Solar Observing question

[Tim Vent]

With the upcoming transit of Mercury, and after attending Ric's Solar filter review, my friend and I are looking forward to setting up at the local community college to do some photography and outreach.

My question is, even with a good solar filter, will pointing my scope at the Sun for the 8 hours or so it will take Mercury to transit make it soak up enough heat to damage it in any way? I'm just a little worried.

Any input from the Solar folks here?

Thanks,
Tim

[Ric Honey]

It is not likely that any damage will occur if you follow the guidelines I outlined in the presentation last Friday.
BUT, if you will provide more details about the equipment, I will be in a better position to make an assessment.
What telescope? Aperture size? What solar filter? Full aperture or off-axis? What eyepieces, brand/type? Also, what kind of imaging system?

Remember that you will be able to see absolutely NOTHING through the telescope with the solar filter in place, so finding the sun through the eyepiece is nearly impossible.  The best approach is use the shadow of the telescope on the ground to center the sun in the field of view.  To do this you make the shadow of the optical tube assembly (OTA) as small as possible.

Good luck
Ric Honey

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[Tim Vent]

Thanks for chiming in Ric.

The telescope is a 4" refractor. Televue NP101.
My plan is to use a full-aperture filter made from the Baader ND5 visual grade film (I can't seem to find the ND3.8 anywhere in the US.)
We haven't decided on which camera to use, but it will either be a ZWO ASI120MC-S planetary CMOS camera or a Nikon DSLR (we have a crop-sensor 7100 or a full-frame 610 available.)
We'll likely only use an eyepiece for a short duration of time, just to take a peek once we have the Sun in the scope using your shadow method described below. Given the short focal length of this scope, I'm guessing we'll be using a 13mm Nagler or smaller.

Our ultimate goal is to take shots at an interval that will allow us to combine the frames into one of those photos that show Mercury dotting across the Sun. We haven't calculated what that interval will be yet.

Thanks,
Tim

[Ric Honey]

Good.
There is a good reason it's difficult to find ND3.8 film, it's dangerously not enough for visual use and there is no reason to use MORE light with modern ccd cameras.

All of this should be fine, you are using top quality equipment and it is all well made so you should have no problems.
I would love to see the results....

Ric

[William M. Wilson]

Tim,

I agree with Ric—the likelihood of damage is vanishingly remote, including to the eyepiece if the light reaching it comes through the filter first. I have observed the sun since 1979 using a Questar 3.5 inch scope and full-aperture glass filter, and have had the scope track the sun for at least 8 hours on a few occasions with absolutely no damage.  

Bill Wilson

[Tim Vent]

Thanks Ric, I was hoping that would be the case with the visual film and the CCD.
I'm leaning towards using it over the DSLR's, but I am still learning the software for it.

I'll be sure and post the result (or a link to it - whatever Google allows) here, assuming the results turn out OK.
I've been dipping my toe in the long-exposure water, but this will be our first attempt at something like this.
I'm looking forward to seeing how it turns out.

Thanks,
Tim

[Tim Vent]

Thanks for chiming in Bill.
That makes me feel a lot better.

Thanks,
Tim

[Ric Honey]

This will not require long exposures.
In fact, if it weren't for keeping the sun framed the same, there is no need for a clock drive.
Ric

[Chris Maloney]

Tim and I have another goal (at least I do!) of timing contacts I,II, III and IV as accurately as possible.  The first two might prove difficult since they occur minutes after sunrise here, but I'm hopeful.  The problem is that we don't have a solar H-alpha filter.  From my reading, it is rather difficult to get accurate times without one, since one can't see mercury against the chromosphere/prominences just before contact I and after contact IV.  any thoughts?

---

From: memphi...@googlegroups.com <memphi...@googlegroups.com> on behalf of Tim Vent <tim...@gmail.com>
Sent: Wednesday, April 6, 2016 11:18 AM
To: Memphis Astronomical Society
Cc: tim...@gmail.com; r...@memphisastro.org
Subject: Re: [MemphisAstro:908] Solar Observing question

 

[William M. Wilson]

If you start a video recording just before the predicted time of first contact (and get lucky with atmospheric conditions) you will have a good chance of picking up first contact on one of the frames. I don’t know that you’d do better with an H-alpha filter unless there were prominences in just the right spot, and with solar activity at its current extremely low level, that’s unlikely.

[Brandon Jordan]

I have a Baader Herschel Wedge and am really looking forward to the transit. Is the MAS planning on an official viewing event?

Regards,

Brandon Jordan

Fayette County

[Freddy Diaz]

K3ccdtools an old software for astronomy video capture, has a way of saving a file with the time of each frame was taken, then you can superimpose the original video and the times for a very neat way of recording event times.

Freddy

[Chris Maloney]

Thanks, Bill!  Tim, is the planetary camera a video camera?

---

From: William M. Wilson <wwil...@att.net>
Sent: Wednesday, April 6, 2016 11:42 AM
To: Chris Maloney
Cc: Tim Vent; Memphis Astronomical Society; Ric Honey
Subject: Re: [MemphisAstro:910] Solar Observing question

 

[Chris Maloney]

I'll check it out.  Thanks.

---

From: Freddy Diaz <freddy...@gmail.com>
Sent: Wednesday, April 6, 2016 1:56 PM
To: Brandon J
Cc: Memphis Astronomical Society; William M. Wilson; Chris Maloney; Ric Honey; Tim Vent
Subject: Re: [MemphisAstro:912] Solar Observing question

 

[Tim Vent]

Yes it is, but I just modeled it in Stellarium and it looks like the field will be too small to fit the Sun in it - even through the wide f5.4 field of my scope. I tried it with the .8x focal reducer and even then the field is just slightly too small.

So for the big picture, looks like we'll be using the DSLR; although we can still do some close-up video footage for the timings.

On Wednesday, April 6, 2016 at 3:12:15 PM UTC-5, Chris Maloney wrote:

Thanks, Bill!  Tim, is the planetary camera a video camera?

---

From: William M. Wilson <wwil...@att.net>
Sent: Wednesday, April 6, 2016 11:42 AM
To: Chris Maloney
Cc: Tim Vent; Memphis Astronomical Society; Ric Honey
Subject: Re: [MemphisAstro:910] Solar Observing question

 

If you start a video recording just before the predicted time of first contact (and get lucky with atmospheric conditions) you will have a good chance of picking up first contact on one of the frames. I don’t know that you’d do better with an H-alpha filter unless there were prominences in just the right spot, and with solar activity at its current extremely low level, that’s unlikely.

On Apr 6, 2016, at 11:32 AM, Chris Maloney <cmal...@pccua.edu> wrote:

Tim and I have another goal (at least I do!) of timing contacts I,II, III and IV as accurately as possible.  The first two might prove difficult since they occur minutes after sunrise here, but I'm hopeful.  The problem is that we don't have a solar H-alpha filter.  From my reading, it is rather difficult to get accurate times without one, since one can't see mercury against the chromosphere/prominences just before contact I and after contact IV.  any thoughts?

---

From: memphi...@googlegroups.com <memphisastro@googlegroups.com> on behalf of Tim Vent <tim...@gmail.com>

[Tim Vent]

Thanks for the tip Freddy. Downloading it now.

On Wednesday, April 6, 2016 at 1:56:40 PM UTC-5, FreddyDiaz wrote:

K3ccdtools an old software for astronomy video capture, has a way of saving a file with the time of each frame was taken, then you can superimpose the original video and the times for a very neat way of recording event times.

Freddy

On Apr 6, 2016 12:38 PM, "Brandon Jordan" <bdj...@gmail.com> wrote:

I have a Baader Herschel Wedge and am really looking forward to the transit. Is the MAS planning on an official viewing event?

Regards,

Brandon Jordan

Fayette County

On Apr 6, 2016, at 11:42 AM, William M. Wilson <wwil...@att.net> wrote:

If you start a video recording just before the predicted time of first contact (and get lucky with atmospheric conditions) you will have a good chance of picking up first contact on one of the frames. I don’t know that you’d do better with an H-alpha filter unless there were prominences in just the right spot, and with solar activity at its current extremely low level, that’s unlikely.

On Apr 6, 2016, at 11:32 AM, Chris Maloney <cmal...@pccua.edu> wrote:

Tim and I have another goal (at least I do!) of timing contacts I,II, III and IV as accurately as possible.  The first two might prove difficult since they occur minutes after sunrise here, but I'm hopeful.  The problem is that we don't have a solar H-alpha filter.  From my reading, it is rather difficult to get accurate times without one, since one can't see mercury against the chromosphere/prominences just before contact I and after contact IV.  any thoughts?

---

From: memphi...@googlegroups.com <memphisastro@googlegroups.com> on behalf of Tim Vent <tim...@gmail.com>

[William M. Wilson]

Yes—we’ll have several scopes at the Woodland Discovery Playground at Shelby Farms Park, starting about 9am. Although the transit starts at 6:12 am, the sun will be in the trees then, and hardly anyone will be in the park, which opens at sunrise (6:01am on that day). We can follow it until 4th contact at 1:42pm.