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Vexxing Issue

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#1 FourSpeed

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Posted 22 March 2024 - 01:44 AM

Hi Guys & Gals,

 

1st post here... In getting ready for the 4/8/24 Eclipse, I'm having a vexxing issue, and I'm about out of ideas, and would appreciate any help / suggestions.

 

For the 2017 eclipse, I photographed it with my smartphone attached to a pair of Celestron Skymaster 15X70 binoculars, and they turned out .... ok ... but not great... (sadly, I wasn't able to get the phone / attachment to work with my scope at all).

 

For this eclipse, I'd like to do it through my telescope.  I have a Celestron 130 SLT (that I've enjoyed the heck out of for years). I picked up a SVbony SV305C eyepiece camera, and have been monkeying around with the combo for the past few weeks.

 

Overall, I've really liked the shots I've been getting (included one from today's session for reference), but here's the problem.

 

Excluding my 9mm eyepiece, all the other eyepieces I have show a lovely full disc solar view in the scope.  However, when I switch to the digital camera, it's FOV seems so small that I can only capture 1/3 - 1/2 of the solar disc. While I like the pics that come from that, it's obviously lacking when it comes to imaging the full disc eclipse.

 

I also tried adding a 0.5x focal reducer, but alas, I can't get it to focus before the focuser rack reaches its inner travel limit.

 

 

I know that I could, again, use the binocular approach, but I find that option very unpleasing and discouraging....  At this point, I'm actually wondering how all the full-disc pics I see of the Sun, (or moon, for that matter) are actually being captured (with a telescope) as I don't seem to be able to "get there from here".

 

Which puzzle piece am I missing???

 

Any insight you could share would be most helpful.

 

 

Thanks in Advance, 

4

 

 

 

PS> I'm using the current free version of SharpCap to grab the image....

 

16_27_31_post.jpg


Edited by FourSpeed, 22 March 2024 - 01:53 AM.

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#2 foxwoodastronomy

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Posted 22 March 2024 - 06:33 AM

It seems like the small sensor in that camera combined with the position it is ending up in the image circle formed by your telescope is creating a mega-crop factor.  Like DSLR small sensor cameras do, but you have it on a more problematic level.  You may not be able to physically do it, but you have to get the camera sensor much closer to the tube of the telescope, to try to get the smallest diameter of the image circle.  This is what I mean as it relates to DSLRs.  You have a crop factor like crazy.  I had a similar problem when putting a Nikon Z50 on the back of an ETX.  I had to buy a shorter adapter to get the camera closer to the back of the ETX to get more margin around the Sun. Gordon

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Edited by foxwoodastronomy, 22 March 2024 - 06:55 AM.


#3 AsleepAtTheScope

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Posted 22 March 2024 - 07:11 AM

Hi Guys & Gals,

 

1st post here... In getting ready for the 4/8/24 Eclipse, I'm having a vexxing issue, and I'm about out of ideas, and would appreciate any help / suggestions.

 

For the 2017 eclipse, I photographed it with my smartphone attached to a pair of Celestron Skymaster 15X70 binoculars, and they turned out .... ok ... but not great... (sadly, I wasn't able to get the phone / attachment to work with my scope at all).

 

For this eclipse, I'd like to do it through my telescope.  I have a Celestron 130 SLT (that I've enjoyed the heck out of for years). I picked up a SVbony SV305C eyepiece camera, and have been monkeying around with the combo for the past few weeks.

 

Overall, I've really liked the shots I've been getting (included one from today's session for reference), but here's the problem.

 

Excluding my 9mm eyepiece, all the other eyepieces I have show a lovely full disc solar view in the scope.  However, when I switch to the digital camera, it's FOV seems so small that I can only capture 1/3 - 1/2 of the solar disc. While I like the pics that come from that, it's obviously lacking when it comes to imaging the full disc eclipse.

 

I also tried adding a 0.5x focal reducer, but alas, I can't get it to focus before the focuser rack reaches its inner travel limit.

 

 

I know that I could, again, use the binocular approach, but I find that option very unpleasing and discouraging....  At this point, I'm actually wondering how all the full-disc pics I see of the Sun, (or moon, for that matter) are actually being captured (with a telescope) as I don't seem to be able to "get there from here".

 

Which puzzle piece am I missing???

 

Any insight you could share would be most helpful.

 

 

Thanks in Advance, 

4

 

 

 

PS> I'm using the current free version of SharpCap to grab the image....

 

attachicon.gif 16_27_31_post.jpg

As foxwoodastronomy points out, your camera sensor is very small. Your 130 SLT has a focal length of 650 mm while your camera sensor has a width of about 5 mm. I get a FOV of 26 arc min for that combination which is less than the about 30 arc min diameter of the Sun.

 

Other people use larger sensors and/or a shorter focal length telescope or lens. Your camera has about 1/40 the area of a full frame DLSR. You could try adjusting the primary mirror to be closer to the secondary so it focuses with the focal reducer but you can probably only move the mirror a fraction of an inch.

 

If you're only trying to get the partial phase then your current setup will be ok (but not full disk). If you're trying to get the corona, then it isn't going to work.


Edited by AsleepAtTheScope, 22 March 2024 - 07:12 AM.


#4 winbag4

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Posted 22 March 2024 - 07:53 AM

On the other hand, you could probably get some really spectacular close-ups of Baily's beads and prominences, if you know where to point.


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#5 Cajundaddy

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Posted 22 March 2024 - 10:29 AM

Hey, that is a really sharp image of the sun's surface with excellent sunspot detail.  Your focus and resolution are excellent.  

As explained above, for a full solar image including the outer corona you will need either less focal length or a larger sensor.  Not going to happen with your current setup.  You could shop for a good used full frame DSLR for $200-$300 or a small lens with 150mm focal length and attach this to the SLT mount and this would give you a wide field view.  

With a little practice you probably have the skill to shoot the eclipse with something like this and get great results.  How badly do you want it?

https://www.facebook...7f-e44a09071f6d


Edited by Cajundaddy, 22 March 2024 - 10:46 AM.


#6 FourSpeed

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Posted 22 March 2024 - 11:08 PM

Thanks for the responses.

 

I was afraid that the answer might be something along those lines...  frown.gif

 

@foxwoodastronomy:  Thanks for the detailed explanation. Your reply makes a lot of sense, and helps me better understand the "what" of the issue.

 

@Cajundaddy:  I appreciate the idea, but I'm not too keen on spending $$$ to go an entirely different route when I already have several hundred $$$ worth of astronomical equipment that is able to take quality pictures I'm pleased with -- my personal obstinacy insists that I try to shoehorn a viable solution into this setup... wink.gif smile.gif

 

@AsleepAtTheScope:  Unfortunately, you're right -- I really can't move the primary mirror much at all...   So, "if the mountain (mirror) won't move to Mohammed (camera), I guess I'll have to look at shoving Mohammed closer to it..."  wink.gif smile.gif

 

In looking closely at the scope again today, I think I may be able to 3d print something to insert the camera deeper into the focuser tube  (it has a 2" mount that the 1.25" eyepiece holder sets into, all of which can be easily unscrewed).  It should be simple enough to MacGyver a couple 3d prints to allow me to play around with camera distances and hopefully see if I can get that to solve the problem.

 

Again, thanks for your helpful replies / suggestions. I hadn't thought of printing my own inserts, until I read these replies...  I'll let you know how it turns out...

 

Off to 3d Builder now...     wink.gif lol.gif

 

 

Cheers,

4



#7 Messierthanwhat

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Posted 23 March 2024 - 09:41 AM

An option you may have overlooked, and that would allow you to use the camera you seem to know well, would be using the SV305 with a short-to-medium telephoto camera lens. I have the same camera, and have been using it  that way exclusively in the several years that I've owned it. "Vintage" lenses are readily available for small amounts on auction web sites and at thrift stores. There are C-mount adapters that will connect the SV305 with lenses for a wide variety of camera brands. Examples here. Lots of adapters are also available on ebay.

 

I know it's almost heresy to make such a statement here on CN, but solar imaging doesn't really demand premium optics. When the target is the biggest, brightest object in the solar system, you can stop these old lenses down to where their sharpness will rival almost any other optics you might choose. I've even seem some excellent solar images produced by devices that use lenses from dollar store reading glasses.

 

The image here shows my SV305 mounted to a Vivitar 250mm f/4.5 vintage telephoto with a Pentax K-mount, using a PK-to-C adapter. The longest lens I've used this way is a 350mm, and the disk of the moon barely fits on the sensor, so for a solar eclipse I would probably use something like a 135mm. Most 135mm telephotos don't have a tripod foot, but you might be able to find (or may already have) a telephoto zoom has has that feature and would provide a suitable focal length within its range. 

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Edited by Messierthanwhat, 23 March 2024 - 09:52 AM.

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#8 Cajundaddy

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Posted 23 March 2024 - 10:02 AM

FourSpeed,
Hey no worries.  We are all planning our TSE imaging in different ways and chasing our own objectives.  Lots of different ways to skin this cat and as long as we have the 3 elements of precise focus, exposures, and image scale nailed down we are sure to get something useable.  Right now your focus and exposure look excellent but image scale is about 5x too large to capture the outer corona which is 3-5 solar radius.  If you can find a .2x focal reducer it should get you pretty close, or you may redirect your efforts to get really good closeups of the inner corona and prominences at the limb which should be pretty fantastic.

It is interesting to see the many different variations of TSE imaging plans.  An eclipse is a comparatively large daylight object in the sky and over the last 20 years or so, 99.99% of the epic outer corona photo results have been done with a small refractor and DSLR or mirrorless camera. A well understood and well travelled path.  This year a whole lot of folks are choosing to use a variation on a DSO astro-camera which excels at capturing very small faint objects and are running into unexpected challenges.  Very different tools for different purposes and gentle nudging by others to carefully consider all three elements in choosing their imaging tools results in: "hold my beer..."  wink.gif

I am actually very interested in seeing the images you get with your planned setup.  You clearly have some solid skills and the results might be quite surprising.

Clear skies!


Edited by Cajundaddy, 23 March 2024 - 10:03 AM.

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#9 FourSpeed

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Posted 23 March 2024 - 03:36 PM

Thanks again, guys.

 

It's bleak and overcast here at the moment (weird for Arizona), but the 3d printer is humming away with the ideas from last night, so some interesting (and hopefully useful) tinkering should occur soon-ish.  wink.gif grin.gif

 

@Cajundaddy:  Agreed. There's no end of options to try out. I would have liked to get the scope working for the last TSE in 2017 (I did *observe* thru the scope, of course), but as mentioned in the OP, I wasn't able to get it to work satisfactorily, and I didn't have the SV305C (or a 3d printer) then either, just my smartphone. While camera-wise it is fine, connection-wise, it sucks.  lol.gif   If I manage to get things working and get any images I'm not completely embarrassed about, I'll post a couple here (even if I end up falling back to the binocular / phone approach). As for skills, you're too kind... I mostly chalk it up to repeated obstinacy over the course of a few decades of monkeying around...  wink.gif lol.gif

 

@MessierThanWhat:  That's an intriguing idea... The last time I had a *real* camera, rather than the common phonecam approach these days, was back in the 80's somewhere with a Minolta X700, so your idea never even entered my head.  Amusingly, after looking in the bag, I still actually have a 135mm lense in there (though the camera is long-since defunct). For the price of a $15 C-mount, that might be worth tinkering with as well...  I'll have to 3d print a solar filter holder for the lense, but that should be easy-peasy. If that setup works at all, it should also be fairly easy to piggyback it to the scope for solid tracking...  Hmmmm....

 

Once again, thanks guys for nudging my head into some different ideas, as I was getting a bit annoyed and frustrated with the current state of things atm... In any case, I'll keep you in the loop about what I end up with -- I've still got a few days to dabble until heading off to Kerrville....

 

 

Regards,

4



#10 FourSpeed

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Posted 31 March 2024 - 05:22 AM

Update:

 

Well, with a week to go before travelling, I've pretty much learned that there's little I can do with the scope itself to get a full disc image. While the 3d prints I played with for the focuser allowed me to place the camera 1-3" (appx.) closer and further from the normal focusing point, I wasn't able to get a smaller, useable image of the full solar disc...  frown.gif bawling.gif

 

That said, @MessierThanWhat  suggestion of using a zoom camera lens with a C mount for the SV305C worked out pretty well -- certainly better than my backup plan from 2017 of a cell phone on a pair of binoculars...

 

So, that's what I'm going with... Weather permitting (fingers crossed) I'll get a reasonable set of photos. The 135mm has enough FoV that it should also capture a pretty good amount of the corona as well...  No award winning shots, wink.gif  but if it works better than 2017, I'll be pleased enough...

 

Once again, thanks for your suggestions, guys!  Much Appreciated.  waytogo.gif

 

 

Regards,

4

 

PS> I'm including a couple pics from the other day's testing...  1> 135mm shot   2> Scope shot.   The sun shots are 100 frame Quick Captures run thru Pipp and Registax (cropped & converted by Paint so they'll post here)...

 

X700_14_32_04_crop.jpg

 

C130_14_49_25_crop.jpg

 

 

 

 



#11 FourSpeed

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Posted 31 March 2024 - 05:24 AM

...and finally, here's the scope setup I'll be taking along....

 

Cheers,

4

 

 

C130-Setup_crop2.jpg

 



#12 FourSpeed

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Posted 12 April 2024 - 01:39 PM

Back from the Eclipse Trip.  We were at Stonehenge II in Ingram / Kerrville TX area.  The Weather was essentially overcast and crappy.  frown.gif

 

The scope setup worked fine, but we were only catching glimpses (a few seconds each in duration) throughout the first half partial, and totality, and almost nothing for the second half partial.

 

Here are a few pics. The first two were mine, the 3rd (and best) was from one of the other fellows with us (Sorry, don't know the equipment he was using).

 

Anyway, I appreciated all your advise - the setup was great despite the eclipse itself being mostly a bust for us due to the weather.

 

 

Regards,

4

 

 

 

 

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