tailoring Canon Rebel T6s for 2017

[wtxnitz]

As I have been working with Maestro and my setup, I came up with several questions. They concern both the program
and your observing experience.

My setup is
Canon EOS Rebel T6s
Canon EF 70-300mm zoom f/4-5.6 (will use 300mm, f 5.6 or higher)
Seymour Optics glass solar filter 67mm
iOptron Cube Pro with eq wedge - running equatorial
MacBook Pro 2016
Solar Maestro through USB.
Telegizmo solar observing blanket - essential!

So far i have been running extensive tests and planning. I am a retired engineer who did many field tests with extensive planning.

I have narrowed down the exposure baseline to 1/640 to 1/800 f 5.6, ISO 200. I need to mention, I live in West Texas, altitude 1 mile 5280 -1610m. typical humidity teens to single diigt.
My prime site is near Anderson SC, about 1.5km 0.93 miles from the centerline.

I have been playing with Maestro extensively

Here are some questions so far
the Meastro script wizard generates 1/1250, f/8, ISO 200 for the sun disk; my current calibration is 1/320, 8, 200 - a full 2 stops difference. comments?
I'm basing the exposure on raw digital max values of 75% of 16 bit raw to avoid clipping.
what does this mean for exposures during totality?
I'm now at 5280 ft (1610m), 10% humidity, any guess for settings for SC, 257m, Aug exposure?
I will calibrate on new/ crescent moon - is that valid for total? with alt/ rh correction?
I can trade ISO for aperture (and other) ISO 3200 noise looks ok. Any advantage to higher f#? I can see close range difference, but any help at infinity? DOF?
Is eyepatch worth it?
At 300mm, the sun's diameter is 720 pixels in 6000x4000 frame. I think I should be good for the corona (8.3 solar diam for full width)
prime site is 1.5km from centerline. Your app shows corona broadest ~ 90 deg to crescent. Pre total, can I align using the partial crescent for rotating camera to get max corona? Canon rebel with 300mm lens
I am using pixinsight for some processing. Do you know any scripts for eclipse post-processing?
Thanks in advance

[xjubier]

Telegizmo solar observing blanket - essential!

It can indeed help when you leave the equipment for hours.

The script wizard is just there to help beginners and give them an idea of what they have to do. Yet I recommend polishing your own script.
The exposure settings difference can likely be explained by:
- the solar filter used (usually two major types: ND4 or ND5); yours is likely ND5
- the height of the Sun
- the location (local elevation, latitude, season)
With your setup your partial stages exposure time is likely one stop too much, 1/640s will likely give better results (it is better to underexpose slightly anyway). Check also that exposure compensation is set to 0 and of course that the exposure mode is Manual 'M'.
Again what you have to do is test your setup and find the best exposure settings for the two partial stages. Refer to
http://xjubier.free.fr/en/site_pages/solar_eclipses/Solar_Eclipse_Maestro_Help/pgs/c1sem22.html
And on eclipse day you can do a couple test exposures before the eclipse begins and adjust the exposure time for the partial stages in the script.

I'm now at 5280 ft (1610m), 10% humidity, any guess for settings for SC, 257m, Aug exposure?

Most likely much higher humidity so the exposure time may have to be slightly adjusted for the partial stages.

I'd recommend you always operate your lens at f/8 as it is likely the aperture for which you'll get the best results. Also using ISO 100 is better as the noise level is lower and with your setup you can do it, you can however increase the ISO to 400 or even 800 to shoot Earthshine for example (it will shorten the exposure time needed so that you get more time for the solar corona and this is what you want).
Also do make sure your disable any noise reduction (high ISO and all the others) as one you don't want the camera to do any processing of your pictures and two let the camera spend too much time processing your pictures. All this can be done afterwards.

During totality, the 2+ minutes when you'll see the solar corona you have to take ramps of exposures at stay 1 stop step increment: the reason is that the dynamic of the corona easily covers 12 to 14 stops, so to be able to reveal all the finest details you need to have all those exposures that you can then stack and process. In one single exposure there is no way you can capture everything. So for example you do ramps at ISO 100, f/8, and 1/1000s to 2s without the solar filter of course.
The eyepatch can help improve your dark adaptation, so if you want to see more details of the corona naked eye it is worth having one.

The alignment of the camera should be along the solar equator, see
http://xjubier.free.fr/en/site_pages/solar_eclipses/Solar_Eclipse_Maestro_Help/pgs/c1sem38.html

So a sample script could be (the only adjustment in your case would likely be the exposure time during the partial stages so very easy to change)
# Pre C1
TAKEPIC,C1,-,00:40.0,T6s,1/4000,8.0,100,0.0,RAW,None,N, Pre-C1 uneclipsed bracket
TAKEPIC,C1,-,00:30.0,T6s,1/2000,8.0,100,0.0,RAW,None,Y, Pre-C1 uneclipsed bracket
TAKEPIC,C1,-,00:20.0,T6s,1/1000,8.0,100,0.0,RAW,None,Y, Pre-C1 uneclipsed
TAKEPIC,C1,-,00:10.0,T6s,1/1000,8.0,100,0.0,RAW,None,Y, Pre-C1 uneclipsed

# Partial stages before C2 and after C3
FOR,(VAR),0,1,99
TAKEPIC,MAGPRE (VAR) ,+,00:00.0,T6s,1/4000,8.0,100,0.0,RAW,None,Y, Partial
TAKEPIC,MAGPRE (VAR) ,+,00:10.0,T6s,1/2000,8.0,100,0.0,RAW,None,Y, Partial
TAKEPIC,MAGPRE (VAR) ,+,00:20.0,T6s,1/1000,8.0,100,0.0,RAW,None,Y, Partial
TAKEPIC,MAGPOST (VAR),+,00:00.0,T6s,1/4000,8.0,100,0.0,RAW,None,Y, Partial
TAKEPIC,MAGPOST (VAR),+,00:10.0,T6s,1/2000,8.0,100,0.0,RAW,None,Y, Partial
TAKEPIC,MAGPOST (VAR),+,00:20.0,T6s,1/1000,8.0,100,0.0,RAW,None,Y, Partial
ENDFOR

# Post C4
TAKEPIC,C4,+,00:10.0,T6s,1/1000,8.0,100,0.0,RAW,None,N, Post-C4 uneclipsed
TAKEPIC,C4,+,00:20.0,T6s,1/1000,8.0,100,0.0,RAW,None,Y, Post-C4 uneclipsed
TAKEPIC,C4,+,00:30.0,T6s,1/2000,8.0,100,0.0,RAW,None,Y, Post-C4 uneclipsed bracket
TAKEPIC,C4,+,00:40.0,T6s,1/4000,8.0,100,0.0,RAW,None,Y, Post-C4 uneclipsed bracket

PLAY,C2,-,00:25.0,Filters_Off.wav, , , , , , , , FILTERS OFF!!!!
PLAY,C3,+,00:20.0,Filters_On.wav, , , , , , , , FILTERS ON!!!!

# C2 Baily's beads, chromosphere and prominences
CHGCSSL,C2,-,00:10.0,T6s, , ,3, , , , , Set to 3 fps
TAKEBST,C2,-,00:05.0,T6s,1/1000,8.0,100,24,RAW,None,N, Burst of 40 pictures (8s)

# C3 Baily's beads, chromosphere and prominences
CHGCSSL,C3,-,00:10.0,T6s, , ,3, , , , , Set to 3 fps
TAKEBST,C3,-,00:05.0,T6s,1/1000,8.0,100,30,RAW,None,N, Burst of 50 pictures (10s)

# Totality
LVPSTART,C2,-,00:15.0,T6s, , , , , , , , Start photography in Lv
RAMPSUD,C2,+,00:06.0,T6s,1/1000,8.0,100,0.0,RAW,None,Y,13,1.0, Ramping up and down
TAKEPIC,MAX,-,00:01.0,T6s,2.0,8.0,800,0.0,RAW,None,Y, Earthshine
RAMPSUD,MAX,+,00:06.0,T6s,1/1000,8.0,100,0.0,RAW,None,Y,13,1.0, Ramping up and down
LVPSTOP,C3,+,00:15.0,T6s, , , , , , , , Stop photography in Lv

[wtxnitz]

Thank you for the guidance
I took some dark frames and measured noise standard deviations
here is a subset
all at f/22
exp 1/t ISO cnts rel. noise
25 22 100 33.2 1.00
50 22 200 35.5 1.07
100 22 400 40.5 1.22
200 22 800 57.9 1.74
400 22 1600 94.2 2.84
800 22 3200 150.3 4.53
so you can see up to ISO 400 is not bad and 800 is moderate
I think I'll run 100 or 200 for most, and 800 for moonshine.

[xjubier]

I think I'll run 100 or 200 for most, and 800 for moonshine.

Sounds good, but it's Earthshine, not Moonshine.

Taking darks, flats and bias will of course help if you do jut before/after the eclipse.

PS: I'll send you a link to the beta in a couple days.

[wtxnitz]

Sounds good, but it's Earthshine, not Moonshine.

Duh. How stupid of me. My mind was elsewhere.
I often use that at star parties when all five naked eye planets are visible at once. "Can you see the light of seven solar system bodies?" 5 planets, the Moon and Earthshine.
Thanks

[wtxnitz]

# Partial stages before C2 and after C3
FOR,(VAR),0,1,99
TAKEPIC,MAGPRE (VAR) ,+,00:00.0,T6s,1/4000,8.0,100,0.0,RAW,None,Y, Partial
TAKEPIC,MAGPRE (VAR) ,+,00:10.0,T6s,1/2000,8.0,100,0.0,RAW,None,Y, Partial
TAKEPIC,MAGPRE (VAR) ,+,00:20.0,T6s,1/1000,8.0,100,0.0,RAW,None,Y, Partial
TAKEPIC,MAGPOST (VAR),+,00:00.0,T6s,1/4000,8.0,100,0.0,RAW,None,Y, Partial
TAKEPIC,MAGPOST (VAR),+,00:10.0,T6s,1/2000,8.0,100,0.0,RAW,None,Y, Partial
TAKEPIC,MAGPOST (VAR),+,00:20.0,T6s,1/1000,8.0,100,0.0,RAW,None,Y, Partial
ENDFOR

There seems to be a problem translating this command.
When it loads, the time interval is less than 0.1 secs
I changed the code to
TAKEPIC,MAGPRE (VAR) ,+,10:00.0,T6s,1/4000,8.0,100,0.0,RAW,None,Y, Partial
TAKEPIC,MAGPRE (VAR) ,+,20:00.0,T6s,1/2000,8.0,100,0.0,RAW,None,Y, Partial
TAKEPIC,MAGPRE (VAR) ,+,30:00.0,T6s,1/1000,8.0,100,0.0,RAW,None,Y, Partial
and so on. This should be 10 minute intervals. The generated interval starts at around 6.8 secs goes down to 3.8
I tried it with and without the space after (VAR)

[xjubier]

No my syntax was 100% correct, the issue there is just a bug that I introduced in parsing the MAGPRE and MAGPOST actions. Thanks for pointing this out.

The bug will be fixed in the coming release. If you want I could already provide a beta version fixing the bug.

[wtxnitz]

Please send the beta. I'll be glad to wring it out for you.