Mercury photography question & Introduction

Ghillie · 09-28-2019, 09:49 AM - **1 Like**

Hello Folks,

I've been a member here for a long time, but it's been so long since I last logged in that my account was deleted. Nevertheless, I still consider myself to be a beginner in photography.

On November 11 I wish to photograph the transit of planet Mercury across the face of the Sun. I have an equatorial mount for my K5, and a 49 mm white llight solar filter for my Pentax SMC DA 50-200 mm lens. By my quick calculation, Mercury subtends about 7 arc seconds. Will my lens provide enough magnification to image Mercury?

Thanks, Tom

Last edited by pepperberry farm; 09-28-2019 at 01:45 PM.

photoptimist · 09-28-2019, 10:28 AM

Welcome to the forums!

And thanks for reminding me of the 2019 Transit of Mercury.

With the K-5's pixel size of about 5 microns and with a 200 mm lens, each pixel subtends about 25 microradians. The 10 arcseconds of Mercury is about 48 microradians which makes it big enough to almost blacken a 2x2 pixel region (assuming the lens is sharp). That's fairly small but if you take a stack of snapshots, you should be able to see the track of the shadow.

A longer focal length would be needed to resolve Mercury as a disk. A 1000 mm lens would make it a 10 pixel diameter disk.

Good luck!

EDIT: because Mercury is directly between the Earth and Sun, the disk is much larger (10 arcsec) than when it appears in the sky off to the side of the sun.

Ghillie · 09-28-2019, 11:53 AM

Good afternoon,

Thank you for the informative response.

Unfortunately, I've never learned how to stack photos. I've tried to learn how to use several different, free software packages, but just haven't been able to get started. Living out in the sticks like I do, I don't know any other photo buffs or amateur astronomers. I have to teach myself.

I hope I'll be able to see Mercury or its shadow in single images.

Thanks again, Tom

**UncleVanya** · 09-28-2019, 02:11 PM

The DA 50-200 hasn't a reputation for being especially sharp. I would suggest not only a longer lens but a sharper one if possible.

Ghillie · 09-28-2019, 04:02 PM

Hi Vanya,

I have an old Samyang 100-500 zoom telephoto lens that I've never used. It works with my K5, and 72 mm filters are available. Might it be a better choice?

Thanks, Tom

**UncleVanya** · 09-29-2019, 09:43 PM

Originally posted by Ghillie

Hi Vanya,

I have an old Samyang 100-500 zoom telephoto lens that I've never used. It works with my K5, and 72 mm filters are available. Might it be a better choice?

Thanks, Tom

Only you can tell. What I would do is find a distant landmark or object that is stationary and you can get a good shot of. Take multiple shots using each be lens. Vary the focal length back from the max since some zooms are sharper a bit short of maximum.

Once you have the shots, crop the shorter focal length to give similar images then zoom into both of them to see which picture gives the better image in your opinion.

Edit: Beware a weak tripod will not work well in this test. Sandbags on a window sill might be best.

**Kerrowdown** · 10-01-2019, 05:12 AM

Welcome back to the forum, sorry I can’t offer any advice to your question.

**beachgardener** · 10-03-2019, 12:35 AM

G'day mate and welcome to the forum

K-5 hey? I like my K-5, been thinking of getting a low mileage K-5 IIs to preserve the ability to record images with this sensor.

**ThorSanchez** · 11-11-2019, 08:39 AM - **1 Like**

Here's another option. Not a great one, mind you... I took my kid's cheap telescope, pointed it at the sun. Definitely didn't look in the eyepiece, but pointed it at the wall and then the ceiling. You can definitely see Mercury going across the sun's disk. Then I took the K-3ii and took a picture of the ceiling, and did some RawTherapee enhancement so you can just make out the smudge that is Mercury.

**Mikesul** · 11-11-2019, 12:11 PM

Be sure to let us know how this turns out.

photoptimist · 11-11-2019, 12:52 PM

Originally posted by ThorSanchez

Here's another option. Not a great one, mind you... I took my kid's cheap telescope, pointed it at the sun. Definitely didn't look in the eyepiece, but pointed it at the wall and then the ceiling. You can definitely see Mercury going across the sun's disk. Then I took the K-3ii and took a picture of the ceiling, and did some RawTherapee enhancement so you can just make out the smudge that is Mercury.

Nice!

I tried this projector approach for the transit of Venus a few years back. It worked but I did have issues with the sun burning the tracks and pits into the plastic inside the eyepiece when the sun moved out of the center of the field.

**ThorSanchez** · 11-11-2019, 01:43 PM

Originally posted by photoptimist

Nice!

I tried this projector approach for the transit of Venus a few years back. It worked but I did have issues with the sun burning the tracks and pits into the plastic inside the eyepiece when the sun moved out of the center of the field.

I put the little plastic cap on the eyepiece when I was walking away from the setup, so none of the kids would be tempted to look in. But in a matter of seconds there was a wisp of smoke and a small hole was starting to be melted in the cap.

**kiwi_jono** · 11-12-2019, 03:20 AM

Welcome and good luck!

**WillWeaverRVA** · 11-12-2019, 08:54 AM

Welcome!

weverka · 11-12-2019, 10:39 AM

Originally posted by ThorSanchez

I put the little plastic cap on the eyepiece when I was walking away from the setup, so none of the kids would be tempted to look in. But in a matter of seconds there was a wisp of smoke and a small hole was starting to be melted in the cap.

I hate it when that happens.

09-28-2019, 09:49 AM - 1 Like	#1
Ghillie New Member Join Date: Sep 2019 Posts: 7	Mercury photography question & Introduction Hello Folks, I've been a member here for a long time, but it's been so long since I last logged in that my account was deleted. Nevertheless, I still consider myself to be a beginner in photography. On November 11 I wish to photograph the transit of planet Mercury across the face of the Sun. I have an equatorial mount for my K5, and a 49 mm white llight solar filter for my Pentax SMC DA 50-200 mm lens. By my quick calculation, Mercury subtends about 7 arc seconds. Will my lens provide enough magnification to image Mercury? Thanks, Tom Last edited by pepperberry farm; 09-28-2019 at 01:45 PM.

09-28-2019, 10:28 AM	#2
photoptimist Pentaxian Join Date: Jul 2016 Photos: Albums Posts: 5,128	Welcome to the forums! And thanks for reminding me of the 2019 Transit of Mercury. With the K-5's pixel size of about 5 microns and with a 200 mm lens, each pixel subtends about 25 microradians. The 10 arcseconds of Mercury is about 48 microradians which makes it big enough to almost blacken a 2x2 pixel region (assuming the lens is sharp). That's fairly small but if you take a stack of snapshots, you should be able to see the track of the shadow. A longer focal length would be needed to resolve Mercury as a disk. A 1000 mm lens would make it a 10 pixel diameter disk. Good luck! EDIT: because Mercury is directly between the Earth and Sun, the disk is much larger (10 arcsec) than when it appears in the sky off to the side of the sun. Last edited by photoptimist; 09-28-2019 at 10:36 AM. Reason: Correction for Mercury's diameter.

09-29-2019, 09:43 PM	#6
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,459	Originally posted by Ghillie Hi Vanya, I have an old Samyang 100-500 zoom telephoto lens that I've never used. It works with my K5, and 72 mm filters are available. Might it be a better choice? Thanks, Tom Only you can tell. What I would do is find a distant landmark or object that is stationary and you can get a good shot of. Take multiple shots using each be lens. Vary the focal length back from the max since some zooms are sharper a bit short of maximum. Once you have the shots, crop the shorter focal length to give similar images then zoom into both of them to see which picture gives the better image in your opinion. Edit: Beware a weak tripod will not work well in this test. Sandbags on a window sill might be best. Last edited by UncleVanya; 10-01-2019 at 05:17 AM.

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09-28-2019, 11:53 AM	#3
Ghillie New Member Join Date: Sep 2019 Posts: 7 Original Poster	Good afternoon, Thank you for the informative response. Unfortunately, I've never learned how to stack photos. I've tried to learn how to use several different, free software packages, but just haven't been able to get started. Living out in the sticks like I do, I don't know any other photo buffs or amateur astronomers. I have to teach myself. I hope I'll be able to see Mercury or its shadow in single images. Thanks again, Tom

09-28-2019, 02:11 PM	#4
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,459	The DA 50-200 hasn't a reputation for being especially sharp. I would suggest not only a longer lens but a sharper one if possible.

09-28-2019, 04:02 PM	#5
Ghillie New Member Join Date: Sep 2019 Posts: 7 Original Poster	Hi Vanya, I have an old Samyang 100-500 zoom telephoto lens that I've never used. It works with my K5, and 72 mm filters are available. Might it be a better choice? Thanks, Tom

10-01-2019, 05:12 AM	#7
Kerrowdown PEG Moderator Join Date: Aug 2008 Location: Highlands of Scotland... "Hold Infinity in the palm of your hand" - William Blake Photos: Gallery Posts: 57,863	Welcome back to the forum, sorry I can’t offer any advice to your question.

10-03-2019, 12:35 AM	#8
beachgardener Site Supporter Join Date: Sep 2013 Location: Australia Photos: Gallery Posts: 3,842	G'day mate and welcome to the forum K-5 hey? I like my K-5, been thinking of getting a low mileage K-5 IIs to preserve the ability to record images with this sensor.

11-11-2019, 12:11 PM	#10
Mikesul Loyal Site Supporter Join Date: Sep 2009 Location: Phoenix, AZ Posts: 7,594	Be sure to let us know how this turns out.

11-11-2019, 12:52 PM	#11
photoptimist Pentaxian Join Date: Jul 2016 Photos: Albums Posts: 5,128	Originally posted by ThorSanchez Here's another option. Not a great one, mind you... I took my kid's cheap telescope, pointed it at the sun. Definitely didn't look in the eyepiece, but pointed it at the wall and then the ceiling. You can definitely see Mercury going across the sun's disk. Then I took the K-3ii and took a picture of the ceiling, and did some RawTherapee enhancement so you can just make out the smudge that is Mercury. Nice! I tried this projector approach for the transit of Venus a few years back. It worked but I did have issues with the sun burning the tracks and pits into the plastic inside the eyepiece when the sun moved out of the center of the field.

11-11-2019, 01:43 PM	#12
ThorSanchez Site Supporter Join Date: Dec 2012 Photos: Gallery \| Albums Posts: 2,807	Originally posted by photoptimist Nice! I tried this projector approach for the transit of Venus a few years back. It worked but I did have issues with the sun burning the tracks and pits into the plastic inside the eyepiece when the sun moved out of the center of the field. I put the little plastic cap on the eyepiece when I was walking away from the setup, so none of the kids would be tempted to look in. But in a matter of seconds there was a wisp of smoke and a small hole was starting to be melted in the cap.

11-12-2019, 03:20 AM	#13
kiwi_jono Loyal Site Supporter Join Date: Dec 2009 Location: Christchurch, New Zealand Photos: Gallery \| Albums Posts: 2,437	Welcome and good luck!

11-12-2019, 08:54 AM	#14
WillWeaverRVA Site Supporter Join Date: Apr 2011 Location: Richmond, VA Photos: Gallery Posts: 1,071	Welcome!

11-12-2019, 10:39 AM	#15
weverka Senior Member Join Date: Sep 2017 Location: Boulder CO Photos: Gallery \| Albums Posts: 133	Originally posted by ThorSanchez I put the little plastic cap on the eyepiece when I was walking away from the setup, so none of the kids would be tempted to look in. But in a matter of seconds there was a wisp of smoke and a small hole was starting to be melted in the cap. I hate it when that happens.