The Admiral

Hi Ahmad, welcome to the forum. That's a great start, and yes, one can take astro-photos with an Alt-Az mount. And of course it's a great introduction to the subject without the extra complications of an EQ mount, but you can always migrate to that later. The principles will be much the same. With 10" of aperture you should be able to hoover up photons and make short exposures more profitable, and you should get some decent resolution too. The down-side of course is that at f/10 you have a very long focal length which will magnify any mount tracking errors. Have you thought of using a focal reducer with your kit, for astro-photography? Setting up your mount initially can make a big difference to its performance, like levelling, precisely setting your location and time, and centring your alignment stars. There are 2 aspects really, the general tracking performance, i.e. how well it keeps the object centred, and the fine-ness of its movements. One thing I have read is that if you don't have many darks then you are likely to introduce noise into the image, rather than reduce it. I think you'll need 50 or more. Likewise, the more subs you take the better your result. Another improvement you can make is to use the RAW output of your camera rather than JPEGs. I think DSS will process your Canon RAWs directly. The downside though is that you'll need a heck of a lot more hard disk space . What do you use for post-processing? There are a number of specialist applications around, varying from cheap to darned expensive, and there will always be a learning curve, but generally you can download a free trial, which I'd thoroughly recommend. I'm not sure that you can get an autoguider for Alt-Az mounts, unfortunately. I can recommend this book as an introduction to short exposure astrophotography< "Astrophotogrphy on the Go - Using Short Exposures with Light Mounts " by Joseph Ashley ISBN 978-3-319-09830-2. Anyway, there's lots of good advice here on the Forum. Ian

That's a good start VSOP, very vibrant for just a single frame. Are you planning on taking a few dozen and stacking them? Ian

Yes Nige, ST is extremely resource intensive and you ideally need a fast PC running 64-bit. There are of course other specialist programs, some of which are very expensive and require substantial study if you are to get anything decent out. Getting the optimum exposure is a bit of trial and error, in the knowledge that at high altitudes the mount may not need to make such great movements, but field rotation is at its worst, and at low altitudes you have to contend with poorer seeing. Your images have come out rather well; I like M13 best. Ian

That's a great start Nigel; if that's come out of DSS then ST should have an easy task. +1 to happy-kat's comment re the autosaved FITS file. Ian

A well deserved comment there Steve, some rewarding images you've got there. I like the colours. To what extent do you think 50 second exposures were affected by any breeze, rather than the mount itself? Ian

Well that looks like a very good start Ken, it's a pity the clouds stopped your activity. I don't know how you are processing your image, but you might find there is more there that could be teased out, but ideally you'll need many, many more subs. But at the end of the day, it depends what sort of image you are after. Ian

Hi Nigel, good grief, 90,000 stars! No wonder it's taking an age chugging through that lot. It's probably counting noise. It only needs a hundred or so I believe. Have you tried raising the star detection threshold in the "Advanced" tab in the "Register Settings" window that pops up when you start the register process? Also, what files are you loading in to DSS? Ian

Yes it is happy-kat. I tried to add that in a series title in Excel, but MS defeated me on that occasion! It' a plot of imaging time vs azimuth for various altitudes, in 5 degree steps. Ian

Yes it does. The graphs are for my location in the UK. Ian

He he, thanks Steve! I like graphs! The following might be useful - I've put the data from the RASC site into graphical form, and used 0.1° rotation limit. Ian

I've found this article to be instructive: http://calgary.rasc.ca/field_rotation.htm The issue is both field rotation and trailing. Field rotation isn't too much of a problem so long as you aren't wanting to image near the zenith, and East and West are preferable, but I tend to image towards the South and 30 seconds is fine. Steve Nickolls has used 40s successfully. Star trailing I guess is an issue connected with the mount movements and effective magnification, and if it is excessive I believe DSS has a problem identifying stars. I'm using a FL of 715mm with an AP-S camera, and it's been OK. It's always worth experimenting and seeing what you can get away with. I've found the book by Joseph Ashley "Astrophotography on the Go - Using Short Exposures with Light Mounts" a good introduction the art. Ian Ah, Steve's beaten me to it!

+1 to Steve's comments, and with the photon hoover you've got there Nigel G, just think what you could achieve by taking multiple images and stacking them! It's the processing which can make or break your result, in my view, and DSS isn't really so bad once you get the hang of it, but make sure you have the latest version. You should be able to load your camera's RAW files straight in (and I strongly urge you to use RAW if you aren't already). Ian

I've had a quick play with DSS to see what differences there are between the autosave TIFF and FITS files. In this sample, the TIFF was 114MB and the FITS 186MB. I had wondered if they were of different bit-depth, but opening them in my trial copy of PixInsight, I see that both are 32-bit floating point 3 channel files. What explains this large difference in file size I can't imagine. Perhaps I'll make a general post on this. Ian

Steve, did you mean "...beyond the usual 30 seconds with alt-az mounts..."? Yes, there are a number of 'save' options with DSS, and it's a bit of a mystery, to me at least, exactly which does what. I'm glad that you are making headway. Ian

A couple of good'ns there Steve. Keep 'em coming. Ian

Not wishing to teach you to suck eggs, Olly, I'd check that the bubble levels are accurate. On mine I've found that the indication differs depending on its orientation, i.e. level one way, but not when rotated! Also, the sticky pad underneath is a foam. Ian

Nice clear image happy-kat, one doesn't often see an open cluster in such a wide star field. If you are going to use darks, then I am led to believe that you need to do a good number of them otherwise their poor statistics can be detrimental to the final image, because collectively they have to be subtracted from every light. "What I don't like is that tracking automatically switches off after 30 minutes and I can't do anything about that" That's a real pain. Do you have to re-align each time that happens? "There is a slight gradient left" Can't says I noticed! "I am on the 32Bit XP compatible version" Isn't that a bit slow? Star Tools needs some serious grunt. Ian

Thanks happy-kat. Intervalometer - not half! Fortunately my camera has one as a built-in function, so everything is nicely self-contained. Ian

Here's another from last Sunday, 13th March. In these parts the sky seemed very good, and I had a go at bagging M51, the Whirlpool Galaxy. I ended up taking 220 x 30s frames, and stacking 202 in DSS and processing in Star Tools. I had to re-centre a couple of times during the run. Yes, I know it's a lot of subs, but total exposure certainly makes processing a bit less problematic, and it's easier to get the colour. I call it an AltAzograph! The keen-eyed should see a faint galaxy on the RHS; will need to identify that. Details: Altair Wave 102mm f7 SuperED APO, Fuji X-T1, Nexstar 6/8SE alt-az mount. 13th March 2016.

That's a good start nicks90, and you'd be surprised at what might lurk in the image! As you say, the Flame neb is visible, but you really need a lot more frames. With those 'scopes and an interchangeable lens camera, how about fitting the camera to the 'scope? Ian