Thread: Which Filters
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Old 10-10-2011, 08:22 AM
avandonk's Avatar

avandonk is offline
Join Date: Aug 2005
Location: Melbourne
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Originally Posted by jase View Post
Good stuff Bert. I think you'll find you'll be doing narrowband imaging much sooner than expected. I had the pleasure of remotely operating a 16" ASA working at F/3.6. The scope sucked in photons like there was no tomorrow, alas it was located under moderately light polluted skies of Houston, Texas. Combination of sky glow and the speed of the scope made it extremely complex to do any RGB work. Narrowband made it bearable though major gradients continued to exist and made for considerable processing effort. The scope is currently being moved to rural skies so I'm hoping the set up will deliver considerably improved results. Whatever you can do to control local lighting will be to your advantage. Not much you can do about the greater sky glow, other than take your set up to darker skies. If you have the opportunity to do so, I'm certain the data from this set up will be nothing short of remarkable.
The whole new system is a bit of a leap into the dark Jase. The only real unknown is the F3 optic. The PL 18603 will really show any failings in the optical train. I am sure I can tame it by using a well designed dew extension shield to fit the existing one. A laser cut aperture to trim any edge effects may also be needed. This will give a slight loss in speed.
This will have the effect of limiting light not contributing to the image even entering the optic and having it being scattered to add to 'sky glow' and 'background'.

The PLC PWM temperature controller I currently use for my Peltier fridge would make a very good thermostatically controlled heater controller to keep the whole optical system at a constant temperature +/- 0.1C. As the system is sealed convective air currents would not be a problem at equilibrium.
The dew shield will be held at a few degrees above ambient to minimise convective currents as is current best practice. Lack of seeing at a FL of 600mm with 3" per pixel should not really be a problem.

I am still trying to think what else I have not thought of.

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