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Solar observing with classic refracting telescopes

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#1 terraclarke

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Posted 12 February 2013 - 03:49 PM

It was a beautiful warm, clear, sunny day here today so I took advantage to do a little solar observing.



#2 terraclarke

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Posted 12 February 2013 - 04:02 PM

Here is my Unitron 140 set up for h-alpha solar observing. I just spent a an hour or two outside on the deck doing some solar observations. I now understand how that Unitron alt-az mount works a lot better than before. Adding an h-alpha train to the rear end (uniclamp, h-alpha unit, televue telecentric, 1 1/4 inch diagonal and larger, heavier 1 1/4 inch eyepiece adds a lot of weight to the rear and makes the spring-loaded altitude a lot weaker. I had to move the tube way up just to have enough leverage for it to not be a teeter-totter.

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#3 terraclarke

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Posted 12 February 2013 - 04:06 PM

The H-alpha unit is 0.9 angstroms. The telescope is operating at full aperture and a "hot mirror" (Baader UV-IR cut filter) and B+W #29 deep red behind it act as the behind the objective ERF (energy rejection filter). These filters are threaded into the nose of the Televue 2.5X Powermate which acts as a telecentric and brings the focal ratio up to F37.5.

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#4 terraclarke

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Posted 12 February 2013 - 04:20 PM

Here's an image of one group of prominences that I snapped with my i-phone today.

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#5 terraclarke

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Posted 12 February 2013 - 04:24 PM

I also set up the 140 for white light with my Intes solar wedge. Images of sunspot detail were a little soft using this vintage 9mm volcano top ortho yielding a magnification of 133X, which is pretty high for daytime seeing.
Auxiliary filters with the wedge were a B+W N.D. 3.0 and a single Celestron (Japan) polarizing filter.

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#6 pbealo

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Posted 12 February 2013 - 04:29 PM

Very nice results.
At last year's Stellafane Bart Fried was using a Brashear hershel wedge on his 4" alt-az Brashear and getting great images, but white light obviously. So the next day I took out MY Brashear hershel wedge that I'd been afraid to use (somehow I thought its age would be an issue) and used it on my 4" Clark. Lots of fun. Very nice white light images. Adding H-a increases the pleasure immensely!

Peter B.

#7 terraclarke

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Posted 12 February 2013 - 04:37 PM

Hi Peter,

I love wedges. I have the Intes and the Lunt. I love the Intes as it has no additional filters built in, only the wedge so its very flexible for work with specialized Ca, Na, Fe, and H-a filters. The Lunt is nice because the N.D. 3.0 is built in so no worrys; it is wonderful with the Baader continuum filter.

Terra

#8 terraclarke

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Posted 12 February 2013 - 04:38 PM

Changing eyepieces out a little later, this 12mm Surplus Shed ep yielded and incredibly sharp image of sunspot detail at 100X. The general rule of thumb for daytime seeing is 25 to 30X per inch aperture.

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#9 Astrojensen

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Posted 12 February 2013 - 04:40 PM

Sunshine, grass, buds on the twigs, a classic scope on the patio... For a northern observer, buried in snow, who hasn't observed the sun since sometime in late October, this is almost torture.

And spring is still two months away.


Clear skies!
Thomas, Denmark

#10 terraclarke

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Posted 12 February 2013 - 04:42 PM

Last week I set up my Monolux 60mm equatorial for h-alpha. I used a full aperture ERF and the 2.5X powermate (initial 60mmx912mm) so operating at F38.

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#11 Astrojensen

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Posted 12 February 2013 - 04:47 PM

The general rule of thumb for daytime seeing is 25 to 30X per inch aperture.


With my Herschel wedge or objective filter, I prefer much lower magnifications, generally. 10x - 20x per inch seems to work fine for me here. Only rarely do I use higher and then the seeing must be excellent.

With my projection box on my 85mm Zeiss apochromat, I generally used much higher magnifications. 177x - 400x was normal. Occasionally, if the seeing was excellent and there was some interesting action going on, I would use 800x. I sometimes saw extraordinary details.


Clear skies!
Thomas, Denmark

#12 terraclarke

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Posted 12 February 2013 - 04:48 PM

The ERF is a 72mm B+W #29 Deep Red. It seats perfectly into the dew shield, resting on the flange above the threads, but to be on the safe side i put a little drafting tape around the edge. Drafting tape is nice because it peals off cleanly and leaves no adhesive residue.

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#13 terraclarke

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Posted 12 February 2013 - 04:51 PM

Here is an image of the proms from that day. (Again, just a snap with my iPhone.)

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#14 terraclarke

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Posted 12 February 2013 - 04:55 PM

Hi Thomas,

Springtime comes early here in the Upper South. I am very thankful for that. Nearly three months with little to no observing and I was going stir crazy. It has been either cold or cloudy since Thanksgiving here. I think the last day I did any substantial solar observing until last week was Thanksgiving Day on Nov 23 while the turkey was baking in the oven. I hope spring and clear skies come early for you too.

#15 terraclarke

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Posted 12 February 2013 - 04:59 PM

I think that the highest I have gone up to was around 220X with my Lunt wedge on my 4 inch refractor. The granulation and faculae as well as the sunspot detail, light bridges, etc. was amazing. I need to get back into doing some solar projection. I have the solar projection kits for my Monolux and Sears refractors and am going to build one for the Unitron 140 since I have the brackets already on the scope.

Terra

#16 Astrojensen

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Posted 12 February 2013 - 05:09 PM

I sure could use some sun and starlight around here. I am getting cabin fever and spend way too much time for my own good, shopping astrogear...

I never was a big fan of open solar projection screens other than for educational purposes. The projection box I've made for my 85mm Zeiss is closed on all sides, save for a small viewing aperture in one side, where you can look at the screen. This boosts contrast phenomenally and allow very high magnifications to be used, resulting in some amazing images. Faculae are extremely spectacular with this setup.

One side of the box can be opened to allow changing eyepieces. It was otherwise a very unassuming cardboard box, not very pretty at all. It was meant to be a prototype, just to see if it worked, but it worked so well, I never did get around to make a more finished version.

C'est la vie.


Clear skies!
Thomas, Denmark

#17 starman876

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Posted 12 February 2013 - 07:12 PM

really nice set up Terra. Great pics with the I phone

#18 bremms

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Posted 12 February 2013 - 07:42 PM

Nice solar set up. Really forgot how fun solar observing can be.
Remember to use a Huygens or Ramsden for projection. I melted and bubbled the balsam in a shiny new 25mm VT ortho with my 6" F8 back in about 77 or so. Sucked since I save d up to buy that eyepiece.

#19 terraclarke

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Posted 12 February 2013 - 08:50 PM

Yup, that's a good reminder Marc. I always use old all metal Huygens eyepieces for projection. I have a couple of old microscope eps 10x, 15x, and 25x that work great. 10x=25mm, 25x=10mm work splendidly. Mine are all metal and are the larger size 23mm dia so are only slightly smaller than 0.965 inch. I made up the difference by making a thin collar out of an old Charley's cologne cap. Old 0.965 Japanese all metal barlows also work as they are single element, no cement.

#20 Astrojensen

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Posted 13 February 2013 - 03:54 AM

I've used orthoscopics for solar projection on my 85mm Zeiss for years without ever damaging one of them. They did get pretty dang hot now and then. I did melt a plastic barrel huygenian once...

Old 0.965 Japanese all metal barlows also work as they are single element, no cement.


Are you sure? I've never seen a single element barlow. Wouldn't that cause terrible color error?


Clear skies!
Thomas, Denmark

#21 R Botero

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Posted 13 February 2013 - 06:32 AM

Hi Terra

Very nice. Thank you for posting all this. I am having an adaptor made to fit my 60mm double-stacked (0.5A) Coronado etalon to the front cell of my 75mm Polarex. It should be ready within the next couple of weeks - just in time for the sun to start clearing the roof of my house at all daylight hours...!
I use a Baader Herschel wedge also but plan to keep it attached to my 6" AP instead of the Polarex. I'm very much looking forward to the native f/20 solar views on the Polarex!! :jump: Imagine adding a barlow to that...let's not get too excited there's the seeing to take into account... :p

Roberto

#22 starman876

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Posted 13 February 2013 - 11:38 AM

Do not forget the ARMY used multiple mirrors to focus the suns rays to melt steel. I would never use a scope without a solar filter on the front. I looks at it like being one photon away from having the sun come out the back of my head.






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