21 replies to this topic

[Nicole Sharp]

Are there any advantages or disadvantages of using a hydrogen-alpha Solar telescope such as a Meade Coronado Personal Solar Telescope for prime-focus videography of the upcoming 2019 Mercury transit?

[slavicek]

After doing last year's the eclipse in white light and Ha, I will do just WL.

[hfjacinto]

I don't know HA looks pretty cool (this was the last Mercury transit)

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[Unknownastron]

I have seen 3 Mercury transits and the most recent in May, 2016.  I observed then with both white light and H-alpha.  Using H-alpha I did not see the black drop effect but did see it in white light.  I noticed the same thing in 2012 with the one and only Venus transit I will ever see.  If you have both you might as well look through both but overall white light is adequate.

Clear skies and clean glass,

Mike

[Nojus]

I have seen 3 Mercury transits and the most recent in May, 2016.  I observed then with both white light and H-alpha.  Using H-alpha I did not see the black drop effect but did see it in white light.  I noticed the same thing in 2012 with the one and only Venus transit I will ever see.  If you have both you might as well look through both but overall white light is adequate.

Clear skies and clean glass,

Mike

thanks for advise, planning to watch this year with H-alpha ( bought specially for this occasion), but will prepare with WL also,hope it will be good conditions for it..

 https://www.timeandd...019-november-11

 https://www.facebook...07332869503846/

Edited by Nojus, 10 March 2019 - 07:55 AM.

[Special Ed]

I've never seen a Mercury transit.  I missed the 2003, 2006, and 2016 transits due to clouds--I'm hoping to break that streak with the upcoming transit.  I'll be set up to watch in WL and Halpha.

 

I watched the transit of Venus in 2012 in both Halpha and WL--pretty cool.

Edited by Special Ed, 10 March 2019 - 01:04 PM.

[kfiscus]

I'll be observing the November 2019 Mercury transit in both white light and H-alpha.  I did the same with the Venus transit.  The PST will be piggybacked on the 8" Meade SCT with a glass filter.  Both scopes will have Meade electronic EPs to send their images to monitors for convenient group viewing.  As you can see in the nice H-alpha photo shared above, Mercury's dot is pretty small.

Edited by kfiscus, 10 March 2019 - 01:13 PM.

[emh52]

It looks great in h-alpha and I am sure I'll use my Lunt 80 to image, but there are other wavelengths, this pic is the last transit with 830 nm cut-off IR using a Questar. The color is just a choice I made that is easy on my eye as the primary image is gray. Full resolution is at:  https://flic.kr/p/G9fwfM

 

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[Rich (RLTYS)]

I also observed the Mercury Transit (2016) with white light (Genesis Refractor) and my Double Stacked 40mm PST. The views in both scopes were great.

 

Rich (RLTYS)

[phillip]

Note never look at the sun without proper solar filters, plug the finder even remove for public

Safety!


Venus was the real winner but now century plus away. Mercury is quite small.

Likely do both with PST and this time use the XT8, visual image size perhaps use the larger scope.

Both views interesting. Hope for clear sky!

[t_image]

Are there any advantages or disadvantages of using a hydrogen-alpha Solar telescope such as a Meade Coronado Personal Solar Telescope for prime-focus videography of the upcoming 2019 Mercury transit?

I was wondering why you haven't gotten better answers as far as imaging,

and then I noticed you posted this on Solar System Observing and not

on Solar System Imaging and Processing or better yet Solar Observing and Imaging subsection forum.

 

1.

What at least 5 comments (observational) do not apply to,

is the spatial resolution of your imaging system.

Since you didn't mention a camera, it's worthless to guess even though you mention 1 part of the puzzle.

 

spatial resolution is how much sky is represented by one pixel of you camera sensor.

Extreme: Mercury fits on one pixel v. Mercury fits on 50 pixels. Fifty would be better than one......on the same sensor....

Use an online calculation to determine the spatial resolution,

such as this one:

http://astronomy.too.../field_of_view/

(use imaging tab, make sure the aperture and focal length of the scopes are correct),

enter in the resolution and pixel pitch of camera sensor.

 

Compare the two different set-ups (assuming your alternative is using a white-light filter on a scope or tele-lens) and see if there is much difference in spatial resolution.

Because if the PST is so low in spatial resolution (larger amount of sky [angular degrees in seconds] represented by each camera pixel),

then the detail that you will capture might not be worth that much in the PST comparatively to W-L and the same camera.

 

If you would be using the same camera, then a cheat would be to compare the FL of each set-up (larger focal length=better spatial resolution),

but it won't give you resolution numbers to compare......

 

2.

Video resolution.

So I'm assuming you have an appropriate astro video cam suited for Solar System imaging like a ZWO or ASI or a ptgrey that can do high framerate at a decent resolution?

Because it seems little sense to use an expensive DSLR in 1080HD or lower res. when there are 4K cameras available, also lots of fast exposure stills can work.....

Since the event is slow, with a higher MP still camera one should just take a series of continuous short exposure still images. (you have to work out the limits of the particular model).

Also consider solar imaging deals with direct sunlight on the system and camera heat issues.....

There are a few tips (beyond the scope of this thread) that can help....

 

Why video resolution important?

because similar to the importance of spatial resolution of the optics to sensor pixel pitch match (of how much sky is represented by one pixel),

the capture resolution of a camera in video mode

(however the sampling is being done -line skipping,interpolation,region-of-interest),

also determines how much of the captured (amount of sky per-pixel) is represented by a video pixel.....

All the efforts to get Mercury represented spatially by 10 pixels would be a waste if in the video, it is only represented by one pixel......

 

Now if your system doesn't have the Solar disk taking up much of the sensor, then a region-of-interest feature of a camera (lower resolution but 1:1 pixel representation) may nullify this worry [depending on how the camera/software does it]....

 

Note taking high MP still images (like with DSLR) short-cuts this issue as the camera sensor is giving a more 1:1 pixel read-out than with video.....

 

3. Color camera.

Now if you are using a OSC or DSLR, you probably have heard of the issue with the CFA and narrowband like H-a (only red) that reduces the capture resolution (as only red covered pixels contain accurate h-a info, rest mostly noise)......

nay-sayers say it's 1/4 but real-world test disagrees to such a figure. Do expect it cuts the captured resolution, at least in half.

Another thing to consider if thinking to do crappy video res. captures....

However a high MP DSLR with still images of h-a may more than rival any 4K pt grey industrial mono video camera, real-world testing needed.....

 

Other considerations:

 

a. Bonus of h-a is Solar activity captured!!!!

I captured the recent U.S. TSE with my LUNT 100LS SS with a FF 4K camera in 4K video, and that day there was lots of fun solar activity!!!

All that would have been missed with my white-light setup.....(had a parallel, didn't use it much---busy enjoying the event to run two systems perfectly)......

For outreach I also connected my 4K recorder to a 4K display (32 inch) under our tent, (to provide shade and heat relief)

and many onlookers and passer-bys (at a TSE event) enjoyed seeing the eclipse along with the obvious Proms in the h-a liveview of the Sun......

 

b. if my camera is attached, will I miss great views of h-a visually?

 

Since the TSE was slow, I sacrificed a bit (easy to recover missing frames in post),

and did pull the camera extension tube out a number of times to give 'er a look with the old eyepiece, and it was worth it as imaging resolution and display dynamic range doesn't match what is seen visually in a solar scope.....

My setup allows easy focus recovery, sometime to consider when changing from imaging-to-visual and back.....

 

c. when all is said and done, the one thing to worry about the most is:no cloud cover wanted!!!!!

 

d. if no video, what about losing any fun transit options?

Capturing 4K video for me was the easiest (and camera of 12MP, wasn't too much better in stills anyways),

but I didn't catch and fun transiting planes or birds across the Solar disk while the TSE occurred.--a big hope of mine.....

I might have ultimately had an easier time just capturing continuous sequences of stills to process "lucky imaging' and compile frames for a timelapse......

 

Although, have to say, experiencing the event was more fun than any resultant captures I have.....

[Tonk]

Last transit in Ha just to give you ideas about options. This image captures the brief (~15 mins) flaring going on with the sun spot

Imaging details here ->

Edited by Tonk, 18 March 2019 - 02:38 PM.

[satellitespotter]

Can't wait for this transit, although it won't beat the Venus transit of 2012!

[AxelB]

November is usually very cloudy around here. I cross my finger but my hope is low.

I’ll be ready with my C8 and Baader astrosolar filter.

Edited by AxelB, 22 March 2019 - 11:25 PM.

[gnowellsct]

November is usually very cloudy around here. I cross my finger but my hope is low.

I’ll be ready with my C8 and Baader astrosolar filter.

I am sure it will rain.  I feel lucky to have observed two previous Mercury transits and both Venus transits.  

 

One thing to consider folks: we were clouded out for the last Venus transit but just as the sun was setting the clouds broke. But where we were we could see nothing because the view was blocked by a tree!  

 

Where I was set up in the field, I had a G11/HD tripod/FS128 with white light filter.  There were four of us.  We picked up that EQ mount with scope and counterweight and briskly walked it 150 feet or so to the end of the field here we could see, leaving behind the power supply and a bunch of wires.  And so, we caught the final minutes of the transit.  

 

I recount this story because the next Mercury transit after November is 2032, and some of us might not have enough decades left.  So my advice to you is: select your gear not just on the basis of the best filter, or the best aperture, but consider also if you might have *mobillity needs* to relocate during the event.  If the transit is high I suppose it won't matter.  But it's a thing to take into consideration while planning.  

 

For the our local conditions the day of the Venus transit, an undriven alt-az would have been better.  But we managed to pull it off.  GN

[JoseBorrero]

bump

[Rich (RLTYS)]

I am sure it will rain.  I feel lucky to have observed two previous Mercury transits and both Venus transits.  

 

One thing to consider folks: we were clouded out for the last Venus transit but just as the sun was setting the clouds broke. But where we were we could see nothing because the view was blocked by a tree!  

 

Where I was set up in the field, I had a G11/HD tripod/FS128 with white light filter.  There were four of us.  We picked up that EQ mount with scope and counterweight and briskly walked it 150 feet or so to the end of the field here we could see, leaving behind the power supply and a bunch of wires.  And so, we caught the final minutes of the transit.  

 

I recount this story because the next Mercury transit after November is 2032, and some of us might not have enough decades left.  So my advice to you is: select your gear not just on the basis of the best filter, or the best aperture, but consider also if you might have *mobillity needs* to relocate during the event.  If the transit is high I suppose it won't matter.  But it's a thing to take into consideration while planning.  

 

For the our local conditions the day of the Venus transit, an undriven alt-az would have been better.  But we managed to pull it off.  GN

I had a the same situation on the last transit of Venus and it wasn't until 15 minutes before the Sun set that there was a hole in the clouds. Observed about 5 minutes of the transit. Well at least I saw it.

[PXR-5]

What magnification do some of you guys suggest?
For the Transit of Venus, I used my Mak, but, my ST80 is calling me, it's just easier to spot the Sun.
But not sure if 40x is gonna give me an enjoyable view.

[Mikefp]

What magnification do some of you guys suggest?
For the Transit of Venus, I used my Mak, but, my ST80 is calling me, it's just easier to spot the Sun.
But not sure if 40x is gonna give me an enjoyable view.

I keep hearing 50x plus

[PXR-5]

I keep hearing 50x plus

I'm gonna throw the 8mm-24mm zoom on the ST80, that will give me 50, but keep the Mak on stand by I think.

[Nicole Sharp]

I was wondering why you haven't gotten better answers as far as imaging,

and then I noticed you posted this on Solar System Observing and not

on Solar System Imaging and Processing or better yet Solar Observing and Imaging subsection forum.

 

1.

What at least 5 comments (observational) do not apply to,

is the spatial resolution of your imaging system.

Since you didn't mention a camera, it's worthless to guess even though you mention 1 part of the puzzle.

 

spatial resolution is how much sky is represented by one pixel of you camera sensor.

Extreme: Mercury fits on one pixel v. Mercury fits on 50 pixels. Fifty would be better than one......on the same sensor....

Use an online calculation to determine the spatial resolution,

such as this one:

http://astronomy.too.../field_of_view/

(use imaging tab, make sure the aperture and focal length of the scopes are correct),

enter in the resolution and pixel pitch of camera sensor.

 

Compare the two different set-ups (assuming your alternative is using a white-light filter on a scope or tele-lens) and see if there is much difference in spatial resolution.

Because if the PST is so low in spatial resolution (larger amount of sky [angular degrees in seconds] represented by each camera pixel),

then the detail that you will capture might not be worth that much in the PST comparatively to W-L and the same camera.

 

If you would be using the same camera, then a cheat would be to compare the FL of each set-up (larger focal length=better spatial resolution),

but it won't give you resolution numbers to compare......

 

2.

Video resolution.

So I'm assuming you have an appropriate astro video cam suited for Solar System imaging like a ZWO or ASI or a ptgrey that can do high framerate at a decent resolution?

Because it seems little sense to use an expensive DSLR in 1080HD or lower res. when there are 4K cameras available, also lots of fast exposure stills can work.....

Since the event is slow, with a higher MP still camera one should just take a series of continuous short exposure still images. (you have to work out the limits of the particular model).

Also consider solar imaging deals with direct sunlight on the system and camera heat issues.....

There are a few tips (beyond the scope of this thread) that can help....

 

Why video resolution important?

because similar to the importance of spatial resolution of the optics to sensor pixel pitch match (of how much sky is represented by one pixel),

the capture resolution of a camera in video mode

(however the sampling is being done -line skipping,interpolation,region-of-interest),

also determines how much of the captured (amount of sky per-pixel) is represented by a video pixel.....

All the efforts to get Mercury represented spatially by 10 pixels would be a waste if in the video, it is only represented by one pixel......

 

Now if your system doesn't have the Solar disk taking up much of the sensor, then a region-of-interest feature of a camera (lower resolution but 1:1 pixel representation) may nullify this worry [depending on how the camera/software does it]....

 

Note taking high MP still images (like with DSLR) short-cuts this issue as the camera sensor is giving a more 1:1 pixel read-out than with video.....

 

3. Color camera.

Now if you are using a OSC or DSLR, you probably have heard of the issue with the CFA and narrowband like H-a (only red) that reduces the capture resolution (as only red covered pixels contain accurate h-a info, rest mostly noise)......

nay-sayers say it's 1/4 but real-world test disagrees to such a figure. Do expect it cuts the captured resolution, at least in half.

Another thing to consider if thinking to do crappy video res. captures....

However a high MP DSLR with still images of h-a may more than rival any 4K pt grey industrial mono video camera, real-world testing needed.....

 

Other considerations:

 

a. Bonus of h-a is Solar activity captured!!!!

I captured the recent U.S. TSE with my LUNT 100LS SS with a FF 4K camera in 4K video, and that day there was lots of fun solar activity!!!

All that would have been missed with my white-light setup.....(had a parallel, didn't use it much---busy enjoying the event to run two systems perfectly)......

For outreach I also connected my 4K recorder to a 4K display (32 inch) under our tent, (to provide shade and heat relief)

and many onlookers and passer-bys (at a TSE event) enjoyed seeing the eclipse along with the obvious Proms in the h-a liveview of the Sun......

 

b. if my camera is attached, will I miss great views of h-a visually?

 

Since the TSE was slow, I sacrificed a bit (easy to recover missing frames in post),

and did pull the camera extension tube out a number of times to give 'er a look with the old eyepiece, and it was worth it as imaging resolution and display dynamic range doesn't match what is seen visually in a solar scope.....

My setup allows easy focus recovery, sometime to consider when changing from imaging-to-visual and back.....

 

c. when all is said and done, the one thing to worry about the most is:no cloud cover wanted!!!!!

 

d. if no video, what about losing any fun transit options?

Capturing 4K video for me was the easiest (and camera of 12MP, wasn't too much better in stills anyways),

but I didn't catch and fun transiting planes or birds across the Solar disk while the TSE occurred.--a big hope of mine.....

I might have ultimately had an easier time just capturing continuous sequences of stills to process "lucky imaging' and compile frames for a timelapse......

 

Although, have to say, experiencing the event was more fun than any resultant captures I have.....

 

Based on the feedback in other posts from Cloudy Nights, I decided to do continuous shooting instead of video.  I ended up using two white-light Solar telescopes (both at 1000 mm of focal length), one for continuous shooting at prime focus, and the other for visual use and afocal imaging.  Really glad I had two Solar telescopes though.  You can barely see Mercury at all on the camera viewscreen, so it's really good to have a second Solar telescope for visual use so you don't have to wait until you get home to see Mercury in the captured images.

 

Regarding hydrogen alpha versus white light for visual use, I am glad I used white light since Mercury is so small and difficult to find on a manual altazimuth mount under partly cloudy skies.  A hydrogen-alpha Solar telescope I think would have been more difficult to see Mercury with, particularly under poor seeing conditions.  I do wish I had been able to get a long-eyerelief wide-field eyepiece though, but was stuck using a zoom eyepiece instead.

 

The small aperture of something like a Meade Coronado PST (400/40) I don't think is an issue for imaging Mercury, but the trick would be getting the focal length long enough to provide enough useful magnification, and making sure there is enough backfocus for a DSLR camera (ignoring the additional issue of monochromatic radiation in a color camera sensor), though something like a 2X or 3X Barlow lens should work in theory.

[Dave Mitsky]

A hydrogen-alpha Solar telescope I think would have been more difficult to see Mercury with, particularly under poor seeing conditions.

I was able to see Mercury through my PST at magnifications of 25 and 33x when the skies were less cloudy but the views were far better through the larger aperture scopes with white light filters.  I was unable to see the small prominences that were present during the transit.