Investigation on a solar instrument Simon de Visscher image: heart nebula (CAS) by M. Haase 1
A quick reminder: sun layers 2
Observing the photosphere Simplest: Reflector Astrosolar, glass Refractor: Astrosolar, glass, helioscope Perf: Astrosolar~Helioscope>glass CHF: Helioscope>glass>astrosolar 3
Astro-solar on a C14 4
H-alpha Much more complicated situation 5
Two different types of targets to consider What is in front of the photosphere Enemy N 1: light from photosphere What is NOT in front of the photosphere Enemy N 1: photosphere light diffusion in the sky and optics. 6
Case 1: the disk Lumi H alpha Kill the background, keep the signal! Bandwith (B) smaller than 1Angström (!): disk constrast depends directly on B! Is the smallest B the best for the disk? Not always: dependency to Doppler- Fizeau effect increases as B decreases. Need to find a compromise... Also: price increases as B decreases (we ll come back to this later) 7
Case II: eruptions Difference w.r.t. case I: no photosphere behind: most of background results from diffusion in atmosphere and optics Larger bandwidth than for the disk If too large, backgrounds kill the contrast + no detail visible on the disk at all (because of the photosphere) If too small: D-F effect, eruptions are too faint. Let s see now how to filter in practice!! 8
Key elements of Halpha scopes 9
Fabry-Perot (FP) Interferometer (solid/air) that creates constructive or destructive interference depending on the light wavelength Peaks can be very narrow (smaller than 1 A)...but resonance peaks (harmonics) are present as well (n*wavelength disphasing). Add a blocking filter (BF) behind to keep only one peak. Sounds nice but two problems slow degradation of the FP surfaces with the time costs a lot!!! 50mm (B=0.75 A)~2500 euros 100mm (B=0.75 A)~9000 euros... 10
FP Frequency tuning!"#$%&! '()*+,*+-#$#.*! /#01#2$*+! 3%0%&#,%+ "#$%&!! 4%$#05#6+"()*+7! 3%0%&#,%+ 4%$#05#6+"()*+77! "#$%&!&'! ()*+,,&-.! /+%'!0!12#'.*+#'&! 3(1*#+4-&!,-.! -#&!5&,!6*1&,! 89&"+:0%&"#$! "#$%&!! 89&"+1&"*0&*+ ;+)0*<<90*+ "9&*0+=! 7)*+,,&-.! 5*#,!%*!1*8+'(! >4'! "#$%&!!?#(<"#0+*"+4%$#0+ 7)*+,,&-.! /&3)(.*'-.&!5-! 4)*-"095! 3+1*! 11
Double stack Superimpose two FP with a slightly different bandwidth Transmittance Transmittance Transmittance 12
ERF 13
Classical combinations 14
PST FP-T-BF FP-FP-T-BF 15
ERF-T-TC-Ha-BF (Daystar,...) ERF-SC-TC-Ha-BF HaT ERF-T(FP)-BF (Lunt) 16
PST "#$%&!'&!()#&!!! "#$%&!'&!(*+,-!!!!!!"! #" Doublet 40/400 ERF Lentille divergente Lentille convergente Filtre HA 6A Etalon Pentaprisme!"#$%&'(")*+,%'(!!!"#$!! %"!&!"'()*+,!$!&!"'()*+!*+-./**+!-01)./2+3! 45*+!'$!.6578!&!!! #'#(# -./&'(0+#'1*'%#( (!"#$"%&'()"!*+!,-+! +./0!!"#$"%&'()"!-++!,-+! -.10!!"#$"%&'()"!!-/+!,-+! 0!!"#$"%&'()"!2++!,-+! 2.*0! 345!2+166! 2.70! #'#()*+#,#()-*+# # Need to reimplement the Lunt system...or use a telecentric one 17
Little summary Solution à-la-coronado FP BF Nice solution but...costs a lot! since D(FP)~D(instrument) Solution à-la-lunt/daystar/pst Instead of putting the FP at the front, put it at the back Two issues: a) FP works with almost parallel incoming lightrays Need to add a telecentric system (TC) b) Need an additional filter at the front, called Energy Rejection Filter (ERF) ERF costs much less than a FP (~1300 euros for d=160mm) TC BF FP 18
Commercial products 19
Coronado FP FP BF 20
Lunt ERF FP BF 21
Daystar Quantum filters 0.3 to 0.8 A SE/PE grade (homogeneity of the field) SE: from 3568 to 11500 euros PE: from 5894 to 17840 euros Thermally controlled Other models available, with different characteristics (diameter, easyness of use, etc...) 22
TC FP+BF ERF-telescope-TC-FP-BF Front lens ERF 23
230 Ref J-P-Brahic 24
230 ref J-P-Brahic 25
ERF-telescope-TC-FP-BF 26
F.Jabet 27
L.Cauvra 28
Coronagraph Clever design, used to observe solely the solar eruptions Remove the diffusion from the front element using a diaphram and two additional lenses Very few brands propose these solutions for amateurs BelOptik (DE): ~1000 euros Baader Other solution: do it yourself...but not a solution for a club! 29
BelOptik Coronagraph solution!"#$%&'"%"(")%$*+!"#$%&'($)*+,$-+./$!0.1 30
P.Tosi (H-M coro) 31
P.Tosi (H-M coro) 32
What do we want? Visual and imagery Diameter? Yes, it matters below 60: quite small, especially in double stack! above 150mm, most probably useless because of the seeing Money-aside (hum...), between 100 and 150 would be nice! FP-telescope-BF: expensive, out-of-the-box working solutions ERF-telescope-TC-FP-BF: less expensive (for a given diameter), but more demanding in terms of mechanics, almost nothing outof-the-box (see Hat) Coronagraph: Commercial solution should be fine home-made: much more complicated to use and setup Let s see what s on the market 33
FP-telescope-BF Complete systems (here: Lunt) Refractor 60mm, BF1200: 2370 euros with double stack: 4600 euros Refractor 80mm, BF1200: ~4795 euros Refractor 100mm, BF1200: ~6645 euros Refractor 150mm, BF1200: ~10575 euros Similar order of magnitude for Coronado (teleskop service) 34
ERF-telescope-TC-FB-BF HaT 203/235/280mm: 4400/6400/9400 euros TTC. Comes with TC Need to add the FP and BF! FP: daystar (3-6k euros) or modified PST (~700 euros) BF: depends on the size (standard: ~1000 euros) Minimal cost: ~8500 euros 35
ERF-telescope-TC-FB-BF Home-made solution catadiopric scope (e.g. Maksutov) 150-180mm (2nd hand: 500-1000 euros) ERF 135: 755 euros, 160: 965 euros, 180: 1365 euros TC:~300 euros FP: daystar (3-6k euros) or modified PST (700 euros) BF: depends on the size (standard: ~1000 euros) 150mm: ~3.2k 200:~5k But...we have a 8 LX50 at the club. Consider then: ERF 180mm (1365 euros)+ filter holder PST (700) or daystar 0.6 A (~4700k) BF ~1000 euros TC ~300 euros Overall: ~3.5k with mod PST! ~7.5k with the daystar. Add rings to put on the EQ6 (nasty fork mount vibration) 36
BelOptik Coro Find a nice achromatic refractor (~120 F/D=12-15): 1000-1500 euros Get the BelOtpik Coro (~1000 euros) Total cost, say 3000 euros max, and can potentially go up to very resonable aperture for a reasonable price...but of course, this means a very long OTA!! Could go for a lower F/D, considering ERF treatment applied on front lens element, gold-cover on the occulting cone... 37
What do we have in our bank account? Currently (today): 5418 CHF Soon (2 or 3 more memberships): say 70 CHF In a couple of months: 500 CHF from Staff Association Total: 5988 CHF We can ask to CERN for an exceptionnal participation, but we need a precise plan and estimation of costs. 38
Summary of prices (just a couple of examples) Type/scope Price Remark Lunt Ref 60 BF1200 ~2400 general use, small diam BA Achro Ref 100+ BelOptik ~3000 Eruptions only ERF+LX50+PST+BF ~3500 large diameter H-M solution #1 Lunt Ref 60 BF1200 Double Stack ~5000 BA + CERN Lunt Ref100 BF1200 ~6600 ERF+LX50+PST+BF ~7500 large diameter H-M solution #2 HaT (PST) 8 ~8500 Lunt Ref 150 BF1200 ~10500 Biggest Lunt Ref... 39
ROS Probably the best place around to see what is going on on the solar observation side Commercial and personnal innovations Many experienced users Nice place Next meeting: June 20th and 21st in Serbannes http://www.soleilactivites.fr/ 40