Bad bad bad BF30

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fjabet
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Bad bad bad BF30

Post by fjabet » Wed Dec 07, 2016 2:01 pm

Hello all,

a customer of mine had issues with a SM90 with a BF30. he told me the images were pretty soft and his PST was delivering almost better images.
I was curious and offer him my help even if this kind of services is not what I usually propose. He sent me the whole shebang, includind the refractor.
After an alignment of the TMB92 he is using, the Solarmax was declared as clean. With my BF15, the images were just nice, as expected from a SM90.
Before alignment the image was rather inhomogeneous due to the quite severe tilt of the lens cell the SM90 was fitted to, after it is quite nice, almost as good as a type 1 SM.
So a bad BF30. This BF has the peculiar design of the lastest units made by Meade prior the take over.

Image

We have three filters : in the diagonal, a high pass filter :

Image


All spectra are done with Airylab's Ocean Optics HR4000 spectrometer.


The first filter in the 2" barrel (eyepice side) is the ITF. It is a bit oxydated.

Image

Its transmission is very low in the Ha band, and its FWHM is quite narrow with 100nm.


Last but not least is the bandpass 6A Ha BF filtre.

Image


It is different form others in the sense that it let the blue/green through. Hence the second red filter in the diagonal.

But the real issue is here :


Image


The peak transmission is... 2,5% ?


Here is my BF15 in comparaison :


Image


So in conclusion, in this BF this is unfortunatly the most difficult part to replace that is faulty.


I hope that was interesting,


Frédéric.
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Re: Bad bad bad BF30

Post by marktownley » Wed Dec 07, 2016 3:53 pm

Things like this are always interesting Frederic!

Now, if there was only someone who sold these 6a Ha BF ;)
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Re: Bad bad bad BF30

Post by Bob Yoesle » Wed Dec 07, 2016 11:28 pm

Thanks Frederic. And again evidence why an RG630 or 610 is needed in the filter system (apparently in the diagonal in this implementation).

Since I own 3 BF30's, for me the question would be whether the order selection filter was wrong or defective to begin with, or somehow deteriorated to its current low transmission value.
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Re: Bad bad bad BF30

Post by Montana » Thu Dec 08, 2016 8:01 am

Well I would send this info back to the manufacturer and ask for a replacement of the faulty goods under warranty :) it is not fit for purpose.

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Re: Bad bad bad BF30

Post by mdwmark » Fri Dec 09, 2016 8:39 am

The realty for standard warranty's for bandpass filters from the manufacture (Andover,Barr, Omega) for standard bandpass filters is one year. The longer warranty is the risk of the company that is making the complete filter.
Hard coated is 5 years. The term hard coated is a broader term now days. This field has changed a lot in the last 5 years. So some system are better then others. The newest technology are very stable with increase costs compared to making an soft coated bandpass.
Now this doesn't mean that it will only last one year. It depends on the run,the design. I have found that two cavity tend to last in the 5-6 year range.( standard blocker). The other factor is the diameter of the filter. They normal fail from the edge inward. So the smaller the filter the shorter life it may have.
From Fiabet scan of the bandpass, It looks like a single cavity filter. Meade could have been making there own. It take less layers but the profile is not the best. Single cavity filters also are not all that stable. From the fifth scan it is either noise or they mismatch the layers to get that peak on the right.
I attached what an normal ITF should look like. And what an 1nm, 2 cavity(standard) and a 1nm, 3 cavity(hard coated ) looks like. The " T" on this ITF is a little low. They are normally 55-60%. But the profile does not need to look this good to still work well.
https://solarchatforum.chttps://solarch ... w&id=25426
Attachments
3 cavity &2 cavity.JPG
3 cavity &2 cavity.JPG (98.42 KiB) Viewed 1820 times
ITF 1.jpg
ITF 1.jpg (33.32 KiB) Viewed 1820 times

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Re: Bad bad bad BF30

Post by christian viladrich » Sat Dec 10, 2016 2:08 pm

Very interesting information. Thanks for sharing.
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Re: Bad bad bad BF30

Post by Merlin66 » Thu Mar 02, 2017 5:15 am

Frederic,
I'm looking at a BF30 and need confirmation of the optics...
Reading this report you say there are three elements
Front ITF filter
Red/IR pass filter, both of these mounted in the 2" section
and finally, in the 1.25" diagonal the 30mm blocking filter.
Please confirm.
(The one I'm looking at doesn't seem to have the Red/IR pass element, but does have what looks like a small (15mm) ITF at the nose of the diagonal (like the BF10 etc) - just doesn't feel right!!!
Ken
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Re: Bad bad bad BF30

Post by Merlin66 » Tue Mar 07, 2017 2:50 am

Guys, I need your help!!

One of the members has recently purchased a BF30 system from OPT....
The 2" section does contain the large ITF and the secondary IR pass filter but
the 1.25" diagonal, although fitted with a final 30mm blocking filter at the eyepiece end ALSO has the small (15mm??) ITF fitted to the nosepiece side.
This seems to be completely wrong! It will cause severe vignetting.....
The image from Frederic in this thread shows a 1.25" diagonal which has NO such ITF in the nosepiece????!!!!
What's going on?
Meade claim ""The diagonal is as you comment, we do not make a larger version or any with a larger filter.""
Please help us understand what is "correct" - and any ideas about replacing the diagonal if necessary.
Thanks,
Ken
BF30 parts_clean.jpg
BF30 parts_clean.jpg (73.41 KiB) Viewed 1552 times
BF30 diagonal_clean.jpg
BF30 diagonal_clean.jpg (76.72 KiB) Viewed 1552 times
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Re: Bad bad bad BF30

Post by fjabet » Tue Mar 07, 2017 6:06 pm

Hello Ken, I confirm that in my case, the diagonal only host a RG filter. The ITF and the BF are in the 2" straight component.
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Re: Bad bad bad BF30

Post by marktownley » Tue Mar 07, 2017 8:18 pm

Wow, Ken, something is not right there :/
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Re: Bad bad bad BF30

Post by Merlin66 » Tue Mar 07, 2017 10:26 pm

Thanks guys!
Got it!
The 2" section has the front ITF energy rejection filter, followed by a narrow band blocking filter (obviously >30mm diameter!)
The 1.25" diagonal contains an IR filter (approx 30mm diameter) to suppress the out of band transmission wavelengths inherent in the BF.

Makes sense.

That being the case, then the 1.25" diagonal the member has is incorrect! The small filter in the nosepiece should not be there........
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Re: Bad bad bad BF30

Post by Merlin66 » Wed Mar 08, 2017 11:05 pm

Further info:
A "local" Meade supplier has sent some images of their "stock" BF30 assembly - guess what?
There is no small filter etc. in the nosepiece of the diagonal!!!!!
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

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