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M51 Using .85x FR on my ED80...is it any good? UPDATE!


oymd

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100 x 120s subs

Here's a better result after it was kindly re-processed by one of the gents here on the forum..

Many thanks @geeklee

 

image.png.0bdd27014083fa614b877b36a764d213.png.35a1daf7f4cae1085eefcd2c7d95bb84.png

 

 

 

 

 

1775301055_M51oldflats.png.9f957141339c316a6628a09cc01aef53.png

Yesterday night I tried the FR for the first time.

Not sure why it messed up my live view in APT, and how I frame the targets? Live view kept jumping to 4x4 binning, and I had to force it back to 1x1.

When I completed the sequence, even though M51 was dead center on my screen, the resulting FIT files showed M51 in the image corner?

DId I mess up something, or is it because of using the reducer for the first time, and I should have chnaged something in the settings?

Here is the outcropped image:

 

M51 old flats uncropped.png

Edited by oymd
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Hard to know why it's off centre, maybe you had clicked on it on APT, and it was centred in the zoomed-in image?

You cant use old flats - you need to take new flats, and that will make a significant improvement to the image and make it much easier to process.  The spacing looks ok, there might be a bit of drift going on as the stars are slightly elongated.

However it's an excellent start, and looks like a great setup.

 

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27 minutes ago, oymd said:

When I completed the sequence, even though M51 was dead center on my screen, the resulting FIT files showed M51 in the image corner?

Hi @oymd I have the same scope and FR/FF - it wouldn't cause any odd issues optically like a target moving.  Were you zoomed in at 1:1 or anything like that in Apt while framing?  M51 looks like its close (ish) to being in the centre of the top left quadrant as though it was centred while zoomed in on the preview (when framing).

image.png.f98f3672dfae622b3b3deec99d71c412.png

EDIT: beaten to it 🙂

Edited by geeklee
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4 minutes ago, tooth_dr said:

Hard to know why it's off centre, maybe you had clicked on it on APT, and it was centred in the zoomed-in image?

You cant use old flats - you need to take new flats, and that will make a significant improvement to the image and make it much easier to process.  The spacing looks ok, there might be a bit of drift going on as the stars are slightly elongated.

However it's an excellent start, and looks like a great setup.

 

 

3 minutes ago, geeklee said:

Hi @oymd I have the same scope and FR/FF - it wouldn't cause any odd issues optically like a target moving.  Were you zoomed in at 1:1 or anything like that in Apt while framing?  M51 looks like its close (ish) to being in the centre of the top left quadrant as though it was centred while zoomed in on the preview (when framing).

image.png.f98f3672dfae622b3b3deec99d71c412.png

EDIT: beaten to it 🙂

Yes, I recall I saw a setting suggesting 1:1 or 1:1 fit or 1:1 with scroll. Something like that. 
and yes, now that you say that, in live view, M51 was unusually LARGE and dead centre. 
I thought that was the effect of the reducer!

silly me...

So, how do I undo any silly things I do with binning, zoom etc in the future?

do I  choose 1:1 fit or which one? 
 

lastly, is my focus ok?

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7 minutes ago, tooth_dr said:

Hard to know why it's off centre, maybe you had clicked on it on APT, and it was centred in the zoomed-in image?

You cant use old flats - you need to take new flats, and that will make a significant improvement to the image and make it much easier to process.  The spacing looks ok, there might be a bit of drift going on as the stars are slightly elongated.

However it's an excellent start, and looks like a great setup.

 

But aren’t the flats unrelated to the reducer change?

do you mean that since I’ve taken new images with a reducer, I need to redo flats with the reducer in place?

oh, yes of course. I’m an idiot....

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5 minutes ago, oymd said:

So, how do I undo any silly things I do with binning, zoom etc in the future?

do I  choose 1:1 fit or which one? 

Not sure about the binning, but for zoom it's OK to use all the "views" you mention, just double check that when you think you've finished framing it's set to On (Fit).  This should show the whole frame on screen.

image.png.77d7093cb820c3aa60eedeb8870f6c66.png

At any time, you can double click on your image to switch between On (1:1) and On (Fit).  Wherever you double click going from fit to 1:1 will zoom into that particular area.

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10 minutes ago, geeklee said:

Not sure about the binning, but for zoom it's OK to use all the "views" you mention, just double check that when you think you've finished framing it's set to On (Fit).  This should show the whole frame on screen.

image.png.77d7093cb820c3aa60eedeb8870f6c66.png

At any time, you can double click on your image to switch between On (1:1) and On (Fit).  Wherever you double click going from fit to 1:1 will zoom into that particular area.

Excellent. Very clear. Thanks. 

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11 minutes ago, geeklee said:

Not sure about the binning, but for zoom it's OK to use all the "views" you mention, just double check that when you think you've finished framing it's set to On (Fit).  This should show the whole frame on screen.

image.png.77d7093cb820c3aa60eedeb8870f6c66.png

At any time, you can double click on your image to switch between On (1:1) and On (Fit).  Wherever you double click going from fit to 1:1 will zoom into that particular area.

Sorry, forgot to ask one last important question. 
 

What advantage did the reducer do to my imaging?

I understand that it shortens focal length and makes the scope faster, but in practical use, what difference does it to to my workload and sequences?

should I have taken LESS than 100 subs, or subs shorter than 120 seconds now that I’m imaging at f/6.375 rather than f/7.5?

i don’t seem to understand this yet?

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18 minutes ago, oymd said:

What advantage did the reducer do to my imaging?

It's the flattener part that will make the most difference I think if you're using a DSLR - should be nice round stars to the edge of the field.  The reducer part helps if you're imaging a larger target as you'll be able to fit more into the frame.

18 minutes ago, oymd said:

I understand that it shortens focal length and makes the scope faster, but in practical use, what difference does it to to my workload and sequences?

should I have taken LESS than 100 subs, or subs shorter than 120 seconds now that I’m imaging at f/6.375 rather than f/7.5?

Technically, no I don't believe so and I'm sure someone more experienced will be along to explain why.... but I think it's not making it faster per se, just capturing more photons because the field of view is larger.  There won't be any additional photons for your target (as it'll be smaller).  Search "f-ratio myth" here😅  I hope I've got that right 🤔

Edited by geeklee
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3 minutes ago, geeklee said:

It's the flattener part that will make the most difference I think if you're using a DSLR - should be nice round stars to the edge of the field.  The reducer part helps if you're imaging a larger target as you'll be able to fit more into the frame.

Technically, no I don't believe so and I'm sure someone more experienced will be along to explain why.... but I think it's not making it faster per se, just capturing more photons because the field of view is larger.  There won't be any additional photons for your target.  Search "f-ratio myth" here😅  I hope I've got that right 🤔

so having a faster f ratio just gives me a wider field of view, but no increase in light gathering power, so technically it will help me fit a bigger target in my frame, like M31, but with no increase in the targets detail or brightness? Is that right?

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6 minutes ago, oymd said:

so having a faster f ratio just gives me a wider field of view, but no increase in light gathering power, so technically it will help me fit a bigger target in my frame, like M31, but with no increase in the targets detail or brightness? Is that right?

I think I've confused myself now and wish I hadn't tried to comment on this particular aspect 😐  Sorry @oymd  hopefully someone with more experience with this question will chip in shortly (and likely correct me)!

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28 minutes ago, oymd said:

What advantage

Hi. It helped in making the stars less distorted. It gave you a wider field of view which is not really what you want for this target. It didn't make the telescope any faster though; to do that, you'd need to collect more light using a bigger telescope, so don't adjust the number of frames because of this. In fact keep taking frames until you just get fed up!

Cheers and HTH.

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2 hours ago, oymd said:

But aren’t the flats unrelated to the reducer change?

do you mean that since I’ve taken new images with a reducer, I need to redo flats with the reducer in place?

oh, yes of course. I’m an idiot....

No one is an idiot, except me sometimes.

Flats record any blemishes/defects in the optical train.  Even if you rotate your camera you likely would need to redo your flats.  In your case you DEFINITELY need to do new flats with the reducer in place.

Flats should be taken with the camera and reducer and telescope, spacers, etc, in exactly the same orientation and focus position as for your lights.  So maybe straight after an imaging session, or if you can lift the kit indoors without dismantling, and take the flats the next day.

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1 hour ago, tooth_dr said:

No one is an idiot, except me sometimes.

Flats record any blemishes/defects in the optical train.  Even if you rotate your camera you likely would need to redo your flats.  In your case you DEFINITELY need to do new flats with the reducer in place.

Flats should be taken with the camera and reducer and telescope, spacers, etc, in exactly the same orientation and focus position as for your lights.  So maybe straight after an imaging session, or if you can lift the kit indoors without dismantling, and take the flats the next day.

Yes, makes sense. But how could you do flats at the end of the session? Its pitch dark?

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6 minutes ago, Endolf said:

I use ELP from ebay, 250mm square.

 

1 minute ago, MarkAR said:

Light box. Flat Field Generator.

Would this work?

https://www.ebay.co.uk/itm/EL-Panel-White-10x10cm/221583107656?hash=item339761e648:g:~vEAAOSwjVVVnUI~

Would be great if you can point me in the direction of one that I can buy, that is easily powered? The one I found on ebay is just 10cmx10cm, and has a weird connector?

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Apologies if someone has already said it and I missed it, but I think for this target I wouldn't bother with the reducer and just crop off the edges of the image where the stars aren't that good during processing.  Even at the 80ED's native focal length the image will not be very big (only about 2mm x 1mm on the sensor).

James

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