Would someone be kind enough to verify my figures in case i missed something please ;-)

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Ewan
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Would someone be kind enough to verify my figures in case i missed something please ;-)

Post by Ewan »

Hi members,

Bored & geeky info follows (you have been warned :lol: )

Not been in here for ages due to work, weather & alt of the sun so feel a little cheeky asking questions straight off the bat but here goes.

I solar image using an AA 80mm EDT & a Tecnosky 152mm F5.9, both using a Quark Chromosphere but I also have a C8 SCT.
I was curious as to how much 'extra' glass I would be gaining with the C8 V's the 152mm, bearing in mind the C8 has a front obstruction.
So I worked out some numbers & I am hoping they are correct or as near as.

152mm = 28.07" total area
C8 203mm = 49.98" total area
Central Obstruction = 7.73"
So 49.98" - 7.73" = 42.25" then 42.25"- 28.07"= 14.18" difference in surface area in favour of the C8 ?

This seems to be the equivalent of a 4.25" aperture scope that I would gain in using the C8

Is this correct ? Welcome your advice or critique on this.

I know the UK skies are not the best & I may well not get a lot of use from the C8 but it's something I am looking into.

Atb
Ewan


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marktownley
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Re: Would someone be kind enough to verify my figures in case i missed something please ;-)

Post by marktownley »

Your 152 is running the 135mm ERF?


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Re: Would someone be kind enough to verify my figures in case i missed something please ;-)

Post by Ewan »

Yes Mark


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Re: Would someone be kind enough to verify my figures in case i missed something please ;-)

Post by marktownley »

You need to measure the free aperture of the ERF (it will be less than 135mm as some of it is held in the cell wall) to get the right numbers.


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Re: Would someone be kind enough to verify my figures in case i missed something please ;-)

Post by Ewan »

marktownley wrote: Mon Jan 22, 2018 7:57 pm You need to measure the free aperture of the ERF (it will be less than 135mm as some of it is held in the cell wall) to get the right numbers.
As you said once before Mark it was indeed 125mm.
The main thing I was trying to find out was how much difference there is using a 152mm or the C8 @ 203mm, as the C8 has the central obstruction, I had to account for this as well as the CO 'stops' light entering the tube. Is my basic theory correct Mark ?

It was clear glass aperture I was looking at as well & not taking into account the size of the existing D-ERF.
Also is it possible to use a reducer with a C8 + Quark to get down to near F30 or will I be looking at buying the Combo instead ?

Cheers Mark


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Re: Would someone be kind enough to verify my figures in case i missed something please ;-)

Post by marktownley »

Yeah, the premise with the maths is essentially correct, but seeing as you're really running at 125mm aperture with the frac (i'm assuming you're always using the ERF with the quark) the gain with the C8 is greater than the numbers you came up with suggests. I've always found my quark works just fine with a range of f10 scopes that i've tried it on.


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Re: Would someone be kind enough to verify my figures in case i missed something please ;-)

Post by Ewan »

Yes as soon as you mentioned the D-ERF size I realised the difference would be even greater :D
So you have no problems using a native Quark giving F42 or there abouts then ? good news for me then.

I have an idea on full ERF design but need to find someone who could machine a cell for me.

Anyway this is all something I am looking at doing through the year not like tomorrow.
Thanks for the advice Mark & clarifying a few points.

Atb


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Re: Would someone be kind enough to verify my figures in case i missed something please ;-)

Post by marktownley »

What you thinking of for the big ERF?


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Re: Would someone be kind enough to verify my figures in case i missed something please ;-)

Post by Bruce Girrell »

I think you'll find a better image with the refractor, despite the theoretical improvement from additional aperture for the SCT (or is that not the question?)
Please let us know how it turns out


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Re: Would someone be kind enough to verify my figures in case i missed something please ;-)

Post by Ewan »

Bruce Girrell wrote: Mon Jan 22, 2018 11:31 pm I think you'll find a better image with the refractor, despite the theoretical improvement from additional aperture for the SCT (or is that not the question?)
Please let us know how it turns out
If you take a look at Christian Viladrich's SCT images Bruce I think you will be quite surprised as to the detail that can be achieved with such an instrument. My SCT is normally for planetary use but having then got into DSO imaging with my 80mm then solar imaging with the 152mm the SCT got 'forgotten about'. It may pan out well it may not but worth a punt I think albeit the UK skies are not the best a lot of the time.

Ewan


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Re: Would someone be kind enough to verify my figures in case i missed something please ;-)

Post by christian viladrich »

Hello,

If the question is whether there is a big difference in resolution in Ha (or visible light) between a 150 mm and a C8, the straight answer is : yes, there is :-) I no longer use my Taka TOA 150 mm for Ha. Even for visual observation, le C8 is doing better.

This beeing said...resolution is mostly limited by seeing. So, depending on the observing site, it could turn out that the C8 gives nothing more than the 150 mm refractor gives, except ... a more expensive ERF.

The following images are not taken with the same filter and on the same day, but give a first idea of the difference of resolution from 150 mm to 200mm:
TOA150 :
Image
C8 :
Image
The two following ones are taken on the same day, same filter and telecentric lens.
C8 :
Image
C11 (Hat11) :
Image


Christian Viladrich
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Re: Would someone be kind enough to verify my figures in case i missed something please ;-)

Post by Ewan »

That 2nd image is the one that really got me thinking that maybe I could use my C8, I understand mine is not the HD or indeed I will not be as low as 0.3A but even so I have to give this some serious thought.

As you know Christian, when we spoke before, the filter & cell won't be wasted either way ;)

Got a few years till solar max gets here by which time I hope to have some pretty neat gear, wife allowing of course :D


Bruce Girrell

Re: Would someone be kind enough to verify my figures in case i missed something please ;-)

Post by Bruce Girrell »

I stand corrected then
It seems I need a little more practice with my C8


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