Tried a new technique: Barlow to Quark to Focal Reducer to Camera

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Starry Jack
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Tried a new technique: Barlow to Quark to Focal Reducer to Camera

Post by Starry Jack »

Per Val's encouragement, I tried a new technique: 152mm masked to 110mm to a Barlow lens (no body) on the end of the Quark then a .5 Barlow (no body) stuck on the 174 camera. While I did not like the vignetting when zoomed out, I did like the contrast when I constrained the ROI.
13_07_57-4-2709 152mm to 110mm to barlo-quark-fr as3 to imppg to gimp bw.jpg
13_07_57-4-2709 152mm to 110mm to barlo-quark-fr as3 to imppg to gimp bw.jpg (676.72 KiB) Viewed 1427 times
13_07_29-4-2694 152mm to 110mm to barlow-quark-fr as3 to imppg to gimp bw.jpg
13_07_29-4-2694 152mm to 110mm to barlow-quark-fr as3 to imppg to gimp bw.jpg (606.65 KiB) Viewed 1427 times
These are two sets of 200 frame captures in to AS3 then IMPPG then GIMP

Best,
Jack


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Re: Tried a new technique: Barlow to Quark to Focal Reducer to Camera

Post by MapleRidge »

That combo turned out very well Jack...nicely done :bow

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Re: Tried a new technique: Barlow to Quark to Focal Reducer to Camera

Post by JochenM »

Interesting setup. Nice results.

What's the idea behind using a barlow on two different positions in the optical train? Or am I just misreading that (the second one being a reducer for example)?


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Re: Tried a new technique: Barlow to Quark to Focal Reducer to Camera

Post by marktownley »

Yup, that's definitely more contrast! Well done Jack.


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Re: Tried a new technique: Barlow to Quark to Focal Reducer to Camera

Post by Montana »

Yes, that is fantastic :hamster: :bow

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Re: Tried a new technique: Barlow to Quark to Focal Reducer to Camera

Post by Starry Jack »

Jochen,

Here are the explanations Mark and Val gave me regarding the imaging train to try.

Mark's encouragement to mask down the 152mm to a 110mm: viewtopic.php?f=4&t=27707
Stopping down the scope is far from giving up. Think about, if the seeing limit is only where say 100mm of aperture is capable of to diffraction limit, viewing it with a larger aperture achieves nothing, the image you are getting is governed by seeing. The larger aperture will still show the same resolution as the smaller aperture. However there is a benefit here of running smaller aperture, the quark is now presented with a much longer focal ratio, and longer focal ratio is a tighter bandpass, and this in turn is more image contrast. Then all of a sudden the detail in the image is easier to see, easier for the stacking software to handle and easier to post process with less influence of image noise.

I would make 2 masks, a 100mm and a 125mm, and try them both against full aperture, I think you'll be surprised!
Val's use of the Barlow on the Quark and the Focal Reducer on the Camera: viewtopic.php?f=4&t=27914
Jack,

Yes, these two are the essential parts of my imaging train. Additional barlow on the Quark's nose increases the F/D making the light cone less steep. This narrows the bandwidth of the etalon = higher contrast and more uniform illumination in the FOV. Then a focal reducer (I do use reducers from 0,8x to 0.5x) helps to optimize sampling on the camera chip (scale optimisation).
Of couse, it is possible to not use a barlow lens on the Quark nose and reducer on the camera But in this case Quark's etalon will work at wider light cone and it's working bandwidth will be wider and image contrast will be lower.
For prominences imaging I usually do not use a barlow on the Quark nose but do use a focal reducer.

Hope this helps.


Valery


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Re: Tried a new technique: Barlow to Quark to Focal Reducer to Camera

Post by DavidP »

Probably a basic question, but can someone explain why the longer focal length , and more gentle light cone creates a more narrow bandwidth at the etalon?


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Re: Tried a new technique: Barlow to Quark to Focal Reducer to Camera

Post by Starry Jack »

That would not be me! ;)


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Re: Tried a new technique: Barlow to Quark to Focal Reducer to Camera

Post by marktownley »

DavidP wrote: Sat May 09, 2020 3:26 am Probably a basic question, but can someone explain why the longer focal length , and more gentle light cone creates a more narrow bandwidth at the etalon?
Have a read from page 17 onwards (diagram page 18) of the daystar white paper. http://www.daystarfilters.com/Quantum/QPEPaperPro.pdf


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Re: Tried a new technique: Barlow to Quark to Focal Reducer to Camera

Post by Radon86 »

Nice work, Jack ! Lovely detailed and high contrast images of the plasma ! :bow :hamster:

I wonder the following though:
1) what is the magnifying barlow (x2 or x3 or something else)
2) where is your UV/IR filter (heat); is it a front ERF or a 2 inch uv/ir cut filter somewhere in the imaging train
3) what is the stop aperture made of ? cardboard ? plastic. Does it matter because it may affect the optical quality of the telescope.
Has anyone managed a decent variable aperture stop, something like a camera lens; its difficult to make good aperture stops from cardboard or paper.

If I can switch to a straight through imaging train, and can convince myself to upgrade my setup (mount, camera, telescope, even h-alpha filter), I will probably buy a 100mm aperture telescope, maybe an ED scope because it has a better focuser already, and can be used for night time work as well !


Thanks.
Magnus


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Re: Tried a new technique: Barlow to Quark to Focal Reducer to Camera

Post by marios i. »

Nice result!


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Re: Tried a new technique: Barlow to Quark to Focal Reducer to Camera

Post by Starry Jack »

Magnus,
I also have an ED 80mm Orion and it produces very nice images as well. Perhaps I will do some more experimenting with that one though it is a fast focal ratio.

Regarding your questions:
I wonder the following though:
1) what is the magnifying barlow (x2 or x3 or something else)
2) where is your UV/IR filter (heat); is it a front ERF or a 2 inch uv/ir cut filter somewhere in the imaging train
3) what is the stop aperture made of ? cardboard ? plastic. Does it matter because it may affect the optical quality of the telescope.
Has anyone managed a decent variable aperture stop, something like a camera lens; its difficult to make good aperture stops from cardboard or paper.
The Barlow is a 2x though since I am not using it in it's normal body, it is likely a bit less? Same with the focal reducer which is normally a .5 (but again, is without it's body). I uses a full aperture Aeries DERF, but I also use a 12nm CCD filter on the camera to minimize any more potential glare and stray light. The aperture mask is thick paper mounted on a metal "lazy susan" hub I found which sits perfectly on the OTA, but it looks really ungainly. :).

Cheers,
Jack


Explore Scientific 152mm f6.5 achromat
Aeries D-ERF
Quark Chromosphere f27 native, (f14 when focal reduced)
Mallincam .5x focal reducer (large format)
12nm Filter
ZWO174 (IMX249 chip 5um)
Huge Sense of Adventure Viewing Creation
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Re: Tried a new technique: Barlow to Quark to Focal Reducer to Camera

Post by Dennis »

If i understand correctly one can use a non telecentric barlow in front of the quark telecentric to improve contrast of the etalon?
Im wondering if that is the case with all barlows / glaspath correctors or does the design of the "front barlow" matter too?

I experimented with this on my 150mm f/8 sw ac with a 1.6x glaspath corrector in front of the quark and the daystar reducer after the etalon.
So at the etalon i was aprox at f/55 and at the camera at around half of it (reduced). Still i didnt notice a "extreme" increase of contrast from f/34 to f/55. But i didnt document the comparison.


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Re: Tried a new technique: Barlow to Quark to Focal Reducer to Camera

Post by ffellah »

Nicely done Jack

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Re: Tried a new technique: Barlow to Quark to Focal Reducer to Camera

Post by MAURITS »

Well done Jack.


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Re: Tried a new technique: Barlow to Quark to Focal Reducer to Camera

Post by marktownley »

Dennis wrote: Wed Mar 30, 2022 10:32 am If i understand correctly one can use a non telecentric barlow in front of the quark telecentric to improve contrast of the etalon?
Im wondering if that is the case with all barlows / glaspath correctors or does the design of the "front barlow" matter too?

I experimented with this on my 150mm f/8 sw ac with a 1.6x glaspath corrector in front of the quark and the daystar reducer after the etalon.
So at the etalon i was aprox at f/55 and at the camera at around half of it (reduced). Still i didnt notice a "extreme" increase of contrast from f/34 to f/55. But i didnt document the comparison.
The actual f-ratios are best determined by image scale. A barlow, or a reducer only work at the advertised spec if they are used in certain conditions / spacings which the barlow manufacturer won't specify.

You're quark will work just fine at the native f8, ditch the glasspath in infront of the quark.


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