Observing - what did you see tonight?

With what did you observe?

Discuss celestial objects and phenomena outside the Earth's atmosphere, Earth-launched satellites and exploratory missions, etc....

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Re: Observing - what did you see tonight?

#81  Postby theropod » Apr 14, 2017 2:51 pm

IMG_4591.JPG
DIY Barn door tracker
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The tracker I built is centered around diamond plate aluminum about 3/16" thick with a piano hinge at the pivot point. The drive rod is 1/4" X 20 allthread and the bend matches the radius arc to within <1/16" across its entire length. This drive rod is guided through a nylon bushing to control lateral and end slop. The 2 X 4 is a select white spruce with very little warp or twist, and attached to the plastic drum with self tapping screws to the rigid section of the thick ring around the top of the drum. When I feel better a good coat of dark exterior latex house paint be applied which will prevent weathering. I used 3/8" allthread sections for fine alignment adjustments in the elevation alignment with Polaris and for east/west centering. My Polaris alignment scope is a 2.5 X 9 rifle scope with an LED to illuminate the reticule, and has been adjusted to remain centered throughout the entire travel of the tracker. For leveling I used my 4 foot level across both axis and any settling in the barrel can be tuned with wedges between the drum and the mount by loosening the mounting screws and retightening after adjustments. To make sure there is no twisting motion in the drum a steel post is driven into the ground with a ratchet strap securing them firmly together. My phone mount is also a DIY affair made from a modified 2" PVC coupler and two golf balls to provide pivot points. The phone mount is a part of an old security light and some soft aluminum heat sink with fingers which grip the phone quite securely. In the attached image, which I had to hobble around on my crutches to take, one can get a feel for my efforts. The Arduino driver and stepping motor are not attached in this image, but I have tested the rate of expansion to less than 2 seconds difference over a 52 minute run. The main drive gear rotates one turn per minute, and both it and the gear attached to the stepping motor are salvaged from a dead VCR. The drive gear has a nut matching the allthread expoxied to the center as is the motor gear. Both are nylon with fine teeth. A rubber band holds the motor gear to the drive gear to ensure no slipping or jumped cogs. The motor is mounted to a bracket made from 90° aluminum and is held to the bottom plate via a single small bolt with flat washers between to allow small movement without binding. Had I not broken my ankle I had planned on using the tracker well before now, but it awaits me when I heal.

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Re: Observing - what did you see tonight?

#82  Postby crank » Apr 14, 2017 3:11 pm

I've had a long term obliviousness to what the hell 'ISO' meant when applied to digital cameras. I've watched a few videos and they all seemed to be more confused than I was. One guy said that at high ISO, the 'camera added light'. The last one I watched has decent info, but spent about 3x longer than needed. The important bits were about how ISO is attempting to shift the relationship of the light levels hitting the sensor and range available form the digital signal. It wasn't until the last minute that he said 'ISO is sometimes called gain". BINGO. So, it's gain, that's easy enough to understand without all the 13 minutes before.

However, that isn't the whole story. Pardon if I make a mess of some of the terms, haven't had to deal with in a while, but there are 2 factors that need taking into account. They could be thought of as a DC level and an AC gain. Alternatively, black level and gain--the setting that determines what range of light level falling on sensor will cause the sensor to output its full range, e.g., a 16 bit sensor range of 0000-FFFF in hex.

I assume ISO was chosen to make some kind of adjustment that was calibrated to f-stop steps to aid in how photographers think vs the tech-geeks like me. That still isn't the whole story. The way film works is the higher the ISO, the less light it takes to give a given level of exposure, I assume the available contrast is roughly similar, meaning the range of light level that gives black vs white is the same. This is a DC offset equivalent, not a gain, And I think that's the same on digital cameras, the sensor chips have a given dynamic range, so ISO is shifting the 'black level' way down so lower light levels will give 'white'. But the electronics add the complication of 'gain', which can dick with the light level vs digits out relationship in all kinds of ways, like 'gamma' which I don't want to get into.

OK, too much TLDR, bottom line, what the fuck does ISO actually do? I'm still not sure, and most sources I've looked to seem more confused than I am. One thing I'm sure of, that could still be wrong, is that it isn't really much akin to the ISO of film.
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Re: Observing - what did you see tonight?

#83  Postby crank » Apr 14, 2017 3:14 pm

theropod wrote:
IMG_4591.JPG


The tracker I built is centered around diamond plate aluminum about 3/16" thick with a piano hinge at the pivot point. The drive rod is 1/4" X 20 allthread and the bend matches the radius arc to within <1/16" across its entire length. This drive rod is guided through a nylon bushing to control lateral and end slop. The 2 X 4 is a select white spruce with very little warp or twist, and attached to the plastic drum with self tapping screws to the rigid section of the thick ring around the top of the drum. When I feel better a good coat of dark exterior latex house paint be applied which will prevent weathering. I used 3/8" allthread sections for fine alignment adjustments in the elevation alignment with Polaris and for east/west centering. My Polaris alignment scope is a 2.5 X 9 rifle scope with an LED to illuminate the reticule, and has been adjusted to remain centered throughout the entire travel of the tracker. For leveling I used my 4 foot level across both axis and any settling in the barrel can be tuned with wedges between the drum and the mount by loosening the mounting screws and retightening after adjustments. To make sure there is no twisting motion in the drum a steel post is driven into the ground with a ratchet strap securing them firmly together. My phone mount is also a DIY affair made from a modified 2" PVC coupler and two golf balls to provide pivot points. The phone mount is a part of an old security light and some soft aluminum heat sink with fingers which grip the phone quite securely. In the attached image, which I had to hobble around on my crutches to take, one can get a feel for my efforts. The Arduino driver and stepping motor are not attached in this image, but I have tested the rate of expansion to less than 2 seconds difference over a 52 minute run. The main drive gear rotates one turn per minute, and both it and the gear attached to the stepping motor are salvaged from a dead VCR. The drive gear has a nut matching the allthread expoxied to the center as is the motor gear. Both are nylon with fine teeth. A rubber band holds the motor gear to the drive gear to ensure no slipping or jumped cogs. The motor is mounted to a bracket made from 90° aluminum and is held to the bottom plate via a single small bolt with flat washers between to allow small movement without binding. Had I not broken my ankle I had planned on using the tracker well before now, but it awaits me when I heal.

RS

:thumbup:
Pretty cool. Wanta build a trebuchet for me? There's a great new design I came across recently and I don't have the time [or ability or patience].
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Re: Observing - what did you see tonight?

#84  Postby felltoearth » Apr 14, 2017 3:18 pm

theropod wrote:
IMG_4591.JPG


The tracker I built is centered around diamond plate aluminum about 3/16" thick with a piano hinge at the pivot point. The drive rod is 1/4" X 20 allthread and the bend matches the radius arc to within <1/16" across its entire length. This drive rod is guided through a nylon bushing to control lateral and end slop. The 2 X 4 is a select white spruce with very little warp or twist, and attached to the plastic drum with self tapping screws to the rigid section of the thick ring around the top of the drum. When I feel better a good coat of dark exterior latex house paint be applied which will prevent weathering. I used 3/8" allthread sections for fine alignment adjustments in the elevation alignment with Polaris and for east/west centering. My Polaris alignment scope is a 2.5 X 9 rifle scope with an LED to illuminate the reticule, and has been adjusted to remain centered throughout the entire travel of the tracker. For leveling I used my 4 foot level across both axis and any settling in the barrel can be tuned with wedges between the drum and the mount by loosening the mounting screws and retightening after adjustments. To make sure there is no twisting motion in the drum a steel post is driven into the ground with a ratchet strap securing them firmly together. My phone mount is also a DIY affair made from a modified 2" PVC coupler and two golf balls to provide pivot points. The phone mount is a part of an old security light and some soft aluminum heat sink with fingers which grip the phone quite securely. In the attached image, which I had to hobble around on my crutches to take, one can get a feel for my efforts. The Arduino driver and stepping motor are not attached in this image, but I have tested the rate of expansion to less than 2 seconds difference over a 52 minute run. The main drive gear rotates one turn per minute, and both it and the gear attached to the stepping motor are salvaged from a dead VCR. The drive gear has a nut matching the allthread expoxied to the center as is the motor gear. Both are nylon with fine teeth. A rubber band holds the motor gear to the drive gear to ensure no slipping or jumped cogs. The motor is mounted to a bracket made from 90° aluminum and is held to the bottom plate via a single small bolt with flat washers between to allow small movement without binding. Had I not broken my ankle I had planned on using the tracker well before now, but it awaits me when I heal.

RS


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Re: Observing - what did you see tonight?

#85  Postby theropod » Apr 14, 2017 4:05 pm

Well, I cannot take credit for the tracker design as several versions can be found on the net. My implementation is a result of attempting to mount this to my old Silk tripod, which was far too sloppy to remain stable as a mere bump required realignment to Polaris. This contraption should stay stable unless we have an earthquake, and be realigned in minites even then. My first vesrion used plywood for the plates and those were entirely too flexible. Also I attempted to use discreet components to drive a unipolar stepping motor, which was not accurate no matter what adjustments were made to the 555 timers. That driver used two 555 timers to generate the pulses which were then fed to a 4017 sequencer/decade counter and those in turn to a 2003 darlington array. The Arduino is deadly accurate in timing and remains so with supply voltage variations as I power it directly from my off grid batteries. My current design should remain stable both mechanically and electronically across temperature swings as well. I am working on a cover which will allow me to leave the drive electronics attached in any weather. As of now I have to remove those parts and reattach them with each use. I cannot wait until I am able to actually use it!

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Re: Observing - what did you see tonight?

#86  Postby theropod » Apr 14, 2017 4:24 pm

As far as the ISO stuff goes I can't say I grasp it well either. What I know is that if I crank the ISO up the graininess becomes obtrusive. For the work I am doing I usually set the ISO between 800 and 1,000 with the white balance around 3,000. Higher white balance numbers results in blueish images and lower in red tints. If I am going for a long exposure, like the one hour star trails shot, I lower the ISO number.

I have seriously considered build a trebuchet for some time! We live on a fairly steep hillside and it would be big fun to hurl stuff down the hillside! By stuff I mean pumpkins and the like. Nobody lives below us and we own the land for 440 yards downhill. When the local coyotes start their nightly singing session it would be great fun to drop a rotten melon in their midst.

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Re: Observing - what did you see tonight?

#87  Postby crank » Apr 14, 2017 5:34 pm

At least some cameras will tie a group of pixels together, read out as one, and this is the likely source of the 'graininess' you're getting, similar to how the grains are actually larger in faster film, which is also grainier.

The trebuchet I want to build would let you drop at least a whole crate of melons in a midst far far away. Shooting downhill is a bit of a cheat, but if that's what you have to work with, no worries. This is the first video where I stumbled on this new sliding trebuchet design. There's tons of videos about them if you search. It's definitely awesome and I must have one.

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Re: Observing - what did you see tonight?

#88  Postby theropod » Apr 14, 2017 5:46 pm

Nice! Yeah, I want to build a siege engine type maybe using a barrel of sand as a counterweight.

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Re: Observing - what did you see tonight?

#89  Postby crank » Apr 14, 2017 5:47 pm

Wow, there's another one I missed, the MERLIN
Image
FLoating arm, the video above is one of these, I'm not sure how it compares to sliding ???
Image

I think they're the same


There probably should be a thread or three devoted to trebuchets, but I ain't gonna start one, I'd end up spending too much time on it
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Re: Observing - what did you see tonight?

#90  Postby theropod » Apr 14, 2017 8:34 pm

IMG_0053.JPG
Fighter High G Turn
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Among the odd things I have captured during my meteor watching is this. Some branch of the US Air Force was out playing late one night last summer and one of the fighter planes turned on his landing lights and made a hi G turn and then turned those lights off again. One could hear the engines of their planes going full throttle and then near silent and back in just a matter of seconds. This little turn lasted less than two seconds and was the only time I saw either plane. I only know there were at least two planes by the sounds as they would engage and then break apart and repeat the game. While I can't be sure I think these planes were operating well above the normal altitude of commercial jets.

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Re: Observing - what did you see tonight?

#91  Postby theropod » Apr 14, 2017 8:49 pm

IMG_0196.JPG
Satellites in Formation
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Again from the oddity files. Here is an image of something I have not seen before or since. These are the tracks of two satellites flying in close formation. I have no idea what reason there could be for this, but they were definitely tracking the same direction and speed with a fixed distance between each other. This image was taken looking almost due east at about 45°from level.

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Re: Observing - what did you see tonight?

#92  Postby theropod » Apr 16, 2017 9:13 pm

IMG_6953.JPG
Missile Command
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A plane and a satellite on what appears to be a collision course, or a scene from the old game Missile Command.

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Re: Observing - what did you see tonight?

#93  Postby Weaver » Apr 16, 2017 9:35 pm

Friday night I observed a truly amazing meteor - path across the sky at least 10 degrees, and significantly brighter than nearby Jupiter - at least a few magnitudes brighter.

Totally chance observation - got out of a car and turned toward the steps, glanced toward the sky while climbing four steps and BAM - there it was, and then gone.

Track originated near the zenith and progressed downwards towards the South.

Brightest one I've seen in a very long time.
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Re: Observing - what did you see tonight?

#94  Postby theropod » Apr 16, 2017 10:59 pm

Weaver wrote:Friday night I observed a truly amazing meteor - path across the sky at least 10 degrees, and significantly brighter than nearby Jupiter - at least a few magnitudes brighter.

Totally chance observation - got out of a car and turned toward the steps, glanced toward the sky while climbing four steps and BAM - there it was, and then gone.

Track originated near the zenith and progressed downwards towards the South.

Brightest one I've seen in a very long time.


Cool! Persistent trail? Color shift of fireball? Did it seem to originate from a northeatern direction? Breakup before dispersing?

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Re: Observing - what did you see tonight?

#95  Postby Weaver » Apr 17, 2017 2:44 am

Only very slight persistence on the trail if at all. Extremely white fireball, no colors - markedly whiter than Jupiter or Venus ever are. Trail was within about 10 degrees of North to South, originating at the zenity. No breakup at all - just fucking bright appearance, zipped along for a large fraction of a second, then gone.
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Re: Observing - what did you see tonight?

#96  Postby crank » Apr 18, 2017 11:43 pm

I think possibly the brightest meteor I ever saw was while driving north on I35 from San Antonio towards Austin. It was close to a town, and I kinda saw over some of those big gre3en signs they use for freeways, I assume this is fairly similar for the US. The signs were't all that close, but there was of course a lot of traffic coming the other way on the freeway and quite a few bright lights from the town, and it was directly in front of me--saw it through the upper half of the windshield, very bright looking despite all the other light. I only saw it briefly, I can only wonder how bright it would have looked if it was in dark skies and my eyes dark adapted. It was enough of a display, I was sure it would make the papers and it got a brief mention in The Austin American-Statesman.
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Re: Observing - what did you see tonight?

#97  Postby theropod » Apr 24, 2017 1:19 pm

Last night was clear and I hobbled out to try to catch a meteor. While I did manage to grab one tiny meteor I saw one that was awesome. While not particularly bright the meteor covered half the sky, and was insanely fast. It entered the atmosphere from the almost due east and on a very flat trajectory, which may be why it lasted so long.

I used my barn door tracker for the first time, and while it worked well it still needs some adjustments. I am either driving the actuator at the wrong speed, and or my alignment to Polaris is off. Still, the attached image is a 5 minute exposure, and is another documentation of the paired satellites I posted upthread. The cheap rifle scope I used as a Polaris alignment tool has suffered from moisture penetration and was completely clouded so I eyeballed this critical part along the hinge edge, and I am sure most of the issues lie there.

I like how these passed through the cup of the Big Dipper.

IMG_4835.JPG
Paired Satellites
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Posible origin of these paired satellites.
http://www.sciencedirect.com/science/ar ... 6513000805

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Re: Observing - what did you see tonight?

#98  Postby theropod » Apr 25, 2017 1:28 pm

IMG_4843.JPG
Paired Satellites 3
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IMG_4852.JPG
Paired Satellites 4
IMG_4852.JPG (1.03 MiB) Viewed 482 times


Having another night of clear skies I went back out last night. No big meteors, but these paired satellites came through again, and this time there was another distinct pair on a different trajectory. The first pair followed almost the same path as the night before, but the second pair are obviously another set as they were clearly tracking southwest instead of southeast.

I pushed the exposure time out to seven minutes in these shots. Basically I am just tuning the tracker little by little in hopes of having it capable of crisp 10 minute shots when the Perseids roll in in August.

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Re: Observing - what did you see tonight?

#99  Postby theropod » May 07, 2017 9:09 pm

IMG_4976.JPG
Frozen Lightening
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A 5 minute tracked shot of Ursa Major. High thin clouds. A firefly very near my iPhone. Taken Friday before midnight.

IMG_5055.JPG
A Small Flash
IMG_5055.JPG (190.99 KiB) Viewed 438 times


Another tracked shot of Ursa Major, but with a sparkling litte meteor. To the eye this looked like a flash with no trail but the phone caught the slightest hints. I suppose this is a small bolide I can add to my collection.

My home brew barn door tracker is/was still running a little slow, so I brought the Arduino back inside and reprogramed it to run another 1% faster. Tonight, even with the waxing moon I hope to test my little Arduino tracker again. Last night I zoomed in the maximum allowed in NightCap Pro of 8X and took two shots of an eastern star. One shot with, and one without, tracking. While the Arduino was still running slow it wasn't bad. The good part is that my polar alignment seems really close as the trailing in both the tracked and non tracked trails follow the exact same arc.
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Re: Observing - what did you see tonight?

#100  Postby The_Metatron » May 08, 2017 5:48 pm

I really like that firefly.
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