Pi Solar Camera - Astronomy with the Raspberry Pi

Well I may be watching just with the solar glasses since while everything else is on hand and ready to go the RasPi HQ camera has decided to play hide and seek.  I know I've seen it somewhere in the last few weeks but danged if I can find it now!  Time to tear the shack apart in search of that sucker.  Shack, not workshop, since it is my radio Ham Shack.

And maybe we should move this back and forth conversation to a new thread and quit adding to this video thread.

N4TTY

Posted by: @codecage

↑

And maybe we should move this back and forth conversation to a new thread and quit adding to this video thread.

While I would normally concur I think in this case we can keep the thread going, as long as we are discussing the sun camera or solar eclipse. 

I'm getting pretty excited as our weather forecast is looking great - mainly sunny on Monday with a high of 14 degrees Celsius. And the weather for Sunday and Tuesday is the same.  But between now and Saturday it's going to be terrible, and there is a very good chance that we will mark the 1 year anniversary of our ice storm with another ice storm this Thursday.

Posted by: @codecage

↑

the RasPi HQ camera has decided to play hide and seek.  I know I've seen it somewhere in the last few weeks but danged if I can find it now! 

I suspect it is hiding with my missing lenses. When I bought my first Pi HQ Camera I also purchased three lenses for it. I have no idea where I put two of them, which is annoying as they were a bit expensive.

Now I just have to keep away from Amazon, or I'll buy a solar tracker for only 800 Canadian dollars! A bit expensive for 3 hours of fun, and there are other things that I probably need more than that.  But it would be cool, and if I act in the next hour it will be delivered on Friday!

Posted by: @zander

↑

I am on here almost constanatly.

The understatement of the century LOL!

😎

Bill

 

 

@zander Wow, that is a really helpful post, full of good ideas and information.  Thank you.

Posted by: @zander

↑

Off the top of my head based on the type of questions you are asking, I think your tripod/tracking is not up to the job, I doubt you have current software and are up to speed on how to use it.

It's the "up to speed" part that is the biggest challenge.  The Meade mount will handle the tracking, but I haven't used it in a long time so I need to relearn how to set it up.  I've read some online guides for how to do an alignment during the day, but it obviously won't be as accurate as if I could use some actual stars to let the software calibrate it properly.  Best bet would be to set it up a few hours before dawn, but that may be impractical for a number of reasons. 

And without a working display on the controller, I would have to use software to control it.  There are several good products that can do that (Solarium, SkySafari and others), but again I need to set it up and become competent with it which is a challenge considering the weather forecast for this week.

The tripod for the camera is a different story, no tracking to be had there.  My thought was to set the lens so that it would keep the sun in view for the full length of totality, and your guidance on that gives me a lot to go on.

Posted by: @zander

↑

Lets try some simple math, the sun is on a 24hr journey, that's 1,440 minutes. The suns apparent size is 1/2 a degree so the sun travels from one edge to the other in 2 mins. (360/720 = 1/2 degree, 1440/720 = 2 minutes)

I had trouble interpreting that, but I think I get it.  I couldn't figure out what "edge" you were talking about, but now I think you mean this is the time for the sun to move one "sun-width" in the sky.  In other words, the time it would take for the sun's east edge to reach the point where the west edge was at the start.  If that's correct, and it takes 2 minutes, then if the sun fills no more than 1/3 of the camera view, it should remain within the frame for 4 minutes.  (Of course that depends on having the camera oriented so that the sun is moving truly horizontally across the frame.)  Based on the image that you sent, the Sony lens should give me enough room even at full zoom (600mm equivalent).  

Totality here will last more than 3 minutes, so that might work out.  I would need to allow some lead time to set it up, and I'd need to practice it so I might be "up to speed". 

My Sony RX-10 uses a 1" sensor that is significantly smaller than your APS-C, and I would be using only a fraction of it for the actual image of the sun.  I think I can set the camera to bracket each shot with up to 9 images for each shutter click.  I need to see how long that takes so I can set the intervalometer so that it and the camera can be in sync.  If I can get to so some practice shots, I can try to see whether or not the resulting image is worthwhile.  Obviously there will be plenty of people with better equipment than mine doing the same work, so I don't really "need" to do this at all.

Posted by: @zander

↑

I am further along and still won't attempt to take any pictures, it's just too much effort and YES, the photographer at any kind of event does not get to enjoy it as he is hussling to get it all correct. Easier today with digital and computers, but some parts are the same.

Yes, I get that.  I'm gathering the information and skills so I can do this if I decide to, but I still may skip some or all of it and just enjoy the show.  And even that is very dependent on the weather.  But even if I opt to skip it entirely and just watch through the glasses, I'm still learning a lot from the process.  Oh, that reminds me - I need to cut up a pair of those glasses and tape the filters over the objective lenses of my binoculars.  That might be my best option.  And that brings me back to this:

Posted by: @zander

↑

Be very careful with both camera sensors and human eyes even during totality.

Everything I've read suggests that it should be safe to look at the sun during totality.  I've never seen a total eclipse directly, so I don't have much to go on.  Some of the eclipse apps have features to tell you (with actual voice prompts) exactly when it is safe to remove your glasses and filters and then when to put them back on.  Can you elaborate on "being careful even during totality"?

@jimgilliland I thought and still do that even at totality there is a risk to eyes and cameras. It will be quite dark, so your eyes will be wide open. Our eyes are an analogue device and adapt slowly to change so if there is a large coronal event, you could be exposed to a lot more dangerous illumination suddenly. I have been to a few star parties and there is always someone with a solar scope and they all said the same thing, it's just not worth the gamble. 

And yes you got it, a sun's width.

If you get the scope tracking, mount the camera on top. I use a ball mount, there is normally a 1/4-20 thread somewhere on the scope that you can use with an adaptor. Before I sold all my stuff I had a box full of misc stuff like that. Head on over to a photo store and hopefully they will have what you need. If there is no built-in spot, see if you can rig something with a large hose clamp.

If I was 20 years younger I would be all over this but I can't plan on any future events as I don;t know from one day to the next if my heart will be normal or not. I am lucky to get 2 or 3 good days a week, hopefully, when I get to see the cardiologist he will agree with my Dr that I need a pacemaker. Apparently, that will make a HUGE difference.

Here is a question that does come fully back to the topic of Bill's original article:  What exactly will the Pi HQ camera be able to see through my ETX-105?  What will be the field of view?  Will I need a focal reducer?

Meade ETX-105AT 4.1" (f/14), 1470mm Focal Length Maksutov-Cassegrain Astro Telescope with Standard Coatings, Motorized Altazimuth Mount, Autostar Computerized Controller & Tripod.

Posted by: @zander

↑

If you get the scope tracking, mount the camera on top. I use a ball mount, there is normally a 1/4-20 thread somewhere on the scope that you can use with an adaptor.

I thought about that.  The scope does have a mounting block - I assume it is so you can use the optical tube on a different mount.  It is exactly opposite the eyepiece, which may be ideal for a connecting the tube to a mount, but certainly not ideal for mounting a camera. 

The scope does have the ability to move the eyepiece mirror and let the image come to a port right on the back of the scope, but the fork doesn't give a lot of clearance.  I'd have to play with it and see how well the camera would work in that position.  In theory, the image should be at least slightly better because one mirror would be eliminated.  Maybe that would make it easier to mount the Sony camera to the scope?  I have no idea who would sell this kind of stuff locally, but Amazon might have something that can be here tomorrow.  🙂

Seems that I need to spend some more time with Google trying to get answers to some of these questions.  I'm sure someone somewhere has mounted a camera on this scope and then written about it.  🙂

PS - take good care of your heart.  I wish you the best.  I'm an old dude, too (73), but so far the heart seems OK.  

Hmm.  I will attempt to answer my own question.  It seems that with a sensor as small as the one on the HQ camera (6.287mm x 4.712mm), the "crop factor" will be about 5.7.  5.7 * 1470 is over 8000.  An 8000mm lens would have a field of view of about 0.25 degrees.  Roughly half the apparent width of the sun.  So even with a focal reducer (which are largely out of stock everywhere at the moment), this telescope is not going to be suitable for eclipse photography with such a small sensor.  I would need a telescope with a much smaller focal length, or a camera with a much larger sensor, or both.  

Does anyone see any errors in my calculations?

Later edit:

I found a site that seems to confirm this.  This site attempts to show you what an object will look like using a given telescope and eyepiece or camera.  It did not have the HQ camera as an option, so I called it a custom camera and told it the sensor size.  It also wanted to know the pixel size, so I divided physical width of the sensor by the horizontal resolution (6.287mm / 4052 = .00115mm = 1.55um).  In the resulting view, the sun more than filled the image.

 

@jimgilliland If you want to mount the camera to the etx-105, you remove the lens from the camera and insert a camera adapter in the scope (a 1.25" IIRC, otherwise a 2") you then attach another adapter that threads onto the end of the first adapter and terminates in the connection your camera needs.

Sorry, I can't remember the math but I can almost guarantee you it will work.

Posted by: @zander

↑

@jimgilliland If you want to mount the camera to the etx-105, you remove the lens from the camera and insert a camera adapter in the scope (a 1.25" IIRC, otherwise a 2") you then attach another adapter that threads onto the end of the first adapter and terminates in the connection your camera needs.

Sorry, I can't remember the math but I can almost guarantee you it will work.

Oh, you're talking about using my Sony as the camera that looks through the scope.  I thought you meant that I should piggyback the camera (using its own lens) on the scope just to take advantage of the tracking.  Yes, that might work.  I don't have the telescope adapter for the Sony, but it might be possible to buy one.  

That wasn't part of my plan.  I had planned to use the Pi HQ camera on the scope, and use the Sony (with its long lens) independently.  

The Sony does not have a removable lens, so I would have to shoot through its existing lens, probably using the widest setting that would avoid vignetting.  But the Sony is a pretty heavy camera.  I'm not sure it would work well with such a small scope.  

I'm not sure I want to head down yet another path.  🙂  Seems like I'm already exploring too many options.  🙂

Posted by: @jimgilliland

↑

I found a site that seems to confirm this.  This site attempts to show you what an object will look like using a given telescope and eyepiece or camera.  It did not have the HQ camera as an option, so I called it a custom camera and told it the sensor size.  It also wanted to know the pixel size, so I divided physical width of the sensor by the horizontal resolution (6.287mm / 4052 = .00115mm = 1.55um).  In the resulting view, the sun more than filled the image.

Just to compare, Bill's little 50mm solar scope has a focal length of 360mm, about 1/4 of mine.  The sun will fill just about half the frame of the HQ camera from side to side and from top to bottom.  Pretty much perfect for this project.  It wouldn't be good for much else, but since it has a solar filter as a permanent part of the scope, that's all it can be used for anyway.

I could run down to Best Buy and pick one up for $100, but I'm not sure I will.  I guess I can keep an eye on the weather.  

I wonder how much they will be marked down on Tuesday.  🙂

Posted by: @jimgilliland

↑

Pretty much perfect for this project.  It wouldn't be good for much else, but since it has a solar filter as a permanent part of the scope, that's all it can be used for anyway.

  Exactly my reason for choosing it. That and the fact it was so cheap!

Posted by: @jimgilliland

↑

I wonder how much they will be marked down on Tuesday.  🙂

LOL! You might be able to get a good deal. And the Sun will still be there the next day and for about 5 billion years after that. Plus, there is an eclipse every 18 months somewhere on Earth.

Posted by: @jimgilliland

↑

I guess I can keep an eye on the weather.  

  As we all are. I'm pretty excited about our forecast. I'm monitoring six weather services, and they all say either "Sunny" or "Mainly Sunny"!  Of course, a lot can happen in 5 days, and we are expecting a major storm this afternoon that may last until Saturday. 

😎

Bill

 

 

 

 

Posted by: @dronebot-workshop

↑

I'm pretty excited about our forecast. I'm monitoring six weather services, and they all say either "Sunny" or "Mainly Sunny"!  Of course, a lot can happen in 5 days

"A shower in spots in the morning; otherwise, intervals of clouds and sunshine; the temperature can drop several degrees during the eclipse"

That's what they are saying for my neighborhood, and it's actually an improvement over yesterday.  

As for scopes, there are about a thousand on Amazon that would work fine if a solar filter could be put on them, and a few of them could even be delivered tomorrow.  I made a filter for my little reflector, but I didn't look carefully at the relationship between the sensor size and the focal length until yesterday, so if I were going to buy one, I'd want to make sure I could adapt my filter to fit it.  Unfortunately, most of them don't tell me the outer diameter of the objective end of the scope, so it's hard to guess.  

The metal part is a wall port for a dryer duct.  The inner surface is a felt "ribbon" with an adhesive on one side.  It's sized to the almost 5" diameter of my Meade scope, but I've got more felt.  🙂

Of course, most of those cheap scopes are pretty much just toys.  Maybe I could find one that could be given to my grandchildren.  I haven't decided yet - that weather forecast is too uncertain.  But obviously I can't wait too long or I will be limited to those at Best Buy.

I saw Riders in the Sky in concert a few years ago.  During the show "Too Slim" said to "Ranger Doug", "There are no more trail drivers, there are just bowlers and online shoppers."  And I'm no bowler....  🙂

@jimgilliland I am fairly sure you know, but if you have an ongoing interest in solar observing, there are specially designed scopes for that. I tried one out at a star party a few years ago and was impressed enough to put it on one of my todo lists. I might move that up in priority as it does offer the advantage of not having to stay up all night which is much harder at 82 than it was at 72 and there is less chance of mosquito bites. The gold standard in these scopes is Coronado (or Lundt if money is no object). They are extremely good and priced accordingly. I think that is what stopped me before, I could get a smallish Coronado, or a big Newt for the same money. Surprise surprise I went for the bigger. But that is gone for a few reasons so time to reconsider.

 

@zander Thank you.  Yes, I'm aware of them, but have never really looked at them.  I'm not sure I will have an ongoing interest in this.  The eclipse and Bill's project brought it all to the surface, but as you may have guessed, my little Meade scope hasn't been used in several years.  

If I were to buy anything right now, it would probably be a little toy scope with a 400mm focal length that I could use on Monday and then give to my grandkids.  But with the iffy weather forecast, that may not be a great choice.

The better choice may be to just use my protected binoculars on Monday.  Depending on the weather, maybe set up my Sony camera to take bracketed photos with the intervalometer (with an ND filter that blocks 99.999% of the light).  Maybe set up the Meade with the solar filter and an eyepiece suitable for the eclipse and use it visually.  Give my neighbors a good look.  I've got a few extra pairs of eclipse glasses to hand out.

Then sometime in the future buy a 3:1 focal reducer so I can use the HQ camera with the Meade for day or night.  With the reducer, I could use it for full images of the sun and moon or for some DSOs.  Without the reducer, I could use it for closer looks at parts of the sun or moon.  And with a Barlow, it might give pretty good images of Jupiter and Saturn.  

That may be the best way to take advantage of the investment of time and cash that went into this.  

@jimgilliland Sounds like a plan.