scotty38

1 hour ago, AstroMuni said:

You could use Cartes du Ciel instead. Thats less processor intensive.

This is true and I have done this too. As I mentioned I just use NINA 99% of the time and if it cannot find a target I fire up Stellarium pass the coordinates to NINA and then shut it down, sorted.

Thanks @vlaiv yes that helps it really does and just what I was looking for, much appreciated!

I can accept that the cem70 is "better" than an eq6 but when all is said and done it's still in the same league, the eq8 is a definite step up if you want heavier.

1 hour ago, vlaiv said:

I'm not sure that I understand what you are asking?

Guiding is independent of resolution at which you are imaging. You can guide the mount and not have scope and camera on it at all.

What you want to do is get your guiding and mount performance in general to the best level you can comfortably achieve.

Guide RMS is contributing factor in overall FWHM that you'll be able to achieve. Other two being seeing and aperture size (for diffraction limited scope or spot RMS in general).

Those things combined will determine how sharp your image is and whether you are over sampling or not given your target sampling rate. It is the only factor that you have some influence over after you've chosen our scope.

You can't influence seeing. Once you have decided on your scope, only way to change its aperture size is to replace it (same thing goes for mount of course). Only thing that you can somewhat tweak is guiding parameters and mount in general (like some mods to make it more stable, more precise).

We often say things like "You need to guide at half of our sampling rate", but these are very rough guidelines. What we should really be saying - make your mount performance the best you can (and that is really inline with other recommendation - and that is that mount is the most important part of imaging kit) as it will in part be determining factor whether you should bin x3 or x4 later (if your primary goal is high resolution).

Thanks and yes maybe not the best question but you did sum it up with "We often say things like "You need to guide at half of our sampling rate"" as I think that's the basis of what I was asking.

Given you essentially said guide as best as you can are you saying that due to seeing etc etc that even with a setup that "could" deliver 0.48" even if I can still only guide at 0.8" with binning in software later I could still make good use of the kit? Maybe not as good as it could be but not a complete and utter waste of time?????

I'm purposely trying to give a bad example to try and make my point by the way 🙂

@vlaiv Let's say I did buy a Stellalyra 10" RC and used it with my QHY 294m, that would give me a resolution of 0.48"/pixel.

If I intended binning later x3 or even x4 to give me either 1.43" or 1.91" do I still need to guide at 0.48" in the first instance?

Apologies if this is a dim question but in my head I think I can make arguments both ways......

Dr Magnus Pyke, one for the oldies 🙂

It looks like it could be dust and would be dealt with by flat frames in a typical deep sky process but never having done planetary I'm not sure if the same is true, process wise anyway.

13 minutes ago, wuthton said:

Focal length has the big effect on field of view, more aperture (at the same focal length) gives you more speed. Larger pixels on your camera also give you more speed. 

 

I did add "all things being equal" as you mentioned 130mm f6 versus 254mm f8. If we take 130mm as being fixed then f6, f8 etc etc won't make it faster, it'll only change the fov because the focal length has changed of course. That's what I was trying to say, maybe not very well I accept.

2 minutes ago, AstroMuni said:

The way I see it is - for a given FOV the best bang for buck is a Newt with the largest aperture that your mount can handle AND if you can get a faster F-ratio then you will need to spend less time imaging! As an example for my HEQ5 Pro you can get a SW Quattro 150 f/4 with a coma corrector that makes it even faster at f2.5 for around £499. If I wanted to get something like this in a refractor with a 150mm aperture, I would need to spend a lot-lot more and the HEQ5 would probably not be capable of taking its weight 🙂

Agreed it's much more cost effective than a refractor no doubt but it's not a galaxy scope unlike the 10" RC at 2000mm, yes it's f8 but it's still 254mm so still plenty of aperture so it's not "fast" in those f ratio terms. This takes us back to my original question (I think) though actually as I got sidetracked with the speed question 🙂 🙂

3 minutes ago, AstroMuni said:

+1 .... for folk like me who can only image during weekends and NOT having an obsy and dont wish to break the bank, thats an important consideration (esp when you live in UK and are at the mercy of the clouds). So the choices for me are large aperture, fast Newts. 🙂

Yes, if you're saying what I think you're saying then there are cheaper ways to achieve speed........ Let's park ultimate quality as my example probably wasn't at that point anyway.....

24 minutes ago, wuthton said:

Colour me confused, my apologies if I've misread your post but isn't the LZOS 130/ASI183 (F6, 0.63"/px) significantly faster than the 10" RC/ASI16200 (F8, 0.38"/px), regardless of the aperture?

Hope I get this bit right at least but in telescopes focal ratio, f8, f6 etc only really impacts the field of view all other things being equal, it's the aperture that has the big impact on speed. I'm sure someone else will give you the warts and all but I think that's the gist of it.

Ok thanks so cost aside if I can operate it correctly if nothing else I have the speed to take advantage of. Has to be said that’s a high price to pay though as I’m not picking up on much else really yet plenty of folk have them and surely I can’t be the only one not on the top of a mountain 😀

thanks for the feedback Vlaiv, much appreciated!

What a setup! Reminds me of the dashboard of an Escort Rally car 🙂 🙂

Hi all I created this post as I don't mind admitting it still confuses me despite the best attempts of @vlaiv to educate me otherwise. I hope he doesn't mind but I stole part of one of his posts from another thread as this is what I want to speak about.

You can all read what he has written below but here is my scenario. Let's say I wanted to buy a longer scope for imaging galaxies and let's say I decided upon a 10" RC, the carbon fibre truss version that FLO sells for roughly £3k. Let's also say that I recognise I need some serious mount/guiding to be in place so I also buy a 10 Micron GM2000. In actual fact the specific scope/mount don't matter you get the point because my question is that given I'm in the UK and at 10m above sea level, looking at Vlaiv's words is there really any point in me having a setup that will image at this level?

On 09/11/2022 at 09:54, vlaiv said:

Resolving power of the telescope grows with aperture size. Large aperture resolves more than small

For given pixel size longer focal length will give higher sampling than shorter focal length (more pixels per arc second).

It turns out that these two grow the same for fixed F/ratio - thus if 6" scope has optimum sampling rate with F/15 for given pixel size - so with 8" scope as difference in resolving capability between 6" and 8" is the same as difference in sampling rate between 2250mm of FL and 3000mm of FL

Sampling is being measured in arc seconds - but there is simple relationship between pixel size in microns and arc seconds for given focal length (this shows that sampling rate in arc seconds is not fixed and grows with aperture since F/ratio is fixed - larger scopes resolve more in terms of arc seconds or have higher angular resolution).

There is relationship between mount RMS and FWHM that is given by FWHM = 2.355 * RMS

Stock Heq5 has guide RMS of around 1"

Modded/tuned Heq5 has guide RMS 0.7-0.8 and even down to 0.5" depending on all the mods applied (same is for EQ6 really).

Higher tier mounts can go as low as RMS 0.2"-0.3" (Mesu200 for example).

Average seeing is 2" FWHM. Good seeing is 1.5" FWHM. Excellent seeing is 1" FWHM and below (below 1" happens only on mountain tops / deserts - special sites).

You will often find that seeing is below 2" - on a cloudy day / night - but when it is night time and clear - it is going to be around 2" (stable atmosphere helps with cloud formation).

In the end - here is sort of rule of the thumb related to aperture size:

with <100mm scopes - limit yourself to widefield imaging as you'll be limited to say about 2"/px

100mm - 150mm - upper sampling limit would be 1.8"/px

150mm - 200mm - 1.5"/px

above 200mm - 1.3-1.4"/px

One can attempt 1"/px - only on the best of nights using very good mount (RMS 0.5 or less).

In all reality - odds are - you won't get image that has detail below 1"/px in 99.99% conditions / equipment.

 

 

2 hours ago, Ouroboros said:

It should be fine as long as there are no polarising components in the optical train.  People use tablets as light screens and the light from these is polarised. 

Ok fair enough, I imagined it doing funky stuff that could not be replicated from one session to the next but if that's not the case then great.....

3 hours ago, Ouroboros said:

I have wondered whether crossed polarisers might be a way to adjust down the light level of led panels. 

Putting a polarising filter into the optical path you mean? Not a chance that's a good idea I'd say 🙂

On 09/11/2022 at 18:28, MG01 said:

I feel like I'm hopscotching all over the place at the moment...but back to PSUs for now!  @Tomatobro I've found one like yours here which seems reasonable: https://www.hamradiostore.co.uk/product/power-supply-30-amps-variable-voltage-analogue-design/

One question I did have was if a load like the mount which has motors would impart additional noise in the form of voltage ripple that could impact on the CCDs?  Would making two separate cable runs make any difference?  I'm probably doing some overthinking here and if i just run this to a power hub and distribute from there it would be fine.

I still think you should have a look at the Nevada on FLO's site. It seems to do all that this one does and is cheaper. In fact there is an Alinco on the site you link to that looks pretty much identical that is up for nearly £170

@MG01 I have NINA setup to use Stellarium and it works fine, as you say Stellarium is a bit heavy but I only use it for any object I can't find in NINA itself. I also use ASTAP for platesolving as it seems to generally be regarded as the best and fastest but you do need to download the databases but other than that it works just fine.

Run NINA etc on the scope PC (the Mele). I have one too and I save the images to the mele but I run the robocopy plugin in NINA and copy the images off to my NAS as they come in. Of course you could have them go to your observatory PC instead and do the live stacking there.

EZDenoise here too although on my aging machine it does take a while....

I "think" it's to do with how STF computes the stretch after the background removal so the image isn't actually noisier.

I don't mind admitting I am massively biased but give NINA a go, if you've not tried it you may well be surprised. It's very accomplished and any help you need, if you do try it, shout up 🙂

6 minutes ago, malc-c said:

Can we get this thread back on track.  The OP asked for opinions on two scopes which they wanted to use for  viewing both planetary and deep sky objects.  They have since opted for the SW Explorer 150P, which I'm sure will suit their needs until such a time where they may want to invest more time, energy or money and upgrade to something else.  At that time they may have the inclination to try the DIY route and build their own scope (bearing in mind that DIY is not just about grinding a mirror).

We are spoilt for choice these days, with several manufactures offering a multitude of telescopes at various price points to cater for both the casual beginner, through to serious amateur.  Often this can make choosing a suitable model difficult as there is so much to choose from.  Regardless of the model chosen, modern manufacturing techniques mean that the optics are finished to a degree that enables the scope to perform within its expectations.   I think that most of us lack the ability to visually detect if a mirror is finished to 1/10th wave or 1/4th wave, and will be happy with a commercial scope so long as the scope produces a decent crisp image. 

Thanks Malc, but no time to read it, just found a bucket of sand so off to melt it down into glass. Now if only I could remember where I left my notes on how to make Aluminium...... 🤣

I created a weather underground account and from there generated an API key but I don't recall if it ever really worked properly to be fair. Now I just use a powerbox or my cloudwatcher.

I'm at 53 degrees and my guiding was garbage so maybe this saves me looking for other reasons 🙂