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The constraints are: needs to be operable in a 2.1m dome, plus no more expensive than an 11″ RASA and with at least as much light grasp. I’m using an EQ6Pro, so I know I probably need to upgrade to an EQ8 – though I kind of hanker after a MyT as I have found MEIIs a joy to use, but too damn expensive.
I like the RASA that I occasionally use – a lot. Its given some great wide FOV images, but I’m not really planning to spend all my time going after large sprawling nebulae and find I tend to image smaller objects and so end up cropping the frames hugely. Obviously, a 14″ RASA would be better with more light and a smaller FOV) but they are $12k so thats not happening and it might not even fit anyway
The balance point on open truss systems seems further away from the tube midpoint to me (I could be wrong) and with a 2.1m dome I’ve got to be really careful hence ignoring them at present.
I had the opportunity to use Meade, Celestron and Skywatcher 12″ Dobos next to each other about 10 years ago. None of them gave a less than nice image though, one did excel – I need to go back and find my notes to remember which it was.
A lot of you will of course have bought new telescopes frequently, but for me this is a new experience. I bought an 8″ f8 Fullerscopes second hand in 1985 and a used 10″ AE f4.3 Newt in 2002 and thats my lot, so you can see, the instruments I have used most over the years have been old-school. I did have more ambitious plans but, as always seems to happen, events occurred (chimney in need of a complete rebuild and new car needed) which suck up the spare funds. Probably just as well as a 3m automated dome, Paramount MEII, RASA 14″ and QHY600 would dent the bank account somewhat and cause plaintive wailing from my bank manager.
Thats interesting. I had forgotten the TS scopes. Happily you and someone else have reminded me. I’ve no idea what the quality is like so I shall look into that as I had assumed (erroneously) that they were daft expensive.
I have wondered about the 300PDS from Skywatcher. The focuser is a bit heavy (I used a 130mm version a few years ago) as I recall but given I only have a 2.1m dome to work with, that may work in my favour in countering the mirror weight… The Quattro isn’t bad in that respect.
The PowerNewts are worth knowing about – I imagine collimation could be fun. Thanks
Thats nice to know. I bought a copy for work several years ago and Willmann-Bell were massively disinterested and unhelpful when I said I needed to use the code on an air gapped machine. They never solved the problem and just stopped answering emails.
Some very good books, but not good at customer relations.
Perhaps some of the books will end up on print services.
Thanks for the reply. I had wondered how much better sigma clipping might be. Looks easy enough to implement.
I have wondered if the skewness of the sample pixels could be calculated and that used as a threshold for pixel removal – though I suspect that might be more computationally intensive than sigma clip.
I shall have a play on some data I’m working on.
One minor tweak….
You say that you need the outer annulus mean value and standard deviation. But, in cluttered fields, does using the median value help protect you from outliers?
I did my first variable star measurement in 30 years.
Result: 20201009 01:27 Mag=14.1 (first crude estimate using AAVSO) while AA7 says 13.94. What does everyone else use?
Refined result using Gaia DR2 plus another from the following night…
20201009 01:27 2459131.60262 14.05
20201010 00:21 2459132.51466 14.30
Managed to catch it around midnight during a brief clear very transparent slot following the swirl of cloud that caused such heavy rain yesterday afternoon. The coldest night of the autumn here so far. Was 4C by the time I closed down – must bring the geraniums indoors.
It really is very faint isn’t it? When the other lobe of the nebula is the brighter of the two then you know its dim.
The faintest I received in our study – August 2009 – was 18.75, so we’re in unexplored territory.
Am kind of hoping it ends up repeating the cycle we observed, so we can say its got an 11 to 12 year cycle, but thats probably too much to hope for. 🙂
W10 has the option of sacrificing appearance for performance and also choosing whether the beneficiary is the applications you use or “background services”.
Would it be worth looking at those and trying different settings? Just a thought given that the system clearly can work without the interference.
Also, have you tried using the camera with your anti-virus turned off?
One question: is your camera a USB camera or a serial camera with a USB adaptor? Cannot vouch for those.
I’ve used: Lodestar, Superstar, Ultrastar, SX H18 and Trius 694s on a USB3 under W7 and W10. No issues.
However, if there is a problem, then if your laptop takes Expresscards, you could perhaps install an old USB2 card.
I discovered the Python Wikipedia entry this week. Highly entertaining reading. About the only thing it doesn’t do, apparently, is turn water into wine – well, thats what the zealots appear to think it seems.
Could you tell me what sort of circular polariser it was please? Am sort of surprised it was so successful against the linear signal from the comet.
Is it one that normally fits on a DSLR camera lens?
Really nice to see this.
The comet is approx 30 degrees from the sun, so the background should display Rayleigh scattering induced polarisation of a few percent. From memory, the orientation in the first image looks roughly right given the suns position pretty much below the north horizon. The comet should have its own dust response – as the Zodiacal light does – and certainly appears to here. I’m a bit perplexed by the orientation of the background polarisation in the second image though. Was the amplitude the same?
Your amplitude measure, was that a Stokes parameter or the degree of total linear polarisation or similar?
I imagine perfect alignment of the 4 polariser images is essential to the values measured when the target has fast changes in brightness. I have always had greatest problems getting good results in parts of the image with steep gradients – subpixel registration is important (I found to my cost).
I assume you only used linear polarisers.
Thanks for the clarification(s) on why you seemed to object to the device. Nice to understand the rationale. I must admit I rather liked the idea of using the PHD slit option. Seemed quite sneaky but can see why a mirror system might work better.
As you say, it ideally needs someone impartial trying both and seeing what works best in practice.
I wondered if any internal reflections made it visible. But and x/y cordinate should be enough really.
