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Transit of Mercury in the Spicule Layer. Phil took this great image with his Quantum 6 Scope, Solar Spectrum etalon and PGR Camera.

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How do I know my Stage 2 is 200mm?

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Starry Jack
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How do I know my Stage 2 is 200mm?

Post by Starry Jack » Thu Jun 06, 2019 12:17 am

Asides from measuring, how do I know my Stage 2 PST mid is correctly spaced behind the etalon? To experiment I have an extendable tupeas the spacer between the etalon and the BF centered around the 200mm distance. I can shrink the tube and reach focus and I can extend the tube and reach focus, but I don’t see any difference in contrast.

Is focus the correct metric to use? Or contrast? Or???

There are too many clouds to do a really good test but still...

Last thing, I am using the 5mm BF and eyepiece holder from the black box. I figured I could get the rig ready while I purchase the 15mm BF.

The scope is a 152mm achromat with 152mm external Aeries ERF.

Thanks,
Jack
Explore Scientific 152mm f6.5 achromat
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Starry Jack
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Re: How do I know my Stage 2 is 200mm?

Post by Starry Jack » Thu Jun 06, 2019 12:20 am

And I operate at f11 or f16ish with or without the Barlow. The scope is native f6.5 with a 1:7 glasspath.
Explore Scientific 152mm f6.5 achromat
Aeries D-ERF
Quark Chromosphere f27 native, (f14 when focal reduced)
Mallincam .5x focal reducer (large format)
ZWO174 (IMX249 chip 5um)
Huge Sense of Adventure Viewing Creation

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Re: How do I know my Stage 2 is 200mm?

Post by marktownley » Thu Jun 06, 2019 1:00 am

Easiest and most accurate way is just to measure.
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Starry Jack
Im an EXPERT!
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Re: How do I know my Stage 2 is 200mm?

Post by Starry Jack » Thu Jun 06, 2019 1:14 am

200mm from back of etalon to ...?

-The BF material?
Explore Scientific 152mm f6.5 achromat
Aeries D-ERF
Quark Chromosphere f27 native, (f14 when focal reduced)
Mallincam .5x focal reducer (large format)
ZWO174 (IMX249 chip 5um)
Huge Sense of Adventure Viewing Creation

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Re: How do I know my Stage 2 is 200mm?

Post by Merlin66 » Thu Jun 06, 2019 1:06 pm

The distance from the rear lens of the etalon assembly to the focus should be very close to the Majic 200mm.
It’s probably easier in some cases the find the prime focus position of the donor scope and then position the front element of the etalon assembly at -200mm by measurement.
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Starry Jack
Im an EXPERT!
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Re: How do I know my Stage 2 is 200mm?

Post by Starry Jack » Thu Jun 06, 2019 2:23 pm

Thanks gents. At this time I am exactly at 200mm from the rear of the etalon to the BF block. I can achieve focus with at least a modicum of contrast when there are lots of high thin clouds. I should have clear skies on Saturday and I can play to see if moving the BF in or out brings any better quality but it sounds like I may have the right distance.

Best,
Jack
Explore Scientific 152mm f6.5 achromat
Aeries D-ERF
Quark Chromosphere f27 native, (f14 when focal reduced)
Mallincam .5x focal reducer (large format)
ZWO174 (IMX249 chip 5um)
Huge Sense of Adventure Viewing Creation

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