The CaK 80A filter arrives!

[Merlin66]

The ebay CaK filter arrived this morning...a few wraps of gaffa tape and it now sits nicely in a 1.25" filter cell.....
As soon as the weather improves......

[MjrTom]

I look forward to your first light report and subsequent images

[Merlin66]

I was going to set it up with the Herschel wedge....
Rusty: what do you mean "the red down to 20%"

[andreahaku]

Great news!
Waiting for your images then.
My 2 should be on their way... hopefully!

[Merlin66]

Ahhh OK
I won't use a blue ERF...I'll have it behind the Wedge.

Andrea...I thought the version I was buying could see through clouds, leap tall buildings and make coffee....apparently I was mis-informed!

[andreahaku]

I thought mine creates a small Sun inside the scope!
Isn't so?! I want my money back

[marktownley]

I was going to set it up with the Herschel wedge....

I tried with a wedge - too faint doesn't work. Ideally use a suitable 'blue' filter as a sub-erf.

[Merlin66]

Hmmm,
The quoted transmission is around 30%, the camera sensitivity down in the UV is about the same and the surface reflection from the wedge is about 4%....
I'd just dump the ND3 and leave it out or replace with the ND1.8.....

[swisswalter]

Hi Ken

great, I'm looking also forward to seeing your report on the first light

[marktownley]

Tried this with the Baader K-Line which has much higher transmission than the Omega filter and IMHO was still too faint... I'm currently shooting 1/2000sec exposure with minimum gain by using a blue ERF instead...

[Merlin66]

The eBay filter according to the curves has a bandwidth FWHM just less than 80 angstrom.
Mark: Point taken...let's see what happens....

[marktownley]

The eBay filter according to the curves has a bandwidth FWHM just less than 80 angstrom.
Mark: Point taken...let's see what happens....

THe Ebay filter is a veritable bargain (compared to the Baader KLine) and should give very comparable results I'm like you Ken, just waiting for the sun to return for long enough to play with all these mods - keeps me out of mischief! :whistle: :cheer:

[alex]

Mark do you have a link to that filter?

Thanks
Alex

[marktownley]

Mark do you have a link to that filter?

Thanks
Alex

[ebay]150751583708[/ebay]

[oldfield]

highly interested in this filter, waiting to see your results!

just surprised to learn that it's too dim even behind a herschel wedge.

BTW, will it take parallel rays in order to work well?

[colinsk]

So CaK is about 4.5 A wide. Beyond that you have blue filter for white light observing.

[etatsolarchat]

So did this filter work with the wedge?

Also seems they are sold out

[Merlin66]

I've been clouded out here in Belgium since it arrived. Maybe next month?

[andreahaku]

I tested them. I have two and I tested both single and double stacked and tilted. Results are good. Certainly not like having a "real" CaK filter but they work quite well. I also don't have the Baader K-Line so can't compare. But I think results are more or less the same by looking at the pictures I've found online made with it.

So for what they cost, they do a good job. As soon as I'll have some time, I'll get back to imaging and forum and I'll post some of the pictures taken with them.

Andrea

[etatsolarchat]

Hmm, is double better? If not maybe you want to sell me one B)

So you did this with a wedge and there is enough light?

[andreahaku]

I tried two to try to reduce the bendwidth. It's a little better.

You can find the spectrum of the filter (single) in my blog (http://observingthesun.com/2012/04/16/a ... spectrums/). I didn't had the time to do the double stack/tilted one.

In the blog you'll also find one of the fist picture I took a few weeks ago with a single stack.

I use an handmade Herschel Wedge (2") and it works well even in single stack.

I don't think I'll sell one... but I'm sure that Bob will bring more to eBay. Try emailing him

[etatsolarchat]

So where's a cheap source for filter holders 25mm filter in a 1.25in holder?

Also where did you get the 1200 l/mm grating on your DIY_USB_Spectroscope? I'm going to have to try that setup..

[Merlin66]

Surplus Shed sell the 1.25" filer holders...
A couple of wraps of gaffa tape on the edge and the 25.4mm (1") filters will fit!
I get all my gratings from Optometrics....

[andreahaku]

I got the filter holders from Bob on eBay along with the filters. Don't know if he still got some more. And the diffraction grating from eBay as well. It's not a great quality one and I payed a very few euros for it. But it works great for the use I do of it.
The USB Spectroscope is very cheap, easy to do and useful if you use astronomy filters like I do to improve the quality of your images.

[PEterW]

Always good to have a range of lower ND with a wedge in case you need to let more light in. Mark, 2000th second exposure?! What scope,filter and camera do you have, I though CaK was faint?

Cheers

PEterW

[sullij1]

Hey, WAAA you guy's buy em out before you posted? It aint right!

[etatsolarchat]

Actually thread started before they were gone... I've already asked them to relist so we'll see if he does...

[sullij1]

Actually thread started before they were gone... I've already asked them to relist so we'll see if he does...

Cool, thanks, don't know how I missed this thread. Been looking for a CaK that is affordable for months. Hope he puts more up. I emailed him too.

[sullij1]

He has more up Now! YAHHH! Snagged one!

[sullij1]

BTW; Everybody, thanks! :

[oldfield]

I got mine as well, I'm using it along with Baader 3.8, a side by side comparison with a 80A blue and an ebay CaK

Attached files

[Merlin66]

Oldfield,
Well done!
Excellent comparison which clearly shows the benefits of the Omega filter.
All we need now is a similar comparison with a single and double stack Omega....

[sullij1]

I picked up 2. Iwas going to give one to my son. I will stack them up when I get them and post the results. He has been engauged in his 20 other hobbies latley anaway.

[colinsk]

Remember we want off band transmissions on the order of .001%. These graphs are not very useful.

[sullij1]

Rusty,

Thanks for the 411 on how to get this done. Just picked up the 400bp10. :

You are a foutian of knowledge. Is the blue ERF needed with this setup?

[sullij1]

Is the 390 neccessary? How should the stack Look? Can the UV/Ir block be used instead of the 390? Just want to get it right. Sorry for all the questions. Example:

1. Solar film or BERF> UV/Ir cut> 400Bp> CaK> 390
2. Solar film or BERF> UV/Ir cut> 400Bp> CaK
3. Solar film or BERF> 400Bp> CaK> 390
4. Solar film or BERF> 400Bp> CaK>

[sullij1]

U R Da Man!Thank you for taking the time.

Cheers