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Mercury elongation planning tips for a newbie

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#1 sigo24

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Posted 04 May 2021 - 09:21 PM

So after searching the forums I know to try to capture my first Mercury at either eastern or western elongation for max distance from the sun. The next one is west, May 16th right after sunset. My current plan is to use my Canon EOS RP (full frame mirrorless) attached to my ED102 (FL 714mm) refractor on my EQ6-R to goto right after sunset to reduce the sun risk.

 

Plan to shoot video 1080 @ 60fps? 4k @ 30 too slow? Other settings?

 

Finally, does it ever really matter dawn vs. dusk? I have a much better western view than eastern in my front yard.

 

Just trying to take advantage of the elongation given the limited time it happens during the year.

 

Thanks for any tips in advance!

 



#2 Tulloch

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Posted 04 May 2021 - 10:05 PM

Best tip for you (as for all the planets) is to not use the internal video mode - rather record the LiveView screen using a program like BackyardEOS. Have a look at the details here.

https://www.astropix...resolution.html

 

Also, have a look at the tutorials on this website.

http://planetaryimagingtutorials.com/

 

And be careful!

 

Hope this helps.

 

Andrew

 

P.S. Although thinking about it again, since it's Mercury you are not going to see a lot of detail anyway, so it probably doesn't matter too much :)


Edited by Tulloch, 04 May 2021 - 10:08 PM.

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#3 AstroBrett

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Posted 04 May 2021 - 10:09 PM

Try shooting Mercury in the daytime when overhead. It's not hard to find with a red filter on, and once located, you are good to go.


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#4 KiwiRay

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Posted 04 May 2021 - 10:56 PM

Around May 13, the Moon will be very near Mercury, which should make it easier to find in daylight hours by first doing a rough alignment on the Moon. Finding the little planet is always the hardest part. I usually wait until the Sun is behind my neighbour's house for safety, and image during daylight so that it's still fairly high in the sky. Andrew is right, though - you're not going to get much surface detail with your scope, but you should at least get a clear look at its phase.

 

Good luck!



#5 sigo24

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Posted 05 May 2021 - 08:08 AM

Thanks for the tips! Yes safety is key for me on this. Out of curiosity would a 3x Barlow help enough for any detail when starting at 714? Stellarium doesn't even show Mercury with detail even for a C14 SCT. 



#6 KiwiRay

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Posted 05 May 2021 - 10:59 AM

I've barely captured one or two of the brightest features with a C6, but conditions need to be really good to see anything interesting with a smaller scope. Larger scopes can get some very nice images - you'll find several on here if you do a search. Your camera and scope combination will make it unlikely that you'll get anything better than a clear view of its phase.



#7 Tulloch

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Posted 05 May 2021 - 04:19 PM

I've only imaged Mercury a couple of times, most recently with my 9.25" SCT at around 5m f/l, and all I saw was some banding on the surface, which may or may not be real. I doubt very much that you will see any detail even with a 3x Barlow, but it would still be better to use it than not.

https://www.cloudyni...ury-2020-09-27/

 

Also keep in mind that Mercury will not look like what you might expect - since it's so low and so small, all you should expect to see on the screen are little fuzzy rainbows (due to atmospheric refraction) which you will need to stack and process to get it to look anything like what you expect...

 

Andrew



#8 sigo24

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Posted 05 May 2021 - 04:34 PM

Thanks everyone. This helps with expectations.



#9 dcaponeii

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Posted 05 May 2021 - 06:37 PM

So after searching the forums I know to try to capture my first Mercury at either eastern or western elongation for max distance from the sun. The next one is west, May 16th right after sunset. My current plan is to use my Canon EOS RP (full frame mirrorless) attached to my ED102 (FL 714mm) refractor on my EQ6-R to goto right after sunset to reduce the sun risk.

 

Plan to shoot video 1080 @ 60fps? 4k @ 30 too slow? Other settings?

 

Finally, does it ever really matter dawn vs. dusk? I have a much better western view than eastern in my front yard.

 

Just trying to take advantage of the elongation given the limited time it happens during the year.

 

Thanks for any tips in advance!

If you think about the ecliptic angle to the horizon you get your answer.  Near Summer solstice, the ecliptic is high in the northern hemisphere sky at that time so viewing Mercury in the west (Greatest Eastern Elongation) would be optimal.  In the early morning, the ecliptic is making a shallow angle with the eastern horizon and so not best for Greatest Western Elongation.  Things are reversed during the winter months.  Doesn't matter as much during Spring and Fall equinox times.  Everything is upside down in the Southern Hemisphere so I haven't even figured out how the tripod works down there.  (hehe)



#10 sigo24

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Posted 08 May 2021 - 11:36 PM

Update. I couldn’t image Mercury mid day today. I put on my solar filter to slew to the sun to make sure my alignment was correct. Then I used my GOTO to slew to Mercury. I tried all kinds of shutter/ISO with the solar filter removed. What did I miss?



#11 Tom Glenn

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Posted 09 May 2021 - 02:43 AM

If you think about the ecliptic angle to the horizon you get your answer.  Near Summer solstice, the ecliptic is high in the northern hemisphere sky at that time so viewing Mercury in the west (Greatest Eastern Elongation) would be optimal.  In the early morning, the ecliptic is making a shallow angle with the eastern horizon and so not best for Greatest Western Elongation.  Things are reversed during the winter months.  Doesn't matter as much during Spring and Fall equinox times.  Everything is upside down in the Southern Hemisphere so I haven't even figured out how the tripod works down there.  (hehe)

Not to get diverted on a tangent, but the angle of the ecliptic relative to the horizon at sunrise and sunset is steepest near the equinoxes, spring (sunset) and autumn (sunrise), not summer and winter.  Given equivalent elongation values, if imaging at sunrise or sunset is desired, then imaging at the appropriate equinox will place the object of interest highest in the sky.  This also has relevance for imaging the narrow crescent Moon......with spring being ideal at sunset for the waxing crescent, and autumn for the sunrise waning crescent.  For Mercury, the period between elongations amounts to several months, and so does not stay with any particular season.  


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#12 KiwiRay

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Posted 09 May 2021 - 09:04 PM

Update. I couldn’t image Mercury mid day today. I put on my solar filter to slew to the sun to make sure my alignment was correct. Then I used my GOTO to slew to Mercury. I tried all kinds of shutter/ISO with the solar filter removed. What did I miss?

Your problem was that you couldn't find Mercury? I usually look for it first in the eyepiece (after roughly aligning on the Moon or the Sun, or more precisely on Venus if I can find that first) and it can sometimes be hard to pick out from the bright background sky. To get it within the camera sensor will require a pretty accurate alignment, which might not be easy if you're aligning on a large single target like the Sun and then slewing to Mercury.

 

Keeping trying. I don't find it on every attempt either.



#13 dcaponeii

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Posted 10 May 2021 - 07:45 AM

Not to get diverted on a tangent, but the angle of the ecliptic relative to the horizon at sunrise and sunset is steepest near the equinoxes, spring (sunset) and autumn (sunrise), not summer and winter.  Given equivalent elongation values, if imaging at sunrise or sunset is desired, then imaging at the appropriate equinox will place the object of interest highest in the sky.  This also has relevance for imaging the narrow crescent Moon......with spring being ideal at sunset for the waxing crescent, and autumn for the sunrise waning crescent.  For Mercury, the period between elongations amounts to several months, and so does not stay with any particular season.  

I did a little digging because your answer sounded a bit odd to my way of thinking.  With the position of the sun defining the ecliptic on the summer solstice with the Sun furthest north (for northern hemisphere) does not the ecliptic make it's steepest angle to the horizon?  Given your long standing accuracy I'm going to go with your reply but I've got to go back and review the geometry of the situation.  So digging into it a little bit, it appears that the angle between the ecliptic and the horizon doesn't change much at all through the seasons.  As the sun moves North and then South of the celestial equation the Earth's axial tilt defines the angle to the horizon so except for small perturbations since that angle remains the same throughout the year the angle with the horizon remains approximately constant as well.  I was wrong in my assumption regarding the ecliptic angle to the horizon.  I need to think some more about Mercury itself since it stays so close to the horizon and how that impacts visibility.  It certainly seems to me that the ecliptic orientation is the root of "favorable" and "unfavorable" Mercury elongations.  But at the moment I need to go give a final exam so this will have to wait.



#14 dcaponeii

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Posted 10 May 2021 - 08:09 AM

Not to get diverted on a tangent, but the angle of the ecliptic relative to the horizon at sunrise and sunset is steepest near the equinoxes, spring (sunset) and autumn (sunrise), not summer and winter.  Given equivalent elongation values, if imaging at sunrise or sunset is desired, then imaging at the appropriate equinox will place the object of interest highest in the sky.  This also has relevance for imaging the narrow crescent Moon......with spring being ideal at sunset for the waxing crescent, and autumn for the sunrise waning crescent.  For Mercury, the period between elongations amounts to several months, and so does not stay with any particular season.  

A quick search after the final exam got started yielded this paper.

Mercury Elongation.png

 

This figure from the paper yields the result that I also presumed for favorable and unfavorable elongations.  As you can see the angle to the horizon is largest at the equinoxes as you correctly identified.  I'll have to quit teaching Astronomy (or think a bit more before writing responses.

Mercury Elongation diagram.png



#15 sigo24

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Posted 10 May 2021 - 03:01 PM

Great information everyone! Yes, KiwiRay I was not able to see or image Mercury after slewing from the sun. I’m not exactly sure why but will keep trying. I refuse to use the eyepiece due to safety for my first viewing.

Any recommendations on shutter/iso for mid day?

Edited by sigo24, 10 May 2021 - 03:03 PM.


#16 Tulloch

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Posted 10 May 2021 - 06:52 PM

Personally I would not attempt imaging Mercury at midday, especially for a first attempt. Much better to wait until dusk (IMHO).



#17 KiwiRay

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Posted 10 May 2021 - 07:58 PM

Mercury is so low at dusk, the result is unlikely to be worth it. You also need a pretty clear view of the horizon, which many of us don't have. I like mid-late afternoon - the sky is darker than at midday, and the Sun can be low enough to be obscured by houses or trees while Mercury is still fairly high. Once the scope is safely in shadow, I can use the eyepiece to help centre Mercury before inserting the camera.

 

I don't use a DSLR for planetary, so can't help with what settings to use.



#18 Tulloch

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Posted 10 May 2021 - 08:20 PM

OK, dusk-ish then :)

 

My best image of Mercury was taken at about 6:30pm where the sun had almost set and Mercury was sitting at about 22* elevation. Not great, but safe and a record of the planet.



#19 sigo24

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Posted 10 May 2021 - 08:26 PM

Thanks. Ya I do have some trees that could block the Sun about that time. My expectations are low. Given my focal length, I'm good with "yup, looks like a small star". lol




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