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M13, M27 etc


Cosmic Geoff

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Here are some EEVA-style images made with a 102mm f5 Startravel, SLT mount and ASI224MC planetary camera. I don't claim that they are very good, but would point to the modest equipment used (the camera cost more than the OTA did) and the fact that these are single exposures of about 5 seconds.

I have previously tried imaging globular clusters with a C8 but the results were dire.

One should also compare them with the eyeball view through a telescope of twice the size.

I also tried imaging the region of Pluto, but on interpreting the result it appears that I missed the planet's position and also was not giving enough exposure to pick out objects that faint.

13_00001.jpg

27_00002.jpg

m57_00002.jpg

Edited by Cosmic Geoff
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I am not sure 5 seconds will be enough time to get down to the 14th mag to should Pluto, I tried it the other night with 4 minutes, and as much as I got a result and for sure Pluto would have been there, where was the question though in 1000's of stars. Keep it up and try slight longer exposures, try an get a good Polar alignment too.

Alan

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18 hours ago, alan potts said:

Keep it up and try slight longer exposures, try an get a good Polar alignment too.

I'll keep trying and hope to get something before this Pluto region is lost to twilight later in the season.

Edited by Cosmic Geoff
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Sorry Alan is right a single 5 secs is far too short for anything other than the brightest object - unless you have a very fast scope (F2.5 - e.g. Hyperstar adapter for your C8 - ouch) . Plus a colour camera is not as sensitive as a mono. So work with what you have 🙂 

Dont try and do 5secs that's not what EEVA is about (unless you have the very expensive kit) really and nor is the image quality (for most IMO in EEVA) .

Adjust your times to suit your kit and the object you are looking at.

You didn't say what software you use  (or I was blind to miss it-sorry) but have you tried to use Sharpcap and its "realtime" Stacking option. You should be able to get "decent" images even with your C8 at native Focal length. Just needs some playing with.

All ways are EEVA - choose what YOU are happy with.

Keep trying !!!! best of luck. 

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Re Pluto, I am still assessing the problems associated with trying to image this minor planet.

Clearly a 5 second exposure is nowhere near long enough.  From my location, the sky glow looked like it might limit what I could do with the f5 Startravel 102mm and the ASI224MC camera.  There is also the question of the GoTo - the SLT mount mostly works well enough with the Startravel to drop an object into the field of a ASI224MC  or ASI12MC camera, but it can be temperamental and on this occasion missed the target.

I tried on later nights with a CPC800, which allows longer exposures, apparently recording fainter stars. The problem now is the GoTo: the accuracy of the CPC800's GoTo is reckoned to be about 6 minutes of arc, which  sounds good until one notes that the camera field is now only about 6x8 minutes of arc.  In practice it persistently misses the target area. Last night having become familiar with maps of that part of the sky I was able to nudge the FOV over to the right place.

It probably needs more exposure than 20 secs and the star images are very blurry, possibly due to atmospheric turbulence rather than focus (tried that).

I will probably investigate how the techniques suggested above help push the envelope.

I have tried Sharpcap's live stacking, and have found that it only works when there are several brightish stars in field on which it can align - often there aren't. 

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When I have had mounts that are not particularly accurate; take as much time as is needed to polar align - I did it 3 times last night and kept adjusting until I was happy.  Then I sync to the nearest bright star to the object of interest, then sync to the next nearest star if available, then go for the object and hope. Mike

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Hi Geoff

I seem to recall capturing Pluto in a 1s exposure with a sensitive mono camera (large pixels) on a 8" f4 scope. I don't recall what the skies were like but probably in the range SQM 19.5 to 20.5. With skies of SQM 20 and a target of mag 14 I estimate an SNR of around 28, which makes it easily detectable. As others have said, the combination of a slower scope, less sensitive sensor and brighter skies will knock you back. Even so, I'm going to stick my neck out and bet that it *is* possible for you to detect it in under 5 seconds with your kit and skies. Mag 14 is quite bright for a point source.

It is worth making a test shot of any known star field (e.g. an open cluster where magnitude data is available) and estimate what magnitude stars you can detect in say 1s, 2s, 5s etc. A good object is NGC 6910 in Cygnus for this test. I've attached a single 10s sub where I estimate I can get down to mag 17-18. Doing a good stretch and inverting will help bring out the fainter stars.

Finding Pluto is another issue. Taking a shot on 2 or 3 successive nights and animating is the easiest approach (except for getting 3 clear nights in a row!).

cheers

Martin

 

NGC 6910

NGC6910_inverted.png.00ac698fc6b4c98596cd284d32d34f9b.png

 

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17 minutes ago, Martin Meredith said:

Hi Geoff

I seem to recall capturing Pluto in a 1s exposure with a sensitive mono camera (large pixels) on a 8" f4 scope. I don't recall what the skies were like but probably in the range SQM 19.5 to 20.5. With skies of SQM 20 and a target of mag 14 I estimate an SNR of around 28, which makes it easily detectable. As others have said, the combination of a slower scope, less sensitive sensor and brighter skies will knock you back. Even so, I'm going to stick my neck out and bet that it *is* possible for you to detect it in under 5 seconds with your kit and skies. Mag 14 is quite bright for a point source.

It is worth making a test shot of any known star field (e.g. an open cluster where magnitude data is available) and estimate what magnitude stars you can detect in say 1s, 2s, 5s etc. A good object is NGC 6910 in Cygnus for this test. I've attached a single 10s sub where I estimate I can get down to mag 17-18. Doing a good stretch and inverting will help bring out the fainter stars.

Finding Pluto is another issue. Taking a shot on 2 or 3 successive nights and animating is the easiest approach (except for getting 3 clear nights in a row!).

cheers

Martin

 

NGC 6910

NGC6910_inverted.png.00ac698fc6b4c98596cd284d32d34f9b.png

 

Would submitting a sub to Astrometry not automatically annotate Pluto, or does it not include planetary orbits?

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14 minutes ago, Martin Meredith said:

I haven't used it so you may be right, but it is more fun trying to spot it 'manually' 😉

Very true 😏

A few subs over a few nights, then using AstroArts flicker function should help spot any movement.

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If you can get only one night's image it is possible to put the image into All Sky Plate Solver together with telescope and camera data. Once the image is solved you can move the cursor to the candidate 'star' and check the RA and Dec. It's a bit of a palaver to download and set up ASPS but it's useful for identifying quasars etc. using this technique and it can automatically label NGC objects, which can be handy. I don't think Astrometry Net has solar system information in it. I don't think you normally put date and time information with your image (although some FITS images will have this stored in metadata).

Good luck with your search.

 

 

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Thanks for the suggestions.  My most recent effort with the 8" SCT was discouraging (I imaged some very blurry stars that I could not identify, somewhere near Pluto).  I think I will try the 102mm f5 next time and see if I can get the platesolving to work.  M57 is a popular target and I think the faintest star I captured next to it with the 102mm is about mag 14, but that was near the zenith.

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  • 1 month later...

Geoff, 

I think your efforts are great regardless of your equipment.  I have tried with a dslr and the Ioptron Skyguider Pro and did not have the quality of images you posted.  I really enjoyed them and best of luck in the future.  Keep posting they are an inspiration to myself and all others starting in EAA.

 

Mike

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