Rustang

I would say its the other way round in regards to the 'LX200' I would say that maybe that scope that was put together for someone, its got the same looking focuser as the Schmidt but the rest is the same as mine, Ive not seen that finder scope before either but its bracket is matching the same green paint finish as the rest of trim. Its an interesting one!

5 minutes ago, johninderby said:

ORION OPTICS XSN200 (8") SCHMIDT NEWTONIAN REFLECTOR

Not one of these unfortunately I don't think as its got the same standard secondary mirror that mine has! 

10 minutes ago, johngm said:

Or, it could belong to a boy racer astronomer, you know, the ones that used to stick RS turbo stickers on there 1100 cc escorts 😂😂😂

Difficult because if that is the case they have done it really well!

34 minutes ago, Graham Darke said:

Is it Schmidt Newtonian by any chance? Orion Optics used to sell a 200mm f4 Schmidt Newt in the early 90s. They marketed it as the XSN200 which came on their own German eq Mount. If my memory serves me correctly, they also marketed the same tube on a Vixen GP Mount which they sold under a different model name.  Was there an XLX200? 

I dont think so, the secondary mirror looks exactly the same as mine! I would have thought that would be different if it was a Schmidt Newtonian - looking on google, I have found the Schmidt Newts, doesnt appear to be one of them, its a strange one!

Managed to get a picture! 

10 minutes ago, Peter Drew said:

There is a VX200, perhaps someone spelt it incorrectly.       🙂

Lol 😄 the other thing is that the 'Orion' logo txt is white where as in all other pictures of these scope's, its black! Same font though!

Quick question, has anyone heard of an Orion Optics 'LX200' I've seen an old 8 inch Newtonian pretty much exactly the same as my old Orion Optics Newtonian f6 (white and green) but Ive never seen one from research that was an 'LX200', the sticker lettering looks authentic but the only LX200 I know of is a Meade scope!?

A picture of mine for reference!!

38 minutes ago, Seelive said:

I've never quite understood why guiding accuracy is referenced to arcsec on the guiding log. I would guess that PHD2 can only guide at best to within about +/- 0.1 PIXELS of the guide camera.  What that results in +/- PIXELS on the imaging camera depends upon the focal length of the guide scope, the focal length of the imaging scope, the pixel size of the guide camera and the pixel size of the imaging camera. If you are getting round stars, then I wouldn't worry too much about the guide log, but if you're not and the guide log shows guiding errors of less than 0.2 pixels then I would suggest you need to consider your hardware setup.

Ive never quite understood most of astrophotography let alone all this calculations stuff! 😄

2 minutes ago, wimvb said:

Yes, I couldn’t see that in your screen shot. If you can increase that, the guiding variation may decrease.

Thanks, appreciate the help as always. I will put this together with what Ive been reading and make some small changes and go from there 👍

40 minutes ago, wimvb said:

The guide error, RMS value you are refering to, should be the one in arcseconds, which for you is 1.53” if I read correctly. This value should be at most half your imaging scale, ie less than 1.1”, otherwise tracking errors will affect the stars in your images.

To avoid guiding on seeing flicker, keep your exposure time several seconds. If you go below 1 second, the guide star will move due to seeing.

The guide assistant will give you recommended settings. Use these as a baseline. It will also show your polar alignment error and DEC backlash. If the latter is large, keep a small polar misalignment, and guide in only one DEC direction (opposing the drift).

On the phd website, there is a link to a guiding analysis program. Download and install to analyse your guide logs.

When you say 'read correct;y' you mean from the blurry picture? By imaging scale you mean the imaging camera's Pixel scale which with my canon 600d and 600fl scope is 1.5 so as you says needs to be 1.1 or less, if its 1.53 then that's why I had star issues in my last session. Or do you mean the 3.44 Image scale of the guide scope would then need to be under 1.7 ?

When you say exposure time, you mean the number to the right of the 'stop' symbol on PHD2 which i currently have set to 2s !?

PHD2_GuideLog_2020-09-09_215827.txt Ive found the logs, here are a couple from my last session.

PHD2_DebugLog_2020-10-09_205113.txt

I'm trying to use my down time as productively as possible so I'm now going to try and understand my guiding graph/settings a little better. Up until now all Ive known really is to make sure the TOT reading stays under 1 and your good!, it has been doing that fairly well, keeping between 0.4-0.8 most if the time but really does get upset sometimes and as you can see from the picture, the graph gets pretty crazy.

Ive been doing a lot of reading myself and have read that if its doing this I can lower the 'RA Aggressiveness' setting to 70-80% (currently on default 100%) so I may try that and also tweak the 'Min motion setting' There's a great document called 'Understanding PHD2 and getting it to work properly' that Ive been reading and it helped me set things up at the start. In there it talks about the Calibration step size, the example given for the writers set up with a pixel scale of 2.67 arc-secounds per pixel, he sets the steps to between 2000-2500ms, he states that if your pixel scale is higher then to up that amount, mine is 3.44. In PHD2 I have changed mine to 3000ms to start with but it wont allow me to change this in the advanced section settings and keeps it on the calculated '1950' for the guide scope details I have put in so not sure what to do here?

The guiding can get upset after a dither,  I have read that if the Dec cant recover well after a dither then to dither only in RA, from reading up this doesn't seem to be a good option and produces 'walking noise'

I want to clarify in PHD2, what is the 'Guide speed n.nn x sidereal'? is, is that the Guide rate? Mine is on 0.5, it also states in the document to set that to 1x so should I?

What are the readings to keep an eye on, in real simple terms? My graph can look crazy but what are readings besides the TOT that I need an eye on to help me tell how the guiding is really going? I believe there are some in regards to the image pixel scale?

I'm not sure how to get the logs files from my sessions so currently I only have to below cropped image for you to go by and it would be good to get that settled out. i know there's lots of factors, I have been reading but lets start with the good basics, and as you know I can struggle to understand things so I simple terms please! ☺️

To add, I know about the Guide assistance but a little worried i wont really understand it at the moment.

1 minute ago, Coriorda said:

I think something simple like the Star Adventurer or Skyguider Pro should start me off ok 

Sure, just check the max weight capabilities and you should be fine. 

1 minute ago, HunterHarling said:

Pretty much  To my credit though, I had originally gotten the C8 for observing, but I quickly became interested in imaging.

Same here, didn't take me very long at all before going onto imaging, I now very much enjoy both Imaging and visual. 

I started out with a decent mount which is really one of the most important bits of kit so it can handle the 650fl absolutely fine. 

Hello! I shouldn't think you'll be disappointed with that set up. It will fit in targets such as the Heart Nebula really nicely. Get a Bahtinov Mask to aid focusing and your away 👍 Your right though, I really long focal length will be a bit harder to deal with but your way down at 360, I started at 650 without any trouble!

No problem, it takes a bit of learning to get them done properly 👍

Flats are a thing to master, I thought I had it right until recently. You need to try and avoid any unwanted stray light coming into the light path and i think the way your doing it may not be good for that. The way Ive got my best results recently is by using an LED drawing light pad from Amazon pressed right up against the scope, they are pretty cheap. Place a piece of paper over that and Ive also cut the same aperture of the scope out of foam which then sits around the end to help block any unwanted light. The light needs to dead even for Flats to work and also the correct exposure. There are more knowledgeable people that will come along to help but that's what Ive learnt recently. You can also try the computer screen option with a blank word document on the screen but the best flats Ive achieved to date is with the light pad. I was also told this recently in regards to LED's that they refresh many times per second so any capture shorter than the refresh rate and the light will be uneven so you will need to bring the exposure down to around a second.

You will find a recent good flat of mine to go by below!

14 minutes ago, Aramcheck said:

On @alacant's suggestion of stacking without Darks, you can of course try this & compare the noise levels on a background area. I tried it once & found that with Darks included in the process, my background noise with my astromodified 600d appeared to be about half that compared with the same set of Lights stacked with only Master Bias & Master Flats.

BTW I also have the problem with Dithering timing out on occasions.

Cheers
Ivor

So to clarify on your test, you stacked a dithered set of images with and with out Darks and the noise appeared to be less when you still added Darks? 

12 minutes ago, vlaiv said:

At least there is simple point to all that - do dither it is good for the final image

I've just got to work out if I've got the correct settings in APT and PHD2 now! 😊

25 minutes ago, vlaiv said:

Not true.

Dithering is very beneficial for lowering noise in the image, although most people don't know this. This is especially true when small number of calibration subs is taken.

To best explain this we need to look at what is happening when dithering. Let's observe single pixel and part of target on that pixel. If we have perfect tracing, same piece of target always lands on same pixel - with dithering it is always different pixel.

This means that with perfect tracking stack of pixels for our part of target come from single pixel in each sub and consequently get calibrated always with same bias value - bias is in this case constant and does not average out beyond it already being stacked and averaged.

With dithering - target covers always different pixel and bias sub calibrating always different pixel will have always different value as residual after stacking is random - this makes bias noise that we inject back in the image much smaller than in above example.

I know this is poor explanation, but point is - with perfect tracking, bias that we use to calibrate is always the same with respect to target (not image) and can be mathematically "pulled in front of average" and noise from master bias pollutes final image after stacking. With dithering - it pollutes each sub "differently" (same with respect to image but differently with respect to target) and does so prior to stacking and when stacked - same thing happens as with every other noise source - it gets reduced with respect to signal (stacking improves SNR).

In fact - you can check this yourself - take any set of calibrated and dithered subs and do two stacks:

1. plain average stack after aligning subs

2. plain average stack before aligning subs

Now take empty patch of sky (try to avoid stars) and measure standard deviation. You will find that standard deviation is smaller in first case - noise in background is smaller than in case without alignment.

No alignment would be necessary when one has perfect tracking / guiding.

 

Your a clever man but most of the time your knowledge is wasted on me as it goes right over my head! 😁

44 minutes ago, wimvb said:

Osc of course. 😋

@Rustang, & others:

Regarding dithering. If you plan to dither 15 pixels, and you have a guide rate of 0.5 sidereal, then dithering should take twice your imaging scale ("/pixel) in seconds. Ie, if you image at 1"/p and your guide rate = 0.5, a 2 seconds dither will move your mount 15 pixels. The 12 pixel dither recommendation comes from a talk by Tony Hallas on astrophotography with a dslr.

Dithering will never by itself lower the noise in an image. Only more data will do that. And then only when the exposure time is such that the read noise is burried in light pollution (photon) noise or thermal noise. For a non-cooled dslr at high ISO, you may run into dynamic range problems. Keeping the ISO down can be a good thing. But dithering will spread any fixed pattern noise, and break up so called walking noise.

Cheers, I never fully got my head around the calculations for dithering and with that, the settings needed in APT, I will try and go over it again 👍

49 minutes ago, Budgie1 said:

I've got to get some flying practice in, I've been asked to do a wedding in August next year with my drone. They want aerial shots and footage! 😬

I've worked with a couple of drone companies at weddings, sounded like I had a giant bee over my head alot of the time but they produced some great stuff 😊 

I'm finishing shooting weddings next year which I've been doing part time for a few years, once thats over I'm selling that gear which will then be time for upgrades but must be patient till then! Must be patient, must be patient......

21 minutes ago, ollypenrice said:

Firstly I think that many aspects of the processing are quite simply excellent. The background sky is beautifully flattened both in brightness and consistency of colour (with the colour good) and it is at a respectably light level. So many backgrounds are too dark, too blue, too red, too green etc. Not this one. Its great. Stars are small, tight and round. Not enough blue? Vlaiv, on here, has made the point that amateur imagers push for too much blue in spiral arms and I think he's right. I've certainly changed my own approach in the light of his arguments. Look at the Hubble team's colour: https://www.spacetelescope.org/news/heic1901/

As you've said, where the image starts to fail is in its small scale details. Would more data help? Enormously. Build in a large scale dither of about 12 pixels, take a lot more subs and use a sigma clip routine when stacking. I don't use a DSLR but think Alacant's calibration suggestions will work best. No darks, just bias. (DSLR darks are not adequately temperature matched.)

Olly

That Hubble picture really helps settle the mind a bit ! 👍