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Just quarking about...


Ags
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I tried shooting images with my Solar Scout at 60 mm, 52 mm, 37 mm and 30 mm aperture, to see how the f-ratio affected contrast. See my results below.

20220428apertures.thumb.jpg.f5d16df5498825a230ddc1b70883bd1c.jpg

In my opinion, 30 wins in an overview but what about detail?

20220428apertureDetail.thumb.jpg.2eed159f94535a2a7d914088d020fa72.jpg

Here's a full disk at 30 mm:

20220428disk.thumb.jpg.0ca6cfec329db7213b867c31939ae3da.jpg

Here it is processed as an honest eyepiece view. Makes the faculae pop!

20220428diskred.thumb.jpg.19a489780e0bb4596e3da1627495e2cf.jpg

 

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By the way, each sequence was processed identically, but I did vary the exposure lengths with aperture:

60 mm - 2 ms

52 mm - 3 ms

37 mm - 5 ms

30 mm - 8 ms

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Not sure if that's a accurate test.. if the ideal  aperture was 30 mm then I'm sure that it would have been made at that size

Maybe at 8 m/s was best for the location conditions on that particular day...

True test woul be to test all apertures in all exposures ...

To me it seems like you brightened the exposure at the cost of reducing the aperture

Or maybe the magic f30 had the part to play

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Posted (edited)
1 hour ago, newbie alert said:

Not sure if that's a accurate test.. if the ideal  aperture was 30 mm then I'm sure that it would have been made at that size

Maybe at 8 m/s was best for the location conditions on that particular day..

Cynically, an achro 60 mm doublet is cheap, and a 60 mm solar scope will sell a bit better than a 30 mm one!

I can't see any circumstance where an 8 ms frame will be better than a 2 ms frame. Given the difference in aperture, they captured the same amount of light and 2 ms will freeze the seeing much better.

However I agree the comparison is a bit unfair. I processed the images identically to see the difference between the apertures - but if I was just shooting at 60 mm I  would process it differently not at all like a 30 mm sequence.

Also I was pressed for time and shot short sequences, and then used a high percentage (16%) of the frames. This doesn't favor resolution, where the 60 mm would shine. I'm also using a color camera, which loses a bit of resolution.

Edited by Ags
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57 minutes ago, Peter Drew said:

I think I would baulk at paying for a 60mm aperture solar telescope if its best performance was at 30mm aperture.    🤔

Especially at the old price I paid, it's not a bad deal, but you can't judge just by a couple of pictures. Visually, the full aperture really shows proms well with very fine detail. Proms don't need a very narrow bandpass, but they do need a lot of light.

Secondly, the wider aperture increases exit pupil size, allowing for higher magnifications at the expense of a subtle loss of contrast.

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  • 5 weeks later...

makes sense. effectively you're increasing the focal ratio and quarks do tend to perform better at those longer ratios.  very similar in performance to the atleast in my example. this lunt 35tha is 35mm aperture, 400mm focal length, f/11.45. i put the quark in there and fairly surprised with performance for a cheap small aperture. ofcourse the bigger aperture 127 f9.45 beats it, but i've also compared against 50mm and 80mm f/5 scopes and they don't come close, they need masking down aperture for quark to perform its best on band. 

image.thumb.jpeg.104728ad1e2d8ffc1e77ef73206435b4.jpeg

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I'm currently settled on 43 mm aperture (f22). That seems to be a fair compromise between f-ratio, resolution and light gathering (to keep noise down and keep subs short)...

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On 01/06/2022 at 07:55, Ags said:

I'm currently settled on 43 mm aperture (f22). That seems to be a fair compromise between f-ratio, resolution and light gathering (to keep noise down and keep subs short)...

You seem to be zoned in on f ratio, admittedly you can't make your 60mm any larger in aperture, or change the 4.2x barlow any smaller but can't see the point of making the aperture smaller to balance out the f ratio

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Based on my tests it strongly affects contrast. So there is a balance between resolution and contrast, and that balance seems to be 43 mm 😀

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Posted (edited)
3 hours ago, Ags said:

Based on my tests it strongly affects contrast. So there is a balance between resolution and contrast, and that balance seems to be 43 mm 😀

Pretty sure Daystar would have run numerous tests before they released the 60 mm version , otherwise it would have been a 43mm instead of a 60..

F ratio will always be FL divided by aperture..  

Edited by newbie alert
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Posted (edited)
1 hour ago, newbie alert said:

Pretty sure Daystar would have run numerous tests before they released the 60 mm version , otherwise it would have been a 43mm instead of a 60..

F ratio will always be FL divided by aperture..  

it remains a mystery why Daystar didn’t issue the Solar Scout with a slower OTA - obviously they wanted to market it as a 60mm aperture, but why F/15, when the Quark is designed to operate best at F/30+? Ags is right to experiment with stopping down the aperture, and is getting some great results at different focal ratios. I’ve just been trying out a Baader Sundancer - similar to the Quark - and the difference in contrast on surface features between F/21 and F/30 is enormous. I suspect there are more than a few Solar Scout buyers out there who are disappointed with the visual performance at F/15, but who would see a lot more at F/25-F/30, even if aperture, and therefore resolution is lower.

Edited by Highburymark
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6 minutes ago, Ags said:

@Highburymark So how does the Sundancer compare to a Quark?

I will hold my tongue for now Ags as I’m meant to be doing a review for Astronomy Now, and I haven’t had chance to thoroughly test it. Had a couple of problems with the first unit so it’s gone back to Baader. 

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25 minutes ago, Highburymark said:

it remains a mystery why Daystar didn’t issue the Solar Scout with a slower OTA - obviously they wanted to market it as a 60mm aperture, but why F/15, when the Quark is designed to operate best at F/30+? Ags is right to experiment with stopping down the aperture, and is getting some great results at different focal ratios. I’ve just been trying out a Baader Sundancer - similar to the Quark - and the difference in contrast on surface features between F/21 and F/30 is enormous. I suspect there are more than a few Solar Scout buyers out there who are disappointed with the visual performance at F/15, but who would see a lot more at F/25-F/30, even if aperture, and therefore resolution is lower.

So why not stick a  x2Barlow in the mix and  run it at f30+...?

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18 minutes ago, newbie alert said:

So why not stick a  x2Barlow in the mix and  run it at f30+...?

There’s already a 4.3x telecentric in the device. But I agree it would have made more sense to use a more powerful telecentric - as long as overall magnification was kept to practical levels. I guess they didn’t do this because it would required a redesign of the Quark element and hiked the cost - it had to based around a Quark, presumably with etalons that didn’t make it to Quark grade - that original £695 price was very low for an Ha device after all.

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Posted (edited)

The SS60-DS is supposed to have the same quality as a proper quark, but less aperture - only 12 mm I think. 

Edit: the Scout has 16 mm eyepiece aperture compared to 21 mm for a proper Quark.

If a big quark can do full disk at 400 mm focal length, then logically the Scout could do a full disk at 304 mm or f5. That would have been a lot better than the f3.75 objective they chose. And it would only have added 8 cm to the scope length...

Edited by Ags
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12 hours ago, Highburymark said:

There’s already a 4.3x telecentric in the device. But I agree it would have made more sense to use a more powerful telecentric - as long as overall magnification was kept to practical levels. I guess they didn’t do this because it would required a redesign of the Quark element and hiked the cost - it had to based around a Quark, presumably with etalons that didn’t make it to Quark grade - that original £695 price was very low for an Ha device after all.

I think you have to factor in the price to the sales point that you're aiming for.. if you look at it that a 60mm scope has a focal length of 930mm and Barlow it once more say x2 to get your ideal f ratio then I don't think it can support it, not in the mainstream seeing conditions anyway ... Even at its current price it's still very low for a Ha scope , I think it's to make it affordable to most, especially if you compare it to a 60mm lunt

What's with the double stack at no extra costScreenshot_20220603-105717.thumb.png.f41655e28306633cb60ee2a92c9c1195.png blurb

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On 03/06/2022 at 11:58, newbie alert said:

What's with the double stack at no extra cost

The general consensus is its maketing hype.

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Filaments with a Quark or Solar Scout might resemble a double stack system if you get a great filter with a narrow bandwidth (luck of the draw), or if you are able to push the focal ratio of the system to F/40+. But true double stack filters suppress photospheric light bleeding through into the Chromosphere - such as on the limb , where they will show individual spicules, not the ‘double limb’ effect you get with a Quark or other mica filters. Daystar was definitely pushing it with the ‘double stack’ claim.

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