Omega bob's CaK filter

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Re: Omega bob's CaK filter

Post by marktownley » Thu Jan 08, 2015 7:17 am

Very interesting set of images Walter. Sadly it has confirmed what I thought might be the case...

Did you overexpose any shots with Bobs filter to see if we have any ghosts with it.

Thank you for all your hard work with this.
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Re: Omega bob's CaK filter

Post by Brett » Thu Jan 08, 2015 9:08 am

Walter, thank you for this info, really appreciated and well done!

I have two questions if you do not mind:

1.) I could not figure out why you needed to tilt the Omega Bob filter?
2.) Question that I have been thinking for a while, now that you have the Omega filter. Do you think it can be successfully double stacked for imaging?

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Re: Omega bob's CaK filter

Post by marktownley » Thu Jan 08, 2015 11:05 am

Tilting is to throw the reflections.

I don't think I would buy one of them, let alone get 2 for double stacking. Double stacked that uneven illumination is just going to be worse...
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Re: Omega bob's CaK filter

Post by swisswalter » Thu Jan 08, 2015 12:25 pm

Hi Valery, Mark and Brett thank you very much

some of the questions are already answered by Mark.

I have informed Bob well ahead of publishing these pics. He is on the way to find out what exactly the issue is. I can only speculate, my Money is on an uneven sputtering of the layers (something like the Daystar Quark etalons suffered from for a short time).

Valery the Gamma used is usually 800-1000. I adjust the gamma on the monitor to give me the best looking life view. By most of the pics with the Bobfilter I had to use Gamma 512 , which is the lowest, to give at least some contrast.
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Re: Omega bob's CaK filter

Post by grimble_cornet » Thu Jan 08, 2015 12:44 pm

Wow - gamma 512 is VERY low ........... don't think I have ever captured at that setting :o

I find that I am often disappointed with the results when I use settings which make the image look good ON THE SCREEN with the GS3 so I have been running a few experiments to determine what works best with my scopes and my usual processing routine.
I usually frame and focus at G=800 where the image looks good on the screen and then capture at G=1000 (or 900-950 in poor seeing).
This seems to produce the best results with my 'off the shelf' Lunt CaK1200.
I'm not sure if you used a standard Lunt unit in your trial?
I compared a couple of my images taken on the 4th Jan with your set and mine seem to be quite similar to your 'standard filter stack' - whatever that is?

Thanks again for sharing your experience and expertise Walter - it is saving me vast amounts of money experimenting with filters in an attempt to improve my results :lol: :oops: :lol:
.

.



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Re: Omega bob's CaK filter

Post by Brett » Thu Jan 08, 2015 12:52 pm

Thanks for informing Bob. I wonder if he could get this sorted out if he would send us a replacement filter?

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Re: Omega bob's CaK filter

Post by Montana » Thu Jan 08, 2015 12:55 pm

Bob's filter with a K line looks alright for those on a tight budget (if they have the K line already). Certainly is seems that if you only have £200 I would buy a bob filter rather than a Baader K line on it's own as you will see more structure.

Alexandra

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Re: Omega bob's CaK filter

Post by swisswalter » Thu Jan 08, 2015 8:58 pm

Hi Mike, Brett and Alexandra

thank you very much

@Mike and Valery My Standard set up is the LUNT CaK wedge B1200, followed by a K-Line, a CaK-PST#1 and a TS UV/IR cut filter

After having done these experimental shots, I'll switch to the following combination as my new standard:

starting from the objective : UV/IR cut 2" Beloptik, one hot mirror of the LUNT CaK wege B1200, PST CaK #1, distance 50 mm, PST CaK #1, LUNT CaK stack, UV/IR cut 1,25" from Beloptik on the camera nose. So it is a tripple stack with almost no ghosting. You can use the same setup without the LUNT CaK stack with almost the same results
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Re: Omega bob's CaK filter

Post by swisswalter » Thu Jan 08, 2015 9:02 pm

marktownley wrote:Very interesting set of images Walter. Sadly it has confirmed what I thought might be the case...

Did you overexpose any shots with Bobs filter to see if we have any ghosts with it.

Thank you for all your hard work with this.
Hi Mark

yes I did, but did not record it, because there was only one small prom on the westside. the new setup showes hardly any ghosting, the Bob filter did not introduce more gosting. Of course I have to wait for a good limb with proms , then I can conform or not ;)
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Re: Omega bob's CaK filter

Post by swisswalter » Thu Jan 08, 2015 9:04 pm

Montana wrote:Bob's filter with a K line looks alright for those on a tight budget (if they have the K line already). Certainly is seems that if you only have £200 I would buy a bob filter rather than a Baader K line on it's own as you will see more structure.

Alexandra

Hi Alexandra

you are absolutely right, as soon as bob has sorted out the reason of the "banding" on his filter
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Re: Omega bob's CaK filter

Post by swisswalter » Thu Jan 08, 2015 9:05 pm

Brett wrote:Thanks for informing Bob. I wonder if he could get this sorted out if he would send us a replacement filter?
Hi Brett

I'm sure he will sort that out. Just leave him some time to do the job
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

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from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)

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Re: Omega bob's CaK filter

Post by swisswalter » Thu Jan 08, 2015 9:14 pm

grimble_cornet wrote:Wow - gamma 512 is VERY low ........... don't think I have ever captured at that setting :o

I find that I am often disappointed with the results when I use settings which make the image look good ON THE SCREEN with the GS3 so I have been running a few experiments to determine what works best with my scopes and my usual processing routine.
I usually frame and focus at G=800 where the image looks good on the screen and then capture at G=1000 (or 900-950 in poor seeing).
This seems to produce the best results with my 'off the shelf' Lunt CaK1200.
I'm not sure if you used a standard Lunt unit in your trial?
I compared a couple of my images taken on the 4th Jan with your set and mine seem to be quite similar to your 'standard filter stack' - whatever that is?

Thanks again for sharing your experience and expertise Walter - it is saving me vast amounts of money experimenting with filters in an attempt to improve my results :lol: :oops: :lol:
Hi Mike

the standard Lunt CaK B1200 wedge is a wonderful filter set. I thought, it is the best we can get, until Mark T. jumped into my garden, grabbed my scope, added a CaK PST #1 filter and dang ;-).
As soon as I get my promissed 14mm filter fittings I can report on double stacked LUNT CaK filterstacks. I guess my supplier fears the results and therefore is postponing the delivery date almost every month ;)
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)

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Re: Omega bob's CaK filter

Post by swisswalter » Thu Jan 08, 2015 9:24 pm

Valery wrote:Thank you very much, Walter for your titanic labor work. It is clear now what is what.

Only few questions remain:

1. What were the gamma setting for this experiment?

2. Does the Skybender consists it's own CaK filter?

3. What is your regular filter combo for CaK imaging?

4. Can you make one more experiment - Bob's filter alone with and without tilt and at maximum contrast gamma setting?



Valery.
Hi Valery


thank you very much

#1 was answered but I will publish the Gamma and exposure time for each avi that was stacked and published

#2 the Skybender 1,25" Version and the 2" Version come without any filters at all . You mount the filters you want to play with

#3 see my answer in that thread to Mike

#4 I did make the runs already (with and without tilt) , about the gammy, see my list which will be soon published
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Re: Omega bob's CaK filter

Post by swisswalter » Thu Jan 08, 2015 9:29 pm

Valery wrote:Another my thought - I still believe, that Omega Bob's filter can be used for large scale high resolution imaging
in the CaK instead of full disk imaging. For this it must be placed as the last element in the optical train, after a
barlow lens, near camera (as near as possible).

Valery.
Hi Valery

an interesting thought. But why should I get an filter with banding, which works only in a certain Situation/configuration if I can get a filter (CaK PST #1 or LUNT filterstack) which work almost perfect in any situation ?
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

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Re: Omega bob's CaK filter

Post by marktownley » Thu Jan 08, 2015 9:48 pm

swisswalter wrote:As soon as I get my promissed 14mm filter fittings I can report on double stacked LUNT CaK filterstacks. I guess my supplier fears the results and therefore is postponing the delivery date almost every month ;)
:oops: I've just designed it now on the computer, i'll laser cut it in the morning and post it saturday. Expect delivery in Wolfhalden early next week.
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Re: Omega bob's CaK filter

Post by marktownley » Thu Jan 08, 2015 9:52 pm

swisswalter wrote:But why should I get an filter with banding, which works only in a certain Situation/configuration if I can get a filter (CaK PST #1 or LUNT filterstack) which work almost perfect in any situation ?
Because the filters in the Lunt or the coronado are a completely different design than Bobs... Bobs are designed for energy rejection rather than to be used in a visual / imaging context.
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Re: Omega bob's CaK filter

Post by marktownley » Thu Jan 08, 2015 10:09 pm

swisswalter wrote:
Montana wrote:Bob's filter with a K line looks alright for those on a tight budget (if they have the K line already). Certainly is seems that if you only have £200 I would buy a bob filter rather than a Baader K line on it's own as you will see more structure.

Alexandra

Hi Alexandra

you are absolutely right, as soon as bob has sorted out the reason of the "banding" on his filter
Maybe i'm being too critical here, but i'm not sure I agree with this. I think there is not a huge difference between the detail with a K-line and the Bob, but the Baader will certainly give a much sharper and even image. Especially knowing you had gamma down in the 500s, says to me there's not much contrast there in the first place with the Bob...
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Re: Omega bob's CaK filter

Post by Valery » Fri Jan 09, 2015 2:53 am

swisswalter wrote:
Valery wrote:Another my thought - I still believe, that Omega Bob's filter can be used for large scale high resolution imaging
in the CaK instead of full disk imaging. For this it must be placed as the last element in the optical train, after a
barlow lens, near camera (as near as possible).

Valery.
Hi Valery

an interesting thought. But why should I get an filter with banding, which works only in a certain Situation/configuration if I can get a filter (CaK PST #1 or LUNT filterstack) which work almost perfect in any situation ?
Hi Walter,

You personally don't need to do so for YOUR imaging practice. I mean that it is worth to do as the test of capability of using Bob's
for CaK imaging. At least several peoples are waiting for your conclusion - is it worth to buy this Bob's filter for CaK imaging.

And my limited experience with CaK imaging tells me that the best what can be achieved with this filter is to image in high a resolution
mode when the filter is the rear element and as near to the camera as possible.

Thanks,

Valery.
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Re: Omega bob's CaK filter

Post by swisswalter » Fri Jan 09, 2015 5:17 am

Hi Mark, Hi Valery

thank you very much.

@Mark Ah, great to hear about the filter housing

@Valery I'm sure you have read inbetween the lines, on top of that, the pics speak a clear language
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Re: Omega bob's CaK filter

Post by Brett » Mon Jan 12, 2015 10:29 am

Walter, you stated that the performance of the Bob filter was not dependent on the f ratio. Did you verify this? What was the longest focal length that you attempted to use the filter on?

Reason for my question is that, maybe due the Bob filter having a different coating and design, that the focal ratio might play a bigger role than we are aware of. I would like to see how the banding issue is influenced when you take a test at about f/25 to f/30?

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Re: Omega bob's CaK filter

Post by swisswalter » Mon Jan 12, 2015 7:27 pm

Hi Brett

thank you very much. I used only f/6 f/7,3 and f/10. It does not make sense to me to use f/25 or f/30 for a full disk shot. I was expecting that the 2A filter is performing like or outperforming the CaK PST #1 or the LUNT CaK stack, neighter of that was true. On top of that, if the filter showes banding at f/6 through f/10 it will show it at f/40.
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Re: Omega bob's CaK filter

Post by Valery » Thu Jan 15, 2015 5:06 am

marktownley wrote:
Maybe i'm being too critical here, but i'm not sure I agree with this. I think there is not a huge difference between the detail with a K-line and the Bob, but the Baader will certainly give a much sharper and even image. Especially knowing you had gamma down in the 500s, says to me there's not much contrast there in the first place with the Bob...
Hi Mark,

I saw one of Walter's CaK photo taken through a 6" refractor and 5A DayStar filter. The details are great.
So, if Bob's CaK filters have <4A FWHM and the base of their transmission is like in DayStar filter, then these
filters can be used for CaK imaging. If they are not of very high optically, then they need to be used very near
the focal plane and better after a Barlow lens.

I bet, that Bob's Ca K Walter tested, can be used near focal plane in resulting F/20 or slower.

Valery.
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Re: Omega bob's CaK filter

Post by marktownley » Thu Jan 15, 2015 7:01 am

Valery wrote:Hi Mark,

I saw one of Walter's CaK photo taken through a 6" refractor and 5A DayStar filter. The details are great.
So, if Bob's CaK filters have <4A FWHM and the base of their transmission is like in DayStar filter, then these
filters can be used for CaK imaging. If they are not of very high optically, then they need to be used very near
the focal plane and better after a Barlow lens.

I bet, that Bob's Ca K Walter tested, can be used near focal plane in resulting F/20 or slower.

Valery.
Hi Valery,

Don't get me wrong, I want these filters to be a success but i've seen no images from them yet that would make me want to go out and buy one. Any results from yours yet?

Mark
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Re: Omega bob's CaK filter

Post by Valery » Thu Jan 15, 2015 11:34 am

marktownley wrote:
Valery wrote: Any results from yours yet?

Mark

Not yet. :)
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Re: Omega bob's CaK filter

Post by michael.h.f.wilkinson » Sat Jan 17, 2015 7:22 pm

Interesting thread, I was certainly contemplating Bob's CaK filter behind my Beloptic Triband ERF. Doesn't seem like a good idea. It is probably better to go towards a B1200 CaK (or even just a B600 in my 80mm F/6)
Solar kit: GP-C8 with Thousand Oaks Solar filter, APM 80mm F/6, Lunt Herschel Wedge, Solar Spectrum 0.3Å H-alpha filter, Beloptic Tri-Band ERF (80mm free aperture), Thousand Oaks 90mm ERF, Coronado SolarMax II 60mm with Double Stack Unit. Lunt straight B1800 Ca-K module.

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