Rustang

Very nice, Il give £10 to anyone who can tell me how many stars are there! 😄

2 hours ago, CraigT82 said:

Does the drawtube still rack in and out smoothly?

The alignment of the focuser with the optical axis can be checked with a laser collimator if you have one?  

You can clamp it in the focuser and check the dot exits the front lens bang in the centre (assuming the laser is straight). If not in the centre then the focuser should be adjusted until it does... I'm not sure how it's done with your focuser but I had a TAL100rs which needed adjustment and I did it by loosening focuser mounting screws a tad, moving the whole focuser assembly until it was straight as I could get it (as per the laser dot),  then tightening up the screws again (this was a bit of a faff tbh)

You can also check for decentred front lenses using a cheshire sight tube if you have one. 

Thanks for the tips, sadly my laser is not straight and I currently don't have a sight tube. I'm leaning towards a professional taking a look because I was planning on a possible upgrade later in the year and as it stands I wouldn't won't to sell this scope on unless the it's fully functional, cosmetically it's fine. I'm not 100 % sure the focuser on these scopes is adjustable because I remember looking to see if there was a way to when I had my 72mm ED DS PRO so if I keep this scope maybe it's time to  upgrade the focuser. It does still  run smoothly also. 

Images of the gaps/mis alignment mentioned above. Now I know they are minimal but I'm pretty sure they weren't like that before the fall. The tube now sits closer to the housing on the right and the unit doesn't sit tight to the main telescope tube on the right. 

10 minutes ago, CraigT82 said:

Sorry to hear about this Rustang, I'm sure it is fixable, if there's no broken glass then there's not much else that can go wrong with a scope that can't be fixed.  Poor cat must have been manic. 

You could also try Steve Collingwood over in Tonbridge. Very nice chap. 

http://sctelescopes.com/contact/

Thanks, il give that look, fingers crossed it can be sorted and yes it definitely could have been worse👍

5 minutes ago, JeremyS said:

Very sorry to hear this. Coincidentally this is the second post I’ve seen this week about a cat knocking a scope off a surface where it had been left onto the floor (on another forum, it was a Takahashi)

Thanks, these things happen and in the grand scheme of things in life its really not the end of the world but I'm still gutted. That was a much more expensive accident for that person then, and to think I was going to upgrade later in the year, very nervous about that now but life must still be lived 

18 minutes ago, Peter Drew said:

Last question, was the reducer fitted during the accident ?         🙂

No, thankfully because I have to, I always remove the camera so it was safe in its protective box. The scope should have also been in its flight case safe and sound but due to the run of clear nights Ive been leaving it out ready to go. 

24 minutes ago, Peter Drew said:

 

29 minutes ago, david_taurus83 said:

Do a star test on a bright star. What scope is it by the way? You got any pics of what you think doesn't look straight? Could be that the optics are still OK but the drawtube is slightly off centre with the optics.

SW 80 ED DS Pro. The draw tube doesn't now look 100 % straight in the unit as in the gap all around isant the same, it's slightly over to one side, there also seems to be a small gap one side of the focus unit against the main telescope body. I don't have a diagonal to to achieve focus with an eye piece plus very limited knowledge on star tests. Would a miss alignment in the focus tube cause the same stars and from my knowledge that's part of the collimation to make the focus unit parallel with the lens cell!? 

Il try and get some pics up tomorrow 

4 minutes ago, Peter Drew said:

I agree.  I'm visual only but I have considerable optical experience.  The only time I've been unable to focus a star with an otherwise ok telescope is when the spacing of a focal reducer is incorrect, hence my comment.  Does your telescope have a built in reducer?     🙂

Not built in but I've always been using the same reducer. 

4 minutes ago, tomato said:

Sorry to hear about this unfortunate event, I have come across a few mishaps related here on SGL, but not this combination.

+1 for trying Es Reid to see if a bench test is possible. From memory FLO charge £75 for one on a new Esprit purchased from them, so I presume a test service is available. I think adjustment  of the collimation is possible, but I’m not sure what could be done if there is more damage done than that.😕

Thanks, I will contact FLO. It's probably best after a fall like it had to get a full test and go over. 

2 minutes ago, Peter Drew said:

I would expect a collimation issue due to such an accident to show distorted star shapes or comet like rays all pointing in the same orientation.  I'm not an AP specialist but to me the stars look reasonably symmetrical ?      🙂

It would be pretty strange to all of a sudden get out of focused stars like above when I've never had them before like that only since the fall they appear not so good. I'm not saying my focus has been perfect but I've always produced the crisper looking stars above until now! 

1 minute ago, tooth_dr said:

Going by your present yield of images I'd say you are fairly well versed in AP, and would be unlikely that it's not focused.  Somethings knocked out of place.

I'm certainly leaning that way, it's been such a great scope 😔

7 minutes ago, Peter Drew said:

Looks more like a focus issue rather than a collimation problem.       🤔

I would hope so but I focused in the exact Same way as I always do with a mask and even checked it thoroughly before the last two sessions after the fall so I can't see why it would be that out, to be honest the target looks ok focus wise but not the stars!. In all of sessions using that scope and focusing in the same way I've never had stars like I do now. To take a fall from 4ft onto a wooden floor would it not be expected to be knocked out of collimation? I would need to buy a diagonal to do a star test but even then I'm not experienced enough to 100% tell if everythings ok. For learning purposes, if you think it's a focus issue, what would the stars look like then if I was a collimation issue!? 

So I had an infuriating and upsetting incident last Saturday, I had been out imaging Friday night and packed up about 3am and went to bed. The next morning it was really hot so I always open the shed where my gear is stored to let the air flow through, as i opened the door our cat ran out, oh so I locked you in by mistake, i didnt even know he was in there! Then I stepped into the shed and my heart sank, my scope with guide scope with guide camera attached was on the floor! it was 4ft above the floor position at a 45 degree angle away from the edge of the work top where i always leave it. I went numb and just stood there waiting to be pinched and woken up from this nightmare. How it happened i dont know, it was obviously the cat but considering it all weighs nearly 5 kg and the cat weighs nothing he must have gone mental trying to get out!!!

I didnt have the heart to pick it up for a while not wanting to accept any damage. I eventually did and started stripping it all down checking for damage. The bracket holding the guide scope on was pretty bent up including a screw on the back that holds the focueser to the scope body. The main scope sort of appeared unscathed but on closer inspection the focus unit appeared not 100% aligned with the body and the tube the same with the unit, it had taken a knock because it was locked but pushed in! apart from that it seemed ok. After sorting everything the best I could i decided to try imaging the next couple of nights. The guide camera still works, and all appeared ok with the images so I was relived but also not convinced i had gotten way with any issues just yet.

Sadly after looking at my data tonight I can see the stars are not great at the same focus, see images below. The crisper stars from before the fall, the crap stars after! So i would say its now out of colimation which I'm not surprised about! I'm gutted, my gear is my pride and joy. and there was me worrying about the stars in the corners in my earlier thread!

Does anyone know if i could be sent away and where to be sorted!?

2 minutes ago, symmetal said:

If you have a field flattener in the image train you can get this effect with incorrect flattener sensor spacing distance, generally this effect is with the distance too great.

Yes if the polar alignment is significantly out, you will get visible field rotation in the image and it will rotate around the guiding star.

Alan

I'm using a reducer so as said above, it could be that not correctly spaced, I will have to have a look at that when I get a chance.

6 minutes ago, Astro Noodles said:

It's not PA. If it was, the streaking would all be in the same direction, and it would be across the frame. What sort of scope are you using? are you using a field rotator?

Yeah I'm using a reducer so it could well be that, that's not correctly spaced!

10 minutes ago, Astro Noodles said:

I can't think what else could be causing it, What about the camera, is that secure?

Camera is definitely secure. If it happens to be the pola aligment thats out (i cant see how though) could that cause it even with guiding?

4 minutes ago, NorthernAstro said:

What type of mount is it? If it is an alt az mount, the field will rotate over time, if it is an equatorial mount I am sorry and I can not help you.

HEQ5 Pro

10 minutes ago, Astro Noodles said:

Is the scope slipping in its rings, or the camera slipping?

Could be but its pretty hand tight in its rings, i never know how tight to go though!

Ive known my stars in the corners of my images have always been pants so i felt its time to see how to improve this. The strange thing is, if you look at my image it looks like field rotation if you notice the direction of travel of the stars in the corners!? I use an app to see where to put Polaris for Pola alignment so I cant see how that could be so far out and I'm guiding also so any advice would be greatly received as always.

what else can I add so what they all said! 😊

I nearly brought one of these second hand which I would still consider to upgrade from my SW 80 ED DS Pro. How much better it would be though... 

https://www.teleskop-spezialisten.de/shop/Telescope/ED-APO/80-90mm/TSAPO906-TS-Photoline-90mm-f6-6-triplet-FPL-53-SuperApo-2-5-CNC-OAZ-tube-length-adjustable::1055.html?language=en

35 minutes ago, vlaiv said:

See if you can get longer exposures as well. That camera has ~8e of read noise. Ideally for NB you want something like 20-30 minutes of exposure if your gear is up for it.

Blimmey! what about light pollution, I'm in bortle 6!? would that limit my exposure time? obviously I can just try and see what happens. That will be a long process to get set of darks completed though! 😩

1 hour ago, vlaiv said:

This was with taken with narrowband filters and QHY 9 camera?

What sort of exposure length did you use?

Yeah that's right, it's Adams old QHY 9 mono CCD with Baader NB filters. I've been doing 10min exposures for all of my projects. 

This short intergration time was only just to see what the data was like to start with, I do this with all of my images, stack the first couple of hours or so just to see before then gaining some more data. It was because I've never had it turn out like the above before which is what lead me to ask for help, my first initial test stack is normally noisy but never what was happening above!. I do normally try and get around 4-5hrs on each wavelength and know I should still be going for more. 

I will hold my hands up and say I've been lazy with my integration time, I'm still fairly new to Narrow band imaging and probably will in time settle to longer projects, i.e longer integration time but for now its been fun trying lots of targets!  

3 minutes ago, vlaiv said:

Sigma reject is good algorithm that for most part should behave like average.

There are two important things to understand with sigma reject:

1. Meaning of sigma

If we have normal distribution of data, then 68.27% of all data samples falls in one sigma interval around mean value. 95.45% falls into 2s interval and 99.73% falls into 3s interval.

If you for example put 1 sigma as your parameter and have perfect data without any satellite trails or whatever - it will only stack about 70% of your subs. For regular data you want to have sigma between 2 and 3 because you want to stack between 95% and 99% of your subs.

2. For above to work properly - you need to have normalized data. Way you normalize your subs is very important

As target moves across the sky - it changes amount of atmosphere lights get thru and hence brightness of the target. If one frame is taken in zenith and another frame is taken when target is at 45° altitude, then second one will be just 70% signal strength compared to first one

Transparency changes during the night and so does light pollution (target moves and people turn lights on/off). This thing with light pollution changes background value.

This makes data incompatible for sigma reject, and in order to make it compatible - well you need to normalize it.

I'm afraid that I never had much faith in DSS frame normalization process - primarily because I don't understand how DSS does it. I know how it should be done - and options present in DSS don't really fit into my understanding of it:

In any case - you should fiddle with these settings - probably use Rational instead of linear and use middle for calibration method or something like that.

Don't use median methods (like in image above) - use regular average methods (simple Kappa Sigma, and keep number of iterations to say 3, so 3 and 3 is good value for Kappa-Sigma clipping).

Ok, il try and get my head around all of that, it all makes some sense etc but I never realised that DSS could throw out some subs by itself! Thanks again for all your help, I owe you yet another beer! 👍