Omega bob's CaK filter

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Omega bob's CaK filter

Post by swisswalter »

Hi modder gang

Bobs CaK filter arrived just on x-mas, the clouds too. Hence I can show only some simple plots

Transmission overview
bobcaknewoverview.jpg
bobcaknewoverview.jpg (39.64 KiB) Viewed 4580 times
Transmission close up
bobcakcloseup_.jpg
bobcakcloseup_.jpg (52.43 KiB) Viewed 4580 times
Absorption overview
bobcaknewabsortion.jpg
bobcaknewabsortion.jpg (82.43 KiB) Viewed 4580 times

Interesting is the different behavier in transmission when measured through the silver side in comparison to the green-blue side. Visually I cant see the sun disk through the filter. The green-blue part of the filter looks some how like the baader venus filter


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Re: Omega bob's CaK filter

Post by Valery »

Merry Christmas to all!


Walter, thank you very much for sharing these results with us.

I see that this is very much different from what were told on the Bob's eBay page with this filter description.
On the eBay ads the transmission is higher than 60% ! Your filter has lower than 20%.

Blocking also is far from what were promised: "The filter comes as with high degree blocking elements that attenuate the longer wavelengths to an average of OD 8 and a minimum of OD 5.0. " While your results are close to OD 4 only.

For imaging this is OK, as the typical 10bits camera will not see the background. But the eyes have much wider dynamical range and therefore one can see the sun disk at longer wave lengths.

Will be interesting to see the image with DS and with a telescope 100mm and larger at high resolution. Too bad that large spots are over.


Valery.


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Re: Omega bob's CaK filter

Post by swisswalter »

Hi Valery

thank you very much, there will be new spots on the disk, I'm sure


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Re: Omega bob's CaK filter

Post by marktownley »

Interesting, thanks for this walter. We have ordered some clear skies for you and Barbara so you can test it out. I look forward to the results. I'm tempted by one of these, but i'll see what performance is like first...


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Re: Omega bob's CaK filter

Post by swisswalter »

Hi Mark

thank you very much for the ordered CS. Do you happen to know something about the delivery date ;)


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Re: Omega bob's CaK filter

Post by Ibbo »

swisswalter wrote:Hi Mark

thank you very much for the ordered CS. Do you happen to know something about the delivery date ;)


sometime between now and summer solstice :D :D :D


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Re: Omega bob's CaK filter

Post by swisswalter »

Hi Steve

that destroyes all our hope


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Re: Omega bob's CaK filter

Post by Ibbo »

I do hope a lot sooner as I am very interested in your results :bow

in fact I would have ordered a filter but for the polite demand by the Companies House for corporation tax :evil:


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Re: Omega bob's CaK filter

Post by swisswalter »

Ibbo wrote:I do hope a lot sooner as I am very interested in your results :bow

in fact I would have ordered a filter but for the polite demand by the Companies House for corporation tax :evil:

:lol: :lol: :lol: :lol: :lol:


Hi Steve

All over the world the same situation , isn't that funny ;)


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Re: Omega bob's CaK filter

Post by swisswalter »

Hi Freaks

Bob mentioned that my measurement my lack some measuring points. So I did a rerun from both sides blue / and silvered side with 0,5 nm resolution instead of 1 nm

the result
bobcaknew29122014_c-1.jpg
bobcaknew29122014_c-1.jpg (48.24 KiB) Viewed 4486 times


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Re: Omega bob's CaK filter

Post by Valery »

16% of transmission instead of promised 60%.


Valery.


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Re: Omega bob's CaK filter

Post by Merlin66 »

Walter,
Were your results corrected/ calibrated for the camera response at 400nm??
Just checking.


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Re: Omega bob's CaK filter

Post by swisswalter »

Hi Ken

thank you very much. No I made no corrections at all for the CCD response, but of course for the instrument.

@Valery it has almost 100% more light trough put compared to the KLUNT filter


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Re: Omega bob's CaK filter

Post by Merlin66 »

Another question....
I see it's quoted as a 1.25" filter.....does it come in the usual threaded filter cell?????


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Re: Omega bob's CaK filter

Post by Valery »

Merlin66 wrote:Another question....
I see it's quoted as a 1.25" filter.....does it come in the usual threaded filter cell?????
"All components are mounted in a standard 28mm or 1.25" Eyepiece ring." - as described on the site.


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Re: Omega bob's CaK filter

Post by swisswalter »

Hi Ken

in my case it came nacked as a Sandwich of a bluish and silvered part. It fits nicely in a narrow 1,25" threaded filter cell. It is too small in diameter to fit in a 1,25" threaded filter cell from TS


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Re: Omega bob's CaK filter

Post by Merlin66 »

Hmmm
OK, then you need a spare empty 1.25" filter cell to mount it.......


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Re: Omega bob's CaK filter

Post by swisswalter »

Hi Ken

yes exactly. Watch out for the free Diameter, the filterstack has a diameter of 24.9 mm and not 27,6 which is the usual european / Baader size


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Re: Omega bob's CaK filter

Post by swisswalter »

Hi Modder Freaks


here comes the load ;-)

you will see 23 different filter combos, taken on two days. Each combo was taken with the GH3, ~500 Frames, stacked 32 of them with autostakkert, threated only mild in PS to my taste.

on the first day I used only the WO110, stopped down to 90 mm (f/7.3)

because of the results I got

I used on the second day the WO 110 not stopped down and the 127/ f/10

to sum up

° you can take nice pics with the new bob filter
° the bob filter has a great transmission rate, easely to come down to 8 ms or less exposure time
° it works fine at f/6, f/7,3 and f/10


° if you want to have even fields, never introduce a LUNT CaK stack or PST CaK #1 filter in the optical Train
° the banding I observed with my filter was not dependend on the f/number nor the position of the filter

to better understand the coming pics: the following information

- first I shot with my standart filter stack as a reference
- then different combinations of filters to see if I could get better result's
- finally I introduced also a filter tilting device (the Skybender) to get rid of the banding (that is what I call it, Bobs filter behaves something like a PST Etalon , having a good side and a not so good side

o.k. lets get started

first go monday 5th january ,with the WO 110, stoppend down to 90mm giving something like f/7,3

My standard CaK filter set

CaK_05012015_105455_bw.jpg

only Bob filter

only_Bobfilter_110134_bw.jpg

bob filter with K-line as a prefilter

CaK_bobnew_05012015_110526_bw.jpg


bob with CaK PST #1 +K-line

Bob_CaK_PST#1_K-line_110736_bw.jpg

Bob-Luntstack-K-line
Bob_Luntstack_Kline_111108_bw.jpg

LUNTstack-CaKPST#1- Kline
Luntstak_CaK-Pst#1__K-line_111638_bw.jpg

PSTCAK#1-K-line- PSTCAK3#1
CaKPST#1_K-line_CaKPST#1_112615_bw.jpg

Lunt Stack-PST CaK#1-K-Line_PSt CaK#1

LUNTSTACK_CaK_PST#1_K-line_Cak_Pst#1_113309_bw.jpg

Bob-PSTCaK#1
Bob_PSTCaK#1_114601_bw.jpg


Bob_K-line_PSTCak#1
Bob_K-line_PST_CaK#1_114807_bw.jpg


Skybender Bob_PSTCaK#1
Bob_K-line_PST_CaK#1_114807_bw.jpg

Skybender- bob-K line_ CaK pst#1

Skybender_bob-K-line_PSTCAK#1_120211_bw.jpg

Skybender K-Line_Bob

Skybender _K-line_bob_120711_bw.jpg


WO110 no stop f/6
CaK_06012015_110702_bw.jpg

luntstack_CaKPST#1-k-line-CaKPST#1

Lunt_Stack_CaK-Pst#1_K-lline_CaK-PST#1_111037_bw.jpg
Attachments
Skybender_Bob_PstCaK#1_115704_bw.jpg
Last edited by swisswalter on Wed Jan 07, 2015 11:43 pm, edited 2 times in total.


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Re: Omega bob's CaK filter

Post by swisswalter »

I'm offline for a SMOKE ;)


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Re: Omega bob's CaK filter

Post by grimble_cornet »

A real labour of love Walter - thanks for sharing the results of your hard work :bow2


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Re: Omega bob's CaK filter

Post by swisswalter »

Thank you very much Mike

I have to open a new answer. I have been stopped by the amount of pics. So I'll restart after 115704


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Re: Omega bob's CaK filter

Post by swisswalter »

Here we go for the next part

skybender bob-k-line- CaKPST#1
Skybender_bob-K-line_PSTCAK#1_120211_bw.jpg

Skybender K-Line- Bob
Skybender _K-line_bob_120711_bw.jpg

WO110 full opening

PSTCak#1 K-line- Ca-PST#1

CaK_06012015_110702_bw.jpg


Luntsack-PSTCaK#1-K-Line_ PSTCaK#1
Lunt_Stack_CaK-Pst#1_K-lline_CaK-PST#1_111037_bw.jpg


Bob K-line _CaK-PST#1
Bob_K-line_CaK_pst#1_111822_bw.jpg

Bob filter tilted fix
Bobtfixtilted_112540_bw.jpg

inverse bob-tilted fix
bob_inverse_fixtilted_112942_bw.jpg

now 127 / f10
LUNT_stack_CAK_PST#1_-line_Cak_PST#1_113841_bw.jpg
CaK PST#1_Kline_Cak PST#1_114838_bw.jpg

bob-K-line_Cak PST #1_tilted_115451_bw.jpg


Bob_K-line_CaK PST #1_not tilted_115851_bw.jpg
Bob_Skybender_120530_bw_f10.jpg

bob_skybender_K-line_131057_bw_f10.jpg


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Re: Omega bob's CaK filter

Post by Valery »

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?



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Re: Omega bob's CaK filter

Post by Valery »

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.


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Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.
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Re: Omega bob's CaK filter

Post by marktownley »

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 »

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 »

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 »

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 »

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 »

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 »

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 »

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 »

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 »

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 »

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


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Re: Omega bob's CaK filter

Post by swisswalter »

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 ;)


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Re: Omega bob's CaK filter

Post by swisswalter »

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 »

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 ?


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Re: Omega bob's CaK filter

Post by marktownley »

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 »

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 »

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 »

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 »

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 »

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 »

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 »

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.

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Re: Omega bob's CaK filter

Post by marktownley »

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 »

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 »

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)


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