Sweet spot, banding and tilted etalons ...where are the limits ?

Frankenscope? Let's see it!***be advised that NOTHING in this forum has been safety tested and you are reading and using these posts at your own peril. blah, blah, blah... dont mess around with your eyesight when it comes to solar astronomy. Use appropriate filtration at all times...
User avatar
MapleRidge
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 10199
Joined: Fri Jan 13, 2012 11:58 pm
Location: Cambray, ON Canada
Has thanked: 64 times
Been thanked: 4340 times
Contact:

Re: Sweet spot, banding and tilted etalons ...where are the limits ?

Post by MapleRidge »

Hi Christian...

Thanks for the completed math on the calculations.

I had always though the 'sweet spot' on my mod was less than optimum since the etalon/collimators are designed for a f7 scope, but I have it on a f8 OTA.

My original mod with this etalon was on a 100mm, f10 scope and I think the sweet spot increased as the focal ration move closer to what it was designed for. When I run the math on the 100mm scope it shows the radius is smaller, close to 0.16 deg by my math.

Brian


Brian Colville

Maple Ridge Observatory
Cambray, ON Canada

Photos: https://www.flickr.com/photos/185395281@N08/albums

10'x15 Roll-off Roof Observatory
Takahashi EM400 Mount carrying:
C14 + Lunt 80ED
Deep Sky Work - ASI294MM Pro+EFW 7x36/Canon 60D (Ha mod), ONAG
Planetary Work - SBIG CFW10, ASI462MM

2.2m Diameter Dome
iOptron CEM70G Mount carrying:
Orion EON 130ED, f7 OTA for Day & Night Use
Ha Setup: Lunt LS80PT/LS75FHa/B1200Ha + Home Brew Lunt Double Stack/B1800Ha on the Orion OTA + Daystar Quantum
WL, G-Band & CaK Setup: Lunt Wedge & Lunt B1800CaK, Baader K-Line and Altair 2nm G-Band filter
ASI1600MM, ASI432MM, ASI294MM Pro, ASI174MM, ASI462MM
LeoD
Im an EXPERT!
Im an EXPERT!
Posts: 395
Joined: Mon May 04, 2020 2:21 pm
Location: Moscow, Russia
Has thanked: 1262 times
Been thanked: 1057 times
Contact:

Re: Sweet spot, banding and tilted etalons ...where are the limits ?

Post by LeoD »

Very informative thread!
christian viladrich wrote: Mon Mar 01, 2021 1:15 pm BTW, there is also a possible combinaison with a double stack Lunt 80 mm internal etalon. I don't remember what is the actual diameter of this etalon.
The Lunt LS80MT has 51mm tilted internal red ERF in front of 45mm clear aperture etalon and DSII-SFPT module of 36mm c.a., joint next to it.
The same as Marty, I'm curious to pair the Lunt, in my case DS rear system, with a bigger frac f/7. Seems promising, though.
With my given 130/7 according to Christian's formula, I have 0.34° diameter of the 'sweet spot' i.e. 2/3 of the disk.
How to calculate a lens in front of the etalon? with detached native collimation lens or as it is?

Leo


christian viladrich
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 2150
Joined: Sun Jun 14, 2015 4:46 pm
Location: France
Has thanked: 1 time
Been thanked: 2713 times
Contact:

Re: Sweet spot, banding and tilted etalons ...where are the limits ?

Post by christian viladrich »

I think George9 on Cloudy Night Forum has a double stack configuration with his 155 mm Astrophysics. I am pretty sure he has at least one Lunt 80 mm etalon, but I don't remenber whether the other etalon is another Lunt 80 mm or a Quark.
I don't remember if George9 is also on SolarChat ?


Christian Viladrich
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
christian viladrich
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 2150
Joined: Sun Jun 14, 2015 4:46 pm
Location: France
Has thanked: 1 time
Been thanked: 2713 times
Contact:

Re: Sweet spot, banding and tilted etalons ...where are the limits ?

Post by christian viladrich »

Here is an example of double stack Lunt 80 mm on a 204 mm refractor :
http://www.astrosurf.com/topic/144876-s ... m-h-alpha/


Christian Viladrich
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
Post Reply