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

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

Post by Merlin66 » Fri Nov 29, 2013 9:36 pm

Guys,
It's been suggested to me that a PST with a dud ITF could be fitted with a front mounted 2" Baader 35nm Ha filter as a replacement ERF....
Any thoughts/ comments?? Optical quality?.....
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Re: Front end replacement ERF for new "blue" PST??

Post by DavidG » Sat Nov 30, 2013 7:11 pm


You might want to hold off buying one. I know for a fact that a company has developed a direct drop in replacement for the PST ITF and will soon be selling it. I have the prototype in my PST and it works great and took maybe 10 minutes to replace. My ITF only lasted about 3 years after it was installed in PST that was repaired by Meade for the rusted objective problem.

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

Post by swisswalter » Sat Nov 30, 2013 8:01 pm

Hi David

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

Post by Merlin66 » Sat Nov 30, 2013 9:22 pm

Dave,
That sounds VERY promising!
Do you know when it will be made available?
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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley » Sat Nov 30, 2013 9:49 pm

Sounds promising indeed dave!
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Re: Front end replacement ERF for new "blue" PST??

Post by DavidG » Sat Nov 30, 2013 10:22 pm



I'm hoping that filters will be availbale in the next few weeks. The company has made a couple of improvements that should greatly extend the life of the filters. They are using better coating material, the scribe is deeper along the edge and the edge is better sealed. I've worked with this company before in providing custom filters for my solar applications and have had excellent results. I told them that I believed that there would be market for a direct replacement filters for the PST and possibly other ITF used in other model solar telescopes. They sent me a prototype that has worked very well so they are going to make a production run and see how the sales go. As soon as I get the go ahead I'll let everyone know were to get them. By the way I have no connection with this company, just a happy customer that sugguested a possible product for them that would benefit PST owners.
Here is a picture of the prototype filter mounted in my PST focusing tube. I just unscrewed the retainer ring, dropped the rusted filter out, dropped the new one in and reinstalled the retainer ring. By the way you can help extend the life of any of these filters just by loosen the retainer ring so it just touches the glass. This allows the glass to expand during thermal cyclcing which causes less stress on the seal along the edge.

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

Post by Merlin66 » Sun Dec 01, 2013 12:35 am

Sounds absolutely great to me! (If the pricing was better than the Baader 35nm Ha - it would be a definate winner!!)
Any transmission specs available??
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Re: Front end replacement ERF for new "blue" PST??

Post by DavidG » Sun Dec 01, 2013 3:32 am

The spec I saw showed that the filter is block out to 2500nm and then same into the UV. The bandpass is centered at 656 and is about 75nm wide with 65% transmission at 656nm. It is also MgF2 anti-reflective coated on both sides to increase transmission and reduce ghosting.
The 50.4mm Baader filter with 7nm bandpass looks to start to transmitt around 1150nm which might be problem in letting IR thru and teh cost for the 2" one looks to be around 640 Euros which is around $870.
I don't know what the cost is going to be but I'm hoping that is will be far less then the Baader unit and the price of $150 to $350 Meade quoted me on sending my PST back to them to just have filter replaced plus a couple of months wait. As soon I know more I'll be posting here.

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

Post by Merlin66 » Sun Dec 01, 2013 4:00 am

Dave,
The Baader 35nm Ha filter blocks all the way into the IR but has some minor resonance leakeage. This is in the region well above the sensitivity of the CCD.
I just bought a 1.25" Baader 35nm filter for $80.
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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley » Sun Dec 01, 2013 8:14 am

Interesting. A filter with blocking all the way up into 2500nm is a plus. I'll definitely be buying one.
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Re: Front end replacement ERF for new "blue" PST??

Post by brianb11213 » Sun Dec 01, 2013 11:38 am

Sounds good ...
By the way you can help extend the life of any of these filters just by loosen the retainer ring so it just touches the glass. This allows the glass to expand during thermal cyclcing which causes less stress on the seal along the edge.
There are good reasons for never tightening retainer rings more than is necessary to prevent movement under gentle shaking. Compressing the edge of the glass distorts it optically & this can affect the optical performance. Refractor objectives are particularly sensitive to this effect; the mass market manufacturers usually overtighten the retaining rings (to prevent loosening during transit; people receiving "new" scopes with objective elements fallen out of the cell usually aren't too impressed) & this usually results in the scope having more contrasty images when slightly stopped down, the distortion caused by overtightening being restricted to the outer few mmm of the aperture.

For anything in a solar scope which is likely to warm up I'd respectfully suggest that allowing a slight rattle is probably better than just touching the glass. Use a dab of paint to prevent the retaining ring from unscrewing itself.

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

Post by swisswalter » Sun Dec 01, 2013 11:43 am

Hi Brian

a very useful information. Thank you
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

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

Post by DavidG » Mon Dec 09, 2013 11:09 pm

Hi All,
I got a message from the company that is making the replacement ITF filters, that they will be selling them for $75. Once they give me the go ahead I'll let everyone know were to get them. As I said before I have no connection with them except for being a happy customer.

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

Post by Merlin66 » Tue Dec 10, 2013 5:16 am

Whoooo........
That sounds like GREAT news - and a very good price!!
Will these be available for the various sizes in the common scopes?
PST- Lunt & Coronado blocking filters BF5 - BF30 etc.
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley » Tue Dec 10, 2013 6:45 am

Fantastic news! 8)
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Re: Front end replacement ERF for new "blue" PST??

Post by DavidG » Tue Dec 10, 2013 2:34 pm

Whoooo........
That sounds like GREAT news - and a very good price!!
Will these be available for the various sizes in the common scopes?
PST- Lunt & Coronado blocking filters BF5 - BF30 etc.

Right now, the diameter of the filter and transmission specs are for the ITF in a PST. If these sell well the company may offer other filters as well. It is my understanding that the Blocking Filters have a much different transmission curves then the ITF, those being much narrower bandpass.
I was sent two more "production" prototypes" to test. I'll report my finding when they arrive.

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

Post by swisswalter » Tue Dec 10, 2013 3:19 pm

Hi Dave

thanks for sorting that out for us
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: Front end replacement ERF for new "blue" PST??

Post by DavidG » Tue Dec 17, 2013 7:55 pm

Hi All,
I tested the latest production ITF replacement filter and it works very well. My PST is giving the best images that I can remember. The company that is making these filters is Maier Photonics. Here is a link to the filter http://maierphotonics.com/656bandpassfilter.aspx It is a drop in replacement and takes about 10 minutes to swap out the old filter with a new one.
I have no connection with this company except being a happy customer.

Happy Holidays and Solar Observing,

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

Post by Merlin66 » Tue Dec 17, 2013 8:08 pm

Dave,
Thanks for the link!
Great news to PST owners.....IF THEY LIVE IN THE US
They don't ship O'Seas.....bumma!
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley » Tue Dec 17, 2013 8:12 pm

That is a very formidable spec 8)

I shall be ordering one of those very soon...
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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley » Tue Dec 17, 2013 8:14 pm

The only thing I would like to see is the transmission graph above 1200nm...
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Re: Front end replacement ERF for new "blue" PST??

Post by marktownley » Tue Dec 17, 2013 8:15 pm

Dave,
Thanks for the link!
Great news to PST owners.....IF THEY LIVE IN THE US
They don't ship O'Seas.....bumma!

Nooooo!!! :ohmy: :unsure: :angry:
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Re: Front end replacement ERF for new "blue" PST??

Post by DavidG » Tue Dec 17, 2013 9:56 pm

[quote]Dave,
Thanks for the link!
Great news to PST owners.....IF THEY LIVE IN THE US
They don't ship O'Seas.....bumma!

Nooooo!!! :ohmy: :unsure: :angry:

Send a note to Maier Photonics and ask if will sell you one. They need to know were the market is.

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

Post by marktownley » Tue Dec 17, 2013 10:03 pm

Good plan. Will do.
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Re: Front end replacement ERF for new "blue" PST??

Post by DavidG » Tue Dec 17, 2013 10:06 pm

Here is Maier's shipping policy. Drop them a note to see if they will ship to your location.

Happy Holidays,
- Dave

"You can trust that your order will be quickly processed and safely delivered. We can ship products anywhere in the United States using the shipping method of your choice. When you place an order we will estimate delivery dates based upon the availability of your item(s), shipping method selected and your shipment?s destination. Our shipping charges are determined by the total dollar amount of your order, excluding applicable sales tax. Some products cannot be shipped to international destinations so please submit a message to us from the Contact Us page if you would like to discuss international ordering options. "
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