Ha & CaK Full Disks - 11th June

[markt]

Hi All,

Thought I would finally get round to joining SGL and get some of my solar pics on here. I'm normally lurking on CN solar, however as you know tis' forbidden to talk about the PST mod over there...

Here's some images from the brief few hour window this morning before the clouds and showers returned...

First off full disk in Ha - taken with a double stacked 40mm Coronado etalon mounted on a 70mm f6 refractor. 2x barlow and DMK31 camera. This is a mosaic of 6 frames assembled in Imerge...

Ha Full Disk Lrg by Mark Townley, on Flickr

Next off full disk in CaK. This is taken with my modded CaK PST (well it's innards') mounted to the 70mm frac @ f11. DMK31 and 6 panes assembled in IMerge. Seeing was starting to get ropey at this point and not all the frames are as sharp as I would like...

cak full disk lrg by Mark Townley, on Flickr

I had a go with the 127mm frac @ f19 with the Lunt wedge and 705nm TiO filter, however this was pushing things too far and the image was getting a bit mushy. This is AR11234...

wl f190007 11-06-11 11-17-18 by Mark Townley, on Flickr

I hope you like these! I'm looking forward to seeing more of other peoples solar images here and learning some new tips.

Cheers.

Mark

[Photosbykev]

lovely detail, I find the surface texture fascinating I'm curious why the PST mod should be a banned subject on CN ?? (I honestly have no idea, so if it's a touchy subject just ignore the question)

I'm seriously looking at a solar scope and obviously the PST mod is a contender except for the problems with DSLR imaging through it

[markt]

Hi Kev,

Thanks for your kind comments! No idea why discussing the PST mod is banned on CN, but it is, if I posted the above CaK image and said it was taken with a 'modded PST' i'd risk a ban; peculiar I know!

I personally think the way forward with solar imaging is through a CCD video camera rather than a DSLR, i've not really seen anything taken solar wise with a DSLR that comes close to CCD.

Mark

[Photosbykev]

Hi Kev,

Thanks for your kind comments! No idea why discussing the PST mod is banned on CN, but it is, if I posted the above CaK image and said it was taken with a 'modded PST' i'd risk a ban; peculiar I know!

I personally think the way forward with solar imaging is through a CCD video camera rather than a DSLR, i've not really seen anything taken solar wise with a DSLR that comes close to CCD.

Mark

Thanks for the comment on CCD vs DSLR. I come from a photographic background so I tend to think DSLR before anything else. I also like printing/framing images I take so I like high resolution images, so I might well go down the CCD with small chip and then mosaic them for a larger image.

[ollypenrice]

Great stuff. Could you point us to a tutorial on imerge mosaic making? I struggle on the sun using ICE or Ps because I get geometric distortions which mean the sun isn't round. (Well I know it isn't round but the edges won't join all the way round!)

Olly

[Merlin66]

Great images, great resolution, great scopes.

Well done!

[markt]

Thanks for the kind words guys!

Olly, regards IMerge I just used the instructions in the help file that came with it to learn my way around. Other things i've found that work, despite it not saying so in said help file is to use a fairly decent amount of overlap between frames (ie not a small thin band), manually alter the brightness between frames - although this is rarely an issue unless transparency is variable and I always run in FITS image format through Avistack2 (stacking), Registax (wavelets) and IMerge (mosaicing)... Oh, and make sure Avistack is stacking the minimum area else the edge of the individual frames are noisy...

If you're getting distortions is that a result of you using a barlow in the optical train? I used a 2x nosepeice on the above 2 mosaics and this introduces some noticeable distortion towards the periphery of the fov, doesn't help stitching together at all... Normally I use an AstroEngineering 1.6x nosepeice which i've found to be great and free from any spherical aberations. I ultimately need to bite the bullet and get me a meade 2x teleextender and / or a TV 2.5x powermate - I think these as peices of glass are the way to go...

[johnh]

Those are glorious images, love the CaK one.

John.

[Carbon60]

Great images Mark. Are you able to elaborate on the modified CaK PST? Thanks to Merlin66 et. al. we know about the H-alpha PST mod, but the calcium line scope modification is a new one on me. Given the beautiful image that you have posted here, there may be quite some interest in learning more about this.

Thanks.

Stu.

[Merlin66]

My guess is that the CaK filter and black box has been mounted behind a 70mm refractor - like the stage 1 mod......

[markt]

My guess is that the CaK filter and black box has been mounted behind a 70mm refractor - like the stage 1 mod......

Not quite... More like a stage 2 I guess...

The 'black box' was unscrewed off the tube which leaves the tube with the first half of the filter setup at it's rear end. The tube was then cut approx 3 inch from the back end - it's very nearly 2" in diameter and with a bit of electrical wrapped around this makes a great fit for a 2" focuser. Now, the second half of the filter is at the base of the eyepeice holder on the black box - it's a BF5, same size as with the regular Ha PST (though obviouslly different bandpass). I don't use this as a BF5 is like looking down a toilet roll tube, rather in the back end of the uncrewed and cut assembly I use a c-mount nosepeice with a Baader K-Line filter. The 1 1/4" peice of glass effectively means its operating as a BF30. A bit of electrical tape wrapped around this forms an interference fit so it fits snug and tight. My DMK31 screws onto the back of this...

I only ever use this setup for imaging, NOT visual.

Compared to the Lunt CaK filters (and i'm only comparing images of others here) the setup i'm using shows more detail and is more contrasty. This, I believe, is because the setup has a tighter bandpass <2.2a compared to the 2.4a of the Lunt. I'm able to run with exposure times of 1/2000 sec at zero gain, and by going for longer exposure are easily able to get proms in CaK light. The brightest of proms show up in the same way as the 'one shot' style of imaging with Ha.

That CaK disk isn't one of my best by far; there's plenty of better ones on my blog site Brierley Hill Solar or is you have a peruse at the full size images on my flickr Flickr: Mark Townley's Photostream If you go through it a bit there's close ups with the homebrew CaK and my 5" frac.

Mark

[sheri_barri]

Hi Mark,

Excellent images! I am interested in more detail on how you performed the mod of the CaK as I have one which could really benefit from being mounted on a 80mm refractor. If you have a how-to or could point me in the direction of a good one, I would appreciate it.

Keep up the great imaging!

Cheers,

Sheri

[twotter]

They're both great images

[markt]

Thanks!

Hi Sheri. It would be really easy to do a stage 1 mod on the CaK PST and use it with a frac of your choice. The stage 2 mod is much better IMHO as it removes the yucky astigmatic pentaprism from the optical train. Maybe call it the stage 3, but changing the original BF5 from the CaK PST for the Baader K Line filter is what brings on the real jump in performance - seems to tighten the bandwidth and increase the surface contrast compared to the original unit.

Mark