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Is aperture still king even during the day?

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#26 Hikari

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Posted 30 November 2013 - 01:51 PM

The iris has to be at a specific point in the optical path. If the iris is at an image plane, then it is what is called a field stop and the field of view will narrow. If the iris is at a pupil, exit or entrance, it will control the effective aperture of the system--this is known as an aperture stop and makes the image darker without changing FoV.

If you have your iris somewhere between a pupil and an image plane, then you get a bit of both. What you mostly see is a vignetting effect as the edges of the stop are darkening.

#27 snorkler

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Posted 01 December 2013 - 03:16 AM

Scope review FYI. It compares spotting & astronomical scopes.

#28 mooreorless

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Posted 01 December 2013 - 08:32 AM

Talking about the TeleVue 85. And what is this using 75x to 150x with this scope, I thought that was impossible from what I have read on this thread. Eight pounds is a challenge? :foreheadslap: Give me a break.

"Weighing in at more than eight pounds, this behemoth was a challenge just to get out of the back seat of my car."

#29 snorkler

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Posted 01 December 2013 - 06:49 PM

75-150X daytime conditions are as rare as 600-900X nighttime conditions.

Birders don't just haul their scopes from their cars to the lakeshore. They often have to carry their scopes all the way around the lake.

#30 mooreorless

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Posted 01 December 2013 - 08:28 PM

You are the one that posted the link. I read it and this person thinks 8lbs. is a challenge just to get out of a vehicle, they better take a Nikon 50ED. I agree that is a lot of magnification, but it does show sometimes you can use more than the 60x and it might be more times than you folks think.

BTW thanks for posting the link.

#31 snorkler

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Posted 03 December 2013 - 12:53 AM

You're welcome, Steve. Your seeing conditions may be different where you live, but my daytime experience with scopes at the target range and birding is this: Once you're past mid-morning, your useful upper magnification limit is 30-40X far more often than it's 60X.

I'm speaking from nearly 50 years of experience using spotting scopes. YMMV.

#32 mooreorless

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Posted 03 December 2013 - 12:47 PM

My place 2.8 miles away Ok I agree that 30x-40x is probably the most used magnification in spotting scopes for conditions. A lot of it depends on how far away you want to look as well.

#33 edwincjones

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Posted 10 December 2013 - 03:43 PM

aperture is still king-day and night
but one has to ask if
care and maintance of the king
is worth the cost in money and effort

edj

#34 curiosidad

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Posted 10 December 2013 - 04:08 PM

It is good, edj!!!

#35 Tamiji Homma

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Posted 12 December 2013 - 05:50 PM

The American flag on the hill was down for a while but it is back this morning. So I decided to take photos.

Here is experiment of daytime images. The photos are taken with Fuji X-Pro1 camera.

The target is American flag on top of the hill, about 2Km away, temperature 64 degree F, slight wind on the ground. As you can see, it has more wind up on the hill. They are not shot back to back so conditions vary but it mostly represents what I see.

Visually (looking through eyepiece), it is hard to see more proportional to aperture due to simmered air by heat and wind. When wind stops and air gets stable, it is very obvious larger aperture shows more. It happens a few times a year, at most half an hour each day, usually early evening here. You can use 200x and I can spot ants on the American flag :)

Swarovski spotting scope ATX95@70x + TLS APO adapter, through eyepiece:
Full size: http://www.pbase.com...46/original.jpg
Posted Image

Swarovski spotting scope ATX95@30x + TLS APO adapter, through eyepiece:
Full size: http://www.pbase.com...49/original.jpg
Posted Image

Takahashi FS-60Q + ExtenderQ 1.6x f/16, prime focus, focal length 960mm:
Full size: http://www.pbase.com...51/original.jpg
Posted Image

TMB 130SS f/7, prime focus, focal length 910mm:
Full size: http://www.pbase.com...54/original.jpg
Posted Image

WO FLT 152 f/8, prime focus, focal length 1200mm:
Full size: http://www.pbase.com...54/original.jpg
Posted Image

Tammy

#36 KennyJ

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Posted 12 December 2013 - 06:16 PM

Thanks for making the effort to take those photos and post them here, Tammy.

Although realising it's the best we can do, by their very nature, the precise moment/conditions/photographer/and camera(s)used inevitably contribute in at least some small part to the images we see.

To MY eyes, both in the reduced and full sized images, the TMB 130SS f/7, prime focus, focal length 910mm shot provides by some margin the most satisfying and informative image.

So, my summary based upon these examples is that although obviously of some significance, APERTURE ALONE does NOT trump sheer optical QUALITY.

Kenny

#37 Tamiji Homma

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Posted 12 December 2013 - 06:51 PM

Hi Kenny,

single exposure of the daytime image is difficult to know what it really looks like.

I also shot video when I took the photos. I am going to upload them when I get a chance. The video shows more, not detail but how you would see in eyepiece, I think.

I'll post video link later.

Tammy

#38 KennyJ

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Posted 12 December 2013 - 07:05 PM

Thanks, Tammy.

It's after midnight here now, so I'm off to bed.

Looking forward to any future posts in this thread!

Kenny

#39 Tamiji Homma

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Posted 12 December 2013 - 07:57 PM

I uploaded the video files to YouTube.

FS60Q+ExtenderQ 1.6x, 960mm:
http://youtu.be/ciweU29lG0M

Swarovski ATX 95@70x:
http://youtu.be/sxg220mKMSU

TMB 130SS f/7, 910mm:
http://youtu.be/w1bi-9gU-7A

WO FLT 152 f/8, 1200mm:
http://youtu.be/hnD01phkJY4

Tammy

#40 Jobryant

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Posted 12 December 2013 - 11:31 PM

Thanks for taking the time to make and post up those videos Tammy. It was much easier for me to see a difference with the videos compared to the pictures.

#41 snorkler

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Posted 13 December 2013 - 01:02 AM

I agree with Kenny that the TMB130 still photo shows the most detail. But looking at the heat wave distortion in all the videos, I think the TMB130 photo was a lucky catch between shimmers. There was simply too much heat wave distortion that day preventing acceptable views of birds/details.

#42 KennyJ

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Posted 13 December 2013 - 03:39 PM

I was very disappointed with the videos of both the larger scopes. The first few moments were stunningly glorious through both, then it seemed to lose focus completely for almost all of the remaining minute or so.

Quite apart from the "shimmering" or effects of mirage, I found the "gentle wavering" caused by the video camera reminiscent of what it is I DON'T like about Canon Image Stabilised binoculars.

I repeat though that in the still photos, I remain extremely impressed by apparent quality of the TMB optics.

Kenny

#43 mooreorless

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Posted 13 December 2013 - 04:15 PM

I'll take the WO 152 in the video. I liked the birds.I have to agree with Darrell the TMB 130 was/might of been a lucky catch between heat waves. This was all very interesting, thanks Tammy for doing this, I can just imagine the time you have in this!!

#44 Hikari

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Posted 13 December 2013 - 08:18 PM

But you are really not comparing just the entrance pupils with your images, you are also comparing exit pupils. The smaller the exit pupil, the greater the diffraction and so lower resolution. Comparing an f/7 image to an f/16 image and trying to make a determination about the effect of the entrance pupil is far from ideal. You really cannot make a conclusion.

#45 Hikari

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Posted 13 December 2013 - 08:25 PM

The angular size of the entrance pupil is proportional to the resolution at the subject plane. The angular size of the exit pupil is related to the resolution at the image plane.

#46 nighthound

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Posted 04 January 2014 - 09:57 AM

Got the Sky90 a few days ago and so far I like it a lot. Only bad thing is that I can't reach infinity with my modified diagonal with iris and mag switch. So unless I can figure something out to get it to reach focus with my diagonal setup the little Sky90 will probably not be replacing the 114mm which is a real bummer because I'm really digging the Tak.

I've only been able to use the Sky90 during the middle of the day and during that time I find I like the Sky90 just a bit better then my Vixen 114. Contrast and sharpness are just a hair better with the Tak and the overall view is just more pleasing to me. So far the only EP used has been a 30mm leitz and a 12mm Ortho so I have yet to push the tak to see how it performs at higher powers. The main test for me and my uses will be to see how the Tak does during dusk and dawn timeframes and how well the Sky90 will do with videoscoping.


Have you tried an extension tube with the Sky 90. I haven't needed one with my Sky 90 for astro but I do need the added distance behind the focuser with the Tak 60 and DSLR or guide cam. Won't hurt to call Land Sea & Sky and ask if it might be a solution with your diagonal.
http://www.takahashi...ww.takahashi...

#47 Jon Isaacs

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Posted 06 January 2014 - 07:47 AM

75-150X daytime conditions are as rare as 600-900X nighttime conditions.

Birders don't just haul their scopes from their cars to the lakeshore. They often have to carry their scopes all the way around the lake.


Or across a lake, through the swamp, up the mountain, down the canyon, through the brush... an 8 lbs scope like the TV-85 requires a serious mount which adds weight..

I am a weight weenie when it comes to birding. I much prefer my 60 mm spotter that weighs 6 pounds with the the tripod to my 80mm spotter that weighs nearly 5 pounds by itself..

For astronomy, I am not so worried about the weight.

Jon

#48 Jobryant

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Posted 09 January 2014 - 11:38 AM

Got the Sky90 a few days ago and so far I like it a lot. Only bad thing is that I can't reach infinity with my modified diagonal with iris and mag switch. So unless I can figure something out to get it to reach focus with my diagonal setup the little Sky90 will probably not be replacing the 114mm which is a real bummer because I'm really digging the Tak.

I've only been able to use the Sky90 during the middle of the day and during that time I find I like the Sky90 just a bit better then my Vixen 114. Contrast and sharpness are just a hair better with the Tak and the overall view is just more pleasing to me. So far the only EP used has been a 30mm leitz and a 12mm Ortho so I have yet to push the tak to see how it performs at higher powers. The main test for me and my uses will be to see how the Tak does during dusk and dawn timeframes and how well the Sky90 will do with videoscoping.


Have you tried an extension tube with the Sky 90. I haven't needed one with my Sky 90 for astro but I do need the added distance behind the focuser with the Tak 60 and DSLR or guide cam. Won't hurt to call Land Sea & Sky and ask if it might be a solution with your diagonal.
http://www.takahashi...ww.takahashi...


I need more of both in-focus and out-focus with my current daytime eyepiece setup. The only way I'm going to get the Sky90 to work the way I would want it to would be to have the OTA shortened and replace the focuser.

After thinking about it a bit more and reading the responses I feel a big factor of answering this question is going to depend on how one does majority of their daytime viewing. If you're a person that views close to your vehicle or from a porch then the more aperture is probably better. For someone like me on the other hand who does a lot of hiking to get to their viewing locations then there comes a point where more aperture is just not worth it or even doable for that matter.

#49 KennyJ

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Posted 09 January 2014 - 05:45 PM

< If you're a person that views close to your vehicle or from a porch then the more aperture is probably better.

For someone like me on the other hand who does a lot of hiking to get to their viewing locations then there comes a point where more aperture is just not worth it or even doable for that matter>

Yes, I think that pretty much sums up the situation.

Kenny

#50 edwincjones

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Posted 11 January 2014 - 08:04 AM

many birders,
at least on BirdForum
seem to be going to 32mm binos

edj






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