PST CaK modification

[hunterknox]

Hi All,

Can anyone talk me throught the process of converting a CaK PST to a module for use with a larger scope? I've done a Ha mod before but CaK is all new to me. I've had a look at the existing threads and I get the general idea but I'm not confident I'd know what I'm doing yet.

If it makes a difference I'm proposing to use the same 102mm f11 scope I use for my Ha PST mod.

Cheers,

Tom

[Merlin66]

I'd love to help, but I haven't done a CaK mod - as yet!
There's no real restriction, I believe, with the scope.
The CaK "module" is a series of broadband/ narrowband filters to give the final result.
I'm sure others will chip in, but I'd think as a basic mod you could just replace the "gold" tube with your donor OTA???

[Bob Yoesle]

This post should get you going in the right direction:

http://solarchat.natca.net/index.php/en ... dification

Feel free to ask if there is additional information you need.

[marktownley]

Apollo has got this summed up with his pictorial - only thing to add is in the back (ep end) of the black filter assembly you either need to put the BF5 from the ep holder of the PST, an Omega CaK filter or a Baader K-Line to act as the blocker...

[hunterknox]

Thanks guys and a special thanks for the pics, Rusty.

How about the spacing behind the CaK module? Is it the same (200mm) as with the normal PST?

[marktownley]

As far as i've found spacing is unimportant...

[colinsk]

My understanding of the CaK PST is that the light is uncollimated. There are no lenses in the filter assembly and it is not an etalon at all. Treat it as you would any filter. Try to keep out the heat out to make it last longer.

[marktownley]

My understanding of the CaK PST is that the light is uncollimated. There are no lenses in the filter assembly and it is not an etalon at all. Treat it as you would any filter. Try to keep out the heat out to make it last longer.

Spot on with that Colin...

[hunterknox]

Excellent. That's given me some ideas...

Any sources for large, round wratten 80B filters?

[hunterknox]

Actually here's another thought - could the CaK module not sit on top of a Herschel prism, which would effectively be acting as an ERF?

[marktownley]

You're cutting the light (by 95%) at CaK wavelengths by doing this, by using a dedicated ERF you will let ~100% CaK light through but cut light at other wavelengths...

[hunterknox]

Aah, forgot about that. Doh! Thanks Mark!

[marktownley]

[quote]You're cutting the light (by 95%) at CaK wavelengths by doing this, by using a dedicated ERF you will let ~100% CaK light through but cut light at other wavelengths...

In fact, I've tried this out and yes, you can install the PST CaK frontfilter in top of a Herschel wedge. B) I assure you the picture is all the same as we love it in the PST CaK.

While you are cutting 95% of the incoming light is not the same as saying that the amount of CaK light is diminishing or decreasing.

You still have exactly the same ratio of CaK as with other elements in the solar spectrum in the final 5% available. You are only "cutting" the incoming light so to speak, with all the elements remaining.

It works for me and it will work for you too. You still need the Omega CaK or even better the Baader K line filter as a blocking filter, of course.

And I assume it will work in H-alpha too, but why would one put all necessary filters for H-alpha in a Herschel wedge anyway? And I don't think there's enough space for such a device.

How times change! I forgot about this thread...

Both myself and Walter are using CaK filters mounted on the end of a herschel wedge now, and have been doing so for sometime. It works very well and circumvents Lunts 4" aperture rule for CaK...

[solarchat]

The Lunt CaK module for the LS152 also uses s standard Herschel wedge with a CaK filter on the end of it.

[astroshot]

Mark & Walter,
Just so as I am clear, you have a Baader Herschel wedge and a CaK filter.
Du you use an ND filter also?>
I presume the CaK filter is on the camera side of the wedge.
What CaK filter are you using?
Thanks,
Michael.

[swisswalter]

Hi Michael

it all depends on what sort of close up I work. The PP works fine with 2x barlow, afterwords I need more light and go direct with a beloptik filter , k-line filter and the lunt end of the CaK wedge

[astroshot]

Back one step there Walter... ;-)

PP?? beloptik filter??
What are these?

To confirm, are you saying you use a beloptik filter + a Baader k-line + a lunt CaK wedge all together for the same image?

Thanks,

Michael.

[marktownley]

Hi Michael.

My setup as follows > Lunt wedge with NO nd filtration, then on the camera (barlow) nosepiece PST CaK front filter and a Baader K-line* used as a blocker. Results work very very well 8) http://brierleyhillsolar.blogspot.co.uk ... ium-k.html

*Actually it's half a baader K-line and an Edmunds Optics 387nm filter I use as the blocker, it has a higher transmission % than the K-line on its own...

Mark

[astroshot]

Mark,
Thanks for sharing that detail.
Yes, it does work very well !
I used to own the Baader K-line filter but sold it about a year or two ago.

[swisswalter]

Hi Michael

PP=Pentaprisma (herschel wedge like Instrument)
Beloptic UV/IR cut as an ERF (The Baader D-ERF is not trasmitting the CaK lines)
Baader K-Line followed by the Lunt Prismen from the CaK wedge (KLUNT filter)


So I'm not using ther Lunt wedge, only the last part of it. Pics be found in the modsection ;-)