I don't get it!?

asimov (John) · #1 15-10-2005, 02:50 AM

No jetstream.....no wind.....Yet the seeing conditions here right now (2:20am) I'm giving 4/10!!!

Mars in the scope looks like I'm looking thru the bottom of a empty stubbie!

No nice mars photo's from me! Hope you guys in Adelaide are having better luck than me!

I hate astronomy sometimes!

DSO · #2 15-10-2005, 09:23 AM

Frustrating, isn't it? I can get set up for an observing session sometimes, or drive to our local observatory only for the dreaded water vapour to build up. Astronomy is a frustrating hobby, but the good times far outweigh the bad.

Starkler (Geoff) · #3 15-10-2005, 09:44 AM

Scope well cooled?

Itchy · #4 15-10-2005, 10:20 AM

Quote:

Originally Posted by asimov

I hate astronomy sometimes!

Astronomy is a lot like Golf. My worst night doing astronomy is better than my best day at work.

Cheers

seeker372011 (Narayan) · #5 15-10-2005, 10:40 AM

Quote:

Originally Posted by Itchy

Astronomy is a lot like Golf. My worst night doing astronomy is better than my best day at work.

Cheers

asimov (John) · #6 15-10-2005, 02:28 PM

6 hrs worth of cool-down time. I usually setup just after sundown, chuck a cover over the scope then go back inside till I'm ready.

I've found the jetstream maps to be not quite accurate....this confirms that theory in my mind at least.

The proof is in the seeing.

33South (Chris) · #7 15-10-2005, 02:53 PM

Quote:

Originally Posted by Itchy

Astronomy is a lot like Golf. My worst night doing astronomy is better than my best day at work.

Cheers

I'll drink to that

ving (David) · #8 15-10-2005, 02:59 PM

well its not my fault!

atalas · #9 15-10-2005, 03:11 PM

Quote:

Originally Posted by ving

well its not my fault!

You were the first suspect David

asimov (John) · #10 15-10-2005, 03:15 PM

I gave up work cos' it was cuttin' in to me viewing time!.......

ballaratdragons (Ken) · #11 15-10-2005, 03:41 PM

Yep! Frustrating indeed!!!! But it makes it worthwhile when the sky is good.

rumples riot · #12 15-10-2005, 06:49 PM

Asimov, we setup with my scope for a impromptu drinking session and some imaging with EXFSO, Gadget, another mate and myself. Seeing was initially around 1/10. Really bad and the image looked like a mix master going on 1000. No detail was visible at all and trying to focus was impossible.

Thinking that maybe the collimation was off, EXFSO and myself set about checking it at 2am. Yes collimation was ever so slightly out but we quickly made the adjustments; mind you this would not have accounted for the bad images. See the collimation shot below. Dont worry about the pinch, it is tube current related.

By about 3am EXFSO and myself were the only ones still attending and by this stage very under the weather. Peter went home and I decided to wait out the dreaded tree for the vain hope of some good seeing. Around 4am Mars was once again visible and it was the first time I had seen it since 2am and before that 1am. Damn tree on my neighbours block is treading on dangerous ground. Very frustrating.

At 530am after taking a couple of AVI's of Mars that were at best ordinary and looking at Saturn with a 12mm (which gave a beautiful view) I decided to pack it in. Seeing over the course of the night would have only gotten to a very shaky 3/10 and transparency would have been very low also; no doubt contributing to the haze. Very disappointed and goes to show that all the preparation in the world cannot account for the weather.

Paul

asimov (John) · #13 15-10-2005, 07:22 PM

I must admit I nearly fell for the: "It MUST be the scope!!"

.....trick!

I started thinking "hmmm...perhaps theres a smudge on the eyepiece/collimation out/dew!???"

Then I had a closer look: Sirius was twinkling like crazy. A dead give away for totally crummy seeing. I stuck it out though & waited, just in case it came good, which happens a lot around here.

At least you had a nice night under the stars with your mates.

You had nothing better to do did you Paul??

Please don't mention trees! I love trees...but not when they get in my way astronomically speaking.

Drill 1/4" hole on 45 deg angle (with hand-drill) pour in roundup, block hole up with sawdust from drill.

davidpretorius · #14 15-10-2005, 07:28 PM

Guys, for collimatioin, what eyepiece, what star and how much out of focus so you go to get that image.

i can get the cd's coming up and they are pretty good.

but a "star test" still has me beat thru lack of knowledge???

asimov (John) · #15 15-10-2005, 07:50 PM

I'm guessing when you see these 'CDs' you must mean you de-focus a lot.

I do a star test in increments: bung in 15mm get shadow of secondary in centre of CD. bung in 7.5mm do the same thing. bung in 5mm do the same thing....then get closer to focus with the 5mm. As you get closer to focus, the CD decreases with size obviously....& hence so does the more accurate your tweaking of your primary has to be to..........I'm finding this real hard to explain!!

Put it this way: You must use fairly high magnification. If you see a gigantic CD with a black shadow in the centre, it's too hard to guess if that shadow is in the centre of the bright disk. You need to get the image smaller by getting closer to focus. As you get closer to focus the image will change.

You must use a medium bright star. it must be close to zenith. it must be 7/10 plus seeing. Your scope must be ambient.

Sorry Dave. Not very good at explaining myself here.

I'll see what articles I can find (I have heaps on the puter) & email you with an article/s...

Unless someone here can explain it better! I KNOW how to do it....but can't describe it! (go fiqure)

asimov (John) · #16 15-10-2005, 08:22 PM

Heres a good example Dave. If you were to try to get a perfect focus with this kind of collimation, the result would be a star with a comet tail (as you described in a previous thread)

asimov (John) · #17 15-10-2005, 08:35 PM

Another thing I should mention: I find it easiest to pick a star. centralize the star in the FOV. de-focus star slightly until you think you see a star with rings around it. Get the star off-axis to allow the star to 'drift in' to the dead centre of the FOV THEN decide which way you must tilt the primary. Thats the hardest part, working out which way to take it!! You have approximately 2-3 secs at that mag to make a decision with no tracking.

davidpretorius · #18 15-10-2005, 08:37 PM

i am following you,

If i look at the stars say in the "trap" with my 12mm, i have the stars going to points, but if i move the focusser slightly out of focus, i get the outside focus, ie the star grows hair for want of a better term!

Given image is upside down and back the front and the focusser is on the left hand side, which primary screw should i start adjusting and by what increments ie 1/4 turns???

thanks mate

davidpretorius · #19 15-10-2005, 08:38 PM

i am actually yet to see rings! I think!!!

asimov (John) · #20 15-10-2005, 08:43 PM

I would suggest your not seeing rings because the 'criteria' is not being met. good seeing, close to zenith blah blah