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Ha Full Solar Disc - Jan 22 2019

solar imaging astrophotography
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#1 RickV

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Posted 23 January 2019 - 07:56 AM

Hi All,

 

Conditions were poor... poor 'seeing', poor 'transparency' and wispy tendrils of cloud covered the sky.  But it was sunny! lol.gif

 

Here's what I managed...

 

Merge 11_46_49Prom & 11_18_46Surf Colr 900.jpg

 

Best,

Rick


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#2 MalVeauX

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Posted 23 January 2019 - 08:42 AM

Nice Rick, the little sunspot group is persisting!

 

All clouds here.

 

Very best,


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#3 petert913

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Posted 23 January 2019 - 09:18 AM

I hope the sun is enjoying his little nap these past few years.  Wake up, ya lazy lout !  lol.gif



#4 descott12

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Posted 23 January 2019 - 10:46 AM

Rick,

That is awesome. I am just getting into solar astronomy so it would help to know what you captured this image with (camera, quark, scope).  I am considering getting a Daystar SS60-ds with the integrated quark filter. Any comments on that?

Thanks



#5 RickV

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Posted 23 January 2019 - 11:18 AM

Hi Dave,

 

My scope is a Lunt LS50 with B600 diagonal/filter.  50mm objective lens of 350mm focal length, making it an f7 system.

My camera is a ZWO ASI 178MM that has a maximum square frame resolution of 2080 x 2080 pixels of size 2.4 microns.

 

For Ha imaging, the maximum pixel size that should be used for good image resolution = f# / 2.8.

In my case, maximum pixel size = 7 / 2.8 = 2.5 microns.

Thus, the ASI 178 with its 2.4 micron pixels is an excellent match to my system and I typically image with a region of interest of 1600x1600 pixels - that captures the full solar disc with space around it for the normal to larger size proms.

 

RE:  I am considering getting a Daystar SS60-ds with the integrated quark filter. Any comments on that?

Let's see...

DayStar Filters Scout 60mm DS Chromosphere Solar Telescope

- Tuned for Chromosphere Viewing
- 60mm Achromatic Doublet Refractor
- 930mm Focal Length, f/15.5 Focal Ratio
- Chromosphere Quark H-alpha Solar Filter

 

At that long 930mm focal length, you will never capture a full-solar disk in one image.  To image the full solar disc, you would need to stitch together a mosaic of multiple images - something most folks don't like to do.  Without doing a mosaic, that scope will restrict you to sunspots and prominences.

At f/15.5, the camera you ideally want would have a maximum pixel size = 15.5 / 2.8 = 5.54 microns.

The ZWO ASI 174MM with 5.56mm pixels would be an excellent match.

 

Best,

Rick



#6 descott12

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Posted 23 January 2019 - 02:35 PM

Hi Rick,

Thank you for such a helpful response.

 

Follow up:  

What is the max f ratio that I could have to see the full disk?

 

I kind of like the more closeups of just a part of the disk and the edge with proms so this f ratio may actually work well for me.



#7 RickV

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Posted 23 January 2019 - 05:03 PM

Hey Dave,

 

RE: Follow up:  What is the max f ratio that I could have to see the full disk?

It more a question of the maximum focal length and the number & size of the camera pixels.

 

Example 1

My LS50, 50mm objective, 350mm focal length is f7.

With the 350mm focal length, the diameter of the image of the sun with space around it for proms is 1600 pixels of size 2.4 microns with my ASI 178MM camera.  i.e. 1600 x 2.4 microns = 3.84 mm.

The maximum square frame of of the ASI 178MM is 2080 pixels of size 2.4 microns = 5.0 mm.

 

Given the limitations of the camera (max image size of 5.0mm), we can calculate to see what the max focal length could be.

Max focal length to use with the ASI 178MM would be, x / 350mm = 5.0 / 3.84, x = 350mm x (5.0 / 3.84) = 456 mm.

 

Now, I don't know if this would work in reality but...

Your 60mm objective, 930mm focal length is f15.5.  The f15.5 is required before the built-in quark for the quark to operate properly.  Some folks do add a focal reducer after their 'original quark' to lower the effective focal length and f#.  Whether than would work here, I can't say - having no first hand experience.

e.g.

If you added a 0.5X focal reducer after the quark and before the camera (eyepiece), you could possibly have...

930/2 = 465 mm focal length at f 15.5 / 2 = f7.75

Note that focal length of 465mm is just over the limit of 456mm for the ASI 178MM... so maybe you could capture the full solar disc with somewhat less space around the disc for proms.  The new f# of 7.75 is OK for the ASI 178MM camera; Ha max pixel size = 7.75 / 2.8 = 2.8; that is larger that the 2.4 micron pixels of the ASI 178MM so you are all good.

 

I think you need others with direct hands-on experience using a Quark & Focal Reducer to chime in here.

 

Best,

Rick



#8 descott12

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Posted 23 January 2019 - 06:05 PM

Thanks Rick. That makes alot of sense. I currently have an ASI 294Pro Color.  It has a 4.63 um pixel so it right on for f15.5. I know it is color which is not ideal and it is a 12 MB camera so I wonder how that will look. I guess it can't hurt to give it a try. 

 

I also have a NextImage 10 with 1.67 um pixels.  I think I will just experiment a bit and maybe look into getting the focal reducer.
Thanks for your help



#9 RickV

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Posted 23 January 2019 - 06:52 PM

RE: I also have a NextImage 10 with 1.67 um pixels.

I also have that camera but my 'basement tests' indicated that it was very insensitive to Ha.

 

Camera Sensitivty jpg.jpg

 

e.g.
In white light, the NexImage 5 was 250 / 91 = 2.75X as sensitive as the NexImage 10.

In Ha, the NexImage 5 was 6000 / 250 = 24X as sensitive as the NexImage 10.

 

Best,

Rick



#10 descott12

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Posted 23 January 2019 - 07:31 PM

Interesting. Not sure why I bought that camera...you live an learn.



#11 MalVeauX

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Posted 23 January 2019 - 08:00 PM

 

 I am considering getting a Daystar SS60-ds with the integrated quark filter. Any comments on that?

 

Don't bother.

 

If you're going to consider a Quark, get a stand alone Quark and use whatever scopes you want to.

 

Very best,



#12 descott12

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Posted 23 January 2019 - 09:25 PM

The Daystar SS60-ds is about half the price of the standard Quark ($695 compared to $1200). Plus, I only have a SCT and my understanding is the quarks work a whole lot better with a refractor so I would also have to get a refractor that has the proper f ratio. Seems alot simpler and cheaper to go the SS60-ds...



#13 MalVeauX

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Posted 24 January 2019 - 08:16 AM

The Daystar SS60-ds is about half the price of the standard Quark ($695 compared to $1200). Plus, I only have a SCT and my understanding is the quarks work a whole lot better with a refractor so I would also have to get a refractor that has the proper f ratio. Seems alot simpler and cheaper to go the SS60-ds...

If you're willing to pay $700 for a fused Quark in a small achromat, I would suggest you simply get a Lunt 50mm instead.

 

Very best,



#14 descott12

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Posted 24 January 2019 - 08:30 AM

If you're willing to pay $700 for a fused Quark in a small achromat, I would suggest you simply get a Lunt 50mm instead.

 

Very best,

Hmmm... I will check that out. I was thinking the Lunt's were alot more money. Thank for the tip



#15 descott12

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Posted 24 January 2019 - 09:01 AM

If you're willing to pay $700 for a fused Quark in a small achromat, I would suggest you simply get a Lunt 50mm instead.

 

Very best,

You are right! Definitely the way to go. Thanks



#16 descott12

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Posted 27 January 2019 - 02:47 PM

All,

I have been doing a little math and I was hoping you could verify my numbers. Assuming an ASI 294 camera with 4.63 um pixels and a 23.2 mm diagonal.

 

Scope                Aperture FL   f     FOV       Image scale  Max pixel size

                     (mm)     (mm)       (arc-min) (arc-sec/pix)(um)

-------------------------------------------------------------------------

Daystar SS6-ds       60       930  15.5  86        1.30         5.5 um

Lunt LS50THa-BP-600  50       350  7     228       2.73         2.5 um

 

The formulas I used are:

 

FOV = 3436*Diag(mm)/FL(mm)

‚ÄčImage scale = 206*pixelSize(um)/FL(mm)

Max pixel size = F/2.8

 

Since the Sun is only 30 arc-minutes across, it seems that both could do a full disk but my camera is matched much better to the Daystar. Plus, I think I could get better resolution on details/proms with the higher focal ratio of the Daystar.

Thoughts? Have I made any errors.

 

Also, they the claim the Quark Daystar is already effectively "double-stacked". This makes it much more cost effective for an equivalent Lunt if true.

Thanks in advance.

Dave


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#17 MalVeauX

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Posted 27 January 2019 - 03:00 PM

 


Also, they the claim the Quark Daystar is already effectively "double-stacked". This makes it much more cost effective for an equivalent Lunt if true.

Be very wary of this kind of marketing. It's not double stacked at all. It's not effectively near double-stacked either. I would take a Lunt over Daystar's latest entry level Quark-fused-achromat, Scout series, etc. And I would take a normal Quark over any of Daystar's "quark-scopes" and I would take a normal Quark over a small Lunt, but my interest is high resolution. If your interest is more full disc, then front mounted etalons like the smaller Lunts are a better way to go.

 

Very best,


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#18 descott12

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Posted 27 January 2019 - 03:18 PM

 If your interest is more full disc, then front mounted etalons like the smaller Lunts are a better way to go.

 

 

Hi Marty, actually my interest is more in the close-ups and not the full disk. That is why I thought the F15.5 might be better. My understanding is that scope has an identical quark unit but it is simply not removable. As I don't anticipate ever using it on another scope, I didn't think that was an issue.  The 60 mm aperture beats the Lunt's 50 and all for alot less cost. I figured the "double-stacking" claim was all marketing but I assumed that they were simply claiming that the results were good.   This is a tough decision...


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#19 MalVeauX

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Posted 27 January 2019 - 03:36 PM



Hi Marty, actually my interest is more in the close-ups and not the full disk. That is why I thought the F15.5 might be better. My understanding is that scope has an identical quark unit but it is simply not removable. As I don't anticipate ever using it on another scope, I didn't think that was an issue.  The 60 mm aperture beats the Lunt's 50 and all for alot less cost. I figured the "double-stacking" claim was all marketing but I assumed that they were simply claiming that the results were good.   This is a tough decision...

If you're interested in high resolution (close ups) and not the full disc, you do not want to limit yourself to 60mm aperture. You certainly do not want a Quark fused to a 60mm little scope in this situation. And you don't want a Lunt 50mm or 60mm or any 60mm either, if you're mostly interested in close up high res. A standard Quark can be used with large aperture instruments, up to 150mm refractors, and that is where you can get into high res close up shots of the surface and features.

 

To give you an example, here's 40mm vs 150mm to give you an idea of why it's far more important to look at aperture if you're interested in close ups:

 

30861465137_9e2d8f783d_b.jpg

 

A standard Quark is good to go on apertures up to 150mm. So you can use a 60mm if you want, or an 80mm, 100mm, 127mm, etc to change scales and use your existing scopes.

 

Or, if you're buying a scope, big aperture achromats are inexpensive and excellent for this.

 

Very best,




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