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Questions re: solar imaging using my Edge 8 + Daystar Chromosphere

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#1 jerahian

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Posted 27 February 2020 - 09:30 PM

I'm thinking about getting a Daystar Chromosphere to do some solar imaging (and visual), but I'm not 100% sure of what all I would need to do so with my EdgeHD 8.  So, I have a few questions:

 

  • I've read about needing ERFs for apertures > 80mm, but I can't figure out if this is some special expensive blocking filter I have to add to the front of my SCT or if a UV/IR cutoff in front of the Chromosphere would suffice?
    • In lieu of the EdgeHD 8, would my ES ED127 refractor be better for this?  What would the ERF requirements be for that?
  • Would I place the Chromosphere where an eyepiece would normally go inside a diagonal even for imaging?
  • I'm thinking imaging would be with an ASI224MC.  Would this work OK?

 

Help in making sense of this would be appreciated.

 

Thanks!



#2 MalVeauX

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Posted 27 February 2020 - 10:18 PM

Hey Ara,

 

To use an SCT, you would need a full aperture D-ERF to handle the thermal load. This will cost minimum $2k, plus another few hundred for a holding cell to mount the D-ERF. The Quark's specifications for 80mm aperture or more is only applied to refractors; not to folded optic designs like SCT. You need full aperture for SCT, Newtonian, etc, for a D-ERF, which means huge costs. A D-ERF is very much a narrowband filter (dielectric at best), so you know at 8" it will cost you not only premium but custom costs.

 

Your 127mm refractor will work with a Quark without anything special beyond a basic UV/IR block filter in front of the Quark. This is more realistic. It is still subject to seeing limitations.

 

Seeing conditions during the day, need to be sub-arc-second seeing to try to realize the resolution of 200mm during the day. So unless you're in a very special geographic place on Earth where seeing is less than 1 arc-second sustained per minute, do not bother with 8" or greater apertures for day time solar imaging. I say this as someone who experiences this in Florida and I have an SSM monitor to get measurements. I also have a C8 Edge, D-ERF and Quark setup that I've imaged with. It's not as simple as just buying the equipment. You must have excellent seeing conditions to realize the resolution. There's no magic bullet to this, you must have sub-arc-second seeing conditions to image with 8" aperture at critical sampling for solar during day time. Otherwise, you might as well use smaller aperture. There's no way around this.

 

I cannot stress enough, do not think its a matter of getting the gear. The seeing is what matters. Day time seeing is way, way, way worse than night time seeing. You will find for your area, there is a specific time of day that seeing is ideal. You can only attempt high res imaging then. Even then, it better be sub-arc-second sustained per minute, or you will not get 200mm aperture resolution potential.

The Quark has an internal 4.3x telecentric amp. Use that to figure your focal-ratio and effective focal length. Now consider your 224MC sensor's 3.75um pixels. You will be using a 0.5 focal reducer most likely to get things more reasonable for sampling at those image scales.

 

Your refactor is much more likely to be a successful option for imaging like this.

 

Here's a place to get an idea of your seeing conditions: https://www.meteoblu...merica_11395215

Plug in your location. Maine is not known to have great seeing. 2" seeing is not going to support 8" aperture. That's 102~127mm aperture at best based on conditions.

 

Here's my C8 Edge, plus a full aperture D-ERF (Aries) in a T.S. made cell holding mount with my Quark, along with 0.3"/pixel image scale captures I've done recently (spring of 2019):

 

47106519952_ee10e4a872_c.jpg

 

47631283031_260ca026f4_c.jpg

 

32651905897_37f3db8d8f_c.jpg

 

This is not the results you can get from 1.5~2 arc-second seeing. This requires 0.7~1 arc-second minimum, sustained, seeing during the day. This is with the exact system you propose. This is only an option for a very few places on Earth honestly.

 

That said, let's look at what you can do with a mere 120mm aperture refractor, an achromatic, not even an ED doublet or more, with a Quark. No expensive D-ERF needed, just the internal UV/IR block filter in front of it, under ok seeing conditions (2~3 arc-second conditions):

 

120mm frac with Quark (no big front mounted full aperture D-ERF; Celestron Omni XLT 120mm F8.3 achromatic doublet + Quark):

 

34313004040_6b89716650_c.jpg

 

35361200432_db6c98ef4e_c.jpg

 

35915185303_0649b0209d_c.jpg

 

Very best,


Edited by MalVeauX, 27 February 2020 - 10:37 PM.

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#3 jerahian

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Posted 27 February 2020 - 10:45 PM

Marty, first off, those image are amazing!  Thank you for sharing.

 

Second, I hadn't thought about daytime seeing for solar, and you're right, I will NEVER get sub-a.s. seeing in Maine :(  It just doesn't happen even for nighttime AP.

 

So, now that we've ruled out the Edge 8 for solar imaging, how would you compare:

  • a dedicated solar scope, like a SolarMax, single or double etalon 70 or 90mm vs.
  • a Chromosphere on my ES ED127

I know the cost of a dedicated SolarMax is about 3x, but would the tuned Ha filters in the dedicated setups provide richer contrast for both imaging and viewing, given the limitation in resolution at my location?  I understand you may not have experience with either of these setups, but your opinion would be appreciated!

 

Thanks!



#4 Tulloch

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Posted 27 February 2020 - 10:46 PM

Extraordinary - I can see why people get into solar photography with images like these jawdrop.gif



#5 MalVeauX

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Posted 27 February 2020 - 10:51 PM

Heya,

 

I have 40mm double stack, 60mm double stack and anything from 40mm to 200mm single stack at my disposal.'

 

In 2" or 3" sustained arc-second seeing, I would suggestion anything 127mm or less will be ok on average, smaller is better.

 

A double-stacked 90mm system is honestly a life-time system. I would take it over a 120~127mm single stack, any day, for solar.

 

The least expensive way to view high res solar, with a single stack, is a 102mm~127mm aperture frac and a Quark.

Imaging and visual are two different beasts. I can show examples for several setups. But it's not going to matter unless your seeing supports it.

 

Overall, if I were to suggest something... I would endorse an 80~90mm double stack option for visual, or a 80~127mm single stack option for imaging not knowing a metric for your seeing conditions.

 

Very best,



#6 jerahian

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Posted 27 February 2020 - 11:22 PM

Well, your edited post gives me some hope to ease into solar imaging without breaking the bank.  And, now I know the upper end of what is possible, knowing that my local seeing conditions in Southern Maine will ultimately prevent me from getting there.  Tomorrow, for example, my daytime seeing on MB starts at 2.4 as, peaks at 3.35 as, and backs down to 2.7 as near dusk.  Not great :(

 

So, taking your advice, I might just try the Chromosphere with my existing 127mm frac as the easiest entry into solar imaging  and save for a 90mm double-stack once I have a couple of years under my belt.

 

I know I mixed imaging and visual in my initial question, which probably has gotten me a bit confused now, but would my 127mm + Chromosphere do OK for visual (as limited by my seeing)?  Specifically, would one be able to see proms if they're there with that combo?

 

Marty, thank you very much for your detailed assessments and pictures!



#7 MalVeauX

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Posted 28 February 2020 - 07:41 AM



Well, your edited post gives me some hope to ease into solar imaging without breaking the bank.  And, now I know the upper end of what is possible, knowing that my local seeing conditions in Southern Maine will ultimately prevent me from getting there.  Tomorrow, for example, my daytime seeing on MB starts at 2.4 as, peaks at 3.35 as, and backs down to 2.7 as near dusk.  Not great frown.gif

 

So, taking your advice, I might just try the Chromosphere with my existing 127mm frac as the easiest entry into solar imaging  and save for a 90mm double-stack once I have a couple of years under my belt.

 

I know I mixed imaging and visual in my initial question, which probably has gotten me a bit confused now, but would my 127mm + Chromosphere do OK for visual (as limited by my seeing)?  Specifically, would one be able to see proms if they're there with that combo?

 

Marty, thank you very much for your detailed assessments and pictures!

Heya,

 

Your 127mm and a Quark will be great for visual (especially with binos) and for imaging, even at 2.4~2.7 arc-seconds seeing conditions. That's the sustained average, there will be spikes of good seeing and that's what lucky imaging is all about. And if seeing is really poor, you can mask your refractor to 80mm or 102mm for example. Totally fine to go big on refractors with this, since you can mask them as needed. Put in some binoviewers (no GPC needed with the Quark) and you're set, I would target 32mm~25mm to start out.

 

This will be super helpful:  http://www.scopestuff.com/ss_solf.htm

 

Here's some info to get you started:

 

https://www.cloudyni...-jan-20th-2020/

 

https://www.cloudyni...-jan-16th-2020/

 

49503136771_a0a3fc6a32_c.jpg

 

Very best,


Edited by MalVeauX, 28 February 2020 - 08:17 AM.

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