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Old 08-02-2017, 08:56 AM
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UVIR-CUT filters from Alibaba... or Optolong L-Pro?

I found couple of ads on Alibaba for UVIR-CUT filters at very attractive prices (10 - 50 US$ .... bargain compared to Astronomik or Baader Planetarium prices), performance on ads looks good, but the overall presentation on Alibaba website somehow doesn't fill me with confidence, I have a feeling that both sellers and buyers do not know exactly what is going on and what will be received at the end of the day... especially after (bad?) experience with seller on ebay where last year I bought Rocolax filter with advertised transmission BW to be 400-700nm, but actually it turned out to be ~ 400-640nm - good for general photography, but not suitable for AP.
(I am sure somebody in the supply chain made a mistake or did not check properly)

Does anybody have some advice or comments?

Last edited by bojan; 09-02-2017 at 12:24 PM.
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Old 08-02-2017, 11:41 AM
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Been dealing with Alibaba for a while, my electric bike kits come through there and I've picked up a few other bits no problems. Always quite quick on delivery, sometimes for free. Always received what I've ordered although they haven't been as critical as filter specifications.
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Old 08-02-2017, 12:07 PM
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I have had good and bad experiences with Alibaba sellers, and some mainland Chinese sellers are very slow to deliver. Be aware of the February shutdown of business in China due to their new year holiday period, which affects some businesses for two weeks.

I used to buy Canon DSLR parts on a regular basis and woukd say 70% took about six weeks min to receive.

For something like an astro filter, i would stick to the respected brands with a history. There is a supplier in Hong Kong, Cyclops Optics, which i have purchased from - bought a cheap set of Optolong RBG filters (low cost Chinese brand). They are ok -just. I would not buy their narrowband filters however. You could look at ZWOs filters but i believe they are identical and from the same source supplier as the Optolongs. Both ZWO and Cyclops are Alibaba sellers. The Baaders and Astronomiks etc give you very precise specs, excellent multicoating, etc. I use Baaders for narrowband, purchased from Teleskop-Express, no regrets.
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Old 08-02-2017, 12:32 PM
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Hi Glen,
Thank you....
Optolong L-Pro filter looks OK.... a bit expensive but probably worth it.
UHC is cheaper...
I will consider.....
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Old 09-02-2017, 07:23 AM
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Just purchased unmounted 36mm L-Pro filter from Cyclops... It seems to be the better option than UVIR-CUT filter because it is also LP filter.
According to Cyclops, it is the same glass used for Clip-On variety..
So I decided I will 3D print the holder.
But... before starting my own design, I had a look at Thingiverse.. and found this design.
It is for 1.25" filters, so I will have to modify the STL file, as the central hole needs to accommodate 36mm x 2mm glass (this can be done by loading stl file into 123D (freeware from AutoDesk) and subtract the appropriate cut out.
This "fiddling" will save me $67... not insignificant amount.

For more general applications in the future (for other cameras and telescopes), this (or similar) design will be useful as the principle.

I am still looking for low-cost solution for UVIR_CUT filter on Alibaba... so far the lowest price is US$50 for 50x50mm sample.

EDIT
Because the design from Thingiverse is for 1.25" filter, 36mm glass will not fit into frame... So I will have to design my own, with lower profile springs.
I will post the design here when tested.

Last edited by bojan; 09-02-2017 at 12:29 PM.
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Old 09-02-2017, 07:45 AM
glend (Glen)
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Bojan, ZWO has a 2" Round IR Cut filter on their website for $49 USD.

https://astronomy-imaging-camera.com...ir-cut-filter/

There are a number of cheaper ones in smller sizes. You might be able to use one of the UV-IR Cut sensor cover windows and print a carrier for that. Sizes vary from 1.25 up. Don't pick an AR window as they do not block.
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Old 09-02-2017, 08:03 AM
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Hi Glen,
Thank you for the tip.
It seems all those filters are coming from the same source, as transmission plots are (sometimes) identical (as if those guys just copy-paste the data one from another).

Anyway, I will consider this filter for next month, right now my "allowance" is used 120%.
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Old 10-02-2017, 07:32 AM
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I was searching for converter of *.stl file into *.dxf and found this online utility:
http://www.cadforum.cz/catalog_en/stl2dwg.asp

It worked OK, and resulting file could be opened in LibreCAD (which is 2D). I have yet to try this with some 3D cad.

Also, there are other utilities that may help editing stl files:
https://all3dp.com/free-stl-editor-open-edit-stl-file/

Last edited by bojan; 10-02-2017 at 07:43 AM.
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Old 11-02-2017, 02:05 PM
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3D print looks good.
Now waiting for filter to arrive.
Attached Thumbnails
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Click for full-size image (Filter_clip_printout.jpg)
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Click for full-size image (Filter_clip_in.jpg)
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Old 16-02-2017, 04:56 PM
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While waiting for L-Pro filter to arrive, I contacted seller on Ebay from whom I purchased Rocolax UVIR-cut filter last year (it was $70!)
They promised to send me the new one (hopefully the wider one).
To strengthen my case, I put together my Hartridge spectrograph, calibrated the wavelength with energy saving bulb and processed images taken with $5 webcam in BASS software..

Instead of cutting off wavelengths above 670nm as per ad, the cutoff starts at 645nm.
I am hoping for the best outcome...

Also with the same setup I will be able to check L-Pro filter as well.
Attached Thumbnails
Click for full-size image (Rocolax_uvircut.jpg)
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Click for full-size image (c_07.jpg)
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Last edited by bojan; 17-02-2017 at 08:28 AM.
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Old 17-02-2017, 08:14 AM
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it seems wavelengths and China dont work out so well. I spent ages trying to find UV torches that actually were UV and not just purple torches, they just don't match the wavelengths listed and yes specs are just copy/pasted to fill in product descriptions. I've got a nikon clip-in filter from cyclops on its way, they've been great to deal with and I've got confidence in their listed product specs.

fyi, TinkerCAD is also a good online free 3D program for modifying 3d files for printing. It does a better job at some things than LightWave3D (which I've been using 15-20yrs) and I can work between both easily, if only my aldi 3d printer was so easy!
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Old 17-02-2017, 08:26 AM
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What is curious here is that Gary Honis is (re)selling 2" Rocolax UV-IR Cut filter and he told me it is quite OK for H-alpha.... So there must be a couple of varieties, all manufactured by uvircut.com (they or their office seem to be in Taiwan, and I tried to contact them directly but there was no response..)
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Old 17-02-2017, 04:58 PM
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L-Pro filter is here...
Test says it is probably OK, ~3x more H-alpa compared to Rocolax (y-axis calibration/linearity (gama) is still questionable).
Due to small sensor of this $5 webcam, only red part of the spectrum was captured.

Hopefully, it will be clear tonight....
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Old 19-02-2017, 05:47 PM
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I changed a concept slightly....
Adapter is still clip-on but to M42-EOS adapter.
The position of the filter relative to sensor is the same as conventional clip-mount, but the filter is attached to the lens/scope.
This way I have more flexibility in use of modified or unmodified or any camera in combination with any lens/telescope I have (all of them have M42-EOS adapter).
This adapter is easier to print with lower tolerances (0.1mm layer thickness, 85% infill, printing took 16 minutes) and the fit inside camera is better, it is tight but the elasticity of the material is sufficient to ensure self alignment.
Now I need a clear, light-polluted sky to test the whole thing, it seems Melbourne will be blessed with all that tomorrow.
Please note, the adapter ring is not solid, I made a cut (visible on the image at the away side of the adapter) so it could be widened to accept the filter.
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Last edited by bojan; 20-02-2017 at 01:02 PM.
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Old 21-02-2017, 06:02 AM
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Results of test from last night are attached.
While the contribution of the filter to LP extinction was somewhat disappointing (~50%... but still significant), the focus is drastically better.
However, some stars on the image are still bloated (halo is greyish), I think this may be due to presence of IR.

BTW, I returned Rocolax UVIR-cut filter to seller, they promised to send me back the correct one (hopefully they will perform some tests to ensure that... ).
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Click for full-size image (c_001.jpg)
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Last edited by bojan; 21-02-2017 at 07:58 AM.
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Old 21-02-2017, 07:31 PM
speedyjim (James)
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Ever tried a Hoya 49mm uv-ir cut filter? For a 2" filter they work out cheap and have full cut off at 700nm and appears it only starts to cut at 680nm. They are way cheaper than baader etc. You can remove from filter via spring circlip and use unmounted... Thoughts?

http://www.hoyafilter.com/hoya/produ...lters/uvircut/
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Old 21-02-2017, 07:57 PM
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Hoya was on my list, but it was quite expensive.. so I thought this L-Pro will do the job + LP... IR cut off is the same as Hoya, as per my own measurement.
That Rocolax was supposed to be the same as Hoya (for 1/3 price) , but it seems I received the wrong one.
The new one is on the way, we shall see what happens.

Last edited by bojan; 21-02-2017 at 09:22 PM.
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Old 21-02-2017, 09:50 PM
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Quote:
Originally Posted by bojan View Post
Results of test from last night are attached.
While the contribution of the filter to LP extinction was somewhat disappointing (~50%... but still significant), the focus is drastically better.
However, some stars on the image are still bloated (halo is greyish), I think this may be due to presence of IR.

BTW, I returned Rocolax UVIR-cut filter to seller, they promised to send me back the correct one (hopefully they will perform some tests to ensure that... ).
Hi Bojan,

Nice comparison of the with and without LP filter.

I did something similar with a didymium filter on Orion and have been meaning to post the image as part of my quest to reduce the effect of LP. Your thread has reminded me to do so, so I will soon. If you'd also like to try these filters in your fight against LP, since you're in Melb, let me know. I may have one in a size that you could borrow.

Best
JA

Last edited by JA; 21-02-2017 at 10:23 PM.
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Old 22-02-2017, 12:10 AM
speedyjim (James)
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Quote:
Originally Posted by bojan View Post
Hoya was on my list, but it was quite expensive.. so I thought this L-Pro will do the job + LP... IR cut off is the same as Hoya, as per my own measurement.
That Rocolax was supposed to be the same as Hoya (for 1/3 price) , but it seems I received the wrong one.
The new one is on the way, we shall see what happens.
I managed to get one off Amazon for $75 delivered. Most others were selling for $100 plus delivery
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Old 22-02-2017, 06:29 AM
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Quote:
Originally Posted by JA View Post
.... If you'd also like to try these filters in your fight against LP, since you're in Melb, let me know. I may have one in a size that you could borrow.

Best
JA
Thank you for the offer, I will PM you when I am ready

As for comparison....
the attached images below were taken with the same lens, left one is with unmodified 60D (last year), right one is with 450D FSM + L_pro (last night).

Some stars (with L-Pro) have halo, some others (of same or even higher magnitude) don't.
There are no halos on corresponding star images taken with unmodified 60D.
The difference is most likely in spectral type and excess of IR (most likely) or UV (I don't know yet what L-Pro filter does compared to Canon filter in 60D)
So, it seems more filtering will be needed to fix this (IR? I will know when replacement UVIR-cut from Rocolax arrives).
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