M51 with CLS filter

[MarkS]

After attempting the Horsehead with the CLS filter from Sidcup, here is my attempt at a faint galaxy on Sunday night.

It's the Canon ESO300D on the C11 with an F/3.3 focal reducer and CLS filter.  19 subs of 5 minutes gives 95 minutes of total exposure.  The red channel ends up being very noisy because so little red light gets through.  The background isn't flat because I don't yet have any flats for this particular focal reducer. 

[Daniel]

Hi Mark, lovely image, love the colour variation in the spiral, which ISO did you use?

[JohnP]

Mark - Not bad for a first attempt esp with a DSLR. You are right the background is yuk... need to sort out flats/ gradients etc. Great start though - it would be interesting to try this at DSC & see what difference the skies make.

John

[Tony G]

Well hopefully this is what I'm trying for, if the weather allows me too.

Tony G

[Mike]

Good image Mark.

I am very surprised about the very narrow field of view you are getting with a DSLR AND a focal reducer!

[MarkS]

Daniel, I used ISO 800 as I usually do (see my explanation in the High ISO or Longer Exposure thread)

Mike, that image is a crop taken from the complete frame.  The complete frame suffers from extremely severe vignetting - in fact, Meade say the F3.3 reducer should not be used with a DSLR but only for dedicated astro-CCDs.

But I thought of it as follows - most of the time I tend to perform 2x2, 3x3 or 4x4 bucketting on the final image anyway unless the seeing is perfect enough to justify the resolution of an 11".  So if I'm going to perform 2x2 bucketting anyway then it makes sense to do the 2x reduction with a reducer in the first place (using a F3.3 reducer instead of a F6.3 reducer).  Why?  Because using the reducer I collect 4x the number of photons per pixel which reduces the Signal/Noise ratio by a factor or 4.  But if I perform 2x2 bucketting on the final image instead, it reduces the S/N by only a factor of 2.

So, for the identical half size image, a reducer will give me twice the S/N of bucketting.    It's a no brainer.  It also means I can substantially reduce the length of my subs without sacrificing the quality of the (already greatly improved) final image.

Time for another attempt on the Horsehead 

[Ian]

is bucketting like binning? Only using buckets?

Just wondering. 

arrrrggg, the pedants are revolting!

[Daniel]

Mark, just wondering how you do binning on a DSLR, and which software you are using for stacking?

[MarkS]

Bucketting?  Binning? 
"When I use a word," Humpty Dumpty said, in a rather scornful tone, "it
    means just what choose it to mean -- neither more nor less."

Daniel, no you can't do on-camera binning with the DSLR (as far as I know).  I do post-acquisition binning using IRIS.  Where possible I use DeepSkyStacker for stacking - it's very easy to use.  But sometimes it fails miserably, in which case I use IRIS.  In any case I do all post stacking operations in IRIS.

[Daniel]

Ahhh, will have to try IRIS, I downloaded it the other day, so will have to try that out, just wondering, you don't use any 3D programs do you, Bucketing is a term we use sometimes when rendering, and it's not a million miles from Binning

[Ian]

ahh, I recognise the term bucketting when you're talking about rendering. How else does the mortar get from the mixer to the wall?

[JohnP]

Ahhh, will have to try IRIS, I downloaded it the other day,

Daniel - good luck & be prepared for a learning curve... It's a brilliant prog & has some great features (esp seeing it's free) but it's not the world's easiest user interface...

John

[MarkS]

Tuesday night's attempt:  this used 10min subs with the C11 guided by the Nikkor 300mm lens with a webcam literally stuffed inside - minimalist guiding!  The lens was mounted on the C11 camera bracket which resulted in some flexing - hence elongated stars.

I'm going to get a proper guide-ring mount to piggyback on the C11.  Then my calculations indicate I need to go to 15 or 20 min subs to reduce those noise levels (part of which are due to over-processing).

[Mike]

Oooh that's a big improvement.

[Mike]

....3D programs do you, Bucketing is a term we use sometimes when rendering..

Are you a 3D artist Daniel? If so, what programs do you use?