Pompey Monkey

Passion friut!

I quite like that pallet.

I know you probably have been told this, but a 1000 mm telescope at very close to the manufacturers (optimistic) payload capacity of an heq5 is always going to give you headaches.

The pain of paying once for a better mount (eq6 minimum), while intense, will fade into the past and soon forgotten about when it works every time.

The chronic discomfort of having to constantly fettle your current mount to perform to your satisfsction will, however, slowly sap at your soul for as long as you continue using it with that scope.

On 18/12/2021 at 02:02, Malpi12 said:

@lukebl Beautiful obs., well done and I envy your clear spell total cloud here
So I was reduced to armchair playing with your result :-

I copied your plot into gimp and measured the entry/exit , mid and total durations in pixels, and also the 10sec width(308px)  :-
238/308x10=7.73sec
222/308x10=7.21sec
216/308x10=7.01sec
Give or take a pixel or two it looks like you were on or near the max center line !

The trojans @Stu are in the same orbit as Jupiter ( at the L4 and L5 Lagrange points 60deg ahead and behind ) round the sun so it should have the same orbital velocity as Jupiter (mean 13.06km/s according to wiki).
So I should be able to get from that to an estimate of its diameter.

7.73x13.06  gives 100.95km
7.01x13.06 gives 91,6km
Hmmm, I think I have gone astray a bit, or maybe I need to find the min. orbital velocity.

That was fun ! quite interesting, not a million miles off the 63to71 km dia in the header of the pic in post#1 of the ground track.

I think that you need to take the Earth's orbital velocity (approx 30 km/s IIRC) into account in your calculations.

In fact, on the (simplistic, but not unreasonable) assumption that the line of sight (LOS) between the star and target is sweeping across the solar system at the same speed as the orbital velocity of the asteroid, I think we actually caught up and overtook the shadow!

There is also the Earth's surface rotational velocity to factor in, although this is a lot slower than our orbit.

And what about the relative motion between the Solar system and the occulted star? I'd hazard a guess that this is pretty small, but someone, somewhere, has probably included it in their calculations...

I think we are being spammed with "new members".

Apologies if this has already been sorted out.

6 hours ago, ollypenrice said:

Now there you have it: someone starting out has, in my view, enough to think about without setting themselves up for further preventable mistakes. Keep it simple. 

 

I agree, at least on the basics:

I'd encorage anyone to least learn some of the constellations before heading out into cold to bury their face into a computer screen...

The star images taken with the 200 mm lens are elongated by camera shake.

However, the spikes in the Tak image show definite chromatic abberation which is very much an optical effect.

I think the two issues are completely unrelated.

Did you have a completley unobstructed view of the target? A washing line or telephone cable in the line of sight could cause this effecl.

On 30/11/2021 at 17:35, Philip Terry said:

Hi All:

I've been taking images over the last few months and I've just noticed some undesirable spike sillhouettes in my images of bright stars, particularly when I do a close crop to expand the image. It was really striking  a couple of nights ago on a shot of M42; I attach a blow up of a region where the brightest star in the field shows 2 "dark beams" shooting out of it. The telescope is a Zenithstar ZS73 with 0.8 FF/FR and the camera  is a Canon 600D.  (The flattener probably needs a bit of adjusting, corner stars on the full-field image are a bit elongated and streaky). This is a stacked image of 24 x 90 sec exposures, ISO 800 unguided, processed throughot using Affinity. I'm not desperate to produce perfect images, and I'm really pleased with what I've taken so far, but I'd like to solve this. I've used a torch to peer up the optical train but can't see anything untoward. There are a couple of machined notches in the rim of the flattener towards the midpoint, but these look part of the item and face forwards so it would seem odd if these are having an effect. Any suggestions would be welcome! Thanks, Phil.

 

If you are seeing "lower order" artefacts in your images, it means that you are doing great!

18 minutes ago, Grant93 said:

A really nice change! Brought out a lot more of the background! Thank you!

You are welcome.

Processing image data is not easy for me. I am only learing how to "see" what is going on in an image after over five years!

The technical side of aquisition is totally clear to me, as I have an engineering background.

However, knowing what to do with the data to make a nice image is a struggle for me. I'm getting there. lol.

Patience is soooo important in this hobby, as there is so much to learn, but you will be rewarded if you persevere!

You are off to a great start :)

35 minutes ago, Grant93 said:

Hello everyone!

Always posting away in the getting started with imaging forum, felt its about time to be brave enough to post here 😅. I hope its a worthy image. A bit of a story - Had this 135mm Lens for a while, not fully understanding or appreciating how fast it was, I use to think my backyard skys were too polluted for it, I use to stop it down considerably so I could get 'longer exposures' without overexposing the histogram. I don't know how or when it hit me how silly this was, but I finally understood the love of RASA's and the fact you don't need them long exposure times, just open the damn thing up and shoot for as long as it doesn't overexpose, whether thats 20 seconds or 120!

It didnt dissapoint, this is probably my second or third cleanest image to date, but with 2-4 hours less total exposure, because this was shot at f2.8 compared to f4-f5. After the first result of processing, I was impressed and wanted more data to try and bring faint dusty regions out around it, sadly I think I've failed at that. I added another 2 and a half hours data, but it doesn't seem any easier to process, and even added difficult gradients, I will try scouring through the images, getting rid of bad ones and restacking on the weekend. However I am too eager to hold my image back as it is one I am rather proud of considering it contains less than 2 hours data, unguided and not dithered (This will change by christmas ).

I am rather happy that I managed to pull out some dusty regions to the top right and bottom left - Will a few hours more intergration time be able to pull out a lot more from a bortle 5? Or do we need 20 hours+ for that dusty detail from a bortle 5?

EDIT: Please please please, give me plenty of constructive criticism

Heres the details;

Modded 600D

SGP

Samyang 135mm @F2.8 (Heard it was sharper than F2.0)

150 Lights @ 45 seconds

20 of each caliberation frame.

 

You have some nioce data going on.

A quick ABE and a (small) stretch in Pixinsight:

I don't  have a Mesu, but I applaud your efforts to get away from USB connections.

Unless captive at both ends, the connector technology is pretty much unsuitable for moving parts.

Alas, we have all been pushed down this route for convenience and/or cost over the years. Now we are stuck with it!

You need to be pointing somewhere near the celestial equator for the calibration to work (after polar alignment, of course).

Pointing at the celestial pole to calibrate, like you were, will give wildly inaccurate results. Because maths.

Good luck!

You should do...maybe then we'll  get some clear skies! 🤣

Yes, the blue is interesing!

2 hours ago, StuartT said:

Hmm.. thanks for this. But it sounds like I'd need to actually open up the laptop and change some hardware to do this, right? If so, I think that's a little above my pay grade.

The chips are in the cables!

So no need to disassemble anything

19 hours ago, StuartT said:

 

As for USB woes, I totally agree! My laptop annoyingly changes its mind about what number to give the COM port every time I connect up! 😡

 

The easiest remedy for this is to only use USB to serial adapters with FTDI chips, NOT the Prolific brand.

FTDI "remembers" the correct COM port regardless of which USB socket is used, while Prolific doen't.

Believe it or not, the reasons are due to hisitorical issues with IPR piracy!

On 12/11/2021 at 20:29, tomato said:

It was (I hope) the official Risingcam store on Aliexpress. I paid by credit card for some level of protection but the process all looks good so far, order status info as good as anything I've seen on UK based sites. Camera should be in the UK by the end of first week in December, then we'll see what import duty there is to pay.

The import duty will be calculated based on the "declared value" of the package. 😇

Thanks for the heads-up.

35 minutes ago, Piero said:

if I'm going to refactor my 12" f6 Lukehurst dobson, I will use metric units from the very beginning.

In that case, surely it's a 304.8 mm f6? 😇

1 hour ago, Zermelo said:

Give me any thread subject, and I guarantee to (mis)direct it eventually to Doctor Who ...

Much more civilised than Godwin's Law!

9 minutes ago, Alan White said:

just make sure you put on decent socks and shoes.

And trousers.

2 minutes ago, Zermelo said:

That sounds just like that fictitious road in London that the map company put in, for the same reason.

 

I saw this on telly once. It used to happen quite a bit.

I have thought about randomly removing a star from each of my images for this very purpose. But then I realised that no-one would want to rip them off anyway....

18 minutes ago, Zermelo said:

You forgot chains! Still very important to some people.

Why did you have to bring up chains to complicate matters further?

That's just not cricket, old chap!

25 minutes ago, Carbon Brush said:

This evening I might relax with a 0.568 litre glass of beer.

Nah!

You should just roll over and give them their 0.454 kg of flesh...

I'm getting increasingly peeved at constantly having to swap between metric and imperial components, nuts, bolts, and tools on my rigs. It can really interrupt my train of thought while assembling stuff.

And, as for planning how to make stuff that includes both measurement systems, it's nigh-on impossible.

Just venting!

20 minutes ago, vlaiv said:

You really should not get too hung up on bit count - it is really not important if you handle your data properly. Many people use ASI1600 and produce excellent results - and it is only 12bit camera.

Each time we stack - we increase bit depth of final stack, so even 12bit camera can easily produce 20+ bit precision image.

This is particularly applicable with many short sub-exposures compared to fewer longer ones. So it's another win for CMOS.

BTW the extra 8 bits of resolution would require a minimum of 256 subs - that's a lot of storage and CPU demand.