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On the face of it, it looks interesting, but only if you have an SCT, but don't have a refractor. Stopping down the SCT gives a very slow focal ratio, like F/30, so you wouldn't need the tele-centric in a standard Quark. Not however that if I use my C8 I would only be using a fairly small 63mm aperture or thereabouts. Slightly less than a third of the full aperture is available. As I have an 80mm, a regular quark gives me more. I would almost expect these combo quarks to be fairy cheap, so that with the required ERF they do not come up to the cost of an ST80 plus regular quark.

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Nothing really new here in principle, off axis Ha solar systems have bee around for some time. The difference here is the use of a redesigned Quark that eliminates the telecentric, as mentioned by Michael, as the stop down to f30 means it is unecessary. The Daystar intention is to open up the use of SCT's with their Quark device. This new Quark would not be suitable for short focus refractors which still need to operate around f30.  :smiley:

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On the face of it, it looks interesting, but only if you have an SCT, but don't have a refractor. Stopping down the SCT gives a very slow focal ratio, like F/30, so you wouldn't need the tele-centric in a standard Quark. Not however that if I use my C8 I would only be using a fairly small 63mm aperture or thereabouts. Slightly less than a third of the full aperture is available. As I have an 80mm, a regular quark gives me more. I would almost expect these combo quarks to be fairy cheap, so that with the required ERF they do not come up to the cost of an ST80 plus regular quark.

I agree Michael. This does seem to be a bit of a niche product. Perhaps better for larger SCTs where it possible to get a larger off axis ERF but I'm sure the refractor option would generally be easier, plus less weight to mount.

I was expecting one with a x2 or so Barlow to allow longer focal length refractors to be used. I imagine something like a TAL or Lyra Optics 102 f11 with a Quark would be very nice, plus affordable.

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At $400.00 for a 10"ERF I don't think I'll be bothering :)

Dave

I don't know the costs of the Airy Labs kit, but they use the SCT corrector plate for the ERF, which is then coated with the necessary coatings. This should reduce the cost compared to buying a separate ERF as a lot of the cost is in producing an optically flat piece of glass.

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I don't know the costs of the Airy Labs kit, but they use the SCT corrector plate for the ERF, which is then coated with the necessary coatings. This should reduce the cost compared to buying a separate ERF as a lot of the cost is in producing an optically flat piece of glass.

The $400.00 one only has an 80mm ERF.

Dave

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The moment you use a full aperture ERF you will need a tele-centric to get the focal ratio back to F/27 or slower. A 180mm D-ERF costs €1395, the Airy Lab HaT based on the C8 €4400. As I already have the C8, along with tele-centric lenses, I wonder if buying a full aperture ERF isn't the less costly option than going for an Airy Lab HaT.

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I hope the off axis front cover remains in place better than 8" & 6" Nexstar SE stock covers.... plenty smoke signals if not  :shocked: I once coughed whilst upstairs and the cover fell off the scope which was in the living room downstairs !!!!

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I did a PST mod on a C5 SCT with a full aperture ERF, for whatever reasons it didn't perform as well as a 5" refractor with the same setup. Some comments on Solarchat at the time suggested that the native F2 of the SCT primary caused field angle issues for the PST etalon. Might be worth revisiting if I ever get time.  :smiley:

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I did a PST mod on a C5 SCT with a full aperture ERF, for whatever reasons it didn't perform as well as a 5" refractor with the same setup. Some comments on Solarchat at the time suggested that the native F2 of the SCT primary caused field angle issues for the PST etalon. Might be worth revisiting if I ever get time.  :smiley:

The secondary acts essentially the same way as a 5x Barlow. If you use a 4" F/5 with 2x Barlow in the optical path, rather than a native 4" F/10, the angles of the rays are a lot steeper across the FOV, causing sweet-spotting issues. A 5x "Barlow" in the form of the secondary would be a lot worse. That's exactly why I would like to see a tele-centric in such a set-up, and preferably one computed for the SCT (this is where the HaT design might be better).

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