Sunday, April 22, 2007

A good home for PST BF5

I bought a PST just to dig out the PST etalon module, but then how should I use the rest of the system? Wouldn't it a big waste if I simply throw the rest away?

I've disassembled the PST BF5 which also forms the visual back of the PST, I've removed the blocking filter inside this visual back, it's basically two pieces of glasses cemented together:-

The red side is facing the eyepiece, feels like a H-alpha narrow band filter.

The gold side is facing the objective end, it has very high reflectivity.

Given it's very small size, I wonder where shall I put it? With a blink of mind, I think of my 7x25 monocular which was used as a white light scope to see if there's any sunspot before I setup a bigger scope for imaging, so I disassemble it as well:-

I've placed the PST-BF5 in the field stop of the eyepiece part, however, it couldn't cover it all since it's very small. Then I also picked the circular field stop inside the PST visual back to put it as the field stop again for this scope:-

So, finally, I've a 7x25 which has a PST-BF5 installed. If a SM40 is placed in front of it, it's basically a very small H-alpha telescope! I plan to use it for afocal imaging with my DC, since it's so small, even a tripod is not required and I can use it for snapshot type of H-alpha imaging.

I shall conduct some experiments to see if the PST etalon can be used as a front filter, if it can, it will be even more portable. At the same time, since the PST etalon has no central obstruction to block the already small 25mm aperture, it will actually be more suitable than the SM40.

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