CraigT82

Yeah without a doubt a bigger beefier dovetail is needed with wide ring spacings or with big tubes, I’ve only ever used losmandy style plates with my Fullerscope or my 300p. 

As a user of large newts I often wonder about this.

I imagine holding a long stick in my hands, holding with hands wide apart would allow you to resist externally applied forces (e.g. like wind gusts on the OTA etc.) better than holding with narrow spaced hands, hence I’ve always gone with widely spaced rings. Also I think as the weight of a newt is concentrated at the ends then wider spaced rings would resist flex in the tube itself better too. 

Saying that I’m not an engineer and am just guessing really.  I’ve seen a few pics online of large/long scopes with closely spaced rings and I’m sure I’ve read something somewhere saying that closer spaced rings were better but can’t find it again. 

I wonder if there are any mechanical engineers on here who could share their thoughts? Following with interest! 

I also use a neutral density filter on my 12” as the image of Jupiter is very bright even at high magnification. Unfiltered it kind of looks like an overexposed image and hard to make out any detail

The ND filter is a bit like wearing sunglasses on a bright day and looking wispy clouds on the sky, it takes the edge off the brightness and allows you to see more detail in the wisps (if you get what I mean - not explaining very well)

I’d much rather have the heritage 150 under a good dark sky than the 200p dob under a light polluted sky. I say get the heritage. For what it’s worth I have the 130 heritage ad I love it. 

That’s a good point… you could just run off one long 30 min capture and chop it up as necessary in PIPP

1 hour ago, neil phillips said:

Without seeing the Chris Pellier blink test. I think most wouldn't consider 3 mins as something viable. Over time I think i can see its effects. As a slight softening. But only when someone has perfected other things in planetary imaging. Would it be worth worrying about. I do prefer 5 min de rotated vids for sure. Often i run off 3 min vids and when i think ive nailed focus and everything is looking stable. i start running off 5 min vids for winjupos. It works for me. But yes that blink test is a real surprise for sure

Looking at his 3 min test between AS2 only and winjup derotation I must admit I can’t really see any difference between the two blinked images, not on my phone anyway. The 4 minute test at the bottom of the page has obvious differences though. You don’t really see any of the specialist planetary guys running 3 min captures but, remember the OP asked about a 6 inch scope and I think 2-3 minutes will be fine for that (in my opinion).

19 hours ago, symmetal said:

I would actually say that anything over 0.5 pixel movement during the video would cause actual noticeable blurring in the stacked image. 🤔

A quick way to calculate the max video duration without worrying about angular resolution etc. is to measure the diameter in pixels of your Jupiter image. Lets say it's 300 pixels.

Circumference of Jupiter would then be 300 * PI = 942 pixels.

In 10 hrs (36,000 seconds) a spot on Jupiter's equator would therefore move 942 pixels

It will move 0.5 pixels in 0.5 / 942 x 36000 seconds = 19.1 seconds.

So it's proportional to Jupiter's image pixel diameter and the amount of pixel movement you're willing to accept.

Alan

Maybe half a pixel if captured with perfect optics, perfect collimation, perfect focus and perfect seeing, but in real conditions I disagree. 
 

I agree that it’s down to the observer and what amount of rotation they’re willing to accept though, and of course the sampling resolution.

I personally use 60 second captures with my 12” newt and they work out well. I think next time I’m out I might do some testing along the lines of that Christopher Pellier did in Neil’s link and see what happens. If anything I think AS3 is even better than AS2 at dealing with rotation, both field and planetary. 

On my old 200p the first time I took the mirror cell out I had to use a large flat bladed screwdriver as a drift and tap it out with a mallet as it was really stuck in there.   There was just enough of a lip where the cell meets the tube to get the screwdriver onto.  After that first time it got easier. 

Stopped using Registax a couple of years ago and switched to Astrosurface. It does everything Registax does and a lot more besides, including deconvolution. 

The maths for this one isn’t difficult, as long as you know a few key parameters.

Jupiter is about 450,000km around its circumference and rotates once every 10 hours ish. So a spot on its equator moves at about 12.5km per second. At a distance of 600,000,000km, 12.5km per second gives an angular distance travelled of 0.0043” per second. 

With a 150mm scope you’ll be sampling at 0.25”pp let’s say. 

So it would take 58 seconds for a spot on the planets equator to move from one pixel to the next, but to actually be visible in the image as blur it’d probably need to move at least 3 pixels, so there you have it…. 3 minutes! 
 

Same here on a trip to Tasmania. Upside down Orion and also the moon really is weird to look at. 

1 hour ago, vlaiv said:

Yes, it does seem to contradict original document - and also common sense

Well I wouldn’t say it’s common sense but I get your meaning 😂

There is some more in depth explanations further into that paper in section 7 but it’s all Greek to me. Maybe the inventor of the process has embellished it’s capabilities slightly in that paper, wouldn’t be the first time that’s happened! 

Looking at the first document linked to in that APP thread it says this about Drizzle and it’s influence on noise, which seems to contradict that quote from the handbook? I’m probably misunderstanding,  I admit I haven’t read the entirety of either document.

Really nice result 👍🏼 Amazing what can be done with a manual dob 

Yeah could be possible in AS3, using the surface mode and with strategically placed alignment points 

Are you sure the guidescope is moving and not the primary mirror? That’s the issue I had with my 8” f/6. Solved with an OAG. 

Well I guess it depends on what you’ll be using it for. 

If planetary/lunar/solar the higher read noise of the ASI compared to the P1 won’t matter much as with the strong signals from those targets the shot noise far outweighs the read noise (except perhaps on Uranus or Neptune).

Personally I’m looking at doing DSO lucky imaging - stacking thousands of 0.5s to 1s subs - and so the read noise is critical. I would choose the P1 camera for that over the ASI. 
 

Not sure as to the why. They must have a reason for changing the HGC point but I don’t know what it is.  

On 31/08/2022 at 01:48, Adam J said:

and here is the answer,

https://www.cloudynights.com/topic/779874-imx585-chip-coming/page-2

Looks like Playerone modified the HGC read mode of the sensor so that it kicks in at a alower gain and ZWO have not. The sharp cap results above effectively confirm this.

Not sure they can modify that in drivers or not.....

On that basis I know which one I would buy.

Edit: for the noobs its the player one.

Adam

 

Sorry only just saw your posts, not sure how I missed them must be getting senile in my old age.

Thats an interesting thread, it seems that the early 585 cameras ZWO produced had the HGC kicking in earlier but then the changed it to 252 so that would explain the charts on FLOs listing. 

Also interesting is the post about US dealers getting pressure from a certain camera manufacture not to carry player one cameras, could explain why no one carries them here but starfield. I know business is business but this isn’t a good look for this other camera manufacturer.

40 minutes ago, Dark Raven said:

Not sure where that comes from but I just checked their product page and it states 252

So it does… In that case are the ASI585mc charts on the @FLO website for the wrong camera???

That now raises the question (for me at least) of how Player One are getting much better read noise performance from the same sensor than ZWO? Also ZWO claims 47k full well and player one claims 39k but are getting better DR.

I’ve just had a look at a couple of other M31s and they look the same, so it’s probably just my phone display, apologies!     Looking forward to seeing the result (on my monitor!) with the RC10 data added

Wow…some nice detail in the dust lanes around the core.  Is the background sky black clipped? Might just be my phone screen. 

With the 300p last year I was using an APM coma correcting barlow operating at about 2.8x (with my QHY462c) and this year I’ve got a Tevelue 2x barlow and with the ADC between it and the camera (ASI485mc) it will operate at about 3x.

Like Neil I tend to oversample, but I’m not too fussed about the sampling really as long as it’s in the ballpark. On the list of ‘things that will ruin your images’ the exact sampling is way down the list in my opinion. 

Actually whilst we’re on the subject, one benefit of using greater barlow power than is strictly necessary is that you get a larger diffraction limited field size and so a bit more tolerance to collimation error. With a long imaging train and a newt with thin flexible tube wall that is not to be sniffed at. 
 

Edit: just thought I’d add this link to a tweet with a Jupiter image, captured with a C14 at F/25 with 2.9um pixels. It’s massively over sampled but has that ruined the image?  Could the image have been better if sampled more sensibly? Possibly. But my point is that oversampling won’t ruin your images, but bad seeing will, thermal issues will and focus error will.

Really nice! Europa and it’s shadow are pin sharp, love that. 

3 hours ago, neil phillips said:

Its good your asking the question Craig. My very simple blur on the edge not too obvious then. The rind will be a given for the most part. I wonder sometimes if to just leave it. But either approach is fine. And yes Craig the 245mm Newtonian. Do you still have the 300p ?

Yeah I wasn’t sure, it just looks like Martian clouds to be honest you’ve done a good job on that. Yeah I still have the 300p it was stripped down last year but it’s been put back together now and just waiting for Jup to be in a decent position around 11-12pm to get going with it as early mornings are a no go with the kids at the minute