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Viewing the CRAB PULSAR

Started by Thomas Dey, 02/07/2016 01:46PM
Posted 02/07/2016 01:46PM Opening Post
This was indeed "After Dark" last night: I have become obsessed with the Crab Pulsar and wanting to actually see it. Never had even tried before because assumed it's impossible. But I have this 29-inch Dob and the Pulsar is (ostensibly) mag (Mv) ~16; which would be just on the cusp of a scope that size. Well, Yes - I can see it, sort of: First I tried Nagler 31 107x no; then Ethos 17 196x no; then Ethos 13 256x ... maybe. By that I mean I could see something stellarish in the right place, but only fleeting with averted vision and that sort of subliminal where all I know is I could see Something there but not further describe it. And (knowing) there are actually Two stars there (the Pulsar and it's "companion"), I don't want to claim I saw the Pulsar itself as a discrete object. Next I tried the Night Vision (Micro IIE) ITT Gen3 "eyepiece." COOL! I can see the two stars! The "companion" is really pretty easy but the Pulsar is medium tough. They are quite close together, with the pulsar "leading" as they cruise across the field. I tried my visibility test for medium tough targets: Ask myself once a second for a full minute "Do I see it?" Yes, yes, yes ... , yes." So I can hold it for an entire minute without losing it = SEEN! A few technical notes: This is in agreement with my observation that Night Vision picks up 1-2 magnitudes on stars. There are other advantages (and disadvantages), but it is certailny something to consider adding to your eyepieces. I know some pureists would point out that I didn't actually SEE it, because I was cheating using the Night Vision. But, taken to its logical limit ... you'd better remove your eyeglasses before you claim you can see 10 stars in the Pleiades? Come to think of it - Galeleo cheated! Nother note: used my "Sky Quality Meter" for the 1st time. Pointing toward the "winter" constellations it reads 20.9 mag/sec^2; pointing toward the (dimmer) spring sky it reads 21.2. So regular star light actually does affect the reading! I am also pleased that my back yard sky is good - not Great ... but Good!

STOCK PICTURE ATTACHED - from my Observing Log, shows marked what I saw. Tom Dey

Attached Image:

Thomas Dey's attachment for post 60038

29-inch Dob in a dome
36-inch upgrade soon
LUNT 80/80 solar scope
FLI 6803 cam
APM 100mm APO Binos
JMI RB-16 Night Vision Binos
Zeiss 20x60 IS binos
Posted 02/08/2016 10:15PM #1
Nice score smile

~ Charlie Stevenson

8" f/5.7 String Telescope - 1st Scope Build; 2nd Place Stellafane 2016 Optical Award for Newtonians 12.5" and Smaller
10" f/4.5 Newtonian (June 2015) mirror refigured by Optic Wave Labs P-V WaveFront 1/14.24, Strehl Ratio 0.993 (Aug '15)
Criterion RV-6 seems to be circa 1973 (June 2015) [For Sale]
Celestron C8-A XLT (January 2015) [For Sale]
Celestron PowerSeeker 70AZ (Christmas 2014)
Aldrich Astronomical Society member since 2015
http://astro.charleskelleystevenson.com/
Posted 02/14/2016 02:33PM #2
Update: It's been too cloudy or cold to look again, but seems the Pulsar is more like mag (Mv) 16.5 rather than 16. What puzzles me is that it should be easier to see (with this good 29-inch!) than I experienced. Now I'm thinking I may not have used enough power: The nebula itself must be washing down the stars, not unlike trying to see the central star in the Ring --- should be easy but the nebl renders it tough! Next chance, I'll go up in power --- from 256 to 416 YIKES! That's most always too much mag for resolution - but should improve the star/background contrast because the pulsar looks like a DOT ... a miniscule DOT at 256x. The only way I can get more mag with the Night Vision is to use a Barlow --- so will try that too. (The effective NV mag was a Very low 131x) Tom

29-inch Dob in a dome
36-inch upgrade soon
LUNT 80/80 solar scope
FLI 6803 cam
APM 100mm APO Binos
JMI RB-16 Night Vision Binos
Zeiss 20x60 IS binos
Posted 03/12/2016 07:14PM #3
UPDATE: Last Night - I added a high-end Optical Chopper to the scope and tried to strobe the 1st (known) harmonic to no avail. Also added a (custom) Barlow and various filters to keep the chopper source from getting to the Night Vision. The chopper is super-duper (Thor Labs) that I can trick into providing accurate freq to (far better than .01 Hz?) AND phase to around a milirad. And I can tune freq and phase on the fly! It even tells me when it is freq and phase locked. But the display is backlit blue and squirts out everywhere - so I wrapped the control box in black velvet. All this atop a 12-step warehouse ladder in the dark in the dome at the eyepiece with that spinning chopper like a meat-slicer a few inches from my face! I'll try more. but this ain't easy or cheap --- probably why I'm trying it. I'm guessing it won't be 'till late summer before I succeed --- or not at all. Worth the try though. Done enough to convince myself that no one has actually SEEN the Pulsar flickering unless they are chopping at a professional, VERY BIG scope. It indeed would be very easy to confuse Scintillation (in the atmosphere, eye and especially the Gen 3) with true strobing. So I'm not claiming success yet. Nevertheless happy that I can at least SEE the pulsar (as a dot) and that I am at least trying the near-impossible... Tom

29-inch Dob in a dome
36-inch upgrade soon
LUNT 80/80 solar scope
FLI 6803 cam
APM 100mm APO Binos
JMI RB-16 Night Vision Binos
Zeiss 20x60 IS binos
Posted 04/02/2016 04:08PM #4
Oh well - the weather here has been typical = not cooperating. And especially at this latitude the Crab is speeding toward the sun/daylight. Anyway, the 36 I have the mirrors and all the parts are ordered to build it in as a giant GOTO/Track Dob in the Dome. Advantage of building it also that I will optimize it for permanent installation use and even have a separate focuser board that incorporates the Night Vision with the chopper as close to focal plane as possible. The tracking might also allow me to try to do high-speed radiometry if the looking at it fails. I'm stubborn, so unlikely to give up on this until I knock myself out... Tom Quixote

29-inch Dob in a dome
36-inch upgrade soon
LUNT 80/80 solar scope
FLI 6803 cam
APM 100mm APO Binos
JMI RB-16 Night Vision Binos
Zeiss 20x60 IS binos