Second Light SXVR-H18 - Crescent Nebula

[RichieJarvis]

Hi All,

After have a few teething troubles, I spent last night gathering data on NGC6888.

This image is slightly cropped, but works well I think.

Click here to go to the full sized version and capture details

Thanks for looking!

Cheers,

Richie

[ollypenrice]

Stonking image scale. Could you go for longer subs? Not a user friendly focal length, I know!!

Olly

[harry page]

Hi

Nice scale and great start

Is the rain , from hot pixels that you have not clipped out

Harry

[RichieJarvis]

Hi Olly - yes, i am kinda regretting going for 5 minute subs tbh - but I wanted a 'quick' result during the working week

I hope to add some more to this soon - but the Sadr region of Cygnus would really look good in the Genesis..... Decisions decisions!

Harry - I think the 'rain' came from the flats - not quite sure though. Hopefully my processing will improve with the camera as time goes on!

Cheers,

Richie

[RobH]

Nice image Richie

Looking at the full res though, you still have some vertical streaking (the rain I guess!) and some horizontal issues at the bottom of the image.

Forgive me for asking a daft question, but you did apply temperature regulated darks I assume?

The streaks look very similar to the effect you get with a DSI when the darks don't match the lights temperature wise.

Cheers

Rob

[harry page]

Hi

I have seen bias and dark frames from the h18 and very clean they are.

This is a sx camera and I do not see the need for darks at all , subtract a bias yes , but dont bother with darks

Harry

[RobH]

I wouldn't expect that effect from this camera, but you never know!

I certainly had to use darks with my H16.

Rob

[harry page]

Ah different opinions , never used a dark with my h16 ( in unbinned mode)

A good dither and a sigma stack sorted out any rubbish

Harry

[RobH]

I tend to be rather 'belt and braces' Harry.

I even use darks with my 16HR, as well as a bit of dithering and sigma stacking!

Rob

[harry page]

Hi

there is a thing about adding more noise than you take away with alow noise camera.

When I was looking at the 8300 , it is obvious that it has less noise than the H16

So I am not sure what the noise in the image above is

Harry

[RichieJarvis]

Harry - Terry Platt says you need darks for the H18, due to the much higher noise levels, so I've been running down that route.

Anyway - yes Rob - I think its the calibration frames I was using - I took flats and darks - temp regulated. Just having another stack now with no calibration and sigma on to see how it behaves.

Ok - its worse without darks - see attached

Cheers,

Richie

[harry page]

Hi

Very interesting result , I of to see terry as he seems to have changed his mind

I will admit the kodak chip do have more noise than the sony chips , but nothing that has bothered me

Oh bug-- I have just noticed that this is a Ha shot , this will show a lot more noise , but surprised by the amount

Harry

[ollypenrice]

I still go for the subs length though the 'rain' is odd. One thng I've accidentally done is have the darks the wrong way up.

Richie, the Genesis is a good weapon on this one. I wonder how well it will cover the big chip? I can't wait to see how it does. This was with the 16HR.

Olly

[Astronome]

Richie,

Just about in the same state with the SXVR H18..

Cannot quite get the images right.

Tried short subs (100s) say 30 (M31 standard test galaxy)

Also messed about trying to get the colour right..

Not much success yet. The L image is not bad with 6 darks.

Big issue with AA4 and SXVR H18 was keeping the cooler at the correct temperature. Now I know that the cooler is off while in download I have added a delay of 30 seconds to let it gat back to temp.

What is your view about a total process for M31 say:

I think I will try...

-20C

6 standard flats at twilight

3 darks @ 180sec

20 L filter at 180s

10 R at 180s

10 G at 180s

10 B at 180s

3 darks @ 180sec

stack each set with DSS standard settings (median on darks)

Use AA4 to get RGB and LRGB

Regards,

John

[Astronome]

I would look very closely at the temperatures. I have had a lot of trouble maintaining temperature between darks and L R G B frames.

Looks like a tempaerature mismatched frame somewhere.

The black streaks would seem to be something subtracted like darks. Not flats??

I have found that there are a number of cooler issues with the H18. It turns off on download for a start. It has difficulty maintaining temps of -20C at even 7-10C ambient. Take a look at the fits headers and temp.

John

[RobH]

I've fitted a fan to my H18, and it now holds temperature a lot better.

It is certainly a noisy chip, and you do need darks.

I had to send my first one back as the cooler simply didn't maintain a stable temperature, so it was impossible to match darks.

Rob

[RichieJarvis]

I have the external fan - it was holding -40 ok for me until last week... Now I am using -35.

Aye Rob - it is a noisy [removed word] indeed, but does work

Cheers,

Richie