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Sony DSLR and Coronado SolarMax II 60mm focusing issues

beginner dslr solar imaging
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#1 lwoody7110

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Posted 02 September 2020 - 07:14 AM

Hi all

I'm struggling to focus my Sony a55v camera through my Coronado SolarMax II 60mm.  I searched the forum for my camera and no hits came back.  Has anyone had success with this combination or a similar Sony?

The best images I've captured are below.  Is there is 'procedure' to follow?  The last time I tried was 6 years ago and these were the best I got after 3 days effort and a sunburnt forehead.  I became frustrated and put everything away.  Its time to have another go before age and eyesight become a factor.

Any hints and tips greatly appreciated.  Please note that I can't afford to change the camera at the moment.
 

 

 

Most look like this.  Annoyingly it looks sharp in the camera view finder.  Its very frustrating.

DSC00187.JPG

 

 

This is the only image that seems to show detail and that the sun appears to have an atmosphere.  This was pure luck more than any judgement and is the only photo out of hundreds that looks like this.  All the others look like the top photo, and a few like the bottom one.

DSC00198 copy.JPG

 

 

This shows sunspots as dark patches - but it looks nothing like the sun as I see it through the view finder.

DSC00203.JPG

Any tips welcomed.



#2 sg6

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Posted 02 September 2020 - 08:35 AM

What is the order of bits from the scope backwards ?

Basically is the a diagonal in there?

 

If so remove it and fit the DSLR "straight through". That brings the camera in closer to the focal plane and in general that is the problem as the DSLR will sit too far back (ouwards) - mechanical case of DSLR and eyepiece optics are the cause.

 

If no diagonal then little real idea but give detail of all the bits, one may be able to be removed.

 

OR shocked.gif : Buy a new camera, one of the nice new expensive mirrorless should possibly manage lol.gif  lol.gif  lol.gif

 

Wonder if a barlow would help? Image appears small enough that some expansion seems possible, and a balow may push the image out enough. If you have a decent one spare try it.

 

Just in case the edge of the sun will not be a sharp line, it is a ball of gas (well plasma) so no well defined edge.



#3 Tapio

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Posted 02 September 2020 - 08:58 AM

Isn't the diagonal essential in Coronado too as a blocking filter?

I guess best bet is to wait until active region/sunspot emerges and use that for focusing.
Oh and use tethering/computer screen. And a sun shade of some sort.

Edited by Tapio, 02 September 2020 - 08:58 AM.


#4 vincentv

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Posted 02 September 2020 - 10:59 AM

SG6's advice works for nighttime photography.

*Don't* take out the diagonal/blocking filter.

The las 2 photos show the disk in focus. What's left is playing with the exposure settings. Using the histogram is a must. Keep in mind that DSLRs are notoriously bad for narrow bandwidth imaging. That said go out and have fun experimenting.


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#5 MalVeauX

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Posted 02 September 2020 - 11:06 AM

Heya,

 

This is a typical view from these sensors; they are not sensitive to HA and its a color sensor on top of that. Combine this with severe undersampling and you'll see the images you're seeing above. This is why at the eyepiece it looks so different than via this sensor.

 

If you wish to really get into solar imaging, it's suggested to use a smaller pixel based monochrome sensor based camera.

 

Very best,


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#6 lwoody7110

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Posted 02 September 2020 - 11:07 AM

Equipment = Sony a55v (which is translucent) -> Meade Variable Projection Tele-extender (holds eyepiece) -> SolarMax II.  I have a few eye pieces.  I don not recall which was used as these are 6 year old images.

Diagonal is indeed the blocking filter.

As I type this, I'm missing a few pieces of the Tele-extender which attach it to my DSLR body, and the inserts into the SolarMax II eye-piece holder.  I cannot place hands on all parts.  I hope to bump into them soon as I suspect they're in storage.   ***edit. Its possible I purchased a different T adapter to connect the camera to the SolarMax as I'm just not seeing how they'd connect right now. ***

 

This camera cannot be tethered for live output but I will double check this once I find the manual.  It does have HDMI output for video playback.  I don't recall if it offers live output or not.  Either way, HDMI isn't practical beyond focus testing in the context of this thread.  I'm hoping to avoid laptops and further bulky equipment.  The cabling and battery management really gets in the way of trying to enjoy the moment.

I've used the same equipment on my Meade LX200 GPS 8" and achieved focus far more easily for Moon, planets, and using a Baeder (spelling?) solar shield.  Using the shield, I imaged the Sun in white light.  It was that solar success that prompted me to invest in the SolarMax II, which I've not had any imaging success as yet.

I'm hoping that a member here has experience with very similar hardware and can share their experiences.


Edited by lwoody7110, 02 September 2020 - 11:22 AM.


#7 lwoody7110

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Posted 02 September 2020 - 11:19 AM

SG6's advice works for nighttime photography.

*Don't* take out the diagonal/blocking filter.

The las 2 photos show the disk in focus. What's left is playing with the exposure settings. Using the histogram is a must. Keep in mind that DSLRs are notoriously bad for narrow bandwidth imaging. That said go out and have fun experimenting.

Don't worry - the diagonal is staying put.  I haven't used the histogram properly before.  I'll look into understanding it further.  Thanks for the tip.

 

 

 

Heya,

 

This is a typical view from these sensors; they are not sensitive to HA and its a color sensor on top of that. Combine this with severe undersampling and you'll see the images you're seeing above. This is why at the eyepiece it looks so different than via this sensor.

 

If you wish to really get into solar imaging, it's suggested to use a smaller pixel based monochrome sensor based camera.

 

Very best,

ok - so basically the camera cannot see what my eye can see.  It seems the investment in the SolarMax will need further investment with imaging equipment.  The colours seen through the SolorMax are beautiful.  Is there a method to recreate those colours via the monochrome sensor you're suggesting?



#8 MalVeauX

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Posted 02 September 2020 - 11:50 AM

ok - so basically the camera cannot see what my eye can see.  It seems the investment in the SolarMax will need further investment with imaging equipment.  The colours seen through the SolorMax are beautiful.  Is there a method to recreate those colours via the monochrome sensor you're suggesting?

Most dSLR color sensors have IR blocking and the transmission profile grinds down as you approach IR from red, and that's where 656nm falls, so the sensor's sensitivity to 656nm (HA) is lower than it is to say, green (520nm) wavelengths. Add to this that its coming through a bayer matrix and that lowers the signal a bit and lowers resolution as only some of the signal reaches a pixel site. Add to this yet again that the pixels are larger, and the focal-ratio of your system is very fast, and you are severe under-sampling, so detail that normally would be separated by a pixel is instead falling to the same pixel and lost as data as its merged, this is under-sampling. It's ok for the most part, but it contributes when it comes to full discs like this and getting any discernible detail on the surface where contrast is already low.

 

Yes you can replicate any color in post. Our star is a white star, 656nm happens to categorize as a wavelength of red as seen by our cone cells, so it should appear a warm orange/red hue visually, but in reality color isn't absolute. If you had defective cone cells, or if you were quadchromatic, you would see this wavelength differently than someone else. In post you can make it any color you like.

 

Very best,


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#9 lwoody7110

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Posted 02 September 2020 - 12:00 PM

Most dSLR color sensors have IR blocking and the transmission profile grinds down as you approach IR from red, and that's where 656nm falls, so the sensor's sensitivity to 656nm (HA) is lower than it is to say, green (520nm) wavelengths. Add to this that its coming through a bayer matrix and that lowers the signal a bit and lowers resolution as only some of the signal reaches a pixel site. Add to this yet again that the pixels are larger, and the focal-ratio of your system is very fast, and you are severe under-sampling, so detail that normally would be separated by a pixel is instead falling to the same pixel and lost as data as its merged, this is under-sampling. It's ok for the most part, but it contributes when it comes to full discs like this and getting any discernible detail on the surface where contrast is already low.

 

Yes you can replicate any color in post. Our star is a white star, 656nm happens to categorize as a wavelength of red as seen by our cone cells, so it should appear a warm orange/red hue visually, but in reality color isn't absolute. If you had defective cone cells, or if you were quadchromatic, you would see this wavelength differently than someone else. In post you can make it any color you like.

 

Very best,

Thanks for the explanation.  Its a shame to ditch a DSLR as they're convenient and easy to use, as well as multi-purpose for a more bulky laptop / dedicated imaging solution but I understand the limitations of DSLRs and why the colours and detail is lacking.




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