Cocoon Nebula with DSLR - Big Problem!

[Tommohawk]

Hi all

Well, down to earth with a bump! Flushed with my recent success with M27, I though I'd give Cocoon Nebula a go. Should be a doddle - M27 is mag 8.1 and Cocoon is 7.2.

So I'm being hopelessly dim here - but why am I struggling to even find it??? Usually I use the goto to a nearby star, apply position correction in Stellarium scope, and then on to my chosen target, then a 30 second exposure to frame it and then away.

I did my 30s exposure and coudnt see anything - figured I was poorly aligned, so back to deneb, realign, back to Cocoon - nothing. Re-did this for about an hour, before deciding my position must be about correct. So did a 5 minute exposure - and there it was - just!! I couldnt match the stars with those showing in Stellarium, but it was a perfect match for image found on the web - so deffo on target (from the outset.... grrr.)

Why so dim?? I upped the exposure to 8 minutes, had fab guiding - best ever - but still the subs were really poor - and by 1.30 am they were just getting worse. Maybe the sensor was on fire by this time... or conversely maybe had condensation. Surely not both! The guide scope had some condensation but the mirror looked OK.

So I can heear you all slapping your thighs and chuckling at my schoolboy error - but what went wrong?? How can I image this? I upped the ISO at some point just for framing purposes - maybe thats the answer - but the magnitude suggest it shouldnt need this.

Any help gratefully recieved!

[Tommohawk]

Quick follow on - I hae yet to figure out how to find the EXIF/Meta data showing CMOS temperature. If I look at the info tag in "Canon Digital Photo Prefessional" it shows load of info but not temperature.

thanks

[Northern Soul man]

Hi Tommohawk, I must admit I'm no imager - have no imaging set up - but it just maybe that the Cocoon (going from memory here so bare with me!!) has a very low surface brightness - M27 has a very high surface brightness and I think a lot more compact than the Cocoon - I've tried many times to hunt down the Cocoon visually with no luck at all, but M27 jumps out of the EP at me.

The magnitude scale of brightness works from a single point of a light source so even if the object is brighter (according to the magnitude scale) if its over a larger area of sky - this makes the object much dimmer than a dimmer, smaller (area of sky covered) one does if that sounds right !!!

Hope that's the correct way of putting it - perhaps I'm totally wrong and you imager's do things different than us " EP lookers" - I'm sure that someone will be along shortly to correct me - dare I say it.

Regards.

Paul.

[oldpink]

the stock filename output from my canon has the date + time + temp along with other info in it
makes it handy to match the temps of the darks & bias files, BYEOS does this for you

[frugal]

Given that you mention Canon, I am going to assume you are using a DSLR. The cocoon nebula emits mostly in Ha, which DSLRs are very poor at recording as they have filters to stop that end of the spectrum from hitting the chip.

So, one of the reasons that it was hard to photograph was that it is not really visible in the part of the spectrum that the camera records.

[Tommohawk]

Hi Tommohawk, I must admit I'm no imager - have no imaging set up - but it just maybe that the Cocoon (going from memory here so bare with me!!) has a very low surface brightness - M27 has a very high surface brightness and I think a lot more compact than the Cocoon - I've tried many times to hunt down the Cocoon visually with no luck at all, but M27 jumps out of the EP at me.

The magnitude scale of brightness works from a single point of a light source so even if the object is brighter (according to the magnitude scale) if its over a larger area of sky - this makes the object much dimmer than a dimmer, smaller (area of sky covered) one does if that sounds right !!!

Hope that's the correct way of putting it - perhaps I'm totally wrong and you imager's do things different than us " EP lookers" - I'm sure that someone will be along shortly to correct me - dare I say it.

Regards.

Paul.

Yep, I think its just faint!! But theres more to it than that....

the stock filename output from my canon has the date + time + temp along with other info in it

makes it handy to match the temps of the darks & bias files, BYEOS does this for you

Dont have BYEOS - will have a look. youd think the Canon EOS utility would have this.. no?

Given that you mention Canon, I am going to assume you are using a DSLR. The cocoon nebula emits mostly in Ha, which DSLRs are very poor at recording as they have filters to stop that end of the spectrum from hitting the chip.

So, one of the reasons that it was hard to photograph was that it is not really visible in the part of the spectrum that the camera records.

Take your point - but I have modded 550D so should pick some up. I've seen some other cocoon DSLR images which look quite good

Have just had a look at my darks - lot of what I take to be amp glow - worst for the early ones which seems odd, and I did the darks before the lights so shouldnt have overheated. Also, not knowing that 5 minute lights wouldnt show enough, I only did 5 minute darks. So I wonder why I have amp glow which I've never had on 5 minute darks before??

Any ideas?

[Tommohawk]

Just noticed that the very last shot was an 8 minute dark - which has no amp glow!?

[Tommohawk]

Further thought! I think I've solved the amp glow issue! I often do darks last by just putting the scope cover on - but yesterday I did them first - still some daylight, so maybe just didnt have the cover on preoperly?? Or leakage through the viewfinder? Would explain why the later ones were better.

[Steve Ward]

I'd leave it 'til later in the year and darker nights are here ... it's not a particularly difficult target then ...  

I shot this in late mid-September '12 with Standard Canon 1000D  through an ED80Pro+FF/FR ..... just 20 x 120s frames @ ISO 200.

[Tommohawk]

I'd leave it 'til later in the year and darker nights are here ... it's not a particularly difficult target then ...  

I shot this in late mid-September '12 with Standard Canon 1000D  through an ED80Pro+FF/FR ..... just 20 x 120s frames @ ISO 200.

Hey thats fantastic!! ISO 200??!! 120s? So what the heck is going on with my set up!!

I dont think light was a problem - my first sub was after 12, and it was pretty black. I did M27 last week with subs taken earlier on a warmer night - minimal condensation on scope at end session

By the end of the session last night  the scope was covered with condensation - so I wonder if that was the issue.

Question - where is condensation most likely to form an a Newt: Sensor, Primary, secondary??

[sidelight]

If you are using windows Infranview will give you temp as part of the the information for an image (click the information button then click EXIF), its a bit of a long winded way round but its there.

Although I try to avoid it, if I do darks during daylight I tend to put the covers on then wrapin with some kitchen foil as well as well.  I find light will leak through the covers if its bright enough.  Don't forget if you are using a newt light will get in through the back of the scope around the primary mirror (and I have also found around the joint where the primary cell is attached to the scope.

Cheers

Ross

[Tommohawk]

If you are using windows Infranview will give you temp as part of the the information for an image (click the information button then click EXIF), its a bit of a long winded way round but its there.

Although I try to avoid it, if I do darks during daylight I tend to put the covers on then wrapin with some kitchen foil as well as well.  I find light will leak through the covers if its bright enough.  Don't forget if you are using a newt light will get in through the back of the scope around the primary mirror (and I have also found around the joint where the primary cell is attached to the scope.

Cheers

Ross

Great - ta for the tip.

[toxic]

when i had due it always started on the secondary mirror.

[Tommohawk]

when i had due it always started on the secondary mirror.

OK ta - I'm out ther now again! Leaving the cover on til ready, and use library darks

[Tommohawk]

Hey Ross.. I think you've solved it!

The problem with both the darks and the lights was light getting in behind the mirror. I'm careful to avoid lights getting in at the business end, but my setup for this meantthe laptop was right next to the bottom ofthe scope.

So the longer exposures just leaked more light,and the more I looked on the web for solutions, the brighter it was!

so.. I've taped all the LEDs, repositioned the laptop, and covered the screen. Looking better!

I'll post tomoz when hopefully I'll have some kind of result.

Thanks again to all!

Tommo

[sidelight]

Fantastic news! Glad to hear that's sorted it.

[sidelight]

I made up a cover for the back of mine using that foam board you get from hobby craft, and a couple of bits of velcro. Once the scope has cooled for a bit I put that on and it seems to stop most of the light leaking into the back of the scope, with some electrical tape around the joint between the tube and the cell as well.

Cheers

Ross

[Tommohawk]

Aaaah - thats better!. Always room for improvement, but I think thats about right. Broke my own rule and over-processed a bit I think - trying to make it look like other people's renditions. For some reason colour look stronger on posted PNG than on my original - not sure why.

Also I now realise I should have framed it off centre to show the dark lanes better. Thanks once again for the input!

17 lights x 300s, 19 darks, 20 bias. ISO800. Shot 31st July/1stAug from 22.33-0013.

[Steve Ward]

Nice result , glad to hear you're sorted ... 

I think it's one of those targets that looks better in wide field , the dark 'snake' is part and parcel in my mind.

[Tommohawk]

If you are using windows Infranview will give you temp as part of the the information for an image (click the information button then click EXIF), its a bit of a long winded way round but its there.

Although I try to avoid it, if I do darks during daylight I tend to put the covers on then wrapin with some kitchen foil as well as well.  I find light will leak through the covers if its bright enough.  Don't forget if you are using a newt light will get in through the back of the scope around the primary mirror (and I have also found around the joint where the primary cell is attached to the scope.

Cheers

Ross

Thanks for this also - at last I can see the temp! It seems really odd that the EOS utility doesnt seem able to do this