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ITF H-alpha filters

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32 replies to this topic

#1 DAVIDG

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Posted 21 December 2013 - 01:59 PM

Hi All,
For those looking for ITF filters Maier Phototonics is offering one. These are used for IR/UV blocking. http://maierphotonic...passfilter.aspx
I used the Maier filter to replace this one.

- Dave

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#2 BYoesle

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Posted 21 December 2013 - 02:17 PM

Excellent Dave! :waytogo: Thanks for posting this resource - looks like a perfect drop-in replacement for certain instruments with well-documented ITF failure issues.

#3 LarryAlvarez

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Posted 21 December 2013 - 03:12 PM

Wooohoo, finally a way to restore my system to 1000%. BTW, that's a really interesting design on the ITF you have there. Mine usually look more like the helix nebula. :)

#4 DSobserver

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Posted 21 December 2013 - 05:59 PM

be carefull! as far as I can see transmission over 1200nm is increasing!

#5 DAVIDG

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Posted 21 December 2013 - 06:13 PM

be carefull! as far as I can see transmission over 1200nm is increasing!

Maier's state "Thinfilm coated filter incorporates silver metal layers that reflect/absorb wavelengths from 700-3000 nm and greater and "Out of Band Blocking: Optical Density > OD 5 (O.D. 4.0 minimum 1200-1300 nm)" So from what they say only between the 1200-1300nm is the optical density less 100,000:1 (OD5) but better then 10,000:1 (OD4)

- Dave

#6 marktownley

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Posted 22 December 2013 - 04:31 AM

Wow, your ITF was properly trashed Dave!

Yup, like Dave says these filters block to 3000nm, a true ITF as is needed for a Ha system.

#7 germana1

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Posted 22 December 2013 - 10:32 AM

Dave where is this filter mounted? And can one use this in a PST and drill out the small one for better views,and one more ? Can that filter be put in a Coranado bf5 to make it larger?
Thanks pete

#8 marktownley

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Posted 22 December 2013 - 10:53 AM

Simple answer to both questions Pete - No!

This is an ITF filter, the blocking filter is something completely different and both of these filters must be used in conjunction with each other. You could replace a rusted ITF in a bf5 or bf10 with one of these.

#9 germana1

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Posted 22 December 2013 - 11:27 AM

Just curios where is the filter in the pic mounted, in the front of the BF or the eyepiece end? The reason for the ? Is my bf5 has a bit of a hallo in the center when you look at certain angle that's on the objective side, is the blocking filter actually 2filters in the same housing? Was hoping to make a little improvements to the system. Ps don't mean to hijack the thread.
Thanks again for the feedback.
Pete

#10 DAVIDG

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Posted 22 December 2013 - 11:32 AM

Dave where is this filter mounted? And can one use this in a PST and drill out the small one for better views,and one more ? Can that filter be put in a Coranado bf5 to make it larger?
Thanks pete


In a PST and many other H-alpha telescopes there two filters that used togther along with the Etalon. One of these is the ITF filter which blocks UV and IR. The ITF has a bandwidth that is fairly large of 50 to 100nm center around the H-alpha wavelength of 656nm but like I said it blocks the UV and IR that the Etalon transmits. To isolate just the H-alpha line a smaller diameter blocking or trimmer filter is used. This filter has a band width of only a few nanometers centered around H-alpha wavelengths and this just lets the sub angstrom H-alpha light from the Etalon thru but would let UV and IR thru if used by itself.
When you look into the eyepiece tube of a PST, the filter your looking at is this trimmer or blocking filter ie the BF5. The ITF is located below this filter at the very bottom of the eyepiece tube, just above the penta prism.
In my 'scope I noticed that the image was getting slowly dimmer, especially toward the edge of the field and from the picture of my ITF you can see why.

- Dave
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#11 BYoesle

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Posted 22 December 2013 - 02:05 PM

Just curios where is the filter in the pic mounted, in the front of the BF or the eyepiece end? The reason for the ? Is my bf5 has a bit of a hallo in the center when you look at certain angle that's on the objective side, is the blocking filter actually 2filters in the same housing?


The ITF can be placed anywhere ahead of the "trim" or "blocking" filter. In the PST it has also been placed as a coating on the objective. For both the earlier Lunt and the Coronado BF's, the ITF is found as the filter ahead of the trim filter in the BF diagonal, as shown here:

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  • 6266963-Lunt LS60T Ha SM.jpg


#12 germana1

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Posted 22 December 2013 - 02:37 PM

Thanks Bob that explains a lot thanks for the diagram. After the holidays I'll take a closer look at my diaganal and see what's going on as the views right now aren't to bad contrast wise. It's good to know there is a source for a replacement .
Pete

#13 DSobserver

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Posted 23 December 2013 - 04:42 PM

be carefull! as far as I can see transmission over 1200nm is increasing!

Maier's state "Thinfilm coated filter incorporates silver metal layers that reflect/absorb wavelengths from 700-3000 nm and greater and "Out of Band Blocking: Optical Density > OD 5 (O.D. 4.0 minimum 1200-1300 nm)" So from what they say only between the 1200-1300nm is the optical density less 100,000:1 (OD5) but better then 10,000:1 (OD4)

- Dave


mmmh . Only full spectrum graph would definitely convince me.... Why if it's the case they doesn't show it????? :question:

#14 marktownley

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Posted 24 December 2013 - 02:18 AM

I'm fairly certain Swisswalter will have a plot of this before too long...

#15 SteveSMS

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Posted 26 December 2013 - 07:40 PM

I received mine today and it looks great. I'm using it to replace an ITF from a BF5 diagonal. Thanks for letting us know about this Dave.

Clear Skies,

Steve

#16 swalker

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Posted 13 January 2014 - 03:55 PM

I bought this thinking my PST needed it, but when I opened it up, the ITF is just fine (which was surprising, I just had my PST serviced for the rusty objective in 2012).

#17 Photonics

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Posted 26 January 2014 - 04:38 PM

Here is a spectral graph of the blocking measured on a Varian CARY 5000.

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  • 6337058-ITF_blocking.jpg

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#18 Gray

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Posted 24 February 2014 - 11:26 PM

Received mine today. Fast shipping and a noticeable difference in clarity. My ITF was completely covered in rust. Easy installation, perfect fit. Can't wait to see what a difference it will make.

#19 Gray

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Posted 25 February 2014 - 02:32 PM

New ITF installed shows much brighter image. Image is 100 times sharper. Very satisfied customer. I'm happy with a lowly PST, IMO better than my Lunt 35 hands down...

#20 CarlDD

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Posted 25 May 2014 - 11:12 AM

Hi all.
I too am a very satisfied customer.
I've just installed it in a BF5 I purchased some time ago on amart and found the view to be very dim.
It's given a new lease of life to what would other wise have been a paperweight.
Best Regards
Carl

#21 Alfred Tan

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Posted 26 May 2014 - 06:26 AM

Hi Dave,

Definitely a good buy for $75. Now I have a solution when my ITF in BF is down. Thanks.

Alfred

#22 ASTROTRUCK

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Posted 14 April 2015 - 07:24 PM

i have a coronado bf 15 starting  to go but still good - fainter than when purchased  but no exrernal marking yet,

 

when it is time how do i replace whatever in the bf15 for that item  by maier

 

http://maierphotonic...passfilter.aspx

 

doesnt look as if that fits into anything.

 

what do i unscrew & what do i remove to place that new item into the bf

 

also does the size vary - seems it is a pst bf 5 or 10 replacement only ??



#23 SunBlack

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Posted 08 April 2016 - 07:06 AM

Hi i up thus topic, my bf15 is rusted too. This Maier is directly adaptable? Or to be cutted? a replacement tutorial?

#24 SteveSMS

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Posted 08 April 2016 - 07:20 AM

I don't know the manufacturing year of my BF15 diagonal but I was able to use the Maier ITF as a direct drop in replacement for a rusted ITF.



#25 janewind

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Posted 28 May 2019 - 03:27 AM

When I used the Corona sm90 and qhy183m cameras to shoot the sun today, I was always overexposed and half normal. As shown below, changing the telescope pointing, the position of the overexposed part will change. I suspect that there is a problem with the back end of the mirror.

 

The brightness of the sun's surface is uneven when shooting, and everything is normal. It is suspected that some angles are leaking invisible light.

 

No details after the exposure has come down.




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