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Classic Refractors and H-alpha viewing

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#1 Spyke

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Posted 09 August 2020 - 05:15 AM

Hi.

 

I hope these aren't silly questions.  I was wondering if any of you use your older refractors with H-alpha filter systems, such as the Daystar Quarks, for viewing of the Sun.  I was contemplating using my Swifts, as I have all the hardware necessary, but something (caution) held me back until I had enquired on here to see if there are any classics-specific pitfalls to be aware of.

 

My thinking is, the high focal ratios and good quality glass should be a perfect match for the Quark and other H-alpha filters, and my Swifts in particular have metal construction, so no risk of plastics melting.... but I'd hate to miss something and regret it afterwards.

 

Even if mine aren't suitable, I'd be interested to learn more of classic telescopes being used to study our Sun.

 

Ant  :cool: 


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#2 Astrojensen

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Posted 09 August 2020 - 05:57 AM

I have used, and use, my Daystar Quark on a variety of classic refractors, chiefly my Zeiss Telemator, but also my 80/1200mm Vixen achromat and 85/1575mm Zeiss A apochromat. 

 

If the focal length is too long, you can use a focal reducer in front of the Quark, to reduce the focal length and image scale. This might need quite a bit of inward focuser travel, though, and not all instruments come to focus. An alternative is to use the Combo Quark and use a weaker barlow or powermate. The resulting focal ratio should be around f/30-32 or slower, so if the scope is f/15, use a 2x barlow/powermate. The original Quark has a built in 4.2x telecentric barlow, so a f/15 refractor ends up as a whopping f/63! 

 

But the long focal ratios has a benefit: The bandwidth gets narrower and this increases contrast! You can also use a reducer AFTER the Quark, but the field then gets very narrow. Contrast is preserved, however, so this can be the way to go. 

 

One thing to be aware of, is that the Quark is a bit heavy, so the focuser must be up to the job. A weak focuser will tilt the Quark relative to the optical axis and this will shift the observed wavelength, just like the tilt tuner on some front-mounted etalons. For this reason, I am particularly fond of my Zeiss Telemator as a solar H-alpha scope, as the accesories are solidly threaded onto the visual back and there are no moving parts, as the focusing is done by moving the objective.

 

gallery_55742_4772_130798.jpg

 

And yes, the original Quark, because it has a telecentric barlow, allows you to come to focus with a binoviewer! And this REALLY brings out the details. The Sun is surprisingly low contrast and a binoviewer helps a lot here.

 

 

Clear skies!
Thomas, Denmark


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#3 Spyke

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Posted 09 August 2020 - 07:14 AM

That all makes sense, Astrojensen, and it's good to know that I'm not the only one thinking of using their classic refractor for this.

 

I usually use more modern achromats and Apos with my original Quark, so am aware of the image amplification that's built into the system and the reduction of bandwidth with increased focal ratio.

 

Focuser sag is something I hadn't considered, so that's very helpful. I'll have to assess the focusers and see if I think they will affect the alignment as the weight of a Quark, diagonal and eyepiece is considerable for a 50-odd year old focuser!

 

Thanks!



#4 Garyth64

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Posted 09 August 2020 - 07:46 AM

I've made a white light filter from Baader film, and I use them on some of my classic scopes.  The Sears 6339a has one in the dew shield. 

 

We do a yearly "Sun" day at one of the local schools,   

 

Sun day 1.jpg

 

(I was going to take another photo, since one of the teachers walked by, but I didn't get around to it.)

 

We were there for entire day.  Every hour a different science class would come out of the school with their teachers to get a look at the Sun.

Our club had some other scopes, non classics, also set up.


Edited by Garyth64, 09 August 2020 - 07:51 AM.

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#5 Spyke

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Posted 09 August 2020 - 09:27 AM

Very nice, Gary. Nice to see you hitting the public with a double whammy: "Come see our cool scopes, and come see the Sun while you're at it!" :)

 

White light isn't such an issue - I regularly use old scopes with white light filters already, but need to find myself a 1.25" Herschel Wedge to really get the best views. 

 

Ant


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#6 Terra Nova

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Posted 09 August 2020 - 09:57 AM

I’ve used a Daystar T-scanner and a Thousand Oaks prominence filter with my Unitron 114, Unitron 140, and both my Taks.

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#7 Terra Nova

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Posted 09 August 2020 - 10:08 AM

The deal with the T-scanner and the Prom filter is you have to boost the working focal length to between F24 and F35, hence the TV Powermate. You really need a telecentric to do that. A barlow will work but the Powermate, being more of a true telecentric is better. You want the rays going through the rear etalon to be near parallel.


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#8 Bomber Bob

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Posted 09 August 2020 - 10:50 AM

my Swifts in particular have metal construction

 

My Swift 838 was my Solar Scope until our grandson got it.


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#9 Piggyback

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Posted 09 August 2020 - 12:01 PM

IMG_0643.JPG

 

DayStar 0.7A ATM, Telecentric Barlow, Starlight focuser on my Telemator. Sitting idle for the past couple years. Praying for some mentionable solar activity to reappear. bow.gif


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#10 Spyke

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Posted 09 August 2020 - 12:05 PM

attachicon.gifIMG_0643.JPG

 

DayStar 0.7A ATM, Telecentric Barlow, Starlight focuser on my Telemator. Sitting idle for the past couple years. Praying for some mentionable solar activity to reappear. bow.gif

There's been lots happening over the last few days. Prominences, filaments, Active Regions - the works! Time to wake it up!  :) 


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#11 Terra Nova

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Posted 09 August 2020 - 12:10 PM

I need to brave the heat and humidity and get out there I guess.


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#12 RichA

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Posted 09 August 2020 - 04:38 PM

Hi.

 

I hope these aren't silly questions.  I was wondering if any of you use your older refractors with H-alpha filter systems, such as the Daystar Quarks, for viewing of the Sun.  I was contemplating using my Swifts, as I have all the hardware necessary, but something (caution) held me back until I had enquired on here to see if there are any classics-specific pitfalls to be aware of.

 

My thinking is, the high focal ratios and good quality glass should be a perfect match for the Quark and other H-alpha filters, and my Swifts in particular have metal construction, so no risk of plastics melting.... but I'd hate to miss something and regret it afterwards.

 

Even if mine aren't suitable, I'd be interested to learn more of classic telescopes being used to study our Sun.

 

Ant  cool.gif

Kind of wonder how hot an uncoated lens might get since it absorbs about 15% of the sun's light.


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#13 Terra Nova

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Posted 09 August 2020 - 05:37 PM

Kind of wonder how hot an uncoated lens might get since it absorbs about 15% of the sun's light.

The bulk of the heat concentration is in the back around the focal point. Also, most systems with rear-mounter etalons have energy rejection filters in front of the objective. 


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#14 Spyke

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Posted 10 August 2020 - 01:21 AM

The bulk of the heat concentration is in the back around the focal point. Also, most systems with rear-mounter etalons have energy rejection filters in front of the objective. 

When using the Quark in "smaller" refractors it's ebough to have a UV/IR filter in front of the Quark itself, usually screwed into the front of the diagonal. None of my scopes so far have needed a front-mounted ERF. But again, that's something worth thinking about for these older scopes maybe...


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#15 Terra Nova

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Posted 10 August 2020 - 06:44 AM

When using the Quark in "smaller" refractors it's ebough to have a UV/IR filter in front of the Quark itself, usually screwed into the front of the diagonal. None of my scopes so far have needed a front-mounted ERF. But again, that's something worth thinking about for these older scopes maybe...

Yes, that is true but I was speaking to my own personal experience with traditional H-a systems.


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#16 Astrojensen

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Posted 10 August 2020 - 11:34 AM

Kind of wonder how hot an uncoated lens might get since it absorbs about 15% of the sun's light.

An uncoated lens doesn't absorb 15% of the incoming light. An uncoated glass surface reflects 4% of the light and glass absorbs about 1% per inch of thickness. In a small, say, 3" objective, this means that if left uncoated, about 15% of the light is reflected and 0.5-1% is absorbed.  

 

If glass absorbed that much energy, large windowpanes, which are not coated, would get very hot in the Sun, but they're quite cool to the touch, even on a summer day. 

 

Even a green bottle, which DOES absorb a lot of the energy, doesn't get particularly hot in direct sunlight. 

 

 

Clear skies!
Thomas, Denmark


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#17 highfnum

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Posted 11 August 2020 - 02:42 PM

i posted several images with edmund 3 an 4 inch with quark combo eyepieces 

work very well at f15


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