Jump to content


Photo

DayStar T-Scanner Filters

  • Please log in to reply
15 replies to this topic

#1 MAURITS

MAURITS

    Apollo

  • -----
  • Posts: 1018
  • Joined: 22 Sep 2009
  • Loc: Belgium

Posted 21 November 2012 - 04:16 AM

Is it a good idea to use the "DayStar T-Scanner Filters" for observing the sun in Ha in combination with the TOA-150mm?

Can I use it with the full scope aperture?

Are there drawbacks to this system?

Thanks! :waytogo:

#2 drksky

drksky

    Surveyor 1

  • *****
  • Posts: 1760
  • Joined: 31 Aug 2009
  • Loc: Bloomington, IL

Posted 21 November 2012 - 06:49 AM

Daystar states that their filters work best at f/30, so if you wanted to use is with a TOA150, you'll need a 5X powermate. With a proper ERF, Daystars can be used on just about any scope.

The T-Scanners are no longer available new, so unless you're buying used, you need to get one of the new ION filters.

I don't know of ant disadvantages, but you can get a .3A filter for a seemingly reasonably price compared with the Quantum SE line.

#3 MAURITS

MAURITS

    Apollo

  • -----
  • Posts: 1018
  • Joined: 22 Sep 2009
  • Loc: Belgium

Posted 21 November 2012 - 06:59 AM

Thanks Tony for the information!

#4 David Knisely

David Knisely

    Hubble

  • *****
  • Posts: 15452
  • Joined: 19 Apr 2004
  • Loc: southeastern Nebraska

Posted 21 November 2012 - 11:39 PM

Daystar states that their filters work best at f/30, so if you wanted to use is with a TOA150, you'll need a 5X powermate. With a proper ERF, Daystars can be used on just about any scope.

The T-Scanners are no longer available new, so unless you're buying used, you need to get one of the new ION filters.

I don't know of ant disadvantages, but you can get a .3A filter for a seemingly reasonably price compared with the Quantum SE line.


The problem with using the 5x Powermate is that, unlike the 2x, 2.5x, and 4x models, the 5x Powermate is not quite telescentric. Using it to get to f/30 or beyond will result in the dreaded "sweet spot" or "ring" effect, making the portion of the field of view that is within the passband of the filter to cover notably less than the entire field of view. I had the idea of using the 5x Powermate on my 100mm f/6 refractor, but I got the same "ring" effect that I had gotten when I used a regular Barlow. If you want full-field H-alpha, you need to use either a fully telecentric system or one that is intrinsically f/30. Clear skies to you.

#5 sullij1

sullij1

    Surveyor 1

  • -----
  • Posts: 1600
  • Joined: 08 Nov 2008

Posted 21 November 2012 - 11:55 PM

Right on both counts, ERF, Powermates up tp 4X or Baader telecentrics Here:
http://www.alpineast...tric System.pdf
This may be of interest to you also:
http://www.leif.org/...ar_showdown.pdf

#6 MAURITS

MAURITS

    Apollo

  • -----
  • Posts: 1018
  • Joined: 22 Sep 2009
  • Loc: Belgium

Posted 22 November 2012 - 01:47 AM

Thanks David and sullij1 for the info and the link!

#7 drksky

drksky

    Surveyor 1

  • *****
  • Posts: 1760
  • Joined: 31 Aug 2009
  • Loc: Bloomington, IL

Posted 22 November 2012 - 06:41 AM

sullij1 I glanced at that PDF of the shootout and one thing struck me. Should the powermate be behind the filter and not in front of it??

#8 sullij1

sullij1

    Surveyor 1

  • -----
  • Posts: 1600
  • Joined: 08 Nov 2008

Posted 22 November 2012 - 02:29 PM

In front of the T-scanner, it is the powermate that takes the function of the Baader telecentric. That's why you want the 2X - 4X as their optics are telecentric. Telvue states this in their Powermate advertising. As I understand it, this was "one" of Al Naglers considerations when the Powermates were first developed.

Also why (as you can see in the shoot out) the 5 X performed worse. It's not telecentric.

If you are using a T scanner and dont use a Powermate, in addition to the ERF you would also need a iris on the objective to stop down the apature, until you increased the focal ratio to required F30. F30 provides a near telecentric beam. This information also is burried someplace in Daystars website.

#9 marktownley

marktownley

    Cosmos

  • -----
  • Posts: 8581
  • Joined: 19 Aug 2008
  • Loc: West Midlands, UK

Posted 23 November 2012 - 02:15 AM

You need to consider your local seeing consitions - ask yourself how often you will be able to use a 150mm aperture at 4500mm fl in the dfaytime...

I know where I am this is something I have never been able to do...

#10 Gary BEAL

Gary BEAL

    Surveyor 1

  • *****
  • Posts: 1559
  • Joined: 10 May 2003
  • Loc: New Zealand

Posted 23 November 2012 - 04:49 AM

I agree with Mark, in my case most of my solar imaging is done at 840mm, and very occasionally I can slip the 2.5x PowerMate on, not often though.
Gary

#11 BYoesle

BYoesle

    Aurora

  • *****
  • Posts: 4862
  • Joined: 12 Jun 2004
  • Loc: Goldendale, Washington USA

Posted 27 November 2012 - 01:09 AM

The long focal lengths noted previously can be somewhat ameliorated by using a focal reducer just after the filter. The new SolaREDi80 comes with a 0.5 x reducer diagonal for this purpose. See: http://www.daystarfi...olaREDi80.shtml DayStar’s new Skylight 100 ( http://www.daystarfi...ylight100.shtml ) could also benefit from this approach.

Also of note is that telecentric performance is dependent on being matched to the focal length of the objective for optimum performance. This is the same as for internal etalons using collimators - which must be designed specifically for the objective they are paired with to obtain optimum performance over an angular field covering the suns disk or larger. With the longer focal lengths (narrow fields) this may be irrelevant, but for optimum performance at shorter EFL’s, a custom made telecentric tailored to the objectives focal length would be required. See Gene Baraff’s thorough article on telecentrics here: http://home.comcast....erving/Tele.pdf

I’m not sure what focal length would be optimum for the TeleVue Powermates, but I believe the Baader telecentrics were originally designed for use with a 150 f/8 objective, and therefore would be optimized for a focal length of 1200 mm.

Another option might be to situate the DayStar and Solar Specturm type filters within a collimator optical system. Focal lengths might be more manageable this way, as well as that collimators can be more easily optimized for a specific focal length. With the advantages of these filters being the ability to get FWHM bndpasses below 0.5 angstroms, Lunt has indicated it is working on just such a rear-mounted filter system design using collimators...

#12 MAURITS

MAURITS

    Apollo

  • -----
  • Posts: 1018
  • Joined: 22 Sep 2009
  • Loc: Belgium

Posted 28 November 2012 - 01:41 PM

Thanks all for the great comments!

#13 markthais

markthais

    Vostok 1

  • -----
  • Posts: 140
  • Joined: 25 Jun 2004

Posted 29 November 2012 - 09:01 PM

Your question about using the TOA150. You would be better off stopping it down to F/8 and use an 4X Powermate or Baader TZ4.
The filter doesn't care what the size of the scope is. That is only if you want to see a full disk.
It's a good idea to use a good red glass(1/4 wave on transmission)for the ERF. If it is going to be 3" or larger make sure it is at least 1/4" thick.
The next important information is where the bandpass wavelength is at the temperature your using it at. The wavelength moves with temperature(about 1 ang per 10C) and most of them are 1 ang red at 25C but it could be on band at 25C just as easy.
To tell where your at,put it on the scope, if you can see improvement by turning the knob you are red of Ha. The maximum tuning adjustment is 1/8 of a turn any more that that the filter will be very broad or you are adjusting for misalignment.
The other information is that the bandwidth of the filter on the label is only when it is not tilted. So if the filter says .5Ang that is only if the filter is not tilted. Any tilting of the filter broadens out the bandwidth quickly, this is the same with all etalons. An air spaced etalon would broaden even faster with tilt. So this point is the same with all etalons.
The last bit of information is that the narrower the bandwidth the smaller the window of temperature it works well.
This is not to say that a T-Scanner won't work but you may find that it will work better sometimes and not so well others. I hope this gives you an understanding on how to get the most out of your T-Scanner.
Mark W.

#14 sullij1

sullij1

    Surveyor 1

  • -----
  • Posts: 1600
  • Joined: 08 Nov 2008

Posted 29 November 2012 - 11:22 PM

There ya go. Right from the guy who probably put the thing together. ;)

#15 MAURITS

MAURITS

    Apollo

  • -----
  • Posts: 1018
  • Joined: 22 Sep 2009
  • Loc: Belgium

Posted 30 November 2012 - 07:15 AM

That's a good opinion Mark!

#16 BYoesle

BYoesle

    Aurora

  • *****
  • Posts: 4862
  • Joined: 12 Jun 2004
  • Loc: Goldendale, Washington USA

Posted 30 November 2012 - 09:20 PM

Elaborating on what Mark notes above, if it were me (I used a DayStar system for almost 30 years), I would opt for a full aperture ERF with heat reflecting dielectric coatings - available form Lunt or Baader. These will help to reduce thermal loading and prolong the H alpha filter’s lifetime. The largest available from Lunt is 100 mm; Baader’s are available to over 160 mm. Less expensively, you could use a plain red glass ERF of suitable quality, and use a Baader Red dielectric CCD filter or IR/UV filter for protecting the Ha filter itself from IR.

Full disk views of the sun would be best by stopping down the aperture of your TOA 150 to 36 mm @ f30. Alternatively, go to 73 mm and use a 2 x Powermate or Baader TZ2 Telecnetric. This will give you an EFL of ~ 2000 mm, and you can manage a full- disk view with a suitable long focal length eyepiece. For times when the atmosphere permits, you could use the full aperture with a 4 x Powermate or Baader TZ4 Telecentric for higher magnification purposes. And again, you can use a focal reducer after the filter to get a more manageable EFL...

By the way, DayStar no longer makes the T-scanner; the ION series has replaced it, and eliminates the need to tilt the filter for tuning. T-scanner filters can also be upgraded to the ION specification: http://www.daystarfi...m/ION/ION.shtml






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics