19.12.05 obs report

[ving (David)]

no fancy names for this one!

date: 19/12/05
time: 9pm - 10:15pm
scope: 8" f6 newt
seeing: 8.5-9/10


I had what had to be the best seeing i have had for literally ages. I set up the scope in the back yard just before sunset and let it all cool, then did some collimation, shes been way out for ages but now shes perfect.

went out at dark to do a bit of looking around, i had at that stage no idea that the conditions were going to be soo good! basically I just wanted to test my collimation (which is pretty much spot on now) but ended up cruising around the orion doubles ,mars and sirius.

after reading birds post on collimation i decided that a good star of about mag 2 to test on was mintaka in orions belt. being early still she did a bit of dancing but once everything cooled i had a very cool view and i could tell that my collimation effort from before was damn near perfect...
I looked at rigel, a sweet looking double of white/blue (A) and blue (B) easily split, but I never have problems with this one... I just like looking
heading down orion i hit m42 which in a sky that was still a bit light lokked dimmer than usual, more like it does with the moon out. I could make out 6 stars in the trap tho wich makeit it only the 2second time i have been able to do so. I continued to just scan around heading to alnitak to see if i could see the flame neb but the sky was still too light and i only made out the faintest bit of nebulosity.

pupis: I went to look at the MOC object in pupis again after hearing that theres a PN hidden in the field of stars. I had completely forgotten how to get to m46 and was hopping all over the joint... I gave up and got my Palmpilot out. If you dont have a palmpilot yet, go and get one and get palm planetarium to go with it its toip stuff
anyhow, star hopping my way down from sirius i found both m46 and 47 and dont they look 100% better with a properly collimated scope! I found the PN but only with averted imagination... it wasnt easy!

By now the sky was dark and noticing how stable everything was i headed to mars. its the best i have seen the planet! so much detail I spent about 15 mins just staring at it in wonder.

with everything so still and stable i just had to try and split sirius
I thought i had it at one stage making out a small speck wobbling in and out of focus within the discs but its a hard one to do so I'll go back agian one day...

back to orion and its doubles. 23 orionis is an easy split, star A is mag 5 and B is 7.2 which is enough to make is hard when they are close together... but they arent, theyre 32" apart which ou can do in a finder
33 orion is hard one. there is only 1 mag diference between A and B and they are only 1.9" apart, but surprisingly with such good seeing i could bump the magnification right up to 320x to see a clear division between them happy as a pig in mud i was. I had failed last time and now, well!!!
32 orion: I was feeling lucky after my 1.9" split and decided to push my scope harder. still only 1 mag diference between the 2 stars but this time only 1.2" seperating the 2! using all avaliable power (ie 2x barlow and 6.5mm ep) i jumped in with both feet and well.... it was just that easy they wobbled a bit and sometimes the gap between then disapeared completely but I split them. 2 lil' white stars that look like they are joined at the hips, and then every now and then there'd be just the smallest gap between them

completely stuffed from a late night the previous night i hit the sack to dream about binaries
(ok I made the dreaming part up )

back

[Robert_T]

Onya Ving, your passion for doubles is obvious (and catchy)! Sounds like a great night out under the star-stars


cheers,

[[1ponders] (Paul)]

Good onya ving. I can tell you enjoyed yourself. I wonder how you'd go using an aperture mask on sirius. You might be collecting too much light.

[ving (David)]

I had the aperture mask just sitting in the base of the dob... i didnt think to use it!

oh well

[Robert_T]

Originally Posted by ving

I had the aperture mask just sitting in the base of the dob... i didnt think to use it!

oh well

Ving, would the best aperture mask for double splitting involve a ring on the outer edge of the mirror so you can get maximum resolution or do you just use a smaller disk mask between the spider vanes?

cheers

[ving (David)]

I use a single disk that sits between the vanes. no obstruction then
its only 80mm but thats plenty on really bright objects, which is what i use it for

[asimov (John)]

Nice report sir! Glad you had fun

[asimov (John)]

Originally Posted by Robert_T

Ving, would the best aperture mask for double splitting involve a ring on the outer edge of the mirror so you can get maximum resolution or do you just use a smaller disk mask between the spider vanes?

cheers

Hi Rob. I'm a bit of an aperture mask nut as well On my reflector I use the standard 3 holed (round holes) mask. Depending on what I'm looking at I will leave the 3 holes open, or I will close 1 up....or 2 for that matter, It's a variable brightness mask lol.

I have one as you describe for the refractor as well..never thought of making one like that for the reflector..

[xstream (John)]

Always love your reports David.

[Robert_T]

Originally Posted by ving

I use a single disk that sits between the vanes. no obstruction then
its only 80mm but thats plenty on really bright objects, which is what i use it for

Hi Ving, you might not need the light, but you might need the aperture to get the resolution needed to split very close doubles. You know how they quote theoretical minimum arc second (another technical term) resolving power for different diameter objectives. Your 80mm disk will give you the resolving power of an 80mm scope - not sure what that is, but it's way more than an 8 inch scope - whereas a thin annular mask that exposes only a small amount of the outer edge of your mirror of equivalent area to an 80mm objective should "theoretically" still provide the full resolving power of your 8 inch scope while only utilising the same amount of light as the 80mm. Make sense?

Of course whether you can get a good focus with such an annular mask (Asi?) and the greater impact of atmospheric turbulence etc on the larger mask might over-ride such advantages.

Just a thought

cheers,

[ving (David)]

hi robert... i have no idea what you are on about.... annular? it doesnt make sense to me how it'd have the same resolving power

[davidpretorius]

great report ving,

i will have a go at these, where is a good place to start working thru doubles and triples

[ving (David)]

spirit of 33 davo, spirit of 33

[acropolite (Phil)]

Excellent report Ving, as usual, I always feel as though I were there.....

[asimov (John)]

Uuumm....EH!? (this applies to both Robert & vings latest posts)

[ving (David)]

http://www.s33.org/

[fringe_dweller]

doubles and multiple's rock - go the eyeballers!
nice one dude!