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Old 19-11-2020, 08:56 PM
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pmrid (Peter)
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Imaging the Jupiter Saturn conjunction

Iím planning to image this event - on December 21st. I have been trying to decide which combination of scope and camera will work best. I will have to use a portable rig - I have chosen a site in a west-looking park near home - so already some limitations. It will have to be my HEQ5Pro mount. Now since the planets will be low (15-18 degrees) above the western horizon and barely 90 minutes after sunset, and it is likely to still be warm if not hot, and the seeing will be poor the choice of gear will be tricky. Do I try my ZWO290MC CCD and take videos, or try to get some still frames and hope?

Framing issues clearly favour getting both planets in the same frame. So matching scope to CCD will be the real challenge. I have a 10inch f3.8 newt of 952mm FL. But on a small mount it will probably be a bit unstable in an exposed location. Likewise my127mm refractor - another 950ish FL. I have an RC8 (1600mm FL) which is a bit heavy but less prone to instability if thereís a bit of breeze. I also have a ED80 which is light and portable. But the FL is a bare 600mm and getting a decent image of Jupiter (let alone Saturn) would be difficult.

I have the usual mix of old EOS 20D, 40D and even a 500D plus a great Olympus OMD EM1. and an SBIG STF8300M and an older 4MP Starlight Express SXVR H16.

Spoilt for choice. I won't be able to get both planets in frame AND get a decent image scale so I will have to sacrifice one or the other. And I think image scale loses out. So I think my rig of choice will be the RC8 and the SBIG STF8300.

There wonít be time to take multiple filters. Iím going to have to image in one colour - probably green I think. Iíd be interested to see what the experts think though.

Peter
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Old 23-11-2020, 07:23 AM
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doppler (Rick)
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Hi Peter, the other difficulty to get around will be the large difference in brightness between the two objects. Jupiter will be overexposed to get Saturn exposed correctly and Jupiter's moons should be about the same exposure as Saturn. I will be taking various exposures and then blending 2 together in PS.

Rick
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Old 23-11-2020, 08:20 AM
glend (Glen)
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Yeah i think the technique used to properly expose Orion (M42) would work well, which is two separate sub sets, one longer one to allow capture of the nebulosity cloud, and a short one to capture the Trap detail before it burns our. Then use Photoshop layer masking to blend them together; perhaps even dialing down Jupiter's Opacity if required. There are a fair number of Orion Processing tutorials on Utube that you can work on right now to perfect the technique, for those new to the concept. Of course those two planets are much brighter than Orion's gas cloud, so the exposure differences would not need to be that large (as Orion's).
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Old 23-11-2020, 08:02 PM
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Thanks Rick and Glen. Iíve settled on using my RC8 with a ZWO ASI290MC which is a 2MP sensor, USB3 supporting a high frame rate so I can vary the exposure duration and gain to get the settings to work with both planets. The problem will be with the very short window of opportunity and having to run off big enough video grabs. I want to be able to work with at least 10K frames for each. The irony is, of course, that weíll probably have stormy weather and Iíll have nothing to do but console myself withXmas cheer.
Peter
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Old 23-11-2020, 10:23 PM
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multiweb (Marc)
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There's going to be only an hour or so between the sunset and the planets being too low. The sky will be probably quite bright so you'll need to be quick. Best to get everything in one field rather than trying to mosaic. I don't think there will be enough time for this. I reckon a FL of 1m or a refractor barlowed x2 would be perfect. Color would be hard. Mono or IR better given the altitude and the sky brightness.
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Old 23-11-2020, 11:30 PM
glend (Glen)
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I have just been looking at Sky Safari for the night's prior to the conjunction, and there seem to be good opportunities to do some test imaging leading up to the actual conjunction on the 21st. Saturn and Jupiter are very close for a number of nights prior, and certainly can be captured in a single field shot, which could be useful for practicing your exposures. Also you can grab them at a slightly higher altitudes it would seem. Check out Sky Safari, or Stellarium or whatever you use for dates like the 17th. On Thursday the 17th at 8:55pm they are at 15 degrees altitude and already close enough in my opinion to get a good image of the two in the same frame, they seem to be less than 1 degree apart based on Sky Safari data. Maybe don't worry about the actual conjunction shot and go for getting them both in the same frame, which is pretty unique in itself.

Last edited by glend; 23-11-2020 at 11:41 PM.
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Old 24-11-2020, 06:23 AM
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Quote:
Originally Posted by glend View Post
I have just been looking at Sky Safari for the night's prior to the conjunction, and there seem to be good opportunities to do some test imaging leading up to the actual conjunction on the 21st. Saturn and Jupiter are very close for a number of nights prior, and certainly can be captured in a single field shot, which could be useful for practicing your exposures. Also you can grab them at a slightly higher altitudes it would seem. Check out Sky Safari, or Stellarium or whatever you use for dates like the 17th. On Thursday the 17th at 8:55pm they are at 15 degrees altitude and already close enough in my opinion to get a good image of the two in the same frame, they seem to be less than 1 degree apart based on Sky Safari data. Maybe don't worry about the actual conjunction shot and go for getting them both in the same frame, which is pretty unique in itself.
Yes, I had given that thought too. I was reminded of that adage that goes "The perfect is the enemy of the good." And on that basis, perhaps getting some images in the day or so preceding the 21st may be a "good" idea.

Peter

Last edited by pmrid; 24-11-2020 at 12:21 PM.
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Old 24-11-2020, 07:52 AM
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I'll be starting from the 17th, when the moon is close and then tighten the field of view as the two planets get closer. I will have a go at some daytime shots as well, Jupiter is bright enough not sure about Saturn though. Hopefully the weather is kind here, the wet season hasn't started yet but afternoon clouds are becoming the norm.
Rick
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Old 24-11-2020, 10:34 AM
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Day time images are worth a shot. Sounds like real challenge though. I have imaged Jupiter near the meridian previously but not Saturn.
If you can make this work then you could try for the closest approach point for this conjunction. I think this is about 10am on the 22nd. The separation will be down to 6.25 arc seconds.
I am not going to try imaging this conjunction. Rather I am setting up for day time, twilight and early evening visual observing just to enjoy and commit the event to memory.



Quote:
Originally Posted by doppler View Post
I'll be starting from the 17th, when the moon is close and then tighten the field of view as the two planets get closer. I will have a go at some daytime shots as well, Jupiter is bright enough not sure about Saturn though. Hopefully the weather is kind here, the wet season hasn't started yet but afternoon clouds are becoming the norm.
Rick
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Old 24-11-2020, 10:57 AM
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I suggest using a red filter for daytime shots, as it boosts contrast. I used a red filter during a Saturn conjunction with the Moon a few years ago and it really made Saturn pop. Great to see Saturn appear to dive into the Moon.
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Old 25-11-2020, 11:44 AM
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I'm intending on attempting a daytime capture.

should be able to have the 2x barlow and possibly have some spare space for a bit of a crop on the system.

looking in stellarium there are going to be nice moon alignments but i'm sure these will be washed out.

cheers
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Old 25-11-2020, 01:59 PM
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Quote:
Originally Posted by rustigsmed View Post
I'm intending on attempting a daytime capture.

should be able to have the 2x barlow and possibly have some spare space for a bit of a crop on the system.

looking in stellarium there are going to be nice moon alignments but i'm sure these will be washed out.

cheers
Jupiter is quite easy if it's high when the sun is setting but still up. Never tried Saturn though. That could be hard. For the moon I reckon it will be really hard to over expose and get them out of the sky glow.
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Old 25-11-2020, 09:11 PM
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Just checked on Stellarium -
the event is only 7 degrees above the horizon in the West.
I don't think a good shot is possible.
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Old 25-11-2020, 09:40 PM
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Well, Iíve been experimenting with different combinations of scopes and cameras. Iíve scrapped my plan to use my RC8 (at 1600 FL). Iím not happy with itís collimation and I havenít the time or energy to tweak it. Iíve gone instead with my BD80ED at a native 600 FL but with an eyepiece projection rig using a 20mm eyepiece and plugging my ZWO 290MC into that. My rough figures tell me Iíll have a FOV of 0.15 x 0.09 degrees. That should get both planets and a sprinkling of moons (with a bit of luck).

I am also praying to the weather gods rather a lot.

Peter
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Old 25-11-2020, 09:45 PM
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Quote:
Originally Posted by alpal View Post
Just checked on Stellarium -
the event is only 7 degrees above the horizon in the West.
I don't think a good shot is possible.
For Melbourne, perhaps something over the water in Port Phillip Bay might work, trying to miss the distant light pollution, but it's very tight: little time after sunset, low position, framing, etc ......

Best
JA
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Old 25-11-2020, 11:05 PM
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For Melbourne, perhaps something over the water in Port Phillip Bay might work, trying to miss the distant light pollution, but it's very tight: little time after sunset, low position, framing, etc ......

Best
JA



You'd get it but it would just be 2 blurry blobs.
They are not close enough to be magnified in the same frame.
Maybe I should post a Stellarium picture?
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Old 25-11-2020, 11:15 PM
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Quote:
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You'd get it but it would just be 2 blurry blobs.
They are not close enough to be magnified in the same frame.
Maybe I should post a Stellarium picture?
Not that I'm planning to image it but I too did look at it in Stellarium as part of this discussion. I could get them in the same frame at about 0.2-0.3 arcseconds/pixel (or was it 0.5?) using a bit of this and that. Now I'll need to go back and look again.

Best
JA
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Old 25-11-2020, 11:18 PM
glend (Glen)
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Folks go back to the 17th when they are higher in the sky around 8:30pm, certainly dark enough then. Forget the actually conjunction event, and be satisfied with very close.
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Old 25-11-2020, 11:20 PM
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pmrid (Peter)
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Quote:
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Just checked on Stellarium -
the event is only 7 degrees above the horizon in the West.
I don't think a good shot is possible.
I had a look at SkySafari for Frankston on the 21st December at 7.30 pmand it shows Jupiter at 23degrees plus and 12 degrees at 8.30. Still doable.

Peter
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Old 26-11-2020, 07:39 AM
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Here's a quick overlay to show the separation compared to the moon at the same fov. And one of the moon saturn conjunction from 2019. Detail would be possible with the right exposure.
Rick
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