H alpha filter as ERF?

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H alpha filter as ERF?

Post by minhlead »

Hi everyone,
I am using a UV/IR cut filter with my Quark but I am suspecting the UV IR cut does not reject enough heat.
The reason for this is my the etalon seems heats up considerably considering that I have to turn the knob all the way counter clockwise and I read somewhere counter clockwise is Quark's oven temperature down and the longer my observing session is, the CWL seems to be shifted even more to the red since the detail seems to disappear even when the Quark has been shifted blue all the way (the knob is at -5). I am from VN and summer here can be incredible hot. We're just at the start of summer and temperature here already hit 38-40 degree Celcius (104 F) outside (it can reaches up to 45-50 degree easily when it's peak of summer here).
So I am finding a way to better reject heat before it reaches the etalon, a Ha filter seems to be a good way. I have a disposable SVbony 1.25 mm 7nm Ha filter that I am intending to mount at the nose of the Quark. Would that work?
Thanks!


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Re: H alpha filter as ERF?

Post by AndiesHandyHandies »

Hi

The 35nm Baader H-alpha works well, its hard coated. And rejects IR up to 1100nm. The 7nm Baader is less good in IR. For longer IR rejection you can use a Beloptik UV-IR coated KG3 but it must be after a ERF or for visual on the eyepiece say.

The SVbony looks OK https://www.svbony.com/h-alpha-filter-7nm#F9169A

Cheers. Andrew.


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Re: H alpha filter as ERF?

Post by minhlead »

AndiesHandyHandies wrote: Mon May 10, 2021 7:49 am Hi

The 35nm Baader H-alpha works well, its hard coated. And rejects IR up to 1100nm. The 7nm Baader is less good in IR. For longer IR rejection you can use a Beloptik UV-IR coated KG3 but it must be after a ERF or for visual on the eyepiece say.

The SVbony looks OK https://www.svbony.com/h-alpha-filter-7nm#F9169A

Cheers. Andrew.
Thanks Andy. This afternoon I do a little experiment. First I take out all the filter and put my hand under focused light cone. Ouch, it burns almost immediatelly. Then I take the filter and put it into light path, this time the focused light cone is not so hot, I can comfortably put my hand into it without any problem. I think any residual heat can easily be filtered out by the blocking filter. So I figure I'd use the filter and do some test. The result is promising, the Quark now tune fine even under intense sun and 41*C ambient (it some times refuse to turn green when I set the knob to -5 when it's too hot. I still got best result from -5 knob though).
Think I'll use this one and keep experimenting. Thanks for the advice.


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Re: H alpha filter as ERF?

Post by Valery »

minhlead wrote: Mon May 10, 2021 12:50 pm
I am also interested in your ERF, do you have a link where I can find out more about them? Thanks again.
We do not produce such small filters. 140mm is the smallest model and only if we gazered a full batch (8 pc).

BTW Still, I advice you to buy a full aperture DERF of 100mm size. There are plenty of them and not that expensive.
In such a small telescope a 2" derf is OK if it installed on the front end of the focuser moving tube.


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Re: H alpha filter as ERF?

Post by Montana »

The Baader D-ERF is very good indeed.

Alexandra


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Re: H alpha filter as ERF?

Post by EGRAY_OBSERVATORY »

Does sound rather scary to burn hands and no-doubt some other gear too, let alone the eyes, if mistooks are made !!!

PLEASE ALWAYS ER ON THE CAUTION-SIDE OF SOLAR IMAGING/VIEWING - AS THIS FOR US - IS A HOBBY AND NOT WORTH THE PERMANENT RISKS. LEAVE THE DANGEROUS/DAMAGING EXPERIMENTING TO THE PROFESSIONAL "BIG FIRMS" WHO HAVE THE FUNDING AND SAFETY-GEAR TO DEAL WITH THESE SORTS OF ISSUES....

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Re: H alpha filter as ERF?

Post by Montana »

Minh, as you are using a Quark at 100mm aperture and less, Daystar do state that you do not need a front ERF. However, as you are finding it is getting very hot in your environment then using an internal ERF to protect it is better. It is well known that a Baader red h alpha filter 35mm like Andy stated is much better than a UV/IR filter see here viewtopic.php?f=10&t=24689&p=222191&hil ... nm#p222191

I use one in front of my PST modification too. However, to prevent internal heating in the tube which is bad for imaging then it is better to use a front ERF like a Baader D-ERF instead.
The Quark is safe for visual if you follow the instructions by Daystar, using an internal Baader red as a ERF in front of the Quark is also safe, as is using a front D-ERF.

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Re: H alpha filter as ERF?

Post by Rusted »

I have lots of nasty experiences with sub-aperture Baader D-ERFs placed INSIDE the telescope.
Note that I image all the hours in the day if the sun is out. That is a lot of heat exposure compared to many hobby imagers.
Who can only image when time allows. I am retired so can spend countless hours in the observatory.

I permanently cooked my ZWO ASI120 camera DESPITE using a 90mm INTERNAL Baader D_ERF with my 150mm f/8.
This was AFTER all the usual PST components of course.
I count myself lucky I rarely did any visual observing with that sub-aperture D-ERF!

I was able to burn my hand instantly at focus with the 90mm D-ERF midway in the light path of the 150 f/8 with no PST components in place.
Can you imagine the heat being pushed through the entire PST optical train! Secondhand PSTs cost £500-600 in the UK!

I set fire to a cardboard stop ring which caught the fiercely re-focused reflection from the INTERNAL D-ERF.
The cardboard had warped and sagged into the intense, re-focused beam in the dewshield.
I was choking with smoke in the observatory and assumed a thoughtless neighbour had lit a bonfire!
I have no idea how the 6" f/8 lens survived the flames from the burning cardboard!

Fortunately I was always aware of the extreme dangers of looking into the dewshield when the sun was out.
Imagine if I had not been present! I regularly leave the telescopes tracking the sun from 8am-6pm!
In a closed, rural observatory with NO visitors.

Having decided to get serious about solar imaging I bought a 160mm Baader D-ERF to go IN FRONT of my new 150mm f/10 iStar objective.
I added 2" KG3 and Baader 35nm filters well in front of the PST etalon to further protect my next ZWO camera. An ASI174mm.
I monitor the camera temperature reading constantly in the capture software.
Had I cooked my expensive ASI174 I would probably have given up solar imaging or observing altogether.

TAKE NO CHANCES WITH THE SUN! It is very unforgiving.


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H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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Re: H alpha filter as ERF?

Post by DeepSolar64 »

Daystar states that if an objective is 80mm or below an ERF is not needed with a Quark. Any bigger, yes.
TAKE NO CHANCES WITH THE SUN! It is very unforgiving._ Rusted
So true this is!!


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Re: H alpha filter as ERF?

Post by minhlead »

Rusted wrote: Mon May 10, 2021 6:10 pm TAKE NO CHANCES WITH THE SUN! It is very unforgiving.
That is some scary experiences right there. This is going to go straight onto my observatory wall in big, bold print.


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Re: H alpha filter as ERF?

Post by EGRAY_OBSERVATORY »

In other words Minh, please always remember:-

"If it can go wrong, it will go wrong."

("Murphy's Law" refers) as https://en.wikipedia.org/wiki/Murphy%27s_law etc.

Please be safe and see the Sun, rather than just be able to feel its' heat..

Terry
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Re: H alpha filter as ERF?

Post by Merlin66 »

I had a discussion with Daystar Re the heating only to come on band with the Quark.
I ordered a Quark and then had some concerns about temperature.
At that time the Quark heater was said to work up to 27 deg C.
My problem, like yours, was the ambient temperatures here in Australia can easily exceed 40-45 deg C during summer.
After some (lengthy) discussion they suggested when ordered I needed to specify the "working temp" and they would try to find an etalon/ heater set-up which could work well.
After some thought.... I cancelled the order.
It would be interesting to hear from other Quark users about issues/ concerns they may have with temperature.


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Re: H alpha filter as ERF?

Post by AndiesHandyHandies »

Hi

The Beloptik UV-IR KG3 needs to go after the ERF with UV-IR blocking of whatever sort. As the KG3 absorbs IR. Then it only absorbs the longer IR. Most dielectrics only block out to 1100nm or so. Any UV-IR coating is dielectric. KG3 is the only common option available to block over 1100nm and makes a measurable difference at the eyepiece used for visual. Mark thinks it improves CCD results. And on a PST I thought it made an improvement visually. Does the same as the ITF in a PST. Supposedly now used in commercial etalons to block the long IR.

Dielectric filters reflect the unwanted light so you have to be careful with reflections. Because they reflect the unwanted light they are cooler than coloured glass based ERFs.

I have posted here collected transmission of commercial ERFs with help from Merlin.

The Baader D-ERF passes 100nm so there is more heat on the etalon than a Baader 35nm or similar filter. Some commercial ERFs pass more. UP to 60% !!!

I would add a Baader 35nm amd Beloptic KG3 after most commercial D-ERFs in a PST Mod.

You can measure the temperature of the ERF and its holder with a remote IR thermometer.

Any internal ERF should be as far up the light path as possible to share the light out on it. Astrograph used Baader 35nm ERFs in refractor based solar telescopes he sold up to 6". I would say 1.25" up to 4" and 2" up to 6" is reasonable.

As you can get larger photographic UV-IR filters you could use one as a pre-filter to go larger.

On my Rumak180 on the sunniest day, the PST Collimator lens then a Baader 35nm in an aluminium nose piece, with the front clean bare polished aluminium, measures 65deg C. The reflected beam is spread back out as it came in by the collimator lens so no reflected hot spot. The thermometer pointed up the eyepiece peaks at 32deg C. I have moved the Beloptic KG3 after the etalon as cooler there. I am trying a 1.25" SVbonny UV-IR as a pre-filter which happens to go in the front of an extra baffle in the Rumak, give 8mm fully illuminated field as sweet spot size, and that reduced the temperature on the Collimator lens and Baader 35nm a good deal. My scope has no plastic in it!

You can add another ERF after the etalon for extra safety if you like. With the Blocker filter and Etalon much cooler there.

Rogerio Marcon uses a 8" Zeiss with only a chunk of alloy as a baffle and 'ERF'.

Care is needed doing visual Solar work.

Also I cannot justify the cost of a front ERF for just 4 good days in a year when it would make a difference.

Using the same filter technology the absorbed heat per unit solid angle is the same for a front or internal ERF.

Cheers. Andrew.


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Re: H alpha filter as ERF?

Post by minhlead »

AndiesHandyHandies wrote: Tue May 11, 2021 8:58 am Hi

The Beloptik UV-IR KG3 needs to go after the ERF with UV-IR blocking of whatever sort. As the KG3 absorbs IR. Then it only absorbs the longer IR. Most dielectrics only block out to 1100nm or so. Any UV-IR coating is dielectric. KG3 is the only common option available to block over 1100nm and makes a measurable difference at the eyepiece used for visual. Mark thinks it improves CCD results. And on a PST I thought it made an improvement visually. Does the same as the ITF in a PST. Supposedly now used in commercial etalons to block the long IR.

Dielectric filters reflect the unwanted light so you have to be careful with reflections. Because they reflect the unwanted light they are cooler than coloured glass based ERFs.

I have posted here collected transmission of commercial ERFs with help from Merlin.

The Baader D-ERF passes 100nm so there is more heat on the etalon than a Baader 35nm or similar filter. Some commercial ERFs pass more. UP to 60% !!!

I would add a Baader 35nm amd Beloptic KG3 after most commercial D-ERFs in a PST Mod.

You can measure the temperature of the ERF and its holder with a remote IR thermometer.

Any internal ERF should be as far up the light path as possible to share the light out on it. Astrograph used Baader 35nm ERFs in refractor based solar telescopes he sold up to 6". I would say 1.25" up to 4" and 2" up to 6" is reasonable.

As you can get larger photographic UV-IR filters you could use one as a pre-filter to go larger.

On my Rumak180 on the sunniest day, the PST Collimator lens then a Baader 35nm in an aluminium nose piece, with the front clean bare polished aluminium, measures 65deg C. The reflected beam is spread back out as it came in by the collimator lens so no reflected hot spot. The thermometer pointed up the eyepiece peaks at 32deg C. I have moved the Beloptic KG3 after the etalon as cooler there. I am trying a 1.25" SVbonny UV-IR as a pre-filter which happens to go in the front of an extra baffle in the Rumak, give 8mm fully illuminated field as sweet spot size, and that reduced the temperature on the Collimator lens and Baader 35nm a good deal. My scope has no plastic in it!

You can add another ERF after the etalon for extra safety if you like. With the Blocker filter and Etalon much cooler there.

Rogerio Marcon uses a 8" Zeiss with only a chunk of alloy as a baffle and 'ERF'.

Care is needed doing visual Solar work.

Also I cannot justify the cost of a front ERF for just 4 good days in a year when it would make a difference.

Using the same filter technology the absorbed heat per unit solid angle is the same for a front or internal ERF.

Cheers. Andrew.
Thanks Andy,
I do get the basics of this. And I am 100% agree with you on the justifications of front mounted ERF, especially with a small scope like mine. But if I upgrade to large aperture in the future (and I'll), I think I'll go with an external ERF for peace of mind.


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Re: H alpha filter as ERF?

Post by AndiesHandyHandies »

Hi

One of the standard red spot thermometers helps with peace of mind as well.

Pointed at front filters after quick removal to check they are no where near melting
and
up the eyepiece for the black body equivalent temperature of the light coming out.

Which Quark do you have? One with a 4.2x barlow on the front? If the entrance is about 9mm I would put the filter on the front of the diagonal where its fully illuminated. Also with the Barlow you are only picking up the centre of the telescope image anyway so vignetting there not an issue.

Cheers. Andrew.


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Re: H alpha filter as ERF?

Post by minhlead »

AndiesHandyHandies wrote: Tue May 11, 2021 9:28 pm Hi

One of the standard red spot thermometers helps with peace of mind as well.

Pointed at front filters after quick removal to check they are no where near melting
and
up the eyepiece for the black body equivalent temperature of the light coming out.

Which Quark do you have? One with a 4.2x barlow on the front? If the entrance is about 9mm I would put the filter on the front of the diagonal where its fully illuminated. Also with the Barlow you are only picking up the centre of the telescope image anyway so vignetting there not an issue.

Cheers. Andrew.
I did test the sub aperture ERF with a thermometer and curiously, the UV IR Cut heats up considerably (about 15 degree from ambient) while the 7nm Ha only warms up a little (3-4 degree Celcius) Maybe the 7nm reflects more and less absorbing than the UV IR cut is the reason.


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Re: H alpha filter as ERF?

Post by Rusted »

It would be useful to have this sort of temperature gain data for common optical components in a skeleton tube OTA.
The [laser guided] remote sensing thermometers need a clear shot to be able to measure surface temperature.
Most of us have sealed OTAs where such access is all but impossible.

I tried the "exterior" sensor [on a lead] of a digital IN/OUT thermometer but it doesn't properly register heat in the optical light path.
Probably because is it white plastic encapsulated. Perhaps I really need an "oven" thermometer with a bare metal sensor? :shock:


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Re: H alpha filter as ERF?

Post by AndiesHandyHandies »

Hi

I whip the PST mod out of the focuser to measure the nose temperature.

Cheers. Andrew.


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Re: H alpha filter as ERF?

Post by minhlead »

AndiesHandyHandies wrote: Wed May 12, 2021 6:49 am Hi

I whip the PST mod out of the focuser to measure the nose temperature.

Cheers. Andrew.
Me too. I use a filter drawer so pulling it out for measuring is quick and easy.


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Re: H alpha filter as ERF?

Post by Rusted »

My 50mm protection filters are on a long extension well up inside the main tube.
Thereby hoping to avoid the hottest section of the focused beam near the focus.
I'd have to withdraw the entire optical train including the PST etalon, fittings and blocking filters.
I wonder whether the filters have the thermal capacity to hold their working temperature?


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H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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Re: H alpha filter as ERF?

Post by minhlead »

Rusted wrote: Wed May 12, 2021 11:44 am My 50mm protection filters are on a long extension well up inside the main tube.
Thereby hoping to avoid the hottest section of the focused beam near the focus.
I'd have to withdraw the entire optical train including the PST etalon, fittings and blocking filters.
I wonder whether the filters have the thermal capacity to hold their working temperature?
I loosen the retaining ring on the filter holder a bit until the filter rattles very slightly in the holding cell to allows some room for thermal expansion, hoping it won't break even if delta T is high


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Re: H alpha filter as ERF?

Post by solarchat »

Gentlemen, please refrain from disparaging others on this forum.
Feel free to state your preferences for products but I will not have this forum turn in to iceinspace or cloudynights where people make malicious comments about others.
End of discussion.

This topic was moved to solarscope modifications where it belongs.


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