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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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#26 Nicole Sharp

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Posted 15 September 2019 - 03:12 AM

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?

 

The manual doesn't really explain it, but I googled, and it looks like all it does is slow down the speed of the mirror.  The mirror still goes up and down for each shot same as in all other drive modes.  I guess a slower-moving mirror might produce less vibration, but would have to test it at a long enough focal length to find out.  Might be worth checking out though.



#27 Nicole Sharp

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Posted 15 September 2019 - 03:19 AM

OK, but StackExchange says that exposures of less than 0.1 seconds in duration aren't affected by mirror shake, but that could be proportional to focal length.  I was trying as short of exposures as I could get at 1500 mm.  Though it's possible the flimsy mount and the stock focuser (or a slight breeze) made it worse, especially if I was doing 10-shot bursts at 5 FPS in JPG (no RAW).  On a fixed (nontracking) altazimuth mount, there is apparent motion as well, but I don't think it would be visible in ultrashort exposures.


Edited by Nicole Sharp, 15 September 2019 - 03:26 AM.


#28 Alex McConahay

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Posted 15 September 2019 - 11:41 AM

Put a delay in each shot. The delay starts with the mirror going up, the camera settles, and then the shutter fires. 

 

Alex



#29 RedLionNJ

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Posted 15 September 2019 - 01:38 PM

OK, but StackExchange says that exposures of less than 0.1 seconds in duration aren't affected by mirror shake

 

This is utter poppycock. StackExchange is a forum for the gathering of opinions, often from non-experts, with the most appealing opinion being voted highest.

 

Take the mirror out of the situation altogether. Surely your DSLR has a mirror lock-up feature?



#30 RedLionNJ

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Posted 15 September 2019 - 01:41 PM

The answer seems to be that you can't with small apertures unless you stack many frames to increase the resolution. 

This is totally not the purpose of (or result from) stacking.

 

All stacking will do is increase the signal-to-noise ratio.  It has nothing to do with resolution. Resolution is limited by seeing, aperture size, effective focal length and sensor photosite size.



#31 BQ Octantis

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Posted 16 September 2019 - 02:38 AM

OK, but StackExchange says that exposures of less than 0.1 seconds in duration aren't affected by mirror shake, but that could be proportional to focal length.  I was trying as short of exposures as I could get at 1500 mm.  Though it's possible the flimsy mount and the stock focuser (or a slight breeze) made it worse, especially if I was doing 10-shot bursts at 5 FPS in JPG (no RAW).  On a fixed (nontracking) altazimuth mount, there is apparent motion as well, but I don't think it would be visible in ultrashort exposures.

With an APS-C sensor at prime on a 1500mm FL objective, the 1.6 crop factor means the effective focal length is 2400mm. The rule of thumb for terrestrial photography is to do handheld at no less than the inverse of the aperture FL in seconds, so 1/2400 sec. So you may very well be able to capture workable images at 1/4000 sec with the DSLR mirror hammering your setup…but certainly not at 1/10 sec. Not sure how the 0.1 sec number was derived, but I doubt it used 2400mm as the effective focal length. But don't take my word for it…you have the setup in question to figure it out through experimentation. And the exposure bracket program on your new intervalometer can help you find the knee in the curve. Heck, if you can make it work with the hammering, you could capture an infinite number of JPEGs at 5 fps in continuous shooting mode…

 

BQ


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#32 Alen K

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Posted 16 September 2019 - 08:27 PM

This is totally not the purpose of (or result from) stacking.

 

All stacking will do is increase the signal-to-noise ratio.  It has nothing to do with resolution. Resolution is limited by seeing, aperture size, effective focal length and sensor photosite size.

IF you are undersampled, drizzling, which is a form of stacking, can improve resolution. However, the resolution of the optical system and most importantly the seeing must not be the limiting factors. IOW, there has to be real detail that is being undersampled for drizzling to work. 



#33 Nicole Sharp

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Posted 19 September 2019 - 05:04 AM

Thanks for all the help.  Still going through photos and working on enhancing my Lunar-imaging techniques.  Will take a lot of practice to get good, but I think I already got below 10-arcsecond (20-kilometer) resolution *HANDHELD* at 250/45 with the Canon EF-S 55-250 IS STM kit zoom lens on the EOS Rebel SL2 (200D).  No tripod, no timer, no telescope, and no stacking (single-shot only).  :-O  Using ultrashort exposures (one millisecond or less), manual focus, image stabilization, mirror lockup, and single-shot silent shooting to slow down the speed of the mirror (thanks again for the tip about that).


Edited by Nicole Sharp, 19 September 2019 - 05:10 AM.


#34 Nicole Sharp

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Posted 19 September 2019 - 05:24 AM

I'm hardly a selenographic expert, but trying to compare Virtual Moon Atlas to my handheld photos taken with the 55-250 kit zoom lens, and I can definitely identify Sosigenes A (12 km in diameter), but there are a number of smaller craters nearby (adjacent to Sosigenes and Caesar) that I can see in the photo but am not sure the names of.  So likely getting down to maybe 3 arcseconds or less, which is really pushing the limits of the 45-mm aperture.  I might be able to identify more if I could overlay a map perhaps.  It doesn't help that the field is rotated either.  Not really sure how it can be possible for me to see so much detail in a handheld single-shot photo taken from a 55-250 kit zoom lens.  I'm guessing it's just the image stabilization coupled with the extremely short exposure time (1/4000 of a second), and maybe I also just happened to get a "lucky" image under very clear skies.


Edited by Nicole Sharp, 19 September 2019 - 05:31 AM.


#35 BQ Octantis

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Posted 19 September 2019 - 05:34 AM

Thanks for all the help.  Still going through photos and working on enhancing my Lunar-imaging techniques.  Will take a lot of practice to get good, but I think I already got below 10-arcsecond (20-kilometer) resolution *HANDHELD* at 250/45 with the Canon EF-S 55-250 IS STM kit zoom lens on the EOS Rebel SL2 (200D).  No tripod, no timer, no telescope, and no stacking (single-shot only).  :-O  Using ultrashort exposures (one millisecond or less), manual focus, image stabilization, mirror lockup, and single-shot silent shooting to slow down the speed of the mirror (thanks again for the tip about that).

Not a surprise at all to me, Nicole—I've spent 20 years doing handheld low-light photography. If you're using mirror lockup, there's no need for the silent shooting—you're just slowing down the camera's readiness for the next exposure. As before, the rule of thumb for the limiting shutter speed for hand-held is 1/FL sec (FL is Focal Length). With the APS-C scale factor, the equivalent FL for your 250 is 1.6×250 = 400mm. So the minimum hand-held without IS is 1/400 sec. IS typically buys you another stop, which brings the limit down to 1/200 sec. One millisecond is 1/1000 sec or 5× what you need. This is important because you're sacrificing precious SNR with lower exposures. And trying to stack with handheld is a real bugger—you have to manually find the rotation between frames. This is the major advantage of tripod.

 

If you're going to shoot the moon handheld, I recommend the following workflow:

  • Set the camera to 1/250sec ISO200 f/8, daylight white balance.
  • Turn on mirror lockup.
  • Set the shutter to 2 second delay.
  • Brace yourself on something solid.
  • Hold the camera close to your body.
  • Aim at the moon and get it into focus (I like using autofocus in LiveView and then setting the lens to manual focus).
  • Take a deep breath and hold it.
  • Press the shutter button and wait 2 seconds.
  • Relax and repeat.

If you don't have anything to brace against, recommend controlling your sway to force it in the direction of the target—motion in the axial direction is way more forgiving than in the lateral direction.

 

Cheers,

 

BQ



#36 Nicole Sharp

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Posted 19 September 2019 - 05:38 AM

Unless of course I am way off in my selenographic interpretation:

 

https://www.nicolesh...n/Capture20.PNG

 

Could that be Agrippa and Godin instead of Sosigenes?

 

Menelaus is 27 km in diameter though.  So there's still a lot of other craters that look like less than 10 arcseconds (20 km).

 

I wish there was a way to overlay Lunar maps on photos.  I thought that VMA supported that but not sure how to try it.  It would probably need a certain number of known reference points.  But if I could get a transparent PNG or SVG map maybe with a high enough resolution, I could try to rotate it, adjust the scale, and overlay it in GIMP.


Edited by Nicole Sharp, 19 September 2019 - 05:59 AM.


#37 Nicole Sharp

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Posted 19 September 2019 - 06:10 AM

Not a surprise at all to me, Nicole—I've spent 20 years doing handheld low-light photography. If you're using mirror lockup, there's no need for the silent shooting—you're just slowing down the camera's readiness for the next exposure. As before, the rule of thumb for the limiting shutter speed for hand-held is 1/FL sec (FL is Focal Length). With the APS-C scale factor, the equivalent FL for your 250 is 1.6×250 = 400mm. So the minimum hand-held without IS is 1/400 sec. IS typically buys you another stop, which brings the limit down to 1/200 sec. One millisecond is 1/1000 sec or 5× what you need. This is important because you're sacrificing precious SNR with lower exposures. And trying to stack with handheld is a real bugger—you have to manually find the rotation between frames. This is the major advantage of tripod.

 

If you're going to shoot the moon handheld, I recommend the following workflow:

  • Set the camera to 1/250sec ISO200 f/8, daylight white balance.
  • Turn on mirror lockup.
  • Set the shutter to 2 second delay.
  • Brace yourself on something solid.
  • Hold the camera close to your body.
  • Aim at the moon and get it into focus (I like using autofocus in LiveView and then setting the lens to manual focus).
  • Take a deep breath and hold it.
  • Press the shutter button and wait 2 seconds.
  • Relax and repeat.

If you don't have anything to brace against, recommend controlling your sway to force it in the direction of the target—motion in the axial direction is way more forgiving than in the lateral direction.

 

Cheers,

 

BQ

 

I think I may actually have "cheated" a little bit by sitting on the ground for some of the handheld photos (I didn't hold my breath :-O ).  Some were taken standing up, and some sitting down.  Wasn't sure but this particular one might have been sitting down probably.  To hold the camera still enough to get long enough exposures (at f/4) to capture starfields at the zenith, I actually had to lay down on the ground and point the camera straight up.  Most of those are still blurry, but a couple came out really nice with pinpoint stars.  You have to zoom in really close up to see that the stars are a little blurry from being handheld, even with the image stabilization.  Overall though I am really happy with the DSLR camera so far, and it's a lot more fun to use than a webcam, even if it can be a little frustrating for planetary imaging.  This was only my second time ever using the DSLR camera without the telescope (fifth time overall), and my very first time trying out the 55-250 zoom lens.  I also got a nice handheld photo (at 55 mm f/4) of the Pleiades in conjunction with Luna, but of course Luna is heavily overexposed.


Edited by Nicole Sharp, 19 September 2019 - 06:22 AM.


#38 BQ Octantis

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Posted Yesterday, 02:23 AM

I think I may actually have "cheated" a little bit by sitting on the ground for some of the handheld photos (I didn't hold my breath :-O ).  Some were taken standing up, and some sitting down.  Wasn't sure but this particular one might have been sitting down probably.  To hold the camera still enough to get long enough exposures (at f/4) to capture starfields at the zenith, I actually had to lay down on the ground and point the camera straight up.  Most of those are still blurry, but a couple came out really nice with pinpoint stars.  You have to zoom in really close up to see that the stars are a little blurry from being handheld, even with the image stabilization.  Overall though I am really happy with the DSLR camera so far, and it's a lot more fun to use than a webcam, even if it can be a little frustrating for planetary imaging.  This was only my second time ever using the DSLR camera without the telescope (fifth time overall), and my very first time trying out the 55-250 zoom lens.  I also got a nice handheld photo (at 55 mm f/4) of the Pleiades in conjunction with Luna, but of course Luna is heavily overexposed.

I started my first serious foray into AP with the Canon 55-250 f/4.5-5.6 Mk1 kit zoom (Mark 1)—in fact, my first crack at superresolution was with it on Venus:

 

post-273658-0-03875600-1536444569.jpg

Venus 2017-01-30 09:47 UTC, 32˚ elevation
Canon 55-250mm f/4-5.6 Mk1 @ 250mm f/8
Canon T3i RAW stack (5×1/2000s@ISO100)
Scale = 2.2ppAd (λ = 536nm)
Outback Northern Territory, Australia

 

It's a capable lens, albeit a quite slow for handheld AP at f/4.5. My go-to lenses for AP are now my Sigma 8-16mm f/4.5-5.6, my Canon 50mm f/1.8 Mk1 "Nifty Fifty", and my Canon 200mm f/2.8L II. But for best results—especially with the slower 55-250—you're going to need a motorized equatorial mount. The cheapest solution would be an Orion Adventures in Astrophotography Bundle—you'd also need to get the 2.1-lb counterweight (as the 4-lb counterweight is much too heavy for all my camera configurations). This would totally complement your intervalometer…

 

BQ



#39 BQ Octantis

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Posted Yesterday, 05:27 AM

Ok, Nicole, you inspired me to reprocess one of my very first successful DSO shots—the Eta Carina Nebula through the 55-250—just to show you what the lens is capable of on a tracking equatorial mount:

 

Carina Nebula Reprocessed

Carina Nebula 2017-05-24, 51˚ elevation
Canon 55-250 f/4.5-5.6 @ 250mm f/5.6
Canon T3i (stock), Generic EQ2 mount
11×30sec@ISO3200, 100×bias, 100×darks
Aligned & stacked in Lynkeos v3.1
Processed in Photoshop CS5 w/
Annie's Astro Actions 7.0 & Astronomy Tools v1.6
Scaled to 29%, cropped to 927×1002

Tropic of Capricorn, Northern Territory, Australia

 

This was just 5 minutes of integration…

 

BQ


Edited by BQ Octantis, Yesterday, 06:18 AM.



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