Front end replacement ERF for new "blue" PST??

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Re: Front end replacement ERF for new "blue" PST??

Post by DSobserver »

higher cost , ok, (but cheaper than what meade offer :evil: )

What do you mean with "direct drop"?

What is sure is that for the moment only beloptik is giving transmission up to 2200nm.


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Re: Front end replacement ERF for new "blue" PST??

Post by Merlin66 »

The Beloptic/ Baader are 1.25" diam. filters.....
The Maier is 17.5mm or so - a direct 'drop in' replacement for the PST ITF.
(I think you mean the Beloptic gives blocking up to 2200nm)


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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley »

Slow to respond to this, but all has been covered. With the Maier you just take out the rusted filter and pop in the replacement on the PST. Night time Ha and Beloptik UV/IR costs more, but, would work just as well :)


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Re: Front end replacement ERF for new "blue" PST??

Post by Merlin66 »

Walter,
I think there's something wrong with your transmission data....
Looks like it needs calibration....
The ITF seems to be far too much "off band" - the transmission at Ha is about 5%...this, I would have thought, should be closer to the 90%
The final blocking filter blocks EXACTLY at 6563A - you seem to off wavelength??


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Re: Front end replacement ERF for new "blue" PST??

Post by swisswalter »

Hi Ken


thank you very much about your comment. I wondered about the results too. I'll have to check the gear and will report


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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley »

Interesting. The 656nm peak does seems to be over somewhere like 620nm (ish!) - maybe that would bring the ITF curve something more similar to the BG glass curves then?


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Re: Front end replacement ERF for new "blue" PST??

Post by swisswalter »

Hi Ken, Hi Mark

mea culpa, mea culpa, mea maxima culpa. What a poor quality assurance. I must have a word with my boss next week ;-)


here the results






Interesting is the UV leak of the 2" night time Ha CCD filter


That ITF could indeed be BG61


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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley »

Just a note to say the filter arrived yesterday, initial impressions are very pleasing. I will be doing a more detailed evaluation very shortly :)


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Re: Front end replacement ERF for new "blue" PST??

Post by swisswalter »

Hi Mark


great, now I know why the weather is as it is ;)


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Re: Front end replacement ERF for new "blue" PST??

Post by drewclan »

Just a quick note, as I didn't see this mentioned above. These Maier ITF replacements do not fit on the older style Coronado PST. It's simple to see if your scope is compatible. Just unscrew the eyepiece holder from the top of the scope and remove the retaining ring you'll find there. If you see a tiny, aprox 3mm, square blocking filter then you won't be able to use the Maier.

Bummer for me! But many thanks to Chris Maier and Dave Groski for coming up with this solution for everyone else.

Jay in CT


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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley »

Yeah, it's only a fix for the newer models unfortunately...


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Re: Front end replacement ERF for new "blue" PST??

Post by swisswalter »

Hi Jay

welcome to that wonderful site. Have sun, fun and mod the hell out of it


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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley »

Here's a plot from Chris of the replacement ITF...




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Re: Front end replacement ERF for new "blue" PST??

Post by Merlin66 »

Looks good to me!!


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Re: Front end replacement ERF for new "blue" PST??

Post by larryB »

Hello, and thanks for an awesome thread. I've spent hours looking for these answers!

I have a couple of questions. I'm not 100% on the terms, but the ITF is the filter just below the eyepiece housing and above the pentaprism?

I have the PST in the image below, I just want to make sure I am ordering the right replacement filter. Is there a way to tell between "older" and "newer" PST's? Mine had the front element replaced under warranty by a previous owner, but this internal filter is obviously in it's "rusty" phase.

I'm looking at purchasing the replacement drop in filter mentioned in the thread:
http://maierphotonics.com/656bandpassfilter.aspx

Thanks for all this valuable information!

Larry

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Re: Front end replacement ERF for new "blue" PST??

Post by Merlin66 »

Larry,
The filter you show was always added to the PST when the objective was changed from the "Gold" to the "Blue"
It's commonly called the "mini-erf" or ITF filter to distinguish it from the Blocking filter element - the small 'red" filter you see looking into the eyepiece holder.
The Maier filter is a direct change-over for the deteriorated filter you show.


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Re: Front end replacement ERF for new "blue" PST??

Post by swisswalter »

Hi Larry


welcome to that wonderful place, Have fun, sun and mod the hell out of it


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Re: Front end replacement ERF for new "blue" PST??

Post by larryB »

Thanks! Just ordered one. I'll report how it goes.


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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley »

Just put the Maier filter as a replacement for the rusted ITF in my BF15 - works a treat! faster exposure and the image is considerably more even. Interesting they're the same size for the PST, BF10 and BF15 - admittedly though with a RG substrate instead of the clear substrate of the BFs...


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Re: Front end replacement ERF for new "blue" PST??

Post by swisswalter »

Hi Mark

that are very good news, especially


Quote :

considerably more even

end Quote

:hamster:


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Re: Front end replacement ERF for new "blue" PST??

Post by Merlin66 »

That could be great news!
I didn't think the smaller diameter would fit the larger blocking filters....


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Re: Front end replacement ERF for new "blue" PST??

Post by Merlin66 »

Whooooooooo
Mark's correct. The Maier ITF juuuuuust fits the BF10/BF15.
Very handy to know.


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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley »

I bet it would fit the BF5 blocker too ;)

I suspect the 'same size' ITF is Coronados way of saving themselves money by having 'like' components, fortunately for us it saves us money too ;)


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Re: Front end replacement ERF for new "blue" PST??

Post by Sungazer »

Hi All, I have recently fitted a Maier ITF filter to my PST, the results are even better than when new 7 years ago. I have today finished my PST mod ,using a Meade 100mm F 7.8 tube assy with an 80mm aperture stop at the front, ahead of the lens, giving F10, and a 60mm coated ERF located 230mm down the tube. The PST slides up the 2" focuser tube ,having cut off 3" of the original tube. and can be slid out and the original lens screwed back on and then can be used away from home. All mounted on a GP driven mount. I also have aperture stops for 70mm , 90mm, and of course 100mm.Giving different focal lengths if needed. Saved me buying a new scope !!!, Used only for visual use .
I can totally recommend the Maier filter, after 20 years of Ha viewing it is the best I have used.


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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley »

The Maier filter rocks! :seesaw


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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley »

Interestingly I tried this (in my bf15) with a unmodified SM90ii etalon yesterday, and with the CCD there is quite clearly a huge light leak going on somewhere, the ccd sensor was completely saturated. Putting a 7nm Baader ha filter in the optical train stopped this.

I also found that the front surface of the mirrored (objective side of the filter) had developed a frosted surface to it. I've tried to get some pics of this but is difficult to see in the camera...
P1080245.JPG
P1080246.JPG
P1080247.JPG
P1080248.JPG
This is very clearly on the top surface and is soft and can be 'scratched off'. I'm going to try and remove it chemically. Interestingly i've seen on the CN forum several times now, people reporting exactly this same thing on Lunt CaK and Ha blockers on the ITF.

Anybody else got / seen this?


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Re: Front end replacement ERF for new "blue" PST??

Post by swisswalter »

Hi Mark

that does not look good at all with that ITF filter. I would not chemically clean it, instead take a Diamond based grinding paste with a grain of 125 nm diameter Free samples on request ;)


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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley »

It is water soluble, as is the coating on the other side of the filter... :?


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Re: Front end replacement ERF for new "blue" PST??

Post by swisswalter »

marktownley wrote:It is water soluble, as is the coating on the other side of the filter... :?
Mark do I understand that right? The stuff which migrates to the surace is water soluble.


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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley »

It 'washes' off with a cotton bud dipped in water, as does whatever is coating the rear side of the filter... Very unusual...


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Re: Front end replacement ERF for new "blue" PST??

Post by swisswalter »

Hi Mark

next time when cleaning the ITF please send me the Cotton bud, I'll analyse the substance which migrates to the surface


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Re: Front end replacement ERF for new "blue" PST??

Post by Merlin66 »

Mark,
Interesting....
I haven't seen similar "staining" on my Maier filter - not yet anyway.......


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Re: Front end replacement ERF for new "blue" PST??

Post by Merlin66 »

Mark,
Seems strange based on earlier reports and the transmission curves we've seen that your SM90/Maier results should be so dramatically different.
Have you tried a combo of the BelOptic UV-IR/Kg3 and the Maier???


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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley »

Hi Ken, I don't have the beloptik uv/ir kg3, but the baader 7nm Ha or D-ERF used in conjunction with the SM90 completely solved the problem... Weird...


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