Stefan73

Here's nearly 12 and a half hours, over 10th,15th and 17th January, of the Flaming Star Nebula (IC 405) through a Stellalyra 10" f/4 newt with a IDAS NBZ nebula booster filter.  Gory details on astrobin.  I screwed up the FOV on one of the sessions so the intersection of all the subs ended up a bit longer and thinner than I'd have liked...  thanks for looking.

I'd guess the dark isn't as dark as it should be.  When I've done darks it hasn't been good enough to just put the telescope cover on, or even to take the imaging train out and put a cap on that, due to light leaks.  I've ended up just having the camera with the cap on in a dark garage or the flats end up over correcting.

That being said I think usual advice is not to do darks with a DSLR and use a constant bias with siril.  For my 550D I used

preprocess light -bias"-2048" -flat=pp_flat_stacked -cfa -equalize_cfa -debayer

I'm not sure what number in place of 2048 you'd use.  I'm not sure you'd really need as many as 120 of the calibration frames but it won't do any harm

A telegizmo cover was the best thing I've ever bought for my telescope. 

No chance of an observatory but a reasonably secure garden so just shoving the cover over it rather than breaking down in the freezing cold was a big quality of life improvement.

I think StellaLyra newts are just re badged GSO scopes so you might have more luck searching for that (or for one of the other brands that rebadge GSO scopes or explicitly search for the focuser). 

The picture of the focuser looks plausibly like a ZWO EAF would fit, and if not I bet there's a 3d printed bracket someone's designed that will make it fit.

Sometimes you need a bit of experimentation with back spacing. The suggested value can be just a starting point.

Probably the best way to get more suggestions would be to post a fits of a short exposure sub of a good star field and a picture of the camera and coma corrector all connected up to the telescope.  It looks like the tails on the stars are all going the same way but hard to see.  Could it be tilt?  Have you looked at a sub with astap or siril's tilt detector?

Definitely try what alacant suggests. 

The only thing I'd add is you can try focusing on something far away during daylight so you don't waste imaging time on faffing with extensions.  You might have to move the focus tube a bit further in when focusing on stars but it should give you a good starting point.  If it's still not working try to work out whether the camera is too near or too far.  It should be a bit more obvious if you're getting closer to focus when at maximum extension or minimum extension.

11 minutes ago, AstroRookie said:

Still no go; if I use 37,5mm + 17,5mm from flange to the sensor, I cannot reach focus at all. Also after having read this thread I'm even more confused. Not using the coma corrector is not an option, as I cannot tighten the spacers in the focuser; did I purchase spacers with the wrong diameter ???

It sounds like you should have a 37.5mm spacer between the camera and the coma corrector and then the coma corrector goes fully into the focus tube clamp; like a nose piece on a camera.  Is that what you have?   Can you see if you're getting close to focus at either full extension or full retraction of the focuser?

If you want to do astrophotography with a DLSR then you're probably best going for the thinnest OAG going.  Something like this: https://www.firstlightoptics.com/off-axis-guiders-oag/ts-off-axis-guider-tsoag9-length-only-9-mm.html

Even if your focus position is fine with a thicker OAG you might want to use a coma corrector in the future and those often have 55mm back spacing so you wouldn't have room for anything thicker in front of the DLSR.  

I've no experience with the 200PDS but the 130PDS was not usable without modification even with the above 9mm OAG as the focus tube was pretty much in as far as it would go to achieve focus and you just got pacman stars without cutting off a lot of the focus tube to stop it protruding.  Using a coma corrector too was fine though.

I'd try to eliminated all the obvious things which might stop the mount responding to PHD2.  Bad USB cables, cable snags, worm gears binding in certain positions maybe.

I had similar graphs with my Samyang / EQ6-R sometimes and I think a cable was getting snagged slightly as it went away with more careful cable management.

7 hours ago, v4169sgr said:

From a practical POV I am not sure what screwing the camera in to the focuser would look like LOL

You need an adapter (for the coma corrector rather than the camera).  Here's a rather expensive example of one https://www.teleskop-express.de/shop/product_info.php/language/en/info/p16454

Might not be possible for the coma corrector you're using of course.

Often the compression ring can be unscrewed from the focus tube which exposes a thread and the corrector can be screwed directly to that.  Maybe post what corrector and newt you're using and someone with that combination might have advice.

I certainly have the same potentially random tilt when inserting the corrector into the compression ring.  I've just got into the habit of taking some short trial pictures first and reseating if needed.

13 hours ago, Mega_Parsec said:

Secondly I looked at the TS GPU 1.0x CC, which I understand would give a better corrected image (and I'd prefer to stay at 1000mm focal length) but I understand that this also impinges on the light path due to its length: 

TS 1.0x GPU Superflat 4-element 2" Coma Corrector | First Light Optics

It's possible it would as I've never used it with a 200PDS but it doesn't with my 130PDS.  It moves the focus position outwards by about 20mm so there less of the tube impinging on the light path.  I've been very happy with it.

44 minutes ago, alacant said:

We neither. I question the need for adding yet another layer electromechanical interference to a train. If anything, our stars improve as the night progresses

By contrast in the UK last night it dropped 1.5C over the first half an hour to hour of imaging I did last night and the 10" F4 GSO reflector I've recently got definitely needed refocusing.  It's just a function of temperature change and a massive metal tube I guess.; I don't think I've ever needed as obviously to refocus my Samyang lens during the night no matter how brutal the temperature change has been.

When it's below zero outside I'm very, very grateful for my AEF and autofocus routines too!

After a lot more replugging and rebooting this does seem to have sprung into life, cameras have connected and seem OK.  I did try it under windows and connected via the unity controller pegasus provide so maybe that made it spring into life.  Anyone else had initial astroberry problems with it?

Has anyone had any luck with the Pegasus USB control hub using INDI?  https://www.firstlightoptics.com/pegasus-astro/pegasus-astro-usb-control-hub.html

I'm trying to use it with INDI and astroberry and my cameras don't seem recognised when I plug them into the hub. 

I can connect to it using the Pegasus UCH driver in one of the Aux slots in the kstars profile, INDI finds it and it gets its own tab but it's like the USB sockets are turned off (but INDI says they're on).  I'm trying to plug in a couple of ZWO cameras FWIW.  Plugging in a mouse does appear with lsusb and the cameras work fine when plugged directly into the pi.  It's all powered with a 25-30A Nevada power supply so it should have plenty of power for the cameras and the USB cables are lindy and work fine connecting directly to the pi.

Is there some magic to making these spring to life?  Is the choice of baud significant here?

Thanks for any help.

10 hours ago, woldsman said:

Why would a gso coma corrector obviate having to address the issue of focuser protruding? Am thinking about getting a 130pds but the focuser mod is off-putting.

If you choose the right coma corrector it can move the focus position further out.  eg I use the GPU one https://www.firstlightoptics.com/coma-correctors/ts-10x-gpu-superflat-4-element-2-coma-corrector.html and the focuser is nearly at full extension with no noticeable protrusion.

I think just setting it to play a sound via ssh should be OK for my purposes (providing it's setup to work passwordless).  The discussion you linked to seems more aimed at getting a notification to appear on a mobile phone, which is a bit trickier.

Tonight looks initially clear with incoming cloud so should be a good test for it! 

That's what I need!  Never noticed that notifications menu before. 

There's a bit of faff getting it to do something on my controlling laptop rather than the pi sitting in the garden but looks good.

Does anyone have any good monitoring solutions for EKOS/INDI when an imaging session is set off?

I generally go off to do something else, leave astroberry in charge and check on it occasionally.  I really want something to shout at me straight away if it fails, often all it needs is the imaging run or guiding restarting. 

Usually it's a passing cloud causing guiding to fail (which I can catch by polling PHD2's guide status over the network with a program and playing a noise when it aborts) but the last one was the CCD started failing to download subs (probably need to finally replace the ZWO USB leads).  I guess I can NFS export EKOS's logfile and set something inside monitoring that but I wonder if anyone has a better solution?

Here's the Cygnus Loop from my Samyang 135mm and ASI2600MC.  This time stepped down to 52mm (the tilt seemed a bit random with it at f2) and using a IDAS NBZ filter.  It was stacked from the best 3 of about 4.5 hours of data spread over 5th, 6th and 7th September and processed with Siril and Startools.  The gory details are on astrobin.  Thanks for looking.

10 hours ago, dobbie said:

hi there is another option that is to change the 150pds to a 130pds which would sit nicely on the eq3.. just a thought, 

I started off with a 130pds on an eq3 and it could just about cope with AP but it was right at the quoted limit for the mount and I couldn't get guiding to work well with it at all.

I would definitely save up for the best mount you can rather than downgrade the scope to try to make the eq3 work a bit better.  Less frustration longterm!

double post. sorry.

Here's my go at the North American Nebula which is also the first proper test of my Samyang 135mm (at F2) with an ASI2600.  No filters and nearly two hours of integration over 10th and 14th August (full details on astrobin).  Not sure I've got the back spacing completely right but it turned out better than I was expecting!  Thanks for looking.

Hi all.

Been trying again to get my Samyang 135mm working properly now the nights are starting to draw in.

I'm using the M48 adapter from here https://www.firstlightoptics.com/adapters/astro-essentials-samyang-lens-to-m48-adapter.html and with that it claims I should need 44mm of back spacing.  I have tried this with ASI 2600 (with tilt adapter still in place), ZWO filter drawer (https://www.firstlightoptics.com/zwo-accessories/zwo-2-filter-drawer-m42-m48-v2.html) and 5.5mm of spacers to gave 17.5mm + 21mm + 5.5mm = 44mm.  This won't reach infinity focus (not even close at f2) and I have removed the little focus stop thing as per various youtube videos.  No filters involved either.

After some experimentation, I could reach infinity focus with 4.5mm of back spacing, and very near to where the focus stops (about 160 steps for the auto focuser) ie with a total back spacing of 43mm.  At that spacing I got the attached 60s sub at f2.  To me its got a slight rotational look to the star trails which I think implies the back focus should be a bit less even(?).  Any thoughts or advice appreciated!  Is the Samyang back focus that variable in practice?  Or is it always 44mm regardless and I'm doing something wrong? What are people using who are happy with their corner stars?

Also what's going on with the bright star in the bottom left quarter (Deneb I think)?  It looks like the sort of flaring with bites out of it that mirror clips on a newtonian cause.  I think Deneb was more or less straight up at the time so shouldn't have been any trees or anything in the way.  Other stars don't seem affected but obviously not as bright.

I've always found a strap wrench invaluable astronomy kit for this sort of thing.  For example:

https://cpc.farnell.com/duratool/d00070/strap-wrench-set-2pc/dp/TL10279