Pompey Monkey

OK. From a few years back, the Rosette in HaLRGB with a 150PDS, STF8300M and Baader filters. All on a AZEQ6 from a fairly (Bortle 5/6)* light polluted site:

Edit: Not "(Bortle 3/4/5)" as I originally wrote.

3 hours ago, Anthonyexmouth said:

Don't cheap out on the cable. 

https://www.firstlightoptics.com/sky-watcher-mount-accessories/lynx-astro-ftdi-eqdir-usb-adapter-for-sky-watcher-eq6-or-neq6-syntrek-pro-mounts.html

You can make one for a third of the cost of a pre-made cable (sorry FLO!). The most important thing is to get a genuine FTDI USB to RS232 serial adapter. Also, as said above by @dunc check the TTL voltage against the mount specs. 

BTW, APT is a very good piece of software. @Yoddha puts a lot of work into it and listens to all the user feedback!  

47 minutes ago, John said:

Thanks for your hard work Grant. Very much appreciated

 

Seconded!

15 hours ago, mikeonnet said:

Hi all,

I'm looking for some advice on the 'curved banana' shaped spikes I have. Having used a DSLR connected to a 0.85 focal reducer & Skywatcher 80 refractor, the bahtinov diffraction spikes were perfecly straight including the diaganal lines. However, I am now using a ZWO mono 290 and a filter wheel with the adapters (55mm from the sensor to reducer) but now the lines are curved - see image. I know it's a noisy image but this was just a quick snapshot but my main concern is what is causing the curvature of the spikes.

Is this an issue of the camera not being the correct distance to the reducer? I have only had a quick imaging session of M27 the other day and too be honest, it seemed OK but I just wonder if this 'wobble' will be impacted on all the light frames I will be taking. Any advice please...

I

I've seen this before and I think that it was a around the time that I was fiddling with back focus distance on my Esprit 880ED.

Have you allowed for the increased optical path length due to the filters? This is usually approximately 1/3 of the thickness of the filters. See here http://www.qsimaging.com/downloads/QSI-500-600-Series-Back-Focus.pdf

Also, are the bananas oriented the same all over the FOV, or do they gradually change curvature over the image? If they change, it might be another indication of incorrect spacing between the comma corrector and the imaging plane.

Can you post the whole image?

On 11/8/2016 at 23:03, Uranium235 said:

and the camera was quite close to colliding with the mount

Are you sure it did not actually brush against the mount at some point?

The other thing that comes to mind is a less than perfect PA - this is another source of cone error. However, given the quality of your images, I suspect that your alignment is rather better than +- 3/4 of a degree!

3 minutes ago, Gina said:

This is looking better and better   Thank you everyone   I have Linux Mint on one of my laptops.  Also on my no.2 desktop (home built).  I really need to look into image processing software for Linux so that I can avoid using Photoshop.  I've used the GIMP in the past - must check up on latest version - have they upgraded to 64bit yet, for instance? 

PI works on Linux 

5 minutes ago, Mak the Night said:

I've spoken to a few people on the Ubuntu forums who had problems with it. Trusty Tahr is more stable than 16.0.4 LTS at the moment and it will be supported for a few more years yet, so I don't believe that being that up to date with Ubuntu releases is necessarily true. In fact, non-LTS Canonical releases are far less stable than the long term ISO's and less compatible usually. Ubuntu isn't Microsoft and there is no compulsion to purchase every new OS version released.

I gave this post a "like" because it's obviously well informed.

However, everything I've highlighted in red illustrates why the mainstream user does not understand and does not adopt Linux: I know what an "ISO" is, but many wouldn't and I have no idea what the other highlighted terms mean, and I'm an engineer who's been on a Unix administration course! I know that GIYF, but it takes time

I want to adopt Linux, but the learning curve is steep and, to be honest, puts me off somwhat.

I will, however, persevere. One thing that came to mind to me is to get a secondary system running with mount/camera/obsy simulators until I'm confident that I can diagnose problems and find solutions without wasting night upon night of clear skies before going "live"....

This is a good idea - adding the missing, but necessary, quality assurance. I hope that everyone buying one of these "budget" 'scopes will seriously consider the small extra cost to be a good investment.

53 minutes ago, ollypenrice said:

I think I'll try a refinement of the trainer soles technique which has the virtue of not distorting the rings at all. I'll try to find some kind of strong rubber mat and cut out two squares which I'll bond onto plywood sheets. These will replace the trainers. The stuck adapter menace strikes visiting astronomers very regularly and the resident one from time to time as well! A definitive solution would be nice to find.

Olly

Patent pending? ;)

7 hours ago, FLO said:

Gina had one of the first Esprit-80 scopes to arrive in the UK, it might actually have been the first. At that time there was confusion around the correct spacing requirements (at least one store in the US was quoting the wrong distance and Sky-Watcher's importers were also confused). This thread should be read with that in mind, it is a blow-by-blow account of someone finding the correct spacing. 

We calculated the required spacing, for use with Gina's camera, then asked John (the engineer who makes our adapters) to machine a spacer/adapter. I then drove to Gina's house (wonderful dark sky!) with another Esprit-80 and the spacer/adapter. That was it. Problem solved, happy ending  

In hindsight it would have been more conclusive if we had not replaced the scope but simply left the spacer/adapter because the scope was later tested and found to be AOK. It wasn't the replacement telescope that solved the problem, it was the spacer/adapter. 

Regarding Sky-Watcher's quality control. Optically the Esprit scopes are very good indeed. Have you noticed how few issues have been reported since this thread? But we still occasionally experience minor niggling things like cosmetic blemishes in the cream powder-coating or the focuser's black anodising. And the case material is prone to shedding black fibres which can fall on the inside surface of the objective. For this reason we still check every Esprit prior to dispatch. 

HTH, 

Steve

Yes!  Even more remarkably, I already have the correct spacers for my SBIG CCD/ SX FW combo!

6 hours ago, Sp@ce_d said:

Go for it.. I have two of them. Both from FLO because... well.. they look after you don't they. Any issues I've ever had with anything from them over the years have been dealt with promptly or I've been refunded.. my choice & simples. I've been very happy with the Esprits performance and I've tried a few scopes & never found one around it's price bracket to beat it really. You'll probably find a few of my threads on here comparing scopes when I was trying to run a triple shooter. My first one has been permanently in the obsy now since I got it a very short time after Ginas. The only issue I've noticed is the rubber on the focuser knobs has perished & disintegrated into tiny bits. I found a pile of little bits on the obsy floor during one visit. Took me a while to work out what they were from! I operate it remotely so they are never touched as its motorised. My other ones been fine so far. The only scope I'd think of replacing them with would probably be a Tak now.

That's why I'm buying new: peace of mind. You may, or may not, have seen my thread in "whole scopes" about the second hand Star 71 that I bought a couple of months ago. To my mind it's a write off. Actually, it's worse than that as I've wasted every clear night since the middle of February faffing about with it. Particularly galling as the weather was soooo bad through out autumn...

One more question: Do I need a metric or imperial ADM dovetail kit? I'm specifically thinking of the threads on the scope bracket for the low-profile screws.

Cheers!

Well that was fourteen long pages....

....with no conclusion!

I have a SW Esprit 80 ED, flattener and extra dovetail (for balancing my filter wheel and CCD) in the basket at FLO. I'm just itching to pull the trigger but have yet, despite numerous excellent astrobin images, to be convinced of Skywatcher's QC... 

Anyone? FLO?

On 3/29/2016 at 09:02, ollypenrice said:

I've just this minute ordered some mini 2 way self adhesive bubble levels intended for caravans and camping cars. I'm going to get my cameras perfectly orientated either in landscape or portrait using the star trail method, then set the counterweight arm and OTAs to horizontal and stick them on the backs of the CCDs. I use a dual scope fast imaging rig and this should allow me to switch between landscape and portrait on both very quickly and fairly accurately.

I'll report back on how well this works.

Olly

Or you could draw some fine lines on white tape  

On 03/10/2013 at 21:29, ant said:

I had a very similar issue, absolutely did my head I.

I tried light heating, cooling in a freezer, rubber gloves, rubber grippy tin / jar openers. Everything I could think off.

The someone on here, Peter, I believe suggested the soles of trainers...

Get one shoe turn it upside down, place the adapter on the sole, then get the other one and put sole down on top. Then apply pressure to the face of the adapter and turn.

Took a few attempts but worked a treat.

Hope that helps.

Ant

I know this post is straight out of the morgue, but it just saved my afternoon!

Lovely - understanding what you are taking pictures of is sadly missing in too many examples nowadays - you have an excellent appreciation of the "bigger picture" as they say.

3 minutes ago, sagramore said:

Hello everybody. I hope this is the right place to post because this is my first post on this forum and I absolutely love this thread in particular for reasons that should become apparent....

I just received my 130-PDS and I cannot wait to get out there with it. I recently treated myself to a NEQ6 (I figured better safe than sorry when it comes to the mount!) and have just finished acquiring all the bits and pieces to get it working in the field. I am pretty new and you'd probably describe me as "all the gear but no idea" at the moment! I've upgraded to this kit from a 200P 8" dobsonian so it's a bit of a step up in complexity to say the least.

What I have managed to do so far is get the mount fully controlled by my laptop with EQMOD and Stellarium/StellariumScope and I was able to take some photos using APT and my (unmodified) EOS 550D on it via my ST80. I think my polar alignment isn't too shoddy as I have managed up to 90 second exposures without guiding on the ST80. I was originally trying to mount the 8" dob OTA on the NEQ6, which I think can handle the weight, but the 1200mm reflector is just not built for it and I was getting some mirror slop & tube flexure so I gave up and decided the 130-PDS was the way forwards.

Anyway, my real reason for posting is to show these three photos of my setup (which I have not yet used!) to ask if anybody can see I am doing something very obviously wrong or not? I plan to try and use the ST80 as a guide scope with an old webcam I have modified to fit into the 1.25" connection on the ST80 but as yet I'm not actually sure if it's a good enough camera. I'd like to avoid another £200-£300 on a guide cam for now if I can, especially seeing as my local light pollution is pretty high and I might well be limited with my exposure times anyway.

There is a skywatcher coma corrector between the DSLR and the focuser and I know it's unconventional to angle the camera down like that but it was the only way I could get it to all balance! So - criticisms and advice gratefully accepted for this very new hobbyist! The forecast says I might get some clear skies on Tuesday so I'm hoping to give it all a try then.

Thanks for looking! 

 

Hamish / sagramore

Hi, and welcome to SGL!

Your set-up looks fine. The position that your DSLR finished in is actually a very logical one for balancing and works very well, even if it looks counter-intuitive to the inexperienced. 

Also, APT is my capturing software of choice and will see you a long way into your imaging career. As you are using a DSLR, I'll add one more thing: dither, dither, dither. Dithering is the best DSLR noise reduction strategy (in conjunction with taking more subs) there is.  Dithering works great with APT and PHD

On 15/02/2016 at 21:24, jnb said:

Besides being a very nice image and well documented for exposure times, focal rations and camera speeds (I'm amazed how many people don't mention those when they post images) it's a nice example of coma. I'd be interested to see the same image done with a skywatcher and baader coma corrector. I have a 150p-ds on order and was wondering how much I need a CC and whether the baader is worth the premium (or a revelation worth the discount)

 

You'll end up either needing or wanting a coma corrector for sure

A lot of posters don't mention camera speeds because they use CCDs...

Awww - what the heck - it's only 20 mm more - here's my Rosette with the 150 PDS and Skywatcher CC

37 minutes ago, richyrich_one said:

Are you referring to the uneven halo (only way I can describe it) around Archturus itself?

I was. But now I had a chance to look at the full size image, I agree with you that it looks like a touch of coma. Sorry about that.

Have you got the spacing between the CC and the sensor correct?

5 hours ago, richyrich_one said:

Thanks Rob. That was my inspiration although the PDS cell is a better design which made it a lot simpler.

I can get focus and the draw tube isn't intruding at all. I probably have 5mm out focus left at most. Cover is my next job along with a third locking screw in the focuser collar.

Noticed some coma in this 30s of Archturus. What are your thoughts on it?

Disappointing. I shouldn't need to play around with spacing surely?

That looks more like internal reflections than coma to me.

Welcome to the world of worrying about second-order effects

7 minutes ago, richyrich_one said:

By moving the mirror, by which ever means, could there be a problem with illumination of the secondary?

It's just come to me...would it be plausible to create a cutout in the focuser of say 10mm deep but fading to the edges so as to maintain the usability of the focuser and also keep the intrusion to a minimum? Oh what to do...!

Something like this...

Looking for the perfect solution when one probably doesn't exist...Whatever I do it's looks like I'm dusting off the hacksaw.

 

Morning Richie,

Funnily enough, I only posted about this in another thread just last night:

"15 mm movement on a 750 mm focal length telescope is a 2% radius = 4% loss of light due to spillage past the secondary, assuming it was fully illuminated in the first place. I can live with that 

As for vignetting, I would hope the telescope manufacturers would design for none with the focuser fully extended. I certainly don't see evidence for extra vignetting on my flats.

In summary, a small longitudinal movement of the primary is unlikely to have a critical effect on the optical path."

I do have the 150 PDS, but the principle is be the same. It's all just triangles.

As for the scooping out of the focuser tube.. Well you could always try it and report back your results...

9 hours ago, richyrich_one said:

Hmm...Thanks Paul.

I was hoping for a non-destructive option. I like to be able to "undo" if at all possible.

If we are only talking 15mm, is moving the primary with longer screws a neater way? I'm not that familiar with the cell construction so will have to investigate.

Curious, where did you get the 15mm calculation from?

Good old engineering judgement:

I'd read that 10 mm off the focuser would fix the "bitten" star feature. Another 5 mm made sure*

I'd also picked up my 150 PDS OTA from Astroboot for £113.50, including postage (Brand new, with just a tiny scratch on the tube). So it would only be a little bit painful if it all went wrong. But how could it go wrong? It's just metal tube and some mirrors!

*Of course I checked that I would still be able to reach focus first!

58 minutes ago, richyrich_one said:

Well FLO delivered...Literally

First light has been a while, what with my EQ direct cable DOA.  No problems balancing with the DSLR.

Had a quick go this morning using the synscan handset...Archturus. First thing is the focuser intrusion, much more noticable on the TIF version for some reason.

What are my options to eliminate this? From what I've gathered from this thread...

1. Mount the MPCC into the draw tube some how to facilitate getting the camera further in and so having to rack out more to get focus. Sounds complex trying to get the spacing correct.

2. Chop down the inner end of the draw tube. Could you then potentially rack the draw tube out too far past the rollers at the inner end of the focusser mechinism?

Is there a cheap non-hacksawing option I've missed?

 

You missed one, but it still involves the hack-saw: I chopped 15 mm off of my OTA at the primary end and re-drilled the four cell mounting holes in my 150 PDS for the same reason.

The advantage of this over the focuser hack is that I could use the tripod to hold the tube while I did the dirty deed.  The whole job took less than two hours.

Reason is becuase I was having an awful time trying to get my 383 to calibrate properly a few months ago when I got the Star 71 - the flats were over correcting by a long way (giving bright corners). That was with an average level of 26,000 (1/3 histogram in Artemis), so I backed it off to 20,000 maximum level instead and the problem went away immediately. Ive just checked an old 130pds flat, and that was just under 22k maximum - so its in that genereal ball park area (26k+ is a bit high). Both scopes have a completely different vignetting pattern, so there will be some element of experimentation.

Odd. That's just the point of doing the flats in the first place. As I posted before, because the correction is normalised and multiplicative, as long as the sensor is reasonably linear and the flat is not clipped at either end, it should not matter...

But obviously the range does matter, and your images are a testament to your experience

and to get the SW CC in there I literally had to hacksaw and file off its collar (only for the brave!... or mad).

In regard to the correct ADU levels, aim on the low side - between 16,000  and 20,000 max ADU (not average). 

Kudos to doing the hacksawing, Rob - I chickened out at this point, although I did hacksaw off 15 mm from the OTA at the primary end of my 150 PDS to stop the focuser causing the odd star shapes! Believe me, I was sweating over that one

But why the 16,000 to 20,000 max ADU for the KAF 8300 flats? I've not come across a compelling reason for this in my 'net travels. I'm sure that your experience shows this to be correct, but is there an engineering explanation?

Cheers,

Paul

 An Allen head seems to definitely be needed when trying to hold the weight of all the gubbins.  

I only do it up finger tight! As tempting as it is to use an allen key, the coma corrector is a delicate optical assembly

Thanks for the advice Rob.  

I have bought an A3 LED display for flats and am experimenting with this.  Because of the shutter on the 383 it means that the right amount of light reduction needs to be made to increase the exposure time -  which is a bit fiddly.  Unfortunately the panel can be dimmed but does not dim enough !  Its a question of diffusing the light enough to get to the right exposure I guess. I am also going to look at the T shirt method outdoors but again its getting the right thickness of material to get a long enough exposure !  Bring back AV DSLR flats anyday !

I believe a figure of 25-30k ADU and above 5s should be achieved  to avoid the shutter affect ?

Wrt the coma corrector yes the drawtube focusser scews arent the best and I thought of replacing the complete unit which holds the screws  as it is difficult to tighten the screws with the filter wheel in situ as it is. Haven't researched this yet though.  

From the Atik site the backfocus for the 383 is quoted as 17mm which I assume is from the chip to the 383 mating interface - I guess this is the distance I add to the EFW thickness and then add the CC internal distance to the lens and then also add a spacer if required to get 55mm     Does this sound about right to you ?

I've had good results with ADUs in the range 14,000 to 30,000. I don't think that it's mega-critical as long as you are well out of the noise floor and not saturating the sensor. Flat field corrections in software are multiplictive so, in theory at least, as long as you are not clipped at the black or white ends the corrected results should be the same as long as the sensor is linear. The KAF 8300 is, apparently, quite linear and is used for scientific work.

With regards to the back focus distance, you'll have a fun time sourcing all the spacers that you'll need to get it exact. I found Telescop-Express to be a very useful resource.

The third screw in the eyepiece holder is an absolutely must with the weight of the coma corrector, filter wheel and camera hanging off of the PDS focuser if you want any kind of orthogonality at your chip! I used an M6 allen-head bolt that I have in abundance. There's plenty of metal in the eyepiece holder to take the bolt. Taps and dies are cheap and you just need to find a buddy with a pillar drill (every astronomer should have access to a pillar drill! ). You can see the bolt in this close up:

You might also consider tightening up the focuser a bit too. See here: http://www.teleskop-shop.at/testphotos/w-erbung/Crayford_adjustment_Synta_microfoc.pdf I found that the weight of the imaging gear would slowly unwind the focuser over the evening until I had "corrected" the tension in mine.