Jupiter / Saturn conjunction - test 1

[Tulloch]

Hi there, in case you haven't heard, Jupiter and Saturn are coming together in a few weeks ;). The two planets were out last night and the night before, although last night there was a bit of cloud around which made the test difficult. I took a quick and dirty iPhone image, and also imaged the two planets separately with my C9.25, f/0.63 reducer and ASI224MC but using the same camera settings to see how it would go. I set the maximum histogram level for Jupiter to be up around 90%, which still left some dynamic range for Saturn. These were taken at an elevation of around 22 degrees each, which is similar to where they could be visible at conjunction, weather permitting.

Stacked in AS!3, sharpened in Registax, then combined together manually to simulate their approximate positions on Dec 21. This was just focusing on the planets, I didn't really try for the moons this time. This test shows that it should be possible to get a reasonable representation of the two planets with my setup. Not a lot of detail expected on the planets, but some there to be sure.

In order to get the locations, I used a time of 9:11 PM on 21 Dec local time, which is 2020-12-21-10:11 UT, which I figured was as good a time as any (and matched the time I used for the test images above). The image with the SS overlay is attached.

Sky Safari reports a separation of 6' 30.8" at around that time at my location. On the last image shown attached (before I scaled it by 50% to fit on IIS), Jupiter was 67 pixels in diameter, the separation is 810 pixels - approximately 12.1 Jupiter diameters. The original image in the first post shows them separated by 12.7 Jupiter diameters - close enough for government work :lol:

Andrew

[pmrid]

Andrew, thanks for your post. Could you please expand a bit on your histogram setting at 90%.
Peter

[Tulloch]

Sure - I adjusted the gain setting on my camera so that the maximum value shown in FireCapture when imaging Jupiter was 90% of maximum. I then used the same gain level when I slew across to Saturn and took a video with the same settings.

I did this to get some sort of idea as to the relative brightness levels between the two planets when I have to capture them at the same time.

[pmrid]

Thanks for that. You have put your finger on the problem I’m trying to confront - imaging both planets in the same frame when there is such a difference in their relative luminosity. Most of the planetary image capture programs I’ve looked at seem to have very sophisticated routines designed to image single planets but two in one frame is another matter.

It’ll be a very interesting half hour or so - particularly because I’ll be setting up in daylight and will need to polar align and then to locate the planets in semi-twilight.

[glend]

Just shoot two sets of subs, one exposed for Jupiter and one for Saturn, then you layer them in Photoshop in processing. Typically you wouild mask over one target off the other. Same technique that is used for processing M42, to bring out the Trapezium detail without blowing the core when exposing to bring out the detail in the gas nebula. Of course, this is a traditional sub approach to imaging, and not high frame rate stacking for planetary, but the same concept should work for capture, just shoot two videos, one for Saturn and one for Jupiter, you take the two final images and layer mask.

[Tulloch]

Sure, that's possible (and in fact it's kinda what I did here), but that's not really the point is it :)

[multiweb]

I used a DSLR for the Venus/Jupiter closeby in June 2015 and different exposure times. I think it was a tad wider than the Saturn/Jupiter distance will be but ball park same fov. I have a composite here (https://onedrive.live.com/?authkey=%21ACnUIS%5FstUVCu%2Ds&cid=6930D3AD12D5044C&id=6930D3AD12D5044C%211539&parId=6930D3AD12D5044C%211252&o=OneUp)