Ouroboros

1 minute ago, Elp said:

Is it just me or does the unit look absolutely huge, it's like attaching a home router to your telescope.

It certainly looks maybe twice the size of an Air. 

I watched the Lazy Geek’s vid the other day just after it was released.  I thought it looked quite promising. I don’t think I’m ready to jump ship from the ASIair quite yet. But I’ve had some poor experiences with it recently which make me wonder whether ZWO have lost their edge with their product. 

Thanks, @Budgie1.   I’ll look into that.  I also had a reply from Adam Block on the Pixinsight Forum drawing my attention to the star de-emphasiser script. Apparently this can be used to preferentially de-emphasise smaller stars. I have yet to look into it. I’ll report back. I might be some time.   

Thanks, @Budgie1.  I’ve got that. I tend to use blur exterminator now. 

But isn’t Star Reduction doing the exact opposite of what I’m saying. It allows you to protect  small stars. What I want is, having reduced stars in blur exterminator, to protect the brightest stars whilst reducing the many small stars.

Trying to do this with levels or curves doesn’t work because it tends to give bright stars a cut off look - as the screen shot in this much zoomed in image (left) shows.

What’s the best way to reduce the brightness of small stars whilst keeping the brightness of the bright ones?  I find Curves doesn’t do this very well.

Is there a script that leaves the main, bright stars unaffected, but attenuates the small stars?

Spiffing! 

Worth pointing out that the Practical Astronomy Show is advertised for Saturday 23rd of March 2024! not the 9th. @mikeDnight
 

Practical Astro Show

43 minutes ago, Stefan73 said:

If you want to do astrophotography with a DLSR then you're probably best going for the thinnest OAG going.  Something like this: https://www.firstlightoptics.com/off-axis-guiders-oag/ts-off-axis-guider-tsoag9-length-only-9-mm.html

Even if your focus position is fine with a thicker OAG you might want to use a coma corrector in the future and those often have 55mm back spacing so you wouldn't have room for anything thicker in front of the DLSR.  

I've no experience with the 200PDS but the 130PDS was not usable without modification even with the above 9mm OAG as the focus tube was pretty much in as far as it would go to achieve focus and you just got pacman stars without cutting off a lot of the focus tube to stop it protruding.  Using a coma corrector too was fine though.

 

I agree. I wouldn’t use an OAG with my 200P for the reasons you point out. I have obtained adequate guiding with my 200P using a 9x50 finder guider - although perhaps one might expect slightly better results using a  longer focal length guide scope.

Something else you don’t often hear mentioned is how useful a finder guider (or separate guide scope) can be for  observing. If you set the finder guider as the main scope, and use plate solving, you can be sure that the weak fuzzy target is smack bang in the middle of the eyepiece - assuming that is you’ve aligned the guidescope and main scope to the same point. I don’t think you can do that with an OAG. 

It’s looking good. What are you going to go for as your first target, @Beardy30? 

Good luck with your purchases, @Beardy30.  That looks  like some good value kit - not too Astra nomically priced.

17 minutes ago, Rallemikken said:

On the side; thread seems to stretch out: On Linux it's easy to back up personal settings, and take them from one install to another, or from computer to computer. Really handy regarding those big indexfiles for local platesolving. KStars uses this directory:

/home/<your_user_name>/.local/share/kstars  (dont miss the dot)

See if you find something similar om your mac (or even Windows) and keep a backup on a USB-stick. Or burn to DVD if you can.

Well, thank you all who dug up this archeological thread and then took the time to respond. I’m afraid I moved on to using an ASIair,  which does everything and probably more than I was doing with KStars etc three years ago - and certainly more reliably and intelligibly. 

Looks like you’ve made an excellent start mastering the necessary skills for the AP game.  Was that with guiding? I suspect not. Your polar alignment must have been pretty good. I think I can just about see some ellipticity in the stars  suggestive of drift.  Only just mind.  Guiding will fix that and, as you’re no doubt aware,  you’ll be able to push your subs out to several minutes. 

If that’s the first one I can’t wait to see the second.  😀  Joking aside it’s a truly fantastic image, @Craig123.  Almost unreal and I mean that as a compliment.  Like it’s been painted.  It’s images like this that make me ask myself why the hell I am still bothering with astrophotography. 

Would the roof close automatically if the rain came?  Very nice image @wimvb!  I sometimes think that in our attempts at large targets we forget that star and galaxy fields make worthwhile images too. Are the spectral lines at the top left the glare you refer to or something else? 

19 minutes ago, Oddsocks said:

The gold standard for resolving flats issues is to compare artificial panel flats to pre-dawn or post-sunset sky flats taken with a stationary mount (tracking switched off) pointing approximately 30 degrees above the horizon of the anti-solar point, and no other diffusers in the path. If the calibrated sky flats also show the same gradient then you can rule out the panel as being entirely to blame.

My experience is that you don’t need to be that picky. Any old sky with a diffuser ie several layers of t-shirt or whatever over the input end of the telescope will work absolutely fine. I do point the scope away from the sun and avoid shadow falling on the diffuser.  It’s fine as long as the light falling on the t-shirt is reasonably uniform.  The diffuser is so far from infinity (or the far field) the camera doesn’t ‘see’ it as an imagable object, if that makes sense. I’ve done my flats like that for years until more recently when I started using an iPad plus T-shirt diffuser with a small refractor. Again. No problem.  

I’d stick a t-shirt over the telescope and point it at the daytime sky. That’s got to produce uniform illumination as long as you avoid shadows falling on the diffuser. Try not to have too short exposures ie  add more layers to make them longer than a second or two. See what that gives you, 

Have you tried taking flats some other way, @aleixandrus ie without the flat panel?  It might be good to establish whether this problem is panel or telescope related? 

23 minutes ago, Horwig said:

Thanks, the original TIFF looked a lot better to my eye, using 'export for web' from photoshop seems to screw up the saturation, not sure why.

H

I think that of my images posted here.  Is png better, and does the site accept them? 

Looks good. I like the natural looking colours.   Perhaps a toned down bit of noiseX might help? 

@geeklee’s suggestion sounds about right. Opinions seem mixed about this latest version. Mostly good though. The few times I’ve tried it it’s been amazingly good. Almost so good that one wonders whether moderate amounts of  tilt or similar issues issues is going to be worth worrying about. Or for that matter … do you really need that expensive astrograph?  😀

1 hour ago, Stu1smartcookie said:

A lovely new tripod thanks to those peeps at FLO … the stellalyra (very solid ) tripod that makes my ED80 ultra stable . 

That looks very classy I must say. Is it light enough to pick up the whole lot to take outside?  I like the right angle finder. I bet that helps avoid neck ache. 

1 hour ago, vlaiv said:

They actually use two sets of 1D + temportal information to construct 2D+time, right?

Does scattered light "freeze" frequency at the moment of scatter? I'm trying to figure out how chirp plays into all of that - it is probably combined with diffraction to separate different moments, but I'm failing to see how that would be possible if scattered light continued to change in frequency with time.

There you are - try this paper. Single-shot compressed ultrafast photography: a review.  Bits of it are quite readable. 😀.  I admit that I don’t grasp how the digital micromirror device they mention allows them to reconstruct the spatial and temporal information.  It’s clever stuff though. 

51 minutes ago, vlaiv said:

Yep, that part is evident.

There is one more detail, that I might have gotten wrong - it took 8 hours to "analyze" the recording?

Yes. I’ve skim read some review papers in this field over the last half hour or so. It’s not immediately obvious how this technique works.  But I think I can sort of see that they use imaged chirped laser pulses to encode wavelength information with temporal information. They then use two cameras - the streak camera and a cmos camera - plus a whole load of processing to get back temporal and 2D spatial information.  The frames per second thing is slightly misleading. It’s more like an equivalent fps. 

12 minutes ago, vlaiv said:

How can such device be used to record 3 dimensions? Two spatial and one temporal?

Two dimensions (1 time, 1 spatial ) is easy by focusing an image along the slit of the streak camera. The slit is perpendicular to the scanning electrodes in the streak camera. At the back of the streak camera is a phosphor screen attached to an image intensifier. The output of that is coupled to (these days) a cmos camera which provides a two-dimensional image - time in one direction, spatial in the other.

How do you get the other spatial dimension is the question. I can see this can work easily if multiple laser pulses are used. Basically you could scan the subject or laser or imaging system up and down.  However, I believe some of these techniques work with a single laser pulse and I’m not quite sure how that’s done. 

Incidentally, as explained in the video, the image of the figures is provided by a conventional camera. 

11 minutes ago, vlaiv said:

When you say this, does it mean:

- you can record event that lasted sub-pico second with this type of camera

or you are saying:

- you can record event that lasts sub-pico second, every sub-pico second with this type of camera?

I would say yes to both of those. Here’s a link to the brochure for a Hamatsu streak camera. They show there a picture of a series of sub-ps pulses repeating every 10ps or so. I guess they’ve used an etalon or similar to produce a comb of pulses like that.  So if for example you used a single light pulse of 50 femtoseconds duration to excite some emission in a sample lasting a few picoseconds (say) you would easily resolve that event with such a camera.