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Walking on the Moon

If you fancy a laugh take a look at my M31


beamer3.6m
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Now this is a pretty poor attempt at M31.

34 x 180s lights

5 darks

15 flats

Light pollution filter (clip in)

Moon was rising

Canon 1100d (unmodded) with Tamron 18-200 lens set at 197mm(!)

I am not sure of the 'f' of the lens as I keep forgetting to check

AZ-GTI (EQ modded)

 

The pros:

Focus

Tracking

Alignment

 

The cons:

 

M31 copy.png

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It's not bad, at least most of it looks in focus.

You generally don't want to use any filter when imaging galaxies as the target is broadband and you don't want to block out any light.

The image also doesn't look like it's been processed as there's no wider detail other than the bright core if you did manage to take 3 minutes per sub (well done), there should be a tonne of detail in it. My first attempt I was taking 10s subs and could see the whole galaxy, my second attempt I was taking 30s subs and more detail still.

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I just had a go at processing it, and there is definitely more in there.   If you live in a location that rquires a LP filter then broadband  is probably not really suitable for where you live.   Moon rising as well, but it has a lot going for it.  Just keep at it and you will get there.

Carole 

Edited by carastro
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Some advice I can offer here is to stretch the histogram on R, G and B separately. This allows you to balance the background to grey and then any other automatic tools you use have a much easier time.

I know pixinsight can't correct the background colour very well until I have balanced it a little with the histogram mixer myself.

 

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I tried Siril but I don't really get it to be honest... my images come out looking awful when I follow the tutorials.

So I opted for Deepsky Stacker ('DSS')for this one and then photoshop with noel carboni astro actions but the 'actions' were not really put into play.

I will post the .Tiff as produced by DSS very shortly

Edited by beamer3.6m
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On 17/09/2022 at 22:30, beamer3.6m said:

Now this is a pretty poor attempt at M31.

34 x 180s lights

5 darks

15 flats

Light pollution filter (clip in)

Moon was rising

Canon 1100d (unmodded) with Tamron 18-200 lens set at 197mm(!)

I am not sure of the 'f' of the lens as I keep forgetting to check

AZ-GTI (EQ modded)

 

The pros:

Focus

Tracking

Alignment

 

The cons:

 

M31 copy.png

First of all congrats! You managed to capture the centre of an object that is 2.5M ly away…. It is not easy!

 

The tracking seems good 🙂

Here is my first attempt ever with the Andromeda galaxy…..

 

A89CEE6F-14EB-4295-B7F5-EB0B088C93A1.jpeg

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54 minutes ago, George Sinanis said:

First of all congrats! You managed to capture the centre of an object that is 2.5M ly away…. It is not easy!

 

The tracking seems good 🙂

Here is my first attempt ever with the Andromeda galaxy…..

 

A89CEE6F-14EB-4295-B7F5-EB0B088C93A1.jpeg

Thank you... I'm loving the mount and the ease of setup...

I think for m31 I need to ditch the cls clip filter and see how it goes too.

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On 18/09/2022 at 11:00, beamer3.6m said:

The .Tiff as produced by DSS

m31.jpg.f34260e298b8720450a92d135b112b27.jpg

You probably don't need darks at all for DSLR, so use bias only and shoot a bit more than just 5 of them

This camera has very low red response (hence very green / teal appearance without proper color calibration), and when color is managed - then a lot of noise in red pops up.

Try stacking with Siril, ditch darks and use bias instead (but more than 5 - like 30-40 of them)

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59 minutes ago, beamer3.6m said:

Sounds like I need a better camera for this???

That is one way of looking at it :D

Let's see if there is something that we can do with the things as they are.

1 hour ago, beamer3.6m said:

So in essence the original data was not good...

What sort of LPS filter did you use, and what is your LP like (ideally approximate SQM or at least Bortle).

Not all LP filters are suitable for every target and LP filter don't help always.

If you by any chance used UHC filter on broadband target like M31 - then first order of business is to ditch LP filter and shoot target again. If you shoot from Bortle 5 or less - you probably don't need filter if it is CLS type. If you are in Bortle 4 or less - you probably don't need special filter like Hutech IDAS P2.

You can shoot bias now. Bias don't depend on temperature (or at least it should not) nor focus position, nor light from telescope so you can shoot it any time. It contains read signature of the camera that needs to be removed (bias signal). You take it by selecting same ISO as you used when taking lights - but instead of lens - put that plastic cover on. Remember to cover finder window with that rubber cap and set exposure to minimum supported.

Record about 30-40 such subs.

Stack your data again in Siril

That might make it a bit better than it is now.

Rest is down to filter used and your LP levels - so that can be tried on your next night out.

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Don't need CLS filter then. CLS filter is a bit aggressive. It works better for emission type nebulae (but not as good as UHC) - but it hurts galaxies and other broad band targets (and reflection nebulae).

In Bortle 4 - you probably don't need filtering at all.

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1 hour ago, vlaiv said:

Don't need CLS filter then. CLS filter is a bit aggressive. It works better for emission type nebulae (but not as good as UHC) - but it hurts galaxies and other broad band targets (and reflection nebulae).

In Bortle 4 - you probably don't need filtering at all.

OK. For my next run then I will do without the filter and see how I get on... and do biases

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5 minutes ago, beamer3.6m said:

Question... do I still need flats or am I just using bias frames (that could be a really stupid question)

Bias goes instead of darks - rest is the same, so yes take flats.

Proper calibration requires darks to be taken. Do this every time when working with dedicated astronomy cameras, but DSLRs are a bit different. They have "automatic dark removal" (sort of). There are dozen or so pixels in each row that are covered and don't get exposed with the rest of pixels - but they do participate in exposure and accumulate thermal signal. These are then used to calculate dark current that is removed from other pixels that were actually exposed to light.

This process removes dark current - but what can't be removed like that is bias signal (signal of reading out pixels and analog / digital conversion units). You would normally remove that in regular calibration as darks consist out of both read out signal and dark current signal, but here since dark signal is automatically subtracted - we are only left with bias signal to be removed - that is why we use bias instead of darks with modern DSLRs.

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21 minutes ago, vlaiv said:

Bias goes instead of darks - rest is the same, so yes take flats.

Proper calibration requires darks to be taken. Do this every time when working with dedicated astronomy cameras, but DSLRs are a bit different. They have "automatic dark removal" (sort of). There are dozen or so pixels in each row that are covered and don't get exposed with the rest of pixels - but they do participate in exposure and accumulate thermal signal. These are then used to calculate dark current that is removed from other pixels that were actually exposed to light.

This process removes dark current - but what can't be removed like that is bias signal (signal of reading out pixels and analog / digital conversion units). You would normally remove that in regular calibration as darks consist out of both read out signal and dark current signal, but here since dark signal is automatically subtracted - we are only left with bias signal to be removed - that is why we use bias instead of darks with modern DSLRs.

Perfect, thank you

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