D-ERF in converging beam?

Frankenscope? Let's see it!***be advised that NOTHING in this forum has been safety tested and you are reading and using these posts at your own peril. blah, blah, blah... dont mess around with your eyesight when it comes to solar astronomy. Use appropriate filtration at all times...
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Bob Yoesle
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Re: D-ERF in converging beam?

Post by Bob Yoesle »

Just as a FYI, Brian Stevens at Lunt did mention the issue of tube currents was one of the reasons their 30 cm scope uses a open truss design.

The other issue I want to highlight is that etalons are very sensitive to temperature changes. My Solar Scope DSF100 etalons suffered greatly from thermal instability - and they sat ahead of the objective in the 1 mW/mm^2 region of direct sunlight and had a RG630/dielectric ERF ahead of them. None of the materials an etalon is composed of have a zero CTE, and reducing thermal loading and cycling as much as possible should be of paramount importance for optimum performance. Therefore using good pre-filtering as I previously described would help ameliorate such thermal loading and cycling...


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Re: D-ERF in converging beam?

Post by Rusted »

Thank you Bob.

I have seen changes in my own 6" 'scopes during my [usually] long image capture sessions. I would put it down to seeing conditions as the day warmed up. Though that doesn't account for better seeing later in the day. When the thermal load on the landscape must surely be at its highest. With convection from the heated ground rising into a cooling atmosphere.

Solar Spectrum uses an onboard cooler/heater at a price rather beyond most amateur's pockets. Though a simple cooling fan could easily be applied to our "toasty" etalons.Your argument for better filtration might well be more effective. Since the PST etalon is fully enclosed by its glass lenses. An external airflow may go completely unnoticed. Will we all end up with skeleton tubes? With a battery of cooling fans blasting away at each of the components? ;)


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