Jump to content


Photo

Double Stacked Coronado PST question

  • Please log in to reply
7 replies to this topic

#1 domsel

domsel

    Lift Off

  • -----
  • Posts: 2
  • Joined: 03 Aug 2011

Posted 26 October 2011 - 05:11 AM

Hello all,

I've been using my PST for solar observing for some time and with the upcoming maximum decided to add a double stack to the tube. However, after following the installation and tuning to the letter, I can't say the level of detail has much improved, if at all. Should adding the double stack be a significant improvement or was I simply too optimistic?

Could there be something wrong with the SM40, or am I doing something wrong?

Thanks for your help and suggestions,

Matt

#2 Montana

Montana

    Soyuz

  • -----
  • Posts: 3654
  • Joined: 02 Jan 2010
  • Loc: Cheshire, UK

Posted 26 October 2011 - 06:52 AM

Hi Matt, I have just recently double stacked my PST and the effect blew me away. This should be a huge improvement on the single stack. I was instructed by Old Dinosaur and he was spot on. Tune your PST to maximize surface filament and prominence detail. Then close your double stack all the way in as far as it will go, then screw it on the front. Then slowly turn the wheel until you see spectacular results. Mine however is on band right at the closed point, I have no room for adjustment. I think all of them vary and the critical point is very small so don't miss it. I hope that your point is not outside the tunable region, it scared me that mine was right on the closed point.

Here is a picture I took of the same active area single stack: http://www.flickr.co...tream/lightbox/

and double stacked:
http://www.flickr.co...tream/lightbox/

You should see hundreds more filaments than you saw before and quite dark with very bright active areas which aren't apparent with single stack, and more filaproms too.

http://www.flickr.co...tream/lightbox/

Good luck, I hope this helps a bit.

Regards
Alexandra

#3 domsel

domsel

    Lift Off

  • -----
  • Posts: 2
  • Joined: 03 Aug 2011

Posted 26 October 2011 - 07:41 AM

Alexandra,

Thanks for your quick reply. As soon as it clears up, I'll give it another try.

Thanks again,

Matt

#4 Bill Cowles

Bill Cowles

    MacGyver

  • *****
  • Posts: 2855
  • Joined: 16 Apr 2006
  • Loc: Utah

Posted 26 October 2011 - 12:23 PM

I'm with Montana, the stacked PST is so much better than without the extra filter, never view without it. We have many non stacked PST's in our club, and comparing the difference, is night and day. I have since upgraded to a Lunt 60 and I only view stacked. Both scopes show just more surface detail but the contrast is so much greater, no red hazy background, just a nice black background.

Bill

#5 Dave n San Diego

Dave n San Diego

    Lift Off

  • -----
  • Posts: 2
  • Joined: 07 Apr 2012
  • Loc: California

Posted 26 January 2013 - 07:03 PM

Is double stacking something I can do myself? I have a standard PST. Can I just order the second filter and thread it on myself? If it is that easy, does anyone know where I can order the filter?
Thanks,
Dave

http://cleardarksky....ObsObCAkey.html

#6 RandallK

RandallK

    Surveyor 1

  • -----
  • Posts: 1768
  • Joined: 10 Nov 2006
  • Loc: Nanaimo, B. C. Canada

Posted 26 January 2013 - 11:23 PM

Yes you simply thread it on to the PST. You don't have to send it away to have it matched up. I got mine from Canadian Telescopes who drop ships most of their line from Woodland Hills Telescopes.

http://woodlandhillstelescopes.com/



#7 Dave n San Diego

Dave n San Diego

    Lift Off

  • -----
  • Posts: 2
  • Joined: 07 Apr 2012
  • Loc: California

Posted 27 January 2013 - 03:00 AM

Perfect! Thank you

#8 BYoesle

BYoesle

    Aurora

  • *****
  • Posts: 4963
  • Joined: 12 Jun 2004
  • Loc: Goldendale, Washington USA

Posted 27 January 2013 - 09:19 AM

Could there be something wrong with the SM40, or am I doing something wrong?


You should first tune the internal (single stack) PST etalon for maximum contrast inside the "sweet spot". Then add the second external filter and tilt it only far enough to get rid of any secondary reflections from covering the suns disk and nearby prominences. If you tilt the second filter too much, it will be so far off-band as to only be passing continuum light, and there will be no benefit to double stacking.

A recent thread demonstrating the qualitative and quantitative benefits of double stacking can be found here:

http://www.cloudynig...5587193/page...

Another DS thread including the suitability of "off-the-shelf" DS filters can be found here:

http://www.cloudynig...3190784/Main...

Mine however is on band right at the closed point, I have no room for adjustment. I think all of them vary and the critical point is very small so don't miss it. I hope that your point is not outside the tunable region, it scared me that mine was right on the closed point.


Most "normal" filters are designed to be on-band when fully closed at sea level, and tilting would generally be needed if one were to observe at significantly higher altitudes.

There are no "factory matched" DS filters for the PST. For DSing other scopes, the second filter might be intentionally designed to perfrom better when tilted slightly for the purpose of double stacking, but many have found that "normal" filters perform just as well for the purpose, even though they go slightly off-band when tilted.








Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics