Question about short refractors and solar eclipse imaging

Phil Creed:
Ideally, I'd like to image the 2024 total solar eclipse using my NP101.

But one thing I haven't accounted for is if we're packing for four people, taking my mount and the NP101 might not be possible.

So a thought had occurred to me--take my small mount (SW Star Adventurer GTI) and my AT60ED, since I have a white-light solar filter for both OTAs.

My concern is focal length.  I'll only have 288mm with the 0.8X reducer and 360mm natively.  Ideally, if I could match the 540mm of my NP101, that would be great, and 720mm from a standard 2X barlow wouldn't suck, either.

...?  And then, it occurred to me--what about field curvature?

If I try to barlow my way to more focal length with the AT60ED, can a standard 1.5X barlow reduce field curvature enough to keep both the sun and outer corona streamers sharp with an APS-C sensor?  That would be 1.7° x 2.5° by my math.

Or should I just call it good with a flat 288mm and just crop if needed?

Clear Skies,
Phil

Phil Creed:
What's an MTO?

Clear Skies,
Phil

Presumably a Maksutov-Cassegrain: https://mrmarc.com/mto-1000am-10-51100mm/

Phil Creed:
Would something like a 500mm f/8 Tamron mirror lens work?   Those are dirt cheap.  Not sure about image quality.

Kevin Morefield:
This all depends on what features of the eclipse you want to capture and somewhat about the eclipse itself.  The 2024 eclipse is a pretty long one which means the Moon is going to hide a lot of the prominences and inner detail for most of the eclipse.  It’s also near a solar maximum which should mean more extended streamers.  And with the Moon more fully covering the Sun and its bright chromosphere, it should be easier to see the dimmer stuff and Earthshine.  So on this one I would be focused on shorter FL, longer exposures to get the most extended corona and make sure it is in the frame.  That doesn’t mean you won’t be able to capture prominences, Bailey’s beads and other close in detail in 2024, it’s just going to be a smaller part of this eclipse.

I shot last week’s short eclipse (48 seconds for me) with a 400mm telephoto and Sony full frame camera.  That 400mm lens versus telescope decision was driven by wanting to travel to Australia very light and not the ideal choice given that I was interested in the inner corona and prominences.  My brackets went down only to 1/13th of a second but still I filled most of the frame (on the short side at least) with corona.  See here for uncropped at 400mm: https://www.astrobin.com/s12byw/B/

I think my FSQ106 at 530mm would have been ideal here since I think it is sharper than the lens and would have still captured the corona OK.  With 2024 I will be shooting longer exposures and I expected to fill the frame completely.  

I think your NP101 would be a great choice for 2024.  At least with full frame.  Unless you want to go for the inner stuff and let the extended corona run off the edge.  Then something like 700-800mm would be better.  288mm is pretty short. 

Kevin

Phil Creed:

Kevin Morefield:
This all depends on what features of the eclipse you want to capture and somewhat about the eclipse itself.  The 2024 eclipse is a pretty long one which means the Moon is going to hide a lot of the prominences and inner detail for most of the eclipse.  It’s also near a solar maximum which should mean more extended streamers.  And with the Moon more fully covering the Sun and its bright chromosphere, it should be easier to see the dimmer stuff and Earthshine.  So on this one I would be focused on shorter FL, longer exposures to get the most extended corona and make sure it is in the frame.  That doesn’t mean you won’t be able to capture prominences, Bailey’s beads and other close in detail in 2024, it’s just going to be a smaller part of this eclipse.

I shot last week’s short eclipse (48 seconds for me) with a 400mm telephoto and Sony full frame camera.  That 400mm lens versus telescope decision was driven by wanting to travel to Australia very light and not the ideal choice given that I was interested in the inner corona and prominences.  My brackets went down only to 1/13th of a second but still I filled most of the frame (on the short side at least) with corona.  See here for uncropped at 400mm: https://www.astrobin.com/s12byw/B/

I think my FSQ106 at 530mm would have been ideal here since I think it is sharper than the lens and would have still captured the corona OK.  With 2024 I will be shooting longer exposures and I expected to fill the frame completely.  

I think your NP101 would be a great choice for 2024.  At least with full frame.  Unless you want to go for the inner stuff and let the extended corona run off the edge.  Then something like 700-800mm would be better.  288mm is pretty short. 

Kevin

The NP101 would be the weapon of choice.  It's a question of whether I'll have enough room to transport it and my HEQ5 + tripod + counterweights and 12V power supply along with luggage for my wife and kids on potentially a cross-country trip.  I live in the path here in NE Ohio, but I'm not counting on it being clear here.  That's precisely why I have a hotel reservation along the path's edge in Arkansas as a contingency measure.

One thought I did have was swapping my AT60ED for an AT72EDII and getting the 72's 1.0X flattener for 432mm @ f/6.0.  That should easily ride on my Star Adventurer GTI mount if I need to go that route.  The GTI can run off AA batteries in a pinch.

Of course, another thought had occurred to me--get the AM5 mount.  That saves a lot of weight and space vs. the HEQ5 and its tripod.

Clear Skies,
Phil