Maxvision 127ED

A friend reminded me of the above option, it's a 127mm f/7.5 ED triplet.

Aperture is 127mm and focal length is 952mm.

Dew shield retracted, it is ~840mm long and when extended, it's like 1020mm long, the weight is like 6.5kg, not very heavy considering that it's a triplet. The diameter of the dew shield is slightly more than 150mm, i.e. my Cheapy-ERF will still be large enough, finally at f/7.5, the PST etalon module should be happy with it.

Last but not least, it's pretty inexpensive, and in case there's not enough back focus, I can always ask my local friend to cut it... since it's cheap and so I won't hesitate to cut it. :-)

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Usage:

1. Solar imaging:-

- to be used with the Cheapy-ERF, PST etalon, BF10, this will ensure internal reflection free; since it's also less than 1000mm, the BF10 will still be big enough to cover the full solar disc, maybe good for DSLR at prime focus

- to be used with my Herschel Wedge, for excellent white light observation

- to be used with my Herschel Wedge + Baader CaK, for the best possible CaK

2. Deep sky scanning:-

- to be used with my Unistar Lighter at lower power, with my Pentax 40mm XL, it yields 2.73 degree which is very nice!

3. Planet imaging:-

I guess it's do-able with my LXD55

Storage:

With the very long tube, I guess I can only hide it behind the door, maybe to put the front inside a big plastic box with some dessicant inside