Jupiter with the 9.25

[matt]

OK guys. Nowhere near the Dennis/Rob T class but then neither was the seeing!

Thought I'd give the 9.25 a run last night to see what we'd get.

Seeing wasn't too good but the image shows an improvement on prior efforts with the SCT and that's all that matters.

No motor focus or cooling, but did have the new dew heater running, which I think made a difference.

Managed to adjust our capture settings for a more natural appearance and this time we've caught some extra detail like extra swirls in a few of the belts and some extra "spottage":lol:

Feedback as always most welcome

[asimov]

Nice job Matt. It has that nice 3D look, due to the limb(s) being in slight shadow. (non technical person: Don't know the correct terminology)

Care to share your wavelett settings?

[matt]

Hey Asi Thanks for the encouragement. It's nowhere near as good as the image you've posted in the last half hour but I'm workin' at it. My wavelets was very different to yours. I worked sliders 4,5 and 6 pretty hard. From memory I think 6 was about 65, 5 around 50 and 4 about 30. I sort of work a sliding system from 6 the hardest, downwards. I'm fascinated by your experiment with using just the one slider. I still don't think I've got collimation right??? The star test looked ok though, although I noticed my central obstruction looked bigger on one side of focus than the other. Could I be dealing with a problem primary perhaps???

[[1ponders]]

Up and running matt. Way to go :thumbsup:

A quick question re your setting up. Do you check your collimation before imaging and then recheck it during the night?

[matt]

Paul Re: collimation - I suspect this is one area where I can still make great strides. To my eye it looks OK, but I'm sure my eye is just simply not experienced enough. I'm seeing a nicely positioned central obstruction and concentric rings, but I've perhaps not had good enough seeing to crank it up to really high mag and test at that level. Last night I star tested with the 10mm XW

[Daniel Beringer]

Excellent, your getting some good detail with the C9.25....nice image scale too!

[[1ponders]]

If your seeing will let you have a go at trying it using the NexImager and barlow on the laptop (or leave the barlow out if it's too much).

In some situations I've found that its' helpful, if for nothing else than keeping the star in the center of your imaging train. If the star image is out near an edge using an eyepiece then curvature can affect what you see and the position of the diffraction rings.

[matt]

Thanks Daniel Still plenty of learning to do but that's all part of the fun

[matt]

Paul Re your comment: "If the star image is out near an edge using an eyepiece then curvature can affect what you see and the position of the diffraction rings." I have no idea what that means in terms of collimation, given I check the diffraction rings only when the image is centred in the ep?????

[[1ponders]]

When you adjust the collimation screws the star will move out towards an edge of the field of view because the secondary mirror is moving. You then recenter the star. If the star is not well centered then, as I understand it, because the star is now an extended object rather than a point souce and the scondary is convexly curved, the appearance of the diffraction rings can be affected by the curvature of the mirror.

If I'm being really pinickety on a night of imaging, I'll use my ToUcam and the reticle function of K3CCDTools to make sure my defocused star is dead center of the screen. That way I can be pretty confident my diffraction rings are off center because of collimation and not because of where the star is in on the secondary.


Does that make sense :shrug:

[asimov]

Plenty to be learned here Matt, thats for sure! Yes, up to only last night I've always used waveletts similar to you ie: #6-30 to 40 / #5-24 to 30 etc etc etc. I'm stacking the same AVI right now as ANOTHER experiment, this time using 1 & 2 waveletts only. (depends on the amount of frames stacked here, as to how far you can push them)

I don't collimate until the scope has reached ambient. I was collimating using 2X barlow + extension tube + 7.5mm EP the last few nights....Now I use 2X barlow + extension tube + toucam. ;) I see better 'quality' diffraction rings/central obstruction on the laptop than by eye threw an EP. Try it. (On a fairly bright star close to the intended target) You'll have to boost/tweak gain & gamma to get a good image.

I think cooldown is just as important as collimation with SCT's. I set mine up just after sunset, cover it & forget it. By the time Jupiters high enough, I'd say its very close to ambient, even without the cooler.

[asimov]

Makes total sense to me Paul. Thats the way its always been done, & always will be.

[matt]

Paul. Was just a bit confused coz I've been reading different ways to collimate an SCT. The way I've been working is to start with the star in the centre of the field of view and de-focus to get diffraction rings. Then judge how central the obstruction is and how concentric the rings are. If they are out, move the image around the field of view to find the spot where things look more centred and concentric, then turn the secondary collimation screws to bring that improved image back to the centre of the field of view. Have another look and repeat if necessary. If the seeing allows, insert higher mag ep and do it all again. Asimov... glad it all makes sense to you, you clever fellow, you!

[iceman]

Looks good matt, has the "Bird" colouration and style :)

I think you were let down by the seeing most of all. Looking forward to the next attempt!

[matt]

Thanks Mike That was something I was really keen to achieve with this image, even if it looks a little soft. Getting those more natural eyepiece tones is actually quite a challenge. It's so tempting during Registax and post-process to push things too hard. I also tried a few things differently during capture, which made the overall experience worthwhile. Set gamma and gain to around 60%, brought brightness down to about 50% and backed saturation off to around 60-70%. That's the highest I've worked the gamma and gain. Seems to work quite nicely.

[[1ponders]]

Well there you go, ya learn something new everyday. That sounds similar to the meade standard technique but with a twist. I hadn't heard about finding the spot where the rings are concentric first. I'll have to give that a go. :thumbsup:

[matt]

And I'll try yours Paul. Given the quality of your recent posts I'd be an idiot to ignore your method!!! LOL

[bird]

Nice image Matt, I was out last night as well, but the seeing around here was too poor. I'll be out again tonight though, see the 'HST + Amateurs' thread... Hopefully you can have another go as well.

Bird

[asimov]

Oh, you must be assuming my comment was a smart-A one Matt, :lol: it wasn't mate I assure you. (I'm thick as 2 pallets of bricks!) :D I just meant while were using curved mirrors, star centering is a must. I'm with Paul too....never heard of that technique you just described! I'll try anything!

[[1ponders]]

Oh, I just remembered another benefit of doing it through the ToUcam. It's live eye. You don't have to look through an eyepiece and reach around the end of the scope to adjust. Simply position the laptop in the most convenient spot and watch the screen. Adjust collimation with one hand hand and adjust scope postition with the other to keep it centered on the screen. Very comfortable and civilized. You can even carry on a conversation and demonstrate at the same time. How geeky is that :D

[matt]

No Asi. Didn't think you were making a smart-A comment. Quite honestly meant that you are a clever lad. You've got that 9.25 moving at a 1000mph and I'm floundering in your dust!!!

[matt]

Interesting, Bird. I was also thinking the seeing was a bit dodgy. Thanks for that. Yeah, hopefully will do better tonight. Thanks mate. Although the jetstream's looking a bit rough?

[asimov]

Oh ok, lol. Not really mate. I've had one night of good seeing & that's it!

The night I got those 2 AVI's, I got rained on twice. Then after stacking the first AV & realized what I had...I deleted all the other AV's I had (including my best Saturn) with the intention of racing out & getting heaps more!.....Only to find it clouded over! NOOOOOOOO!!!! So I waited & waited & waited. It stayed cloudy. I was livid!! No doubt woke the neighbours at 4AM with all my cursing & shouting!

Last night, well, I got one AVI....stacked/tweaked/deleted. The jetstream was/is here travelling at the speed of sound lol.

[Robert_T]

Matt, you've got the makings of something really great here, all the macro detail is very well defined and you've got the colours I want. Could be seeing or collimation that's not letting you get just that extra step in sharpness (and wavelet settings as Asi will point out), however, I'm beginning to think focus is perhaps an often under-rated factor. When I look back at my images, the biggest single improvement wasn't gained when I changed scopes or cameras, but when I got myself a meade motorfocusser.

Keep up the great work!

[matt]

Thanks Rob. Funny you should mention the issue of focus. I was thinking exactly the same. I was noticing the other night that these SCTs present a couple of probs in this dept. I was familiar with the obvious image shift as you rack the focus in and out, and also the not-so precise nature of using the focuser knob. However, I've also discovered another issue which makes focusing even harder using the standard knob. The simple act of applying inward or outward pressure by your hand on the focusing knob, pressuring the focus mechanism in a lateral direction - towards or away from the corrector - also impacts significantly. I've noticed some quite considerable loss of focus the moment I take my hand away from rotating the focus knob precisely when the image is crisp and sharp on the screen. Honestly, it's a nightmare!!!!! Does this problem have an astro/techo name i'm unaware of?

[Robert_T]

Matt, not sure if this has a name, but I'm not surprised by this action given the mechanics of mirror shift focussers. Perhaps Dennis can shed some light. He mentioned something about a mirror lock that he has for his C9.25? I tend to approach focus with an anti-clockwise turn and then do the fine focussing with the motor focus unit. Re focussing every now and then in the hope I'll jag perfect focus for some of the avis.

[matt]

Thanks Rob. Regarding the collimation issue. I'd be really keen to see a few NexImage shots taken through your scope of a star test. Mine look good at about 300x, but I've noticed a difference in the size of the central obstruction in the outside and inside focus images.

[Robert_T]

that's normal Matt, your inner and outer focus images won't be exactly the same (unless you've got a refractor maybe). The key thing is that the rings are concentric either side of focus. You really need to be running >500x magnification for critical star collimation and the nights where seeing is good enough to use that aren't all that common...

anyway, I'll try and capture collimation some time soon and post. Be more interested to see Dennis's though - he get's diamon razor sharp images!

cheers,

[Dennis]

Hi Robert

Have a look at:

http://www.iceinspace.com.au/forum/showthread.php?t=8831&highlight=diffraction

Msg#2 contains inside and outside of focus star images with the x2.5 in the optical train.

Cheers

Dennis

[matt]

Cheers Dennis. You're the man.

I'd forgotten about this very handy post.

Collimation looks pretty much the same as mine. The only challenge will be waiting for a night of great seeing where I can push the mag to >500x.

I can only assume seeing has again fallen short of what was hoped???

This is Canberra, after all:lol:

And I'm also now in the market for a precision electric motor focuser. Wish you hadn't snapped up that JMI Dennis!!!

[asimov]

when the scope is pointing up 45 deg +...gravity is coming into play with the weight of the primary mirror. Wind the focuser knob clockwise, the mirror is moving down towards the EP end of the scope & the knob is very easy to turn. Wind it the other direction, its fairly firm to move. This is because your fighting against gravity. When focussing, I get it to focus as viewed on the laptop, then I wind clockwise slightly, taking it out of focus, I then tweak it very slowly back the other way until I gain critical focus. This takes all backlash out of the system & will not shift on you while your imaging.

[Lester]

asi, your'e a wealth of information.

[matt]

Thank Asi. Actually, I'm aware of that issue with the mirror shift and backlash, but that other issue with the shifting is something altogether different.

I'm gettin' me a microfocuser;)

[asimov]

I'm getting me one too....just a matter of making it. :D

[matt]

Good for you, matey!!!

I'll be paying for mine .... thru the nose ... big-time!!!:lol: :thumbsup:

[Lester]

Okay chaps this is what I did many years ago with my mid 1970's Celestron 8". After removing the primary and corrector with secondary, I drilled 3 holes into the base of optical tube and threaded them to fit 1/4" thread. I then placed a small dob of silicone on the end of each bolt. Once focus is achieved the bolts are screwed lightly and evenly up against the rear of the primary to hold it in place.

DANGER.....DANGER.....DANGER! You do this at your own risk. But I am always looking for the easy way out.

Sorry I don't have any test results to say how successful this was, because at the same time I stopped using my C8 as a guide scope on the 16" Newtonian and went to a off-axis guider.

[asimov]

Yes, I've seen that done on a C14. Works a treat!

[[1ponders]]

You won't regret getting the microfocuser Matt. I know I'd be lost without mine, I don't have the patience to try with just the SCT focuser. I had a meade microfocuser with my LX200 originally, but with the new OTA I went for the JMI. Glad I did.

And btw one of the biggest reasons I bought a meade 8" rather than a celestron was because of the mirror lock (if the 9.25 was cheaper I might have overlooked it). Lock that sucker down and you are set for the night with just minor shifts in the microfocuser. If there is a kit around for the 9.25 think about that too.