Search found 640 matches

by Bob Yoesle
Thu May 10, 2012 4:19 am
Forum: Solar Scope Modifications
Topic: Large Aperture Solar Telescope Using Double Stacked Coronado Etalons.
Replies: 42
Views: 4122

Re: Large Aperture Solar Telescope Using Double Stacked Coronado Etalons.

Well sort of, but not exactly. The collimator lens is a 100/900 = f9, but the etalon it is feeding a collimated (unfocused & no f ratio) "beam" to is 90 mm in diameter. Therefore, the effective diameter of the collimator is 90 mm, and the focal ratio will be 90/900 = f10, which is then perfect for u...
by Bob Yoesle
Thu May 03, 2012 5:30 pm
Forum: Solar Scope Modifications
Topic: Large Aperture Solar Telescope Using Double Stacked Coronado Etalons.
Replies: 42
Views: 4122

Re: Large Aperture Solar Telescope Using Double Stacked Coronado Etalons.

Thanks guys - I definately will be keeping you up to speed as this project moves along. Hi Rusty, that's the ISTAR "counter cell" - it's designed for mounting the lens cell to the telescope tube with push-pull bolts, and it's MASSIVE! The lens itself is beautifully AR multicoated, and the lens comes...
by Bob Yoesle
Wed May 02, 2012 7:35 pm
Forum: Solar Scope Modifications
Topic: Large Aperture Solar Telescope Using Double Stacked Coronado Etalons.
Replies: 42
Views: 4122

Large Aperture Solar Telescope Using Double Stacked Coronado Etalons.

My experimental quest for a large(r) aperture H alpha solar telescope with good full-disk capability is taking shape. A number of factors must be addressed with internal etalons if one is to achieve optimal full-disk performance. Primarily this is directed an minimizing the increase in field angles ...
by Bob Yoesle
Mon Apr 30, 2012 6:04 pm
Forum: Solar Scope Modifications
Topic: Large Aperture solar telescope using a modded Lunt etalon?
Replies: 171
Views: 11522

Re: Large Aperture solar telescope using a modded Lunt etalon?

Haven't seen a site actually describing the scope. The ideal system would be to use a collimator lens feeding a “collimated” beam to the LS60. The collimator would ideally be a simple achromat of 60 mm diameter and 600 mm FL (e.g. f/10 to match the primary objective), which it appears there would be...
by Bob Yoesle
Mon Apr 30, 2012 4:03 pm
Forum: Solar Scope Modifications
Topic: Large Aperture solar telescope using a modded Lunt etalon?
Replies: 171
Views: 11522

Re: Large Aperture solar telescope using a modded Lunt etalon?

Hi Merlin. I believe Markus is stating that the collimator lens acts a the second element of an achromatic doublet to correct some spherical abberation from the singlet objective, as well as to collimate the light comming from the singlet objective. He appears to be stating that the collimation lens...
by Bob Yoesle
Sun Apr 29, 2012 5:07 pm
Forum: Solar Scope Modifications
Topic: PST CaK modification
Replies: 22
Views: 1494

Re: PST CaK modification

This post should get you going in the right direction:

http://solarchat.natca.net/index.php/en ... dification

Feel free to ask if there is additional information you need.
by Bob Yoesle
Sat Apr 28, 2012 5:19 am
Forum: Solar Scope Modifications
Topic: Would mirrors affect Ha imaging?
Replies: 12
Views: 1422

Re: Would mirrors affect Ha imaging?

Hi Ian, I met with Spectral Joe this week and he has an incredible spectrohelioscope fed by a coelostat: http://www.cloudynights.com/ubbthreads/showflat.php?Cat=&Board=solar&Number=4422708&Forum= The coelostat itself is controlled by a tracking system like you’re describing. OTOH, an equatorial moun...
by Bob Yoesle
Fri Apr 27, 2012 10:55 pm
Forum: Solar Scope Modifications
Topic: Large Aperture solar telescope using a modded Lunt etalon?
Replies: 171
Views: 11522

Re: Large Aperture solar telescope using a modded Lunt etalon?

The f ratio of the collimator lens (at the aperture of the etalon) will affect whether the the etalon/collimator acts as a field stop - i.e vignetting is the main issue here. The actual performance of the etalon regarding the bandpass is based on the focal length of the of the ojective divided by th...
by Bob Yoesle
Thu Apr 26, 2012 12:36 pm
Forum: Solar Scope Modifications
Topic: Blocking Filter, Mini ERFs and Alternatives
Replies: 176
Views: 22869

Re: Blocking Filter, Mini ERFs and Alternatives

Bob, what are you going to use instead of the KG5? Hi Etat, First, if I had a failed ITF, I'd get it replaced with another ITF, as they are relatively cheap. And this is BY FAR the safest route to take in protecting ones eyesight from far IR... I would only consider alternatives for imaging - not vi...
by Bob Yoesle
Thu Apr 26, 2012 3:39 am
Forum: Solar Scope Modifications
Topic: Cak filter modification
Replies: 16
Views: 1222

Re: Cak filter modification

I have left mine in the original assembly and have not teken the filters out: First; there has been no need. Second; the filters themselves are likely "clocked" or tilted with respect to each other in an optimum configuration to avoid internal reflections, and this might be diffcult to re-establish ...
by Bob Yoesle
Sat Apr 21, 2012 2:22 pm
Forum: Solar Scope Modifications
Topic: Cak filter modification
Replies: 16
Views: 1222

Re: Cak filter modification

Hi Rob, Actually no, I don't advise using the PST body or it's blocking filter, as the pentaprism focusing mechanism is prone to sagging and hence producing astigmatism, and the BF is tiny. If I had both a PST and a Lunt CaK, I would use the PST's main filter assembly within the Lunt module to doubl...
by Bob Yoesle
Wed Apr 18, 2012 4:19 am
Forum: Solar Scope Modifications
Topic: Cak filter modification
Replies: 16
Views: 1222

Re: Cak filter modification

...are the distances between filters critical in the CaK module? I noticed that your illustration shows quite a long 2" tube.... Hi Pete, The PST CaK filter(s) are rather small, and you want these to be as near to the imaging device as possible to avoid vignetting. The Baader CaK needs to be just be...
by Bob Yoesle
Mon Apr 16, 2012 10:44 pm
Forum: Solar Scope Modifications
Topic: Cak filter modification
Replies: 16
Views: 1222

Re: Cak filter modification

Hi Pete,

I use a semi-APO ED100 doublet - the results are as seen above. A triplet would probably be even better corrected for SA in the violet/near-UV, if you can afford it.
by Bob Yoesle
Mon Apr 16, 2012 5:37 pm
Forum: Solar Scope Modifications
Topic: Cak filter modification
Replies: 16
Views: 1222

Re: Cak filter modification

Hi Pete, As Mark states, yes, this PST CaK mod works very well for imaging. Even if I could see CaK - which I can barely make out with a great deal of effort - I wouldn't trust this for visual observation. IT THEREFORE IS ONLY SUITABLE FOR IMAGING. That being said, I believe Mark and I, who learned ...
by Bob Yoesle
Mon Apr 16, 2012 2:31 am
Forum: Solar Scope Modifications
Topic: Cak filter modification
Replies: 16
Views: 1222

Re: Cak filter modification

Hi Robert, You could use your existing PST filter and the Baader CaK filter to make a stand-alone CaK module, just add a Baader Blue CCD filter to the front for an ERF: To get to the PST CaK primary filter, unscrew the gold OTA/objective tube from the main body, and then unscrew the main filter asse...
by Bob Yoesle
Mon Apr 16, 2012 1:58 am
Forum: Solar Scope Modifications
Topic: Blocking Filter, Mini ERFs and Alternatives
Replies: 176
Views: 22869

Re: Blocking Filter, Mini ERFs and Alternatives

Bob you have any luck finding a 1/10 KG-5 filter? Yes, I have a quote for two 47 mm diameter KG5 filters to ~ 1/10 lambda for $1500.00 USD. At this point I'm still waiting for a coating quote for UV blocking, as KG glass is stated to have "transmission changes" with "intense UV" as could be expected...
by Bob Yoesle
Fri Apr 06, 2012 3:05 pm
Forum: Solar Scope Modifications
Topic: Blocking Filter, Mini ERFs and Alternatives
Replies: 176
Views: 22869

Re: Blocking Filter, Mini ERFs and Alternatives

I'm nearing completion of my new Ha blocking filter and CaK modules, which will be evacuated and filled with Nitrogen. These are essentially identical units with a sealed inner chamber intended to remove moisture from the primary filter elements and keep thermal stresses to a minimum. Therefore I'm ...
by Bob Yoesle
Sat Mar 24, 2012 1:58 am
Forum: Solar Scope Modifications
Topic: Telecentric Lens Systems
Replies: 21
Views: 2033

Re: Telecentric Lens Systems

Rusty - That was my thought as well! But you better hurry, I understand from somewhere Lunt may soon no longer offer the LS35, or at least the DS filter... Should be an interesting project!

Collin - I have the book and software somewhere as well - probably burried in the garage!
by Bob Yoesle
Tue Mar 20, 2012 5:51 am
Forum: Solar Scope Modifications
Topic: Telecentric Lens Systems
Replies: 21
Views: 2033

Re: Telecentric Lens Systems

Hi Colin, Here's an interesting telecentric design using off-the-shelf optics from Edmund Optical I found on Peter Hobel's German site (with all his filter transmission graphs): http://translate.google.com/translate?hl=en&ie=UTF8&prev=_t&rurl=translate.google.com&sl=de&tl=en&u=http://www.sonnen-filt...
by Bob Yoesle
Mon Mar 19, 2012 5:01 am
Forum: Solar Scope Modifications
Topic: Blocking Filter, Mini ERFs and Alternatives
Replies: 176
Views: 22869

Re: Blocking Filter, Mini ERFs and Alternatives

“The figures I quote are for 8 hours per day occupational exposures. I choose them for the obsessed of us.” Actually Collin, I’m not sure I would trust even these exposure levels, as in my experience with sound levels, OSHA 8 hour tolerances (90 dBA) can an do result in hearing loss. And as with any...
by Bob Yoesle
Sat Mar 17, 2012 3:02 pm
Forum: Solar Scope Modifications
Topic: Blocking Filter, Mini ERFs and Alternatives
Replies: 176
Views: 22869

Re: Blocking Filter, Mini ERFs and Alternatives

Makes sense that a thicker absorption filter would have a decreased transmission, but I would like to verify this. Then there would be the possibility of “double stacking” (!). BTW Edmund offers the KG 5 in 3 mm thickness, as opposed to the 2 mm shown in the graphs above. Whatever Lunt appears to be...
by Bob Yoesle
Sat Mar 17, 2012 12:36 am
Forum: Solar Scope Modifications
Topic: Blocking Filter, Mini ERFs and Alternatives
Replies: 176
Views: 22869

Re: Blocking Filter, Mini ERFs and Alternatives

Thanks for that info Colin, which argues even more strongly against using wide-band Ha filters alone as an IR blocker for solar use. Going by your stated ND values, a KG 1 appears to be unsuitable for IR blocking (and exceeds the EU standards shown above): The KG 3 appears to be better: Although it ...
by Bob Yoesle
Fri Mar 16, 2012 6:19 pm
Forum: Solar Scope Modifications
Topic: Blocking Filter, Mini ERFs and Alternatives
Replies: 176
Views: 22869

Re: Blocking Filter, Mini ERFs and Alternatives

Most of the “traditional” dielectric filters appear to have higher transmissions above 1200-1400 nm. That is why metallic silver is incorporated in to the ITF’s layers for IR blocking solar applications. I believe it is much better to be conservative and have something that performs as well as the o...
by Bob Yoesle
Fri Mar 16, 2012 3:22 am
Forum: Solar Scope Modifications
Topic: Blocking Filter, Mini ERFs and Alternatives
Replies: 176
Views: 22869

Re: Blocking Filter, Mini ERFs and Alternatives

This site is the source of most of the solar filter transmission curves posted here, and has some references to the German/EU standards: http://www.sonnen-filter.de/

Translated - “EU standards, guidelines and recommendations presented in graphical form”:


by Bob Yoesle
Fri Mar 16, 2012 1:22 am
Forum: Solar Scope Modifications
Topic: Blocking Filter, Mini ERFs and Alternatives
Replies: 176
Views: 22869

Re: Blocking Filter, Mini ERFs and Alternatives

Hi Colin,

I agree completely that a DERF is not adequate by itself, but for far IR blocking the KG glasses look to be a possible alternative to an ITF as shown in their transmission blocking out to 2500 nm. Lunt appears to have gone this route as well, as noted above.