dmki

Really nice work!

5 hours ago, gorann said:

Unclear to me why you think a CCD would be better to grab the details, especially compared to a modern mono CMOS, considering the much higher read noise, usually lower QE, dead pixels and columns that affects the CCD.

I am not.... i am suggesting that luminescence is where we perceive detail, so keep your existing mono ccd to capture luminescence and get a cmos osc to capture rgb... reducing your image capture times.

On 01/11/2021 at 06:54, newbie alert said:

So carry on wondering around your park at night, thinking about selling your mount for a low cost version and panicking about Mr musk and friends...

unfortunately we have an infestation of men with guns looking to bag about 80 bodies... so the night park wanderings are off for a while.

On 01/11/2021 at 12:37, DaveS said:

The QHY 410C looks to be a good match for my Moravian G3 16200. Use the G3 for Lum and NB, and the QHY for RGB. Haha, upper case 3 is £, so nearly typed G£ 16200 😆. Appropriate really.

I think this is the answer to anyone with ccd thinking of jumping into cmos, keep the ccd for mono to grab the detail of the image and  get a cmos osc to quickly grab RGB to colour that detail.

3 hours ago, DaveS said:

Money spent on a premium mount is never wasted.

You still need to give enough exposure to get your sky background above the noise floor, and for those of us living in reasonably dark (SQI 21.5 or better) areas that still means longish exposures.

sky background,  is that the stuff that lets me walk around my local park,  a mile or more from the nearest lamp, any time of night unaided?

thanks for the heads up about the 294, its on my list of sensors to consider.... when i feel ive learnt enough to do AP properly and what the implications of moving from a bortel8 can see where i am going by skylight day or night to a bortel10+ city are going to be.

@newbie alertThis is yes you can take loads of short exposures with ccd, the question is should you?
ccd's favour long exposures because the cells accumulate very little noise vs cmos.... but  make up for that with much higher read noise.
by taking those short exposures with the ccd you are accumulating an awful lot of read noise in the stacked image.

and as for satellites; those businessmen, as forum rules prohibit the language would normally use, have only just started deploying their low earth orbit satellite comms constellations and i fear that soon, a great deal of astronomy is going to be impacted in an attempt to make a few pennies for a very small number of people.

direct drive means that the mount/telescope are driven directly by the motor, with no gearing or pulleys between them.
in principle very simple, but you need to have a closed feedback loop for the drive electronics, thus you need encoders with a very high level of precision... which is a specialist item.
an interesting question would could you replace that encoder with synthetic encoder created from a combination of plate solving and star tracking?

to be honest i would be more tempted to build something out of, perhaps used, harmonic gears... high torque and low backlash

But best of luck with this, i am very interested in how it goes

true storage is cheap, but you would be courageous to put all that time and effort onto a single hard disk... mirroring help, but its not a backup, so you can be looking at maintaining 2-3 copies of that data... which does start to add up.

That cmos is optimised for many short exposures vs ccd, is a step change almost as significant as the move from film to ccd. all those techniques used by the planetary astrophotographers start to be come very practical for deep space, loose an image to a shortcoming in your mount, a satellite, a patch of particularly poor seeing and you can toss the image and just loose a few minutes of exposure.... rather than the 10's of minutes of ccd. And this is going to feed into the data storage requirements, just store the best% of your images and toss the rest.

Speaking personally, as some one just getting into the subject, I would not consider getting a ccd new or secondhand at any price, simply because of the cost of purchasing the necessary mount to get the best out of it. And for that dream setup I am thinking cmos lets me take money out of the mount and put it into improving field of view/acquisition times...

if i already had a ccd, if i could sell it for decent money i would do and move to cmos, failing that I would keep with ccd until there was a compelling cmos sensor on the market or i got annoyed with satellites, or short weather  windows making complete image collection a painfully slow process... 

i was thinking specifically of the 294 camera which use the Sony IMX492 and IMG294 sensors for mono and colour respectively. by default the are supplied bin 2x2, providing 11mp, however the mono version can be un-binned to 47 mp with a corresponding loss of wheel depth and dynamic range. I must admit that ive assumed other sony  sensors based on the same construction would also provide an un-binned mode... and we all know what assumptions can be wrong:).

Another difference between osc and mono, is the rgb filters, which tend to proper data filters with sharp crisp bandpasses are that RGB, whilst those in osc tend to march the crap band passes of human rgb retina dyes. I suspect that there is a reason for osc filters to work this way and its probably something to do with rendering an image which is as close to what we would see in the flesh.

which feeds into that our photos consist of three influences, the data(object reality), a desire to make a thing of beauty, our perception.... what that unique to you visual cortex does to the data as its converts it into sensation. In the case of that latter influence, there is a horizon program that goes into the detail
Horizon Do You See What I See Part 1-4

That's a very tempting combination

The 0.7 reducers are for the Celestron EDGE series telescopes, which have different optics to the other   Celestron SCTs which use the F6.3 reducer.

Then we have that quite a few of the higher end colour sensors each colour pixel is a  2x2 binned under the mask, so the mono version can be run a 4 times the resolution at the cost of well depth and bit resolution. And i guess for the right set of circumstances this could lead to a decent change in image quality.

The other issue being that you get multiple listing of the same advert.

suspect compared to machine vision and security astronomy sensors are a small market,  cmos is where those markets live and thats the commercial driver sending us to cmos. then obviously the lower read noise allows shorter exposures to be stacked, meaning a less demanding and therefore lower cost mount... and i guess the possibility of taking lucky imaging to deep space. I think now the only people using ccd are those who already have them and perhaps people getting into a few niches like photometry or spectroscopy.

i've got a 183 based osc and 178 mono camera for guiding and some optics experiments im doing. It occurred to me that an addional experiment that could be interesting, assuming i cannot just look up the answer... we tend to see resolution as luminescence rather than colour. so how much detail would you loose using a lower resolution RGB data to colour higher resolution lum. Just do both would be a fitting end to this debate

That looks great, I like the focusing mechanism, its an interesting alternative to using a timing belt with matching ring

1 hour ago, HiveIndustries said:

2 hours ago, DaveS said:

A one-way trip isn't a suicide mission if you're setting up a colony, with people expecting to live out their (Long, hopefully) lives there. I doubt the Pilgrim Fathers (What about the mothers? Much more important)  on the Mayflower were expecting (Or even wanted) to return to England.

Your assumption that billionaires want their employees to commit suicide is dangerously close to political.

Musk talks about it openly man, I don't think it's political. The only thing up for debate is the word "suicide" which I, probably like you, would disagree with but certainly worth debating.

We know enough to know there's going to be damage to humans on the way and when you get there and that they're more than likely to shorten life, at least speculatively, coupled with a "one way" trip, whether or not that qualifies as suicide, isn't that fair game?

Dave, you have a point, to describe billionaires as having wet dre4ams about the deaths of their employees is wrong, a more appropriate word would be indifferent. recent times have given lots of examples of this behaver, amazon, tesla and dyson to name a few, where employee well being has been given  a lower priority to achieving their aims be it business expansion, profitability or anything else they might want.

Personally if amazon's founder were to send people to mars does anyone here think he would have any more concern for their well being than he would for his warehouse and delivery staff? is this political, i guess it is but that's only because the old given of the 'duty of care' we have to each other has become a tribal political issue.

As for suicide mission, I would say that any high risk project where the end of mission crew survival was not the first design and project priority would at best be a sacrificial and at worst suicidal mission. I guess this opinion is guided by seeing being careless with your life and suicide being side of the same coin... though i appreciate that many would disagree.

1 hour ago, SimM said:

Insurance companies have a way of looking at a claim and weaselling out if it, if they can.

You have a point, but i think  it depends upon how important 'weaselling out' is to the company's business model. rather like the difference you see between the full service, low cost airlines and out there in a category of their own Ryan air. Its worth going to which? to get their consumer reviews of insurance companies, as this lets you see who are the full service insurers and who are the Ryan air wantabe's.

I think quite a bit of the weaselling coming from the insurer and the customer not having the same understanding of the risk's being insured, so nothing quite beats being very upfront and descriptive of what you want, as in:

On 04/10/2021 at 20:44, qisback said:

I had the criteria of something like:

1) "I'd like to put all my kit in the garden and run 2 cables to it, leaving it unattended and operate it remotely"

1) "I'd like to go to the middle of no where, setup my kit, run a cable into a caravan, set a session going; get drunk; fall asleep and I want all the kit covering on insurance"

This great description and more or less what ive done when trying to get non standard insurance, it  allows the sales team to find a risk pigeon hole they have already have. Or failing that; help the actuarial identify set of risks in their risk lists  and data, from which they can tell the business what the risk they are agreeing to is. if the business sees  risks that cannot quantified;   you get a refusal to cover or a large premium to offset that unknown risk.

manned missions to mars are going to be fabulously expensive, even if you go for a billionaire's dream of employees on a suicide mission, i don't think the wealth available to even the richest of our current crop of vein billionaires have a fraction of the cash needed. That leaves political projects to mars, I don't think there is a country on the planet that does not have sufficient domestic government funding issues that would not make diverting cash to a manned mission to mars a toxic political project.

I would be shocked if we did a manned mission to mars this century

2 hours ago, Tim said:

Looks like the neighbour I had at a "dark site" recently.....

My neighbour at home is similar, massive floodlights on all night, I spoke to him about it once and he did angle them down a bit, but then upgraded to even brighter, much worse ones.  They drive you mad don't they 😕

I think that there is a strand of the libertarian movement that feel a desperate need to demonstrate their personal freedoms by being as antisocial as they can and demonstrate their concept of personal responsibility, by determining themselves what the consequences their actions should be, i.e. i've been a complete ar*se, ive decided that there should be no consequences... so were all good.

2 hours ago, irtuk said:

I was just sending a pic to my dad, yes, don't be fooled by the beard I'm not Santa's grandad, and I said "this is Hydrogen Alpha data" and I was then going to explain what that was when it occurred to me that I don't know.

I know that its "light" at a particular wavelength of 656 or so nm but is is emitted by hydrogen or filtered through hydrogen?

so in a HA sub, is the recorded signal starlight that has passed through a region dense in hydrogen, or light that has been emitted by hydrogen ...erm ...doing something? I want to say combusting but my knowledge sort of hits a brick wall after the spelling of "Hydrogen" and I am certain combusting is not the right word.

 

Ed.

 

the light that you are recording is emitted by hydrogen atoms in space.

because of the the way the universe works electrons around atoms behave like waves and can exist in specific resonant orbitals, which we label s, p, d and f, these are more clouds than planetary orbitals and levels that we label as 1,2,3....

each of these levels and orbitals is associated with a precise energy, and the electron whilst it is under the influence of the proton in the nucleus must have enough energy to be in one of this orbital levels.

now with hydrogen we are usually thinking of s orbital which is a spherical cloud around the proton, and when the hydrogen atom is at minimum energy its ground state, the electron is in the 1s orbital.

there are numerous ways in which an electron can be knocked into an excited state, which would be any level higher than 1, but once there is will be drop down to the ground state and it does not have to do it in one step.

each time it drops down a level, it must loose the energy difference between the two levels. it does this by radiating an photon whos energy determines its wavelength

so in the case of hydrogen-alpha its a transition from level 3 to level 2, hydrogen-beta is 4 to 2 and blue/green, hydrogen-gama 5-2 and blue, level infinity to 2 is violet

we dont really discuss transitions to level 1 as they are in the ultraviolet and space telescope stuff and transition to level 3 or higher are infarred or lower

you can get a more detailed overview of the subject on wikipedia

Now the question of dense hydrogen clouds is interesting, in these clouds hydrogen atoms can absorb hydrogen alpha photons and then re-emitted as a new photon in any direction. so as hydrogen alpha light travels through a dence hydrogen cloud  towards earth its at risk of being scattered in all directions, thus less photons reach our telescope. so actually dense hydrogen clouds can be opaque to hydrogen alpha and its series siblings whist transparent to other light frequencies

The only way you can do this for $400 is if you are repurposing a DSLR and lenses that you already have, so that the only thing you are buying is the mount and tracker.

as soon as you talk telescopes(to use uk second hand pricing) your looking at a motorised mount which is going to cost between £250-700 and 300+ for the telecope

living London and being able to stalk my local park without a head touch at night  any time of the year, all i can say is

what are you complaining about, you can still see black behind the house 😀

I am just starting to get into astronomy and I am currently at the stage of knowing how little i  know, so take what i am saying with a pinch of salt.

There's a budget issue here. that filter wheel and filter set is going to set back the best part of 700+ GBP, add this to the cost of a mono sensor and its going to come close to taking you into a new class of sensor when your buying osc. I suspect that unless you have a lot of clear nights and an observatory to capture them, that your going to get best value from the osc.

the one thing can say with experience, going from a Pentax DSLR aps-c to a secondhand 183 osc; is that the loss of fov is more than made up for by the huge improvement in sensitivity, noise and general image quality. which ever way you go, the only regret you will have is not doing it sooner.

This is a really nice piece of engineering. I am just starting the 3d printing  and cad journey and to be honest I didn't really think it was capable of stuff like this. something for me to aim towards

I have a Pentax 3ii and i really like it... as a DSLR camera, it is amazing value for money particularly is you value water resistance and being able to take low light indoor photos without flash,  Iit has a sensor sensitivity few canons come near. In principle it is very good for astrophotography, even comes with a built in, but temperamental, star tracker and i got some really nice beginners photos this jan/feb with a sw 80ed using an intervalometer.  And if this is all you want pentax is not  a bad choice.

However the problems start when you want to go beyond using an intervalometer and start to make use of all that software thats out there, EKOS and kstars in my case. the software support for pentax is almost non-existent as pentax seem to want it that way. there are reverse engineered drivers but i have yet to get the to work my k3 and to be honest I am not willing to put the time in as i am going over to dedicated astrocams.

I would personally say if you want to do astrophotography with dslr, go for canon its got the best software and hardware support and at the end of the day that is more important than the quality of the sensor because  if you have to constantly fight it to get it working, you won't use it