246 replies to this topic

[keithlt]

 

 

 

interesting test, I do wonder if the color template being displayed on an LED screen makes a difference compared to how the filters behave in natural light.

How could it? Light is light, regardless of its source.

 

well the badder ha filter just made a sea of red even including the white background

 

A computer screen has pixels in three colours, Red, Green and Blue - to produce Red, it lights up the red pixels, to produce white, it lights up Red, Green and Blue pixels - if a filter blocks all the green and blue light, "white" will look exactly the same as red, which is precisely what the Baader filter shows.

 

what is was getting at and now I look a bit foolish was is that in astro-imaging your target would not be producing full spectrum like a LED. well methinks that's the case

[Bart Declercq]

 

 

 

 

interesting test, I do wonder if the color template being displayed on an LED screen makes a difference compared to how the filters behave in natural light.

How could it? Light is light, regardless of its source.

 

well the badder ha filter just made a sea of red even including the white background

 

A computer screen has pixels in three colours, Red, Green and Blue - to produce Red, it lights up the red pixels, to produce white, it lights up Red, Green and Blue pixels - if a filter blocks all the green and blue light, "white" will look exactly the same as red, which is precisely what the Baader filter shows.

 

what is was getting at and now I look a bit foolish was is that in astro-imaging your target would not be producing full spectrum like a LED. well methinks that's the case

 

I'm not sure what your point is?

The whole point of "narrowband" filters is to only let through light at a particular wavelength, you don't want other light to interfere. In astro-imaging your subject may not be producing "full spectrum", but things like stars and streetlamps do produce full-spectrum, so if your narrowband filter lets other colours of light through, that's bad - testing this using a computer screen is perfectly OK.

[Fongky]

https://drive.google...iew?usp=sharing

We have a long Facebook chat with Optolong. The link is the record of our discussion today. There are seven persons in this chat group. The two representatives from Optolong can be identified by their Chinese names and the rest are Malaysians.

Koot and Jesster are my friends that have bought the Optolong filters that tested with off-band failure. William uses Optolong narrow band filters but his filters do not show any off-band failure. Derrick helped to establish the contact with Optolong.

Since the Malaysians were using English in this discussion, I only summarize the Chinese part of the online conversation:

1. The Ha and SII filters from Astronomik, Baader, and Lumicon are manufactured from HWB  glass, the same type of glass for making infrared filters. HWB glass has very good transmission rejection in wavelength below 600nm. Even without any coating, filter made by this type of glass will achieve the same results as my test. Optolon Ha and SII filters, such as William’s SII filter that did not show any blue or green leakage were produced with HWB glass.

2. Since August 2016, Optolong has switched to B270 glass with the new Optorun coating process. Bubbles and lines in the HWB glass are the reasons of switching to B270. Another reason is to comply with the environmental import policy of the European Union. In addition, Optolong has studied the materials and coating method from Astrodon and trying to meet their standard with the new manufacturing facility.

3. The new coating achieves blocking of 0.1% (OD3).  Astrodon filters have blocking of 0.01% (OD4) which is much more expensive. You can just add an IR filter to the Optolong  narrow band filter to achieve the same result as your test. However, it will have different result when imaging the night sky.

4. Optolong denied that the filters that have shown blue and green leakage are defective. They insist that their filters have passed their stringent quality control process before they are shipped to customers.

In the afternoon, Optolong presented a set of tests using different glasses (HWB and B270) to demonstrate their arguments.

They appreciate our feedback but think that my tests are not professionally done. They suggest we test the filters with spectrometer.

Well, I will leave it to everyone to form your opinions from this discussion. I will be grateful if you can share your two cents’ worth.

Thanks

Edited by Fongky, 19 December 2017 - 10:23 AM.

[jimthompson]

In my opinion it sounds like Optolong has changed their recipe in order to save money.  They don't want to use HWB630 glass as the base for their filters because of bubbles and lines...and yet Astronomik and Baader, etc. still use it for their filters.  Seems like Optolong just does not want to pay more money to get high quality HWB630 glass.  Also, settling for OD3 blocking is not great.  Most other narrow band filters aim for OD4 minimum and some times even OD5 blocking, ie. 0.01% to 0.001% transmission at off band wavelengths.

 

This is disappointing to me as I had high regard for Optolong filters up until now.  I extend my offer again:  anyone with Optolong narrowband filters that wants to have their spectrum measured, I am happy to do it. 

 

Best Regards,

 

Jim T.

[hfjacinto]

Fongky, thank you for doing this. I learned a lot.

[jimthompson]

Hi Fongky,

 

You can use a monochrome camera to do the same test.  Colours that are effectively blocked by the filter will appear dark grey to black, and those that pass through the filter will be light grey to white.

 

Best Regards,

 

Jim T.

[Konihlav]

many years ago I did a run of Astrodon filters (and some others as well) on spectrometer to see if I spent my $$$ in a useful way or not (some stuff is still on my blog). What I learned? Astrodon filters, narrow band, though very expensive are the best quality ever! (only come always dirty in the package which is what you'd not expect from a top-brand filters, I got many of them of various sizes and it was always this way).

 

I can tell you one thing - for narrow band, Astrodon's are best (second in my opinion Baader). For broad band - it depends (for some large format KAI KAF series 16803 of cameras on big CDKs or Newtonians Astrodon TruBalance are the way to go, BUT for all the rest LRGB from Baader are just as OK as it can be - because for refractors - that are never apochromatic - using a highly transmitting L or B filters from Astrodon produces larger stars - and the TruBalance 1:1:1 from Astrodon is hard to match with any other CCD or CMOS chip in the camera other than famous Kodak/TSI/OnSemi KA* series - MOREOVER Astrodon's LRGB are somehow optimized for light pollution supression and I nowadays (for deep LRGB shots under a good low LP skies) prefer higher transmittance of full color spectra rather than having subtle LP filter in place - I can always add an IDAS light pollution suppression P2 filter to the optical train if I need to).

 

last comment: price point!!!

 

- cheap filters won't be the best performing ones (may only get to some close to good ones with some compromise but attractive due to low price or difference between premium filters and cheap ones)

 

- expensive filters are not guaranteed to be best performing ones (maybe they are maybe they are not - but there is some chance that they would be)

 

it's up to everyone to decide which link of their imaging setup will be the weak one (compromise).

[Fongky]

_{I also am glad Optolong responded.  looking forward to seeing their response}

Optolong has indeed responded. You can read the translated summary here, https://www.cloudyni...lter/?p=8282858

[Fongky]

I have a set of 3nm astrodon filters that I can test, however the camera is going to be mono, so I'm not sure how do the test, 

You can still test them with monochrome camera. Since Ha and SII filter should cut off everything (appears as black) and only the red (appears as white or grey).

[Fongky]

Hi Fongky,

 

You can use a monochrome camera to do the same test.  Colours that are effectively blocked by the filter will appear dark grey to black, and those that pass through the filter will be light grey to white.

 

Best Regards,

 

Jim T.

I think Andysea can try that out. I have no way to mount my lenses to the monochrome camera. Well, I can mount it to the telescope but the color template will have to be placed a few hundred meters away

Edited by Fongky, 19 December 2017 - 10:53 AM.

[Fongky]

Also, settling for OD3 blocking is not great.  Most other narrow band filters aim for OD4 minimum and some times even OD5 blocking, ie. 0.01% to 0.001% transmission at off band wavelengths.

I seriously doubt that the B270 glass Ha and SII filters have OD3 off-band blocking. I may have a way to test them.

[StarMike8SE]

Now I am questioning my choice to buy my set of Optolong narrowband filters.  I had noticed that the contrast in my 7nm Ha filter was not as I expected, and this may be the cause

[Alien Observatory]

Fongky,  Thank You for this thread as it is very interesting and I am learning from it.   TY  again,  Pat Utah   

[Alien Observatory]

Now I am questioning my choice to buy my set of Optolong narrowband filters.  I had noticed that the contrast in my 7nm Ha filter was not as I expected, and this may be the cause

Mike, Same here for my ZWO Ha filter...  Pat Utah  

[Fongky]

Fongky,  Thank You for this thread as it is very interesting and I am learning from it.   TY  again,  Pat Utah   

No worries. This is the very reason we have this forum.

[andysea]

I will run the same test with the astrodon 3nm and my mono camera next week when I am back from Hawaii.

[jimthompson]

I measured the spectrum of my Optolong 7nm filter tonight.  The resulting plot is attached below.  It appears that my Optolong filter is performing somewhat as advertised but not quite.  The transmissivity reported by Optolong at 656.3nm (Halpha) is supposed to be better than 80%, but I measured only 57%.  Also the off wavelength blocking is supposed to be OD3 (0.1%) but I measure around OD2.7 (0.19%) in the visual band, and OD2.0 (0.93%) in the NIR band.  Note that my measurement of spectrum rolls up at the ends due to my using a halogen lamp as my reference (ie. measurement error becomes large <400nm and >1000nm).  This filter is probably still usable for its intended purpose, but it is not performing as advertised.

 

Best Regards,

 

Jim T.

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[AstroMike47]

Oh man. I am so glad I ran across this post just now as I was about 10 minutes away from ordering a NB set of Optolongs tonight.

I have HA & OIII Astrodons / SII Baader I can take out of my STF-8300 as I want to see how the new ZWO ASI 1600mm-Pro preforms in narrow band imaging. 

I was hoping to get shorter immigration times. I'm in edge of red / brown zone looking south into yellow zone. 

 

Now the question is are the LRGB Optolongs any good which I just received???

 

Thought please & tnx!

[andysea]

Mike, like I said a few posts back I returned the LRGB optlong due to reflections. I then Got a set of astrodon and the reflections were gone.

[Fongky]

I measured the spectrum of my Optolong 7nm filter tonight.  The resulting plot is attached below.  It appears that my Optolong filter is performing somewhat as advertised but not quite.  The transmissivity reported by Optolong at 656.3nm (Halpha) is supposed to be better than 80%, but I measured only 57%.  Also the off wavelength blocking is supposed to be OD3 (0.1%) but I measure around OD2.7 (0.19%) in the visual band, and OD2.0 (0.93%) in the NIR band.  Note that my measurement of spectrum rolls up at the ends due to my using a halogen lamp as my reference (ie. measurement error becomes large <400nm and >1000nm).  This filter is probably still usable for its intended purpose, but it is not performing as advertised.

 

Best Regards,

 

Jim T.

This is not too bad. I wonder if yours is a HWB630 or B270 glass filter? According to Optolong, the manufacturing materials and process were changed in August 2016.

[StarMike8SE]

I wonder if there is a way to determine when one was made!?

[StarMike8SE]

I measured the spectrum of my Optolong 7nm filter tonight.  The resulting plot is attached below.  It appears that my Optolong filter is performing somewhat as advertised but not quite.  The transmissivity reported by Optolong at 656.3nm (Halpha) is supposed to be better than 80%, but I measured only 57%.  Also the off wavelength blocking is supposed to be OD3 (0.1%) but I measure around OD2.7 (0.19%) in the visual band, and OD2.0 (0.93%) in the NIR band.  Note that my measurement of spectrum rolls up at the ends due to my using a halogen lamp as my reference (ie. measurement error becomes large <400nm and >1000nm).  This filter is probably still usable for its intended purpose, but it is not performing as advertised.

 

Best Regards,

 

Jim T.

I wonder which glass the one you tested had

[Fongky]

I requested Optolong to measure the off-band blocking of their current batch of Ha and SII filters if they are really OD3. They sent me a document with the picture of the test certificate of Koot’s Ha filter, the screen capture of the file folder, and the transmission curve generated when this filter was tested for QC before shipping. If you like to look at this document, here is the link, https://drive.google...iew?usp=sharing

The intention of showing us this document is to show that Optolong is able to retrieve the information of a specific filter based on its serial number. It also shows that Koot's Ha filter has been tested for off-band blocking of 0.1%



However, the off-band blocking is only tested for mercury and sodium wavelengths which are the common source of light pollution. We highlighted to them that the filter should be tested for all off-band wavelengths with a light source of continuum spectrum.

They told us that the certificate is designed for L-Pro, only key light pollution wavelengths are highlighted. For narrow band filters, it is understood that only the transmission wavelength is required in the certificate.

We pointed out to Optolong that it is stipulated in their specification, "0.1% transmission of off-band, specially the major emission lines of artificial light pollution". Such statement is misleading. If they are not tested, it should not be in the specification. The Chinese version of the specification even says "Blocking Area：＞OD3 （0.1%） @ 300-1100nm"

They replied that they are following the standard of Astronomik where by only the center transmission wavelength is shown and it is impractical to show the data from 300nm to 1000nm. In most cases, other manufacturers only show the transmission part of the curve. Since Baader and  Astronomik are not providing more data than Astronomik, Optolong will not need to provide any additional information. Optolong will only provide the transmission curve to its customers.

If you read both Chinese and English, the record of the online conversation is available here, https://drive.google...iew?usp=sharing

I am not really sure whether we will continue the discussion with Optolong in future.
 

Edited by Fongky, 20 December 2017 - 10:20 AM.

[OrionSword]

The aforementioned has been interesting reading.  My experience with Optolong at this point has only been with their 2" L-Pro filter.  I had to return my first one to the vendor as the M48/.75 threads would only engage about 3 quarters of a turn.  My IDAS P2 and D1 both thread fully into the same field flattener.  Also there were about five scattered diffuse avoid shapes within the image.  These did not appear to line up as reflections with any bright stars in the FOV.  Surface viewing of the filter showed it as being clean as new, so I can only guess there is a problem in one of the coating layers.

 

Received a new replacement and it thread perfectly.  So now it is up to clear skies to verify there are no blemishes as experienced previously in the image.

 

At first glance it appears the quality control inspections are not very consistent.  Hope they are succesful in reviewing their processes and materials.

[jimthompson]

I wonder Fongky if somehow your friend simply didn't get the filter he was supposed to at all.  Maybe the Halpha narrow band filter performs like the Optolong measured data but by accident some other filter glass got put in the aluminum cell and shipped to your friend.  When I look at your colour pattern with my mirrorless camera through my Optolong Halpha 7nm I get the attached image below.  Clearly different than what your friend has.  It is like he got entirely the wrong filter.

 

Best Regards,

 

Jim T.

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