The EQ3 DSO Challenge

[happy-kat]

43 minutes ago, Knight of Clear Skies said:

Comet Catalina passing close to M101 back in January

Didn't you take a great shot of comet Jacques passing the garnet star the year before?

Crickey found it October 2nd 2014, but was a cracking animation

Edited November 24, 2016 by happy-kat

[Knight of Clear Skies]

17 hours ago, Stub Mandrel said:

That's a smashing shot, you'll excuse me if I try to replicate it!

By all means, go ahead.

16 hours ago, happy-kat said:

Didn't you take a great shot of comet Jacques passing the garnet star the year before?

Crickey found it October 2nd 2014, but was a cracking animation

Thanks, I really must go back to it sometime and fix the colour balance. I hit comet Jacques by accident on that occasion but since then I've kept an eye on the brighter comets for imaging opportunities on Heavens Above.

[Knight of Clear Skies]

Thanks for reminding me about it, here's a version with a better colour balance:

(135mm lens, each frame is a 2 minute sub so it shows the movement of Jacques over about 50 minutes.)

Edited November 25, 2016 by Knight of Clear Skies

[Nigel G]

That's great, I like that a lot , well captured. 

 I like the comet link too, saved to favourites .

Thanks for sharing.

Nige.

[Galactic Wanderer]

Hey guys, 

I was wondering if you could help me with some shots I took of The Pleiades a  couple of nights ago . This was the final shot - but I don't seem to be getting any dust around the stars even with a stretch. This is an hour exposure with an astronomik CLS filter on a EQ3 with an 150PDS. 

Thanks, Seb 

[wimvb]

In this case it's not the total exposure time (integration time or time on target) that is important, but the single sub exposure time.

If you want to catch weak detail, you need to let the system collect photons. Weaker target = less photons per time unit. The total integration time can only help to decrease noise (to a certain limit), it will never increase the signal. Assuming that you use a DSLR, with a target like this you would use a low ISO setting which gives you more dynamic range, combined with longer subexposures. Subexposure time is limited by either light pollution or the stars becoming over exposed. To get the noise down, you need lots of subs.

In processing, you need a tool to remove the light pollution. My favourite is PixInsight DBE, but Photoshop GradientXterminator probably works as well.

Good luck,

[Nigel G]

Unmodified camera, I would suggest trying without the filter, with m45 I got a much better result without my CLS CCD filter in.

Try a single sub and see if there's a difference.

Nige.

[Stub Mandrel]

That's odd, the blue dust seems to be easy to capture and modded cameras don't make any difference to it?

[happy-kat]

Is it really one single exposure of an hour?

[Nigel G]

1 hour ago, Stub Mandrel said:

That's odd, the blue dust seems to be easy to capture and modded cameras don't make any difference to it?

My point being with an unmodified camera the CLS CCD filter can reduce a fair amount of light.

[iapa]

On 14/10/2016 at 22:37, wimvb said:

Later I learned that this is supposed to be impossible, so I couldn't reppeat it.

Therein lies the rub, when you have completed something successfully and people say "you can't do that" you doubt that it is what you did and often convince your self that the setting you quoted where not what you actually used.

 

[Galactic Wanderer]

19 hours ago, happy-kat said:

Is it really one single exposure of an hour?

Sorry for the misunderstanding - it was about 50 80 second expoures

 

21 hours ago, wimvb said:

In this case it's not the total exposure time (integration time or time on target) that is important, but the single sub exposure time.

If you want to catch weak detail, you need to let the system collect photons. Weaker target = less photons per time unit. The total integration time can only help to decrease noise (to a certain limit), it will never increase the signal. Assuming that you use a DSLR, with a target like this you would use a low ISO setting which gives you more dynamic range, combined with longer subexposures. Subexposure time is limited by either light pollution or the stars becoming over exposed. To get the noise down, you need lots of subs.

In processing, you need a tool to remove the light pollution. My favourite is PixInsight DBE, but Photoshop GradientXterminator probably works as well.

Good luck,

Wim, that is really helpful. I was very puzzled when the Orion nebula came out with an hour of 30 second subs and was not even close to the 30 mins of 80 second exposures.

20 hours ago, Nigel G said:

Unmodified camera, I would suggest trying without the filter, with m45 I got a much better result without my CLS CCD filter in.

Try a single sub and see if there's a difference.

Nige.

Here is a single sub with out the CLS filter. I will try in RAW next time though.

Thanks, seb

[Nigel G]

Seb, what camera are you using and at what ISO setting.

With 60s sub's and my Canon 1300d I used ISO 1600 and could see most of the nebula around the 2 main stars in each sub.

Nige. 

[Galactic Wanderer]

This was a very low ISO (100) - I took this a good month ago and then I always used Iso 100 (didn't know a whole lot about imaging then 

Living in London means that you cannot go higher than ISO 1250 - the sky will be washed out.

The subs which I took with CLS filter were ISO 1250 and 80 second exposures.

All of this were taken with a Canon EOS 60d.

Thanks again, this thread has been very helpful in terms of imaging.

seb

[Nigel G]

Definitely need to use RAW files.

Will make a big difference with processing.

Nige.

[wimvb]

+1 on the need to use raw files. There are several good programs to view and process raw files. All astro imaging software can handle raw images directly, and if you wish to process single frames or your daytime images, you can use RawTherapee (free) or something similar.

[Galactic Wanderer]

Hey guys,

I have come back to M45, this time without the CLS filter and with RAW files but still no nebula! Even after stacking I cannot find a single trace of dust and gas. This time I used 80 second subs instead of 60 second to get a slightly higher exposure length. I am very confused -  

Any help would be much appreciated - Thanks Seb

 Here is the final image - 

[alacant]

Hi. I had the same. Third time lucky, having started an optimistic 30s then 60s, I finally got dust with a 6" f5 at two minutes. HTH.

[Galactic Wanderer]

 

22 minutes ago, alacant said:

Hi. I had the same. Third time lucky, having started an optimistic 30s then 60s, I finally got dust with a 6" f5 at two minutes. HTH.

Nice image! Did you just use the Bresser scope  with the camera? Thanks

[Stub Mandrel]

The dynamic range of that image is TINY, what are using to stack?

Also can you post a link to the unmodified DSS stack?

I think you may either have far too much background light pollution or moonlight or something is not happening right.

Look how much bigger my stars are than yours - the 150P-DS ought to be bringing in far more light at 80 seconds with such a high ISO.

This is 21 60-second exposures at ISO1600, chosen as it doesn't show a lot of gas:

[Galactic Wanderer]

Just now, Stub Mandrel said:

The dynamic range of that image is TINY, what are using to stack?

Also can you post a link to the unmodified DSS stack?

I think you may either have far too much background light pollution or moonlight or something is not happening right.

Look how much bigger my stars are than yours - the 150P-DS ought to be bringing in far more light at 80 seconds with such a high ISO.

This is 21 60-second exposures at ISO1600, chosen as it doesn't show a lot of gas:

Living in London really limits me and this is probably the reason - I need to try imaging somewhere else in the Uk!

[alacant]

13 minutes ago, Galactic Wanderer said:

Did you just use the Bresser scope

I used a coma corrector too, although it's not that bad without and you avoid those halos around the stars. HTH

[alacant]

1 hour ago, Galactic Wanderer said:

come back to M45

Hi. There's something of nebulosity I think. Maybe worth stretching again?

 

[Galactic Wanderer]

19 minutes ago, Stub Mandrel said:

Also can you post a link to the unmodified DSS stack?

Sorry here, I have compressed one but the other is completely unmodified

Alacant, yes I will have another go, thanks

Pleiades M45.TIF

[bobro]

Hope EQ2 imagers can post here too ! Couple of ISO1600 images at 2 minute exposures from a beginning imager. EQ3 stuff is far too expensive!