni...less/?p=8720230

 

Are you looking for results with a 114mm aperture or results from a small aperture? I've shot the moon through a 1.8mm aperture (my cell phone), but with my Canon DSLR I've shot it with my 8-16mm, my 15-85mm, my 55-250mm, my 200mm f/2.8L II, my 5-in 750mm SCT, and my 7-in 2700mm Mak-Cass. Surely a set of those would be a bounding case…

 

BQ



#19 Nicole Sharp

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Posted 14 September 2019 - 07:33 PM

Small Bore Challenge: The Moon w/6" or Less (linked to Tom Glenn's results from a 114 Newt):

 

https://www.cloudyni...less/?p=8720230

 

Are you looking for results with a 114mm aperture or results from a small aperture? I've shot the moon through a 1.8mm aperture (my cell phone), but with my Canon DSLR I've shot it with my 8-16mm, my 15-85mm, my 55-250mm, my 200mm f/2.8L II, my 5-in 750mm SCT, and my 7-in 2700mm Mak-Cass. Surely a set of those would be a bounding case…

 

BQ

 

The question is how do you get high enough resolution to photograph physically small (20 km or less) Lunar features with small apertures (i.e. trying to locate and identify specific craters).  The answer seems to be that you can't with small apertures unless you stack many frames to increase the resolution.  If you can do that with a DSLR lens though, that's even more impressive.


Edited by Nicole Sharp, 14 September 2019 - 07:35 PM.


#20 17.5Dob

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Posted 14 September 2019 - 07:47 PM

You seem mostly concerned about photographing the transit of Mercury.
Why not begin now (?); start photographing the sun and maybe you’ll catch a small sunspot or two. And you’ll gain experience shooting the solar disk which is always harder to do on a first attempt than most beginners think. There is a LOT of glare and seeing the solar disk sharply can be a challenge.
You’ll learn what your scope and camera can do, what settings will work, whether guiding is an issue, etc.
As they say, one good test is worth a thousand theories.

Edit: They also say: Don’t get caught in analysis paralysis.

The OP went beyond your last point many threads ago, but the rest is sound knowledge.

The time for asking questions is long past. Now is the time to start shooting and testing !



#21 KLWalsh

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Posted 14 September 2019 - 09:24 PM

The OP went beyond your last point many threads ago, but the rest is sound knowledge.

The time for asking questions is long past. Now is the time to start shooting and testing !


(sigh...) Yeah, I know...

#22 BQ Octantis

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Posted 14 September 2019 - 10:35 PM

Some simple calculations…

 

θmin = 1.22 × λ / D

 

If D is 114mm, and λ = 536 nm, then  θmin is 5.74 microradians or 1.18 arcseconds—an order of magnitude higher than your target of 10 arcseconds. But if you're letting the DSLR's mirror reflex right before the shutter opens, it's hard to tell what kind of performance you're getting with all the resultant vibration…but I'll bet it's way less than 1.18 arcseconds!

 

Your best bet to capture a transit would be in-camera RAWs taken from LiveView with an intervalometer with the right wait time between exposures (probably 6-8 seconds). Alternatively, LiveView capture via USB 2.0 to a laptop running BackyardEOS would allow you to capture ~20fps with no mirror vibrations.

 

BQ


Edited by BQ Octantis, 14 September 2019 - 10:36 PM.

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#23 Nicole Sharp

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Posted 14 September 2019 - 11:35 PM

Some simple calculations…

 

θmin = 1.22 × λ / D

 

If D is 114mm, and λ = 536 nm, then  θmin is 5.74 microradians or 1.18 arcseconds—an order of magnitude higher than your target of 10 arcseconds. But if you're letting the DSLR's mirror reflex right before the shutter opens, it's hard to tell what kind of performance you're getting with all the resultant vibration…but I'll bet it's way less than 1.18 arcseconds!

 

Your best bet to capture a transit would be in-camera RAWs taken from LiveView with an intervalometer with the right wait time between exposures (probably 6-8 seconds). Alternatively, LiveView capture via USB 2.0 to a laptop running BackyardEOS would allow you to capture ~20fps with no mirror vibrations.

 

BQ

Yeah, I only just found out that it's likely all of my initial test images are blurry simply because of mirror shake.  So will have to try again with mirror lock-up enabled and not using bursts.  There's a learning curve.  No laptop though.  Still trying to get a timer remote first.


Edited by Nicole Sharp, 14 September 2019 - 11:35 PM.


#24 sharkmelley

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Posted 15 September 2019 - 01:54 AM

Yeah, I only just found out that it's likely all of my initial test images are blurry simply because of mirror shake.  So will have to try again with mirror lock-up enabled and not using bursts. 

You don't say which camera you are using.  If it has silent shutter mode (i.e. electronic shutter) then use it.  It makes an incredible difference.

 

Mark


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#25 Nicole Sharp

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Posted 15 September 2019 - 02:59 AM

You don't say which camera you are using.  If it has silent shutter mode (i.e. electronic shutter) then use it.  It makes an incredible difference.

 

Mark

 

The Canon EOS Rebel SL2 (200D).  I saw that in the manual.  But Canon didn't really explain it other than that it slows down the framerate.  What does it do?


Edited by Nicole Sharp, 15 September 2019 - 03:00 AM.



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