SteveNickolls

Thanks Nige, I'm quite chuffed seeing as the moon was almost full last night. Never expected to capture the areas of nebulosity. Cheers, Steve

Another clear night (last night) so some more images today :-) The first is of the cluster M52 and (just) the Bubble Nebula NGC 7635 in Cassiopeia caught in the same field. Equipment SkyWatcher Startravel 102mm refractor and SynScan alt-az mount plus Canon 600D DSLR. x40 forty second light exposures at ISO 1600, x50 dark frames, x50 flat frames and x50 bias frames. Frames stacked in DSS and processed in StarTools. Second image, open cluster NGC 7510 with the Bubble Nebula and Sharpless 2-158 (NGC 7536) in the same field. Equipment SkyWatcher Startravel 102mm refractor and SynScan alt-az mount plus Canon 600D DSLR. x31 forty second light exposures at ISO 1600, x50 dark frames, x50 flat frames and x50 bias frames. Frames stacked in DSS and processed in StarTools. A close up of the Bubble Nebula taken from the above- And of Sharpless 2-158- There was an almost full Moon affecting the imaging last night so it will be well worthwhile revisiting on a darker evening. Cheers, Steve

Nice composition and lovely colours nige. Cheers, Steve

Hi happy-kat, Yes, an alt-az set up will open up a lifetime of objects to image and that's good news when your local light pollution is bad, your budget is limited or you just want to see if imaging is going to be an interest without making a large outlay of money. I'd go so far as to say it can be the difference between reading about imaging and being able to get out and do some while learning all the time. One downside of alt-az imaging is that the individual length of each light exposure is much shorter in duration than from a EQ set up. In his book, "Astrophotography on the Go Using Short Exposures with Light Mounts" Joseph Ashley mentions that with very short length astrophotography a total integrated exposure time of 120 minutes is desired for an object. On page 87 he gives a guidance chart comparing % frame success rate and exposure time. In practice that is a really long time to be taking light exposures involving a number of realignments due to field rotation and I don't think I have ever been able to take so many light exposures (I also need some sleep). It's worth experimenting of course but I am mindful that in the UK the weather is very much a limiting factor on how many nights you can actually image on! In the short time I have been using my gear to image I have noted that objects such as clusters and globular clusters do not need that many exposures to get a decent final image. Some nebula and galaxies on the other hand can take up as much exposure time as you can manage. Best regards, Steve

That's a cracking image Nige, very well done. Are you going to trial StarTools? +2 to using autosaved FITs file from DSS in StarTools as advocated by happy-kat. Good luck. Cheers, Steve

Thanks Ian It will be the mount. That evening there was little if any wind. I have noticed that after going to an object using the go-to the mount needs a couple of minutes to steady itself before taking any exposures. Cheers, Steve

Hi SilverAstro, Thanks for the kind comment. At 50 seconds exposure it looks like it is the mount limitations that are failing rather than light pollution (at least in some directions) or field rotation. I've been slowly increasing the exposure duration used during imaging sessions and noting the resulting percentage of light frames acceptable to DSS. If an object is in a good location wrt field rotation I have wrung 50 seconds exposure although the percentage of acceptable exposures has dropped to 50%. For M13 the table I use for field rotation values indicated field rotation itself would permit exposing frames to around 90+ seconds. At shorter exposures across a number of sessions I have seen 90% acceptance with 40 second exposures and higher percentages at 30 seconds. I'd suggest everyone try and experiment on taking longer exposures within the mount, field rotation and light pollution limitations. I do add a 3kg weight to the eyepiece tray on the mount to help with stability. Cheers, Steve

Last night I was able to image M46 and M13 using the SkyWatcher Startravel 102mm refractor, Synscan alt-azount and Canon 600D DSLR. The image of M46 also shows the planetary nebula NGC 2438. There was a lot of light pollution to the SW and M46 was quite low in the sky (around 19 degrees elevation). I was hoping to expose the shots for 40 seconds but the live view showed a completely white image with no detail. I ended up using 25 second exposures. The image below is made from x44 25 second exposures at ISO 1600 plus x50 dark frames, x50 flats and x50 bias frames. DSS was used to stack the exposures and further processing was done in StarTools. The sky to the SE was much more agreeable and I was able to take 50 second exposures of M13- The above image was made from x25 fifty second exposures at ISO 1600 plus x50 dark frames, x50 flats and x50 bias frames. Equipment as for M46. Just above the 9 o'clock position the galaxy NGC 6207 can be seen. DSS was happy stacking half (x25) of the x50 fifty second exposures taken so I think if this is repeated for other targets in the future I am reaching a maximum exposure time for my mount. Cheers, Steve

Morning Ian, Sorry to steal your thunder there, it was after all your splendid advice to me to get the book in the first place. Cheers, Steve

Hi SilverAstro, yes the length of time you can successfully image using an alt-az mount will vary according to a number of factors including the latitude of the observer (in the Northern hemisphere the further north the better); the altitude of the object (lower being better) and the azimuth angle of the object (better to the East and West). This is all explained and tables for each ten degrees of observer's latitude are shown in the excellent book, "Astrophotogrphy on the Go" by Joseph Ashley ISBN 978-3-319-09830-2. I have tailored a more personal rotation chart for my latitude and use it each time I'm planning an imaging session. While the earth keeps rotating all the time the effects of field rotation may mean you don't need to realign your target object through a long imaging session. If you use a stacking programme like DSS it will 'allow' for field rotation effects even meaning you can combine imaging over different sessions. There is an individual ceiling on what your equipment will allow in terms of exposure time of course including your mount design and local light pollution. There are some things you can do to slightly improve your mounts capability as explained in the book. So far I've increased my maximum exposure time to 40 seconds with DSS still happy with over 90% of the light frames collected. I have come across this site-http://daltonskygazer.com/alt-azimuth-mount-tracking-movement-and-field-rotation/ which also explains things and has tables for each 20 degrees of latitude. Best regards, Steve

Hi happy-kat, Thanks for the kind comments. As you know I'm still learning StarTools (do you ever stop?) but will see what further experimenting with the noise removal tool provides. Thanks for the idea. Nigel G you have some good one shot images there. Are you going to attempt multiple images next and stack in DSS? That will improve detail and colour. Keep up the good work! Cheers, Steve

Hi I have recently been re-stacking and reprocessing some of the images taken now I have a better understanding of both DSS and StarTools. I attach an image of the Iris Nebula which now shows more colour and some detail. The original frames were taken on the 7th March 2016 and involved x100 thirty second light frames, x50 dark frame and x50 bias frames. Stacking was done in DSS and subsequent processing in StarTools. The equipment used was a SkyWatcher Startravel 102mm refractor on a Synscan alt-az mount and Canon 600D DSLR. Regards, Steve

Hi Ian, Thanks for the correction. Yes, I did mean 30 seconds (30 minutes would indeed be good to have). Hi happy-kat, Yes these file types are a mystery to be sure. I see Ian has started a thread where we might get to understand some more about the different file types and the influence on the resulting image. All power to your alt-az imaging. Cheers, Steve

Hi happy-kat, thanks for your kind comments. From what I have read the unofficial StarTools Manual says on page 23, "... if you use Deep Sky Stacker to stack your images, have it output FITS files (not TIFF) and try using the Autosave.fits file if you find that ‘regular’ saving outputs a stretched or modified image." This came as an epiphany to me and I took the time to compare file sizes from what I had produced from my imaging. The autosaved FITs file is a lot bigger than the autosaved TIFF and the autosaved FIT file is often twice as large as the FIT file I routinely (or 'regularly' in the vernacular of the manual) saved into the object's folder. Examples of some file sizes from imaging M51 recently are- Autosaved FIT 302MB My 'regular' saved FIT 151 MB Autosaved TIFF 127 MB My 'regular' saved TIFF 154 MB I don't know what the differences in the autosaved FIT/'regular saved FIT file are but a FIT file seems to give much more colour to an image than a TIFF file. Cheers, Steve

Thanks Ian, I realise we are all learning, the latest two images owe a lot to stumbling over the importance of using the autosaved TIF images out of DSS and not the ones I have been blithely saving to file which can be down to half the size of the autosaved files hence affecting colour. Also tweaking the 'Amount' slider and the 'Small Detail Bias' slider in StarTools' SHARPEN module really brings out finer detail. I'm going to have a play with my earlier images to see what SHARPEN can do for them. It's also nice to find it is possible to expose beyond the usual 30 seconds with alt-az mounts provided the object is appropriately positioned in the sky but with local light pollution being an important factor limiting longer exposures. I'd recommend folks trying longer exposures. Ad Astra! Steve

Hi, I have two recent images after experimenting taking 40 second exposures with the Synscan alt-az mount. The first is of M51 taken on the 17th March 2016, x113 light exposures of 40 seconds duration each at ISO 1600, x50 dark frames and x50 bias frames. The exposures were stacked in DSS and the resulting autosaved TIF image used in StarTools. My equipment was a SkyWatcher Startravel 102mm refractor on a Synscan alt-az mount and Canon 600D DSLR. The imaging conditions were not ideal, plenty of moisture in the air and a 71% waxing Moon that night. The second image is of M63 taken on the 30th March this year using the same equipment as for M51 but using x85 40 second light frames, x50 dark frames and x50 bias frames were stacked in DSS and the master autosaved image processed in StarTools. Imaging conditions that night were better with the Moon out of the way and less moisture in the air. Cheers, Steve

Sorry calli, my omission. The SkyWatcher Startravel came with a Synscan Go-To alt-az mount. Cheers, Steve

Two more images to post from last night, firstly M51. This is my second attempt imaging this object this time I used x100 thirty second exposures at ISO 1600 plus x50 dark and x50 bias frames. The equipment was a SkyWatcher Startravel 102mm refractor (f/4.9) and Canon 600D DSLR. The frames were stacked in DSS and the master resulting image processed in StarTools. The keen eyed will notice some other smaller fainter galaxies in the frame :-) And here is my first image of a globular cluster (M3), taken with the same equipment as M51 but using x50 light frames plus x50 dark frames and x50 bias frames. Stacking and processing as for M51.