Blocking Filter alternatives

Frankenscope? Let's see it!***be advised that NOTHING in this forum has been safety tested and you are reading and using these posts at your own peril. blah, blah, blah... dont mess around with your eyesight when it comes to solar astronomy. Use appropriate filtration at all times...
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Blocking Filter alternatives

Post by seti_v2 » Thu Mar 12, 2015 3:59 pm

Hi,

I know blocking filters need to be less than about 8angstroms in order to isolate a single etalon transmission spike.

Would either of these work? Anyone have experience with either of these?

http://www.ebay.com/itm/310955342486?ru ... 26_rdc%3D1

http://www.ebay.com/itm/150809916349?_t ... EBIDX%3AIT


I would be using this inplace of the 5mm blocking filter in a pst mod. Also I will be using an ITF and ERF for blocking as well.

thanks!
Frank

PST mod, Orion 120mm F5, Celestron C8

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Re: Blocking Filter alternatives

Post by marktownley » Thu Mar 12, 2015 4:04 pm

Personally I wouldn't waste money on those in the link.

Do you image or visual with the PST mod?
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Re: Blocking Filter alternatives

Post by seti_v2 » Thu Mar 12, 2015 4:21 pm

I'm wanting to image. I have a zwo asi120mm camera.

Not that I don't trust myself, but any solar scope that has been modified I'm not going to stick my eye behind it. Plus I enjoy imaging more than visual.
Frank

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Re: Blocking Filter alternatives

Post by marktownley » Thu Mar 12, 2015 4:34 pm

You can always mount the blocking filter closer to the camera chip to avoid vignetting...

Apart from that my best advice would be to look out for a bf10/15.
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Re: Blocking Filter alternatives

Post by swisswalter » Thu Mar 12, 2015 7:20 pm

Hi Stephen

I had them on my scope. I wasn't happy at all, sorry
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Re: Blocking Filter alternatives

Post by seti_v2 » Thu Mar 12, 2015 8:11 pm

What were you dissatisfied with? Blocked too much? Not enough? Bad image quality? Ghosting?

Thanks.
Frank

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Re: Blocking Filter alternatives

Post by swisswalter » Fri Mar 13, 2015 5:15 am

Hi Stephen

just not narrow enough to show good Ha details
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: Blocking Filter alternatives

Post by Valery » Fri Mar 13, 2015 11:13 am

swisswalter wrote:Hi Stephen

just not narrow enough to show good Ha details
Hi Walter,

I believe that Stephen asked how these filters do work as _blocking filters_ in junction with H-a etalons.

Have you tested these filters as blockers?


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"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

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Re: Blocking Filter alternatives

Post by seti_v2 » Fri Mar 13, 2015 3:03 pm

Correct. I'm asking about blocking filters in conjuction with ERF, etalon, ITF.

Oh and seti is just my online handle. Names Frank.

thanks everyone!
Frank

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Re: Blocking Filter alternatives

Post by marktownley » Fri Mar 13, 2015 3:21 pm

I've used one, not narrow enough, too much continuum leakage...
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Re: Blocking Filter alternatives

Post by seti_v2 » Fri Mar 13, 2015 3:49 pm

Which one of the linked ones did you use? Or do they both suffer too much continuum leakage?
Frank

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Re: Blocking Filter alternatives

Post by swisswalter » Fri Mar 13, 2015 5:59 pm

Hi Frank

the 0,7 nm Ha is for stars not for the sun, the 0,15 nm is for sun but in conjunction with a double pass system. I used an older pair, especially designed for Ha work on the sun in a telezentric system
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: Blocking Filter alternatives

Post by swisswalter » Fri Mar 13, 2015 6:22 pm

Hi Valery

here the blocking filter plots from LUNT B3400, B1200 and PST 5 mm


an overview
blockfilterlunt_pst_overview.jpg
blockfilterlunt_pst_overview.jpg (63.31 KiB) Viewed 2911 times


the Details

blockfilterluntpst_detail.jpg
blockfilterluntpst_detail.jpg (52.63 KiB) Viewed 2911 times

the transmission is relativ (different sizes), the PST seems to be a touch narrower and the filterstack is slightly thicker compared to the B1200. All three blocking filter seem to be having the same gold layer facing the incoming sunrayes
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: Blocking Filter alternatives

Post by marktownley » Sat Mar 14, 2015 12:48 am

Hi Frank.

I have the one in the second link, sorry, but they are junk. If they were any good the whole solar community would be using them, in reality I think you will struggle to find anyone that is getting good results from them. Sorry to sound harsh but this is the reality.

Mark
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Re: Blocking Filter alternatives

Post by seti_v2 » Sat Mar 14, 2015 1:05 am

Thanks for all the honest talk guys! I will wait and save up. Guess you get what you pay for.
Frank

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Re: Blocking Filter alternatives

Post by Valery » Sat Mar 14, 2015 5:41 pm

swisswalter wrote:Hi Frank

the 0,7 nm Ha is for stars not for the sun, the 0,15 nm is for sun but in conjunction with a double pass system. I used an older pair, especially designed for Ha work on the sun in a telezentric system
Thanks Walter for your measurements and your point of view.

However there is a misunderstanding, I believe.

0,7nm Bob's filter, if it really 0,7nm will be BETTER as a BLOCKING filter than any of these three filters.

Lunt 1200 has about 20A FWHM, both Lunt 3400 and PST have about 15A FWHM with very low finesse in PST
and much higher in the B3400.

So, it is necessary to test 7A Bob's filter as a blocking filter or as addition to a standard blocking filter.


Valery.
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

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Re: Blocking Filter alternatives

Post by fjabet » Mon Mar 16, 2015 10:01 pm

I have them all, the 0,7nm deep sky and the 1,5A stack. They don't work as BF as said before. You may guess proms with the 1,5A + elaton, but no more. Nevertheless when used on a tiltable mount with my Daystar, the complete 1,5A+ITF thick filter brings some added value.
It is also interesting visually when used with the PST etalon on the following system : HaT>BF15 band pass>telecentric amplifier>PST without its lenses>diagonal>1,5A filter>eyepiece or binocular.
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Re: Blocking Filter alternatives

Post by antonello » Tue Mar 24, 2015 1:00 pm

Hello All
I'm a new member. My English is not good, but I try the same to communicate. I have bought two 1,5A H-alpha Omega Optical filters

http://www.ebay.com/itm/310955342486?ru ... 26_rdc%3D1

and with these I saw for the first time and with much emotion the solar prominences with my small telescope of 70 mm lens diameter (with only $ 220 for filters!). After, I have bought a Lunt LS60FHa H-Alpha Filter (what you put in front for double stacking) for a telescope under construction with a Istar 150 mm H-Alpha f:10 lens.
Waiting to finish the construction of this telescope, I have tested the Lunt filter with my small telescope with lens diameter of 70 mm with Lunt filter in front to the lens. Together the Lunt filter I not did buy the BF, confident of being able to use one of the two Omega 1.5A optical filters as Bloking Filter.

The result it is was excellent. I see perfectly the solar prominences and the surface of the sun with a Omega Optical filter (BF 25mm!) paid only $ 110! NOT $ 1800!
I can not tell the difference between the use of my Omega Optical filter (such as BF) and a BF Lunt original (I not have the possibility to make the comparison), but what is important is that my filter works well and the difference with the original filter could be less than that of the price. ;)
Last edited by antonello on Thu Mar 26, 2015 6:45 am, edited 1 time in total.

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Re: Blocking Filter alternatives

Post by swisswalter » Thu Mar 26, 2015 4:48 am

Hi Antonello

welcome to that wonderful site. Have fun in the sun. Great description what you saw through your setup. Can you show us any pictures
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: Blocking Filter alternatives

Post by antonello » Thu Mar 26, 2015 7:19 am

Hello swisswalter

Please note that I have corrected my previous message to explain better what I meant.

Unfortunately I am not a skilled photographer and I have no experience in astronomical photography with small telescopes, but I made two photographs. The photographs were taken with a photographic camera Sony Nex. They are the firsts and unique that I've ever done on the Sun.
These pictures do not show everything that I see visually. With the eye to the telescope I see many details, myriad details, on the edge and on the surface of the Sun (consistent with the diameter of only 70 mm).

All this is NOT an invitation to buy this filter, but an invitation to those who have already this filter to try it as Bloking Filter (please, despite the Lunt LS60FHa has a ERF filter, I recommend to use also an IR-CUT filter with this Omega Optical filter).

In addition, if anyone has this filter and also a Lunt BF original, I and all we will be grateful to him for the comparison of the two filters.

Here are two images that I have made with my Omega Optical filter as Bloking Filter.
swisswalter wrote:Hi Antonello welcome to that wonderful site. Have fun in the sun. Great description what you saw through your setup. Can you show us any pictures
Attachments
_DSC5342.jpg
_DSC5337.jpg

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Re: Blocking Filter alternatives

Post by swisswalter » Fri Mar 27, 2015 5:01 am

Hi Antonello


thank you very much for the pics. Yes you have ha details, no doubt. It is difficult to judge from color camera pics how good the details are
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: Blocking Filter alternatives

Post by antonello » Fri Mar 27, 2015 8:17 am

You are right

my images may not accurately show the image quality obtained with 1.5A Omega Optical filter as BF.

I can write with certainty, that the quality of the image that i see with him is good, with many details, but is below the image quality offered by the objective in white light.
Even visually it is seen that the filter (the flatness of the sides of the glass window ) is not worked with Lambda / 4 precision . I think both Lambda / 1 ... (max).

This is also his limit.

However it is shown that this filter can function as BF.

When I wrote this thing in Italy, a person wrote to me that it is not possible because the filter costs too little. On a forum one other person, who has bought the same filter, and wrote the same things that I write, has had this response: "it is not possible, there are no individual filters with a bandwidth of 1.5A !, the minimun bandwidth is 50-80 nm " (!!!)

Certainly the Omega Optical Filter 1.5A not have the same quality of a bloking Filter Lunt, but it costs 1/20 and For Those Who Can not spend much (many people are not rich) the price is amazing.

swisswalter wrote:Hi Antonello
thank you very much for the pics. Yes you have ha details, no doubt. It is difficult to judge from color camera pics how good the details are

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