Whirlwind

Doesn't Sharpcap use PHD for guiding - isn't the function in there?

As for darks what is the issue as darks are just the same exposure/temperature with the lens cap on (assuming no light leaks)?

As noted above this looks like "Walking Noise".  It's caused by fixed pattern noise on the CMOS camera that can't be corrected using dark frames.  Again as noted you have to use aggressive dithering to remove it.  This 'blurs' the noise across the image in an areas rather than rely on slow drift to remove it during processing which was more commonly relied on for CCD images.  I speculate that that the difference between a 2min / 5min exposures is that for some reason 2 mins is more heavily dithered and/or is generally more noisy so hiding the issue (rather than not being there).  For the 5 min exposures other noises sources will be lower (relatively) and/or there will be less images being dithered because of the longer exposure and hence more aggressive dithering is required. 

There's always going to be some sacrifices because of the number of restrictions.  From what I can tell these are what you might call portable:-

SXD2/SXP2 (as discussed)
Ioptron CEM40 (and smaller already noted)
RST-135 (already mentioned)
Crux140 (13kg imaging payload, similar concept to RST135)
AstroTrac 360 GEM (Just enough payload for requirements at 10kg)
Panther TTS160 (above value threshold and individual components may still be too heavy)
Avalon Instruments M-Zero (only 8kg capacity for individual 'scope)
Losmandy GM811G (fits all criteria?  Also the GM8 for less capacity)
Fornax Lightrack II (stated as 12kg max payload with c/w but have no experience with this type of mount, I think the max imaging time is limited to about 100 mins before a rewind is needed).

I can't think of any more?

10 hours ago, saac said:

I wonder if what we are really missing is perhaps what many of us (in UK at least) grew up with.  Where is the weekly programming of science and  technology,?  Come on BBC a return to the days of Tomorrows World  or decent Panorama /Horizon  documentaries.   I'd hazard a guess that these were the programmes that influenced many to follow into science and engineering.   As much as I love watching the "Repair Shop"  that doesn't really cut it . 

Jim 

I'd agree.  I guess they cost more money than the 'tripe' that is the "One Show" or "The Wheel".  Educational programs (doesn't just need to be science) is generally left for late at night or BBC2/3/4 etc.  Just replacing one episode of the One Show each week with something a bit more aspirational would improve things considerably.

1 hour ago, saac said:

Nothing romanticised about it whatsoever . I was referring to the possibility that a career in science/ technology can be as equally glamourous and desirable as any other and that is the positive message kids need to and do hear.    Wow , "just become a teacher"   -  there is motivation for you lol.    Thankfully, you are wrong  about the next generation being put off , certainly has not been my experience .  But hey I am "just a teacher" lol .

Jim 

I didn't mean to sound condescending to teachers, I apologise if it came across that way.  What I was trying to express is that once 'reality' comes into the frame and there has to be a choice about what you want to do then the lack of certainty will drive most away from doing pure science work (for most children this reality is unlikely to be known, they just the see the glamourous side etc).  Simply that being a teacher is more stable as a job and ultimately tends to guarantee a career whereas the post-doc path is littered with people that for one reason or another didn't get the same opportunities to make it permanent.  This ultimately leads to them having to find another career and generally work there way from the 'bottom', so losing up to 10 years behind their peers in the 'replacement' career.  These may well have been excellent scientists but for one reason or another simply didn't get the piece of luck they needed. 

14 hours ago, saac said:

There is the incentive for current S6 pupils considering their university options, good to see a real scientist holding their own with the "gliterati"    That said, I consider that Cox is underpaid  though compared to the other presenters. 

Unfortunately this is rather 'romanticised' when faced with reality.  B Cox is paid this amount as a presenter (noting it also probably excludes travel expenses etc) not as a scientist.  

In the 'normal' astronomy science world.  You have post docs that will earn £30k as a starting salary (maybe increasing to £35k with experience).  These are all 1-3 year contracts so if you win one place you are almost immediately looking for the next post.  You are also competing with people that to put it mildly are obsessed so you to maintain an research output to give you a chance of a permanent job you are looking at putting 60-70 hours (if not more) during these placements.  The general wisdom is you are expected to have done 4-5 posts docs before you'd even be considered for a permanent position (with the exception if you win an award that brings in a substantial amount of money for the Uni - in effect they are bribing you to not take the award elsewhere).  If you are then 'lucky' enough to get a permanent position then that's a £40k - £50k salary.  Again if you win enough you may then end up with a professorship (£100k+).  It's a very shallow sided pyramid though - there are lots of post-docs, a lot less permanent positions, and a lot less professorships. And even the latter will be paid less than B. Cox for presenting a couple of series of programs.  What is really needed is a much more structured career progression that, arguably, is less exploitative.

To put it into context you can earn more as a HGV driver these days (£50k with experience) or even a night shift manager at a DHL warehouse (£40k advertised in Leicestershire recently).  You can even just become a teacher £30k starting (but permanent position).  Hence holding up the above salaries as something a child could achieve is not realistic (it's a bit like telling a child that by learning to sing they could earn as much as Rihanna etc) - yes it is possible but there are 100,000's of people that are excellent at it but ultimately don't because their 'face/voice doesn't fit'.

B Cox earnt enough in those couple of shows to fund 7ish post docs for a year etc which is what I find most galling about this sort of thing.

21 hours ago, Macavity said:

But PART of me still HOPES? To *some* extent, international organisations
like CERN (Hey, it was not perfect!) try hard! To be frank, my return to the
UK (UK science!) was something of a personal... and "political" disaster. 😑

The visible presence of UK Science is still about (BBC) "posh people"? lol.
But if I can inspire anyone to try to be a (Thicko? lol!) Particle Physicist! 🥳

I'd always support in getting more people into science - it's just a shame that the reality is that most next generation Einstein's are put off before they even get onto the ladder.

5 hours ago, Macavity said:

Re. (2) You are right! If I could keep away from "social media"? But I still feel that Prof.
Cox might BETTER USE social media for promoting Science, rather than "Remoaning"
and/or Re-Tweeting "CERN stuff"? It is certainly the THE RIGHT of Scientists to FULLY
express an opinion on Religion & Politics (Philosopy!) But I do TIRE of these people...  😑

Science is highly politicised though - you aren't likely to find many 'pure' scientists (i.e. those that don't have business backing with a profit based orientation) that disagree with his political views etc.  It is driven by a funding system that is largely insane and a lot of excellent scientists don't get there work funded.  His online presence isn't about educating its about supporting an agenda for either your own or the university's research.  We are still in a position where if you bring money into a university and if you can self support yourself when you don't get publicly funded that helps massively (which B Cox is able to do because of his musical past).

Historically for pure sciences funding has come from the university itself, the UK science council and the EU schemes (of which the latter had made up about 50%, and maybe greater, of all funding for Astronomy).  The UK generally funded private research businesses (the Rolls Royce mini reactors is a good example of this).  Pure science funding from the UK tended to come in the form of supporting individual Post Doctorate (and occasionally reader positions for a few years).  There is usually a restriction though that you can  submit one/two submissions from a department - so when you look at it analytically the lions share of funding proposals tended to go to the groups that were headed by the Heads of Departments etc.  The same goes for internal university funding which tended to see the lions share of funding go to whichever department the Head of the Science College was from.  Ultimately you end up in situation where money = more research = 'success' = control = money and so on.  The difference with the EU system is that it isn't limited int he same way and usually allows for much bigger bids (for example £1m+ is not unheard of).   This allowed for post docs/phd students that might not have been funded to get some support for their science.  The UK massively benefitted and for the money spent by the government got a huge return.  This option is much less available now - we now have to be more partners, rather than lead universities and at the moment there is a lot of 'caution' in partnering because of the 'shenanigans' and that it is less easy for things like sabbaticals (spending a year or so at another uni but your home uni pays for it) to undertaken.   

With funding much lower than it use to be it should not be a surprise that B Cox is politicising certain issues as that will be part of his job at the university as fundamentally it is get more money for their specific research etc.  So you shouldn't see their posts as for the 'benefit of mankind and education' to an extent.

6 hours ago, The Lazy Astronomer said:

I'm all for experimentation when it comes to things like this - that is the scientific method after all.

I look forward to seeing the finished product 👍

To an extent, but that doesn't mean you will get a different result.  A rather vacuous example is that we can all jump of a 30 floor building to 'test' gravity but we all know what the end result will be etc.  I tend to recommend these two youtube videos as they explain why just running very long subs doesn't always add a benefit to imaging.

Deep Sky Astrophotography With CMOS Cameras by Dr Robin Glover - YouTube

Choosing the right gain for Deep Sky imaging with CMOS cameras - YouTube

13 hours ago, raadoo said:

It's a fair point and one I've personally made to others in the past as well. We do need to define a few parameters before moving forward with this thread:

• Long-term Mount: I'm thinking 3-5 years. Past that, I'd be looking at what I call a Forever Mount (e.g. 10Micron)
• We can always extend the idea of if I'd only been a bit more patient more and more. And with it, budget. But a line must be drawn. So I'll extend that waiting to your proposed 6 months and up the budget to under €4k.

That being said, I have very little knowledge of that market or what's reliable / flaky, so any recommendations and ideas are very welcome!

It doesn't have to be and it really depends on what you want.  All I can go on is from my own experience.  I went from a CG5 - Vixen SXD - Mach1GTO.  In hindsight I would have probably been better to have gone straight to the Mach1GTO based on what I wanted to achieve at the time.  Nevertheless the SXD (although not planned) still provides a very useful 'holiday' mount as it is much more portable than the Mach1 (so I still have it).  The Mach1 is probably my forever, but not in an observatory mount.  When I get my own house in the countryside, in dark skies etc (I wish) then I will plan for an observatory mount....lol  Although if your current mount is on its last legs than you may be pushed into that earlier decision anyway (it really depends on why you want to upgrade).  But I do take the point that you can't wait forever otherwise you will never get anything!

I'm not sure why you need to do this?  Because of the sensitivity of the camera, low read noise, fast optics you aren't going to gain much compared to much short exposures and stacking them - it might even be worse because your background is much more impacted by light pollution?

Can't you just get the helical focuser for the OAG to make refocussing easier - only issue is I'm not sure whether you can get it to work with that style of guide camera?

14 hours ago, raadoo said:

After many hours spent tweaking and playing around with my AZ-GTi for the past year or so, I'm ready to move up to a more long-term mount and plead the wisdom of this fine group for some considered recommendations.

The question I would ask is whether you can wait and build up some funds if you want a 'long term' mount.  It will open up more (and better) options.   The only experience I have is with the original SXD (different software) but found it a wonderfully light weight portable mount.  There were some known software bugs originally but I never came across these.  However I understand the SXP2 is much superior to the SXD2 option these days.  You've already noted the RA-135E is out of budget but if you could wait 6/12 months would that become viable?  I always find the worst feeling is "if I'd only been a bit more patient" etc.  

3 hours ago, david_taurus83 said:

Is it a sensor issue? Ie could happen to other brands or just something to do with how ZWO have placed it on the board? What causes it? 

I believe it is due to the thermal pad on the back of the sensor itself and as it is heated and cooled it releases this grease which then 'leaks' onto the sensor probably by capillary action or similar.  It's not the sensor itself and maybe related to the aggressiveness of the cooling.  IIRC they are aware of the issue and have changed the pad so newer versions (hopefully) won't have this issue and is also why similar cameras don't see the same thing.  I believe that if you have this type of thermal pad it can happen at any time so it could be within a month vs several years - it perhaps could be more prevalent in warmer climates where more aggressive cooling is needed because the ambient temperature is higher (but is speculation).  Though I do thing it is a bit off from ZWO that they don't recall the affected cameras and replace the pad. 

On 27/10/2021 at 16:33, Staring said:

Did I miss any other suitable telescopes?

What about some of the Borg telescopes, they are collapsible so should be easily transportable as well being modular to meet different needs?

This is worth watching especially if you have AMD processors as W11 appears to hit them very hard.

There may be other causes.  I think this came up in discussion before (on a Chroma filter IIRC) and I postulated that it could be Newtons rings formed from a spherical surface and touching surface next to it.  For example I imagine the coverslip and the microlens of the CMOS chip.  It is wavelength dependent so may only be seen in narrowband (as broadband the effects at each wavelength would merge).  This should be testable as the equation is well known.

The alternative I more recently thought of was perhaps because of how interference filters are designed (Interference filters - Electronic Imaging - Bedford Astronomy Club).  From my understanding narrowband interference filters can have several layers of material in them.  If some of the light reflects then you can get light 'bouncing' back and forth between the layers if they reflect some of the incident light.  This could result in rings of slightly defocused light reaching the CMOS/CCD.  This would be more dependent on the thickness between the material in the filters so will be harder to determine as companies are less likely to release this information. 

1 hour ago, tooth_dr said:

It does look green and the Ha and Sii are red. Any suggestions on a test target, looking clear later? 

How about the Dumbbell Nebula as that has a distinct OIII component.  

Have you checked that the filter wheel is cycling every position correctly.  For example if is thinking it has 7 positions and is an actually an 8 position wheel etc.  Should be able to check this in daylight.  If travels in both directions you want to check it selects the same filter going backwards and forwards etc.

2 hours ago, vlaiv said:

Luckily it is a bit more easy than that. It turns out that our eyes work a bit like very low resolution spectroscopes - producing only 3 numbers instead of hundreds of measurements along 400nm-700nm range. Same is true for cameras - they also produce three values and it turns out that these three values are enough to reproduce (more or less accurately) original color.

In fact - we have very well defined XYZ color space that does exactly that - pretend to be very low resolution spectroscope that is compatible with our vision system and if you take any two light sources that produce same XYZ value although they might have difference on finer scale of spectrum - people will see those two as the same color.

With the exception that colour vision changes with age.  Our lens naturally yellows as we age but also there can be degenerative diseases that can affect our perception of colour (e.g. Changes in Color Perception | MacularDegeneration.net).  As such you may well find that some people 'boost' the contrast of their images to compensate (unknowingly).  I would expect that is some cases colour contrast is boosted less by a younger person compared to an older person for some colours.  As such you can never really use a person's eye as the low resolution spectroscope because each one is likely to perceive the colour slightly differently - in fact arguably we have no idea how anybody other than ourselves perceive colour because you can't plug yourself into someone else's brain.  To get a precise colour position you'd need to use specific energy levels.  

Really though it doesn't really matter what the colours are.  They are more representation of the data and what is going on in that location.  As long as the data itself is not being altered colour in the form we know it is just a perception - an alien species may not see it in the same way (lets say they see colour by change if brightness gradients) etc. You can make a star forming region red, blue, or luminous yellow as long as it is consistent it is still providing the same information.  In the same way that narrowband colour representation is usually 'wrong' but still provides real information on the object.

There are likely several factors here. We have effects like having differently calibrated monitors so colours can look subtly (or even widely different).  Then we have our own limitations - there is obvious colour blindness but also as we age I believe we tend to see colours differently.  As such as you age you might naturally adapt images to enhance elements so they are more vivid in certain colours but to the individual because their eye is filtering some colour it is more natural.  The reality is that the only way to do 'true' colour is to agree a colour for each temperature of an object through spectroscopy and then when you have sampled enough objects in the image apply that colour cast to the image.  However it does mean that with any imaging must come a lot of spectroscopic data.   

5 hours ago, ollypenrice said:

  We ordered it from a French website but it ended up coming from Wakefield!

Ooof, well given the problems in the UK transport industry at the moment I'd expect it sometime around the New Year....🤣

On 25/06/2021 at 20:58, woodblock said:

At present I use a Canon 450d DSLR and I'm looking at the possibility of buying a dedicated CCD or CMOS mono camera. My interest is in Photometry not imaging. Browsing the catalogues I noticed that most of the CCD cameras have 16 bit ADC's whereas the CMOS cameras have mainly 12 or 14 bit ADCs. It seemed to me that for photometry I would be losing resolution with a 12 bit ADC CMOS camera but I have a feeling that might be an over simplification. I wondered if anyone had any comments.

Cheers

Steve

 

The ADC isn't that important between CCD and CMOS overall.  For bright photometric objects either should be fine especially if it is for 'fun'.  The bigger issue (which comes more prevalent with faint targets/where changes are small (e.g. exoplanets)) is that you want a consistent noise on a frame by frame basis.  Here CCD currently still have the advantage.  CMOS have ADCs on their individual pixels whereas CCDs just have one.  It means that the readout from a CCD is consistent so when you create calibration frames the noise represented in them is the same as the actual science image.  In CMOS you can get variations on a pixel level (the proverbial walking noise effect that can be seen sometimes when stacked).  You can remove this by dithering in imaging but for photometry you don't really want to change pixels (ideally you want the target sitting on the same pixel(s) all the time as it keeps your noise values as close as to the same as possible).  

On 31/05/2021 at 15:17, Kitsunegari said:

The transmission graph on their website reveals zero leakage in the h-alpha range so it is a bit unusual;  almost as if this is intentional.   You can see the leaks all over the place as you say;  but this is pretty huge and  how could they miss h-alpha transmission with this large of a peak?  Especially for being "the best of the best".   

But it's not zero and this is where the problem lies.  Most astronomy filters have an OD value of 3 or 4 and for some science 5-6 (it's likely impossible to create one with no light leak).  As such if you have a very bright source (the flu tube) compared to the background then in an OD 3/4 filter enough is likely to be detectable.  On the other hand stars are much fainter in this regard so practically you may not need an OD 5-6 filter and is probably overkill for what we use it for.

This isn't really a surprise.  Most filters have some out of band transmission (this is usually referenced as their optical density (OD) value).  Even the best filters transmit some light out of the desired passband even if it is a tiny fraction of a percent.  If you put the filter in front of a very bright source then you will inevitably see the leakage (a fraction of a high luminosity can still be a high value etc).  Even Baader don't claim a perfect filter (you can see some leakage in their filter profiles). Nevertheless for RGB filters you use these primarily to obtain colour data of a broad ban image so some limited leakage can be OK as it isn't the dominant component.  Also you can expose on G2V stars to get a 'correct' colour balance (for our eyes) anyway which would remove any leakage impacts.  

1 hour ago, wimvb said:

The light gathering ability (efficiency) of an imaging system is proportional to (p/F)^2, where p is pixel size, and F is the F-number. This can be rearranged to (r*D)^2, where r is pixel scale (arcsecs / pixel) and D is aperture.

When @gorann and I processed images from the Liverpool telescope, we didn't need lots of data because a slow system , F=10 was combined with large pixels (30 um). When Göran switched to a RASA, he used a more common pixel size with a fast system. Again, he didn't need much integration time.

The optical resolution of the system is an entirely different matter.

I'd agree.  I've always thought that an imaging area per "/pixel is a more useful representation as to how 'fast' a system (as above) as there are other ways to increase the speed of your system through simple binning (excusing any noise differences from doing so)

2 hours ago, dweller25 said:

Just to upset all you refractophiles…….

My Skywatcher 10” Newtonian gave way better planetary views than my FS128 😱

A well figured, well collimated substantially larger reflector (including RCs and Cass's) should always be able to provide better views than a smaller refractor.   I don't think this should be in doubt.  Unfortunately because of their general size and that is easier to make good reflectors relatively cheaply means that there is a general dearth of premium reflectors on the market (both from an optical and mechanical standpoint).