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

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

Post by SMS »

Hi Dave,

All three of my Coronado blocking filters show deep red when you shine a flashlight through them.

Steve


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

Post by DavidG »

Hi Steve,
The edges of all your filters, were there is no coating are clear so that shows the coatings were applied to a clear substrate and not the RG630 glass. The red color could be from a number of sources. It could be a coating that was applied on purpose, it could be from the ITF coatings or it could be from the "rusting" of the original coatings and the ITF material turn red when it degrades. Having the coating put down on clear glass vs RG630 glass indicates to me that there will be difference in the percentage of how much the the filter transmitt. So I think it safe to say that there are differences between the ITF made to be used in a PST vs a Solar Max BF diagonals and that the Maiers filter is not a drop for replacement for the Solar Max units. We know that the optical configuration of the Solar Max system is different, in terms of were each type of filter is located in the optical path vs PST.
All I can say is that the Maiers filters I have tried have worked very well in my PST and I bet they will also work well in any other PST and that has rusted ITFs that were made using the red RG630 glass.

Happy New Years !
- Dave


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

Post by swisswalter »

Hi chaps

great new informations. Thank you very much for the insight


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

Post by marktownley »

I thought it was appropriate to include the plot of the transmission of a BF15 ITF from http://www.sonnen-filter.de/






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

Post by DavidG »

Hi Mark,
Thanks for posting the plots. What I find interesting is that these plots show that the total transmission at 656nm is 45% for a Coronado ITF, while the Maier filter is 70%. So in theory if all else was same the Maiers filter should provide a brighter image.

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

Post by marktownley »

Indeed. I shall definitely be giving mine a good try and comparison when it it arrives (and the sun is a bit higher in the sky!). However like Steve says, and just looking at the variance in the pictures just us 3 have posted in this thread I suspect there's a variety of ones out there in circulation...


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

Post by DSobserver »

so here is my contribution :

rusted ITF from BF15 VS ITF from PST Meade




What is interesting if you compare this BF15 ITF to the SMS's one is that mine is from Schott RG630 and edge are not black treated :



Last picture is I think mentioning a different batch production compare to the one from Mark



comparing both ITF, I've the feeling that the PST one is thinner and both side silver treated (the one from BF15 is only one side treated....strange)

At the end everything looks possible, but don't understand the main ITF differences between BF and PST...


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

Post by Merlin66 »

Mark,
I think those transmission curves are already in the Library, you may want to check and add the Maier curve as well.....


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

Post by marktownley »

Here are the Maier curves...






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

Post by marktownley »

What might be really good as 'additional' info to complement all this is if anyone could take some pictures like those above of the ITF from a Lunt blocking filter. I would do this but I don't have a Lunt blocker...


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

Post by swisswalter »

Hi Mark

I'll give it a go the next days and run a plot on it


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

Post by marktownley »

Good stuff! Thanks Walter! :)


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

Post by swisswalter »

Hi Chaps

missing the disc on the sky I went into my lab.


Here we go:

start disassembling (note the fine handy tool ;-) used)





blocking filter and ITF





ITF edge on





Diagonal mirror





the plots









The ITF seems to be a double coated clear glass, the blocking filter is a stack of two glasses one deep red (okulare side) and golden coated (objective side).

The mirror on the diagonal is very special, it seems to have the same coating as the objective side of the blocking filter


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

Post by marktownley »

Well that is an interesting plot Walter. I knew you would make good use of that lens spanner ;)

Lots more transmission with the Coronado blocker than the Lunt at 656nm, no wonder Lunt say you can use a Lunt blocker on a Coronado but can't use a Coronado blocker on a Lunt...


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

Post by marktownley »

That Lunt ITF looks suspiciously like Schott BG glass to me

http://www.schott.com/advanced_optics/e ... ng=english

I wonder which variety?


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

Post by swisswalter »

Hi Mark


thank you very much for the comments. The lens spanner is just a wonderful tool, I guess you should get one too next birth day ;-)

Difficult to say about the BG glass ware. They cut the plot at 300 nm, makes it difficult to choose the right variety if it is from them. I'm not yet convinced


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

Post by marktownley »

I'm sure i read somewhere Lunt are using the newer BG glass in their blockers http://www.schott.com/advanced_optics/e ... ng=english I will have to search around for it.

The mirror looks like it's coated in some way too....


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

Post by swisswalter »

Hi Mark

thanks for the plots. So the ITF seems not to be of the BG6 type. All surpressing transmission well before 300 nm.

Yes the mirror has a special coating. Should I scrape it off and run an FTIR on it ;-)


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

Post by marktownley »

So the ITF seems not to be of the BG6 type. All surpressing transmission well before 300 nm.

Yes, all the BGs seem to fall short of 300nm :unsure:


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

Post by swisswalter »

Hi Mark

Comes time, comes solution. We just have to watch out and be aware ;-)


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

Post by DSobserver »

I've 1 question : why this solution would be better than the one from Beloptik that is already existing?


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

Post by marktownley »

I've 1 question : why this solution would be better than the one from Beloptik that is already existing?

Which is the Beloptik solution?


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

Post by DSobserver »

UV/IR cut on KG3 + night time Ha filter!

Did I miss something????


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

Post by DavidG »

I've 1 question : why this solution would be better than the one from Beloptik that is already existing?
If you referring to a PST, those are not a direct drop in replacement for the original ITF and the cost is higher.

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

Post by Merlin66 »

Yes,
That was the original solution!
But as Dave says - not a 'drop in' replacement (at the eyepiece)and more $$$$


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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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