UV filter for Venus

[Relpet]

Attended a very interesting lecture by Dr. Colin Wilson from Oxford Uni  the other night where he gave us an hour-long talk about Venus.  He recommended getting a UV filter in order to bring out the detail in the Venusian atmosphere.  Blue would do but UV would be better.  I've got blue but never used it on Venus and fat chance of a trial with southern skies at present.  Have searched for a specifically UV filter, either 2" or 1.25" but come up blank.  Items available are usually described as UV/IR.  Would one of these do or is there a product any of you lovely people would recommend?  As Dr Wilson remarked, most of us have only seen Venus as white as the cue ball on a snooker table.  It would be nice to see more.

[riklaunim]

IR/UV cut are not "UV filters", they cut UV and IR for use in visible photography. A UV-only passing filter is Astrodon UVenus, Baader U-Filter or the new Optolong UV filter. You will also need a good mono camera, some aperture (best if it's a mirror only telescope) and you are ready to go. A cheap alternative would be to use visual violet #47 filter with Schott BG39.

Venus UV and deep IR imaging is quite common when the planet is nicely visible. Aside of cloud details there is also an option to capture Venus night side emission with a 1010nm filter when the phase is low.

[MarsG76]

Apparently a SCT corrector plate blocks a lot of the UV wavelengths and a Newtonian is a better option, but I still managed to get something through a 2X Barlow on my 8SE using a Astrodon UVenus filter.

Not much, but something... I used the uv channel as blue in RGB.

[riklaunim]

SCT corrector plate isn't that bad, but a Barlow lens may be Some coatings cut UV hard.

[RT65CB-SWL]

Hi 'Relpet',

AstroBoot have a No: #47 violet filter on sale. I believe this is what he means or Venus observers use. I purchased one earlier this year. I have not yet used it, therefore I am unable to comment as to how effective it is.

[Relpet]

IR/UV cut are not "UV filters", they cut UV and IR for use in visible photography. A UV-only passing filter is Astrodon UVenus, Baader U-Filter or the new Optolong UV filter. You will also need a good mono camera, some aperture (best if it's a mirror only telescope) and you are ready to go. A cheap alternative would be to use visual violet #47 filter with Schott BG39.

Venus UV and deep IR imaging is quite common when the planet is nicely visible. Aside of cloud details there is also an option to capture Venus night side emission with a 1010nm filter when the phase is low.

Thank you, that is very interesting.

[Relpet]

Hi 'Relpet',

AstroBoot have a No: #47 violet filter on sale. I believe this is what he means or Venus observers use. I purchased one earlier this year. I have not yet used it, therefore I am unable to comment as to how effective it is.

Good advice, Philip.  I just checked AstroBoot and they've got a bucket load in various sizes at very nice prices.  Many thanks.

[riklaunim]

Visually it still may be a feature-less blob - it depends on they eye and seeing. For imaging you will have to add BG39 like this one: http://uqgoptics.com/stock-product/FBG-3951.aspx

[Steve Ward]

Piotr's full and very informative UV imaging page is here ... 

http://www.rkblog.rk.edu.pl/w/p/optimizing-uv-venus-imaging/

[Dave In Vermont]

Both Baader and Schuler made UVenus-filters. I think the Astrodon is what Schuler was, but I'm not sure. In extensive comparisons, the Schuler won over the Baader one - by a hair. I have the Schuler one I bought over 10 years ago. Expensive glass it was.

Do remember: These are strictly for photography/imaging use only. They won't do anything but dim your view to a purple glow visually.

Have fun,

Dave

[Relpet]

Visually it still may be a feature-less blob - it depends on they eye and seeing. For imaging you will have to add BG39 like this one: http://uqgoptics.com/stock-product/FBG-3951.aspx

Thanks for the cautionary advice.  I spend half my time in SW France where the sky is much darker and clearer than in SE England so I'll see how things go.  My pal in France is more interested in imaging so I will let him know about the UQG filter.

[Relpet]

Piotr's full and very informative UV imaging page is here ... 

http://www.rkblog.rk.edu.pl/w/p/optimizing-uv-venus-imaging/

Thanks for the link, Steve.  That is really useful information.  I am continually astounded at how helpful SGL is, no matter what the question.

[Dave In Vermont]

Here's the test & results of a comparison of the Baader & Schuler Venus-Filters:

http://www.astrosurf.com/pellier/comparuvfilters

I finally found it - dredging my myriad Filter-files.

Enjoy!

Dave

[Relpet]

Here's the test & results of a comparison of the Baader & Schuler Venus-Filters:

http://www.astrosurf.com/pellier/comparuvfilters

I finally found it - dredging my myriad Filter-files.

Enjoy!

Dave

Thanks, Dave,

I read the piece with interest though it is not only seems a bit dated but deals with products way out of my price range, sadly.  However I did find this from Cloudy Nights which bears out a previous reply.

"I used to use a Schuler UV Venus filter. This filter is so dark it looks black. It works but it cost more than $100. I have seen other imagers get good results using just a #47 violet filter. I would try that first."

The #47 filter should be with me any day but I take the advice re imaging.  That will have to wair until I get back to France in the New Year.

Thanks again.  Nice to hear from you.

Peter (aka Fang).

[riklaunim]

Infra-red leak will wash out any UV detail #47 may give. That's why BG39 is used with this filter And it's also the reason why all UV filters are expensive - it's hard to make an UV filter without IR leak.

[Pete Presland]

I bought a #47 filter for purely imaging Venus with my C9.25, but I have had no success getting any detail. I have thought about buying a "Venus" filter, but the price puts me off and they don't turn up to often on the 2nd hand market.

[Dave In Vermont]

Infra-red leak will wash out any UV detail #47 may give. That's why BG39 is used with this filter And it's also the reason why all UV filters are expensive - it's hard to make an UV filter without IR leak.

IR-Filters aren't terribly expensive - last time I looked. Not exactly cheap though. Here's one in the US:

http://www.adorama.com/OSIRF.html?hotlink=t&svfor=5m&gclid=CJa_9JTqz8kCFYIlHwodCz0ANg

It was the IR that put the Schuler over the top in comparing to Baader. And yes, Fang( ), the UV-Filters cost a small fortune! It would be of interest to me to try a IR-filter with a #47 purple. Too true about the Schuler looking black. Visually you can tell the phase of Venus with it - barely though. So imaging would require a longish exposure. I never got around to such though. If any readers out there do try imaging with a #47 and IR filter, please do tell us the results. Or post same.

Have fun -

Dave

[riklaunim]

IR-Filters aren't terribly expensive - last time I looked. Not exactly cheap though. Here's one in the US:

 

http://www.adorama.com/OSIRF.html?hotlink=t&svfor=5m&gclid=CJa_9JTqz8kCFYIlHwodCz0ANg

It cuts UV and IR which isn't the thing you want to do (even when the name is simplified to "IR cut"). You need something that actually cuts IR without cutting UV. Try BG39 and not IR/UV cut if you want to get some UV images. (guess from which filters Schuller UV is made of ).

 

I bought a #47 filter for purely imaging Venus with my C9.25, but I have had no success getting any detail. I have thought about buying a "Venus" filter, but the price puts me off and they don't turn up to often on the 2nd hand market.

IR leak will always wash the detail off.

The #47 has such spectrum:

So you need to cut >= 700nm without cutting <= 400 nm which normal IR-cut filters won't do.

BG39:

And if you use star analyser with IR-leaking filter you will see how IR is stronger than UV signal:

So you don't have to try reinvent the wheel. Cheap as well as dedicated UV imaging filters are known and used with success.

[Relpet]

Infra-red leak will wash out any UV detail #47 may give. That's why BG39 is used with this filter And it's also the reason why all UV filters are expensive - it's hard to make an UV filter without IR leak.

The BG39 filter is on my Christmas list, thanks to the previous post on this subject.  Thanks to all for some very interesting and useful responses.

[Relpet]

Infra-red leak will wash out any UV detail #47 may give. That's why BG39 is used with this filter And it's also the reason why all UV filters are expensive - it's hard to make an UV filter without IR leak.

I've just been examining the spec of the Nikon d5100 dSLR I use for imaging and found that a BG39 filter is built in as standard.  So, being a bear of very little brain, standing on the very lowest rung of the long ladder of expertise, would I be right in thinking that shooting through a Barlow plus the #47 violet filter with this camera would give me the right combination?

Thanks again.

[Dave In Vermont]

I just chased down the BG39 filters over here. Astrodon being the brand and $200US everywhere that carries them.

I'm glad I already have the Schuler. This would kill me! Better luck at a lower cost across the pond.

Dave

[riklaunim]

There are two problems - color sensor and possible coatings on that BG39. If the filter has some additional coatings on that built in BG39 filter then it may cut UV. Second - color sensors are quite insensitive in UV. You can try but it will be rather hard to get anything. Good mono planetary camera is required for hassle-free UV imaging.

And side note - shops with filters like UQG, Thorlabs or Edmund Optics have some other filters too. For UV imaging with BG39 some other filters than Wratten #47 could be used (like some Hoya filters). ~25mm diameter filters can be mounted in plastic filter cells of SkyWatcher moon filters, or if you want to stack BG39 with violet - put the BG39 inside the violet filter cell and lock it with a bit of paper put on the sides of the filter.

[Relpet]

There are two problems - color sensor and possible coatings on that BG39. If the filter has some additional coatings on that built in BG39 filter then it may cut UV. Second - color sensors are quite insensitive in UV. You can try but it will be rather hard to get anything. Good mono planetary camera is required for hassle-free UV imaging.

And side note - shops with filters like UQG, Thorlabs or Edmund Optics have some other filters too. For UV imaging with BG39 some other filters than Wratten #47 could be used (like some Hoya filters). ~25mm diameter filters can be mounted in plastic filter cells of SkyWatcher moon filters, or if you want to stack BG39 with violet - put the BG39 inside the violet filter cell and lock it with a bit of paper put on the sides of the filter.

You know, I'm getting so much information from SGL to questions I would never even have dreamed of asking before I took up this pastime 8 months ago I feel as If I've strayed into a parallel universe.  The only problem is my shopping list keeps getting longer.  Good mono planetary camera, eh?  I've checked out good ones and that's my pension for three months, assuming I can live without food, heat, light, put the car on blocks and evade the monthly expectation from the tax man.

Most of my stuff is in France, where the skies are much more observer-friendly, so I'll give the Nikon a go with the #47 next time I get down there.  If the images are not good enough I'll check out Polish and other European online shops where the pound sterling goes a little further these days than in the land of its birth.

Thanks again for all the wonderful advice, which I hope one day I'll be able to follow!.

[riklaunim]

Astro hardware from Asia is prices usually in USD so GBP would have to be strong against USD. New ASI120 or QHY5L-II start around 130 GBP, where there may be also additional sales Some used may show up on astrobuysell as people may upgrade to new cooled ZWO cameras

[Relpet]

Astro hardware from Asia is prices usually in USD so GBP would have to be strong against USD. New ASI120 or QHY5L-II start around 130 GBP, where there may be also additional sales Some used may show up on astrobuysell as people may upgrade to new cooled ZWO cameras

I am greatly encouraged by those recommendations.  The ASI 120 and the QHY5L-II are both available at prices in sterling which have come down considerably from when they were first launched. Images I have seen on line from either camera would be very satisfactory to a novice like me.  Thank you.