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JGM1971

The "No EQ" DSO Challenge!

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On 08/03/2016 at 19:51, nicks90 said:

first effort at using an az mount to the thread

then a quick mess with levels in Gimp, but i have no idea about how to do anything else with it. I really need to sit down and watch some processing videos, but its just finding the time!

and poor focus and horrendous light pollution - you can spot the flame neb!

Great first effort ! Thanks for showing.

I also have been messing and learning with GIMP ( sadly I dont have any AltAz of my own yet , only camera on a tripod stuff so not on-topic for this one !)

So, if you will forgive me I have borrowed your pic and played with a light pollution tool in GIMP (well actually it does not seem to be called that in the GIMP sites, but from a previous life in electronics I sussed that it was a useful thing in the frequency/FFT domain, this message will self destruct in 1/2hr :) ) )

(I dont know what the netiquet is in using other peeps pics so I wil show just a cutdown jpg of your original to show the effect but not steal the intellectuals ! ) ( and it was cloudy/raining outside :) so it gave me something to do, thanks !)

The light pollution is spread across the frame [ and is (in data speak !) called a low frequency signal] and can be got rid of with a suitable filter [ a high pass filter in other speak :) ] to leave only the sharpish stuff like the stars and condensed nebulosity

The tool you want is in Filters > Generic > High Pass Filter (if it is not there in your version of gimp then go to the addons repository and look for high-pass.scm and put in your scripts folder/directory)

PS Edit ,, if that is all gobbldygook I'll happily do a blow by blow account how-to get it installed but didnt want to teach eggs if a hint is all you need about the high-pass tool :)

So, I did this, with a bit of increase in hue>saturation as well :) :-

 

Ori2.jpg

Edited by SilverAstro
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I don't have that installed, but I will certainly be putting it on!

Thanks mate

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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

Edited by The Admiral

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11 hours ago, The Admiral said:

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

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

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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

NGC 7023.jpg

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Have you tried the noise removal tool? Thinking of the background, I tried it on my image back early March and it improved/removed the speckling in the background.

The nebula is lovely looking and great colour. I'd be very chuffed with that.

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What a great topic, it gives me hope ☺

I have taken a few single shot images ( still not got my head around dss) but I'm trying. 

I was quite chuffed with these images considering I was expecting a blur. 

Taken with Star discovery 150p synscan goto alt az, 200p dobsonian and canon eos 1200d

large.PSX_20160305_135258.jpg

M101 pinwheel. 1x47s iso 3200 + little work with photo express app.

large.PSX_20160305_135026.jpg

Whirlpool galaxy 1x30s iso 3200 +photo express 

large.PSX_20160323_111303.jpg

M3 1x47s iso 6400 + photo express.

PSX_20160211_165620.jpg

M31 1x30s iso 1600 + photo express 

large.PSX_20160305_134546.jpg

Owl nebula 1x30s iso 6400 + photo express 

large.PSX_20160205_151604.jpg

Double cluster 1x30s iso 1600 + photo express. 

large.PSX_20160312_174435.jpg

M42 1x30s with orion all in one cam.

gallery_48933_4088_689330.jpg

Comet Catalina 1x10s with dobsonian. 

Nige.

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16 minutes ago, happy-kat said:

Have you tried the noise removal tool? Thinking of the background, I tried it on my image back early March and it improved/removed the speckling in the background.

The nebula is lovely looking and great colour. I'd be very chuffed with that.

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

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6 minutes ago, SteveNickolls said:

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

Steve.

Yes I fancy a go at multiple shot stacking, I did try about 2 months ago but not very good, I'm reading and learning, I have a set of bias ready, darks are no problem it's just dss I'm getting use to. And still waiting for a clear still night  as a slight breeze shakes my cheap scope  ☺

Nige.

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+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

Edited by The Admiral
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Is that the 200p 1200mm on your discovery 150p's mount?

Do like your cluster/glob images.

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43 minutes ago, happy-kat said:

Is that the 200p 1200mm on your discovery 150p's mount?

Do like your cluster/glob images.

Thanks..

The goto mount I only use the 150p....The dobsonian I have fashioned a way to move both axis smoothly by hand, it's a bit awkward but I can get about 10s without trails.

Nige.

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8 hours ago, Nigel G said:

M42 1x30s

Interesting to see what single exposures on AltAz are like , thanks for showing.

I have read (somewhere on the interweb !) that the problem of field rotation varies depending on where in the sky one is pointing and so with M42 now in the west and in one of the 'better'? directions (a little)longer exposures for the subs may be ok ?

Edited by SilverAstro

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6 hours ago, SilverAstro said:

Interesting to see what single exposures on AltAz are like , thanks for showing.

I have read (somewhere on the interweb !) that the problem of field rotation varies depending on where in the sky one is pointing and so with M42 now in the west and in one of the 'better'? directions (a little)longer exposures for the subs may be ok ?

Unusually low objects are harder than high ones, I get around a minute exp time longest. Problem is not field rotation, it's trails. Being un guided is the biggest problem I think.

lower objects limited to 30 - 40s

Nige.

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15 minutes ago, Nigel G said:

Unusually low objects are harder than high ones, I get around a minute exp time longest. Problem is not field rotation, it's trails. Being un guided is the biggest problem I think.

lower objects limited to 30 - 40s

Nige.

large.PSX_20160117_222122.jpg

M42 in January  1x30s iso  6400  canon 1200d

Nige

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6 hours ago, SilverAstro said:

I have read (somewhere on the interweb !) that the problem of field rotation varies depending on where in the sky one is pointing and so with M42 now in the west and in one of the 'better'? directions (a little)longer exposures for the subs may be ok ?

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

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8 hours ago, SilverAstro said:

Interesting to see what single exposures on AltAz are like , thanks for showing.

I have read (somewhere on the interweb !) that the problem of field rotation varies depending on where in the sky one is pointing and so with M42 now in the west and in one of the 'better'? directions (a little)longer exposures for the subs may be ok ?

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!

Edited by The Admiral
Corrected term
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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

 

Edited by SteveNickolls

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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.

 

Field rotation.jpg

 

Ian

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5 minutes ago, Stub Mandrel said:

Doesn't it also depend on your latitude?

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

Ian

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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

Edited by The Admiral
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You are less than a degree different to my location so I will borrow that :D

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4 hours ago, SteveNickolls said:

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.

Thanks Steve, interesting and that is a good link.

I found the one I was thinking of, a pdf by Bill Keicher :- http://www.autostarsuite.net/forums/storage/19/4981/Field Rotation V3.pdf

has some neat pics/charts for various lattitudes and the varying regions of the sky, written for CCDs but I guess the proportionality would be similar for DSLR etc.

 

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