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CaK Full Disk - 15th October

markt

By markt
in Imaging - Solar

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markt

markt

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Didn't manage to image this until quite late in the afternoon, i'm surprised I got anything at all - the image on the lappy screen was shimmering all over the place, however avistack managed to work its magic and get something from not very much...

6246839729_f03713b042_b.jpg

cak full disk by Mark Townley, on Flickr

Taken with homebrew CaK filter, 70mm @ f11, DMK31.

Hope you like!

Mark smile.gif

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markt

markt

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The CaK PST has a 5mm blocking filter - I replace this with the Baader K-Line which effectively means the scope has a 30mm blocking filter. I also suspect the filter combo I have made has a slightly different bandpass that a Lunt CaK filter as in my eyes my full disks always look subtly different than the lunts. As others have notcied on here it is really easy to see the supergranulation...

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Tron

Tron

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The CaK PST has a 5mm blocking filter - I replace this with the Baader K-Line which effectively means the scope has a 30mm blocking filter. I also suspect the filter combo I have made has a slightly different bandpass that a Lunt CaK filter as in my eyes my full disks always look subtly different than the lunts. As others have notcied on here it is really easy to see the supergranulation...

Ahh I see, thanks.... I also read that the Baader k-line's are "stacked", do you know why that is?

So I could buy perhaps a smaller blocking filter on a solar diagional (Lunt or Coronado) (much much cheaper) and replace it with a Baader filter? So the "larger" solar (Ha or CaK) blocking filter is an overpriced upgrade that they try to sell for imaging that can be done cheaper?

The cost of the larger blocking filters push it out of the budget, but I could effectively void the warranty and DIY my own larger block on the same diagional? or are they sealed :)

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NickH

NickH

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Mark, yes I have built an adapter, but always wanted a wider FOV on it, I like your idea (and I have the two filters you mention already)...very interesting idea...have you got any pics of the construction and do you know the spacing you've set up for each part..

Nice one..!

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markt

markt

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When it says the Baader K-Lines are 'stacked' what it is referring to is that there are 2 peices of glass that make the filter. This works as an interference filter Interference filter - Wikipedia, the free encyclopedia

Not sure I would recommend cannibalising a Lunt CaK diagonal tbh... Not even sure what the configuaration of their filter is and so optically whether incorporating a K-Line into it would even work.

With all wavelengths solar, always go for as large a blocking filter as you can afford - scrimping on that will only cause regret later on...

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markt

markt

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Mark, yes I have built an adapter, but always wanted a wider FOV on it, I like your idea (and I have the two filters you mention already)...very interesting idea...have you got any pics of the construction and do you know the spacing you've set up for each part..

Nice one..!

Hi Nick,

Bit of CaK PST background (which you probably know anyway!) - the PST is made up of 2 main filter groups. The first sits in the end of the ota where it screws into the black box, the second is the blocker filter, actually a pair of filters, that sit in the bottom of the ep holder...

The procedure is pretty straight forward and is as follows:

I unscrewed the black box from the CAK PST, this left the 'front half filter' in the gold tube assembly. I used a hacksaw and cut off the OTA square a couple of inches above the front edge of this filter. At what used to be the objective end of the tube a 2" blue filter is fixed to act as an ERF, it will work without but the life of the filter assembly will be reduced through excessive thermal loading.

The back end of this hacked tube (where the black box would be) has an aperture a centimetre or so deep ever so slightly wider than a standard 31.7mm filter.

Next stage is to screw the baader k line into a C-Mount nosepeice, then using electrical tape, wrap around this assembly until just enough to make an interference fit that can go into the back of the above mentioned 'hacked tube' section. No special distances here, just pushed in as far as it will go... Rotating the Kline in this assembly reveals a point that gives best image contrast; once found this is clocked for future reference.

CCD cam is just screwed directly onto the back of the C-mount and you're ready to go. I'm able to image @ 70mm f12, no gain, exposure 1/1667s - nice and fast, freezes seeing :)

I've since retrofitted a 1.6x AE nosepeice between the CMount and the KLine to increase my image scale a bit - I prefer to mosaic rather than get a full frame shot.

Just to clarify a health warning here - this setup I only EVER use for imaging; NEVER for visual use. The UV wavelengths we're working with here are a recipe for cataracts (hence Lunt having a 100mm aperture rule).

The 'module' will then fit in any refractor with a 2" focuser.

HTH Nick.

Best wishes,

Mark :)

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NickH

NickH

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Sounds like the Cak module I built with the PST Cak (have demoed it at various star parties)...all I need to do then is take out the 5mm filter and slap in the baader on...I use a hot mirror to kill the thermal side, one that transmits at 393nm... will replace the 5mm filter tomorrow... nice one

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NickH

NickH

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Will post up some pics of my rig, I use a set of AE adapters (similar to the ones for the HA mod), and a 2" front filter (hot mirror), as said... my only issue ever was the "keyholing" due to the 5mm filter when using it with the 80mm Vixen, but this will be gone with the setup you mention...nice idea...!

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NickH

NickH

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velengths solar, always go for as large a blocking filter as you can afford - scrimping on that will only cause regret later on...

Kind of true, the Coronado BF10 seems in many instances to give a better image view than the 15...and that was also confirmed by people who work on them

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markt

markt

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Let me know how you get on Nick, will be interesting to see your results. What are you using for your hot mirror? My blue filter isn't the most effective blocker, lets through quite a chunk of light, if there's a better option i'm missing i'd be keen to give it a go; prolong the life of the filter downstream as much as possible.

:)

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